Investigation of UPML in the FDTD Analysis of Planar Microstrip Structures

Planar microstrip structures are analyzed with a three dimensional finite difference time domain method (FDTD). Uniaxial anisotropic perfectly matched layer (UPML) absorbing boundary condition is utilized to truncate the FDTD lattices. In order to validate the numerical model, scattering parameters of a line-fed rectangular patch antenna and a low-pass filter are investigated. Simulation results are compared with measurements given by published works. Moreover, efficiency and convergence of FDTD-UPML are also compared with Mur's absorbing boundary condition. Simulation results demonstrated that FDTD-UPML needs less total mesh and convergences faster than Mur's ABC. The method presented in this paper is valid for arbitrary microstrip geometries, such as microstrip circuits and microstrip antennas.