Analysis of Inductive Waveguide Microwave Components Using an Alternative Port Treatment and Efficient Fast Multipole

This paper presents a simple and alternative approach for the analysis of inductive waveguide microwave components. The technique uses a surface integral equation formulation, in which the contours of the waveguide walls and of the inner obstacles are all discretized using triangular basis functions. In order to avoid the relative convergence problem of other techniques based on mode matching, an alternative port treatment is used. The technique is based on the application of the extinction theorem using the spatial representation of the Green's functions in the terminal waveguides. In addition, the Fast Multipole Method is proposed in order to reduce the computational cost for large problems. Different complex structures are analyzed, including microwave bandpass filters with elliptic transfer functions, waveguide bends and T-junctions. Results show the high accuracy and versatility of the technique derived.