The advantage of the canonical filter theory approach to design inductive power transfer (IPT) systems is that values for the coupled resonator elements are readily calculated from scaled canonical filter prototypes with specific frequency response characteristics. For example, Butterworth bandpass filter prototypes can be used to synthesize resonant-coupled IPT systems with critically-coupled frequency response characteristics. In this work, we analyze two canonical filter prototype structures: one prototype has series matching elements at the ports, and the other prototype has shunt matching elements at the ports. Equations are provided to transform the networks into coupled resonator structures that implement IPT links with a transmitter, receiver, and multiple repeater coils. The filter methodology for IPT link synthesis also provides an easy framework to evaluate design trade-offs. An example of comparing resonator inductor sizes for both the series and shunt matching topologies is shown for IPT links operating in ISM frequency bands of 6.78 MHz, 13.56 MHz, 27.12 MHz, and 40.68 MHz. Experimental results are shown for four different IPT examples that were designed using filter synthesis methods.
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