Page 41 - The Illustrated Dictionary of Electronics

5059F-pA_1-55 4/9/01 4:41 PM Page 26

26 amplifying delay line • amplitude selection

amplifying delay line A delay line that causes am- munications and broadcasting. The modulating-
plification of signals in a circuit intended for signal energy appears at sideband frequencies
pulse compression. above and below, and very close to, the carrier
amplistat A self-saturating magnetic amplifier. frequency. These sideband signals carry all the
amplitron A backward-wave amplifier used in mi- information. The extent of modulation is ex-
crowave circuits. pressed as a percentage, from 0, which represents
amplitude The extent to which an alternating or an unmodulated carrier, to 100, which repre-
pulsating current or voltage swings, positively sents full modulation. In a signal modulated 100
and negatively, from zero or from a mean value. percent, one-third of the power is used to convey
amplitude-controlled rectifier A thyratron- or the data; the other two-thirds is consumed by the
thyristor-based rectifier circuit. carrier. This form of modulation is essentially
amplitude density distribution A mathematical outmoded, although it is still used in the stan-
function giving the probability that, at a given in- dard broadcast band from 535 to 1605 kHz. See
stant in time, a fluctuating voltage has a certain FREQUENCY MODULATION, PHASE MODU-
value. LATION, SINGLE SIDEBAND.
amplitude distortion In an amplifier or network,
the condition in which the output-signal ampli-
tude exhibits a nonlinear relationship to the in-
put-signal amplitude.
amplitude error 1. The error in measuring the am-
plitude of a signal, normally expressed as a per-
centage of signal amplitude or as a percentage of
full scale. 2. The frequency at which the output
amplitude of a signal is in error by 1% with am-
plitude at 10% of full scale.
amplitude factor For an ac wave, the ratio of the
peak value to the rms value. The amplitude factor
of a sine wave is equal to the square root of 2 =
1.4142136.
amplitude fading In the propagation of electro-
magnetic waves, a condition in which the ampli-
tudes of all components of the signal (i.e., carrier
and sidebands) increase and decrease uniformly.
Compare SELECTIVE FADING.
amplitude/frequency response Performance of
an amplifier throughout a specified range, as ex-
hibited by a plot of output-signal amplitude ver-
sus frequency for a constant-amplitude input
signal.
amplitude gate A transducer that transmits only
those portions of an input wave that lie within
two close-spaced amplitude boundaries; also
called slicer. amplitude-modulation noise Spurious amplitude
amplitude limiter A circuit, usually with auto- modulation of a carrier wave by extraneous sig-
matic gain control (AGC), that keeps an amplifier nals and random impulses, rather than by the in-
output signal from exceeding a certain level, de- tended data-containing signal.
spite large variations in input-signal amplitude. A amplitude noise In radar, amplitude fluctuations
dc-biased diode performs passive limiting action of an echo returned by a target. This noise limits
via clipping. the precision of the system.
amplitude-modulated generator A signal genera- amplitude of noise The level of random noise in a
tor whose output is amplitude modulated. Usu- system. The amplitude of noise is measured in
ally, this instrument is an RF generator that is the same way that signal amplitude is measured.
modulated at an audio frequency. amplitude range The maximum-to-minimum am-
amplitude-modulated transmitter A radio- plitude variation of a signal. It can be expressed
frequency transmitter whose carrier is varied in as a direct numerical ratio or in decibels.
amplitude, according to the rate of change of amplitude response The maximum output obtain-
some data-containing signal (such as voice, mu- able at various frequencies over the range of an
sic, facsimile, television pictures, control signals, instrument operating under rated conditions.
or instrument readings). amplitude selection The selection of a signal, ac-
amplitude modulation Abbreviation, AM. A cording to its correspondence to a predetermined
method of conveying intelligence in wireless com- amplitude or amplitude range.