A Low-Profile and Wideband Triple-Mode Antenna for Wireless Body Area Network Concurrent On-/Off-Body Communications

In this article, a low-profile and wideband triple-port printed antenna for wireless body area network (WBAN) on-body and off-body communications is presented. Three ports are responsible for exciting three different patterns that are orthogonal to each other, including a vertically polarized omnidirectional pattern and two horizontally polarized broadside patterns with radiated fields polarized along the xand y-directions, respectively. In particular, the vertically polarized pattern is achieved by loading an annular array of metallic vias connected to a pin-fed patch antenna on the bottom, while the horizontally polarized patterns are enabled by a closely spaced modified E-shaped stacked patch on the top with additional slot cuts. The integrated antenna was fabricated and characterized, achieving a measured wide S
₁₁
<; -10 dB bandwidth of nearly 14%, a mutual coupling smaller than -15 dB, and an envelope correlation coefficient of less than 0.01. Further numerical and experimental investigations reveal that the proposed antenna has robust electrical properties under both structural deformation and human body loading. The superior performance indicates that the demonstrated antenna is a promising candidate for WBAN devices that can simultaneously support multiple communication modes as well as for other MIMO communications and sensing systems.