Methods and systems for removing transmit phase noise

1. A system comprising:

a radar unit;

a printed circuit board (PCB) having a transmission line coupled to the radar unit and a delay line coupled to a quadrature coupler; and

a processing unit configured to:

cause the PCB to supply a signal, wherein the transmission line is configured to couple the signal to the radar unit and the delay line is configured to couple the signal to the quadrature coupler;

cause the radar unit to transmit a radar signal on a radio channel having a centered radio frequency (RF) using the signal;

estimate phase noise relative to the radio channel having the centered RF based on both an output from the quadrature coupler and a dispersive nature of the delay line, wherein the quadrature coupler receives the signal via the delay line and generates the output as a complex-valued signal, wherein the dispersive nature of the delay line depends on a length of the delay line, wherein the delay line comprises an in-phase output line and a quadrature output line, and wherein a length of the quadrature output line is greater than a length of the in-phase output line;

receive, from the radar unit, a radar reflection corresponding to the radar signal;

responsive to receiving the radar reflection, generate a mixed signal that combines the radar reflection and the output from the quadrature coupler;

remove, using a range deskew filter, phase noise from the mixed signal, wherein the phase noise removed from the mixed signal is based on the phase noise estimated relative to the radio channel having the centered RF; and

determine information representative of one or more objects using the mixed signal.

2. The system of claim 1 , wherein the radar unit is configured to transmit the radar signal as a stretch Linear Frequency Modulated (LFM) pulse waveform.

3. The system of claim 1 , wherein the delay line and the quadrature coupler correspond to a phase noise measurement circuit, and wherein the phase noise measurement circuit further includes an intermediate frequency (IF) filter, one or more gain stages, a homodyne mixer, and an analog-to-digital converter.

4. The system of claim 1 , wherein the radar unit is coupled to a vehicle, and wherein the processing unit is further configured to:

provide instructions to a control system of the vehicle based on the information representative of the one or more objects, wherein the control system is configured to control the vehicle based at least in part on the instructions.

5. A method comprising:

causing, by a computing device, a printed circuit board (PCB) to supply a signal, wherein the PCB includes a transmission line coupled to a radar unit and a delay line coupled to a quadrature coupler, and wherein the transmission line is configured to couple the signal to the radar unit and the delay line is configured to couple the signal to the quadrature coupler;

causing, by the computing device, the radar unit to transmit a radar signal on a radio channel having a centered radio frequency (RF) using the signal;

estimating phase noise relative to the radio channel having the centered RF based on both an output from the quadrature coupler and a dispersive nature of the delay line, wherein the quadrature coupler receives the signal via the delay line and generates the output as a complex-valued signal, wherein the dispersive nature of the delay line depends on a length of the delay line, wherein the delay line comprises an in-phase output line and a quadrature output line, and wherein a length of the quadrature output line is greater than a length of the in-phase output line;

receiving, at the computing device and from the radar unit, a radar reflection corresponding to the radar signal;

responsive to receiving the radar reflection, generating a mixed signal that combines the radar reflection and the output from the quadrature coupler;

removing, using a range deskew filter, phase noise from the mixed signal, wherein the phase noise removed from the mixed signal is based on the phase noise estimated relative to the radio channel having the centered RF; and

determining, by the computing device, information representative of one or more objects using the mixed signal.

6. The method of claim 5 , wherein causing the radar unit to transmit the radar signal on the radio channel having the centered radio frequency (RF) using the signal comprises:

causing the radar unit to transmit the radar signal as a stretch Linear Frequency Modulated (LFM) pulse waveform.

7. The method of claim 5 , further comprising:

providing instructions to a control system of a vehicle based on the information representative of the one or more objects, wherein the control system is configured to control the vehicle based at least in part on the instructions.

8. A non-transitory computer-readable medium configured to store instructions, that when executed by a computing system comprising one or more processors, causes the computing system to perform operations comprising:

causing a printed circuit board (PCB) to supply a signal, wherein the PCB includes a transmission line coupled to a radar unit and a delay line coupled to a quadrature coupler, and wherein the transmission line is configured to couple the signal to the radar unit and the delay line is configured to couple the signal to the quadrature coupler;

causing the radar unit to transmit a radar signal on a radio channel having a centered radio frequency (RF) using the signal;

estimating phase noise relative to the radio channel having the centered RF based on both an output from the quadrature coupler and a dispersive nature of the delay line, wherein the quadrature coupler receives the signal via the delay line and generates the output as a complex-valued signal, wherein the dispersive nature of the delay line depends on the length of the delay line, wherein the delay line comprises an in-phase output line and a quadrature output line, and wherein a length of the quadrature output line is greater than a length of the in-phase output line;

receiving, from the radar unit, a radar reflection corresponding to the radar signal;

responsive to receiving the radar reflection, generating a mixed signal that combines the radar reflection and the output from the quadrature coupler;

removing, using a range deskew filter, phase noise from the mixed signal, wherein the phase noise removed from the mixed signal is based on the phase noise estimated relative to the radio channel having the centered RF; and

determining information representative of one or more objects using the mixed signal.

9. The non-transitory computer-readable medium of claim 8 , wherein causing the radar unit to transmit the radar signal on the radio channel having the centered radio frequency (RF) using the signal comprises:

causing the radar unit to transmit the radar signal as a stretch Linear Frequency Modulated (LFM) pulse waveform.

10. The non-transitory computer-readable medium of claim 8 , further comprising:

providing instructions to a control system of a vehicle based on the information representative of the one or more objects, wherein the control system is configured to control the vehicle based at least in part on the instructions.

11. The system of claim 1 , wherein the quadrature coupler is further configured to generate a first output and a second output, wherein the first output and the second output have a 90 degree phase difference.

12. The system of claim 11 , wherein the processing unit is further configured to:

independently mix the first output and the second output down to basebands prior to an analog-to-digital sampling.