A Broadband Filtering Antenna Array for Sub-6 GHz Base Station Applications

In this letter, a broadband filtering antenna array is proposed with two controllable radiation nulls. A square metal parasitic ring is designed to introduce the radiation null. Both a new resonant mode and a radiation null are introduced by slitting the end of the dipole arm and extending it inward. Four metallic reflector walls also significantly improve the out-of-band suppression level. To demonstrate the mechanism, the proposed antenna is fabricated. It has a wide 55% (2.9–5.1 GHz) impedance bandwidth. The out-of-band gain suppression is greater than 16 dBi. A four elements filtering antenna array is developed and fabricated for sub-6 GHz applications. The measured results show that the antenna array can achieve a wide bandwidth of 55% (2.9–5.1 GHz) with an average gain of 11.3 dBi, which satisfies the modern 5G base station applications.