Wideband Dual-Polarized Antenna With High Selectivity for 5G Sub-6-GHz Base Station Applications

A dual-polarized antenna with a wide impedance bandwidth and high selectivity is presented for the use of 5G sub-6-GHz base stations. By strategically introducing a novel coupled dual-mode grid structure, two additional resonant modes (one is in-band and another one is out-of-band) as well as two radiation nulls can be obtained to enhance the impedance bandwidth and out-of-band rejection level of the widely used tightly coupled cross-dipole antenna (TCCDA). The two radiation nulls introduced by the grid structure are located at the two edges of the desired frequency band. To further improve the gain suppression level in higher out-of-band, a new radiation null is obtained by symmetrically introducing four T-shaped strips. Apart from these additional radiation nulls, this antenna also exhibits two inherent radiation nulls originating from its feed structure and reflector. The measured results demonstrate that the proposed antenna exhibits a wide impedance bandwidth of 39.5% (ranging from 3.07 to 4.58 GHz), an excellent isolation of over 31 dB, and a notable out-of-band rejection level exceeding 17.6 and 19.2 dB in the frequency bands of 1.7–2.7 and 4.8–5.0 GHz.