A system comprises a cavity being reflecting for RF waves and comprises at least one acoustic wave sensor exhibiting a resonance frequency band, coupled to a sensor antenna； and an interrogation/reception device for the sensor. The interrogation/reception device comprises: means for transmitting/receiving an RF signal transmitting within an interrogation frequency band comprising the resonance frequency band of the sensor； at least a first transmission/reception antenna and a second transmission antenna/reception, positioned within the cavity； means for dividing the signal into at least a first RF signal and a second RF signal, the first signal being transmitted to the first transmission/reception antenna and the second signal being transmitted to the second transmission/reception antenna； means for creating a phase-shift between the first RF signal and the second RF signal； means for analysing the power level of the received signal. An interrogation method used in the system is also provided.
