UWB Metasurface Antenna With Improved Gain and Bandwidth for WBAN Application

As the transmission rate of Wireless Body Area Network (WBAN) increases, ultrawideband (UWB) technology is increasingly being applied to WBAN. To effectively integrate UWB technology into WBAN transmission systems, it is essential to develop UWB antennas that meet the requirements of wide bandwidth, ease of fabrication, and compatibility with the human body. Based on the characteristic mode analysis (CMA) theory, this study proposed a honeycomb structure metasurface layout to significantly expand the antenna bandwidth. The implementation of a cross-slot and ring-shaped microstrip line series feed network introduced a 90° phase difference to a pair of vertically polarized degenerate characteristic modes. This excited the degenerate modes, achieving excellent far-field radiation. The dimensions of the designed antenna were <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.4\lambda _{0} \times 1.4\lambda _{0} \times 0.09\lambda _{0}}$ </tex-math></inline-formula>(where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ {\lambda _{0}}$ </tex-math></inline-formula> represents the wavelength corresponding to the center frequency of 7 GHz). Simulations showed that the antenna can stably operate within the 5.12–9.13 GHz frequency band, with absolute and relative bandwidths of 4.01 GHz and 57.14%, respectively. Within the passband, the maximum gain reached 10.43 dBi, with an average gain of approximately 9.4 dBi. The calculated specific absorption rate (SAR) of the antenna indicated that the average SAR was below 2 W/kg, complying with regulatory standards.