INTEGRATED OPTICAL SIGMA-DELTA MODULATORS

Modern avionics equipment, such as superresolution direction-finding s ystems (frequency band 0.3 to 3 MHz), now require resolutions greater than 15 bits. Oversampled analog-to-digital converter architectures of fer a means of exchanging resolution in time for that in amplitude and represent an attractive approach to implementing precision converters without the need for complex precision analog circuits. Using oversam pling techniques based on sigma-delta (Sigma Delta) modulation, a conv enient trade-off exists between sampling rate and resolution, One of t he major advantages of integrated optics is the capability to efficien tly couple wideband signals into the optical domain. Typically, Sigma Delta processors require simple and relatively low precision analog co mponents and thus are well suited to integrated optical implementation s. The current Sigma Delta methodology is reviewed and the design of t he single-bit, integrated optical Sigma Delta modulator is presented. Simulation results for both first- and second-order architectures are presented by evaluating the transfer characteristics numerically. A 16 -bit f(0)=1 MHz design (oversampling ratio of 132) is also quantified. (C) 1996 Society of Photo-Optical Instrumentation Engineers.