A compact acousto-optic time integrating correlator has been developed for passive surveillance applications. The correlator has a bandwidth of 100 MHz about a center frequency (IF) of 300 MHz to provide time-difference-of-arrival information with a resolution of less than 10 nsec useful in locating wideband radar jammers when signals are received at two widely separated antennas. On an airborne platform, the correlator may perform passive ranging. This correlator features the use of counterpropagating surface acoustic waves on a single lithium niobate delay line interacting with light from a laser diode. Diffracted beams are interferometrically combined on an integrating photodiode array. Integration time of 1 msec provides a time-bandwidth product of 105. A two dimensional correlator allows processing of both time-difference-of-arrival and differential Doppler, and a related processor performs both cross correlation and cross spectrum analysis.
Irwin J. Abramovitz,
"Acousto-Optic Processors For Passive Surveillance", Proc. SPIE 0519, Analog Optical Processing and Computing, (21 January 1985); doi: 10.1117/12.945196; https://doi.org/10.1117/12.945196