Fiber lattice accumulator design considerations for opitcal [sigma-delta] digital antennas

Abstract

The ability to directly oversample and digitize microwave range signals at an antenna is not possible with current electronic technologies. The objective for this thesis was to design and computer model an optical sampling and digitization process using a mode-locked laser and fiber lattice accumulators. A novel fiber lattice accumulator design for integrated optical sigma-delta digital antenna technology is presented. The fiber lattice design uses phase modulation to produce the proper interference between input and recirculated/delayed optical pulses in order that they may coherently combine. In this manner, accumulation within the fiber lattice takes into account the sign of a sampled bipolar antenna signal. The fiber lattice performance is numerically evaluated within a first-order optical sigma-delta digital antenna phase coherent simulation. The initial computer simulations show promising results using lower frequency antenna signals to verify optical design feasibility and operation. Optical results closely matched all-electronic simulations. The error between the input antenna and output signals is quantified, and proves correct device performance. All results show the first- order optical sigma-delta does work and is ready for experimental construction. The significance of this device will be its usefulness in extending high resolution sigma-delta analog-to-digital conversion into the microwave signal bands