Design and Analysis of an Ultraminiaturized Frequency Selective Surface With Two Arbitrary Stopbands

The paper proposes a new design and its analysis of a 2.5-D ultraminiaturized frequency selective surface (FSS) with two arbitrarily and independently adjustable stopbands. These two stopbands can be adjusted very far away or combined to a single wideband. This new FSS consists of only one dielectric layer printed on both sides with refined meandering-lines connecting vertical via arrays. By applying the proposed approach with an exactly equivalent circuit and closed-form equations, four representative prototypes are demonstrated. The first one has two distant stopbands, which high-to-low resonant frequency ratio can be as large as 6.2. The second one shows that its unit-cell size can be highly reduced to only 2.8% of the free space wavelength at the lower resonant frequency. The third one has a wide stopband, having a fractional bandwidth up to 75.7%. The final one meets the specification of 2.4-GHz and 5-GHz wireless local area network application. The simulated and measured results both validate the FSS performance and demonstrate its excellent versatility never found in literatures before.