A company frequency reconfigurable MIMO antenna with low mutual coupling for UMTS and LTE applications

In this paper, we propose a compact frequency reconfigurable (FR) multiple-inputmultiple-output (MIMO) antenna in a overall size of 51 × 53 × 0.8 mms. The MIMO antenna consists of two symmetrical FR ones using two PIN diodes on ground plane and has a simple bias circuit without capacitor. By switching the PIN diodes, the FR MIMO antenna can operates in the three states covering bands of tte universal mobile telecommunication system (UMTS), of the long-term-evolution (LTE) at 2.3 GHz, and 2.6 GHz with peak gains of 1.55, 1.81, and 0.87 dBi, respectively. A slot is added on the ground plane to achieve a low mutual coupling between antenna elements of less than −20 dB in all operating bands. The process of antenna design as well as calculating desired frequency bands are presented in detail. The antenna is fabricated on FR4 substrate and the simulated S-parameter results of the antenna are in good agreement with measurement results.