Analysis and Prevention of Coupling-Dependent Data Flipping in Series-Series Resonant Wireless Power Transfer Systems

Load shift keying (LSK) is commonly used in wireless power transfer (WPT) systems for backscattering information from the receiver back to the transmitter. However, when the coupling coefficient (k) between the coupling coils falls below a threshold value (k<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DF</inf>), the demodulated LSK data can unexpectedly flip from '1' to '0' and '0' to '1'. This phenomenon is referred to as coupling-dependent data flipping (CDDF). This research investigates the factors that lead to CDDF in series-series resonant WPT systems, by taking into account of parasitic parameters of the coupled link and validates the analysis through SPICE simulations. To mitigate CDDF, we propose a carrier-frequency auto-tuning scheme that is also verified by simulation results.