Photorefractive adaptive filter structure with 40-dB interference rejection

A new architecture for photorefractive adaptive filtering is introduced. This architecture is based on the principle of time-integrating correlator with a photorefractive material as the time-integrating photosensor. A compact and rugged system is achieved by using the same Bragg cell as both the delay line for computing correlation values and the delay to which the tap weights are applied. In this way a self-aligning structure is achieved. Semiconductor photorefractive materials are used with 1.2-1.3-microm wavelength injection lasers to achieve fast response, low power, and a compact structure. Tests of an experimental system demonstrated >40-dB rejection of narrow-band interference with a transient response time constant of 70micros.