Signal receiver having adaptive interfering signal cancellation

A radar system receiver, comprising:

• an antenna system having a plurality of antenna elements adapted to receive a jammer signal from both a direct path and from an indirect path, such direct and indirect paths having both differential Doppler frequency and differential time delay induced phase shifts;
• (A) a plurality of radar receiver sections, each one having a clutter filter, each one of the receiver sections being fed by a corresponding one of the antenna elements;
• (B) an adaptive jammer canceler fed by the plurality of radar receiver sections for providing a beam to suppress both the direct and indirect paths of the jamming signal, such canceler comprising:
• (a) a frequency transformation section for determining frequency components in each of a plurality of frequency sub-bands in signals received from the jammer by each one of the plurality of antenna elements over a predetermined frequency bandwidth;
• (b) a covariance matrix fed by the determined frequency sub-bands for each of the plurality of antenna elements for determining covariance matrix coefficients for each of the frequency sub-bands;
• (c) a beam forming network fed by the frequency components in each of the frequency sub-bands and the covariance matrix coefficients for forming an antenna beam for each of one of series of sub-intervals of a dwell to suppress the differential time delay phase shifts in the received jamming signal;
• and
• (d) an inverse frequency transformer and combiner for a composite output signal from the antenna beams produced during the series sub-intervals to suppress the differential Doppler frequency induced phase shifts in the received jamming signal.

A method for canceling both differential Doppler frequency and differential time delay induced phase shifts produced by direct and indirect paths of an interfering signal received by an antenna system, such antenna system having a plurality of antenna elements adapted to receive the interfering signal, comprising the steps of:

• (A) determining, for each a plurality of radar dwell sub-intervals, frequency components of signals received by each of the antenna elements in each of a plurality of frequency sub-bands;
• (B) producing, for each of the plurality of sub-intervals, a beam for each one of the determined frequency sub-bands in each sub-interval, such beam being adapted to suppress the differential time delay induced phase shifts in the received interfering signal during the sub-interval;
• and
• (C) combining the beams produced for each one of the sub-intervals into a composite beam, such composite beam being adapted to suppress the differential Doppler frequency induced phase shifts in the received interfering signal.

A method for canceling both differential Doppler frequency and differential time delay induced phase shifts produced by direct and indirect paths of an interfering signal received by an antenna system, such antenna system having a plurality of antenna elements adapted to receive the interfering signal, comprising the steps of:

• (A) determining for each a plurality of radar dwell sub-intervals:
• (a) frequency components of signals received by each of the antenna elements in each of a plurality of frequency sub-bands;
• (b) for each one of the frequency sub-bands, covariance matrix coefficients in response to the signals in such one of the frequency sub-bands received by the plurality of antenna elements;
• (B) producing, for each of the plurality of radar dwell sub-intervals, a beam for each one of the frequency sub-bands from the covariance matrix coefficients determined in each sub-interval, such beam being adapted to suppress the differential time delay induced phase shifts in the received interfering signal during the sub-interval;
• and
• (C) combining the beams produced for each one of the sub-intervals in a dwell into a composite beam for the dwell, such composite beam being adapted to suppress the differential Doppler frequency induced phase shifts in the received interfering signal.