18WuD2x

302 frequency-response recorder • frequency-variation method
frequency-response recorder A graphic recorder
that automatically plots a frequency-response
curve for a device under test.
frequency run A test, or test sequence, that determines
the loss characteristics of a circuit as a
function of the operating frequency.
frequency scanning 1. A controlled fluctuation of
the transmitter frequency in a frequency-agile
radar or communications system. 2. In a programmable,
digital communications receiver or
transceiver, a form of simultaneous digital monitoring
of two or more channels. 3. The frequencyresponse
change in a spectrum analyzer.
frequency scaler See SCALER.
frequency-selection sensor A sensor that passes
or rejects phenomena at certain frequencies while
ignoring those at other frequencies.
frequency-selective relay See SELECTIVE RE-
LAY, 1.
frequency-sensitive bridge A bridge, such as the
Wien bridge or resonance bridge, that can be balanced
at only one frequency for a given set of
bridge-arm values.
frequency separator In a television receiver, the
circuit that separates horizontal- and verticalscanning
sync pulses.
frequency-shift keying Abbreviation, FSK. A
method of digital signal transmission. The logic 1
(high or mark) pulses are sent at a specific carrier
frequency, and the logic 0 (low or space) pulses
are transmitted at another frequency slightly
higher or lower than the logic 1 pulses. This is
the most primitive form of frequency modulation
(FM). The difference between the mark and space
frequencies is called the shift, and is usually
between 100 and 1000 Hz. Compare
AUDIOFREQUENCY-SHIFT KEYING.
frequency-shift radar See DOPPLER RADAR.
frequency span The difference f 2 – f 1 , where f 1 is
the lowest frequency in a given range of frequencies
and f 2 is the highest frequency. Compare
FREQUENCY SPREAD.
frequency spectrum All electromagnetic radiation,
from longest to shortest wavelengths, within
a set of specified limits.
frequency split 1. The difference between the receiver
frequency and the transmitter frequency in
a communications repeater. 2. See FREQUENCY
OFFSET, 2.
frequency spotting The setting-up of signals at
reference frequencies (usually harmonics of a
standard-frequency oscillator), and their use in
identifying unknown frequencies. Also see FRE-
QUENCY CALIBRATOR.
frequency spread The ratio f 2 /f 1 , where f 1 is the
lowest frequency in a given range of frequencies
and f 2 is the highest frequency. Compare FRE-
QUENCY SPAN.
frequency stability The degree to which a frequency
remains constant during variations in
temperature, current, voltage, and similar factors.
It is specified in Hertz (Hz), kilohertz (kHz),
or megahertz (MHz), or in parts per million per
unit of the variable parameter.
frequency standard A signal source of a precise
frequency, against which other signal sources
can be calibrated. See specifically PRIMARY FRE-
QUENCY STANDARD and SECONDARY FRE-
QUENCY STANDARD.
frequency sum In a beat-frequency system, the
quantity f 1 + f 2 , where f 1 is the lower frequency
and f 2 is the higher frequency. Compare FRE-
QUENCY DIFFERENCE, 2.
frequency swing See FREQUENCY DEVIATION, 1,
2.
frequency synthesizer A generator of signals at a
precise frequency or set of frequencies, generally
adjustable in discrete frequency steps. It is used
for test or communications purposes. The signals
are derived from a single-frequency source, usually
a crystal oscillator. Also see SIGNAL SYN-
THESIZER.
frequency tolerance The acceptable amount by
which a frequency can vary from its intended
value. The tolerance can be specified as a percentage
of the stated frequency, a certain number
of parts per million, or a certain number of hertz
(Hz), kilohertz (kHz), or megahertz (MHz). Example:
3.675000 MHz ±10 Hz.
frequency-to-voltage converter A device or circuit
that delivers an output voltage that is proportional
to the input frequency.
frequency translation 1. The conversion of a
given frequency band from one part of the electromagnetic
spectrum to another, without changing
the actual separation of channels or the
overall width of the band. 2. See FREQUENCY
CONVERSION.
frequency transmission The passage of a frequency
or band of frequencies from a mixture of
frequencies through a filter or other circuit. Compare
FREQUENCY REJECTION.
frequency tripler See TRIPLER, 2.
frequency-variation method A method of determining
the figure of merit (Q) of a tuned circuit by
varying the frequency of the applied test voltage