Research On The Spatial Variant Characteristic For Aperture Synthesis Microwave Radiometric Imaging System

As a new array interferometric microwave radiometric imaging systems，aperturesynthesis radiometer (ASR) formed a large physical observation aperture by a thinnedarray of single small-aperture antennas. But new problems are brought out at the sametime, which is the spatial variant characteristic of ASR. Though spatial variantcharacteristic has been studied deeply in many other imaging modalities, it is rarelyreported in ASR imaging system. As the difference of imaging principle, these researchresults can’t be directly applied to ASR. Therefore, it is necessarily to developcomprehensive research on the spatial variant characteristic of ASR. This paper will focuson the cause of ASR spatial variant characteristic, model building of the correspondingspatial variant problem, and the restoration of spatial variant image.Firstly, the state-of-art of ASR and study of the spatial variant characteristic ispresented. The principle of ASR imaging is introduced in detail subsequently. After that,the factors that lead to the decrease of spatial resolution as pixels leave the center of theinversed image are analyzed, simulations prove that the factors of dispersed sampling andfringe washing function are the main cause of ASR spatial variant characteristic and leadto the broaden of ASR main beam. Then the mathematical model of spatial variant imageis given out. Finally, by the use for reference of spatial variant problem converting tospatial invariant problem, least square restrict restoration model is presented andsuccessfully applied to the restoration of spatial variant image of ASR by the use ofregression estimation. Simulations and experiments prove that this method can effectivelymeliorate the image quality of ASR.