Focusing through walls: An E-shaped patch antenna improves whole-home radio tomography

Abstract

Tagless identification and tracking with through-wall received signal strength-based radio tomographic imaging (RTI) allows emergency responders to learn where people are inside of a building before entering the building. Use of directional antennas in RTI nodes focuses RF power along the link line, improving system performance. However, antennas placed on a building's exterior wall can be detuned by their close proximity to the dielectric, thus sending power across wider angles and resulting in less accurate imaging. In this paper, we improve through-wall RTI by using an E-shaped patch antenna we design to be mounted to an exterior wall. Along with its directionality, the E-shaped patch antenna is designed to avoid impedance mismatches when brought into close proximity of a dielectric material, thus increasing radiation through the exterior wall and along the link line. From our experiments, we demonstrate that the E-shaped patch antenna can reduce the median root mean square localization error by up to 43% when compared to microstrip patch and omnidirectional antennas. For equal error performance, the E-shaped patch antenna allows an RTI system to reduce power and bandwidth usage by using fewer nodes and measuring on fewer channels.