A Novel Balanced Detection Based Optoelectronic Front End Circuit for FMCW LiDAR System

To take the advantages of the remote detection distance and wide detection range from Frequency Modulated Continuous Wave (FMCW) LiDAR system, this paper proposes a novel optoelectronic front end circuit consisting of a balanced-detection (BD) based interface and an Analog Front-End (AFE) circuit. The BD based interface adopts a coupler and differential photodiodes to reduce parasitics and noise, which extends the bandwidth and dynamic range of AFE circuit. The AFE circuit employs a three-stage fully differential shunt-feedback pre-transimpedance amplifier to reduce input impedance and a two-stage variable gain post-amplifier to enhance gain regulation range, which further improve the bandwidth and dynamic range. The proposed AFE circuit in a 40-nm CMOS has achieved a gain of 100 dBΩ from 1 MHz to 132 MHz and a dynamic range up to 66.2 dB. The input-referred noise current is 5.8 pA/√Hz and the power consumption is 11.64 mW at 1.1 V. Compared with the state-of-art designs, the proposed AFE circuit has achieved 1.2× bandwidth expansion and a considerably-improved dynamic range.