Modifications to Improve the Time-Domain Performance of the Van Veen Loop

Abstract

The Van Veen loop is intrinsically well adapted to time-domain measurements of net magnetic dipole moment. That is, the system comes very close to preserving the shape of the time-domain waveform of the net or residual magnetic dipole moment produced by the device under test. This property makes the Van Veen Loop very useful in the characterization of magnetic field wireless power transfer systems in which short-time-scale features such as ringing in inverter and rectifier circuits are present in the extraneous magnetic field. We present a unified derivation of the frequency response of the internal coaxial structure of the Van Veen loop showing explicitly why the system intrinsically provides nearly flat frequency response and hence distortionless time response. Additionally, we present two simple modifications to the internal circuitry, which further improve the time- and frequency-domain performance of the system to the extent that it approaches having a distortionless transfer function. A physical explanation for the mechanism by which the time-domain performance is improved is provided. This argument is based on the source termination in a time-domain transmission line analysis. Finally, an alternative frequency-domain analysis based on the high-pass Kuroda transform is given, which provides significant insight into the operation of the distortionless system.