8 December 1978 Acousto-Optic Implementation Of Real-And Near-Real-Time Signal Processing
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Abstract
Acousto-optic devices have been developed for implementing advanced signal processing functions required for real-time and near-real-time analysis of both high-frequency radar signals and low-frequency sonar signals. These devices use the Bragg interaction between laser beams and surface acoustic waves (SAW'S) to perform waveform convolution and correlation, achieving time-bandwidth products of 3000 to 10,000 with dynamic bandwidths of several hundred megahertz. Using these devices, wideband (about 100 MHz) signals have been extract-ed from extremely noisy environments (-30 dB signal-to-noise ratio) and a real-time Fourier transformation with a linear dynamic range exceeding 50 dB has been performed. A programmable correlator and a programmable filter have been demonstrated that use the newly discovered acousto-photorefractive memory effect. This effect is based on a nonlinear interaction between intense, short-duration laser pulses and a SAW signal propagating in lithium niobate, to form a semipermanent index-of-refraction pattern corresponding to the SAW signal. An implementation of the triple-product convolver architecture (proposed by Whitehouse et al.) for performing either a long one-dimensional or a two-dimensional discrete Fourier transform can be obtained by combining an acousto-optic convolver with many CCD chirp-Z transform modules. This triple-product convolver would have extremely rapid data handling capability and large dynamic range, and would be useful for applications such as "co-k" beam-forming for sonar signal processing. Further, a programmable 1-, 2-, 3-dimensional beam-former with a one second update capability may be feasible if the acousto-photorefractive memory effect is used to store SAW signals corresponding to the position of nonstationary sensors.
© (1978) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
N. J. Berg, N. J. Berg, J. N. Lee, J. N. Lee, M. w. Casseday, M. w. Casseday, } "Acousto-Optic Implementation Of Real-And Near-Real-Time Signal Processing", Proc. SPIE 0154, Real-Time Signal Processing I, (8 December 1978); doi: 10.1117/12.938254; https://doi.org/10.1117/12.938254
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