A Wideband Dual-Polarized Filtering Antenna for Multi-Band Base Station Application

A dual-polarized filtering antenna with wide impedance bandwidth and good rejection level in n78 (3.3-3.8 GHz) and n79 (4.8- 5.0 GHz) bands is realized in this paper. By deftly exciting the inherent radiation nulls of the dual-coaxial-fed dipole antenna, good out-of-band rejection levels can be achieved in both the lower frequency band and the n79 band. Then, by replacing the ordinary dipole arms with split loop resonators, new adjustable radiation null can be obtained in the n78 band. The effective length of the split loop resonator can be changed to conveniently alter this radiation null. To confirm the design principle, a prototype of the proposed design was made and tested. The fabricated prototype achieves a wide impedance bandwidth of 52% (1.69- 2.87 GHz) which can cover all established 1.71–2.69 GHz LTE bands. Besides, the proposed antenna realizes good gain suppression levels at the n78 and n79 bands. The tested mutual coupling between its differential input ports is lower than -40 dB.