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Development of a Beacon Antenna System with Automatically Controlled Directivity

Author: Kazel, S.
Author: Rodriguez, G.
Corporate Author: Armour Research Foundation
Date of Publication: 1962-12-07
Pages: 45
Contract: DA 11-022-ORD-4222
Original AD Number: AD-292 641

The surface of interference nulls in the combined pattern of two or more radiating elements is described. It is shown that phase-modulation of the individual radiators can reduce the severity of the nulls. If suitable phase modulation waveforms are used, the nulls are completely eliminated. Sine-wave linear, and square-wave phase modulation are compared. It is shown that sine-wave modulation creates fewer interfering sidebands than square-wave modulation. On the other hand, square-wave modulation appears useful for any number of interfering radiators, while sine-wave modulation is limited to three radiators. Switching between individual radiators is shown to give identical results as square-wave phase modulation. Experimental measurements of the radiation pattern of a 3-slot antenna on a 15 inch diameter cylinder and the effects of 180 degree phase shifts are presented. It is verified that the phase reversal interchanges maxima and minima for both linear and circularly polarized receiving antennas.

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