High-Selectivity Planar Filtenna with Wide Out-of-Band Suppression for Sub-6 GHz 5G Applications

In this paper we introduce a novel planar filter and Filtenna design utilizing capacitive termination microstrip coupled-line resonators and a defective ground structure (DGS). A third-order band-pass filter is designed to operate at 3.5 GHz with a 500 MHz bandwidth and a transmission zero near the passband. Subsequently, the proposed filter is integrated with a power divider and a slot antenna to realize a fourth-order Filtenna, achieving a gain of 3.5 dBi, a radiation null at 4 GHz, and wide out-of-band suppression up to the third harmonic. Extensive experimental validation confirms the effectiveness and potential of the proposed approach for next-generation wireless communication systems.