New closed-form Green´s functions for microstrip structures based on Ge-Esselle´s method

In this paper, the new closed-form Green´s function method is used to calculate the microstrip Green´s functions. In the improved method, the surface-wave poles are first extracted using a recursive contour integration method. Then, the remainder is approximated by a series of complex exponentials using the Prony´s method or the GPOF along the extended rooftop shaped path in k_ρ-plane. Subsequently, an analytical identity is employed to obtain the new spatial-domain Green´s functions. The numerical results show that the improved method can accurately and efficiently calculate the fields for both near and far regions.