Characteristic Mode Analysis of a Nonuniform Metasurface Antenna for Wearable Applications

A novel nonuniform metasurface antenna is designed based on the characteristic mode analysis for wearable applications. A metasurface layer consists of a 3 × 3 unit cell array, in which the center and corner cells are rotated counterclockwise, whereas the other four unit cells are rotated in the opposite direction with a same rotation angle. The structure of a nonuniform metasurface is optimized according to the modal significance curves and surface currents, which resulted that mode 1 and mode 2 are combined to widen the bandwidth, which can cover the 5 GHz WLAN band. The volume of the proposed antenna is equal to a cylinder with a diameter of 55 mm and a thickness of 4 mm. The measured efficiency is greater than 80% and the average gain can achieve 7.63 dBi in the working band. The proposed antenna is harmless to human body, which can be evidenced by the simulated 1 and 10 g averaged specific absorption rate values.