Broadband dual-polarized antennas with high port isolation for portable devices

A broadband multiple-input-multiple-output (MIMO) antenna with a small size of 170 × 187 mm² is investigated. By placing the two circular planar-monopole (PM) antenna elements perpendicularly, a good isolation is achieved. In addition, by adding two L-shaped stubs and embedding a slit on the ground plane, the isolation and bandwidths of the two perpendicularly placed antennas are improved. More specifically, a triple microstrip transition between the port and the printed circular disc is introduced to enhance the bandwidth. To verify the design, a prototype is manufactured. The measured results show that the MIMO antenna has an impedance bandwidth of 117.6% (0.7-2.7 GHz) for VSWR ≤ 2 and a low coupling of less than -15 dB, making it a potential candidate for portable UWB applications.