Dual-polarized filtering antennas and arrays for base stations

As the spectrum becomes increasingly crowded, reducing interference and increasing spectral efficiency have become paramount. In this context, the integration of dual-polarized filtering antennas has emerged as a pivotal solution in modern base station design. By employing two orthogonal polarizations, these antennas mitigate signal degradation caused by multipath interference, reflections, and polarization mismatch. This results in improved signal quality, increased spectral efficiency, and better overall network reliability. The filtering capability further enhances the antenna's performance by minimizing interference from unwanted signals and ensuring cleaner communication channels.

This thesis introduces several innovative methodologies for designing wideband/dual-band dual-polarized filtering antennas. A series of high-performance dual-polarized filtering antennas is presented based on these novel design methods, meeting a diverse range of requirements. Specifically, two dual-polarized filtering antennas are presented for 2G/3G/4G/IMT applications. The first one exhibits wideband characteristics, a steep roll-off, and a high level of out-of-band gain suppression, while the second one emphasizes wideband capabilities with a high out-of-band rejection level. For 5G sub-6 GHz applications, two antennas are designed based on the multipath coupling method. Two different dual-mode resonators are used in these two designs separately to enhance their impedance bandwidths and introduce radiation nulls. In the context of the interleaved dual-band array antenna design, the Multiple Folded Dipole Antenna (MFDA) is analyzed for the first time. This analysis leads to the proposal of a dual-polarized low-pass filtering antenna with high out-of-band gain suppression level and low cross-band scattering. By combining it with four dual-polarized high-pass filtering antennas featuring a high roll-off rate, an interleaved dual-band dual-polarized array antenna is realized for base station applications.

To validate the design principles, all designs were simulated using full-wave electromagnetics simulation software, followed by fabrication and measurement. The measured results aligned well with the simulated results. These high-performance dual-polarized filtering antennas show promising potential for both current and future-generation base station applications.