A Dual-Band, Inductively Coupled Miniaturized-Element Frequency Selective Surface With Higher Order Bandpass Response

We present a new approach for designing dual-band miniaturized-element frequency selective surfaces (MEFSSs) with independent control of the frequencies of operation of each band. The proposed device is composed of 2-D periodic arrays of subwavelength inductive wire grids and capacitive patches separated by dielectric substrates. The structure is built on an inductively coupled MEFSS that uses capacitively loaded dielectric spacers as its main resonators. The two operating bands of this MEFSS correspond to the first and second resonant frequencies of its constituting resonators. By judiciously choosing the locations where the resonators are loaded and the load values, the frequencies of the first and second resonances can be controlled individually. In this way, a dual-band MEFSS with independent frequency bands of operation can be obtained. Using the equivalent circuit model of this MEFSS, a synthesis procedure is developed that can be used to synthesize the dual-band MEFSS from its system-level performance indicators. A prototype of the proposed dual-band MEFSS with second-order bandpass response at each band is designed, fabricated, and experimentally characterized. The measurement results of this device show a stable frequency response with respect to the angle of incidence up to ±45° for both the TE and TM polarizations of incidence.