Spur detection, cancellation and tracking in a wireless signal receiver
A method and device for processing spur components associated with a received wireless signal are disclosed. In one embodiment, the method includes first selecting a sub-band of a spectral band of the received signal. The selected sub-band is scanned, and a detection routine is executed to detect a spur within the scanned sub-band having a peak magnitude above a predetermined threshold. The spur frequency is determined, and the spur may be removed by a cancellation unit based on the determined frequency. The method also includes tracking the frequency of the spur to ensure continued suppression over time and under dynamic conditions.
1. A method of processing spur components associated with a wireless signal, the method comprising:
selecting a sub-band of a received signal;
determining a first Fast Fourier Transform (FFT) based, at least in part, on the selected sub-band, the first FFT including a number of frequency bins;
determining a first differential product for each frequency bin of the first FFT based, at least in part, on the first FFT and a complex conjugate of a second FFT based, at least in part, on the selected sub-band; and
determining a spur frequency based, at least in part, on the first differential product.
2. The method of claim 1 , further comprising:
cancelling a spur based on the determined spur frequency; and
tracking the determined spur frequency over time.
3. The method of claim 2 , wherein the tracking comprises:
storing initial information associated with the spur;
detecting any frequency changes associated with the spur; and
updating the initial information to reflect the detected frequency changes.
4. The method of claim 1 , wherein the first differential product is a complex product of the first FFT and the complex conjugate of the second FFT.
5. The method of claim 1 , wherein the second FFT is determined after the first FFT is determined.
6. The method of claim 1 , wherein determining the spur frequency comprises:
determining a coherent sum for each frequency bin of the first FFT based, at least in part, on the first differential product associated with each frequency bin and a second differential product associated with each frequency bin; and
selecting the spur frequency based, at least in part, on an average coherent sum and a peak coherent sum, wherein the average coherent sum is an average value of the coherent sums associated with each frequency bin and the peak coherent sum is a largest coherent sum selected from the coherent sums associated with each frequency bin.
7. The method of claim 6 , wherein the coherent sum is a complex sum of the first differential product and the second differential product, and the second differential product is based, at least in part, on the second FFT and a complex conjugate of a third FFT based, at least in part, on the selected sub-band.
8. The method of claim 7 , wherein the third FFT is determined after the first FFT and the second FFT are determined.
9. The method of claim 6 , wherein the spur frequency is associated with the peak coherent sum that is greater than a threshold.
10. The method of claim 6 , wherein the spur frequency is associated with the peak coherent sum that exceeds the average coherent sum by at least a threshold amount.
11. A receiver, comprising:
a radio frequency (RF) front end to receive a signal; and
a baseband processor to:
select a sub-band of the received signal;
determine a first Fast Fourier Transform (FFT) based, at least in part, on the selected sub-band, the first FFT including a number of frequency bins;
determine a first differential product for each frequency bin of the first FFT based, at least in part, on the first FFT, and a complex conjugate of a second FFT based, at least in part, on the selected sub-band, wherein the second FFT is determined after the first FFT is determined; and
determine a spur frequency based, at least in part, on the first differential product.
12. The receiver of claim 11 , wherein the baseband processor is to determine the frequency spur by:
determining a coherent sum for each frequency bin of the first FFT based, at least in part, on the first differential product associated with each frequency bin and a second differential product associated with each frequency bin; and
selecting the spur frequency based, at least in part, on an average coherent sum and a peak coherent sum, wherein the average coherent sum is an average value of the coherent sums associated with each frequency bin and the peak coherent sum is a largest coherent sum selected from the coherent sums associated with each frequency bin.
13. The receiver of claim 12 , wherein the coherent sum is a complex sum of the first differential product and the second differential product.
14. The receiver of claim 12 , where the spur frequency is associated with the peak coherent sum that is greater than a threshold.
15. The receiver of claim 12 , where the spur frequency is associated with the peak coherent sum that exceeds the average coherent sum by at least a threshold amount.
16. A device for processing spur components associated with a wireless signal, the device comprising:
means for selecting a sub-band of a received signal;
means for determining a first Fast Fourier Transform (FFT) based, at least in part, on the selected sub-band, the first FFT including a number of frequency bins;
means for determining a first differential product for each frequency bin of the first FFT based, at least in part, on the first FFT and a complex conjugate of a second FFT based, at least in part, on the selected sub-band, wherein the second FFT is determined after the first FFT is determined; and
means for determining a spur frequency based, at least in part, on the first differential product.
17. The device of claim 16 , further comprising:
means for cancelling a spur based on the determined spur frequency; and
means for tracking the determined spur frequency over time.
18. The device of claim 16 , wherein means for determining the spur frequency further comprises:
means for determining a coherent sum for each frequency bin of the first FFT based, at least in part, on the first differential product associated with each frequency bin and a second differential product associated with each frequency bin, wherein the coherent sum is a complex sum of the first differential product and the second differential product; and
means for selecting the spur frequency based, at least in part, on an average coherent sum and a peak coherent sum, wherein the average coherent sum is an average value of the coherent sums associated with each frequency bin and the peak coherent sum is a largest coherent sum selected from the coherent sums associated with each frequency bin.
19. The device of claim 18 , wherein the spur frequency is associated with the peak coherent sum that is greater than a threshold.
20. The device of claim 18 , wherein the spur frequency is associated with the peak coherent sum that exceeds the average coherent sum by at least a threshold amount.