Design and experimental evaluation of an electro-optical, sigma-delta modulator for wideband digital antennas

Abstract

Electro-optical sigma-delta analog-to-digital converters (ADCs) use a pulsed laser to oversample an input signal at two Mach-Zehnder interferometer modulators. A fiber lattice accumulator is embedded within a feedback loop around a single-bit quantizer to spectrally shape the quantization noise to fall outside the signal band of interest. Applications of electro-optical sigma-delta ADCs include digitizing wideband radio frequency signals directly at an antenna (digital antenna). The design considerations, construction process and experimental evaluation of the electro-optical sigma-delta ADC are presented. The experimental results are compared with a computer model of the electro- optical sigma-delta sampling and digitization process.