Technique for compensation of transmit leakage in radar receiver

• US 20060273952A1
• Filed: 06/03/2005
• Published: 12/07/2006
• Est. Priority Date: 06/03/2005
• Status: Active Grant

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Raytheon Company (Rtx Corporation)
• Inventors: Rosen, Robert A., Krikorian, Kapriel V.
• Granted Patent: US 7,202,812 B2
• Time in Patent Office: Days
• US Class Current: 342/198
• CPC Class Codes: G01S 13/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 7/038 Feedthrough nulling circuits
• CPC Class Codes: G01S 7/352 Receivers
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

A radar system (500) radiates a radar transmit signal, has a radar signal receiver (503) and a canceller (505) for canceling leakage of the transmit signal into the radar signal receiver (503). The canceller (505) comprises a digital waveform generator (528) for generating a first digital signal converted to an analog waveform. The analog waveform is amplified after a fixed delay (534) to generate a first cancellation signal input into a circulator (504). The circulator combines the first cancellation signal with the leakage to generate a first corrected signal. A summer (507) combines the first corrected signal from the circulator with a second cancellation signal to generate a second corrected signal. The second cancellation signal is generated by a digital cancellation filter (526). The digital cancellation filter (526) has as an input the first digital signal from the digital waveform generator (528). The digital cancellation filter (526) is controlled using weight adjustments computed by an adaptive weight processor (518). The adaptive weight processor (518) samples the second corrected signal and computes the weight adjustments to optimize the second cancellation signal.

Claims

1. A radar system emitting a radar transmit signal, said radar system having a radar signal receiver for receiving reflected returns of said radar transmit signal, and a canceller for canceling leakage from said radar transmit signal into said radar signal receiver, said leakage impairing operation of said radar signal receiver, said canceller comprising:

a digital waveform generator for generating a first digital signal converted to an analog waveform, said analog waveform amplified after a fixed delay to generate a first cancellation signal input into a circulator, said circulator combining said first cancellation signal with said leakage to generate a first corrected signal

a summer for combining said first corrected signal from said circulator with a second cancellation signal to generate a second corrected signal, said second cancellation signal generated by a digital cancellation filter, said digital cancellation filter having as an input said first digital signal from said digital waveform generator, said digital cancellation filter controlled using weight adjustments computed by an adaptive weight processor, said adaptive weight processor sampling said second corrected signal and computing said weight adjustments to optimize said second cancellation signal.

2. A radar receiver as described in claim 1 wherein said second cancellation signal is sampled from an analog form to a digital representation for processing by said adaptive weight processor using an analog to digital converter.

3. A radar receiver as described in claim 2 wherein said second cancellation signal is digitally described by said digital cancellation filter and converted into analog form by a digital to analog converter.

4. A radar receiver as described in claim 3 wherein said digital cancellation filter uses a finite impulse response filter responsive to said weight adjustments.

5. A radar receiver as described in claim 3 wherein said digital cancellation filter performs a Fast Fourier Transform to generate a frequency domain signal, and wherein said weight adjustments are computed by said adaptive weight processor to operate on said frequency domain signal.

6. A method for canceling leakage in a radar system emitting a radar transmit signal, said radar system having a radar signal receiver for receiving reflected returns of said radar transmit signal, and a canceller for canceling said leakage from said radar transmit signal into said radar signal receiver, said leakage impairing operation of said radar signal receiver, said canceller comprising the steps of:

generating a first digital signal converted to an analog waveform, said-analog waveform amplified after a fixed delay to generate a first cancellation signal input into a circulator;

combining said first cancellation signal with said leakage in said circulator to generate a first corrected signal;

summing said first corrected signal from said circulator with a second cancellation signal to generate a second corrected signal, said second cancellation signal generated by a digital cancellation filter, said digital cancellation filter having as an input said first digital signal from said digital waveform generator, said digital cancellation filter controlled using weight adjustments computed by an adaptive weight processor, said adaptive weight processor sampling said second corrected signal and computing said weight adjustments to optimize said second cancellation signal.

7. A method as described in claim 6 wherein said second cancellation signal is sampled from an analog form to a digital representation for processing by said adaptive weight processor using an analog to digital converter.

8. A method as described in claim 7 wherein said second cancellation signal is digitally described by said digital cancellation filter and converted into analog form by a digital to analog converter.

9. A method as described in claim 8 wherein said digital cancellation filter uses a finite impulse response filter responsive to said weight adjustments.

10. A method as described in claim 8 wherein said digital cancellation filter performs a Fast Fourier Transform to generate a frequency domain signal, and wherein said weight adjustments are computed by said adaptive weight processor to operate on said frequency domain signal.