Dual-Polarized Antenna with Integrated Low-Pass Filtering for Base Station Applications

In this paper, we propose a novel dual-functional device that integrates a dual-polarized filtering antenna and a lowpass filter, specifically designed for base station applications. The proposed device operates as an antenna with a -10 dB impedance bandwidth of 1.68-1.89 GHz, covering the 5G n3 band. It achieves a maximum in-band gain of 9.05 dBi and a radiation efficiency exceeding 93%, with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 45^{\circ}$</tex> dual polarization, which is crucial for base station operations. Additionally, the integrated filtering circuit provides more than 20 dB out-of-band rejection in the lower frequency band and over 15 dB in the upper frequency band, thanks to a parasitic patch introducing a radiation null at 2.12 GHz. As a low-pass filter, the device exhibits a cutoff frequency of 0.96 GHz, with an in-band insertion loss of less than 0.36 dB and stopband suppression exceeding 20 dB. This dualfunctional device can be cascaded with another antenna element operating at frequencies below 0.96 GHz, eliminating the need for additional filtering circuits, thereby significantly saving space and making it an excellent candidate for base station applications.