Electrically tunable mode decomposition network for 2-port MIMO antennas

Typically, geometrically symmetric 2-port Multiple Input - Multiple Output (MIMO) antennas for LTE-enabled small mobile wireless devices feature radiation modes with significantly different radiation quality factors. It is difficult to precisely match radiation modes over the desired frequency band. Therefore, a solution for low-loss electrical tuning is of interest. The new solution, reported in the present paper, uses electrically tunable Mode Decomposition Network (MDN). Both radiation modes can be tuned individually by means of mutually independent mode-specific matching networks to the desired frequency bands while maintaining high modal efficiencies. The usable tuning range is restricted by parameters of commercially available components. An investigation of the practically attainable tuning range is shown.