Page 50 - Electrical Engineering Dictionary

amplitron a classic crossed-field am- or a sinusoidal signal of the form
plifier in which output current is obtained
c(t) = cos(ω c t + θ c ).
primarily by secondary emission from the
negative electrode that serves as a cathode ω c isreferredtoasthe carrierfrequency.AM
throughout all or most of the interaction has the effect of shifting the frequency spec-
space. trumofx(t)byω c . Thesignalisrecoveredby
shifting the spectrum of x(t) back to its orig-
amplitude descriptor of the strength of a inal form. See also frequency modulation.
wave disturbance such as an electromagnetic
or acoustic wave. amplitude response the magnitude of the
steady-stateresponseofafixed, linearsystem
amplitude equations a form of the to a unit-amplitude input sinusoid.
Schr¨ odinger equation that describes the evo-
lution of a quantum mechanical system in amplitude spectrum the magnitude of
terms of only the coefficients of the preferred the Fourier transform |F(ω)|, −∞ <ω <
basis states. These coefficients are known ∞ of a signal f(t). For example, the ampli-
as quantum mechanical amplitudes and con- tude spectrum of a rectangular pulse of unit
tain both magnitude and phase information. width is given in the following figure: See
Amplitude equations are often used to gain also Fourier transform.
physical insight into interactions of quantum
systemswithelectromagneticfields. Seealso
Schr¨ odinger wave equation (SWE).

amplitude linearity qualitative measure
of the extent to which the output ampli-
tude of a device is a faithful reproduction of
its input, with no new frequency harmonics
added. A perfectly linear device would out-
put a scaled version of its input, where the
shape of the input waveform has been un-
altered (i.e., there is no distortion of the in-
put waveform). Viewed in the frequency do-
main, the output signal would contain only
Amplitude spectrum.
those spectral components found in the in-
put signal, and each frequency line would be
scaled by the same amount (i.e., by the gain
of the device). amplitude stabilization circuit a circuit
used to obtain a precise oscillation amplitude
of oscillators. These circuits are used in in-
amplitude modulation (AM) the process
strumentation when it is required to increase
of modulating a signal x(t) by a carrier wave
the purity of output signal and reduce the fre-
c(t) for transmission:
quency depression (especially in Meachem-
bridgeoscillatorwithcrystal)ofthemainhar-
y(t) = c(t)x(t),
monic by higher harmonics (van der Pol ef-
fect). Three types of circuits are used:
where y(t) is the signal to be transmitted.
1. An element of large inertia (tungsten
c(t) is either a complex exponential of the
lamp, thermistor) is included in the circuit at
form
a point where it can change the magnitude of
c(t) = e j(ω c t+θ c ) feedback, but not affect the frequency.

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2000 by CRC Press LLC