GB797367A - Improvements in or relating to pulse radar apparatus - Google Patents

Abstract

797,367. Radar. DECCA RECORD CO., Ltd. July 11, 1956 [July 11, 1955], No. 20063/55. Class 40 (7). Two pulse radar transmitters transmitting alternately on different frequencies have individual duplexers which feed the aerial via waveguide unit 23 incorporating two 3 db. branched guide directional couplers 24, 25. One arm of coupler 24 is connected to the aerial and the decoupled arm to dummy load 26; the remaining two arms are connected to two decoupled arms of coupler 25, these connections being of different effective lengths and one including adjustable phase-shifter 27. Display unit 41 may be fed with the combined received signals whilst display units 39, 40 may be fed respectively with the signals from the separate receiving channels and for this purpose the compiler video signal output is controlled from unit 31. One combined display for range stretch O to R and one for R to 2R (R corresponding to the combined recurrence frequency) may be provided. A blanking signal from unit 31 prevents undesirable bright spots on displays, the resulting fixed blind spots being avoided by varying the pulse repetition frequency of the modulator. Detector and bias control units 43, responsive respectively to the signals in the two receiving channels, bias off the associated I.F. amplifier if strong jamming signals are present. More than two transmitters may be used. If the radar coverage patterns are frequency-sensitive, appropriate choice of radiated frequencies can be made to give complementary coverage patterns.