Along-track multichannel synthetic aperture radaris usually used to achieve ground moving target detection andimaging. Nevertheless, there is a design dilemma between azimuthhigh resolution and wide swath (HRWS). To solve this problemin HRWS mode, we introduce a virtual multichannel (VMC)scheme. For each virtual channel, the low real pulse repetitionfrequency (PRF) improves the ability of resolving range ambiguityfor wide-swath, and the high virtual PRF improves the capabilityof resolving Doppler ambiguity for azimuth high resolution. Formultiple virtual channels, strong ground clutter is eliminated bythe joint VMC processing. Furthermore, a detailed signal modelof a moving target in the virtual channel is given, and the specialfalse-peak effect in the azimuthal image is analyzed. Moreover, wepropose a novel ground moving target processing method basedon the VMC scheme and the clutter suppression interferometry(CSI) technique, which is called VMC-CSI. https://codeshoppy.com/shop/product/location-based-garbage-management-system-for-smart-city/ The integration ofdetection, location, velocity estimation, and imaging for groundmoving targets can be achieved. Accounting for the unresolvedmain peak and false peak for a moving target, in the VMC-CSImethod, we adopt a two-step scheme to estimate the radial velocityand along-track velocity, namely, rough estimation and precise es-timation. Meanwhile, considering the same interferometric phasesof the main peak and the false peak, we use false peaks first for therobustness of initial azimuth location estimation and remove falsepeaks afterward. Numerical simulations are provided for testingthe effect of the false peak and the effectiveness of VMC-CSI
Concept of VMCFig. 1(a) shows an along-track three-element SAR array,used for ground moving target indication (GMTI), where PRFdenotes the real PRF of the SAR system. The middle ele-ment indicates a multiplexing element used for transmittingand receiving. In a T/R snapshot, three spatial samples areformed, in which the numbering of “11,” “12,” and “13” denoteround-trip signification from the first transmitting element tothe first receiving element, the second receiving element, andthe third receiving element, respectively. Note that the loca-tion of the spatial sample can be approximately taken as anequivalent phase center that is positioned midway between theseparate transmitting and receiving elements [27], [39], andit is defined as the location of the virtual element. Hence,we can obtain three data channels in multiple T/R snapshots.Fig. 1(b) shows an MPC-SAR array for the purpose of HRWSstatic-scene imaging. Similarly, in a T/R snapshot, it receivesthree spatial samples. However, they are jointly processed, anda virtual channel is reconstructed for the MPC-SAR system.To simultaneously achieve GMTI and static-scene imaging in HRWS mode, VMC can be divided in a manner shown inFig. 1(c). The numbering of “21,” “22,” and “23” denotesround-trip signification from the second transmitting elementto the first receiving element,the second receiving element,and the third receiving element, respectively. The low realPRF ensures no range ambiguity in wide swath. Moreover, ineach virtual channel, temporal sampling is replaced with spatial sampling, and this overcomes the contradiction between wideswath and high azimuthal resolution. In addition, the unitedprocessing among the VMCs can realize detection and imagingfor the ground moving target in HRWS mode. It is noticed thatalthough a MIMO-SAR array in Fig. 1(c) is used to illustratethe VMC concept, the VMC can also be reconstructed by theexisting along-track multichannel SAR array at the price ofmore receiving elements.
First, the three virtual channels are gen-erated as shown in Fig. 1(c). Then, the strong ground clutteris suppressed by the displaced phase center antenna (DPCA)technique. Second, the interferometric phase information of thetwo cancelation channels after clutter suppression is extractedand used to estimate the initial location of the moving target. Code Shoppy In theory, the real main peak and the false peaks have thesame interferometric phase. Therefore, the mean of multipleinterferometric phases can be used to improve the locationprecision. Third, Doppler centroids corresponding to the realmain peak and false peaks are taken as candidates to betested. Together with the initial location information, a set ofradial velocity is obtained. Then, the phase error compensationfunction is constructed. The image entropy or image contrastis taken as the criterion, and the 2-D real velocity is unitedestimated. Finally, the multiple estimated parameters of thetarget are used to compensate for the error signal and constructthe azimuthal matched filter of the moving target. Eventually,this accomplishes the focused image.
