Experimental Analysis of Pattern and Polarization Reconfigurable Circular Patch Antennas for MIMO Systems

In this paper, we investigate the performance achievable with pattern and polarization multielement reconfigurable antennas in narrowband and broadband multiple-input–multipleoutput (MIMO) systems by means of two-port reconfigurable circular patch antennas (RCPAs). We use field measurements collected in an indoor environment to determine the channel capacity achievable with the RCPAs when used at one or at both ends of the communication link. To conduct this analysis, we use two types of RCPAs: 1) an RCPA with two different antenna configurations, exploiting only pattern diversity and 2) an RCPA with three different antenna configurations exploiting both pattern and polarization diversity. The benefits offered by each state (i.e., excited radiation pattern and polarization) of the RCPAs are investigated in both line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios. The analysis shows the effectiveness of each array configuration in increasing the diversity level of the system and the amount of signal power received in LOS and NLOS communication links. The radiation efficiency and the level of pattern and polarization diversity of each configuration are investigated to explain the performance offered by this class of antennas in MIMO systems. Finally, we show the difference in performance achievable with these antennas when employed in narrowband or broadband communication systems.