Design of a wireless measurement system for use in wireless power transfer applications for implants

Abstract

The performance of wireless power transfer (WPT) systems is a function of many parameters such as resonance matching, coil quality factor, system impedance match, and others. When designing and testing WPT systems, reliable measurement of system performance is essential. In our application, we use WPT to power biomedical implants for telemetry acquisition from small rodents, where rodent behavior data is used to study disease models. Such an application employs a large primary coil and a much smaller moving secondary coil, which can be defined as a loosely coupled WPT (LCWPT) system. This paper presents a novel wireless measurement system (WMS) that is used to collect real-time performance data from the secondary circuit (implant), while testing LCWPT systems. Presently, measuring the performance of the secondary side of LCWPT systems while they are in operation can be problematic. The literature reports various measurement errors when using voltage/current probes, or coaxial cables placed directly into the primary magnetic field. We have designed the WMS to greatly reduce such measurement errors, where the WMS measures the induced voltage (and hence received power) and relays this information by radio. Experiments were done to test the WMS, as well as comparison with cable-based measurements.