Three-element ultrawideband MIMO antenna based on shared-radiator structures with high efficiency and gain

This letter presents a novel three-port ultrawideband (UWB) multi-input-multi-output (MIMO) antenna that covers the sub-6 GHz (between 1.7 and 6 GHz) frequency band for wireless device applications. The proposed antenna consists of two parts: a dipole and two centrosymmetric slot antennas with shared structures. The radiating arm of the dipole can be reused as the large slot ground without increasing the size. The novel circular slot antenna etched on the radiator and circular microstrip feed line are designed to achieve wide impedance bandwidth. Meanwhile, four chamfers are loaded at the corners of the dipole to further optimize the impedance match in the whole frequency band. The physical dimension of the proposed three-port MIMO antenna is 70 x 45 x 0.762 mm3. Experimental results validate that the reflection coefficient remains lower than -12 dB and the port isolation is better than 12 dB in the entire operational bandwidth without any decoupling network. The measured average peak gains are up to 5.6 dBi for all three ports, accompanied by a radiation efficiency of 90% across the frequency spectrum. With the advantages of simple design, high gain and high radiation efficiency, the proposed three-element MIMO antenna design is well-suited for implementation in UWB applications.