GB1504517A - Signal separation arrangements - Google Patents

Abstract

1504517 Reducing interference PLESSEY CO Ltd 26 March 1975 [5 April 1974 27 Sept 1974] 15127/74 and 42143/74 Heading H4L In a circuit arrangement for separating out a desired signal from a channel containing both desired and undesired components, there is added to the signal originally in the channel to form a modified signal a signal from a further channel, containing at least the undesired component, the frequency and phase of the added signal being adjusted in dependence on the correlation between the modified signal and the added signal, to reduce the proportion of the undesired component from the modified signal. Band pass filtering arrangements ensure that the correlator works in (a) frequency band(s) wherein the wanted signal is absent the undesired component predominates. The undesired component may include a tracer signal passed by the filtering arrangements. Alternatively, a gating arrangement may ensure that the correlator means receives signals only when the unwanted signal predominates. As shown the modified signal is formed, at the output of coupler 22, at r.f., local oscillator 31 mixers 29, 30 and filters 32, 33 ensuring that the correlator functions at i.f., bandstop filters 24, 25 excluding the spectral range containing the output signal provided at 28 from the correlated signals. The arrangement may operate at r.f., in which case filters 24, 25 are tunable. Main and auxiliary aerials (1, 2), Fig. 1 (not shown) may receive the desired and undesired components, or the aerial (2) may receive only the undesired components, or the undesired signal may emanate from a co-sited transmitter and be conductively coupled to the auxiliary input. The arrangement may comprise a double superhet arrangement, Fig. 3 (not shown), the correlator operating at an i.f. to control the addition of the desired and interference signals at r.f., the separated, desired signal being fed at r.f. to a receiver (not shown). Separating out a plurality of desired signals, Figs. 4, 5 (not shown). Inputs equal in number to the number of independent, desired, signals may each receive a mixture of all the signals, and, by coupling into each channel phase and amplitude adjusted versions of the signals in the other channels, each phase and amplitude being adjusted in dependence on the correlation between band-pass filtered signals derived from the corresponding pair of channels, substantially pure desired signals may be derived. Alternatively, one channel may be separated out leaving an admixture of all remaining channels, the process being iterated with a stepwise decreasing number of channels until all channels are separated. The undesired components may comprise a broadband jamming signal.