Patch Array Decoupling Using Spoof Surface Plasmon Polariton

To reduce the mutual coupling between patch array elements in multiple-input-multiple-output (MIMO) antennas, this paper proposes a decoupling method for dual-element patch arrays incorporating a spoof surface plasmon polariton (SSPP) structure, which involves an SSPP between the two patch elements in the middle of the two layers. The SSPP operates in a state of plasma that converts the fast wave into the slow wave, thus, the normal electromagnetic waves cannot propagate along the array substrates due to their high-impedance property. To explain the decoupling principle, the plasma state and the corresponding high impedance characteristic are fully analyzed. The simulations show that the proposed SSPP exhibits a plasma state from 4.8 GHz to 5.3 GHz, and the SSPP structure achieves a high impedance from 4.9 GHz to 5.2 GHz. The mutual coupling of the dual-element has been reduced by about 20dB. Furthermore, the SSPP structure successfully enables plasma mode excitation, as evidenced by its distinctive dispersion properties.