Systems and methods for chirp linearization using external reflector(s) as a reference reflector

A method for linearizing frequency chirp in a frequency-modulated continuous wave (FMCW) coherent LiDAR system, the method comprising:

• generating a continuous wave laser signal having a frequency characteristic, the frequency characteristic comprising a frequency chirp over a frequency band in at least one period;
• receiving a signal based on the generated laser signal, wherein the received signal is a reflected signal from a reference reflector positioned external to the LiDAR system;
• mixing the received signal with a local oscillator signal, the local oscillator signal having the frequency characteristic;
• determining at least one beat frequency based on the mixed signal;
• sampling the mixed signal at a rate equal to at least two times the beat frequency;
• and
• determining a correction signal based on the sampled signal, wherein,
• for a given sample in the sampled signal, the correction signal indicates a difference between the laser signal and an ideal signal,
• wherein the ideal signal has an ideal frequency characteristic, the ideal frequency characteristic comprising a linear frequency chirp over the frequency band in the at least one period, and
• wherein the difference is between the frequency characteristic of the laser signal and the ideal frequency characteristic.

A system for linearizing frequency chirp in a frequency-modulated continuous wave (FMCW) coherent LiDAR system, the system comprising:

• a laser configured to generate a continuous wave laser signal having a frequency characteristic, the frequency characteristic comprising a frequency chirp over a frequency band in at least one period;
• a mixer coupled to an output of the laser and configured to mix:
• a received signal based on the generated laser signal, wherein the received signal is a reflected signal from a reference reflector positioned external to the LiDAR system, wherein the reference reflector is positioned at a pre-determined, fixed range from the LiDAR system;
• and
• a local oscillator signal having the frequency characteristic;
• an analog-to-digital converter coupled to an output of the mixer and configured to sample the mixed signal at a rate equal to at least two times a beat frequency of the mixed signal;
• and
• a processor coupled to an output of the converter and configured to determine a correction signal based on the sampled signal and on the pre-determined, fixed range from the LiDAR system to the reference reflector.

A system for linearizing frequency chirp in a frequency-modulated continuous wave (FMCW) coherent LiDAR system, the system comprising:

• a laser configured to generate a continuous wave laser signal having a frequency characteristic, the frequency characteristic comprising a frequency chirp over a frequency band in at least one period;
• a mixer coupled to an output of the laser and configured to mix:
• a received signal based on the generated laser signal, wherein the received signal is a reflected signal from a reference reflector positioned external to the LiDAR system;
• and
• a local oscillator signal having the frequency characteristic;
• an analog-to-digital converter coupled to an output of the mixer and configured to sample the mixed signal at a rate equal to at least two times a beat frequency of the mixed signal;
• and
• a processor coupled to an output of the converter and configured to determine a correction signal based on the sampled signal,
• wherein for a given sample in the sampled signal, the correction signal indicates a difference between the laser signal and an ideal signal,
• wherein the ideal signal has an ideal frequency characteristic, the ideal frequency characteristic comprising a linear frequency chirp over the frequency band in the at least one period, and
• wherein the difference is between the frequency characteristic of the laser signal and the ideal frequency characteristic.