Measured Performance of Broadband Frequency Selective Surface to Reduce Return Loss of Dielectric Plate Designed by Matrix Analysis of Equivalent Circuit

Thicknesses of window glasses, radomes, plastic cases of wireless systems are comparable with the wavelength in the millimeter-wave band. Therefore, reflection phase change can not be ignored and return loss is increased. 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. Among various loading positions of the FSS, the FSS inserted at the center of the dielectric plate shows broadband characteristic. Required characteristic of the individual FSS to obtain the desired characteristic of whole structure is calculated by using scattering matrices (S-matrix), transfer matrices (T-matrix) of the dielectric plate and FSS expressed by shunt susceptance. Broadband characteristic was designed by inserting an FSS at the center of the dielectric plate. The performance was evaluated by simulations and measurements.