A Dual-Frequency Miniaturized-Element FSS With Closely Located Resonances

In this letter, we propose a novel dual-frequency miniaturized periodic element for creating a dual-band frequency selective surface (FSS) having closely spaced bands of operation. Using this element and its complementary structure, the dual-bandstop and dual-bandpass FSSs can be simultaneously created without extra effort. The mechanism responsible for the two element resonances and the new way to make these resonances closer is revealed. Based on this revelation, the newly proposed element can be simply and quickly designed to be compact in size and to have two resonances closely spaced. Furthermore, the dual-band FSS created using this element demonstrates excellent resonance stability with respect to different polarizations and incidence angles. Both the bandstop and bandpass FSS prototypes are fabricated and examined. Their measured and full-wave simulated results validate the performance. The created element size is about 8% of the free-space wavelength at the first resonant frequency, and the ratio of the second resonant frequency to the first one is only 1.4.