Fast analysis of electromagnetic scattering problems of three-dimensional(3D) objects over a wide incident angle is always a difficult problem in computational electromagnetics.Previous study shows that introducing compressed sensing(CS)technique into method of moments(MoM)can reconstruct currents over all incident angles from only several measurements

thereby it can improve the computation efficiently.For the purpose of acquiring total number of measurements and choice of sparse transform when using compressed sensing

a priori technique based on physical optics(PO)is proposed in this paper.By this technique

sparsity of the projection of current coefficients over the wide angle and the number of times of measurement can be pre-estimated

thereby apriori knowledges can be provided for the fast algorithm of solving scattering problems over a wide angle by CS(especially the choice of sparse bases)

thus the fast algorithm can be applied into engineering practice in a real sense.