On the Design of Low-Power Front-End Receiver Circuits for Broadband Optical Free-Space Links

Optical wireless technology is emerging as a key broadband access technology for short-range, broadband wireless applications, offering several advantages over conventional RF systems in terms of connection speed, power efficiency, low transceiver complexity, networking security, and unregulated bandwidths in the THz range. This paper reviews design aspects of low-power, front-end optical wireless receiver circuits and presents a low-noise front-end preamplifier circuit implementing self-biased, automatic gain control and capable of integration with wide field of view detectors necessary for broadband optical wireless applications. The preamplifier is implemented in a low-cost commodity CMOS technology. For a gain variation of 38 dB to 50 dB, the front-end maintains a stable response and minimum 3 dB bandwidth of 345 MHz with a 6 pF photodiode capacitance. The input-referred noise is 12.5 pA/radicHz at 350 MHz.