GB1308392A - Monitoring signal to noise ratio - Google Patents

Abstract

1308392 Pulse radar TELEFONAKTIEBOLAGET L M ERICSSON 25 Nov 1970 [26 Nov 1969] 56165/70 Heading H4D At least one first channel F is arranged to receive a desired signal and noise in an incoming signal, at least one second channel Sp is arranged to receive a different part of the incoming signal which part contains a greater portion of the noise, automatic gain control means AKR maintains the signal plus noise in channel F constant and controls in common the signal plus noise in all channels, and the signal plus noise in a second channel is monitored; in an embodiment the incoming signal is from a pulse Doppler radar, channel F affords a range tracking strobe, channels Sp cover different fixed range "bins", and the monitoring is provided by a threshold circuits T coupled via an adder to a further threshold circuit TA with an output signal U 1 (U 1 issues when circuit TA shows that a predetermined number of thresholds T have been exceeded) which may actuate an alarm or connect range tracking to a computed probable target position, Fig. 4 (not shown). In a modification signal U 1 and a signal U 2 from a threshold circuit TB are fed as binary signals to logic gates G1, G2: a signal U 3 issues if signal-tonoise ratio is low but signal plus noise is high (i.e. there may be jamming) and a signal U 4 issues if signal-to-noise ratio is low and signal plus noise is low (i.e. a weak or no echo). Range channels F, Sp may be replaced by velocity channels.