GB1363079A - Directional aerial systems and apparatus - Google Patents

Abstract

1363079 Aerials MARCONI CO Ltd 29 Oct 1971 [30 Oct 1970] 51625/70 Heading H4A The elements A1 to An of an aerial array are fed through quantized variable phase-shift means whereby the axis of the polar radiation diagram may be set in a desired direction. The limited number of phase steps available with quantization leads to accentuation of grating lobes, and in order to reduce this effect time varying additional small phase shifts, each not exceeding one half of one of said quantized phase steps randomly distributed across the array, are superimposed. The direction of the radiation diagram is consequently caused to move with respect to the desired direction. As described, each aerial element is fed with pulses of radio frequency from a radar unit R through four phase shifters. Thus, the element A1 is fed through the phase shifters 1P1, 2P1, 3P1, 4P1. The phase shifters 1P1, 2P1, 3P1 are controllable through a selector B1 by a computer C to introduce respective phase-shifts of 0 or #, 0 or #/2, 0 or #/4, as may be required for steering the beam. The phase-shifter 4P1 is controlled by a random or pseudo-random number generator NG to produce the aforesaid small additional phase shift. The generator NG may be controlled by the radar unit R so that there is one random number per pulse repetition period. There may also be provided in the feed to each aerial element a fixed phase shift, said fixed phase shifts being randomly distributed across the array.