Page 260 - Electrical Engineering Dictionary

EPROM See erasable programmable equalizer minimum mean squared error
read-only memory. (MMSE) a digital equalizer (filter) in
which the coefficients are selected to min-
equal area criterion a criterion used of- imize the mean-squared error between the
ten in power system studies whenever the transmitted symbols and the filter outputs.
stability of a single machine system needs
to be determined without actually solving equalizer transversal an equalizer that is
the swing equation. It is a direct approach. implementedasafiniteimpulseresponsedig-
Seealsoelectromechanicalequationorswing ital filter. Also called a “tapped-delay line.”
equation.
equalizer zero-forcing an equalizer in
equal gain combining a method of di- which the parameters are adjusted to elimi-
versity combining in which the outputs of nate intersymbol interference (at the expense
several communication channels are first co- of enhancing the noise).
phased and then summed. The resulting sig-
nal has increased mean power and reduced equalizing pulse interval series of 12
fade depth. See also angle diversity, antenna sync pulses inserted in the vertical blank-
diversity. ing interval of each field of the NTSC com-
posite video signal. The equalizing pulse
equal ripple in-band power gain or power makes a transition between the composite
lossvs. frequencyresponseinwhichthemin- signal blanking level and the sync level at
imum dips are equal in power and maximum one-half horizontal line intervals. The dura-
peaks are equal in power. tion at the sync level is 3.575 ± 0.425 percent
of the horizontal line time (0.45 to 0.5 times
the horizontal sync). There are three hor-
equalization a method used in communi-
izontal lines of equalizing pulses (6 pulses)
cation systems to compensate for the channel
preceding the vertical synchronization signal
distortion introduced during signal transmis-
and 3 horizontal lines of equalizing pulses (6
sion.
pulses) following the vertical synchroniza-
tion interval. The equalizing pulse interval
equalizer a device used at the receiver repeats every field of 262.5 horizontal lines.
(typically a digital filter) that attempts to sup-
press or cancel intersymbol interference.
equalizing pulses in an encoded video
signal, a series of 2× line frequency pulses
equalizer adaptive an equalizer that auto- occurring during vertical blanking, before
matically adjusts its parameters to suppress and after the vertical synchronizing pulse.
or cancel intersymbol interference. In the Different numbers of equalizing pulses are
case of a digital filter, the parameters are the inserted into different fields to ensure that
filter coefficients, which are adapted to min- each field begins and ends at the right time
imize a cost criterion (e.g., mean-squared er- to produce proper interlace. The 2× line rate
ror). also serves to maintain horizontal synchro-
nization during vertical blanking.
equalizer decision-feedback a nonlinear
digital filter that consists of a linear prefilter equiband a complex method of chromi-
P(z) for suppressing precursor intersymbol nance signal demodulation, that does not re-
interference, and a feedback filter F(z) for quire dissimilar filters and delay equilization;
suppressing postcursor intersymbol interfer- it most frequently utilizes a bandwidth of 800
ence. KHz.

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2000 by CRC Press LLC