Abstract
An easily assembled 3-D bandpass frequency-selective structure (FSS) is proposed, which exhibits quasi-elliptical bandpass filtering performance with two transmission poles in the passband and wide out-of-band rejection with two transmission zeros for both transverse electric (TE) and transverse magnetic (TM) polarizations. Each unit cell of the proposed FSS consists of back-to-back cascaded ground apertured annular ring resonators, while the ensemble transparent solid circular interior aperture between the resonators serves as a coupling structure, and then a resonator-coupler-resonator module is achieved. The operating principle for this FSS is also explained with the aid of an equivalent circuit model. Moreover, a parametric study is carried out and design guidelines for the proposed FSS are summarized. A design example is fabricated and the frequency responses of the FSS are tested. Measurements show that the frequency performance of the proposed FSS provides a passband with two transmission poles at around 7.2 and 7.9 GHz and a wide stopband with two transmission zeros at around 9.6 and 12.3 GHz under oblique incident wave at theta = 0 degrees and 40 degrees for both TE and TM polarizations. This demonstrates that the proposed structure is an excellent candidate of high-performance dual-polarized FSS with wide stopband rejection.