Transmission properties of metal mesh filters at 90 GHz

Freestanding frequency-selective surfaces with cross-shaped aperture elements are investigated numerically and experimentally. Transmission characteristics of such two-dimensional periodic structures as functions of geometrical sizes are analyzed using the 3D finite element method. These structures find application in modern microwave and terahertz engineering as band-pass metal mesh filters. Utilizing the conjugate gradient method narrowband, 90 GHz filters have been developed and optimized numerically. The results of measurements carried out in the present study agree well with the obtained theoretical data. It is shown that some parameters of such metal mesh filters can be improved by the proper selection of structure periodicity. A single-layer filter with a fractional bandwidth of 5.3% and an insertion loss of − 0.5 dB at the central frequency is demonstrated.