GB1407467A - Interference suppression circuits for radar receivers - Google Patents

Abstract

1407467 Pulse radar SIEMENS AG 6 Nov 1972 [5 Nov 1971] 51015/72 Heading H4D In a pulse radar subject to frequency-swept jamming, its effect is reduced by an arrangement incorporating two delay devices 10, 16 each producing a delay of a multiple integral of the wanted standard echo duration T. In the embodiment an M.T.I. pulse radar has a fixedecho eliminating filter 7 (which may be digital) and a rectifier 8 the video signal output from which Fig. 3a, consists for example of resultant jamming pulses S1, S2, S3 and a wanted echo N in one radar pulse recurrence period EP. A circuit 11 of threshold W produces the output Fig. 3b, and a detector 12 and delay 16 feeds inputs Fig.3c, 3d, into an "interference substitution" circuit 14 to which is applied also the delayed version Fig. 3e of Fig. 3a. A "substitution level" store is connected to circuit 14, the output from the latter being as shown in Fig. 3f. The delay in devices 10, 16 and the threshold W in device 11 may all be adjustable. The substitution level may advantageously be equal to the mean noise D.C. voltage which may also be the threshold W. The effect of the invention on a scanning beam radar is explained Figs. 4 to 6 (not shown). When C.W. jamming is experienced the invention may be disadvantageous; it is therefore arranged that under these circumstances it be switched out.