Application of Ludwig integral combining with SPM in NURBS MOM-PO method for analyzing antenna around electrically large platform

The hybrid method of moments and physical-optics (MOM-PO) based on Non-uniform rational B-spline (NURBS) modeling represented a suitable approach because it´s higher in efficiency and more accurate modeling than Triangle MOM-PO method. However, the reason of the invalidation in existing NURBS MOM-PO method is analyzed in detail in this paper. Ludwig integral combining with SPM (stationary phase method) is utilized to calculate the integral of induced currents for overcoming the invalidation. Thus both the efficiency and validity are ensured. Numerical results demonstrate that accurate results can be achieved in electrically large EM radiation problems by using the present method.