Highly Compact MIMO Antenna System for LTE/ISM Applications

Planar monopole antenna is proposed as the antenna element to form a compact dual-element multiple-input-multiple-output (MIMO) antenna system for LTE2300 (used in Asia and Africa) and ISM band operation. The system can cover a 310 MHz (2.20–2.51 GHz) operating bandwidth, with the total size of 15.5 mm × 18 mm × 1.6 mm. Measured isolation higher than 16 dB is obtained without any specially designed decoupling structures, while the edge-to-edge element spacing is only 7.8 mm (0.08λ at 2.20 GHz). Radiation characteristics, correlation coefficient, and the performance of the whole system with a metal sheet and a plastic housing show this system is competitive for practical MIMO applications. The antenna element is further used to build an eight-element MIMO antenna system; also good results are achieved.