Dual-Frequency Decoupling Circuit Integrated with Matching Circuits for a Two-Element Array

With recent improvement in the quality and capacity of wireless communication, multiple antennas techniques, which are used in antenna diversity systems or Multiple-Input Multiple-Output (MIMO) systems, are becoming important. Also, multi-frequency antennas are required to correspond to communication systems using multi-frequency bands or diversification of wireless systems. There are many reports on the method of decreasing the mutual coupling between two-element antennas in dual-frequency bands. However, in many cases, dual-frequency matching circuits are needed after decreasing the coupling [1], then the circuit loss becomes large.