Port Isolation Method for MIMO Antenna in Small Terminals for Next Generation Mobile Networks

This paper presents a practical method to increase the isolation between two ports of a Multiple Input Multiple Output (MIMO) antenna for mobile hand-held devices. The method consists in a connecting strip containing lumped components placed in between the low impedance zones of the two antennas. The lumped components modify the impedance of the connecting strip so that, together with the mutual coupling impedance, it acts as a band-stop filter between the two ports. As a consequence, the efficiency due to scattering parameters almost doubles and the envelope correlation coefficient decreases dramatically. Furthermore, the use of lumped components makes this method less susceptible to the presence of other components in the mobile device or the user. This method has been verified on two antenna configurations, through simulation and measurements.