Electromagnetic Wave Scattering from Material Objects Using Hybrid Methods

Abstract

Recent progress in wireless communication systems requires the development of fast and accurate techniques for designing and optimizing microwave components. Among such components we focus on the structures where a set of metallic and dielectric objects is applied. The investigation of such structures can be divided into two areas of interest. The first approach includes open problems, i.e. the electromagnetic wave scattering by posts arbitrarily placed in free space and illuminated by plane wave or Gaussian beam. In these problems the scattered field patterns of the investigated structures in near and far zones are calculated. Such structures are applied to the reduction of strut radiation of reflector antennas Kildal et al. (1996), novel PBG and EBG structures realized as periodical arrays Toyama & Yasumoto (2005); Yasumoto et al. (2004) and polarizers Gimeno et al. (1994). The second approach concerns closed problems, e.g. the electromagnetic wave scattering by posts located in different type of waveguide junctions or cavities. The main parameters describing these structures are the frequency responses or resonant and cut-off frequencies. The aforementioned waveguide discontinuities, as well as cylindrical and rectangular resonators, play important role in the design of many microwave components and systems. Rectangular waveguide junctions and circular cavities consisting of single or multiple posts are applied to filters Alessandri et al. (2003), resonators Shen et al. (2000), phase shifters Dittloff et al. (1988), polarizers Elsherbeni et al. (1993), multiplexers and power dividers Sabbagh & Zaki (2001). One group of the developed techniques used to analyze scattering phenomena is a group of hybrid methods which combine those of functional analysis with the discrete ones Aiello et al. (2003); Arndt et al. (2004); Mrozowski (1994); Mrozowski et al. (1996); Sharkawy et al. (2006); Xu & Hong (2004). The advantage of this approach is that the complexity of the problem can be reduced, and time andmemory efficiency algorithms can be achieved. The aforementioned methods are focused on objects located in free space Sharkawy et al. (2006); Xu & Hong (2004) or in waveguide junctions Aiello et al. (2003); Arndt et al. (2004); Esteban et al. (2002). Here the objects are enclosed in a finite region where the solution is obtained with the use of discrete methods such as finite element method (FEM) Aiello et al. (2003), finite-difference time-domain (FDTD) Xu & Hong (2004) or frequency-domain (FDFD) Sharkawy et al. (2006) methods and method of moments (MoM) Arndt et al. (2004); Xu & Hong (2004). In open problems Sharkawy et al. (2006); Xu & Hong (2004) the relation between the fields in the inner and outer regions is found by calculating the currents on the interface between the regions. 3