MIMO Cube Formed of Slot Dipoles

This paper provides experimental and implementation details for various forms of multiple-input multiple-output (MIMO) cube antennas. Slot dipole antennas are used as basic elements of these MIMO antennas. Experimental results show that especially at higher frequencies of various wireless applications the additional loss of the printed antennas increase and therefore implementation of such antennas not always possible above 1-2 GHz. The suggested type of basic antenna elements provide almost lossless realization on cheap metallic plate. The two prototype are simulated, optimized and measured for 4.5-4.6 GHz. Coupling between dipoles are also measured and presented. The cube antennas exhibit an impedance bandwidth (VSWR les 2) of 18% and 7%. Results of simulations show that the theoretical capacity due to mutual coupling between MIMO antennas is lower than for implemented antennas with mutual coupling for cube side lengths less than about 0.3 lambda. For the prototype antenna the S-parameter isolation between ports below -35 dB over a bandwith of 300 MHz and therefore excellent MIMO antenna can be formed without capacity degradation.