Methods and systems for determining the resonance frequency of a resonator, using the Doppler effect. An interrogating sonic beam including a carrier frequency and one or more resonator exciting frequencies is directed at a resonator disposed in a measurement environment. Resonator vibrations are excited by the resonator exciting frequencies. The carrier frequency is modulated by the vibrating part(s) of the resonator. The returning signal is received and analyzed to determine the amplitude of the Doppler shifted sideband frequencies. The resulting data is processed to determine the resonator's resonance frequency. Using calibrated resonating sensors having a resonance frequency that varies as a function of a physical parameter in a measurement environment, the method and systems allow determining the value of the physical variable from the sensor's resonance frequency. The methods and systems may be used, inter alia, to determine intraluminal blood pressure in various parts of a cardiovascular system, the pressure of intra-cranial fluids, the pressure of fluids in various bodily cavities by using implantable calibratable resonating pressure sensors. The methods and systems may also be used for determining the pressure in various industrial measurement environments and enclosures. Methods and systems are provided for detecting the sensor and for centering the interrogating beam on the sensor.
