Isolation enhancement based on reaction theorem for MIMO antenna system

Isolation enhancement between two closely spaced antennas is achieved based on the reaction theorem. The electric fields cross the slot on the ground is so designed that it generates an equivalent magnetic current source to diminish the effect caused by the electric current source, resulting in a lower magnitude of the S₂₁. This method is very useful for those multiple-input-multiple-output (MIMO) antennas having very close antenna spacing for which the isolator or decoupling elements are difficult to be placed in between. The experimental results agree closely with the simulation results, demonstrating the feasibility of the proposed method.