Clarification of issues on the closed-form Green's functions in stratified media

The closed-form Green's functions (CFGF), derived for the vector and scalar potentials in planar multilayer media, have been revisited to clarify some issues and misunderstandings on the derivation of these Green's functions. In addition, the range of validity of these Green's functions is assessed with and without explicit evaluation of the surface wave contributions. As it is well-known, the derivation of the CFGF begins with the approximation of the spectral-domain Green's functions by complex exponentials, and continues with applying the Sommerfeld identity to cast these approximated spectral-domain Green's functions into the space domain in closed forms. Questions and misunderstandings of this derivation, which have mainly originated from the approximation process of the spectral-domain Green's functions in terms of complex exponentials, can be categorized and discussed under the topics of: 1) branch-point contributions; 2) surface wave pole contributions; and 3) the accuracy of the obtained CFGF. When these issues are clarified, the region of validity of the CFGF so obtained may be defined better. Therefore, in this paper, these issues will be addressed first, and then their origins and possible remedies will be provided with solid analysis and numerical demonstrations

Comparative evaluation of absorbing boundary conditions using Green's functions for layered media

Absorbing boundary conditions are comparatively studied using the Green's functions of the vector and scalar potentials for multilayer geometries and general sources. Since the absorbing boundaries are introduced as additional layers with predefined reflection coefficients into the calculation of the Green's functions, this approach provides an absolute measure of the effectiveness of different absorbing boundaries. The Green's functions are calculated using different reflection coefficients corresponding to different absorbing boundaries and compared to those obtained with no absorbing boundary. It is observed that the perfectly matched layer (PML) is by far the best among the other absorbing boundary conditions whose reflection coefficients are available

Numerically efficient analysis of slot-lines in multilayer media using closed form Green's functions

A numerically efficient technique for the analysis of slot-line geometries in multilayer media is presented using closed-form Green's functions in the spatial domain employed in conjunction with the Method of Moments (MoM). The computed equivalent magnetic current distribution on the slot is used to determine the power radiated by the slot and the input impedance. In power calculations, the spatial domain Green's functions are approximated as a power series of radial distance, and the integrals involving the Green's functions are carried out analytically saving considerable amount of computation time

Use of computationally efficient method of moments in the optimization of printed antennas

Derivation of the closed-form Green's functions and analytical evaluation of the method of moments (MOM) matrix entries have improved the computational efficiency of the significantly in the analysis of printed geometries. With this background in mind, an extension of this efficient numerical technique is to incorporate an optimization algorithm and to assess its potential as a computer-aided design (CAD) tool. Therefore, we have employed the Gradient search and Genetic algorithms, in conjunction with the electromagnetic (EM) simulation technique, to a number of representative examples of interest