Investigation of Wire Grid Modeling in NEC Applied to Determine Resonant Cavity Quality Factors

− Numerical computer simulations using the NEC Method of Moments (MoM) code were performed on wire grid models of resonant cavities in order to study how well conductive structures and their surface impedances can be modeled by wire meshes. The resonant cavity quality factor, or Q, was examined due to its high sensitivity to surface impedance. Several half-wave coaxial cavities were simulated using various mesh element sizes. The cavities’ outer conductor radius was varied to obtain different geometries. The quality factor Q was determined from the simulated input impedance spectra. The wire grid model results were compared to well known theoretical and experiment results. Qualitative agreement between simulation, theoretical, and experimental results was achieved for fixed mesh parameters, giving confidence in comparative simulation using the same wire grid meshing parameters. Quantitative agreement of simulation results was achieved through repeated simulation with varying mesh element lengths and extrapolating the simulation results to a conceptual mesh element length of zero. This shows that simulations to determine quantities sensitive to surface impedances can be successfully performed with codes such as NEC.