Abstract
Inductive and capacitive impedance matching are two different techniques optimizing power transfer in magnetic resonance inductive wireless power transfer. Under ideal conditions, i.e., unrestricted parameter ranges and no loss, both approaches can provide the perfect match. Comparing these two techniques under non-ideal conditions, to explore fundamental differences in their performance, is a challenging task as the two techniques are fundamentally different in operation. In this paper, we accomplish such a comparison by determining matchable impedances achievable by these networks and visualizing them as regions of a Smith chart. The analysis is performed over realistic constraints on parameters of three different application cases both with and without loss accounted for. While the analysis confirms that it is possible to achieve unit power transfer efficiency with both approaches in the lossless case, we find that the impedance regions where this is possible, as visualized in the Smith chart, differ between the two approaches and between the applications. Furthermore, an analysis of the lossy case shows that the degradation of the power transfer efficiencies upon introduction of parasitic losses is similar for the two methods.
Highlights
Recent demand on mobility and accessibility of devices is pushing the development of wireless technology to new levels
This method is referred to as inductive matching. We showed that these two matching techniques, i.e., the capacitive and inductive matching could potentially achieve a similar level of matching in certain cases [15]
We present graphs of reflection coefficients in the Smith Chart, based on the equations derived in the previous section for both capacitive and inductive matching
Summary
Recent demand on mobility and accessibility of devices is pushing the development of wireless technology to new levels. The coupling between resonator and the driver coils (or the load coil) can be considered as parts of a matching network, where tuning of the impedance can be achieved by changing the coupling between them In our study, this method is referred to as inductive matching. Among the many different capacitive compensation circuitries, we chose the parallel-series compensation according to reference [8] for comparison to the inductive method This network offers sufficient degrees of freedom to match perfectly if there is no loss and no restriction on parameter ranges, it is sufficient to give an insight into the effect of these limitations. Our work presents a comparison of the matchable loads offered by the inductive and capacitive matching networks over a full range of realistic parameter ranges for three different applications distinguished by their operating frequency and power level [20,21,22]. The impact of parasitic loss to the matchable region is analyzed and optimized power simulation is given in the Section 4 and Section 5 discusses the outcome of the comparison
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