18WuD2x

542 polarization diversity • polarizing filter
polarization diversity A form of reception in
which two separate receivers, tuned to the same
signal, are connected to independent antennas.
One antenna is vertically polarized and the other
is horizontally polarized. The result is a reduction
in fading caused by ionospheric effects on the polarization
of the incoming signal.
Vertical
antenna
Both antennas
at least λ/2 apart
Horizontal antenna
polarized plug A plug that can be inserted into a
socket or receptacle in only one way to ensure
safe and foolproof operation.
Larger pin
is ground
polarized plug
RX
polarization diversity
polarization error In the operation of a loop antenna
(e.g., that of a direction finder), null error
caused by waves arriving with polarization opposite
that of the loop (thus, vertically polarized
waves at a horizontal-plane loop, and vice versa).
polarization fading In radio reception, a form of
fading that results from changes in the polarization
of the arriving signal with respect to the receiving
antenna. When the polarization of the
arriving signal coincides with that of the receiving
antenna, the received signal strength is maximum.
When the received-signal polarization is at
right angles to the receiving antenna, the signal
strength is minimum.
polarization modulation A method of impressing
information on a signal by changing the polarization
of the radiated electromagnetic field.
polarization selectivity For a photoemissive surface,
the condition in which the ratio of photocurrents
for two different angles of plane polarization
of the light incident to the surface differs from the
ratio of the corresponding amounts of light
absorbed by the surface. Also see PHOTO-
EMISSION; PHOTOEMISSIVE MATERIAL; and
POLARIZATION, 3.
polarized capacitor A conventional electrolytic capacitor,
so called because one particular terminal
must be connected to the more positive of the two
connection points. Compare NONPOLARIZED
ELECTROLYTIC CAPACITOR.
polarized light Visible light waves whose electric
lines of flux are confined more or less to a single
plane. This effect can be obtained via filtering; it
also occurs naturally under certain conditions.
Scattered sunlight is polarized to some extent by
the atmosphere. Light is polarized to some extent
when it reflects from a plane surface. Also see PO-
LARIZING FILTER.
polarized power plug A polarized plug for connection
of equipment to an alternating-current utility
power source.
polarized reactor A saturable reactor in which the
lines of flux produced in the three-leg core by the
coils on the two outer legs are added in the center
leg. Consequently, the flux can reinforce or oppose
the controlling current in the coil on the
center leg, depending on the direction of the current.
Compare NONPOLARIZED REACTOR.
polarized receptacle A receptacle constructed so
that it can receive a plug in only one way, thus
preventing incorrect connections.
Larger pin
socket is
ground
polarized receptacle
polarized relay A relay actuated by one polarity of
direct current, or by one particular phase of alternating
current. Such a relay sometimes contains
an armature-centering permanent magnet.
polarized socket See POLARIZED RECEPTACLE.
polarized X rays X-ray waves whose electric lines
of flux are more or less oriented in a specific
plane, as when they are scattered by carbon
blocks. See, for illustration, POLARIZATION, 3
and POLARIZED LIGHT.
polarizing filter A light filter that consists essentially
of microscopic heraphathite plastic plate.
The plate can be rotated to cause light passing