Capped Dielectric Inserted Perforated Metallic Plate Bandpass Frequency Selective Surface

A capped dielectric inserted perforated metallic plate is proposed to design wide-bandpass frequency selective surface (FSS). The proposed structure is using the conventional perforated metallic plate with certain thickness inserted by a series of capped circular dielectric resonators, which satisfies tight mechanical requirements of applications such as huge dichroic mirror. Comparing with the conventional perforated metallic plate, it exhibits much more stable frequency response under oblique incidence of wide angles. An equivalent circuit modal is presented using the even-odd mode method, and the calculated frequency responses are discussed with variation of different parameters and they are in good agreement with the full-wave simulated results. Finally, an FSS is designed based on the discussed structure. The FSS is tested, and the measured frequency responses agree well with simulated ones. Measurements show that the minimum insertion loss is 0.31 dB at the two transmission poles under normal incidence, and insertion loss is 0.5 dB at the center frequency of the passband. The fractional 3 dB bandwidth is 20% under the normal incidence. In addition, the wideband filtering performance for both TE and TM polarizations can be obtained under various oblique incidence angles up to 40°.