A Novel Log-Periodic MIMO Antenna for UWB System

A novel log-periodic multiple-input-multiple-output (MIMO) antenna array for ultra-wideband (UWB) system in a size of 195×195×45 mm3 is proposed. There are eight antennas in this array: four horizontal antennas are placed orthogonally on a FR4 substrate and other four vertical antennas insert into corresponding slot etching on the diagonal of FR4 substrate to obtain beam switching and dual-polarized characteristics. In addition, all eight antennas share a common square ground on the back of substrate and feed by micro-strip line. Results show that the designed MIMO antenna exhibits a good impedance match with S
₁₁
<; -10 dB, high coupling isolation better than 40 dB, average peak gain of 6.5 dBi and envelope correlation coefficient (ECC) <;0.005 cover the whole UWB range (3.1-10.6 GHz).