18WuD2x

eacon • beam parametric amplifier 67
scanning infrared laser. The robot controller determines
the distance to any given reflector by
measuring the time required for the laser beam to
return. In this way, two mirrors can allow the
robot to locate its position in two dimensions;
three mirrors can facilitate position determination
in three-dimensional space.
beacon direction finder A direction finder using a
signal received from a beacon station.
beacon receiver A receiver that is specially
adapted for the reception of beacon signals (see
BEACON, 1 and 3).
beacon station 1. A station broadcasting beacon
signals (see BEACON, 1 and 3) for direction finding,
navigation, and/or determination of radiowave
propagation conditions. 2. Sometimes, a
radar transmitting station.
beacon transmitter A transmitter specially
adapted for the transmission of beacon signals
(see BEACON, 1 and 3).
bead
1. A small ferromagnetic ring that is used as
a passive decoupling choke by slipping it over the
input power leads of a circuit or stage, or around
a coaxial transmission line. 2. A magnetic memory
element in a ferrite-core matrix.
beaded coax A low-loss, coaxial transmission line,
in which the inner conductor is separated from
the outer conductor by means of spaced dielectric
beads.
beaded support A plastic or dielectric bead that is
used to support the inner conductor of an airinsulated
transmission line of coaxial construction.
bead thermistor A thermistor consisting essentially
of a small bead of temperature-sensitive resistance
material into which two leads are inserted.
beam 1. The more-or-less narrow pattern of radiation
from a directional antenna. 2. A directional
antenna—especially a YAGI ANTENNA. 3. The
stream or cloud of electrons emitted by the cathode
in an electron tube—especially a BEAM
POWER TUBE.
beam alignment 1. The lining-up of a directional
transmitting antenna with a directional receiving
antenna for maximum signal transfer. 2. In a
beam alignment
television (TV) camera tube, the lining-up of the
electron beam so that it is perpendicular to the
target. 3. In a cathode-ray tube, the positioning of
the electron rays so that they converge properly
on the screen, regardless of the deflection path.
beam angle In the radiation from an antenna, the
direction of most intense radiation, the side limits
of which are determined by the points at which
the field strength drops to half the value in the
principal direction.
beam antenna 1. A multielement directional antenna,
consisting of a half-wave driven dipole and
one or more parasitic elements. See YAGI AN-
TENNA. 2. Any directional antenna used for
transmitting and receiving radio-frequency (RF)
signals.
beam bender 1. In a television (TV) picture tube,
the ion-trap magnet. 2. Deflection-plate correction
device or circuit.
beam bending Deflection of an electron beam by
electric or magnetic fields.
beam blanking See BLANK, 2.
beam convergence The meeting, at a shadowmask
opening, of the three electron beams in a
three-color television picture tube. See BEAM
ALIGNMENT, 3.
beam coupling A method of producing an alternating
current between two electrodes by passing a
density-modulated beam of electrons between the
electrodes. This, in effect, demodulates the electron
beam, recovering the information.
beam crossover Either of the half-power points
in the beam of a directional antenna, usually in
the horizontal plane. The reference point is considered
to be the direction of maximum radiation.
beam current The current represented by the flow
of electrons in the beam of a cathode-ray tube.
beam cutoff In an oscilloscope or television picture
tube, the complete interruption of the electron
beam, usually as a result of highly negative control-grid
bias.
beam deflector A deflection plate in an oscilloscope
tube.
beam efficiency In a cathode-ray tube, the ratio of
the number of electrons generated by the gun to
the number reaching the screen. The efficiency is
high in electromagnetic-deflection tubes and
lower in electrostatic-deflection tubes.
beam lead
In an integrated circuit, a relatively
thick and strong lead that is deposited in contact
with portions of the thin-film circuit. It provides
stouter connections than continuations of the
thin film would provide.
beam-lead isolation In an integrated circuit, reduction
of distributed capacitance and other interaction
through use of beam leads.
beam modulation See INTENSITY MODULATION.
beam parametric amplifier A PARAMETRIC AM-
PLIFIER in which the variable-reactance component
is supplied by a modulated electron beam.