Design of frequency selective surface by matrix transformation of layer structure to reduce return loss of thick dielectric plate

Thicknesses of window glasses, radomes, plastic cases of wireless systems are comparable with the wavelength in the millimeter-wave band. The reflections from the dielectric plate surfaces are canceled out of phase when the thickness is identical to a half of the wavelength. However, they are not canceled at any other frequencies except integer multiple of a half wavelength. Therefore, return loss is a serious problem in the millimeter-wave band. A frequency selective surface (FSS) loaded to the dielectric plate controls reflection amplitude and phase, thus, return loss is canceled for various dielectric thickness and frequency. A complex scattering matrix (S-matrix) of FSS is represented by only reflection amplitude |S 11 | from the condition of zero thickness of FSS expressed by shunt suceptance. The total reflection is calculated by converting S-matrices of FSS and a dielectric plate to a transfer matrices (T-matrix) and synthesizing them. We propose to find the required characteristics of FSS from the desired characteristic of whole structure. Broadband characteristic was designed by inserting FSS at the center of the dielectric plate.