ISOLATION IMPROVEMENT IN A DUAL-BAND DUAL-ELEMENT MIMO ANTENNA SYSTEM USING CAPACITIVELY LOADED LOOPS

A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827-853 MHz and the higher band covers 2.3-2.98 GHz. Two prototypes were investigated to access the effect of the isolation mechanism. Measured isolation improvement of 10 dBs was observed in the lower operating band while the improvement in the higher band was approximately 2.5 dBs. The isolation improvement was at the expense of 5% reduction in efficiency. The measured gain patterns as well MIMO figures of merits such as the correlation factor, TARC and MEG were investigated as well.