An efficient method for highly oscillatory physical optics integrals

In this work, we use the steepest descent path (SDP) method in the complex analysis to calculate the highly oscillatory physical optics (PO) integral with quadratic phase and amplitude variations on the triangular patch. Compared with traditional approximate asymptotic expansion approach, our method has significantly improved the PO integral accuracy by one to two digits (10^-1 to 10^-2) for evaluating the PO integral. Moreover, the computation effort for the highly oscillatory integral is frequency independent.