Electrical Engineering Dictionary - part 118

multiport memory

one memory mod-

ule can be accessed by two devices simul-
taneously. One example is a video memory,
which is interfaced to a graphics co-processor
as well as the video interface of the monitor.

multiprocessor

a computer system that

has more than one internal processor capa-
ble of operating collectively on a computa-
tion. Normally associated with those systems
where the processors can access a common
main memory.

There are some additional stipulations for

a “genuine multiprocessor:”
1. It must contain two or more processors of
approximately comparable capabilities.

2. All processors share access to a common,
shared memory.

3. All processors share access to common I/O
facilities.

4. The entire system is controlled by a single
operating system (OS).

See also

multiple instruction multiple

multiprogramming

a system that allows

the processor to execute two or more pro-
grams concurrently.

multipulse converter

a three-phase con-

verter that generates more than six pulses of
DC per cycle. Multiple converters are con-
nected so that the harmonics generated by
one converter are canceled by harmonics pro-
duced by other converters, in order to reduce
the line harmonics and improve the system
power quality.

multirate finite impulse response filter
a finite impulse response (FIR) filter in which
the sampling rate is not constant.

multirate signal processing

a system in

which there is at least one change of sampling
rate. Typically an input signal is split into two
or more sub-signals each with a sampling rate
lower than the input signal.

multiresolution analysis

analysis method

that decompose a signal into components at
different resolution level; the fine to coarse
features are revealed in the fine to coarse res-
olution components.

multiresolution coding

coding schemes

that involve a multiresolution structure.

multiscale

characterized by a parameteri-

zation or decomposition in scale, as opposed
to (for example) time or frequency, in partic-
ular, an algorithm that computes or analyzes
a function or an image at multiple resolu-
tions. See also

multispectral image

an image that con-

tains information from more than one range
of frequencies. In this sense, an RGB color
image is multispectral in that it contains red,
green, and blue information. More usually,
multispectral refers to frequencies of such
number and type that it presents difficulties in
interpretation and display. Adding infrared,
ultraviolet, and radar information to an RGB
image creates a problem, since the data can-
not be simply drawn on a display. The use of
many frequencies also provides a wealth of
information sometimes needed to make fine
distinctions between regions in an image, es-
pecially in satellite imagery. See also

data

fusion

, sensor fusion.

multispeed motor

a motor that can be

operated at any one of two or more definite
speeds. For DC and induction motors, the
speed settings are practically independent of
the load, although the speed may vary with
load for certain types of motors. Multispeed
induction motors typically have two or more
sets of windings on the stator with a different
number of poles, one of which is excited at
any given time.

multistage depressed collector klystron
a specially designed klystron in which de-
creasing voltage zones cause the electron
beam to be reduced in velocity before striking

2000 by CRC Press LLC

the collector element. The effect is to reduce
the amount of heat that must be dissipated by
the device, improving operating efficiency.

multistage detection

an iterative detec-

tion strategy where increasingly more reli-
able tentative decisions are made for each it-
eration (stage) of the detection algorithm.

multistage interconnection network

interconnection network built from small
switches (often with fan-in and fan-out of 2);
if 2

modules are connected on each side of

the network, 2

n stages are required.

multistage subset decoding

in this

scheme decoding is done, first on the low-
est partition level of the signal set and then
gradually on the higher level with decoded in-
formation flow from the lower to the higher
level.

multistage vector quantization

a method

for constrained vector quantization where
several quantizers are cascaded in order to
produce a successively finer approximation
of the input vector.

Gives loss in perfor-

mance, but lower complexity than optimal
(single-stage) vector quantization.

multistage VQ

See

multistage vector

quantization

multithreaded

several instruction streams

or threads execute simultaneously.

multitone testing

a measurement tech-

nique whereby an audio system is charac-
terized by the simultaneous application of a
combination of sine waves to a device under
test.

MUSE

See

multiple sub-Nyquist encoding

MUSIC

See

multiple signal classification

mutual coupling

electromagnetic inter-

action between the elements in a phased ar-
ray antenna in which the radiation from one
element causes distortion of the current dis-
tributions or aperture field distributions of the
other elements. Feed network mutual cou-
pling occurs when the amplitude and phase
of the excitation at a feed point are altered
by the presence of reflected waves in the net-
work.

mutual exclusion

a synchronization prob-

lem requiring that two or more concurrent ac-
tivities do not simultaneously access a shared
resource.

mutual inductance

the property that ex-

ists between two current-carrying conductors
when the magnetic lines of force from one
link with those from another.

mutual information

information theo-

retic quantity representing the amount of
information given by one random variable
about another. For two discrete random vari-
ables

X and Y , with joint probability mass

function

p(x, y) and marginal probability

mass functions

p(x) and p(y), respectively,

the mutual information

I (X; Y ) is given by

I (X; Y ) =

x∈

y∈

p(x, y) log

p(x, y)

p(x)p(y)

where

X and Y are the support sets of X and

Y respectively. See also

differential entropy

relative entropy

mutually

pumped

phase

conjugator

(MPPC)

a phase conjugator in which

two phase conjugate waves are generated si-
multaneously when two beams are incident
into the phase conjugator.

With a mutu-

ally pumped phase conjugator, two incident
laser beams mutually pump the photorefrac-
tive medium and produce two phase conju-
gate waves. There are many physical mecha-
nisms that can yield mutually pumped phase
conjugation, for example, MPPC via self-
oscillation in four-wave mixing, MPPC with

2000 by CRC Press LLC

stimulated scattering, MPPC with ring res-
onator, etc.

multi-variable system. See

multi-

input–multi-output system

MVA interrupting rating

the interrupt-

ing rating of a device expressed in terms of
megavolt-amperes. The conversion between
fault volt-amps and fault current in three-
phase systems is

V A = 1.73 — operating

RMS line-line voltage — largest phase fault
current expressed in RMS symmetrical am-
peres. Power circuit breakers can have sep-
arate MVA and maximum current interrupt-
ing ratings, with adjustments when the circuit
breaker is operated below rated voltage.

MWIR laser

a laser producing light in the

midwavelength (2 – 5 micron) range, useful
in chemical species identification and other
applications.

2000 by CRC Press LLC

n-channel MOSFET

a MOSFET where

the source and drain are composed of heav-
ily doped n-type semiconductor regions on a
p-type surface. Electrons form drain-source
current when the applied gate and substrate
potentials invert the p-type surface between
them.

n-well

a region of n-type semiconductor

located at the surface of a p-type substrate
(or larger P-well) usually created in order to
contain p-channel MOSFETs.

See

numerical aperture

Nakagami fading

a general model of fad-

ing used in the modeling of radio communi-
cation channels, introduced by Nakagami in
1960, which includes as a special case the
Rayleigh model of fading.

NaN

acronym for not a number. Used in

IEEE floating-point representations to des-
ignate values that are not infinity or zero or
within the bounds of the representation.

NAND gate

a logic circuit that performs

the operation equivalent to the AND gate fol-
lowed by the inverter. The output of a NAND
gate is low only if all inputs are high.

nano

prefix for metric unit that indicates

division by one billion.

nanocell

cell of radius up to 10 m. See

also

cell

nanoelectronics

a future integrated cir-

cuit technology characterized by minimum
lateral feature sizes in the range 1 – 100
nanometers. Also pertains to ICs utilizing
quantum devices.

nanolithography

Lithography involving

the printing of ultra-small features, typically
on the order of nanometers in size.

nanometer

a metric measure of distance

equivalent to one billionth of a meter.

narrow band

referring to a bandwidth of

300 hertz or less.

narrow-band fading

fading in which the

communication channel amplitude can be as-
sumed independent of fading. Occurs when
the transmitted signal bandwidth is consid-
erably less than the coherence bandwidth of
the channel.

narrow-band filter

narrow-band filters

are those which pass signals undistorted in
one or a set of narrow frequency bands and
attenuate or totally eliminate signals in the
remaining frequency bands.

narrow band FM

frequency modulation

scheme where the ratio of peak frequency de-
viation to the frequency of the modulating
signal is smaller than 0.2.

narrow-band interference (NBI)

in-

terference from a source that occupies a
smaller bandwidth that the desired signal.
One example is a single sinusoid (or a
narrow-band communication system) inter-
fering with a wide-band system, possibly a
spread-spectrum system.

nasal

a sonorant phone that is produced

with the vocal tract closed and the velum
open. Nasals have a formant-like spectrum,
but much information is carried out during
the transition for the opening of the velum.
Hence, the design of very effective auto-
matic systems for the recognition of partic-
ular nasals (e.g.,

/m/, /n/) must take into

account these brief transitions.

Nash equilibrium

a noncooperative equi-

librium in nonzero-sum games defined by an
outcome for each player that cannot be im-

2000 by CRC Press LLC

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