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directional coupler[də′rek·shən·əl ′kəp·lər]
a device consisting of two sections of radio waveguides. A fraction of the electromagnetic-wave energy propagating through the main waveguide is shunted into an auxiliary waveguide by using coupling links; in the auxiliary waveguide the energy is transmitted only in a specific direction. If the wave-propagation direction in the main waveguide is reversed, then the propagation direction of the shunted wave in the auxiliary waveguide will also be reversed. The unidirectional propagation in the auxiliary waveguide results from the interference of the waves that are excited in it. The superposition of these waves in one direction results in cancellation of the waves; superposition in the other direction results in the formation of the summed shunted wave. Examples of coupling links between two waveguides are (1) apertures in adjacent walls and (2) loops. Directional couplers are widely used in superhigh-frequency apparatus (frequencies from 30 megahertz to 300 gigahertz) for splitting or combining the energies of waves; for determining the wave direction, power, and phase; and for other applications.
REFERENCESLebedev, I. V. Tekhnika i pribory sverkhvysokikh chastot, vol. 1. Moscow-Leningrad, 1961.
Altman, J. Ustroistva sverkhvysokikh chastot. Moscow, 1968. (Translated from English.)
L. S. OSIPOV