Parametric study and synthesis of 60‐GHz Fabry–Perot resonators

The analysis and the synthesis of plane‐parallel Fabry–Perot (FP) resonators, illuminated by a normally incident plane wave, are investigated theoretically and experimentally in the 60‐GHz band. The reflecting mirrors are inductive metal meshes with square apertures. The frequency response of symmetrical and asymmetric FP cavities is studied (a) approximately with the transmission‐line theory (TL), and (b) and rigorously with the Finite‐difference–time‐domain (FDTD) technique combined with periodic boundary conditions. Then, the inverse problem is solved with the use of an iterative procedure based on the FDTD method. In particular, it is shown theoretically and checked experimentally that the thickness of the cavity is the most critical parameter in the design, although the grid dimensions enable a precise adjustment of the module and of the phase of the internal reflection coefficients.