Method and circuit for non-cooperative interference suppression of radio frequency signals

DETAILED DESCRIPTION A circuit for separating a radio frequency signal of interest from an interfering signal, constructed in accordance with this invention comprises a circuit for producing first and second signals, the first signal being representative of a composite signal and the second signal being representative of the envelope of the composite signal, wherein the composite signal includes the interfering signal and the signal of interest; a filter for removing selected components from the second signal to produce a filtered signal; and a first mixer for mixing the filtered signal with the first signal, to produce an output signal including a component representative of the signal of interest having a greater spectral power density than other components of the output signal.
In a first embodiment of the invention, the circuit for producing the first and second signals includes a logarithmic amplifier and detector which produces the first and second signals.
The second signal includes a plurality of components, one of the components being a cross product of the signal of interest and the interfering signal.
The filter passes a filtered signal including the cross product of the signal of interest and the interfering signal with the first signal, to the first mixer which mixes the filtered signal with the first signal to produce the output signal.
In a second embodiment of the invention, the means for producing the first and second signals includes a processor which produces the first signal and a second mixer for mixing the first signal with the composite signal to produce the second signal.
Here again, the second signal includes a plurality of components, one of the components being a cross product of the signal of interest and the interfering signal.
The second signal is filtered and the resulting filtered signal is passed to the first mixer which mixes the filtered signal with the first signal, to produce the output signal.
This invention further includes radio frequency receivers which include one of the above circuits in their intermediate frequency stage