An Extended-Range Inductive Near-Field Telemetry System for High-Resolution Mapping of Gastrointestinal Activity.

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We present an extended-range near-field wireless data communication designed for high-resolution mapping of gastrointestinal bioelectrical activity. The system is composed of an implantable unit (IU), a wearable unit (WU) and a stationary unit (SU). The WU transfers power to the IU and recharges its battery through an inductive link, wirelessly; and over the same link, reads the 64-channel slow waves data encoded by a differential pulse position coding algorithm, which is modulated through a load shift-keying technique and sent by a back-telemetry circuit at the IU. To guarantee simultaneous WU-IU wireless power transfer and maximize the IU-WU data transfer rate, the duty cycle of the data stream is reduced to 6.25%. A newly designed 13.56 MHz high-power radio frequency power amplifier at the WU, extends the efficient range of IU-WU near-field data communication and power transfer. The retrieved data at the WU are either transmitted to the SU via a 2.4 GHz RF link for real-time monitoring or stored locally on a memory card. The measurements on the implemented system, demonstrate IU-WU data transfer rate of 125 kb/s, while the distance between the transmitter and receiver coils can reach up to 7 cm while maintaining the specific absorption rate below the guidelines.