A Filtering Antenna Using Transversal Coupling Topology

In this letter, a coupling scheme for the realization of filtering antennas is introduced. This coupling scheme allows the filtering antenna to realize a filter-like reflection coefficient using an all-radiator structure. Instead of cascading resonators one by one in a ladder manner, in a transversal filtering antenna (TFA), all the radiative resonators are coupled to the source simultaneously. The impedance and radiation behaviors of these subantennas (SAs) can be designed individually. So, the performance of these filtering antennas has much lower sensitivity to their physical structure than conventional cascaded designs, which makes the design of such a filtering antenna much easier. Besides, this topology can realize out-of-band gain zeros without using any parasitic elements or cross-coupling structures. The locations of these gain zeros can be controlled by simply changing the lengths of each SA. To the authors’ knowledge, this is the first time that a transversal filtering antenna with all resonators radiative is presented. For validation, some transversal filtering antenna designs with different coupling topologies are introduced to prove the concept and show their advantages. A third-order prototype is fabricated and measured for demonstration, showing good agreement between the simulated and measured results.