A closed-loop inductive power control system for an instrumented strain sensing tibial implant

Inductively-powered implantable biomedical devices are widely used nowadays, however the power variations due to the coil misalignment can significantly affect the device performance. A closed-loop power control system is proposed in this paper, which is implemented in a Subject-Carried Implant Monitoring Inductive Telemetric Ambulatory Reader (SCIMITAR) for remote strain data acquisition from an instrumented ovine tibia implant. The output power of the energizer is adaptively adjusted via a feedback circuitry connected the demodulator with the power energizer. Lab results showed that feedback suppressed variations in induced power caused by coil misalignment and extended the functional range of the device in axial and planar directions.