A 4-GS/s 80-dB DR Current-Domain Analog Frontend for Phase-Coded Pulse-Compression Direct Time-of-Flight Automotive Lidar

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/√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 ~50 W, this work achieves an inaccuracy of 0.225 m (1σ) over 60-m range at 10x lower peak transmit power of ~3.5 W.