Configurable non-linear gain amplifier and lidar analog front end
An optical receiver includes one or more photodetectors and an analog front end (AFE) configured to accept input signals from the one or more photodetectors. The AFE includes a non-linear gain amplifier (NLGA). The NLGA includes a piecewise linear gain stage configured to apply a piecewise linear transfer function to the input signals to form amplified signals. The AFE also includes a DC offset stage configured to apply a DC offset to the amplified signals. A related method of operation and vehicle are also disclosed.
1 . An optical receiver, comprising:
one or more photodetectors; and
an analog front end (AFE) configured to accept input signals from the one or more photodetectors, wherein the AFE comprises:
a non-linear gain amplifier (NLGA), wherein the NLGA comprises:
a piecewise linear gain stage configured to apply a piecewise linear transfer function to the input signals to form amplified signals, wherein the piecewise linear gain stage comprises a high gain saturating amplifier and a lower gain linear non-saturating amplifier; and
a DC offset stage configured to apply a DC offset to the amplified signals.
2 . The optical receiver of claim 1 , wherein the NLGA is configured to amplify small signal portions of the input signals and compress large signal portions of the input signals.
3 . The optical receiver of claim 1 , wherein the piecewise linear transfer function comprises a high gain (G high ) for input signals with an amplitude below a threshold voltage (V thresh,in ), and a low gain (G low ) for input signals with an amplitude above the threshold voltage.
4 . The optical receiver of claim 3 , wherein G low is selectable between 0.05 and 0.5, wherein G high is selectable between 2 and 20.
5 . The optical receiver of claim 1 , wherein the piecewise linear transfer function comprises a positive fullscale voltage level (V FS+ ) and a negative fullscale voltage level (V FS− ), which define a maximum voltage range (V swing ), wherein V swing is selectable between 300 mV to 600 mV in steps of 150 mV.
6 . The optical receiver of claim 1 , wherein the NLGA is configured to operate with a settling time, ΔT 50% =T 50%,rise −T 50%,fall , wherein an absolute value of ΔT 50% is less than 200 ps.
7 . The optical receiver of claim 1 , wherein the NLGA further comprises:
a transimpedance amplifier (TIA) configured to convert an output of the DC offset stage to a voltage-based signal.
8 . The optical receiver of claim 1 , further comprising a plurality of AFE channels, wherein each AFE channel comprises:
a bandgap voltage reference;
a low dropout regulator;
one or more phase-locked loop cores;
continuous-time analog circuitry; and
an analog-to-digital converter (ADC).
9 . The optical receiver of claim 8 , wherein the DC offset stage comprises an offset digital-to-analog converter (DAC) configured to inject a DC offset into an amplified signal output to optimally utilize a full differential dynamic range of the ADC.
10 . The optical receiver of claim 8 , wherein the DAC comprises a 6 bit resolution and an output range of between zero and −500 mV.
11 . The optical receiver of claim 1 , wherein the NLGA is configured to operate between 1 GHz to 3 GHz.
12 . A method, comprising:
receiving, by an analog front end (AFE) of an optical receiver, input signals from a plurality of photodetectors;
applying a piecewise linear transfer function to the input signals to form amplified signals, wherein applying the piecewise linear transfer function comprises utilizing a piecewise linear gain stage, wherein the piecewise linear gain stage comprises a high gain saturating amplifier and a lower gain linear non-saturating amplifier; and
applying a DC offset to the amplified signals.
13 . The method of claim 12 , wherein applying the piecewise linear transfer function comprises amplifying small signal portions of the input signals and compressing large signal portions of the input signals.
14 . The method of claim 12 , wherein the AFE comprises a common-mode to differential-mode (CM-to-DM) rejection rate of at least 40 dB.
15 . The method of claim 12 , wherein the piecewise linear transfer function comprises a high gain (G high ) for input signals with an amplitude below a threshold voltage (V thresh,in ) and a low gain (G low ) for input signals with an amplitude above the threshold voltage.
16 . The method of claim 12 , wherein applying the DC offset is performed by a DC offset stage, wherein the DC offset stage comprises an offset digital-to-analog converter (DAC) configured to inject a DC offset into an amplified signal output to optimally utilize a full differential dynamic range of an associated ADC.
17 . The method of claim 12 , further comprising selecting high gain, G high , and a low gain, G low , wherein G low is selectable between 0.05 and 0.5, wherein G high is selectable between 2 and 20.
18 . A vehicle, comprising:
an optical receiver, comprising:
one or more photodetectors; and
an analog front end (AFE) configured to accept input signals from the one or more photodetectors, wherein the AFE comprises:
a non-linear gain amplifier (NLGA), wherein the NLGA comprises:
a piecewise linear gain stage configured to apply a piecewise linear transfer function to the input signals to form amplified signals, wherein the piecewise linear gain stage comprises a high gain saturating amplifier and a lower gain linear non-saturating amplifier; and
a DC offset stage configured to apply a DC offset to the amplified signals.
19 . The vehicle of claim 18 , wherein the piecewise linear transfer function comprises a high gain (G high ) for input signals with an amplitude below a threshold voltage (V thresh,in ), and a low gain (G low ) for input signals with an amplitude above the threshold voltage.
20 . The vehicle of claim 19 , wherein G low is selectable between 0.05 and 0.5, wherein G high is selectable between 2 and 20.