Tunable decoupling of tri-band LTE700/GSM850/900 MIMO antenna with a parasitic scatterer for handheld devices

This paper presents a simple tunable decoupling mechanism for a tri-band coupled monopole antenna working in LTE700/GSM850/900 bands for MIMO application. A parasitic scatterer with two distributed MEMS tunable capacitors is utilized to match the impedance and mitigate the effects of mutual coupling between elements. Thus, the antenna performance is enhanced significantly by minimizing the coupling current. The prototype is evaluated through the scattering parameters, the total efficiency, the envelope correlation coefficient, radiation patterns, current distributions and fully characterized through simulations. By utilizing a simple passive de-coupling structure, the total efficiency is improved with 1-1.5 dB and a reduction in the envelope correlation coefficient in the order of 60-75% is obtained over a wide aggregated bandwidth. Due to the change in radiation mechanism for both of the antennas, orthogonal radiation patterns are formed. With this approach, the design of the mobile phone antenna can be simplified by moving to complexity from the antenna to the decoupling structure.