A Conformal FDTD Method With Accurate Waveport Excitation and S-Parameter Extraction

We demonstrate a conformal finite-difference time domain (CFDTD) technique with accurate waveport excitation and S-parameter extraction. We discuss, under the CFDTD framework, object modeling with effective subcell material, impedance calibration for the conformal modeled coaxial feed, waveport mode calculation with a newly developed conformal 2-D finite-difference frequency domain solver, waveport excitation with a modified total field scattered field method, and a modified S-parameter extraction scheme that is compatible with the CFDTD method. Lastly, we present two specific validation cases intended asWe demonstrate a conformal finite-difference time domain (CFDTD) technique with accurate waveport excitation and S-parameter extraction. We discuss, under the CFDTD framework, object modeling with effective subcell material, impedance calibration for the conformal modeled coaxial feed, waveport mode calculation with a newly developed conformal 2-D finite-difference frequency domain solver, waveport excitation with a modified total field scattered field method, and a modified S-parameter extraction scheme that is compatible with the CFDTD method. Lastly, we present two specific validation cases intended as relevant precursors to the inverse scattering application: modeling of the reflection coefficient of a tapered patch antenna and modeling of the transmission coefficient in a probe-fed rectangular waveguide. relevant precursors to the inverse scattering application: modeling of the reflection coefficient of a tapered patch antenna and modeling of the transmission coefficient in a probe-fed rectangular waveguide.

I. Introduction

The finite-difference time domain (FDTD) method originally proposed by Yee has become a widely used tool in the modeling of electromagnetic problems. However, the original FDTD method with staircase mesh has difficulties with accurately modeling curved objects. To overcome this problem, Dey and Mittra [1] proposed a conformal FDTD (CFDTD) algorithm with a modified field update. This method increased the modeling accuracy at the cost of reduced timesteps. To address this issue, Xiao and Liu [2] proposed the enlarged cell technique, while Zagorodnov et al. [3] proposed the uniformly stable conformal scheme. However, both of these methods are more difficult to implement than the conventional FDTD algorithm and require additional computational steps. To address this, Benkler et al. [4] introduced the effective material and effective electric field concept, which implements the CFDTD within the original form of the conventional FDTD algorithm. Up to this point, however, no detailed development of the CFDTD method with waveport excitation and S-parameter extraction has been found in the current literature.