A 6-Gb/s CMOS imaging diversity receiver front-end employing select-best method

This paper presents an imaging diversity receiver front-end employing select-best method for free-space optical (FSO) communication. The imaging receiver consists of a seven channel transimpedance amplifier (TIA) array and a select-best circuit implemented in a 180nm CMOS technology. This imaging receiver is designed for flip-chip bonding to a custom InGaAs MSM (metal-semiconductor-metal) photodetector array. Each single-channel front-end TIA provides a transimpedance gain of 60.2dBΩ and a −3dB bandwidth of 4.4GHz for 250fF photodiode capacitance. The select-best circuit employs a novel winner-take-all peak detector structure and demonstrates high-speed, high-precision reception. The resolution of the imaging receiver with select-best is about 2μA near 20μA input current and 4μA near 400μA input current at 6Gb/s. The power dissipation for a single channel TIA is 8.2mW, and for the select-best circuit is 26.6mW from a single 1.8V supply.