18WuD2x

460 multiband receiver • multipath transmission
range of frequencies. Compare WIDEBAND RE-
CEIVER.
multicasting The use of two frequency-modulation
(FM) broadcast stations, or one FM station and
one television station, to broadcast separately the
two channels of a stereo program. The program is
picked up simultaneously with two receivers.
multicavity magnetron A magnetron whose anode
block has two or more cavities.
multicellular horn A loudspeaker in front of which
are placed rectangular cells through which the
sound passes.
multichannel Pertaining to a radio-communication
system that operates on more than one
channel at the same time. The individual channels
might contain identical information, or they
might contain different signals.
multichannel analyzer A test instrument, such as
a spectrum analyzer, that splits an input into
several channels for testing.
multichannel television sound Abbreviation,
MTS. In television broadcasting, audio transmitted
on more than one channel to provide stereo
sound to subscribers.
multichip circuit A MICROCIRCUIT composed of
interconnected active and passive chip-type components.
multichip integrated circuit An INTEGRATED
CIRCUIT composed of circuit elements on separate,
interconnected chips.
multicontact switch A switch having more than
two contacting positions.
multicoupler An impedance-matching device used
to couple several receivers to a single antenna.
multielement antenna A directive antenna having
more than one element. Such antennas include
phased arrays and parasitic arrays. Common examples
are the LOG-PERIODIC ANTENNA, the
QUAD ANTENNA, and the YAGI ANTENNA.
multiemitter transistor 1. A bipolar transistor
having more than one emitter. 2. A bipolar power
transistor having several emitters connected in
parallel in the transistor structure.
multiframe A set of frames in a signal that are adjacent
to each other in time (consecutive) and positioned
according to an alignment signal.
multigun CRT A cathode-ray tube (CRT) having
more than one electron gun.
multihop propagation Propagation of a radio wave
by several successive reflections between the
ionosphere and the surface of the earth.
multilayer circuit A circuit consisting of several
sections printed or deposited on separate layers,
which are subsequently stacked in a sandwichlike
manner.
multilayer coil A coil in which the turns of wire
are wound in several complete layers, one on top
of the other. Compare SINGLE-LAYER COIL.
multilevel password protection See HIERARCHI-
CAL PASSWORD PROTECTION.
multimedia 1. In computing, the use of video,
voice, music, electromechanical control, and/or
data transfer at the same time. Useful in education,
entertainment, business, and gaming applications.
2. The use of voice, images, data, and/or
video in a communications system or network,
and, in particular, in wireless applications. An example
is videoconferencing between a corporate
office and the user of a handheld computer
equipped with a wireless modem.
multimedia computer A personal computer designed
especially for multimedia use. It includes
a sound board, speakers, a microphone, and a
CD-ROM (compact-disk read-only memory) drive.
It often has a large-screen, high-resolution monitor
(17 inches or greater diagonal measure).
multimeter A meter that allows measurement of
different quantities (e.g., current, voltage, and resistance);
the functions are usually made available
through a selector switch.
multimode operation 1. In radio communication,
the use of two or more transmitters simultaneously,
operating in different modes [e.g., one using
single-sideband (SSB) and another using
frequency modulation (FM)]. 2. The transmission
of visible light or infrared energy through an optical
fiber in more than one mode at the same time.
3. The operation of any device in more than one of
its modes simultaneously.
multipactor A microwave switching tube capable
of operating at high power levels. Characterized
by high operating speed.
multipath cancellation A phenomenon sometimes
observed in radio-wave propagation. Separate signal
components arrive at the receiver in equal amplitude,
but opposite phase. Also see MULTIPATH
FADING and MULTIPATH RECEPTION.
multipath delay In MULTIPATH RECEPTION, the
lag between signal components arriving over different
paths.
multipath effect At a receiver, the difference in arrival
time of multipath signals. Also see MULTI-
PATH DELAY.
multipath fading In radio communication, variations
in the received signal that result from phasing
various components of the transmitted signal
that are propagated over different paths. At low,
medium, and high frequencies, this effect is usually
the result of ionospheric fluctuation. At veryhigh
and ultra-high frequencies, it could occur as
a result of changes in the state of the intervening
atmosphere or, occasionally, reflection from objects,
such as aircraft.
multipath reception Reception of a signal over
more than one path. This often results in fading
(see MULTIPATH FADING) and other undesirable
effects, such as ghosting in television reception.
multipath transmission 1. Transmission of a signal
over two or more paths. Also see MULTIPATH
RECEPTION. 2. See MULTIHOP PROPAGATION.