Broadband Vector Potential Dyadic Green's Function and Normal Modes in 3-D Cavity of Irregular Shape

A hybrid spatial-spectral method for rapid and broadband calculation of the vector potential normal modes and dyadic Green's function (GF) inside the cavity of irregular shape is presented. In the broadband method of simulation, the normal modes of the irregular cavity, which are independent of operation frequency, are first computed through a linear eigenvalue problem based on a hybrid representation of the regular (rectangular) cavity. The method is based on the extraction of the singularity of the GF that results in a rapidly convergent hybrid spatial-spectral expansion of the GF. The method is applied to a V-grooved cavity to obtain the vector potential GF inside the cavity, and the results are shown over a broad range of frequencies. The results of the hybrid method are in good agreement with that of direct method of moment (MoM), while the hybrid method is much more efficient than direct MoM as the latter requires the computation at one frequency at a time.