A Study on the Invalidation Case of Partially Overlapped Multilook Processing of the SAR Data of Sea Surface for Uncorrelated Speckle Patterns

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In the present paper, a general integral expression is derived and discussed for the CCF (cross-correlation function) of speckle patterns in SAR images of sea surface as a function of the center time difference of subapertures and scene coherence time. It is shown that, under the white noise approximation for the backscattered field, the interlook speckle CCF is given by the squared modulus of the autocorrelation function of the subaperture amplitude weighting function. It is also shown that the CCF is independent of the surface coherence time of sea surface. Thus, in order to produce multilook images with uncorrelated speckle patterns, it is not possible to process the raw data by partially overlapped subapertures whose center time separation is of the order of the scene coherence time. The integral expression for the intensity CCF is then evaluated and an analytic expression is derived for a rectangular weighting function. The theory is compared with the JERS-1 L-band and RADARSAT-1 C-band SAR images; and as a result, the estimated CCFs from both the SAR data are shown to be in good agreement with the theory.
社団法人電子情報通信学会の論文
2005-05-20