Strongly coupled array elements decoupled by Eigen-mode analysis and its affection on radiate property

Modern electrical devices prepare less space for antennas. Both the miniaturization of antenna elements and decoupling of antenna arrays have become significant problems to solve. This paper firstly discusses the usage of lossless passive network to decouple strongly coupled antennas, such as some previous works done by other authors. Then this paper mainly concentrates on the Eigen mode decoupling theory and finds that the radiation efficiency is affected by the decoupled network because it changes the Rayleigh quotient of the whole network. Furthermore, this paper uses microstrip branch-line directional coupler to decouple two strongly couples dipoles. It comes out an isolation below -25dB at a center frequency of 3.25GHz. The passive decouple network´s effect to the two-element array´s radiation efficiency is analyzed in detail. And it turns out to a conclusion that the function of the decoupled network can increase the radiation ability of the whole structure.