Radiation Pattern Analysis of Single and Multi-Antenna Wearable Systems

This paper presents 3D radiation pattern analyses for omnidirectional (dipole) and directional (patch) antennas for various body locations encompassing wrist orientations and chest positions when mounted on a body phantom. In addition to analysing the directivities and relative efficiencies at 2.44GHz for different body positions, the study considers Sector and Slice analysis of the radiation patterns. In Sector analysis, the directivity is averaged for 12 azimuth-elevation sectors, while in Slice analysis, it is averaged for 28 azimuth sectors over the full elevation. It is shown that the antenna efficiency due to body blockage can be as low as 23% relative to the chest position efficiency, and directivities ranges from 5.4 to 10.5dBi for the antennas at different orientations. The Sector analysis identifies highest average signal levels, which are between table and door height for the dipole and above door height for the patch. The Slice analysis, which doesn't account for access point or user heights, shows average directivities that peak at 5.1 and 4.4dBi for the dipole and patch antenna, respectively. Using these antennas as part of a switch diversity system would improve the average directivity by approximately 7dBi in regions of low signal levels, and hence are potentially useful for wristbands and smart clothing.