A Full Design Perspective of Port Decoupling for MIMO Antennas: Preservation of Radiation Pattern

Whereas most studies of decoupling methods in antenna designs are limited to port isolation, this article additionally investigates the radiation-pattern-decoupling (RPD) method to preserve the radiation pattern in a port-decoupling design. The RPD method introduces shorting vias to obtain a new current component for canceling the coupled current, leaving the original active current on the coupled antenna element. As a result, each element effectively has its own active current only, minimizing the coupling effects on the antenna port and radiation pattern. For demonstration, this RPD method is applied to an multiple-input multiple-output (MIMO) design using broadside microstrip antennas (MAs). Both $1\times 2$ and $4\times 4$ MIMO arrays are considered, with reasonable agreement between the measured and simulated results. Both of the arrays have an overlapping impedance and isolation bandwidth of more than 5%, with the portion isolation higher than 16.5 dB.