Compact Multi-user Wideband Mimo System Using Multiple-mode Antennas

A complete multiple-input multiple-output (MIMO) communication system with orthogonal frequency-division multiplexing (OFDM) based on multiple excitation modes for a single circular microstrip antenna is introduced. Traditional diversity techniques such as spatial diversity by means of a linear antenna array or polarization diversity by means of a crosspolarized antenna array may prove to be unsuitable in the case of severe restrictions on antenna size and spacing. A single microstrip antenna employing multiple modes is shown to be comparable to conventional antenna arrays at a much lower cost in terms of size and spacing in an urban micro-cell setting as defined by the Third-Generation Partnership Project (3GPP) standards body. The throughput performance and signal detection of multimode antennas in flat and frequency-selective fading environments is examined subsequently. Mathematical expressions for the increase in capacity and diversity using an array of multimode antennas are derived thereafter. Finally, a novel space-pattern diversity array is analyzed to determine theoretical limits of capacity and diversity gain over traditional spatial MIMO diversity.