GB894618A - Radar receiver - Google Patents

Abstract

894,618. Radio direction-finding. COMPAGNIE FRANCAISE THOMSON-HOUSTON. Aug. 25, 1960 [Aug. 25, 1959], No. 29396/60. Class 40(7). Relates to a pulse radar in which the deviation of a target from an equi-signal axis defined by the overlapping directivity patterns of two aerial receiving elements 1 and 2, Fig. 1, is obtained by applying the signals from the aerials to a magic-T junction 3 to give sum and difference signals S and D which are combined in a 3 db coupler 4 to give composite signals S + jD and D + jS, the phase difference between these signals as determined by a phase discriminator being a function of D/S and hence of the required deviation. According to the present invention errors due to noise are reduced by applying one composite signal, e.g., S + jD as shown in Figs. 1 and 2, to a 90 degrees phase shifter 15 to give a signal jS-D which is combined with the other composite signal D + jS in an adding circuit 14 to give a resultant signal 2 jS which is applied together with -the first -composite signal S + jD to the phase discriminator 12 through limiters 17 and 13, the phase difference # between these two signals being less than the phase difference #/2-2# between the two compolite signals S + jD and D + jS. As shown in Fig. 1, the composite signals are converted to IF by a common local oscillator 7. Two pairs of aerials may be used to obtain azimuth and elevation deviation error signals.