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Anacousto-optic (AO) correlator is being constructed that offers a small, lightweight solution to detectingand analyzing widebandwidth, spread-spectrum signals. The processor is being inserted into an existingelectronic support measure (ESM) test-bed under the Defense Advanced Research Projects Agency (DARPA)Transition of Optical Processors into Systems (TOPS) program. The correlator has a processing bandwidth of500 MHz and will be used to detect direct-sequence, phase-modulated signals, frequency-hopped signals, chirps,and impulses. A description of the processor is provided along with experimental results obtained from aninterim developmental breadboard. Subsequent digital processing, which includes nonlinear detection andFourier transformation, is used to determine center frequencies, bandwidths, and band shape. Theoreticaldescriptions of the post-processing are provided and simulation results are discussed.1. INTRODUCTIONSignal environments are becoming increasingly complex in both signal density and emitter sophistication.Future battlefield systems are expected to increase the use ofwideband impulse, direct-sequence, and frequency-hopped signals. To more readily intercept and classif' these signals, additional receiver sophistication isrequired. Current ESM receivers work very well at detecting and characterizing narrowband and pulsed signals;however, wide-bandwidth and spread-spectrum signals are not as readily handled. As an example in some ESMreceivers, a frequency-hopped signal may be reported as a multitude of individual, narrowband signals insteadof a single wideband, spread-spectrum signal. |
