AI-1
APPENDIX I
GLOSSARY
APERTURE—See slot.
BOUNDARY CONDITIONS—The two conditions that the E-field and H-field within a
waveguide must meet before energy will travel down the waveguide. The E-field must be
perpendicular to the walls and the H-field must be in closed loops, parallel to the walls, and
perpendicular to the E-field.
BEARING—An angular measurement that indicates the direction of an object in degrees from
true north. Also called azimuth.
BUNCHER CAVITY—The input resonant cavity in a conventional klystron oscillator.
BUNCHER GRID—In a velocity-modulated tube, the grid which concentrates the electrons in
the electron beam into bunches.
CATCHER GRID—In a velocity-modulated tube, a grid on which the spaced electron groups
induce a signal. The output of the tube is taken from the catcher grid.
CAVITY RESONATOR—A space totally enclosed by a metallic conductor and supplied with
energy in such a way that it becomes a source of electromagnetic oscillations. The size and
shape of the enclosure determine the resonant frequency.
CHOKE JOINT—A joint between two sections of waveguide that provides a good electrical
connection without power losses or reflections.
COOKIE-CUTTER TUNER—Mechanical magnetron tuning device that changes the frequency
by changing the capacitance of the anode cavities.
COPPER LOSS—Power loss in copper conductors caused by the internal resistance of the
conductors to current flow. Also called I2R loss.
CROWN-OF-THORNS TUNER—See Sprocket Tuner.
CUTOFF FREQUENCY—The frequency at which the attenuation of a waveguide increases
sharply and below which a traveling wave in a given mode cannot be maintained. A
frequency with a half wavelength that is greater than the wide dimension of a waveguide.
DIELECTRIC CONSTANT—The ratio of a given dielectric to the dielectric value of a
vacuum.
DIELECTRIC LOSSES—The electric energy that is converted to heat in a dielectric subjected
to a varying electric field.
DIRECTIONAL COUPLER—A device that samples the energy traveling in a waveguide for
use in another circuit.
DIRECTIVITY—The narrowness of the radiated beam from an antenna.
