پردازش داده و تشكيل تصوير در رادارهاي روزنه مصنوعي دو پايه ﴿BSAR﴾

چكيده انگليسي :

Bistatic Synthetic Aperture Radar Data Processing and Image Formation Mohammad Zamani m zamani@ec iut ac ir 9 20 2011 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisor Dr M Modarres Hashemi modarres@cc iut ac irAbstractDifferent regions of electromagnetic spectrum can be used in remote sensing and earth surface imaging Synthetic aperture Radar SAR using microwave region brings out several benefits including capability toall weather imaging even in fog and cloud day and night imaging without need to external source and highresolution imaging even in long ranges Therefore it is widely used whether in civil or military applications Bistatic SAR BSAR is characterized by different locations for transmitter and receiver There are severalbenefits with respect to monostatic SAR systems like increased reliability and flexibility reducedvulnerability for military applications reduced costs using existing illuminators of opportunity with severalreceive only systems more scattering information acquiring and capacity of forward or backward lookingSAR imaging Even for objects that show a low Radar Cross Section RCS in monostatic SAR one can finddistinct bistatic angles to increase their bistatic RCS All the advantages above are however paid with theprice of increased processing complexity BSAR system geometry can be categorized in the three mainconfigurations the azimuth invariant BSAR with platforms of the same velocity along parallel directions theparallel BSAR with platforms of different velocity and the general BSAR with arbitrary directions andvelocities of transmitter and receiver Degree of complexity to process these configurations increasesrespectively In SAR raw data the energy of a point target spreads in both range and azimuth and noinformation can be obtained without further processing Thus processing these raw data and image formationis a significant subject Image formation algorithms can work in time or frequency Time domain methodscan focus BSAR data well however these methods suffer from inefficiency problem Efficiency can beimproved by performing the focusing in the frequency domain Omega k is a known focusing algorithmcharacterized by its precision It is preferred by many SAR researchers because of its capability to processwide apertures and highly squinted cases The Bistatic Point Target Reference Spectrum BPTRS is the basisfor most frequency domain algorithms The accuracy of an algorithm is limited by the accuracy of itsspectrum There are different implementations of an algorithm based on the spectrum used MELBF is anaccurate bistatic spectrum presented recently by Loffeld and his group It can be applied within any imageformation algorithm In this thesis we propose a new method by implementing omega k algorithm based onMELBF spectrum that is applicable for all bistatic configurations We present two different approaches basedon accurate Stolt interpolation and efficient approximate interpolation free ISFT First we show the validityof our method in different BSAR configurations Then we show that our method gives better results in termsof image quality measurements compared to an existing omega k algorithm based on ELBF and simulationresults confirms this claim In another contribution we investigated the use of Chebyshev orthogonalpolynomials in deriving the bistatic spectrum As using Taylor and Legendre expansion is reported inliterature we propose to add a third expansion to this group that in some cases gives better results Key WordsSAR Bistatic Image formation Spectrum Omega k Orthogonal polynomials Chebyshev

زماني، محمد

پردازش داده و تشكيل تصوير در رادارهاي روزنه مصنوعي دو پايه ﴿BSAR﴾

طيف , omega-k , چند جمله اي هاي متعامد , چبي شف