Design of Compact Single-Layer Textile MIMO Antenna for Wearable Applications

A compact single-layer textile MIMO antenna is designed for wearable applications. The theory of characteristic mode is used to guide the antenna design and analyze its performance. The MIMO antenna utilizes a small ground plane as the main radiator, which is capacitively loaded by two strips along two orthogonal edges. The whole system occupies a volume of 38.1 mm × 38.1 mm × 2 mm, with each antenna having a dipole-like radiation pattern of linear polarization. Good isolation of above 12 dB is achieved due to the quasi-orthogonal radiations generated by the two antennas, providing pattern and polarization diversities. The envelope correlation coefficient between the antennas is below 0.01. The proposed antenna, fabricated on a flexible felt with a permittivity of 1.2, has a wide bandwidth of 20%. Due to its broadband behavior, the antennas remain well matched at the target band when worn on the body and bended. The loss of the human tissue results in the drop of the antenna gains to 1.6 dBi and 1.2 dBi, respectively, for the two antennas. The proposed antenna is competitive for wearable applications, due to its compact size, single-layer structure, easy integration, robustness, and reasonable on-body antenna gain.