A Planar Single-Layer Differentially-Fed Dual-Band Dual-Polarized Filtenna Based on Multimode Resonant Structure

A planar single-layer differentially fed dual-band dual-polarized filtenna (DBDPF) with a simple configuration is presented, comprising four driven patches and four parasitic strips. Each driven patch is equipped with the shorting vias to excite its two resonant modes while achieving natural radiation null, thus establishing two operational bands with specific filtering characteristics. Further, the bandwidths of the two bands are expanded by introducing extra two resonant modes from the parasitic strips. Simultaneously, the interaction between the parasitic strips and the driven patches induces two radiation nulls, which effectively facilitates the realization of the dual-band filtering performance of the antenna. The inclusion of a pair of rectangular slots on each driven patch enables the creation of an extra radiation null, thereby further enhancing the antenna’s rejection capabilities. The proposed differentially fed DBDPF was manufactured and experimentally validated. The experimental outcomes indicate its capability to achieve −10 dB fractional impedance bandwidths of 8.3% and 12%, maximum realized gain values of 7.7 and 6.5 dBi, and cross-polarization levels smaller than −44 and −46 dB, in its lower and upper passbands, respectively. Moreover, owing to the presence of four radiation nulls, its dual-band filtering response has a high selectivity and strong stopband rejection ability.