Signal receiver having adaptive interfering signal cancellation

• US 6,650,271 B1
• Filed: 11/24/1997
• Issued: 11/18/2003
• Est. Priority Date: 11/24/1997
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Seghezzi, Edward A., Simone, Joseph D.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/979,442
• Time in Patent Office: 2,185 Days
• Field of Search: 342/16, 342/17, 342/18, 342/19, 342/39, 342/98, 342/99, 342/100, 342/101, 342/102, 342/159, 342/162, 342/148, 342/192, 342/194, 342/195, 342/196
• US Class Current: 342/16
• CPC Class Codes: G01S 7/2883 using FFT processing
• CPC Class Codes: G01S 7/2923 based on data belonging to a number of consecutive radar periods
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures

Abstract

A radar system receiver having an antenna system adapted to receive a jammer signal from both a direct path and from an indirect path. The direct and indirect paths have both differential Doppler frequency and differential time delay induced phase shifts. The antenna system includes a plurality of antenna elements. A plurality of radar receiver sections, each one having a clutter filter, is provided. Each one of the receiver sections is fed by a corresponding one of the antenna elements. An adaptive jammer canceler is fed by the plurality of radar receiver sections for providing a beam forming network to suppress both the direct and indirect paths of the jamming signal. The adaptive canceler separates each of a plurality of radar dwells into a plurality of sub-intervals, determines frequency components in each of the sub-intervals over a predetermined frequency bandwidth, forms a plurality of frequency sub-band beam forming networks from the frequency components for each of a corresponding one of the sub-intervals to suppress the differential time delay phase shifts in the received jamming signal, and produces a composite output signal from the plurality of frequency sub-band beam forming networks and the plurality of subintervals to suppress the differential Doppler frequency induced phase shifts in the received jamming signal.

Claims

1. A receiver, comprising:

a plurality of elements adapted to receive an interfering 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 plurality of receiver sections, each one of the receiver sections being fed by a corresponding one of the elements;

an adaptive interfering signal canceler fed by the plurality of receiver sections for providing a beam forming network to suppress both the direct and indirect paths of the interfering signal, such canceler separating the received signal into a plurality of sub-intervals, determining frequency components in each of the sub-intervals over a predetermined frequency bandwidth, forming a plurality of frequency sub-band beam forming networks from the frequency components for each of a corresponding one of the sub-intervals to suppress the differential time delay phase shifts in the received interfering signal, and producing a composite output signal from the plurality of frequency sub-band beam forming networks over the plurality of sub-intervals to suppress the differential Doppler frequency induced phase shifts in the received interfering signal.

2. 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.

3. 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.

4. 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.