Efficient Perturbation Method for Computing Two-Port Parameter Changes Due to Foreign Objects for WPT Systems.

The change in the two-port parameters of a wireless power transfer (WPT) chain is evaluated when an object (foreign object) with given material parameters is placed in the vicinity of the WPT transmitter and receiver. An integral formula for the change of the two-port parameters due to the presence of a foreign object has been derived by using the generalized theory of reciprocity. It is emphasized that—instead of taking the differences of the two-port parameters calculated with and without the presence of the foreign object—the presented method provides the change of the two-port parameters directly from the calculated electromagnetic field at the location of the foreign object. As a result, the relatively small parameter changes can be predicted with good accuracy. Based on the application of the Born approximation, the possibility of computing an approximation of the changes of the two-port parameters is explored. [ABSTRACT FROM AUTHOR]