A Generalized Circuit Model for Designing Multiband Filtering Antennas with Specified Bandwidth and Arbitrary Order

In this article, we have proposed a novel generalized theoretical model for designing multiband filtering antennas. Based on the proposed theoretical model, we can achieve filter antennas with any number of passband, arbitrary order, and specified bandwidth. Our theoretical model is built upon the coupling matrix, enabling the direct synthesis of multiband filtering antennas with coupling structures. To validate the correctness of our proposed theory, we synthesized a four-passband, fourth-order filtering antenna at the theoretical level and implemented a dual-band third-order example based on Substrate Integrated Waveguide (SIW) technology. The simulation and test results both indicate the credibility and feasibility of the theory we proposed.