Investigations and system design for simultaneous energy and data transmission through inductively coupled resonances

[摘要] Wireless Power Transfer (WPT) with simultaneous data transmission through coupled magnetic resonators is investigated in thispaper. The development of this system is dedicated to serve as a basis for applications in the field of Ambient Assisted Living(AAL), for example tracking vital parameters remotely, charge and control sensors and so on. Due to these different scenarios weconsider, it is important to have a system which is reliable under the circumstance of changing positioning of the receivingdevice. State of the art radio systems would be able to handle this. Nevertheless, energy harvesting from far field sources is notsufficient to power the devices additionally on mid-range distances. For this reason, coupled magnetic resonant circuits areproposed as a promising alternative, although suffering from more complex positioning dependency.

Based on measurements on a simple prototype system, an equivalent circuit description is used to model the transmission systemdependent on different transmission distances and impedance matching conditions. Additionally, the simulation model is used toextract system parameters such as coupling coefficients, coil resistance and self-capacitance, which cannot be calculated in asimple and reliable way.

Furthermore, a mathematical channel model based on the schematic model hasbeen built in MATLAB^©. It is used to point out the problemsoccurring in a transmission system with variable transmission distance,especially the change of the passband's centre frequency and its bandwidth.Existing solutions dealing with this distance dependent behaviour, namely thechange of the transmission frequency dependent on distance and the additionof losses to the resonators to increase the bandwidth, are considered as notinventive. First, changing the transmission frequency increases thecomplexity in the data transmission system and would use a disproportionaltotal bandwidth compared to the actually available bandwidth. Additionally,adding losses causes a decrease in the energy transmission efficiency.

Based on these facts, we consider a system that changes the channel itselfby tuning the resonant coils in a way that the passbandis always at a fixed frequency. This would overcome the previously describedissues, and additionally could allow for thepossibility to run several independent transmission systems in parallel without disturbing each other.

[学科分类] 电子、光学、磁材料