Compact Finite Difference Time Domain Absorbing Boundary Conditions for Electrically Large Waveguide Modeling

Abstract

This work extends a previous effort in optimizing the compact finite difference time domain algorithm for modeling electrically large waveguides by investigating the effect of their electrical size on perfectly matched layer absorbing boundary conditions. Sensitivity analysis is conducted via an optimization procedure where actual finite difference time domain simulations serve as input, and optimum perfectly matched layer parameters serve as output. This analysis affirms a critical need to vary the perfectly matched layer parameters, as the waveguide's operating frequency renders it electrically large. Both uniaxial and convolutional perfectly matched layer formulations are investigated, and analysis is extended to a high-order form of the compact finite difference time domain algorithm, with a further outgoing wave absorption of typically 20–40 dB being achieved.