Wearable Vivaldi UWB planar antenna for in-body communication

This paper proposes a planar Vivaldi antenna design in ultra wideband (UWB) for medical wireless capsule endoscope applications, in which it acts as the on-body receiver antenna. 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. An additional metallic reflector, added at the Vivaldi side with a certain spacing distance, effectively converts two opposite end-fire radiations from two opposite Vivaldi elements to one broadside radiation. The resulting planar Vivaldi antenna structure then has the maximum radiation normal to the Vivaldi plane so that the receiver antenna can be parallel to the body, which provides possibility for a compact planar belt implementation. On-body measurement further verifies the impedance matching of the proposed Vivaldi antenna. Diversity reception configuration and performance evaluation including space diversity and polarization diversity have been carried out based on the proposed Vivaldi element as well as an optimized linear polarized omnidirectional capsule antenna. A fully-optimized receiver antenna belt can be expected by combining both the space and polarization diversities.