System and method for reducing a radar interference signal

• US 7,403,153 B2
• Filed: 12/15/2004
• Issued: 07/22/2008
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Valeo Radar Systems, Inc. (Valeo SE)
• Original Assignee: Valeo Raytheon Systems, Inc. (Valeo SE)
• Inventors: Kelly, Thomas M. Jr., Aeder, R. Gregory, Woodington, Walter Gordon
• Primary Examiner(s): Black; Thomas G.
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US11/012,679
• Publication Number:
  US 20060125682A1
• Time in Patent Office: 1,315 Days
• Field of Search: 342/159, 342128-132, 375/346, 375349-350
• US Class Current: 342/159
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/354 Extracting wanted echo-signals Doppler systems G01S13/50
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing

Abstract

A system and method are provided to reduce an interfering signal in a radar return signal for a frequency modulated continuous wave (FMCW) radar. Once the interfering signal is detected, an extent of the interfering signal is determined and the interfering signal is removed from the radar return signal. This allows the radar to detect a target in the presence of the interfering signal. The system and method can benefit any FMCW radar that is within the range of an interfering radar source (e.g. another FMCW radar, a police radar gun, a pulse radar, etc.) operating in the same frequency band as the FMCW radar.

Claims

1. A method of processing a radar return signal, comprising:

generating a first array having time sample elements with respective time sample values associated with the radar return signal;

processing the first array to detect an interfering signal in the time sample elements, wherein the processing comprises;

generating a second array having second array elements with respective second array values associated with the time sample values, wherein the second array values comprise at least one of slope values generated from differences of the time sample values, higher order derivative values generated from differences of differences of the time sample values, or power values, each power value generated by squaring a respective out of the time sample values;

determining, from among the second array elements, second array elements indicative of the interfering signal, wherein the determining comprises;

generating at least one threshold associated with the second array values;

comparing the second array values with the at least one threshold; and

detecting that the interfering signal exists if at least a selected number of the second array values exceed the at least one threshold; and

identifying time sample elements in the first array indicative of the interfering signal by one-to-one mapping at least one of the second array elements indicative of the interfering signal to a corresponding at least one of the time sample elements, wherein the mapping does not alter the time sample values of the first array; and

removing, from the same first array having the same time sample elements and the same time sample values, the identified time sample elements indicative of the interfering signal.

2. The method of claim 1, wherein the generating at least one threshold comprises generating at least one of a first threshold related to a maximum expected second array value or a second threshold related to a mean value of the second array values.

3. The method of claim 2, wherein the comparing the second array values with the at least one threshold comprises comparing the second array values with at least one of the first threshold or the second threshold.

4. The method of claim 2, wherein the detecting that the interfering signal exists comprises identifying if at least the selected number of second array values exceed at least one of the first threshold or the second threshold.

5. The method of claim 1, wherein the associating the second array values indicative of the interfering signal with the time samples comprises:

identifying a lower second array sample limit associated with a selected one of the selected number of second array values exceeding the at least one threshold;

identifying an upper second array sample limit associated with another selected one of the selected number of second array values exceeding the at least one threshold;

selecting a first sample guard band value;

selecting a second sample guard band value;

subtracting the first sample guard band value from the lower second array sample limit to provide an interfering signal lower second array sample extent;

adding the second sample guard band value to the upper second array sample limit to provide an interfering signal upper second array sample extent; and

identifying at least one of an interfering signal lower time sample extent or an interfering signal upper time sample extent in accordance with the interfering signal lower second array sample extent or the interfering signal upper second array sample extent, respectively.

6. The method of claim 5, wherein the removing, from the time samples, the time samples indicative of the interfering signal comprises selecting a group of contiguous time samples excluding time samples between the interfering signal lower time sample extent and the interfering signal upper time sample extent.

7. The method of claim 6, wherein the removing, from the time samples, the time samples indicative of the interfering signal further includes padding the group of contiguous time samples.

8. The method of claim 5, wherein the removing, from the time samples, the time samples indicative of the interfering signal comprises:

generating a weighting function in accordance with the interfering signal lower time sample extent and the interfering signal upper time sample extent; and

applying the weighting function to the time samples.

9. The method of claim 1, wherein the second array values comprise at least one of slope values generated from differences of the time sample values or higher order derivative values generated from differences of differences of the time sample values.

10. The method of claim 1, wherein the generating at least one threshold comprises generating a first threshold related to a maximum expected second array value and a second threshold related to a mean value of the second array values, and wherein the detecting that the interfering signal exists comprises identifying if at least the selected number of second array values exceed both the first threshold and the second threshold.

11. The method of claim 1, further comprising,

transmitting a chirp transmit signal;

receiving the radar return signal as a chirp return signal in response to the transmitting;

converting the radar return signal to an electronic return signal;

mixing the electronic return signal with a signal generated by a chirp oscillator to provide a downconverted signal; and

sampling the downconverted signal to provide the first array.

12. The method of claim 1, wherein the removing comprises altering values of the identified time sample elements so as to be equal to predetermined values.

13. A method of detecting an interfering signal in a radar return signal, the method comprising:

generating a first array having time sample elements with respective time sample values associated with the radar return signal;

generating a second array having second array having second array elements with respective second array values associated with the time sample values, wherein the second array values comprise at least one of slope values generated from differences of the time sample values or higher order derivative values generated from differences of differences of the time sample values;

generating at least one threshold associated with the second array values;

comparing the second array values with the at least one threshold; and

detecting that the interfering signal exists if at least a selected number of the second array values exceed the at least one threshold identifying time sample elements in the first array indicative of the interfering signal by one-to-one mapping at least one of the second array elements indicative of the interfering signal to a corresponding at least one of the time sample elements, wherein the mapping does not alter the time sample values of the first array.

14. The method of claim 13, wherein the generating at least one threshold comprises generating at least one of a first threshold related to a maximum expected second array value or a second threshold related to a mean value of the second array values.

15. The method of claim 13, wherein the generating the at least one threshold comprises generating both a first threshold related to a maximum expected second array value and a second threshold related to a mean value of the second array values, wherein the comparing comprises comparing the second array value to both the first and second thresholds, and wherein the detecting comprises detecting that the interference signal exists if at least the selected number of the second array values exceed both the first and second thresholds.

16. The method of claim 13, further comprising:

transmitting a chirp transmit signal;

receiving the radar return signal as a chirp return signal in response to the transmitting;

converting the radar return signal to an electronic return signal;

mixing the electronic return signal with a signal generated by a chirp oscillator to provide a downconverted signal; and

sampling the downconverted signal to provide the first array.

17. System to process a radar return signal, comprising:

a radar receiving module adapted to provide a downconverted signal;

a radar signal sampling module coupled to the radar receiving module and adapted to provide a first array having time sample elements with respective time sample values associated with the downconverted signal;

an interference detector coupled to receive the first array and adapted to detect an interfering signal in the time sample elements, wherein the interference detector includes an array processor adapted to generate a second array having second array elements with respective second array values associated with the time sample values, wherein the second array values comprise at least one of slope values generated from differences of the time sample values, higher order derivative values generated from differences of differences of the time sample values, or power values, each power value generated by squaring a respective one of the time sample values wherein the array processor is further adapted to generate at least one threshold associated with the second array values, to compare the second array values with the at least one threshold, and to determine that the interfering signal exists in response to at least a selected number of the second array values exceeding the at least one threshold;

an interference extent processor coupled to the interference detector and adapted to identify time sample elements in the first array indicative of the interfering signal by determining, from among the second array elements, second array elements indicative of the interfering signal, and adapted to one to one map at least one of the second array elements indicative of the interfering signal to a corresponding at least one of the time sample elements, wherein the mapping does not alter the time sample values of the first array; and

an interference removal processor coupled to the interference extent processor and adapted to remove, from the same first array having the same time sample elements and the same time sample values, the identified time sample elements associated with the interfering signal.

18. The system of claim 17, wherein the array processor is further adapted to generate at least one threshold associated with the second array values, including at least one of a first threshold related to a maximum expected second array value, or a second threshold related to a mean of the second array values, wherein the interference detector is adapted to compare the second array values with at least one of the first threshold or the second threshold.

19. The system of claim 18, wherein the interference detector further includes a threshold processor adapted to detect that the interfering signal exists if at least a selected number of second array values exceed at least one of the first threshold or the second threshold.

20. The system of claim 17, wherein the interference extent processor includes a limit processor adapted to identify a lower second array sample limit associated with a selected one of the selected number of second array values exceeding the at least one threshold, to identify an upper second array sample limit associated with another selected one of the selected number of second array values exceeding the at least one threshold, to select a first sample guard band value, to select a second sample guard band value, to subtract the first sample guard band value from the lower second array sample limit to provide an interfering signal lower second array sample extent, to add the second sample guard band value to the upper second array sample limit to provide an interfering signal upper second array sample extent, and to identify at least one of an interfering signal lower time sample extent or an interfering signal upper time sample extent in accordance with the interfering signal lower second array sample extent or the interfering signal upper second array sample extent, respectively.

21. The system of claim 20, wherein the interference removal processor includes a selection processor adapted to select a group of contiguous time sample elements excluding time sample elements between the interfering signal lower time sample extent and the interfering signal upper time sample extent.

22. The system of claim 20, wherein the interference removal processor includes a weighting processor adapted to generate a weighting function in accordance with the interfering signal lower time sample extent and the interfering signal upper time sample extent and to apply the weighting function to the time sample values.

23. The system of claim 17, wherein the second array values comprise at least one of slope values generated from differences of the time sample values or higher order derivative values generated from differences of differences of the time sample values.

24. The system of claim 17, wherein the at least one threshold includes, including:

a first threshold related to a maximum expected second array value; and

a second threshold related to a mean of the second array values, and wherein the interference detector is adapted to compare the second array values with both the first threshold and the second threshold, and wherein the interference detector includes a threshold processor adapted to detect that the interfering signal exists if at least a selected number of second array values exceed both the first threshold and the second threshold.

25. The system of claim 17, wherein radar the receiving module is further adapted to receive a chirp signal and to mix the chirp signal with a signal generated by a chirp oscillator to provide the downconverted signal.

26. The system of claim 17, wherein the interference removal processor is adapted to remove, from the same first array having the same time sample elements and the same time sample values, the identified time sample elements associated with the interfering signal by altering the values of the identified time sample elements so as to be equal to predetermined values.