MIMO Antennas for Mobile Handsets

This letter presents a pair of printed MIMO antennas for mobile handsets. With each antenna being a coupled fed monopole in a meandered shape, it is capable of covering GSM 1800/1900, UMTS, WLAN, and LTE frequency bands. The antennas are oriented diagonally at the nongrounded portion of the circuit board. The substrate used for the circuit board is FR4 with relative permittivity of 4.4 and loss tangent of 0.02. The overall volume of the circuit board is 110×65×0.8 mm³, with each antenna occupying an area of 24×14.5 mm². To improve the isolation between antennas, dual decoupling structures consisting of ground slots and inverted L ground branches that extend into the nongrounded portion are etched diagonally on the bottom layer of the substrate. The isolation achieved is better than 15 dB over all the frequency bands covered by each antenna leading to an envelope correlation coefficient of less than 0.02. The simulation and measured results are in good agreement.