SwitchBack: an on-body RF-based gesture input device

ABSTRACT

We present SwitchBack, a novel e-textile input device that can register multiple forms of input (tapping and bi-directional swiping) with minimal calibration. The technique is based on measuring the input impedance of a 7 cm microstrip short-circuit stub consisting of a strip of conductive fabric separated from a conductive fabric ground plane (also made of conductive fabric) by a layer of denim. The input impedance is calculated by measuring the stub's reflection coefficient using a simple RF reflectometer circuit, operating at 900MHz. The input impedance of the stub is affected by the dielectric properties of the surrounding material, and changes in a predictable manner when touched. We present the theoretical formulation, device and circuit design, and experimental results. Future work is also discussed.

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Index Terms

• Human-centered computing

  • Human computer interaction (HCI)