On-body directional antenna design for in-body UWB wireless communication

A planar Vivaldi UWB antenna design is proposed as the on-body wearable receiver antenna for medical in-body wireless communications in this paper. The proposed antenna connects two opposite Vivaldi variants on one side of the substrate and is fed by a radial stub microstrip on the other side. With a metallic reflector at the Vivaldi side, a strong broadside radiation can be obtained from two opposite end-fire radiations resulting from two opposite planar Vivaldi variants. The proposed antenna shows good far field gain in free space measurement with certain optimized spacing distance of the metallic reflector. The impedance matching characteristics have been validated by measurements both in free space as well as on body surface. A 4-element circular-polarized configuration antenna is proposed with good impedance matching and radiation gain characteristics. A dual-polarized diversity reception antenna is also fabricated based on two in-phase fed perpendicular placed antenna elements. A good decoupling between both polarizations in the far field can be concluded. A receiver antenna belt can be expected by integrating multiple dual-polarized antenna units in an antenna array.