Large-diameter-APD receiver for optical wireless communication

Abstract

This thesis covers the design of an opto electronic integrated circuit (OEIC) applicable as receiver in an optical wireless communication (OWC) system. With the intended application for digital audio communication, the chip produces an output level of 3.3V, to ensure compatibility to standard decoding systems. The designed chip is optimized for processing data rates (DRs) appearing with state-of-the-art encoded audio qualities of up to 4.605Mbit/s. For photodetection, a fully integrated large area avalanche photo diode (APD) (diameter = 800μm) was used, offering higher sensitivity compared to other optical-detector devices. A major challenge, arising with OWC, is sensitivity to background light irradiation. Therefore the receiver contains a dummy-path working as a direct current (DC) reference for the signal-path, together forming a pseudo differential structure. Implemented feedback circuitry is able to sense and cancel an offset between these two paths. Additionally, problems arising with flicker noise when operating at low DR are addressed. Post layout simulations resulted in a sensitivity of -62.34 dBm and a dynamic range of 25.47 dB. The OEIC was designed in a 0.35 μm BiCMOS process.