title: On the design of efficient multi-coil telemetry system for biomedical implants.
abstract: Two-coil based inductive coupling is a commonly used technique for wireless power and data transfer for biomedical implants. Because the source and load resistances are finite, two-coil systems generally achieve a relatively low power transfer efficiency. A novel multi-coil technique (using more than two coils) for wireless power and data transfer is considered to help overcoming this limitation. The proposed multi-coil system is formulated using both network theory and a two-port model. Using three or four coils for the wireless link allows for the source and load resistances to be decoupled from the Q-factor of the coils, resulting in a higher Q -factor and a corresponding improved power transfer efficiency (PTE). Moreover, due to the strong coupling between the driver and the transmitter coil (and/or between the receiver and the load coil), the multi-coil system achieves higher tunable frequency bandwidth as compared to its same sized two-coil equivalent. Because of the wider range of reflected impedance in the multi-coil system case, it is easier to tune the output power to the load and achieve the maximum power transfer condition for given source voltage than in a configuration with two coils. Experimental results showing a three-coil system achieving twice the efficiency and higher gain-bandwidth product compared to its two-coil counterpart are presented. In addition, a figure of merit for telemetry systems is defined to quantify the overall telemetry system performance.
authors.affiliation: Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT 84112, USA. akram84@gmail.com
authors.forename: A K
authors.initials: AK
authors.lastname: Ramrakhyani
authors.forename: G
authors.initials: G
authors.lastname: Lazzi
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D019736:Prostheses and Implants; D013686:Telemetry