Mutual coupling reduction between two inverted-F antennas using mushroom-type composite right-/left-handed transmission lines

The use of adaptive antenna and MIMO antenna in next-generation high-speed mobile communication systems has been extensively studied. These antenna systems must be equipped with multiple antennas. Mutual coupling between these antennas should be reduced as much as possible since it strongly influences the performance of the antenna system. In this study, we have developed a method for reducing the mutual coupling between antennas by installing mushroom-type CRLH transmission lines between them. The effectiveness of our method was examined by performing simulation analyses and measurements. The results demonstrated that our method can substantially reduce the mutual coupling between two vertically-parallel inverted-F antennas set a half-wave length apart. However, our method cannot reduce the mutual coupling between two vertically-parallel monopole antennas set a half-wave length apart, owing to the incomplete impedance matching between the antennas.