A Novel Calculation-based Parasitic Decoupling Technique for Increasing Isolation in Multiple-element MIMO Antenna Arrays

This paper presents a systematic and accurate calculation method to design the parasitic decoupling technique (PDT) for increasing antenna isolation in the multiple-element multiple-input multiple-output (M-MIMO) array. The mutual coupling among antennas is suppressed by incorporating the parasitic decoupling structure (PDS) to generate the desired interference against the original antenna coupling. The designed PDS is composed of the parasitic scatterers, transmission lines (TLs), and reactive loads. A general network model is developed to determine the TL lengths and load reactances to satisfy the criteria derived from antenna impedances for high isolation. The decoupling methodology is further verified by two benchmarks. The simulation and measurement results demonstrate that isolation over 25 dB, efficiency above 72%, and envelop correlation coefficient below 0.02 can be achieved for both examples after using the proposed PDT. Besides, the PDT leads to improved pattern diversity, suitable for MIMO applications.