Compact Dual-Band SISL Filtering Antennas With High Selectivity Based on Dual Gap-Coupled Patches

In this article, two compact dual-band substrate integrated suspended line (SISL) filtering antennas with high selectivity based on dual gap-coupled patches are proposed. By using a quasi-I-shaped feedline, etching longitudinal slots on two patches placed symmetrically, and connecting a metal strip with both patches through metallized vias, three radiation nulls (RNs) are generated in the stopband. Thus, an excellent dual-band SISL filtering antenna with broadside radiation is achieved, resulting in high selectivity and deep stopband rejection. To further integrate filtering response and dual band with different radiations, a dual-band SISL filtering antenna with broadside and bidirectional beams is realized. Two RNs are introduced near the upper passband with bidirectional beams by folded C-shaped slots and parasitic strips, and the bidirectional beam is formed by inverted currents on both patches. Moreover, by connecting a T-shaped metal strip with both patches through metallized vias, an extra RN is acquired near the lower passband with broadside beams. Therefore, both sharp roll-off and different radiation in the dual band are achieved. The operating mechanism of both designs is analyzed. Two prototypes are fabricated and tested, and good agreement between simulated and tested values is observed.