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A design method for a miniaturized small resonant aperture by modifying a ridge structure is presented, and its performance is verified experimentally. The proposed miniaturized aperture was designed by deforming the straight ridge structure of an H-shaped aperture with a two-step ridge of different lengths and widths, which resembles the capacitor symbol shape of the electric circuit. Experiment results show that the resonant frequency of the proposed aperture decreases from 5.06 GHz to 2.565 GHz (49.3%) compared to the conventional H-shaped aperture. Its transmission cross section increased by 3.78 times, and the aperture length-to-wavelength ratio is reduced to 0.09.

Abstract:The transmission characteristics of a frequency selective surface (FSS) consisting of small resonant circular apertures with a ridge are related to the transmission cross section of a single ridged aperture, and the performance is verified experimentally. The FSS structure with a ridged circular aperture has a lower resonant frequency, enlarged fractional bandwidth, and a larger wavelength-to-periodicity ratio compared to an FSS with a conventional circular aperture. Experiment results show that the resonant frequency of the proposed FSS structure can be lowered from 13.98 GHz to 7.30 GHz (47.8%) by adding the ridge. Keywords: frequency selective surface, small resonant aperture, ridge, band pass filter, lower resonant frequency Classification: Microwave and millimeter-wave devices, circuits, and modules References

In this paper, the electromagnetic wave transmission through a ridge-loaded small circular aperture is considered. The transmission problem when a plane wave is normally incident on the aperture in an infinite conducting plane is solved by a method of moments(MoM). From the results for the transmitted power and the patterns of radiation from the aperture, the transmission characteristics of a small sub-wavelength circular aperture, a ridge-loaded circular aperture, and a half wavelength slot are compared. In addition, the theoretical study is verified through the experiments for the apertures fabricated on an Flexible Printed Circuit Board(FPCB), which shows fairly good agreements with the simulated results.