Page 203 - Electrical Engineering Dictionary

two-wave mixing, if the two laser beams are delay locked loop See delay-locked loop.
of the same frequency, a stationary interfer-
ence intensity pattern is formed. This leads to delay power spectrum a function charac-
a stationary volume refractive index grating. terizing the spread of average received power
Such a kind of two-wave mixing is referred as a function of delay. Can be obtained from
to as degenerate two-wave mixing. the scattering function by integrating over the
Doppler shift variable. See also scattering
degradation situation in which a signal function, multipath propagation.
has been corrupted by noise, blurred by some
point-spread function or distorted in some
delay profile See delay power spectrum.
other fashion.
delay range the difference in arrival times
degree of membership the degree to
between the first and last significant compo-
which a variable’s value belongs in a fuzzy
nent of the impulse response of a wideband
set. The degree of membership varies from
communication channel. Also known as the
0 (no membership) to 1 (complete member-
total excess delay.
ship).
degree of mobility each prismatic or rev- delay resolution the capability, measured
olute joint has one degree of freedom and in units of delay (seconds), of a signal used
provides the mechanical structure with a sin- for channel measurement to resolve received
gle degree of mobility. signal components which arrive with differ-
ent delays. If two signal components arrive at
degrees of freedom the number of in- the receiver with a delay separation less than
dependent position variables that have to be the delay resolution, they will be observed
specified in order to locate all parts of the as one signal, superimposed on each other.
mechanism is defined as a number of de- The actual value of the delay resolution de-
grees of freedom. Therefore, the degrees of pends on the criterion by which two signal
freedom is defined as the minimal number of components are defined to be resolved. An
position variables necessary for completely approximate measure is given by the inverse
specifying the configuration of the mecha- of the channel (or signal) bandwidth. See
nism. also multipath propagation.

degree of visual angle the angle sub- delay slot in a pipelined processor, a time
tended by an object of a given width a given slot following a branch instruction. An in-
distance away from the viewer. struction issued within this slot is executed
regardless of whether the branch condition is
delay (1) the time required for a signal to
met, so it may appear that the program is ex-
propagate along a wire.
ecuting instructions out of order. Delay slots
(2) the difference in the absolute angles
can be filled (by compilers) by rearranging
between a point on a wavefront at the device
the program steps, but when this is not pos-
output and the corresponding point on the in-
sible, they are filled with “no-operation” in-
cident input wavefront, expressed in seconds
structions.
or degrees. Delay can exceed 360 degrees.
Given by t d ,wehave
delay spread a measure of the time
through which the duration of a transmitted
t d = θ out − θ in
signal is extended by dispersion in a wide-
band communication channel. Usually mea-
delay angle See firing angle. sured as the RMS delay spread, i.e., the sec-

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