DOPINGThe process of adding impurities to semiconductor crystals to increase the number of free
charges that can be moved by an external, applied voltage. Doping produces N-type or P-type material
DOPPLER EFFECT(1) The apparent change in frequency or pitch when a sound source moves either
toward or away from a listener . (2) In radar, the change in frequency of a received signal caused by
the relative motion between the radar and the target .
DOPPLER FREQUENCYThe difference between transmitted and reflected frequencies; caused by the
Doppler effect .
DOUBLE-MODINGIn a transmitter output tube, the abrupt and random change from one frequency to
DOUBLE NEGATIVE LAWIn Boolean algebra, the law which states that the complement of a
complement is the equivalent of the original term .
DOUBLE RECEIVERA fine and coarse synchro receiver enclosed in a common housing with a two-
shaft output (one shaft inside the other) .
DOUBLETAnother name for the dipole antenna .
DOUBLING UPThis is a type of two-equipment installation where one unit can be substituted for
another in the event of failure .
DOWN LINKThe frequency used to transmit an amplified signal from a satellite or other craft back to
DRIFT SPACEIn an electron, a region free of external fields in which relative electron position depends
on velocity .
DRIVEN ARRAYAn array in which all of the elements are driven .
DRIVEN ELEMENTThe element of an antenna connected directly to the transmission line .
DRIVERThe final stage of amplification .
DRUM-TYPE ARMATUREAn efficient, popular type of armature designed so that the entire length of
the winding is cutting the field at all times. Most wound armatures are of this type .
DRY-AIR SYSTEMProvides dehumidified air for electronic equipment that is moisture critical .
DRY CELLAn electrical cell in which the electrolyte is not a liquid. In most dry cells the electrolyte is in
the form of a paste .
DUAL-GATE MOSFETA two-gate MOSFET in which either gate can control the conductor
independently, a fact which makes this MOSFET very versatile .
DUAL IN-LINE PACKAGE (DIP)IC package having two parallel rows of preformed leads .
DUCTILEEasily drawn out (as to form filaments or wires) .
DUCTINGTrapping of an RF wave between two layers of the earth's atmosphere or between an
atmospheric layer and the earth .