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Leveraging Electromagnetic Polarization in a Two-Antenna Motion Tracking System

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March 15, 2016
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Wireless sensing, tracking, and drawing technologies are enabling exciting new possibilities for human-mobile interaction.
They primarily rely on measurements of backscattered phase, amplitude, and Doppler signal distortions, and often require
many measurements of these quantities—in time, or from multiple antennas. In this paper we present the design and implementation
of PolarDraw, the first system for pen motion tracking that sends differentially-polarized wireless signals to glean
more information from the environment. Leveraging information received from each polarization angle, our novel algorithms
infer orientation and position of an RFID-tagged pen using just two antennas, writing in the air or on a whiteboard. An experimental
comparison in a cluttered indoor office environment compares two-antenna PolarDraw with recent state-of-the-art
object tracking systems that use double the number of antennas, demonstrating comparable centimeter-level tracking accuracy
and character recognition rates (88–94%), thus making a case for the use of polarization in many other tracking systems.

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