Electromagnetic analysis of wires with joints using a hybrid meshless-moments technique

Abstract

This paper presents a fast and accurate hybrid method to analyze radiation of and scattering from conducting wire structures. The proposed technique is based on meshless method (MlM) and method of moments (MoM). First, the electric field integral equation (EFIE) is broken into two parts, integral and differential parts. In this paper, we use smooth meshless basis functions in evaluating the differential part and conventionally employ pulse basis functions in estimation of the integral part, given by closed-form expressions. We call this new technique, advanced meshless method (AMM) and use it to analyze wire structures such as helix and straight dipole antennas. Next, we investigate structures that include two wires connecting at a joint point, such as a helical dipole antenna that is composed of a quarter-wavelength dipole, connected to two helical wires at both its ends and also a folded dipole antenna that has two half-wavelength dipoles connected by two small half ring wires. We propose a new hybrid meshless-moments technique (MMT) which treats separate wire parts like the helical wire, half ring wire, and straight dipole parts by the AMM and the joint or connection parts by the MoM. The interactions between different parts are then taken into account by calculation of the near-field integral equations. Various comparisons between AMM and MMT results with those of a conventional MoM confirm that while accuracy is fixed the AMM and MMT are at least 10 times faster than MoM. The main feature of the hybrid MMT method is its computational efficiency in analyzing electrically large problems. As an example, extinction cross section of a chaff cloud composed of a large number of randomly placed and oriented helical particles as a function of frequency is efficiently computed by the hybrid MMT to show its capability in fast and accurate calculation of a complex medium dispersion.