Miniaturized FSS With Ultrawide Out-of-Band Suppression Based on Parallel-Plate Capacitor

In order to solve the problem of poor ultrawide out-of-band suppression performance of existing filtennas. In this letter, a novel design method of miniaturized frequency selective surface (FSS) with ultrawide out-of-band suppression is investigated. Parallel-plate capacitor (PPC) structure is introduced into a basic nonresonant bandpass FSS to construct an equivalent series LC circuit with a low Q factor. The low-Q PPC resonator effectively increases suppression bandwidth by stronger interlayer coupling. The large value of PPC is also beneficial for the miniaturization and stability of passband. Finally, the unit size and thickness of the modified FSS are all reduced to 0.06λ0 (3 mm), which totally avoids the appearance of a grating lobe under 50 GHz. The −1 dB passband of our design is stable in 5.3 GHz to 7.4 GHz when the incident angle is up to 45° at both TE and TM polarizations. Simultaneously, the −20 dB suppression band covers 10 GHz to 45 GHz. The measured and simulated results validate great performance of the proposed design.