Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision

Adaptive RF interference reduction for broadband communication systems continues to be problematic. The acousto-optic RF signal excision system offers real-time, narrowband RF interference, frequency domain filtering for broadband communication systems, but has been limited in its capability for adaptive processing and rejection of broadband RF interference. As a means to reduce these limitations, this dissertation examines the application of a novel photorefractive optical power limiting device to achieve adaptive notch filtering, and multi- channel acousto-optic deflection to achieve angle-of- arrival signal discrimination at the notch filter. This dissertation describes basic principles of acousto-optic RF signal excision, including linear phased- array antenna, angle-of- arrival processing using a multi-channel acousto-optic deflector. The principles are verified experimentally by demonstration of frequency domain filtering according to frequency and angle of arrival. This dissertation also describes basic principles of photorefractive optical power limiting, which is a new approach for achieving adaptive, frequency-domain notch filtering. Photorefractive field shielding of electro-optic birefringence is examined by numerical solution of the band- transport model, and experimental measurement of notch filter amplitude and spatial profiles for high-intensity, Gaussian beam optical illumination and high- intensity, externally applied electric fields. Results indicate that for illumination-beam radius larger than a few microns, power-limiting notch widths follow the illumination intensity and terminate at the dark-to-light illumination interface where excess charge accumulates.Air Force Research Lab Wright-Patterson AFB OH Sensors Directorate is the author of 'Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision', published 2001 under ISBN 9781423522898 and ISBN 1423522893.