Beamforming Based MIMO Processing with Closely Spaced Antennas

When antennas are placed closely spaced together, the mutual coupling and spatial correlation effects undermine the advantages provided by multiple input and multiple output (MIMO) antennas. In this thesis, we compare and analyze the performance of digital beamforming, fixed radio frequency (RF) beamforming and element based patterning with closely spaced antenna systems. In the case where only one RF-chain is available, we have demonstrated performance improvements using RF beamforming-based MIMO processing instead of element-based MIMO processing with closely spaced metamaterial antennas. The result indicates that even without mutual coupling, antenna based MIMO processing is greatly impacted when moving from rich to correlated scattering environments. In the second half of the thesis, we investigate the switch and examine receiver combining (SEC) technique. We derive the switching rate of SEC and show that even though it has the same outage probability as traditional selection combining, it has a significantly lower switching rate.PMA