Coherent pulsed lidar system

A method comprising:

• emitting, by a light source of a lidar system, local-oscillator (LO) light and pulses of light, the emitted pulses of light comprising a first emitted pulse of light, wherein an optical frequency of the first emitted pulse of light is offset from an optical frequency of the LO light by a first frequency offset;
• detecting, by a receiver of the lidar system, the LO light and a first received pulse of light, the first received pulse of light comprising light from the first emitted pulse of light scattered by a target located a distance from the lidar system, wherein detecting the LO light and the first received pulse of light comprises:
• producing, by a detector of the receiver, a photocurrent signal corresponding to coherent mixing of the LO light and the first received pulse of light, the photocurrent signal comprising an amplitude-modulation (AM) signal;
• and
• producing, by a detection circuit of the receiver, an output signal corresponding to the AM photocurrent signal, wherein producing the output signal comprises:
• amplifying, by an electronic amplifier of the detection circuit, the photocurrent signal to produce a voltage signal corresponding to the photocurrent signal;
• and
• producing, by each frequency-detection channel of one or more frequency-detection channels of the detection circuit, a portion of the output signal, wherein each frequency-detection channel comprises:
• an electronic local oscillator configured to produce an electronic local-oscillator signal having a particular oscillator frequency;
• an electronic mixer configured to mix the voltage signal with the electronic local-oscillator signal to produce an intermediate-frequency signal;
• and
• an electronic filter configured to transmit a portion of the intermediate-frequency signal located within a pass-band of the electronic filter;
• and
• determining, by a processor of the lidar system and based on the output signal, that the first received pulse of light is associated with the first emitted pulse of light.

A lidar system comprising:

• a light source configured to emit local-oscillator (LO) light and pulses of light, the emitted pulses of light comprising a first emitted pulse of light, wherein an optical frequency of the first emitted pulse of light is offset from an optical frequency of the LO light by a first frequency offset;
• a receiver configured to detect the LO light and a first received pulse of light, the first received pulse of light comprising light from the first emitted pulse of light scattered by a target located a distance from the lidar system, wherein the receiver comprises:
• a detector, wherein:
• the LO light and the first received pulse of light are coherently mixed together at the detector;
• and
• the detector is configured to produce a photocurrent signal corresponding to the coherent mixing of the LO light and the first received pulse of light, the photocurrent signal comprising an amplitude-modulation (AM) signal;
• and
• a detection circuit configured to receive the photocurrent signal and produce an output signal corresponding to the AM photocurrent signal, wherein the detection circuit comprises:
• an electronic amplifier configured to amplify the photocurrent signal to produce a voltage signal corresponding to the photocurrent signal;
• and
• one or more frequency-detection channels, each frequency-detection channel configured to receive the voltage signal and produce a portion of the output signal, wherein each frequency-detection channel comprises:
• an electronic local oscillator configured to produce an electronic local-oscillator signal having a particular oscillator frequency;
• an electronic mixer configured to mix the voltage signal with the electronic local-oscillator signal to produce an intermediate-frequency signal;
• and
• a digitizer configured to produce a digitized signal corresponding to the intermediate-frequency signal;
• and
• a processor configured to determine, based on the output signal, that the first received pulse of light is associated with the first emitted pulse of light.