Acoustooptical approaches to radar signal processing

To realize full benefit from a radar, the analyzed echoes must be strong and sharp. Two options are available: Either the transmitted burst must be an intense, short pulse (often not a propitious arrangement) or the onus can be put on the receiver to process the echo into something more than it appears to be. One method for ``upgrading'' the received signal beyond a feeble echo from a not-too-powerful transmitted beam is acoustooptical processing, in which the reflected radar beam is converted to an acoustic wave that is used to modulate a light source. Then with the appropriate operation on the modulated light, the radar echo input is correlated against an optical filter. Of the two acoustooptic correlator classes described here, one works well below 150 MHz and the other is appropriate for frequencies above 150 MHz.