An optical-electrical sub-sampling down-conversion receiver with continuous-time [Sigma] [Delta] modulation

Abstract

This thesis describes the design and implementation of an optical-electrical sub-sampling down-conversion receiver that employs [Sigma] [Delta] modulation. Accurate sub-sampling of an electrical RF signal in the optical domain is achieved by using a low-jitter mode-locked-laser and a high-bandwidth interferometer. The sub-sampled information is then digitized by an optical-electrical continuous-time (CT) [Sigma] [Delta] analog- to-digital converter (ADC). Here, photodiodes and low-jitter pulses from the mode- locked-laser are leveraged to perform signal clocking and quantizer pre-amplification, overcoming digital-to-analog converter (DAC) clock jitter and quantizer metastability issues that plague traditional electronic implementations. The optical-electrical converter achieves 76.5 dB of SNR (12.4 ENOB) with a 1 MHz signal bandwidth and a sampling rate of 780 MHz. The chip was implemented using a standard bulk 0.18 [mu]m CMOS process from National Semiconductor, occupies a total area of 3 mm2, and consumes 45 mW of power.