A Frequency Selective Surface With Miniaturized Elements

TLDR

The proposed FSS can be fabricated with standard printed‑circuit technology on both sides of microwave substrates, similar to traditional FSSs. The authors introduce a new bandpass frequency selective surface that employs sub‑wavelength resonant dipole and slot elements. The surface consists of a periodic array of capacitive metallic patches separated by thin air gaps and backed by a matching inductive wire mesh, creating a localized resonant structure that enables flexible spatial filtering of arbitrary wave phasefronts. Cascading these miniaturized‑element FSSs yields arbitrary multipole or multiband responses, with one‑pole designs showing reduced sensitivity to incident angle, and prototype measurements at X‑band confirm excellent agreement between experiment and simulation.

Abstract

We demonstrate a new class of bandpass frequency selective surface (FSS), the building block of which, unlike the traditional FSSs, makes use of resonant dipole and slot structures that have dimensions much smaller than the operating wavelength. This design allows localization of bandpass characteristics to within a small area on the surface which in turn facilitates flexible spatial filtering for an arbitrary wave phasefront. The proposed FSS is made up of periodic array of metallic patches separated by thin air-gaps backed by a wire mesh having the same periodicity (Ltlambda). The array of metallic patches constitute a capacitive surface and the wire mesh a coupled inductive surface, which together act as a resonant structure in the path of an incident plane wave. Like traditional FSSs, the capacitive and inductive surfaces of the proposed FSS can easily be fabricated using printed circuit technology on both sides of microwave substrates. It is shown that by cascading such bandpass surfaces in a proper fashion, any arbitrary multipole filter or non-commensurate multiband response can be obtained. The frequency response of the proposed miniaturized-element frequency selective surface (MEFSS) is demonstrated for various incident angles and it is shown that one-pole designs are less sensitive than two-pole designs to the angle of incidence. Dual band designs are also possible based on two-pole designs, but are more sensitive to incident angle than single band designs because of their larger (in terms of wavelengths) spacing. Prototypes of single-pole and dual-pole MEFSSs are fabricated and tested in a waveguide environment at X-band frequencies and excellent agreements between the measured and simulated results are demonstrated