Dual-Polarized Filtering Dipole Antenna Using a Novel Crossover Ring Filter Structure

This letter presents a different dual-polarized filtering antenna design method by inserting a novel crossover ring filter into a conventional balun-feed dipole antenna structure. The performance of the crossover ring filter structure is first analyzed, revealing that different port selections yield distinct stopband effects. Specifically, exciting the horizontal ports of the crossover structure introduces a stopband at upper frequencies while selecting vertical ports generates a stopband at lower frequencies. Leveraging this phenomenon, two third-order crossover ring structures are orthogonally positioned beneath the radiating arms for dual-polarization operation realization. The integration of this structure enables the antenna to achieve the desired bandpass radiation response. For verification, the proposed antenna was fabricated and tested. The results indicate that the antenna achieves an impedance bandwidth of 1.88 GHz to 2.41 GHz, two controllable radiation nulls, and an out-of-band radiation suppression level exceeding 19 dB. These advantages make it an excellent candidate for base station antenna systems.