A hybrid BEM/WTM/DFT technique for analysis of the EM scattering from open-ended circular cavities with cylindrically periodic terminations

The cavity problem, formulated using a magnetic field integral equation (MFIE), can be solved by the iterative physical optics (IPO) method, the progressive physical optics (PPO) method or the hybrid boundary element method/wavelet transform method (BEM/WTM). In this paper, we focus on open-ended circular cavities with cylindrically periodic terminations. The cavity problem is formulated using an electric field integral equation (EFIE), based on the dyadic Green function technique, instead of an MFIE. The discrete Fourier transform (DFT) technique is applied by exploiting the periodicity of the termination to reduce the original computational size by a factor of N_s with corresponding computational savings of a factor of N_s², where N_s denotes the number of blades in the cylindrically periodic termination. Two kinds of dyadic Green functions are derived to reduce the integral range in the EFIE, thus accelerating the scattering solutions for different cavity applications. The BEM/WTM method is combined with the DFT to obtain sparse impedance matrices that can be efficiently solved using sparse solvers. The proposed hybrid BEM/WTM/DFT technique provides an alternative means of effectively analyzing the electromagnetic (EM) scattering from large-size circular cavities with cylindrically periodic terminations. Numerical results are presented to demonstrate the merits of the method.