Systems and methods for maintaining a drive signal to a resonant circuit at a resonant frequency are provided. A system for maintaining a drive signal to a resonant circuit at a resonant frequency can include: an oscillator configured to provide an output to a phase comparator and a drive circuit, the...http://www.google.com.au/patents/US20110084752?utm_source=gb-gplus-sharePatent US20110084752 - Systems and Methods for Maintaining a Drive Signal to a Resonant Circuit at a Resonant Frequency
