CROSS MODULATION IN THE SCAMP SIGNAL PROCESSOR
NAVAL RESEARCH LAB WASHINGTON DC
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When two or more signals of different frequencies are fed simultaneously into the input of a limiter, cross-modulation products exist in the output. Such a situation occurs in the Scamp Single-Channel Monopulse Processor signal processor when the sum signal and both difference signals azimuth and elevation of a monopulse system are processed in a common limiter. The resultant cross modulation can produce deleterious effects, even though the spectra of the three input signals do not overlap. By the use of approximation methods, formulas are developed for the limiter outputs, showing the dependence of the cross-modulation terms on the input amplitudes and phases of both difference channels. Curves are presented illustrating the amount of cross modulation for several arrangements of channel spacing. The largest errors occur when the difference channels are symmetrically located on either side of the reference channel. The errors are substantially reduced by an unsymmetrical or a noncontiguous channel orientation. Experimental results on a simulated Scamp processor agree favorably with the theory.
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