A Wireless Power and Bidirectional Data Telemetry Prototype Using a Single Inductive Link for Biomedical Implants

This paper presents a prototype of a wireless power and half-duplex data telemetry subsystem using a single inductive link for implantable biomedical applications. In order to maintain continuity of power delivery for bidirectional data telemetry, half-duplex frequency-shift keying (FSK) and resonance-shift keying (RSK) are employed for the downlink and uplink, respectively. Frequency splitting characteristics of short-distance inductive link is utilized to determine the modulation frequencies of FSK, while the RSK is realized by switching a resonant capacitor at the secondary coil. The characteristics of the inductive link combining FSK and RSK are analyzed in detail as the theory basis for device parameter design. A prototype designed with discrete components delivers 125-mW continuous power with 127- and 700-Kbps data rates for the FSK downlink and RSK uplink, respectively, which acts as a reference of chip implementation for implantable wireless power and bidirectional data links.