Wideband Dual-Polarized Filtering Antenna for Base Station Applications

A compact wideband dual-polarized filtering antenna based on tightly coupled cross dipoles is presented in this letter. The enhancement of impedance bandwidth is realized by introducing four impedance equalizers to equalize the input resistances of the two inherent resonant modes of the tightly coupled cross-dipole antenna. The enhancement of the selectivity is realized by introducing two radiation nulls in 5G sub-6 GHz n77 and n79 bands. The radiation null in the n77 band is obtained by introducing the cross strips in the center of the antenna. The radiation null in the n79 band is achieved by the introduction of open-end branches. The manipulation of their key parameters allows for independent control over both radiation nulls. The validity of the antenna's design principle was confirmed by carrying out fabrication and measurements. The results obtained showcase the antenna's broad fractional bandwidth of 63.4% and exceptional port isolation of 31 dB. High out-of-band rejection levels in the n77 and n79 bands are also obtained. In addition, since the whole radiator of the presented antenna is coplanar, it offers the advantage of a simple structure and convenient manufacturing, making it highly suitable for use in base stations operating across multiple bands.