Decoupling of a Three-Port MIMO Antenna With Different Impedances Using Reactively Loaded Dummy Elements

A simple and efficient decoupling technique for a compact three-port multiple-input-multiple-output antenna is proposed in this letter, and the theory of general design procedures is also introduced. A three-port monopole antenna working at 3.5 GHz is used to demonstrate the decoupling mechanism. The high isolation is achieved by introducing two dummy elements terminated with the reactive loads, which ensures lossless decoupling in the case of ideal elements. The most noteworthy is the radiating elements; all can be matched independently after decoupling since they are well isolated. Measured S-parameters show that the isolation is better than -30 dB within the band of interest. The envelope correlation coefficient is also within the acceptable range. The basic principle provides a promising method for any antenna since the method only relies on the antenna impedances.