18WuD2x

passband • passive reflector 517
passband The continuous spectrum of frequencies
transmitted by a filter, amplifier, or similar device.
Compare STOPBAND.
passband ripple Multiple low-amplitude attenuation
variations within the passband of a filter or
tuner, resulting in a ripple pattern on the nose of
the response curve.
Relative
freq.,kHz
Passband
at 3 dB down
10
20
Ripple
requires no power for its characteristic operation).
Examples: conventional resistor, capacitor,
inductor, diode, rectifier, and fuse. Compare AC-
TIVE COMPONENT, 1.
passive comsat See PASSIVE COMMUNICATIONS
SATELLITE.
passive decoder A decoder that responds to only
one signal code, rejecting all others.
passive detection In reconnaissance, detecting a
target without betraying the location of the detector.
passive electric network See PASSIVE NET-
WORK.
passive frequency multiplier A frequency multiplier
that does not require a power supply, but
operates only from the input signal energy. Usually
consists of one or more semiconductor diodes,
sometimes in conjunction with inductors and/or
capacitors. The output signals appear at integral
multiples of the input frequency.
−6 −4 −2
+2 +4 +6
40
50
Attenuation,
dB
60
passband
passband ripple
passivation The process of growing a thin oxide
film on the surface of a planar semiconductor device
to protect the exposed junction(s) from contamination
and short circuits. See, for example,
PLANAR EPITAXIAL PASSIVATED TRANSISTOR
and PLANAR TRANSISTOR.
passive absorber A substance that reflects minimal
sound energy. Examples include acoustical
ceiling tile and thick carpeting.
passive circuit A circuit consisting entirely of nonamplifying
components, such as capacitors, resistors,
inductors, and diodes.
passive communications satellite A communications
satellite that reflects electromagnetic waves,
but does not contain a transponder; that is, it
does not receive and retransmit the signals. Also
called passive comsat. Compare ACTIVE COM-
MUNICATIONS SATELLITE.
passive component A device that is basically
static in operation (i.e., it is ordinarily incapable
of amplification or oscillation and usually
passive infrared sensor A device that detects infrared
directly, such as that given off by humans
because of their body heat. It does not generate
energy of any kind. It is used in some intrusion
detection systems.
passive mixer A signal mixer using only passive
components (diodes, nonlinear resistors, and
nonlinear reactances) (i.e., one without active
components, such as transistors). Passive mixers
introduce some loss. Compare ACTIVE
MIXER.
passive modulator A modulator using only passive
components (diodes, nonlinear resistors, and
nonlinear reactances) (i.e., one without active
components, such as transistors). Passive modulators
introduce some loss. Compare ACTIVE
MODULATOR.
passive network A network composed entirely of
passive components (i.e., one containing no generators
and providing no amplification).
passive radiator See DRONE CONE.
passive reflector A metal surface used to reflect
electromagnetic energy at ultra-high and microwave
frequencies.