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Crystal and frequency control glossary

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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. he 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 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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