1996 Telecommunications Act
Legislation designed to spur competition among wireless and wireline carriers. Signed into law by President Clinton in February 1996.

2G
Abbreviation for second generation. An improvement over the original design.

3G
Abbreviation for third generation. The next generation of wireless technology beyond personal communications services. The new standard promises to offer increased capacity and high-speed data applications up to 2 megabits.

802.11
The Institute of Electrical and Electronics Engineers standard for wireless local area network interoperability.

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Backhaul
A term used to define the communications link, typically microwave or fiber optical, between a base station and a communications switch or communications network.

Band
The range of frequencies in the same spectrum.

Bandpass limiter
A device that imposes hard limiting on a signal and contains a filter that suppresses the unwanted products of the limiting process.

Bandpass filter
A passive electronic circuit that allows a narrow range of frequencies to pass through the device while blocking or attenuating higher and lower frequencies. Crystals are used for narrow bandpass filters.

Bandwidth
The total range of frequencies required to transmit a radio signal without undue distortion. The required bandwidth of a radio signal is determined by the amount of information in the signal being sent.

Bar (Quartz)
Term used to refer to a quartz stone that has been machined on at least two sides.

Barkhausen criteria
States that for oscillation to occur the product of the gains around a loop must be equal to or greater than unity and that the sum of the phase shifts around the loop must be a multiple of 360°.

Base
The lower portion of a crystal holder. The base incorporates a resonator mounting structure and leads or pins to connect the device to an external circuit. See holder.

Base plating
The process of plating electrodes on to a crystal wafer.

Base station
Fixed radio station used by RCCs (radio common carrier) to send, receive and transport signals. See land mobile.

Base station controller (BSC)
The BSC is a device charged with managing radio frequency resources and radio frequency transmission for a group of basic trading areas (BTSs).

Base station subsystem (BSS)
A device charged with managing radio frequency resources and radio frequency transmission for a group of basic trading areas (BTAs).

Base transceiver station (BTS)
A device utilized to transmit radio frequency over the air interface.

Baseband signaling
Transmission of a digital or analog signal at its original frequencies. The signal is in its original form, not changed by modulation.

Baseband
The original band of frequencies produced by a transducer, such as a microphone, telegraph key, or other signal-initiating device, prior to initial modulation.

Bent pipe technology
Satellite technology to transmit calls from one point on Earth to a satellite and back down to another point.

BER
Abbreviation for bit error rate. The number of erroneous bits divided by the total number of bits transmitted, received, or processed over some stipulated period.
Note 1: Examples of bit error ratio are (a) transmission BER, i.e., the number of erroneous bits received divided by the total number of bits transmitted; and (b) information BER, i.e., the number of erroneous decoded (corrected) bits divided by the total number of decoded (corrected) bits.
Note 2: The BER is usually expressed as a coefficient and a power of 10; for example, 2.5 erroneous bits out of 100,000 bits transmitted would be 2.5 out of 105 or 2.5 10-5.

Bevel
A modification to one or both of the major faces of a resonator plate in which the face is altered to have a partially spherical configuration. See contour.

Bi-directional antenna
Antenna that radiates most of its power in two directions.

Bird
A colloquial expression used to refer to a communications satellite.

Blank
A quartz resonator plate. Also known as a wafer, a plate, or a resonator. A round or rectangular quartz crystal that has been lapped to produce very parallel major surfaces and has minor surfaces machined to the final dimensions required to build the desired resonator. A machined disk of single crystal quartz.

Booster
A television or FM broadcast station, operating at relatively low power that receives a distant input signal, amplifies it, and retransmits it on the same channel.

BPSK
Abbreviation for binary phase shift keying.

Broadband
A general term used to describe wide bandwidth equipment or systems which can deliver multiple channels and services like voice, data, video; i.e., a circuit that operates at a frequency of 20KHz or greater. Also called wideband.

Broadcast
Delivery of a transmission to two or more stations at the same time, such as over a bus type local network or by satellite.

BT cut
The commercial designation for a specifically oriented resonator plate, having well known and repeatable characteristics. See AT cut.

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C Band
Certain high-frequency radio frequency bands between 3,900 and 6,545 MHz used by communications satellites in the fixed satellite service.

C.I.
The abbreviation for crystal impedance, sometimes used in place of the word resistance.

C.I.M.
Abbreviation for crystal impedance meter. See test set.

C0
Abbreviation for shunt capacitance.

C1
The abbreviation for motional capacitance. Motional capacitance is also often abbreviated as Cm.

Calibrated
The process of plating a crystal to the finished frequency.

Calibration
The setting tolerance is the maximum allowable deviation from the nominal frequency at 25°C. It is normally specified in parts per million (ppm).

Calibration Accuracy
See frequency tolerance.

Can
The upper portion, or cover, of a crystal holder. See cover and holder.

Capacitance ratio
In applications (i.e. VCXO) where variations in the crystal parallel resonant frequency are desired, the capacitive ratio (r) may be specified. This ratio is an indicator of the change in a parallel load resonant frequency as a direct result of a given change in crystal load capacitance. Because the value of this ratio has physical limitations when it is realized in a quartz crystal design, please consult the factory for product specifications. r = C0/C1

Capacitance
The property exhibited by two conductors separated by a dielectric whereby an electric charge becomes stored between the conductors. Capacitance is measured in "farads" and is identified by the letter "C."

Capacitor
A passive electronic circuit component consisting, in its simplest form, of two metal electrodes separated by a dielectric.

Capacity
The average amount of traffic that a circuit or circuit group can handle.

Carrier frequency
The nominal frequency of a carrier wave.

CCRR
Abbreviation for co-channel rejection ratio.

CDMA
Abbreviation for code-division multiple access. A coding scheme, used as a modulation technique, in which multiple channels are independently coded for transmission over a single wideband channel.
Note 1: In some communication systems, CDMA is used as an access method that permits carriers from different stations to use the same transmission equipment by using a wider bandwidth than the individual carriers. On reception, each carrier can be distinguished from the others by means of a specific modulation code, thereby allowing for the reception of signals that were originally overlapping in frequency and time. Thus, several transmissions can occur simultaneously within the same bandwidth, with the mutual interference reduced by the degree of orthogonality of the unique codes used in each transmission.
Note 2: CDMA permits a more uniform distribution of energy in the emitted bandwidth.

CDPD
Abbreviation for cellular digital packet data. CDPD is a specification for supporting wireless access to the Internet and other public packet-switched networks.

Cellemetry
Brand name for BellSouth Cellular Corp.'s telemetry service, which uses the cellular network to carry data messaging used for remote services such as utility meter reading, vending machine status and vehicle or trailer tracking.

Center Frequency or Nominal Frequency
The midpoint in the passband. The specified reference frequency of the crystal and is typically specified in megahertz (MHz) or kilohertz (kHz).

Central Processing Unit System (CPU)
The portion of a computer that includes circuits controlling the interpretation and execution of instructions and also the portion that executes programmed instructions, performs arithmetic and logical operations on data, and controls input / output functions.

Channel
A single path, either RF or voice, for transmitting electrical signals between a sending point and receiving point. Channels are often measured in terms of the amount of spectrum they occupy (bandwidth) measured in Hertz.

Channel elements
The frequency determining device in communications equipment. (i.e. oscillator, TCXO, and/or VCXO).

Channel spacing
The difference in frequency between successive radio or television channels.

Chemical etching process
Cleaning quartz resonators by removing some of the surface.

Circuit
Physical connection of channels, conductors and equipment required to provide a complete communications pathway.

Clear channel
A clear channel protects stations designated as Class A stations from objectionable interference within their primary and secondary
service areas. To provide this wide service area, Class A stations operate within a power range of 10 to 50 kilowatts.

Clock
A device providing signals used in a transmission system to control the timing of certain functions such as the duration of signal elements or the sampling rate. A device that generates periodic, accurately spaced signals used for such purposes as timing, regulation of the operations of a processor, or generation of interrupts.

Clock rate
The rate at which a clock issues timing pulses.

Cm
Abbreviation for motional capacitance.

Cold Weld
Welding in which a molecular bond is obtained by a cold flow of metal under extremely high pressures, without heat; widely used for sealing transistors and quartz crystal holders.

Co-location
Placement of multiple antennas at a common physical site to reduce environmental impact and real estate costs and speed zoning approvals and network deployment. Co-location can be affected by competitive and interference factors.

Colpitts oscillator
An oscillator in which a parallel-tuned tank circuit has two voltage-dividing capacitors in series, with their common connection going to the cathode in the electron-tube version and the emitter circuit in the transistor version.

Common-Mode Rejection Ratio (CMRR)
The ratio of the common-mode interference voltage at the input of a circuit, to the corresponding interference voltage at the output.

Communications satellite
A satellite that is used to relay telecommunications information.

Complementary Metal-Oxide Semiconductor (CMOS)
The semiconductor technology used in the transistors that are manufactured into most of today's computer microchips.

COMSAT
Abbreviation for Communications Satellite Corporation. Corporations, chartered by Congress, as an exclusive provider of international telecommunications satellite channels to the US COMSAT also represents the US in INTELSAT.

Conductor
A material that easily conducts an electric current because some electrons in the material are free to move.

Contour
A modification to one or both of the major faces of a resonator plate in which the face is altered to have a completely spherical configuration. See bevel.

Coupled mode
An unwanted mode that becomes energized at the same frequency as the desired mode, thereby draining energy from the desired mode.

Cover
The upper portion of a crystal holder. See holder.

Covered SMR
A subset of specialized mobile radio operators subject to a particular set of regulations.

Crystal
A generic term used in place of the more complete expression piezoelectric quartz crystal unit. A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts. Usually a mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces.

Crystal blanks
Round or square wafers of quartz crystals.

Crystal calibration
See calibrated.

Crystal cut
The orientation of the crystal element with respect to crystallographic axis of the crystal.

Crystal element
Piezoelectric material cut to a given geometric shape, size and orientation with respect to the crystallographic axis of the crystal.

Crystal enclosure
The enclosure protecting the crystal vibrator(s) and mounting system.

Crystal Equivalent Circuit
A crystal device consists of a quartz resonator with metal plating. This plating, as shown in Figure 3, is located on both sides of the crystal and is connected to insulated leads on the crystal package. The device exhibits a piezoelectric response between the two crystal electrodes as expressed in the equivalent circuit shown in Figure 4.

Figure 3

Figure 4

Crystal filter
An electric wave filter employing pies-electric crystals for its reactive elements. In general, filters can be provided in a number of differing topologies, including bandpass, band reject or notch, low pass, and high pass.

Crystal oscillator
An oscillator in which the frequency is controlled by a piezoelectric crystal. A crystal oscillator may require controlled temperature because its operating frequency is a function of temperature. Types of crystal oscillators include voltage-controlled crystal oscillators (VCXO), temperature-compensated crystal oscillators (TCXO), oven-controlled crystal oscillators (OCXO), temperature-compensated-voltage controlled crystal oscillators (TCVCXO), oven-controlled voltage-controlled crystal oscillators (OCVCXO), microcomputer-compensated crystal oscillators (MCXO), and rubidium crystal oscillators (RbXO).

Crystal Parameter Equations

Equation 1. Series Frequency (Fs)

Equation 2. Load Frequency (FL)

Equation 3. R1 Ohms (@Series Resonance)

Equation 4. Pullability crystal Unit Equivalent Circuit
The electrical circuit which has the same impedance as the unit in the immediate neighborhood of resonance.



Current
The net transfer of electric charge per unit of time.

CW
Abbreviation for continuous wave.

Cycle
One complete repetition of an event.

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dB Bandwidth
The specified reference level for the difference between the frequency limits of a band containing the useful frequency components of a signal.

dB
Abbreviation for decibel. See decibel.

dBc
Decibels with respect to or relative to the carrier power.

dBm
Decibels with respect to 1 mW. dBm is used in communication work as a measure of absolute power values. Zero dBm equals one milliwatt.

dBW
Decibels with respect to 1 W. Watts of power expressed in decibels.

DC
Abbreviation for direct current.

DCS
Abbreviation for distributed communications system or digital cellular system.

DDS
Abbreviation for direct digital synthesis.

Decibel
Abbreviation = dB. A unit for describing the ratio of two powers or intensities, or the ratio of a power to a reference power.

DECT
Abbreviation for Digital European cordless telephone.

Desired frequency
See nominal frequency.

Deviation
The amount by which a quantity differs from its nominal value. The amount by which a frequency differs from the nominal or specified frequency.

Dew Point
The temperature at which a condensable component of a gas starts to condense into a liquid.

Dice (Quartz)
Pieces of quartz produced by sectioning quartz wafers into rectangular shapes. Dice are then further machined to produce crystal blanks.

Dielectric
Material that does not conduct electricity readily, i.e., an insulator. A good dielectric should also have other properties: It must resist breakdown under high voltages; it should not itself draw appreciable power from the circuit; it must have reasonable physical stability; and none of its characteristics should vary much over a fairly wide temperature range. One important application of dielectrics is as the material separating the plates of a capacitor.

Digital signal processor (DSP)
A specialized, programmable computer processing unit that is able to perform high-speed mathematical processing.

DIL
Abbreviation for dual in-line.

DIP
Abbreviation for dual in-line package.

Direct broadcast satellite (DBS)
A high-powered satellite that transmits or retransmits signals which are intended for direct reception by the public. The signal is transmitted to a small earth station or dish (usually 18-inches) mounted on homes or other buildings.

Direct piezoelectric effect
The generation of electricity (or electric polarity) in crystals subjected to mechanical stress.

Directional antenna
An antenna in which the radiation pattern is not omnidirectional, i.e., a nonisotropic antenna.

Disciplined oscillator (DO)
An oscillator whose output frequency is continuously steered (often through the use of a phase locked loop) to agree with an external reference. For example, a GPS disciplined oscillator (GPSDO) usually consists of a quartz or rubidium oscillator whose output frequency is continuously steered to agree with signals broadcast by the GPS satellites.

Dish
A circular antenna used to pick up transmissions broadcast from a satellite. See satellite dish.

DOD master clock
The master clock to which time and frequency measurements for the U.S. Department of Defense are referenced, i.e., are traceable. The U.S. Naval Observatory master clock is designated as the DOD Master Clock.

Double rotated quartz cut
SC cut, IT cut, and FC cuts are examples of double rotated quartz cuts. Double rotated quartz cut refers to the two rotations from two reference planes needed for these cuts.

Downlink
A link from a satellite to an earth station.

Drive level
The amount of power dissipation in the crystal, expressed in microwatts or milliwatts. Maximum power is the most power the device can dissipate while still maintaining operation with all electrical parameters guaranteed. Drive level should be maintained at the minimum levels necessary to initiate proper start-up and assure steady state oscillation. Excessive drive level can cause poor aging characteristics and crystal damage.

Dry Nitrogen
Moisture free nitrogen.

DTCXO
Abbreviation for Digitally Temperature Compensated crystal Oscillator.

DUT
Abbreviation for device under test.

Duty cycle
The measure of output waveform uniformity. This term, also referred to as symmetry, is a measurement of the time that the output waveform is in a logic high state, expressed as a percentage (%). This parameter is measured at a specified voltage threshold or at a percentage of the output waveform amplitude.

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Earth station
A station located either on the Earth's surface or within the major portion of the Earth's atmosphere and intended for communication:
* with one or more space stations; or
* with one or more stations of the same kind by means of one or more reflecting satellites or other objects in space.

ECL
Abbreviation for emitter-coupled logic.

EEPROM
Abbreviation for electrically erasable programmable read-only memory.

EIA
Abbreviation for Electronic Industries Association.

Electrode capacitance
This capacitor is not a result of the acoustic vibration of the crystal blank but rather a simple capacitor formed by a dielectric with electrodes on either side.

Electrodes
Terminal through which electric current passes between metallic and nonmetallic parts of an electric circuit. In most familiar circuits current is carried by metallic conductors, but in some circuits the current passes for some distance through a nonmetallic conductor.

Electromagnetic compatibility (EMC)
The condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the same environment.

Electromagnetic interference (EMI)
An engineering term used to designate interference in a piece of electronic equipment caused by another piece of electronic or other equipment. EMI sometimes refers to interference caused by nuclear explosion.

Electromagnetic spectrum
The range of frequencies of electromagnetic radiation from zero to infinity. Note: The electromagnetic spectrum was, by custom and practice, formerly divided into 26 alphabetically designated bands. This usage still prevails to some degree. However, the ITU formally recognizes 12 bands, from 30 Hz to 3000 GHz. New bands, from 3 THz to 3000 THz, are under active consideration for recognition.

Emission
In this context, radiation produced by a radio transmitting station.

Emitter
A transistor region from which charge carriers that are minority carriers in the base are injected into the base, thus controlling the current flowing through the collector; corresponds to the cathode of an electron tube.

Enable/Disable
The enable/disable pin is similar to an on/off switch. A low or logic 0 on the enable/disable causes the unit not to oscillate. A
"high" or logic 1 on the enable/disable pin allows the unit to work as normal (enabled) producing the specified output.

Energy trapping
A term applied to the application of the cutoff phenomenon in wave guides to suppress undesired modes of vibration in a quartz crystal unit.

Equivalent circuit
The equivalent circuit shown below depicts electrical activity of a quartz crystal unit operating at its natural resonant frequency. The CO, or shunt capacitance, represents the capacitance of the crystal electrodes plus the capacitance of the holder and leads. R1, C1, and L1 compose the "motional arm" of the crystal, and are referred to as the motional parameters. The motional inductance (L1) represents the vibrating mass of the crystal unit. The motional capacitance (C1) represents the elasticity of the quartz, and the resistance (R1), represents bulk losses occurring within the quartz.

Equivalent series resistance (ESR)
The resistive element, measured in ohms, of a crystal device. The ESR measurement is made only at the series resonant frequency (FS), not at some predetermined parallel resonant frequency (FL). The motional inductance (L1) and motional capacitance (C1) are of equal ohmic value but are exactly opposite in phase. The net result is that they cancel one another and only a resistance remains in the series leg of the above equivalent circuit. crystal resistance measured at some parallel load resonant frequency is often called the "effective" resistance. (2) A term used to define and quantify the resistive element of a crystal.

ESD
Abbreviation for electrostatic discharge.

Etch
A process used in the manufacture of some types of crystal units. The etch process results in an improved surface condition and an increase in the frequency of a blank. The word "etch" is also used to describe the material used in the etch process, as well as the process itself.

ETSI
Abbreviation for European Telecommunications Standards Institute. A European counterpart to ANSI. It facilitates integration of telecommunications standards into all of Europe.

Extremely high frequency (EHF)
Frequencies from 30 GHz to 300 GHz.

Extremely low frequency (ELF)
Frequencies from 30 Hz to 300 Hz.

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Face
One of the natural surfaces that develop on a crystal during the growth process. Often called a "natural face".

Fall time
Fall time is defined as the transition time from an output logic high to an output logic low and is measured in nanoseconds (nSec). This transition time is measured at specified voltage thresholds or at specified percentages of the output waveform amplitude. See rise time.

Family radio service (FRS)
A very low power, short range two-way radio service in the 460 MHz band.

Fanout
Number of IC gates which can be connected to the output of a crystal oscillator.

Farad
Unit of electrical capacitance, equivalent to 1 coulomb of stored charge per volt of applied potential difference. Named for Michael
Faraday.

FC cut
This cut has an improved temperature and frequency characteristic for ovenized applications (OCXO). The frequency vs. temperature curve is a sine with the inflection temperature at ~ +52"C. This crystal operates in the thickness shear mode. Preferred for ovenized oscillators (OCXO) such as space systems, and Global Positioning Satellite Systems. See AT cut, BT cut, IT cut and SC cut.

FCXO
An abbreviation for a Frequency Converting crystal Oscillator. An FCXO consists of a low phase noise VCXO combined with a complete PLL, which simplifies the synchronization of an output frequency to a stable reference frequency. With its low phase noise, this compact surface mount device is applicable to a wide variety of synchronization schemes. An FCXO also offers a higher degree of component integration than older technologies.

FDD
Abbreviation for frequency division duplex.

Federal Communications Commission (FCC)
An independent federal governmental agency, authorized by the Communications Act of 1934, with authority delegated by Congress to manage commercial and private spectrum.

FER
Abbreviation for frame error rate.

Field-effect transistor (FET)
A field-effect transistor (FET) is a type of transistor commonly used for weak-signal amplification (for example, for amplifying wireless signals). The device can amplify analog or digital signals. It can also switch DC or function as an oscillator.

Filter
Any transmission network used in electrical systems for the selective enhancement of a given class of input signals.

FIR
Abbreviation for finite impulse response.

First in, first out (FIFO)
A queuing discipline in which entities in a queue leave the queue in the same order in which they arrive.

Footprint
In satellite communications, that portion of the Earth's surface over which a satellite antenna delivers a specified amount of signal power under specified conditions.

Forward Error Corrections (FEC)
A system of error control for data transmission wherein the receiving device has the capability to detect and correct any character or code block that contains fewer than a predetermined number of symbols in error.

Frequency
The range of electromagnetic waves with a frequency or wavelength suitable for utilization in radio communication. The periodic repetition of an event within a unit of time. In an electrical circuit, the number of waves that pass a given point in one second. The number of times a resonator plate oscillates or vibrates in one second. The nominal or desired frequency specified by a customer.

Frequency accuracy
The degree of conformity of a measured or calculated frequency to its definition. Since accuracy is related to the offset from an ideal value, frequency accuracy is usually stated in terms of the frequency offset. Frequency Calibration Tolerance @ 25°C
Frequency Calibration Tolerance is the minimum and the maximum frequency deviation allowed from the Target Frequency @25°C. This deviation is usually specified in ±ppm (parts per million).

Frequency deviation
The amount by which a frequency differs from a prescribed value, such as the amount an oscillator frequency drifts from its nominal frequency. In frequency modulation, the absolute difference between (a) the maximum permissible instantaneous frequency of the modulated wave or the minimum permissible instantaneous frequency of the modulated wave and (b) the carrier frequency.

Frequency drifting
An undesired progressive change in frequency with time. Causes of frequency drift include component aging and environmental changes.

Frequency fluctuation
A short-term variation, with respect to time, of the frequency of an oscillator.

Frequency hopping, spread spectrum (FHSS)
Frequency hopping is one of two basic modulation techniques used in spread spectrum signal transmission. It is the repeated switching of frequencies during radio transmission, often to minimize the effectiveness of "electronic warfare" - that is, the unauthorized interception or jamming of telecommunications. It also is known as frequency- hopping code division multiple access.

Frequency instability
See frequency stability.

Frequency modulation or frequency modulated (FM)
In frequency modulation, the frequency of the carrier wave is varied in such a way that the change in frequency at any instant is proportional to another signal that varies with time. See phase modulation.

Frequency offset
The difference between a measured frequency and an ideal frequency with zero uncertainty. This ideal frequency is called the nominal frequency.

Frequency range
A continuous range or spectrum of frequencies that extends from one limiting frequency to another. The frequency range for given equipment specifies the frequencies at which the equipment is operable. For example, filters pass or stop certain bands of frequencies. The frequency range for propagation indicates the frequencies at which electromagnetic wave propagation in certain modes or paths is possible over given distances.

Frequency shift
A change in the frequency of a radio transmitter or oscillator.

Frequency-shift keying (FSK)
Frequency modulation in which the modulating signal shifts the output frequency between predetermined values.

Frequency stability
The amount of frequency deviation from the ambient temperature frequency over the operating temperature range. This deviation is associated with a set of operating conditions including operating temperature range, load capacitance, and drive level. This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm). The frequency stability is primarily determined by the type of quartz cut and angle of the quartz cut. Some of the secondary factors influencing frequency stability include mode of operation, drive level, load capacitance, and mechanical design. The frequency stability is the allowable deviation, in parts per million (ppm), over a specified temperature range. The deviation is referenced to the measured frequency at +25°C.

Frequency standard
A stable oscillator used for frequency calibration or reference.

Frequency tolerance
The amount of frequency deviation from a specified center frequency at ambient temperature (referenced at 25°C). This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm). This deviation is associated with a set of operating conditions including load capacitance and drive level.

Frequency tolerance/stability
An "inclusive" specification is defined as the amount of frequency deviation from the center frequency associated with a set of operating conditions including operating temperature range, supply voltage, and output load. This parameter is specified with a maximum and minimum frequency deviation, expressed in percent (%) or parts per million (ppm).

Frequency translation
The transfer of signals occupying a specified frequency band, such as a channel or group of channels, from one portion of the frequency spectrum to another, in such a way that the arithmetic frequency difference of signals within the band is unaltered.

Fundamental frequency
The lowest frequency at which a resonator plate will oscillate. This frequency is determined by the physical dimensions of the plate. Also known as the first harmonic. See overtones.

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GaAs
Abbreviation for gallium arsenide.

Gain
A measure of the ability of an antenna to receive radio frequency signals, which is related to physical size. The larger the antenna, the higher the gain and the higher the received signal level, in general. An increase in signal power denoted in dbs.

GaN
Abbreviation for gallium nitride.

Gaussian function
A mathematical function used to design a filter which passes a step function with zero overshoot with maximum rise time.

Geometry
The shape of the resonator plate used in a crystal unit. There are three (3) geometrical forms available: flat, contoured, and beveled.

Geosynchronous satellite
A satellite that orbits the Earth during the same period of time in which the Earth rotates, maintaining a fixed orbit, about 24,000 miles above the Earth.

GFSK
Abbreviation for Gaussian filtered frequency shift keying.

Gigahertz (GHz)
A unit of frequency equal to one billion cycles (or Hertz) per second.

Global Navigation System (GLONASS)
A Russian satellite location technology similar to GPS, global positioning system.

Global positioning system (GPS)
A series of 24 geosynchronous satellites that continuously transmit their position. Used in personal tracking, navigation and automatic vehicle location technologies. See GLONASS.

Global system for mobile communication (GSM)
A public, all-digital cellular network that is standardized worldwide and that uses TDMA techniques for multiplexing at approximately 900 MHz, compressed voice at about 13 kb/s, 16 kb/s circuit-switching technology, and error-correcting algorithms.

GMSK
Abbreviation for Gaussian minimum shift keying.

GPIB
Abbreviation for general-purpose interface bus.

GPRS
Abbreviation for general packet radio service.

Grounded base butler
Oscillator commonly used in the range from 20 to 100 MHz. The circuit is capable of delivering high output power, has medium frequency stability. These are basically amplifiers with a tapped capacitor resonant circuit in the collector.

Group delay distortion
The difference between maximum and minimum group delay in the passband.

Group delay
The time taken for a narrow band signal to pass from the input to the output of a device.

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Harmonic level
Signal strength of the multiples of a fundamental frequency.

HBT
Abbreviation for heterojunction bipolar transistor.

Height Above Average Terrain (HAAT)
Measurement of tower height above surrounding average terrain.

HEMT
Abbreviation for high electron mobility transistor.

Henry
The basic unit of inductance, identified by the letter H. One henry of inductance is produced in a closed circuit by a current changing uniformly at the rate of one Ampere per second.

Hermetic seal
An airtight seal.

Hertz
The basic unit of measurement of frequency, "Hertz" replaces the term "cycle per second". Used to denote one complete occurrence of an event in one second. Hertz is commonly abbreviated as Hz.

High frequency (HF)
Frequencies from 3 MHz to 30 MHz commonly known as shortwave. The carrier frequencies of 5, 10, and 15 MHz within this spectrum are internationally allocated for time and frequency broadcasts, and are used by a number of stations, including NIST radio stations WWV and WWVH.

High-pass filter
A filter that passes frequencies above a given frequency and attenuates all others.

Holder
The complete housing for a quartz resonator plate. The holder includes the base and cover. See can and cover.

Holder capacitance
The sum of the stray capacity contributed by the crystal connected between the two leads of the resonator.

Holder size
The measurement of the base and cover combined.

Home satellite dish (HSD)
A home receiver that permits the consumer to receive existing satellite transmissions.

High-speed circuit-switched data (HSCSD)
High-Speed Circuit-Switched Data is circuit-switched wireless data transmission for mobile users at data rates up to 38.4 Kbps, four times faster than the standard data rates of the Global System for Mobile (GSM) communication standard in 1999. HSCSD is comparable to the speed of many computer modems that communicate with today's fixed telephone networks.

Hydrothermal
A method of growing synthetic quartz using a pressure vessel, calcium chloride or sodium chloride, and a quantity of natural quartz material.

Hypertext transfer protocol (HTTP)
In the World Wide Web, a protocol that facilitates the transfer of hypertext-based files between local and remote systems.

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I and Q
Abbreviation for in-phase and quadrature.

Impedance
The total opposition presented by a circuit or device to the flow of alternating current. Impedance is measured in ohms and is represented by the letter Z.

Inductance
In a device, conductor, or circuit, the inertial property that opposes the flow of current when a voltage is applied. Inductance is identified by the letter "L" and is measured in henries.

Inductor
An electronic component used to introduce inductance into a circuit.

Industrial Telecommunications Association ( ITA)
A Washington, DC trade group serving private wireless licensees such as airlines and oil companies.

Industrial, scientific, and medical (ISM) applications (of radio frequency energy)
Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.

Inflection point
An AT-cut crystal has a temperature vs. frequency characteristic that can be represented by a third order polynomial. This curve has a point where the slope is zero and the slope is positive on one side and negative on the other side. This point is defined as the inflection point.

Infrared (IR)
Infrared radiation (IR) or the term infrared alone refers to energy in the region of the electromagnetic radiation spectrum at wavelengths longer than those of visible light, but shorter than those of radio waves.The region of the electromagnetic spectrum bounded by the long-wavelength extreme of the visible spectrum (approximately 0.7 µm) and the shortest microwaves (approximately 0.1 mm).

InGaP
Abbreviation for indium gallium phosphide.

InP
Abbreviation for indium phosphide.

Input current
The amount of current consumption by an oscillator from the power supply, typically specified in milliamps (mA).

Input/output (I/O) device
A device that introduces data into or extracts data from a system.

Insertion loss
The loss in load power due to the insertion of a component or device at some point in a transmission system. (Generally expressed as the ratio in decibels of power received at the load before insertion of the apparatus, to the power received at the load after insertion.)

Insulator
Any of several materials that do not easily permit the passage of electricity.

Integrated circuit (IC)
An electronic circuit that consists of many individual circuit elements, such as transistors, diodes, resistors, capacitors, inductors, and other active and passive semiconductor devices, formed on a single chip of semiconducting material and mounted on a single piece of substrate material. An IC is also referred to as a chip and a microcircuit.

Intermodulation (IM)
The production, in a nonlinear element of a system, of frequencies corresponding to the sum and difference frequencies of the fundamentals and harmonics that are transmitted through the element.

Intermodulation distortion (IMD)
Nonlinear distortion characterized by the appearance, in the output of a device, of frequencies that are linear combinations of the fundamental frequencies and all harmonics present in the input signals.

International Telecommunications Satellite Consortium or International Telecommunications Satellite Organization (INTELSAT)
Organization formed in 1964 with the goal of creating a worldwide satellite system. See COMSAT.

Intermediate frequency (IF)
A frequency to which a carrier frequency is shifted as an intermediate step in transmission or reception.

International shortwave broadcast station
A station that sends programs overseas either for direct reception by listeners abroad or for intermediate reception by overseas relay stations that rebroadcast the programs on shortwave or medium wave stations to nearby audiences.

International Mobile Station Equipment Identity (IMEI)
An equipment identification number, similar to a serial number, used to identify a mobile station.

International Organization for Standardization (ISO)
An international organization devoted to determining standards for international and national data communications and other technical fields.

International Telecommunication Union (ITU)
The international organization that coordinates and publishes telecommunications standards and regulatory and standards information.

International Telecommunication Union-Telecommunication Standardization Sector
The Telecommunication Standardization Sector of the International Telecommunication Union (ITU).

Internet protocol (IP)
A DOD standard protocol designed for use in interconnected systems of packet-switched computer communication networks.

ISM
Abbreviation for industrial, scientific, and medical applications of radio frequency energy. Operation of equipment or appliances designed to generate and use locally radio-frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.

IT cut
This crystal cut has an improved temperature and frequency characteristic for ovenized applications (OCXO). The frequency vs. temperature curve is a sine with the inflection temperature at ~ +78°C. This crystal operates in the thickness shear mode. It is preferred for ovenized oscillators (OCXO) such as space systems, and Global Positioning Satellite Systems. See AT cut, BT cut, FC cut and SC cut.

Itty bitty package (IBP)
Refers to the round compression weld package used to enclose early strip resonators.

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Jitter
The modulation in phase with the frequency of the clock oscillator output

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k
See kilo.

Ka-band
Radio spectrum in the 18 GHz to 31 GHz range used by satellite communications systems.

Kilo
A prefix, abbreviated "k," used to denote units of thousands. One "Kilo" is one thousand. A frequency of one kilohertz is a frequency of one thousand hertz (cycles per second). A unit of frequency denoting one thousand (103) Hz.

Kilobyte (kB)
As a measure of computer memory or storage, a kilobyte (KB or Kbyte) is approximately a thousand bytes (actually, 2 to the 10th power, or decimal 1,024 bytes).

KiloHertz (kHz)
Used to describe the frequency of a crystal or oscillator in terms of thousands of Hertz (cycles per second). A frequency specified as "10.0 kHz" would be understood as being a frequency of 10,000 Hertz (cycles per second). A frequency specified as "10,000 kHz" would be understood as being a frequency of 10,000,000 Hertz (cycles per second).

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L1
Abbreviation for motional inductance.

Land Mobile Communications Council (LMCC)
A trade group of frequency coordinators and associations serving private users and commercial operators.

Land mobile radio
Land mobile radio refers to two-way communication between base stations and mobile, terrestrial based mobile radios.

Land mobile service
A mobile service between base stations and land mobile stations, or between land mobile stations.

Land mobile station
A mobile station in the land mobile service capable of surface movement within the geographical limits of a country or continent.

Lapping
Moving a quartz crystal slab over a flat plate on which a liquid abrasive has been poured, to obtain a flat polished surface or to reduce the thickness a carefully controlled amount.

L-band
A range of frequencies covering approximately 1-1.7 GHz.

LDMOS
Abbreviation for laterally diffused metal oxide silicon.

Leads
See pins.

Line of sight (LOS)
Of an electromagnetic wave, propagation in which the direct ray from the transmitter to the receiver is unobstructed, i.e., the transmission path is not established by or dependent upon reflection or diffraction.

Linearity
The relationship that exits between two quantities when a change in one of them produces a directly proportional change in the other. A trade group of frequency coordinators and associations serving private users and commercial operators.

LNA
Abbreviation for low-noise amplifier.

LO
Abbreviation for local oscillator.

Load
The reactance value presented to the crystal by the external oscillator circuit. The power consumed by a device or circuit in performing its function. A power-consuming device connected to a circuit.

Load capacitance
The value of capacitance used in conjunction with the crystal unit. Load capacitance is a parameter specified by the customer, typically expressed in pF (picoFarads).

Load drive capability
The maximum load the oscillator can drive specified in terms of the number of gates or the type of load circuit.

Load resonance
The condition existing when a crystal unit is operated in conjunction with load capacitance. See series resonance.

Load resonance resistance (RL)
The resistance of the crystal unit in series with a stated external capacitance at the load resonance frequency.

Local multipoint distribution service (LMDS)
A system for broadband microwave wireless transmission direct from a local antenna to homes and businesses within a line-of-sight radius, a solution to the so-called last-mile technology problem of economically bringing high-bandwidth services to users. LMDS is an alternative to installing optical fiber all the way to the user or to adapting cable TV for broadband Internet service.

Logic compatibility
In the past, CMOS, TTL, and ECL oscillators were only capable of driving output loads of the same logic family. With the introduction of HCMOS logic, dual compatible oscillators are manufactured that can drive two logic families. The dual compatible oscillator's output waveform voltages are derived from HCMOS logic. The logic output exceeds the minimum voltage level requirements of TTL, and with the higher output current capability of HCMOS, these dual compatible oscillators can drive both logic families.

Logic Levels
Defined as the Output Voltage Logic High or "Logic 1" and the Output Voltage Logic Low or "Logic 0" (See Image below).





Loop
A communications channel from a switching center or an individual message distribution point to the user terminal. Go-and-return conductors of an electric circuit; a closed circuit. A closed path under measurement in a resistance test. A type of antenna, in the form of a circle or rectangle, usually used in direction-finding equipment and in UHF reception.

Low frequency
The part of the radio spectrum ranging from 30 to 300 kHz. A number of standard time and frequency signals are broadcast in this region, including the 60 kHz signal from NIST Radio Station WWVB, and the 100 kHz LORAN-C signals.

Low phase noise crystals
Crystals designed to have a pure spectral signal for such critical applications as communications and radar. See precision crystals.

LPF
Abbreviation for low-pass filter.

Large scale integration(LSI)
LSI (large-scale integration) meaning microchips containing thousands of transistors.

LTCC
Abbreviation for low-temperature co-fired ceramic.

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Mask
In communications systems, to obscure, hide, or otherwise prevent information from being derived from a signal. Masking is usually the result of interaction with another signal, such as noise, static, jamming, or other forms of interference.

Master frequency generator
In frequency-division multiplexing (FDM), equipment used to provide system end-to-end carrier frequency synchronization and frequency accuracy of tones.

Maximum usable frequency (MUF)
In radio transmission using reflection from the regular ionized layers of the ionosphere, the upper frequency limit that can be used for transmission between two points at a specified time.

MCXO
Microcomputer compensated crystal oscillator often used in spread spectrum system clocks, MTI radars, wireless base stations, telecom timing modules, and precision test equipment.

MDS
Abbreviation for multipoint distribution systems.

Mechanical strip
See AT strip.

Medium frequency (MF)
Frequencies from 300 kHz to 3000 kHz.

Mega
A prefix, abbreviated "M", used to denote units of millions. One "Mega" is equal to one million. In our industry, one MegaHertz is a frequency of one million Hertz (cycles per second).

MegaHertz (MHz)
Used to describe the frequency of a crystal or oscillator in terms of millions of Hertz (cycles per second). A frequency specified as "10.0 MHz" would be understood as being a frequency of 10,000,000 Hertz (cycles per second).

Metal-oxide semiconductor field-effect transistor (MOSFET)
A special type of field-effect transistor (FET) that works by electronically varying the width of a channel along which charge carriers (electrons or holes) flow. The wider the channel, the better the device conducts.

Microbalance
An unsealed plated quartz crystal wafer used to measure very minute changes in its mass by monitoring its frequency.

Microprocessor crystal
Standard crystals for use in clock circuits of microprocessors.

Microwave
RF signals between 890 MHz and 20 GHz. Point-to-point microwave transmission is commonly used as a substitute for copper or fiber cable.

Microwave band
Those frequencies from about 1 GHz upward that use microwave frequencies for point-to-point and point-to-multipoint communications, including common carriers, cable TV operators, broadcasters and private operational fixed users.

Microwave radio
A radio frequency used extensively for long-distance telephone transmission. Digitally encoded messages are sent through microwave channels either between terrestrial antennae, via satellite, or through waveguides.

Military crystals
Quartz crystals that are designed to meet military specifications (Mil-Spec) and produced to Mil-Spec requirements (QPL).

Milli
A prefix, abbreviated "m", used to denote units of thousandths. One "milli" is equal to 1/1000th of a unit.

MMIC
Abbreviation for monolithic microwave integrated circuit.

Mobile earth station
An Earth station in the mobile-satellite service intended to be used while in motion or during halts at unspecified points.

Mobile service
A radiocommunication service between mobile and land stations, or between mobile stations.

Mobile station
A station in the mobile service intended to be used while in motion or during halts at unspecified points.

Mode of operation
The mode of operation of a quartz device is one of the factors that will determine the frequency of oscillation. For AT-cut quartz crystals, overtone modes are at odd frequency harmonics. A crystal may operate at its fundamental frequency of 10 MHz, or at odd harmonics of approximately 30MHz (Third Overtone), 50MHz (Fifth Overtone), and 70 MHz (Seventh Overtone).

Modulation
Impressment of information on a carrier signal by varying one or more of the signal's basic characteristics: frequency, amplitude and phase.

Monolithic crystal
A crystal with two or more electrodes where energy is coupled between the electrodes by way of the vibrating quartz structure.

Monolithic crystal filter (MCF)
Filter which is a crystal with two or more electrodes where energy is coupled between the electrodes by way of the vibrating quartz structure.

Motional capacitance
A parameter associated with a quartz crystal unit, used to illustrate the electronic equivalence of the mechanical elasticity of the unit. Motional capacitance may be abbreviated as "Cm" or "C1." The actual value of C1 has physical limitations when it is realized in a quartz crystal design. These constraints include the mode of operation, the quartz cut, the mechanical design, and the nominal frequency of the crystal.

Motional inductance
A parameter associated with a quartz crystal unit, used to illustrate the electronic equivalence of the mechanical mass of the unit. Motional inductance may be abbreviated as "Lm" or "L1."

Motional resistance
The energy lost within the vibrating area of the crystal resonator. Does not include any loss external to the vibrating crystal. It is represented in the electrical circuit as a resistor. See resistance.

MS/s
Abbreviation for million of samples per second.

Multichannel multipoint distribution service (MMDS)
A broadcasting and communications service that operates in the ultra-high-frequency (UHF) portion of the radio spectrum between 2.1 and 2.7 GHz. MMDS is also known as wireless cable.

Multi-element dipole antenna
An antenna consisting of an arrangement of multiple dipole antennas.

Multipoint distribution service (MDS)
Also known as "wireless" cable. This is a one-way, domestic public radio service broadcast on microwave frequencies from a fixed station that transmits (usually in an onmidirectional pattern) to multiple receiving facilities located at fixed points.

Multi-satellite link
A radio link between a transmitting Earth station and a receiving Earth station through two or more satellites, without any intermediate Earth station.

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n
The small letter "n" is used to designate the overtone number of a crystal unit.

Narrowband AMPS
Cellular standard that expands the network capacity by up to three times by decreasing the duplex RF channel size to 20 kHz (from 60 kHz).

Narrowband radio
Uses a voice channel with a nominal 3-kHz bandwidth.

Narrowband radio voice frequency (NBRVF)
In narrowband radio, the nominal 3-kHz bandwidth allocated for single channel radio that provides a transmission path for analog and quasi-analog signals.

National Telecommunications and Information Administration (NTIA)
The federal government's spectrum management.

Natural frequency
Of an antenna, the lowest frequency at which the antenna resonates without the addition of any inductance or capacitance.

Necessary bandwidth
For a given class of emission, the width of the frequency band which is just sufficient to ensure the transmission of information at the rate and with the quality required under specified conditions.

Nominal frequency
The specified "name plate frequency" of a crystal or oscillator.

NTC
Abbreviation for negative temperature coefficient.

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OCVCXO
Oven controlled/voltage controlled crystal oscillator often used in often used in navigation system clocks, frequency standards, MTI radars, wireless base stations, telecom timing modules, precision test equipment, phase lock loop (PLL) circuits in telecom timing recovery, wireless base station channel or timing reference and fiber optic timing reference.

OCXO
Oven-controlled crystal oscillator often used in navigation system clocks, frequency standards, MTI radars, wireless base stations, telecom timing modules and precision test equipment.

Ohms
A unit of electrical resistance, defined as the resistance in a circuit in which a potential difference of one volt creates a current of one ampere; hence, 1 ohm equals 1 volt/ampere.

Omni-directional antenna
Antenna that radiates equal power in all directions in a horizontal plane.

Operating temperature range
The maximum and minimum temperatures that the crystal device can be exposed to during oscillation. Temperature range over which the crystal's characteristics are guaranteed. See storage temperature range.

Operation Mode
The Operation Mode for AT cut quartz crystals is at the fundamental mode or an odd frequency harmonic of the fun damental frequency. For example, a crystal may operate at its fundamental frequency of 10 Mhz, or at odd harmonics: 30 Mhz (3rd overtone), 50 Mhz (5th overtone), and 70 Mhz (7th overtone). Original Equipment Manufacturer (OEM)
Maker of equipment that is marketed by another vendor, usually under the name of the reseller. The OEM may only manufacture certain components, or complete computers, which are then often configured with software, and/or other hardware by the reseller.

Oscillation mode
A quartz crystal is designed to vibrate on its fundamental frequency or one of its overtones. This becomes important between the 24 MHz to 40 MHz range. Crystals in that frequency range may be made as either a high fundamental or a low 3rd overtone. Fundamental mode crystals at these frequencies become more expensive, because the quartz blank is extremely thin, difficult to handle, and subject to a higher rate of breakage in processing. If you are able to use the 3rd overtone crystal instead of the fundamental, your cost savings may be significant. As the frequency range is extended, the oscillation mode of the crystal changes to other overtones. Crystals in the range of 60-110 MHz are generally 5th overtones, while crystals in the range of 110-175 MHz generally are 7th overtones.

Oscillator
An electronic circuit that produces an output signal of a specific frequency. An oscillator generally consists of an amplifier having part of its output returned to the input by means of a feedback loop; the necessary and sufficient condition for oscillation is that the signal, in passing from input to output and back to input via the feedback loop, arrive at the input with no change in amplitude or phase. If this condition is met for only a single frequency, the output is a pure sine wave; if it is met for more than one frequency, the output is a complex wave. Some oscillators are designed to operate under certain conditions so that the output is a square wave, a triangular wave, or a pulse. In some cases, a very stable mechanical oscillator, such as a specially prepared quartz crystal, may be coupled to an electronic oscillator to enhance its frequency stability.

Output
The output of a hybrid crystal clock oscillator is a highly stable reference signal.

Output enable function
The function to change the output signal.

Output frequency
The frequency signal generated by an oscillator circuit.

Output load
The power-consuming element connected to the output of a circuit.

Output voltage levels
In digital logic, voltage levels are referred to in terms of logic "0" and logic "1". These levels vary depending on the type of output logic required for the application.

Output wave shape
Graph of the output frequency vs. time. This can be a square, sine, or trapezoid.

Ovenized crystals
An ovenized crystal is any crystal made to operate at a temperature above the anticipated ambient temperature (typically +50°C to +110°C) in order to eliminate changes in frequency due to the change in temperature. See precision crystals.

Overshoot/Undershoot
This effect is commonly called ringing. The output voltage can exceed the steady state plateau of either the logic "0" state or the logic "1" state for a period of time. This ringing will decrease in amplitude until the steady state plateau is reached. An unmatched impedance load presented to the oscillator output causes the ringing. It becomes more pronounced as the rise/fall times decrease and the output frequency increases. Proper output loading and good R.F./Microwave transmission line techniques must be used to prevent ringing on the waveform.

Overtone order
The numbers allotted to the successive overtones of a given mode of vibration from the integral numbers commencing with the fundamental as unity.

Overtones
Crystals can vibrate at many harmonic frequencies. Frequencies, which are multiples of the lowest or fundamental frequency, are referred to as overtone frequencies. The overtones are usually referred to by the number of the overtone. An odd numbered multiple of the fundamental frequency.

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PA
Abbreviation for power amplifier.

Package
Physical holder of the crystal unit.

PAE
Abbreviation for power added efficiency.

PAR
Abbreviation for peak-to-average ratio.

Parabolic temperature curve
BT-cut and Tuning Fork crystals' frequencies follow a parabolic curve over temperature. The frequency will decrease as the temperature goes above or below the turnover temperature.

Parallel resonant
A parallel resonant oscillator circuit uses a crystal unit that is designed to operate with a specified value of load capacitance. This will result in a crystal frequency higher than the series resonant frequency, but lower than the true parallel resonant frequency.

Parts per million (PPM)
A method of calculation used to specify the permissible frequency deviation of a crystal or oscillator. May also be abbreviated as ppm. Both are correct.

Passband
A frequency range in which attenuation is guaranteed to be equal to or less than a designated value in dB, typically 3 dB.

PCB
Abbreviation for printed-circuit board.

PCN
Abbreviation for personal communications network.

PCS
Abbreviation for personal communications system.

PDC
Abbreviation for Pacific digital cellular.

Peak-to-peak (P-P)
The difference between the maximum positive and the maximum negative amplitudes of a waveform.

PECL
Abbreviation for positive emitter-coupled logic.
Personal Communications Industry Association (PCIA)
A trade group representing PCS, SMR, private radio and other wireless users and carriers.

Personal digital assistant (PDA)
A term for any small mobile hand-held device that provides computing and information storage and retrieval capabilities for personal or business use, often for keeping schedule calendars and address book information handy.

Phase bandwidth
Of a network or device, the width of the continuous frequency range over which the phase-vs.-frequency characteristic does not depart from linearity by more than a stated amount.

Phase modulation (PM)
A method of impressing data onto an alternating-current (AC) waveform by varying the instantaneous phase of the wave. This scheme can be used with analog or digital data.

Phase noise
The ratio of the power density of one phase modulation sideband to the total signal. It is usually specified as the single side band (SSB) power density in a 1Hz bandwidth at a specified offset frequency from the carrier. It is measured in dBc/Hz.

Phase shift
The change in phase of a periodic signal with respect to a reference.

Phase-locked loop (PLL)
An electronic circuit that controls an oscillator so that it maintains a constant phase angle relative to a reference signal.

PHEMT
Abbreviation for pseudomorphic high-electron-mobility transistor.

Pico
A prefix used to describe a sub-multiple of a number. One pico is one trillionth, 10-12, of a unit. See picoFarad.

PicoFarad
A fractional part, 10-12, (one trillionth) of one Farad. Abbreviated as pF.

Piezoelectric
A material that generates an electric charge when mechanically deformed. Conversely, when an external electric field is applied to piezoelectric materials they mechanically deform.

Piezoelectric effect
Voltage produced between surfaces of a solid dielectric (nonconducting substance) when a mechanical stress is applied to it. A small current may be produced as well. The effect, discovered by Pierre Curie in 1883, is exhibited by certain crystals, e.g., quartz and Rochelle salt, and ceramic materials. When a voltage is applied across certain surfaces of a solid that exhibits the piezoelectric effect, the solid undergoes a mechanical distortion. Piezoelectric materials are used in transducers, e.g., phonograph cartridges, microphones, and strain gauges, which produce an electrical output from a mechanical input, and in earphones and ultrasonic radiators, which produce a mechanical output from an electrical input. Piezoelectric solids typically resonate within narrowly defined frequency ranges; when suitably mounted they can be used in electric circuits as components of highly selective filters or as frequency-control devices for very stable oscillators.

Piezoelectricity
Electrical polarization produced by certain classes of crystals when the crystal is mechanically stressed.

Piezoid
A body of some special shape cut from a crystal having piezoelectric properties and used as an electromechanical transducer.

Pins
Thick short pins used in the hermetically sealed packaging of crystals to connect the plating on the crystal to the oscillator circuit normally .238" minimum in length and .03" to .05" in diameter. Typically used in applications where the crystal is inserted into a socket. See leads.

Plate
The quartz blank or resonator.

Plating
Thin, adherent layer of metal on a quartz blank.

PLO
Abbreviation for phase-locked oscillator.

Polish
A process used in the manufacture of some types of quartz crystals. The polish process results in a very fine surface finish. The word "polish" is also used to define the material used in the polish process, as well as the process itself.

Precise frequency
A frequency that is maintained to the known accuracy of an accepted reference frequency standard.

Precision crystals
Tight tolerance crystals having a calibration tolerance of less than ±10 PPM and or a temperature tolerance of less than ±10PPM or any other special processing requirements such as ovenized crystals, low phase noise crystals, Quartz Microbalance crystals, BT cut crystals, SC cut crystals , IT cut crystals, and FC cut crystals.

Primary frequency
A frequency that is assigned for usual use on a particular circuit. The first-choice frequency that is assigned to a fixed or mobile station for radiotelephone communications.

Primary frequency standard
A frequency source that meets national standards for accuracy and operates without the need for calibration against an external standard.

Protected frequency
A frequency that is not to be deliberately jammed by friendly forces, usually during a specified period.

Phase shift keying (PSK)
In digital transmission, angle modulation in which the phase of the carrier is discretely varied in relation either to a reference phase or to the phase of the immediately preceding signal element, in accordance with data being transmitted.

Public Safety Wireless Advisory Committee (PSWAC)
The FCC group that identified the safety community's wireless needs, motivating the commission’s decision to reallocate 24 MHz currently used by broadcasters to public safety agencies.

Public Utilities Commission
State regulatory administrative body that directs intrastate utilities, including telecommunications. Also known as Public Service Commission (PSC). The general name for the state regulatory body charged with regulating utilities including telecommunications.

Pullability
The change in frequency of a crystal unit, either from the natural resonant frequency (Fr) to a load resonant frequency (FL), or from one load resonant frequency to another. The frequency can be pulled in a parallel resonant circuit by changing the value of load capacitance. A decrease in load capacitance causes an increase in frequency, and an increase in load capacitance causes a decrease in frequency.

Pulse-code modulation (PCM)
Modulation in which a signal is sampled, and the magnitude (with respect to a fixed reference) of each sample is quantized and digitized for transmission over a common transmission medium.

PXO
Precision clock oscillators. PXO applications include PCS base stations, cellular base stations, telecom and wireless infrastructure, and digital switching.

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Q
Abbreviation for quality factor. It is the ratio of energy stored in a system divided by the energy dissipated in the system. Used to characterize the acoustic loss in quartz crystal resonators.

QASK
Abbreviation for quadrature amplitude shift keying.

Quadrature amplitude modulation (QAM)
Quadrature modulation in which the two carriers are amplitude modulated. In analog communications, the representation (i.e., transmission) of digital information by encoding bit sequences of fixed, specified length (number of bits), and representing these bit sequences as a function of (a) the amplitude of an analog carrier; or (b) a phase shift of the analog carrier with respect to the phase that represented the preceding bit sequence, and where the permissible phase shift is an integral multiple of /2 radians (90°, or one-quarter unit interval); or (c) both.

Quadrature phase shift keying (QPSK)
Abbreviation for quadrature phase shift keying.Phase-shift keying in which four different phase angles are used. Each of the angles is usually 90° out of phase.

Quartz
The crystalline form of Silicon Dioxide (SiO2). Quartz is the material from which a blank is made.

Quartz blank
See blank.

Quartz clock
A clock containing a quartz oscillator that determines the accuracy and precision of the clock.

Quartz crystal
Synthetic quartz is composed of Silicon and Oxygen (Silicon Dioxide SiO2) and is cultured in autoclaves under high pressure and temperature. Quartz exhibits piezoelectric properties that generate an electrical potential when pressure is applied on the surfaces of the crystal. Conversely, when an electrical potential is applied to the surfaces of a crystal, mechanical deformation or vibration is generated. These vibrations occur at a frequency determined by the crystal design and oscillator circuit. Under proper conditions, quartz can be used to stabilize the frequency of an oscillator circuit.

Quartz crystal microbalance (QCM)
A piezoelectric quartz crystal that utilizes the Converse Piezoelectric Effect to determine mass changes as a result of frequency change of the crystal. Material is coated onto the crystal that attracts a certain other material. When this other material becomes attached, it lowers the crystal frequency, the amount being directly related to its mass. The Sauerbrey equation relates the frequency change to the mass change. The mass change can be in the nanogram range.
Sauerbrey equation: Δf = -Δmdf2/_qvq
where:
Δf = change in frequency
Δmd = change in mass density (md, mass per surface area)
f2 = frequency squared
_q = density of quartz = 2650 kg m-3
vq = propagation of sound in quartz = 3340 m s-1

Quartz crystal oscillator
A timing device that consists of a crystal and an oscillator circuit, providing an output waveform at a specified reference frequency.

Quartz crystal unit
A completed quartz crystal, including a resonator plate with electrodes, a holder with suitable mounting structures, and a permanently sealed cover. Usually called a crystal.

Quartz oscillator
An oscillator in which a quartz crystal is used to stabilize the frequency.

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r face
One of the three smaller faces which occur at the ends of the natural quartz crystal.

R face
One of the three larger faces which occur at the ends of the natural quartz crystal.

Radiation
The outward flow of energy from any source in the form of radio waves.

Radio
Telecommunication by modulation and radiation of electromagnetic waves. A transmitter, receiver, or transceiver used for communication via electromagnetic waves. A general term applied to the use of radio waves.

Radio control
The remote control of an apparatus by signals conveyed by electromagnetic waves.

Radio frequency (RF)
A term that refers to alternating current (AC) having characteristics such that, if the current is input to an antenna, an electromagnetic (EM) field is generated suitable for wireless broadcasting and/or communications.

Radio frequency interference (RFI)
Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment.

Radio telephony
The use of radio to communicate sounds.

Radio wave
An electromagnetic wave of a frequency arbitrarily lower than 3000 GHz.

Radiocommunication
Telecommunication by means of radio waves.

Radiotelegraphy
The use of radio (instead of wire) to communicate a message(s) over a distance.

RbXO
Rubidium-crystal oscillator often used in satellite terminals and bistatic and multistatic radar.

Reactance
The opposition to an alternating current presented by inductance, capacitance, or a combination of the two. Reactance is measured in ohms and is represented by the letter X.

Read-only memory (ROM)
A memory in which data, under normal conditions, can only be read.

Recrystalling
The removal of one crystal and the replacement by a crystal of a different frequency and the realignment of the equipment.

Refarming
An FCC initiative to promote more efficient use of the frequency bands below 512 MHz allocated to private land mobile radio services.

Reference edge
The edge of a blank or wafer identified for use in orienting the blank or wafer on an x-ray chuck for making orientation measurements.

Reference flat
The flat edge on an otherwise circular blank for use as a reference edge. Called an X-flat when perpendicular to the X-axis.

Reference frequency
Frequency having a fixed and specified position with respect to the assigned frequency.

Relative Bechmann Angle (RBA)
Relative Bechmann Angle is the apparent angle of orientation of an AT crystal blank, which is derived from a plot of the temperature vs. frequency characteristic of a crystal resonator.

Repeater
Devices that receive a radio signal, amplify it and re-transmit it in a new direction. Used in wireless networks to extend the range of base station signals, thereby expanding coverage – within limits – more economically than by building additional base stations. They are typically used for buildings, tunnels or difficult terrain.

Resistance weld
Procedure involving pressure sealing with electricity and backfilling with nitrogen to force out oxygen and moisture. This results in superior aging characteristics.

Resistance
In a device, circuit, or component, the opposition to current flow. Resistance is identified by the letter R and is measured in ohms.

Resistor
An electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor. A component used to introduce resistance into a circuit.

Resonance
The creation of vibrations in a system by the application of a periodic force. The state that exists when the frequency of the applied force is equal to the natural frequency of the system.

Resonance resistance (Rr, R1)
The resistance of the crystal unit alone at the resonance frequency.

Resonant frequency
The natural frequency at which a circuit oscillates or a device vibrates. Abbreviated as Fr or fr.

Resonator
A body that is capable of being set into resonance by the application of a periodic force. See blank and plate.

Resonator plate
The quartz blank or resonator.

RFIC
Abbreviation for radio frequency integrated circuit.

Ripple
The difference between maximum and minimum attenuation in the passband.

RISC
Acronym for reduced instruction set chip, reduced instruction set computing.

Rise and fall times
Rise time is the amount of time, measured in nanoseconds that it takes to go from the logic "0" state to the logic "1" state. The fall time is the transition time from logic "1" state to logic "0" state. The time is measured at the 10% and the 90% points of the voltage transition.

Rise time
The rise time, measured in nanoseconds (nSec), is defined as the transition time from an output logic low to an output logic high. See fall time.

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Satellite
A radio relay station that orbits the Earth. A complete satellite communications system also includes earth stations that communicate with each other via the satellite.

Satellite communications
A telecommunications service provided via one or more satellite relays and their associated uplinks and downlinks.

Satellite dish
A kind of antenna used to pick up transmissions broadcast from a satellite.

Satellite link
A radio link between a transmitting Earth station and a receiving Earth station through one satellite.

SAW
Abbreviation for surface acoustic wave.

S-band
The frequency spectrum near 2 GHz used for land-based microwave and some mobile satellite communications.

SC cut
A double rotated crystal cut good for ovenized application with good aging rates and low phase noise. SC stands for Stress Compensated. SC-cut crystals have an improved temperature and frequency characteristic for ovenized applications (OCXO). The frequency vs. temperature curve is a sine with the inflection temperature at ~ +95°C. This crystal operates in the thickness shear
mode. Preferred for ovenized oscillators (OCXO) such as space systems, and Global Positioning Satellite Systems.

SCM
Abbreviation for signal code modulation.

Second
The basic unit of measure of time, equivalent to "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom." For our purposes, one "second" is 1/60th of a minute.

Secondary frequency standard
A frequency standard that does not have inherent accuracy, and therefore must be calibrated against a primary frequency standard.

Series resonance
The condition that exists when a crystal unit is operated without the presence of load capacitance. Series resonance is frequently shortened to the word series. See load resonance.

Series vs. parallel load resonance
A crystal can be used in an oscillator circuit to operate in either of two resonant modes: Series Resonance or Parallel Load Resonance (also known as antiresonance). The crystals used in these two types of modes are physically the same crystal, but calibrated to slightly different frequencies.
When a crystal is placed into an oscillator circuit, they oscillate together at a tuned frequency. This frequency is dependent upon the crystal design and the amount of load capacitance, if any, the oscillator circuit presents to the crystal. Specified in picoFarads (pF), load capacitance is comprised of a combination of the circuit’s discrete load capacitance, stray board capacitance, and capacitance from semiconductor Miller effects.

Short messaging service (SMS)
A service for sending messages of up to 160 characters (224 characters if using a 5-bit mode) to mobile phones that use Global System for Mobile (GSM) communication.

Shunt capacitance
Abbreviated as C0. A parameter associated with a quartz crystal unit, used to identify the capacitance resulting from the presence of the electrodes plus stray capacitance associated with the holder. The static capacitance between the crystal terminals. Measured in picoFarads (pF), shunt capacitance is present whether the device is oscillating or not (unrelated to the piezoelectric effect of the quartz). Shunt capacitance is derived from the dielectric of the quartz, the area of the crystal electrodes, and the capacitance presented by the crystal holder.

Sideband
The bands of frequency above and below a carrier frequency that are produced by its modulation.

SiGe
Abbreviation for silicon-germanium.

Signal
Detectable transmitted energy that can be used to carry information. As applied to electronics, any transmitted electrical impulse.

Signal frequency shift
Any change in frequency. Any change in the frequency of a radio transmitter or oscillator.

Signal to noise ratio (S/N)
Relative power of the signal to the noise. As the ratio decreases on a line, it becomes more difficult to distinguish between information and non-information (noise). S/N deteriorates with distance because the noise builds every time the signal is repeated.

Signal to noise ratio (SNR)
The ratio of the amplitude of the desired signal to the amplitude of noise signals at a given point in time. SNR is usually expressed in dB.

Sine wave
A periodic wave that can be represented by a sine curve. The amplitude of such a wave is a function of the sine of a linear quantity such as phase or time.

Single-frequency interference
Interference caused by a single-frequency source.

SiO2
Abbreviation for silicon dioxide.

Smart antenna
An antenna system whose technology enables it to focus its beam on a desired signal to reduce interference. A wireless network would employ smart antennas at its base stations in an effort to reduce the number of dropped calls, improve call quality and improve channel capacity.

SMD
Abbreviation for surface mount device. See surface mount.

SMF
Abbreviation for surface-mount filter.

SMP
Abbreviation for surface-mount package.

SOIC
abbreviation for small-outline integrated circuit.

SPDT
Abbreviation for single-pole double-throw.

Special cut crystals
Special cut crystals are those crystals that have been cut at a different angle of orientation to enhance performance for specific needs. Typical special cuts would include BT cut crystals, SC cut crystals, IT cut crystals, and FC cut crystals.

Special emergency radio service
A Private Land Mobile Radio Service employed by persons or organizations engaged in emergency medical and rescue service, health care or similar activity.

Specialized mobile radio (SMR)
A two-way radio service provided within a designated portion of the 800 and 900 MHz frequency bands.

Specified frequency
The frequency specified by the customer.

Spectrum
The electromagnetic radio spectrum. The FCC grants authorizations and licenses to private and governmental entities to use specified portions under certain conditions.

Spectrum assignment
Federal government authorization for use of specific frequencies or frequency pairs within a given allocation, usually at stated a geographic location(s). Mobile communications authorizations are typically granted to private users, such as oil companies.

Spread spectrum
Telecommunications techniques in which a signal is transmitted in a bandwidth considerably greater than the frequency content of the original information.

SPICE
Abbreviation for Simulation Program with Integrated Circuit Emphasis.

Spur
A substitution for the term spurious frequency response. The word "spur" is used to refer to a frequency occurring at some point higher than the desired mode, but lower than the next overtone.

Spurious frequency response
In radio reception, a response in the receiver intermediate frequency (IF) stage produced by an undesired emission in which the fundamental frequency (or harmonics above the fundamental frequency) of the undesired emission mixes with the fundamental or harmonic of the receiver local oscillator.

Spurious Modes
All quartz crystals have multiple vibrational modes. Spurious modes refer to those that are unwanted and can be a problem if the response is as strong as the main mode.

SSB
Abbreviation for single sideband.

SSPA
Abbreviation for solid state power amplifiers.

Stability
The change in the oscillator frequency, referred to the desired oscillator frequency, caused by temperature changed.

Standard calibration tolerance
The allowable deviation from nominal, expressed in parts per million — ppm, at a specific temperature at +25 °C.

Start-Up
The period from the instant voltage is applied to the oscillator until the oscillator output is stabilized.

Start-up time
The specified time from oscillator power-up to the time the oscillator reaches steady state oscillation.

Starting resistance
The non-linear change in the resistance of a crystal as a function of the power level used to drive the crystal.

Static capacitance
See shunt capacitance.

Stone (quartz)
A term used to describe a quartz crystal before any machining operations have been done. The synthetic single crystals grown in the Hydrothermal Process are referred to as a "Stone".

Stopband
The part of the frequency spectrum that is subjected to specified attenuation of signal strength by a filter. See attenuation.

Storage temperature range
The minimum and maximum temperatures that the device can be stored or exposed to when in a non-oscillation state. After exposing or storing the device at the minimum or maximum temperatures for a length of time, all of the operating specifications are guaranteed over the specified operating temperature range.

Strip resonator
A small AT cut crystal whose width is much smaller than its length. The crystal is a finite plate design requiring exact mathematical analysis to achieve good performance. The length of the resonator can be parallel to either the X or Z axis of quartz.

Superheterodyne receiver
The most widely used type of radio receiver, in which all incoming modulated radio-frequency signals are converted to a common intermediate-frequency or IF carrier value for additional amplification and selectivity prior to demodulation. The advantage to this method is that most of the radio's signal path has to be sensitive to only a narrow range of frequencies. The diagram below shows the basic elements of a single conversion superheterodyne receiver.

Supply voltage
The DC input voltage necessary for oscillator operation, specified in volts.

Surface mount (SM)
A component, either active or passive, having no separate leads but which is part of the component body to permit direct mounting on a printed circuit board.

Surface-mount technology or surface-mount toroidal (SMT)
A surface mount device is a component, either active or passive, having no separate leads but which is part of the component body to permit direct mounting on a printed circuit board.

Symmetry
Symmetry is defined as the ratio of amount of time the voltage is in the logic "1" state compared to the time in the logic "0" state. The measurements are taken at the 50% points of the voltage transition between the two logic states. The time period of one cycle of the waveform is calculated first as below.
1/Frequency in Hertz = Time Period in Seconds
Next, the time period of the logic "1" state is measured from the 50% point of the waveform's positive voltage transition to the 50% point of the waveform’s negative voltage transition, then compared to the total waveform period. The calculation for symmetry is shown below:
Logic "1" Time in Symmetry/Period of One Cycle X 100 = % Symmetry
For the % symmetry of the logic "0" state, subtract the logic "1" symmetry from 100%. For example, 40/60% means that the waveform is in its logic "1" state 40% and in the logic "0' state 60% of the total waveform time period.

Synchronous digital hierarchy (SDH)
A standard technology for synchronous data transmission on optical media. It is the international equivalent of Synchronous Optical Network.

Synchronous optical network (SONET)
Abbreviation for synchronous optical network. An interface standard for synchronous optical-fiber transmission, applicable to the Physical Layer of the OSI Reference Model.

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T/C
Temperature vs. Frequency characteristic of a crystal resonator.

T/R
Abbreviation for transmit/receive.

Tape and reel
Refers to the packaging method used to accommodate automated pick-and-place equipment.

Target Frequency - Crystal
The Target Frequency of a crystal is specified in Mhz or kHz. The cut, size and shape of the resonator determine the frequency, or rate of vibration. In “AT” cut crystals, the precision with which thickness is controlled determines the variation from crystal to crystal to crystal; therefore a Frequency Calibration Tolerance should be specified along with the Target Frequency.

Target Frequency - Oscillator
The Target Frequency of an oscillator is the desired output frequency of an oscillator, specified in MHz or kHz
(megahertz or kilohertz) @ 25°C. A Frequency Tolerance should be specified along with the Target Frequency.

TCVCXO
Temperature compensated/voltage controlled crystal oscillator is a VCXO coupled to a temperature compensation circuit allowing a variable frequency output that is also temperature compensated often used for frequency control in tactical radios, telecom timing modules (Stratum 3 Type), wireless systems reference oscillator, phase lock loop (PLL) Circuits in telecom, timing recovery, wireless base station channel or timing reference, and fiber optic timing references.

TCXO
Temperature-compensated crystal oscillator often used often used for frequency control in tactical radios, telecom timing modules (Stratum 3 Type), wireless systems, and reference oscillators.

TDD
Abbreviation for time division duplex.

Telecommunications
Any communication process that allows the transmission of information from a sender to a receiver by means of an electromagnetic or lightwave medium.

Telemetry tracking and control (TT&C)
Functions that provide for the monitoring and control of satellites.

Telemetry
The use of telecommunication for automatically indicating or recording measurements at a distance from the measuring instrument.

Temperature range
The minimum and maximum temperature for which the deviation from the nominal frequency will not vary by a given amount.

Temperature Tolerance over Operating Temperature Range
Temperature Tolerance is the amount of frequency deviation that will occur over the Operating Temperature Range with respect to the frequency @ 25°C. This deviation is usually specified as a minimum and a maximum frequency deviation, expressed in ±ppm (parts per million). This deviation is often associated with other specified operating conditions such as Load Capacitance and Drive Level. Temperature is a major influence on crystal frequency. Small pieces of quartz material used for making crystal resonators are obtained by cutting the quartz at specific angles to the chosen axes of quartz bars. The choice of angle and axes determines the frequency stability over temperature. Figure 3 shows Frequency vs. Temperature plots of crystals, varied by a few minutes of angle rotation.

TeraHertz
The terahertz, abbreviated THz, is a unit of electromagnetic (EM) wave frequency equal to one trillion hertz (1012 Hz). The terahertz is used as an indicator of the frequency of infrared (IR), visible, and ultraviolet (UV) radiation. The terahertz is not commonly used in computer and wireless technology.

Termination impedance
The impedance that should be presented to the source and load side of the filter to ensure proper performance.

Test set
A device used to measure the frequency and resistance characteristics of a quartz crystal unit. Often called a crystal impedance meter, it is abbreviated as "C.I.M."

TETRA
Abbreviation for Trans European Trunked Radio or Terrestrial Trunked Radio is a set of standards developed by the European Telecommunications Standardization Institute (ETSI) that describes a common mobile radio communications infrastructure throughout Europe.

Thru Hole
A conductor used to make electrical and mechanical connection between conductive patterns on opposite sides of a printed circuit board.

Time division multiple access (TDMA)
A communications technique that uses a common channel (multipoint or broadcast) for communications among multiple users by allocating unique time slots to different users. TDMA is used extensively in satellite systems, local area networks, physical security systems, and combat-net radio systems.

Tolerance and stability
Three main components of frequency control product specifications are:
1. Calibration tolerance at room temperature (25°C)
2. Stability over the temperature range
3. AgingCalibration at room temperature is a measurement of the accuracy of the frequency at +25°C. crystal frequencies are adjusted within the stated tolerance by changing the mass of the electrode. Lower frequencies are less sensitive to mass change and are therefore easier to hold tighter tolerances. Tolerance and stability are measured in parts per million (ppm).

Transducer
Device that accepts an input of energy in one form and produces an output of energy in some other form, with a known, fixed relationship between the input and output. One widely used class of transducers consists of devices that produce an electric output signal, e.g., microphones, phonograph cartridges, and photoelectric cells

Transistor
An active semiconductor device, usually made of silicon or germanium, having three or more electrodes. The three main electrodes used are the emitter, base, and collector.

Transition region
The part of the spectrum between the passband and the stopband.

Transmission
The sending and receiving of telecommunications messages through appropriate channels.

Transmission control protocol (TCP)
In the Internet Protocol suite, a standard, connection-oriented, full-duplex, host-to-host protocol used over packet-switched computer communications,

Trim effect
In a crystal oscillator, the degradation of frequency-vs.-temperature stability, and marked frequency offset, resulting from frequency adjustment which produces a rotation or distortion, or both, of the inherent frequency-vs.-temperature characteristic.

Trim sensitivity
A measure of the incremental fractional frequency change for an incremental change in the value of load capacitance. Trim sensitivity (S) is expressed in terms of PPM/pF and is calculated with the following equation: where (Ct) is the sum of the shunt capacitance (CO) and the load capacitance (CL).

Trimmability
The ability to adjust the frequency of an oscillator.

Tri-state
The tri-state function allows the oscillator to be isolated from the circuit upon application of a command signal. When this feature is activated, the output of the oscillator is in tri-state mode. The tri-state mode allows the customer to remove the oscillator from their circuit without physically removing it. Useful for tuning, testing or trouble shooting their board.

Tri-state output
An oscillator with this feature allows the output to be placed into a high impedance state. This feature is activated by the application of a logic control voltage to pin 1 of the oscillator.

TTL
Abbreviation for transistor-transistor logic.

Turning point
An AT cut crystal has a temperature vs. frequency characteristic that can be represented by a third order polynomial. The turning points are points of zero slope where the slope reverses sign. Usually there is a lower turning point around -4° C and an upper turning point around +55° C. Often ovenized oscillators hold the temperature of the crystal at the upper turning point to obtain maximum temperature stability.

Turnover temperature
The temperature at which the frequency is at the top of the parabolic curve.

Twinning
A condition existing within a quartz stone wherein the optic and/or the electric axis suddenly reverses its natural order of polarity. A single piece of quartz material, which contains both left and right handed regions, is said to be "twinned".

Type/Angle of Quartz Cut
The type and angle of a quartz cut affects the crystal device operating parameters, the most significant being frequency stability over temperature. The frequency stability is dependent upon the plane or the angle of the crystal element in relation to the crystalline axes of the crystal. The plane or angle is referred to as the crystal cut. A common type of thickness shear crystal fabricated from Y bar quartz is the AT cut. The frequency stability and operating temperature range required by the customer determine the angle of cut utilized.

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Ultra-high frequency (UHF)
The part of the radio spectrum from 300 to 3000 MHz that includes TV channels 14-83, as well as many land mobile and satellite services.

Ultra-low frequency (ULF)
Frequencies from 300 Hz to 3000 Hz.

Uni-directional antenna
Antenna that radiates most of its power in one direction.

Unity
The factor of one.

Universal asynchronous receiver transmitter (UART)
The microchip with programming that controls a computer's interface to its attached serial devices. Specifically, it provides the computer with the RS-232C Data Terminal Equipment (DTE) interface so that it can "talk" to and exchange data with modems and other serial devices.

Universal mobile telecommunications service (UMTS)
Universal mobile telecommunications service is a so-called "third-generation (3G)," broadband, packet-based transmission of text, digitized voice, video, and multimedia at data rates up to 2 megabits per second (Mbps) that will offer a consistent set of services to mobile computer and phone users no matter where they are located in the world. Based on the GSM (Global System for Mobile communication), UMTS, endorsed by major standards bodies and manufacturers, is the planned standard for mobile users around the world by 2002.

Unwanted response
Frequency responses other than the main, or desired response, which the crystal elements have.

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VCO
Voltage-controlled oscillator. Applications may include FSK generation, voltage and current-to-frequency conversion, stable phase-locked loop, waveform generation – triangle, sawtooth, pulse, squarewave, FM and sweep generation.

VCTCXO
A voltage controlled temperature compensated crystal oscillator. VCTCXOs have a wide range of applications in wireless telecommunications such as portable telephone, VHF/UHF, CATV, instrument for GPS, PLL circuits, AFC circuits, and Radio Frequency (RF) modules.

VCXO
A crystal controlled oscillator where the frequency changes in direct proportion to the application of a control voltage. Often used in phase lock loop (PLL) circuits in telecom timing recovery, wireless base station channel or timing reference, and fiber optic timing reference.

Very-high frequency (VHF)
The part of the radio spectrum from 30 to 300 MHz that includes TV channels 2-13, the FM broadcast band, and some marine, aviation and land mobile services.

Very small aperture terminal (VSAT)
Very small aperture terminal (satellite service) is satellite communications system that serves home and business users. A VSAT end user needs a box that interfaces between the user's computer and an outside antenna with a transceiver.

Vestigial side band (VSB)
Modified AM transmission in which one sideband, the carrier, and only a portion of the other sideband are transmitted.

VOFDM
Abbreviation for vector orthogonal frequency division multiplexing.

Volt
The basic practical unit of difference of (electrical) potential.

Voltage
Also called electromotive force. Voltage is a quantitative expression of the potential difference in charge between two points in an electrical field. The greater the voltage, the greater the flow of electrical current (that is, the quantity of charge carriers that pass a fixed point per unit of time) through a conducting or semiconducting medium for a given resistance to the flow. Voltage is symbolized by an uppercase italic letter V or E.

Voltage standing wave ratio (VSWR)
In a transmission line, the ratio of maximum to minimum voltage in a standing wave pattern.

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Wafer
A thin slice of semiconducting material, such as a silicon crystal, upon which microcircuits are constructed by diffusion and deposition of various materials. See blank.

Warm-up
The time required for an oscillator's frequency to settle within a given tolerance of the frequency several hours later.

Wavelength
The length of one complete wave of an alternating or vibrating phenomenon, generally measured from crest to crest or from trough to trough of successive waves.

W-CDMA
Abbreviation for wideband code-division multiple access.

White noise
Noise having a frequency spectrum that is continuous and uniform over a specified frequency band. Note: White noise has equal power per hertz over the specified frequency band. Synonym: additive white gaussian noise.

Wideband
The property of any communications facility, equipment, channel, or system in which the range of frequencies used for transmission is greater than 0.1 % of the midband frequency. See broadband.

Wireless
Using the radio-frequency spectrum for transmitting and receiving voice, data and video signals for communications.

Wireless application protocol (WAP)
Specification for a set of communication protocols to standardize the way that wireless devices, such as cellular telephones and radio transceivers, can be used for Internet access, including e-mail, the World Wide Web, newsgroups, and Internet Relay Chat (IRC).

Wireless communication
Any broadcast or transmission that can be received through microwave or radio frequencies without the use of a cable connection for reception.

Wireless communication service
A radio service allocated spectrum at 2.305 – 2.360 MHz for flexible wireless use; due to its propagation characteristics, it is thought that the WCS likely will provide fixed wireless local loop service.

Wireless local area network (WAN)
A wireless data communications system that lies within a limited spatial area, has a specific user group, has a specific topology, and is not a public switched telecommunications network, but may be connected to one. LANs are usually restricted to relatively small areas, such as rooms, buildings, ships, and aircraft.

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X cut
A quartz wafer with the major surface of the wafer perpendicular to the X crystallographic axis.

XO
crystal oscillator often used for computer timing. An oscillator in which the frequency is controlled by a piezoelectric crystal.

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Y cut
A quartz wafer with the major surface of the wafer perpendicular to the Y crystallographic axis.

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Z cut
A quartz wafer with the major surface of the wafer perpendicular to the Z crystallographic axis.

ZZ' angle
The angle between the plane of the blank and the optic axis in quartz. The optic axis is the Z or c axis. This angle determines the frequency vs. temperature characteristic of the finished crystal resonator.

Zero angle
The angle of cut that will result in a resonator that has zero temperature vs. frequency slope at the inflection point. For a fundamental, AT-cut crystal this angle is about 35 degrees and 15 minutes of arc.