Acousto-optic channel equalization for microwave digital radios

Abstract

Digital radio transmission systems use complex modulation schemes that require powerful signalprocessing techniques to correct channel distortions and to minimize bit error rates. Acousto-optic processors are used, in conjunction with adaptive digital equalizers, to reduce the bit error rate of the 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 permits a fourfold increase in the modulation capacity of radio, relative to all digital equalization, while improving the bit error rate performance.