Swept bandpass filter frequency modulated continuous wave (FMCW) receiver and related method

• US 20070081611A1
• Filed: 10/11/2005
• Published: 04/12/2007
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Integrated Systems LP (L3Harris Technologies, Inc.)
• Inventors: Fudge, Gerald, Gallatin, Boyd
• Granted Patent: US 7,496,158 B2
• Time in Patent Office: Days
• US Class Current: 375/316
• CPC Class Codes: G01S 7/021 Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
• CPC Class Codes: G01S 7/352 Receivers
• CPC Class Codes: G01S 7/358 using I/Q processing

Abstract

A swept bandpass filter for receiving frequency varying input signals is disclosed. More particularly, a swept bandpass filter frequency modulated continuous wave (FMCW) receiver and related method are disclosed that provide an efficient solution for FMCW signals. The swept bandpass architecture eliminates the need for front-end mixing circuitry and allows for sampling across one or more Nyquist zones within the swept frequency band.

Claims

1. Receive path circuitry for a receiver configured to receive frequency modulated signals, comprising:

a bandpass filter having a center frequency that is sweepable across a frequency band and having a sweep control signal as an input that is configured to determine a location of the center frequency within the frequency band; and

filter sweep control circuitry coupled to the bandpass filter to provide the sweep control signal, the filter sweep control circuitry being configured to control the sweep control signal to cause the center frequency of the bandpass filter to be swept across the frequency band.

2. The receive path circuitry of claim 1, further comprising an analog-to-digital converter (ADC) coupled to sample an output from the sweepable bandpass filter at a sampling frequency that is dependent upon a sampling clock input to the ADC.

3. The receive path circuitry of claim 2, wherein a bandwidth for the sweepable bandpass filter is less than a bandwidth for the frequency band.

4. The receive path circuitry of claim 3, wherein the sampling frequency is selected such that one or more Nyquist zones are crossed as the bandpass filter is swept across the frequency band.

5. The receive path circuitry of claim 3, wherein the sampling frequency is selected such that ten or more Nyquist zones are crossed as the bandpass filter is swept across the frequency band.

6. The receive path circuitry of claim 3, wherein the sampling frequency for the ADC is greater than two times the bandwidth for the sweepable bandpass filter but less than two times the bandwidth for the frequency band.

7. The receive path circuitry of claim 3, wherein the bandwidth for the sweepable bandpass filter is 1 to 10 percent of the bandwidth for the frequency band.

8. The receive path circuitry of claim 2, further comprising envelope detection circuitry coupled to receive digital signals from the ADC.

9. The receive path circuitry of claim 8, wherein the envelope detection circuitry comprises summation circuitry configured to sum a magnitude of a received signal over a plurality of digital samples from the ADC.

10. The receive path circuitry of claim 9, further comprising a digital demodulator and a digital low pass filter coupled between the ADC and the summation circuitry.

11. The receive path circuitry of claim 2, further comprising signal processing circuitry configured to further process the digital signals received from the ADC.

12. The receive path circuitry of claim 1, wherein the filter sweep control circuitry comprises error detection circuitry configured to determine a difference between an actual frequency for a received signal and an expected frequency for a received signal.

13. The receive path circuitry of claim 12, wherein the error detection circuitry comprises signal tracking circuitry that includes one or more additional sweepable filters that are offset in frequency or offset in time, or both.

14. The receive path circuitry of claim 12, wherein the error detection circuitry comprises signal tracking circuitry that utilizes a sinusoidal time dither signal.

15. The receive path circuitry of claim 1, wherein the sweepable bandpass filter is configured to have an adjustable bandwidth that is controlled by a bandwidth control signal.

16. The receive path circuitry of claim 1, wherein the filter sweep control circuitry is configured to sweep the center frequency for the sweepable bandpass filter to track characteristics for a desired signal to be detected.

17. The receive path circuitry of claim 16, wherein the desired signal to be detected comprises a frequency modulated radar signal.

18. The receive path circuitry of claim 16, wherein the desired signal is known to exist and its existence is being confirmed.

19. The receive path circuitry of claim 16, wherein the desired signal is not known to exist and its existence is being detected.

20. A method for receiving frequency modulated signals, comprising:

receiving a input signal having a frequency that varies within a frequency band,

determining a location for the input signal frequency as a function of time;

sweeping the center frequency of a sweepable bandpass filter across the frequency band based upon the frequency location of the input signal; and

filtering the input signal with the sweepable bandpass filter.

21. The method of claim 20, further comprising digitizing the filtered signal from the swept bandpass filter at a sampling frequency.

22. The method of claim 21, further comprising conducting additional digital signal processing on the digitized signals.

23. The method of claim of 21, wherein a bandwidth for the sweepable bandpass filter is less than a bandwidth for the frequency band.

24. The method of claim 23, wherein the sampling frequency is selected such that one or more Nyquist zones are crossed as the bandpass filter is swept across the frequency band.

25. The method of claim 23, wherein the sampling frequency is selected such that ten or more Nyquist zones are crossed as the bandpass filter is swept across the frequency band.

26. The method of claim 20, further comprising determining a tracking error to help control the sweeping of the center frequency for the sweepable bandpass filter.

27. The method of claim 20, further comprising adjusting the bandwidth of the sweepable bandpass filter.

28. The method of claim 20, further comprising adjusting the sampling frequency.

29. The method of claim 20, further comprising sweeping the center frequency for the sweepable bandpass filter to track characteristics for a desired signal to be detected.

30. The method of claim 29, wherein the desired signal to be detected comprises a frequency modulated radar signal.

31. The method of claim 29, wherein the desired signal is known to exist and its existence is being confirmed.

32. The method of claim 29, wherein the desired signal is not known to exist and its existence is being detected.