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Crystal and frequency control glossary

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P

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.

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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.

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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.

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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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