Calibrating array antennas based on signal energy distribution as a function of velocity

1. A radar detection method with antenna calibration, the method comprising:

forming a detection matrix from signals detected by an arrangement of receive antennas in response to chirps transmitted by an arrangement of transmit antennas, the detection matrix having multiple rows each corresponding to one of said chirps, multiple columns each corresponding to a sample of said signals, and multiple planes each corresponding to one of said receive antennas;

deriving a range matrix by performing a frequency transform on a portion of each row of the detection matrix;

extracting a slice of the range matrix having only one layer, with different rows of the slice being associated with different chirps and with different receive antennas;

deriving a velocity matrix from the extracted slice by performing a frequency transform on a portion of each column of the extracted slice;

analyzing the velocity matrix to determine a current peak width; and

adjusting, based on the current peak width, phase shifts associated with one or more of the receive antennas.

2. The radar detection method of claim 1 , wherein adjusting the phase shifts associated with one or more of the receive antennas comprises repeating said operations of forming, deriving a range matrix, extracting, deriving a velocity matrix, and analyzing to iteratively minimize the current peak width.

3. The radar detection method of claim 1 , wherein adjusting the phase shifts associated with one or more of the receive antennas comprises controlling one or more phase shifters conveying the signals from the receive antennas in said arrangement of receive antennas.

4. The radar detection method of claim 1 , wherein forming the detection matrix from signals detected by the arrangement of receive antennas comprises processing the signals to add respective phase shifts as determined by said adjusting operation.

5. The radar detection method of claim 1 , wherein forming the detection matrix from signals detected by the arrangement of receive antennas in response to chirps transmitted by the arrangement of one or more transmit antennas comprises forming the detection matrix from signals detected by the arrangement of receive antennas in response to chirps transmitted by exactly one transmit antenna.

6. The radar detection method of claim 1 , wherein extracting the slice of the range matrix comprises extracting a row from each plane.

7. The radar detection method of claim 6 , wherein extracting a row from each plane comprises extracting rows where each row corresponds to a different chirp.

8. The radar detection method of claim 1 , further comprising:

extracting a second slice of the range matrix, the second slice having one layer corresponding to a single receive antenna, with different rows of the second slice being associated with different chirps and with different transmit antennas;

deriving a second velocity matrix from the second slice by performing a frequency transform on a portion of each column of the extracted slice;

analyzing the second velocity matrix to determine a second peak width; and

adjusting, based on the second peak width, phase shifts associated with one or more of the transmit antennas.

9. A radar transceiver that comprises:

one or more transmitter circuits configured to drive a transmit antenna arrangement to emit a signal towards one or more objects, the emitted signal comprising a plurality of chirps;

an arrangement of receivers, wherein each receiver is configured to detect a signal from a receive antenna during a detection period, each receive antenna having an associated phase shift that is adjustable relative to the other receiver antennas, and wherein each of the detected signals corresponds to the emitted signal;

a processor coupled to the one or more transmitter circuits and the arrangement of receivers, wherein the processor is configured to perform a method comprising:

forming a detection matrix from the detected signals, the detection matrix having multiple rows each corresponding to one of said chirps, multiple columns each corresponding to a sample of said signals, and multiple planes each corresponding to one of said receive antennas;

deriving a range matrix by performing a frequency transform on a portion of each row of the detection matrix;

extracting a slice of the range matrix having only one layer, with different rows of the slice being associated with different chirps and with different receive antennas;

deriving a velocity matrix from the extracted slice by performing a frequency transform on a portion of each column of the extracted slice;

analyzing the velocity matrix to determine a current peak width; and

adjusting, based on the current peak width, phase shifts associated with one or more of the receive antennas.

10. The radar transceiver of claim 9 , wherein adjusting the phase shifts associated with one or more of the receive antennas comprises repeating said operations of forming, deriving a range matrix, extracting, deriving a velocity matrix, and analyzing to iteratively minimize the current peak width.

11. The radar transceiver of claim 9 , wherein adjusting the phase shifts associated with one or more of the receive antennas comprises controlling one or more phase shifters conveying the signals from the receive antennas in said arrangement of receive antennas.

12. The radar transceiver of claim 9 , wherein forming the detection matrix comprises processing the detected signals to add respective phase shifts as determined by said adjusting operation.

13. The radar transceiver of claim 9 , wherein forming the detection matrix from the detected signals comprises forming the detected signals in response to chirps transmitted by exactly one transmit antenna.

14. The radar transceiver of claim 9 , wherein extracting the slice of the range matrix comprises extracting a row from each plane.

15. The radar transceiver of claim 14 , wherein extracting a row from each plane comprises extracting rows where each row corresponds to a different chirp.

16. The radar transceiver of claim 9 , with the method performed by the processor further comprising:

extracting a second slice of the range matrix, the second slice having one layer corresponding to a single receive antenna, with different rows of the second slice being associated with different chirps and with different transmit antennas;

deriving a second velocity matrix from the second slice by performing a frequency transform on a portion of each column of the extracted slice;

analyzing the second velocity matrix to determine a second peak width; and

adjusting, based on the second peak width, phase shifts associated with one or more of the transmit antennas.

17. A system for calibrating antennas, the system comprising a non-transitory computer readable medium storing software executable by a processor, wherein the software comprises instructions to:

form a detection matrix from signals received from an arrangement of antennas in response to one or more chirps, the detection matrix having multiple rows each corresponding to one of said chirps, multiple columns each corresponding to a sample of said signals, and multiple planes each corresponding to one of said antennas;

derive a range matrix by performing a frequency transform on a portion of each row of the detection matrix;

extract a slice of the range matrix having only one layer, with different rows of the slice being associated with different chirps and with different antennas;

derive a velocity matrix from the extracted slice by performing a frequency transform on a portion of each column of the extracted slice;

analyze the velocity matrix to determine a current peak width; and

adjust, based on the current peak width, phase shifts associated with one or more of the antennas.

18. The system of claim 17 , wherein the instructions to adjust the phase shifts associated with one or more of the antennas further comprise instructions to repeat said operations of forming, deriving a range matrix, extracting, deriving a velocity matrix, and analyzing to iteratively minimize the current peak width.

19. The system of claim 17 , wherein the instructions to adjust the phase shifts associated with one or more of the antennas comprise instructions to control one or more phase shifters conveying the signals from the antennas in said arrangement of receive antennas.

20. The system of claim 17 , wherein the instructions to form the detection matrix from signals detected by the arrangement of antennas comprise instructions to process the signals to add respective phase shifts as determined by said adjusting operation.

21. The radar detection method of claim 17 , with the software further comprising instructions to:

extract a second slice of the range matrix, the second slice having one layer corresponding to a single receive antenna, with different rows of the second slice being associated with different chirps and with different transmit antennas;

derive a second velocity matrix from the second slice by performing a frequency transform on a portion of each column of the extracted slice;

analyze the second velocity matrix to determine a second peak width; and

adjust, based on the second peak width, phase shifts associated with one or more of the transmit antennas.