A Technique for a Multi-Doppler, Quadrature Correlation Processing Scheme.
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The location of echoes resulting from transmitted waveforms exhibiting simultaneous Doppler and range resolution requires that a two-dimension search be undertaken. Techniques for range searching using correlation methods are well known. Doppler search using multiple references has been used, but this method is quite inefficient when simulated on a digital computer. The method presented here makes use of the observation that if the Doppler shift is relatively small, it can be treated, approximately, as a frequency shift. It is simulation of a method sometimes used in analog correlators in which the multiplier is followed by a bank of band-pass filters instead of a simple integrator. The difference in center frequency of the various filters produces a result which is identical to that produced by offsetting the frequency of the reference by the same amount. Thus, with a single reference, one can obtain several Doppler channels. The limit, which depends on the time-bandwidth product, Beta T, is the approximation of Doppler time compression by a simple frequency shift.
- Acoustic Detection and Detectors