The present invention determines the resonant frequency of a sensor by adjusting the phase and frequency of an energizing signal until the frequency of the energizing signal matches the resonant frequency of the sensor. The system energizes the sensor with a low duty cycle, gated burst of RF energy having...http://www.google.es/patents/US7679355?utm_source=gb-gplus-sharePatente US7679355 - Communicating with an implanted wireless sensor
