Statistical analysis of monopulse-synthetic aperture radar for constant false-alarm rate detection of ground moving targets

An efficient approach to achieve ground moving target indication (GMTI) for synthetic aperture radar (SAR) is to use the monopulse-SAR system. In this kind of SAR system, moving targets are detected over a so called, called monopulse ratio diagram (MRD) generated by a pixel-to-pixel comparison between the two SAR images acquired from the sum and difference channels. The sample derived from this diagram for the pixel under test (PUT), i.e. the value of monopulse ratio (MR), is employed as the test statistic. This paper examines the statistics of MR when complex Gaussian clutter-plus-noise background in considered. The conditional probability density function (pdf) of MR, given the occurrence that the amplitude of the sum signal is greater than a predetermined threshold, is analysed in detail. Especially, the conditional likelihood function of MR under the null hypothesis is given in a closed-form. Based on these results, an automatic constant false-alarm rate (CFAR) detector for moving target detection (MTD) is proposed and extended to a so called multi-MRD form to further improve the final detection performance. Simulations, as well as experimental results obtained from two groups of real dataset, are presented to examine the detection performance and validate the theoretical analysis.