Analysis and design of cylindrical multilayered MMICs using a unified non-uniform FDTD algorithm

The traditional approach of implementing FDTD techniques is to develop different sets of update relations that accommodate for different computational regions, for example, normal FDTD and absorbing boundary condition (ABC) regions. In particular, when a perfectly matched layer (PML) is used for termination of computational grids, we have to deal with a number of field regions in terms of PML faces, edges, and corners which adds a tremendous work load and complexity to the programming environment. This paper aims to develop an efficient approach to analyze and design cylindrical MMICs. In it, we present a unified non-uniform cylindrical finite difference time domain (NU-CFDTD) algorithm in conjunction with an anisotropic perfectly matched layer (APML) ABC in a stretched-coordinate mapping system. The algorithm uses only one set of update equations to handle all computational regions, no matter if they are normal FDTD or PML regions. We determine a non-uniform grid pattern depending on the circuit density for a specific structure to save computational resources, while remaining satisfactory accuracy. In particular, the present algorithm can characterize different material regions by simply assigning different material parameters.