GB723002A - Improvements in and relating to radar systems - Google Patents

Abstract

723,002. Radar; valve gating circuits. COSSOR, Ltd., A. C. July 24, 1952 [Sept. 19, 1951], No. 22016/51. Classes 40 (6) and 40 (7). [Also in Group XL (b)] The signal/noise ratio in a pulse radar receiver is increased by combining the IF echo pulses with similar pulses delayed by the recurrence period or an integral multiple thereof. As shown, the EF echo pulses at terminal 1 are applied alternately to two such loop circuits IF1, D1, A1 and IF2, D2, A2 by means of switch S1, the output from any one circuit being applied to the remaining stages R of the receiver by means of switch S2 when terminal 1 is connected to the input of the other circuit. When a P.P.I. display is employed, the period of switches S1, S2 is preferalby equal to the time taken for the radio beam to sweep through its angular width. Each loop circuit comprises an IF amplifier, a mercury delay line D and a positive feedback loop including an amplifier A. The two delay lines are mounted in a common housing and when the invention includes means for discriminating between fixed and moving targets by means of a further delay line included in stage R, all three lines may be in a common housing. The switches S1 and S2 each comprise two cathode followers whose cathodes are connected respectively to the anodes of a cathode-coupled pair of valves having a common pentode cathode impedance, Figs. 2 and 3 (not shown). The input(s) are applied to the grids of the cathode followers, the output(s) are taken from the cathodes and the switching waveform is applied to the cathode-coupled valves.