Mutual Coupling Suppression for On-Body Multiantenna Systems

The mutual coupling in small wearable multiantenna systems under bending conditions is studied. Two conventional passive mutual coupling suppression approaches, involving electromagnetic bandgap structures and defected ground structures (DGS) are investigated when curving or deforming. To overcome the limitations of those traditional isolators in on-body applications, a novel metamaterial-inspired isolator that combines DGS and modified split ring resonators (SRR) is proposed. It avoids any vertical conducting parts that have a high risk of being broken with time due to movements of the user. On top, it is wideband, with stable isolating performance under complex bending conditions, and does not affect the compactness of a linear array. The envelope correlation coefficient between the two on-body antennas, when the proposed isolator is present, is found to be low, which is important for a better throughput for a multiple-input-multiple-output system. A prototype is fabricated and measured to prove the validity of the new concept.