Communicating with an implanted wireless sensor

A system for determining a resonant frequency of a wireless sensor, comprising:

• a base unit for transmitting a first set of energizing signals and receiving a first set of sensor signals, wherein each of the energizing signals of the first set has a different frequency and each of the sensor signals of the first set has a phase;
• wherein the base unit comprises a signal processor for measuring the phase for each of the sensor signals, determining a first group phase delay and a second group phase delay based on the sensor signal phases, comparing the first group phase delay and second group phase delay, and determining a resonant frequency of the wireless sensor based on the comparison of the first group phase delay and second group phase delay.