21 December 1994 Extension of the correlation Doppler estimator for determination of the Doppler rate and for resolving the PRF-ambiguity
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Recently the chirp scaling algorithm has been proposed for high quality SAR processing. The algorithm requires first a transformation of the range uncompressed SAR raw data into the range-Doppler domain, which does not permit conventional techniques for the estimation of the Doppler parameters to be introduced efficiently into the processing. This paper first reviews the so called 'correlation Doppler estimator' (CDE), which was proposed for the estimation of the Doppler centroid in the time domain. This estimation algorithm is further extended in order to allow also the estimation of the Doppler rate. To perform this only bright targets are considered. By continuous calculation of the first coefficient of the auto-correlation function, the slope of the frequency history of the Doppler signal is determined, giving an exact estimate of the Doppler rate. to obtain also an estimation of the Doppler rate for scenes without bright targets but with some contrast, a modified version of the SAC algorithm is presented. Further a new method is presented, which can solve the PRF-ambiguity by means of an evaluation of the signal envelope skew in the range-Doppler domain. This technique does not require any additional range FFT, since it is based on the estimation of the variation of a range centroid as a function of the azimuth frequency. Several results are presented, which show the performance of the proposed new approaches. Some remarks are made regarding the inclusion of the described methods into the extended chirp scaling algorithm.
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Rolf Scheiber, Rolf Scheiber, Alberto Moreira, Alberto Moreira, } "Extension of the correlation Doppler estimator for determination of the Doppler rate and for resolving the PRF-ambiguity", Proc. SPIE 2316, SAR Data Processing for Remote Sensing, (21 December 1994); doi: 10.1117/12.197551; https://doi.org/10.1117/12.197551

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