Design and Synthesis of a High-Selectivity and Wide Stopband Suppression Filtering Antenna With Symmetric Coupling Structure

A fourth-order high selectivity and wide stopband suppression filtering antenna with symmetric coupling structure is presented. By incorporating resonant units with different structures, harmonics are effectively suppressed due to the resonators' identical fundamental mode and distinct second-order harmonics. By introducing of a cross-coupling path, two controllable radiation nulls are achieved, further enhancing the antenna's selectivity. Additionally, the symmetric coupling structure is employed to minimize cross-polarization. Finally, the theory of coupling matrix is utilized in the synthesis of filtering antenna, and the relevant physical parameters are obtained. The results demonstrate that the proposed filtering antenna exhibits a bandwidth of 2.40-2.66 GHz for |S11|