Isolation Enhancement in Dual-Band Monopole Antenna for 5G Applications

This brief presents a novel design of high-isolation dual-band antenna with a close distance for 5G applications. The proposed antenna consists of two symmetrical monopole antenna elements. Two resonance frequencies of the monopole antenna are independently tunable. The defected ground structure (DGS) and grounded branches are loaded to reduce mutual coupling of the lower band by changing the current distribution on the ground plane. And a T-shaped parasitic element is placed between the two antenna elements. The parasitic element introduces an inverse path for mutual coupling cancellation, which greatly increases the isolation of the higher band. As a result, the proposed antenna achieves 5G dual-band of 3.409-3.601 and 4.76-5.04 GHz (S11S22<-10 dB, S12S21<-26 dB). Compared with the single monopole antenna, the bands of the proposed antenna don't shift and the impedance matching is improved. With the decoupling structure, the isolations are -29 and -41.4 dB at 3.5 and 4.85 GHz, respectively. In addition, the proposed antenna also has the advantages of small size, more flexibility, and simple structure.