Acousto-optic channel equalization for digital communications

Abstract

Digital communication systems use complex modulation schemes that require powerful signal-processing techniques to correct channel distortions and to minimize bit error rates. In this paper, acousto-optic processors are used, in conjunction with adaptive digital equalizers, to reduce the bit error rate of a microwave digital radio receiver. The acousto-optic processor implements an inverse channel filter that is rapidly adaptable to time varying distortions. A specific architecture is identified and a laboratory system is tested to verify the ability of the processor to track and correct time-varying channels. Computer simulations are used to show that the hybrid acousto-optic and digital equalizer allows a four-fold increase in the modulation capacity of radio, relative to all digital equalization, while improving the bit error rate performance.