Wideband and Wide-Angle FSS Using Loop Slotted Hybrid Quarter-Mode Substrate Integrated Cavity With Two Independently Controllable Poles

Abstract

A wideband and wide-angle frequency selective surface (FSS) is proposed in this communication. The periodic element consists of a quarter-mode substrate integrated waveguide (QMSIW) cavity surrounded by two identical loop slots located on the top and bottom layers of the cavity. Two transmission poles and one transmission zero are caused by the fundamental mode in the QMSIW cavity, the slot mode, and the coupling between them, respectively. By precisely tuning the dual-mode configuration, the proposed FSS shows a wide passband with a good transmission efficiency and a rapid roll-off at the high side of the operation band due to the transmission zero. With the QMSIW-based miniaturized elements, the FSS is also insensitive to a large angle of incidence. Thanks to the novel structure, several higher order modes close to the target band are suppressed, making the parasitic passband far away from both sides of the designed band. To verify the advantages, a prototype operated at 10 GHz is fabricated and tested. The measured results show a wide passband performance with the 1/3 dB relative bandwidths of 34%/49% for normal incidence, which agree well with the simulated results. Besides, the 3 dB bandwidth still remains 23% for the incident angle of 60°.