AI-4
METALLIC INSULATOR—A shorted quarter-wave section of transmission line.
MICROWAVE REGION—The portion of the electromagnetic spectrum from 1,000 megahertz
to 100,000 megahertz.
MODULATOR—A device that produces modulation; i.e., varies the amplitude, frequency, or
phase of an ac signal.
NEGATIVE-RESISTANCE ELEMENT—A component having an operating region in which
an increase in the applied voltage increases the resistance and produces a proportional
decrease in current. Examples include tunnel diodes and silicon unijunction transistors.
NONDEGENERATIVE-PARAMETRIC AMPLIFIER—A parametric amplifier that uses a
pump signal frequency that is higher than twice the frequency of the input signal.
PHASE SHIFTER—A device used to change the phase relationship between two ac signals.
POWER GAIN—The ratio of the radiated power of an antenna compared to the output power of
a standard antenna. A measure of antenna efficiency usually expressed in decibels. Also
referred to as POWER RATIO.
POWER RATIO—See Power Gain.
PROBE—A metal rod that projects into, but is insulated from, a waveguide or resonant cavity
and used to inject or extract energy.
PUMP—Electrical source of the energy required to vary the capacitance of a parametric
amplifier.
RANGE—Distance, as measured from a point of reference, such as a radar, to a target or other
object.
REACTANCE AMPLIFIER—A low-noise amplifier that uses a nonlinear variable reactance as
the active element instead of a variable resistance. Also called a parametric amplifier.
RECIPROCITY—The ability of an antenna to both transmit and receive electromagnetic
energy.
REFLEX KLYSTRON—A klystron with a reflector (repeller) electrode in place of a second
resonant cavity to redirect the velocity-modulated electrons back through the cavity which
produced the modulation.
REFRACTIVE INDEX—The ratio of the phase velocity of a wave in free space to the phase
velocity of the wave in a given substance (dielectric).
REPELLER—Sometimes called a reflector. An electrode in a reflex klystron with the primary
purpose of reversing the direction of the electron beam.
ROTATING JOINT—A joint that permits one section of a transmission line or waveguide to
rotate continuously with respect to another while passing energy through the joint. Also
called a rotary coupler.
