MCRWPT Design Through Analog Filter Theory

Abstract

Magnetically-Coupled Resonant Wireless Power Transfer (MCRWPT) is an emerging technology and the subject of extensive research. Existing research is primarily focused on improving the magnetic coupling properties of the four coils. The circuit parameters of these coils have been of less focus. These parameters are generally determined using optimization routines in an attempt to elicit the desired MCRWPT system performance. While this has proven to be an acceptable method of designing MCRWPT systems it would make more sense to determine the desired performance of the system, and then directly choose circuit parameters which will meet these requirements. Filter theory is chosen to realize this desire. This thesis begins by illustrating how filter theory techniques can be applied to the efficiency of an MCRWPT system. The square of the mutual coupling between the two resonator coils is chosen to act as the input variable which controls the power transfer efficiency of the entire system. This allows for MCRWPT systems to be specifically designed to maintain a high efficiency between two user-chosen coil separations. Next, a general solution to the equations which map the filter transfer function to the MCRWPT efficiency equation is presented. This solution allows for a high transfer efficiency to be realized across a wide range of separations. The transmitted power is found to be maximized at a certain separation and decrease when the coils are moved away from this separation. Finally, a modified general solution is presented. This solution maintains a high transfer efficiency beyond the range specified by the filter used to design the system. Unlike the original general solution, it also maintains a high transmitted power level over a wide range of coil separations.