Online radar phase calibration through static environment measurements

1. An apparatus comprising:

an antenna array comprising a plurality of antennas to receive a plurality of reflected radar signals reflected by a plurality of objects responsive to a transmitted radar signal, wherein the plurality of reflected radar signals includes a first reflected radar signal reflected by a first object, a second reflected radar signal reflected by a second object, and a third reflected radar signal reflected by a third object;

a doppler measurement module to:

determine, for the first reflected radar signal, a first doppler measurement indicating a velocity component based on a comparison of the first reflected radar signal to the transmitted radar signal;

determine, for the second reflected radar signal, a second doppler measurement indicating a second velocity component based on a comparison of the second reflected radar signal to the transmitted radar signal; and

determine, for the third reflected radar signal, a third doppler measurement indicating a third velocity component based on a comparison of the third reflected radar signal to the transmitted radar signal;

a phase offset measurement module to:

determine a first phase offset of the first reflected radar signal received at a first antenna of the plurality of antennas relative to a phase of the first reflected radar signal received at a reference antenna of the plurality of antennas;

determine a second phase offset of the second reflected radar signal received at the first antenna relative to a phase of the second reflected radar signal received at the reference antenna; and

determine a third phase offset of the third reflected radar signal received at the first antenna relative to a phase of the third reflected radar signal received at the reference antenna; and

a phase offset calibration module to determine, for the first antenna, a phase offset calibration error based on:

a first phase offset calibration error for the first object based on the first doppler measurement and the first phase offset;

a second phase offset calibration error for the second object based on the second doppler measurement and the second phase offset; and

a third phase offset calibration error for the third object based on the third doppler measurement and the third phase offset.

2. The apparatus of claim 1 , wherein the phase offset calibration module is to determine, for each object of the plurality of objects, a phase offset calibration error specific to the respective object based on a doppler measurement and a phase offset measurement determined from a reflected radar signal from the respective object.

3. The apparatus of claim 2 , wherein the phase offset calibration error for the first antenna is a mean of the phase offset calibration errors determined for each object of the plurality of objects.

4. The apparatus of claim 2 , wherein the phase offset calibration error for the first antenna is a trimmed mean of the phase offset calibration errors determined for each object of the plurality of objects.

5. The apparatus of claim 2 , wherein the phase offset calibration error for the first antenna is a median of the phase offset calibration errors determined for each object of the plurality of objects.

6. The apparatus of claim 2 , wherein the plurality of objects includes stationary objects and moving objects.

7. The apparatus of claim 1 , wherein:

the phase offset measurement module is to determine a second phase offset of the first reflected radar signal received at a second antenna of the plurality of antennas relative to the phase of the first reflected radar signal received at the reference antenna of the plurality of antennas; and

the phase offset calibration module is to determine, for the second antenna, a phase offset calibration error based on the first doppler measurement and the second phase offset of the first reflected radar signal received at the second antenna.

8. The apparatus of claim 1 , further comprising an angle determination module to calculate an angle indicating a position of the first object that reflected the first reflected radar signal, the angle calculation based in part on a corrected phase offset calculated by subtracting the phase offset calibration error for the first antenna from the first phase offset.

9. The apparatus of claim 1 , wherein the phase offset calibration error for the first antenna is further based on a speed of a vehicle comprising the antenna array.

10. The apparatus of claim 1 , wherein the phase offset calibration error for the first antenna is further based on a distance between the first antenna and the reference antenna.

11. A method comprising:

receiving, by a plurality of antennas, a plurality of reflected radar signals reflected by a plurality of objects responsive to a transmitted radar signal, wherein the plurality of reflected radar signals includes a first reflected radar signal reflected by a first object, a second reflected radar signal reflected by a second object, and a third reflected radar signal reflected by a third object;

determining, for the first reflected radar signal, a first doppler measurement indicating a velocity component based on a comparison of the first reflected radar signal to the transmitted radar signal;

determining, for the second reflected radar signal, a second doppler measurement indicating a second velocity component based on a comparison of the second reflected radar signal to the transmitted radar signal;

determining, for the third reflected radar signal, a third doppler measurement indicating a third velocity component based on a comparison of the third reflected radar signal to the transmitted radar signal;

determining a first phase offset of the first reflected radar signal received at a first antenna of the plurality of antennas relative to a phase of the first reflected radar signal received at a reference antenna of the plurality of antennas;

determining a second phase offset of the second reflected radar signal received at the first antenna relative to a phase of the second reflected radar signal received at the reference antenna;

determining a third phase offset of the third reflected radar signal received at the first antenna relative to a phase of the third reflected radar signal received at the reference antenna; and

determining, for the first antenna, a phase offset calibration error based on:

a first phase offset calibration error for the first object based on the first doppler measurement and the first phase offset;

a second phase offset calibration error for the second object based on the second doppler measurement and the second phase offset; and

a third phase offset calibration error for the third object based on the third doppler measurement and the third phase offset.

12. The method of claim 11 , further comprising determining, for each object of the plurality of objects, a phase offset calibration error specific to the respective object based on a doppler measurement and a phase offset measurement determined from a reflected radar signal from the respective object.

13. The method of claim 11 , further comprising:

determining a second phase offset of the first reflected radar signal received at a second antenna of the plurality of antennas relative to the phase of the first reflected radar signal received at the reference antenna of the plurality of antennas; and

determining, for the second antenna, a phase offset calibration error based on the first doppler measurement and the second phase offset of the first reflected radar signal received at the second antenna.

14. The method of claim 11 , further comprising calculating an angle indicating a position of the first object that reflected the first reflected radar signal, the angle calculation based in part on a corrected phase offset calculated by subtracting the phase offset calibration error for the first antenna from the first phase offset.

15. The method of claim 11 , further comprising calculating a speed of a vehicle comprising the plurality of antennas and determining the phase offset calibration error for the first antenna based on the speed of the vehicle.

16. A vehicle comprising:

a processor;

drive controls comprising an accelerator and a steering system; and

a radar system to:

receive, by a plurality of antennas, a plurality of reflected radar signals reflected by a plurality of objects responsive to a transmitted radar signal, wherein the plurality of reflected radar signals includes a first reflected radar signal reflected by a first object, a second reflected radar signal reflected by a second object, and a third reflected radar signal reflected by a third object;

determine, for the first reflected radar signal, a first doppler measurement indicating a velocity component based on a comparison of the first reflected radar signal to the transmitted radar signal;

determine, for the second reflected radar signal, a second doppler measurement indicating a second velocity component based on a comparison of the second reflected radar signal to the transmitted radar signal;

determine, for the third reflected radar signal, a third doppler measurement indicating a third velocity component based on a comparison of the third reflected radar signal to the transmitted radar signal;

determine a first phase offset of the first reflected radar signal received at a first antenna of the plurality of antennas relative to a phase of the first reflected radar signal received at a reference antenna of the plurality of antennas;

determine a second phase offset of the second reflected radar signal received at the first antenna relative to a phase of the second reflected radar signal received at the reference antenna;

determine a third phase offset of the third reflected radar signal received at the first antenna relative to a phase of the third reflected radar signal received at the reference antenna; and

determine, for the first antenna, a phase offset calibration error based on:

a first phase offset calibration error for the first object based on the first doppler measurement and the first phase offset;

a second phase offset calibration error for the second object based on the second doppler measurement and the second phase offset; and

a third phase offset calibration error for the third object based on the third doppler measurement and the third phase offset.

17. The vehicle of claim 16 , the radar system to determine, for each object of the plurality of objects, a phase offset calibration error specific to the respective object based on a doppler measurement and a phase offset measurement determined from a reflected radar signal from the respective object.

18. The vehicle of claim 16 , the radar system to:

determine a second phase offset of the first reflected radar signal received at a second antenna of the plurality of antennas relative to the phase of the first reflected radar signal received at the reference antenna of the plurality of antennas; and

determine, for the second antenna, a phase offset calibration error based on the first doppler measurement and the second phase offset of the first reflected radar signal received at the second antenna.

19. The vehicle of claim 16 , the radar system to calculate an angle indicating a position of the first object that reflected the first reflected radar signal, the angle calculation based in part on a corrected phase offset calculated by subtracting the phase offset calibration error for the first antenna from the first phase offset.

20. The vehicle of claim 16 , wherein the radar system is to determine the phase offset calibration error for the first antenna based on a speed of the vehicle.