A 4-GS/s 80-dB DR Current-Domain Analog Frontend for Phase-Coded Pulse-Compression Direct Time-of-Flight Automotive Lidar
IEEE Journal of Solid-State Circuits(2020)
Abstract
A 4-GS/s current-domain analog front end (CurAFE) for phase-coded pulse-compression direct time- offlight (dTOF) automotive Lidar has been realized in 130-nm CMOS. The permissible eye-safe laser energy is transmitted in the form of a burst of optical sub-pulses. The burst embeds a phase coding designed to have an auto-correlation function with a maximum peak-to-sidelobe ratio. The optical reflection of this burst, reflected from a target, is then detected by an avalanche photodiode (APD). The APD's output current drives the CurAFE, whose 4-GS/s single-bit output is processed by a digital matched filter for pulse-compression and TOF estimation through cross correlation. The 200-MHz bandwidth frontend detects bursts with bitrates up to 200 Mb/s (5-ns sub-pulsewidth) and is designed for >80-dB DR without saturation and 5-pA/root Hz input-referred noise. A current-feedback dc servo loop at its input cancels the background-light-induced detector current. Compared to state-of-the-art single-pulse Lidars, operating with peak optical transmit powers similar to 50 W, this work achieves an inaccuracy of 0.225 m (1 sigma) over 60-m range at >10x lower peak transmit power of similar to 3.5 W.
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Key words
Analog frontend (AFE),auto-zero,avalanche photodiode (APD),cross correlation,current domain,laser,lidar,matched filter,phase code,photodetector,pulse-compression,self-calibration,time-interleaved analog-to-digital converter (ADC)
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