Auxiliary-carrier load-shift keying for reverse data telemetry from biomedical implants

This paper introduces a new approach for data telemetry from biomedical implantable devices to the external world (also known as reverse data telemetry). In the proposed approach, while power (and perhaps data) is transferred to the implant using a main carrier, a second carrier is also sent to the implant through the same link. The second carrier, which is of higher frequency and smaller amplitude, is envisioned for reverse data telemetry by load-shift keying. In this work, the wireless link is realized with two resonant frequencies using closely-coupled printed spiral coils and LC matching networks. The main and auxiliary carrier frequencies are 1MHz and 10MHz with 5V and 1V peak amplitudes, respectively. While the link is capable of continuously supplying unregulated power of up to 80mW at 4V(peak) to a 100-Ω resistive load, data telemetry at a rate of 100 kbps is successfully tested in the reverse direction.