Abstract
This paper presents a polarization insensitive frequency selective surface (FSS) based on concentric ring slots with five closely spaced passbands. The proposed FSS unit cell contains five ring slots coupled with a supplementary innermost ring slot. The close band response within the first five transmission bands is achieved by the influence of the modified geometry obtained with the inclusion of the sixth ring slot. This added ring slot causes the appearance of a stopband, due to the conductive ring between the fifth and the sixth ring apertures, and a passband produced inherently by the sixth ring aperture. The effect of the additional stopband and passband in the FSS response has been investigated in the paper. Full-wave simulations reveal that a modified geometry with proper sizes effectively enables the close band response of the pentaband FSS. To validate the proposed approach, a 729-element penta-bandpass FSS prototype operating at millimeter-wave frequencies has been designed, fabricated, and tested. Experimental results in a free-space measurement setup indicate resonances at $f_{1} =26.7$ , $f_{2} =29.8$ , $f_{3} =33.6$ , $f_{4} =38.1$ , and $f_{5} =44.2$ GHz, with resonant frequency ratios of $f_{2} / f_{1} =1.12$ , $f_{3} / f_{2} =1.13$ , $f_{4} / f_{3} =1.13$ , and $f_{5} / f_{4} =1.16$ . This FSS demonstrates an extremely low ratio of the highest and the lowest resonant frequencies ( $f_{5} / f_{1} =1.66$ ) for a penta-band operation. This polarization insensitive FSS demonstrates good performance at oblique angular incidence for elevation angles up to 45°.
Highlights
Frequency selective surfaces (FSS) are periodic arrays, commonly in two dimensions, that are composed of geometric elements such as patches or slots that are typically printed on a dielectric substrate
Martinez-Lopez et al.: Close Band Spacing Pentaband FSSs Based on Concentric Ring Slots. It is worth mentioning some applications of the multibandpass FSS such as preventing electromagnetic interference (EMI) between radar and satellite communication antennas [3], electromagnetic architecture of buildings [4], [5], band isolation in systems operating in concurrent mode [6], and coupling reduction between multiband Multiple-Input Multiple-Output (MIMO) antennas [7], [8]
It is observed that the electric field and surface current intensities are higher at the fifth resonance for the case of the unit cell with the supplementary ring slot
Summary
Frequency selective surfaces (FSS) are periodic arrays, commonly in two dimensions, that are composed of geometric elements such as patches or slots that are typically printed on a dielectric substrate. Martinez-Lopez et al.: Close Band Spacing Pentaband FSSs Based on Concentric Ring Slots It is worth mentioning some applications of the multibandpass FSS such as preventing EMI between radar and satellite communication antennas [3], electromagnetic architecture of buildings [4], [5], band isolation in systems operating in concurrent mode [6], and coupling reduction between multiband Multiple-Input Multiple-Output (MIMO) antennas [7], [8]. Further to the previous efforts reported in the literature, this work proposes a novel mechanism to enable the close band response by adding a supplementary innermost ring slot that resonates beyond the operating frequencies of the FSS.
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