Method and apparatus for in vivo sensing

Systems and methods for in vivo sensing are provided. An excitation signal is produced, having a first frequency component and a second frequency component. The first frequency component is swept through a plurality of excitation frequencies within a frequency range of interest.. A response signal is received from an in vivo sensor. The response signal includes a mix component having a frequency equal to one of a sum of a first excitation frequency associated with the first frequency component and a second excitation frequency associated with the second frequency component and a difference between the first and second excitation frequencies. The mix component is evaluated to determine a resonant frequency of the in vivo sensor.