Experimental analysis of a polarization reconfigurable antenna for MIMO systems

A compact polarization reconfigurable microstrip U-slot patch antenna is presented. The lengths of the U-slot arms can be changed using PIN diodes, which enables the antenna to switch between right hand circular polarization (RHCP) and left hand circular polarization (LHCP). The measured overlapped bandwidth (|s₁₁| ≤ -10 dB and axial ratio less than 3 dB) is 2.8% centred at 5.25 GHz. The channel of a 2 × 2 multiple-input-multiple-output (MIMO) system with the proposed reconfigurable antennas is measured in both line-of-sight (LOS) and Non-LOS (NLOS) indoor environments. Results show that transmit/receive antennas radiating different polarizations are able to improve the system capacity significantly compared to antennas with the same polarization in an LOS scenario, while the extent of the improvement is reduced in an NLOS scenario.