$4 \times 4$ MIMO Performance of Two Conjoined Dual Wideband Antennas Including the Feedline Effects for 5G Smartphones

Studies of 4 ×4 MIMO performance of two conjoined dual wideband antennas including feedline effects for 5G smartphones are presented. The two conjoined dual antennas provide four wide operating bands for 4 ×4 MIMO operation in 5G band of 3300 MHz ~ 5000 MHz and in 5 GHz-WiFi band of 5150 MHz ~ 5875 MHz. The radiation efficiencies, envelope correlation coefficients, and 4 ×4 MIMO capacities and throughputs of the fabricated antennas with their microstrip feedlines having different spacings are experimentally studied. Results show that when the spacings of the microstrip feedlines become smaller (for example, 0.5 mm in this study), larger bit-error-rates (BERs) in 4 ×4 MIMO transmission are observed, thereby decreasing the MIMO throughputs. The experimental results are presented and discussed.