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 $195\times 195\times 45\mathrm{mm3}$ 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 $\mathrm{s}_{11} < -10\mathrm{dB}$, high coupling isolation better than 40 dB, average peak gain of 6.5 dBi and envelope correlation coefficient $\mathrm{(ECC) } < 0.005$ cover the whole UWB range (3.1-10.6 GHz).