Loaded N-port Structure for Reconfigurable Compact MIMO Antenna Design Invited Paper

A systematic method for designing reconfigurable compact multiple-input multiple-output (MIMO) antennas is described. This method is based on the analysis of a general loaded N - port structure in beamspace domain and is use-ful in optimizing various compact MIMO antennas for next-generation wireless communication. In this method, multiple streams of symbols are mapped onto a set of orthogonal far-field radiation patterns. Then by finding the required loads, the desired radiation patterns can be excited to transmit symbols. Leveraging this method, in this paper, we focus on two MIMO antenna configurations, including single-radio-frequency (RF) electronically steerable parasitic array radiator (ESPAR) and multi-RF compact antenna, and provide efficient optimization methods to find the optimal MIMO antenna design with load values. Simulation results show that by using the proposed method, the single-RF ESPAR can significantly improve the energy efficiency (EE) while achieving close spectral efficiency (SE) when compared with conventional MIMO antennas. In addition for the multi-RF compact antenna, the mutual coupling can be efficiently suppressed by generating orthogonal radiation patterns at multiple ports and the resulting SE can achieve the channel capacity bound.