Patent ID: 8436512

Claim:
A method of remotely interrogating a passive sensor, comprising at least one resonator, so as to determine the resonant frequency of said resonator, having a resonant frequency response defined by the design of said resonator, the method comprising: a preliminary frequency-scan step for interrogating said resonator over a frequency range determined by the design of said resonator, allowing for the rapid determination of a resonant frequency response centred on a preliminary resonant frequency (fr 0 ) located between a lower preliminary frequency (fr pi ) and a higher preliminary frequency (fr ps ) defined at the half-maximum of said resonant frequency response of said resonator by detecting the amplitude of the response signal of said resonator; a first step of a first couple of interrogations of said resonator at a first frequency (f 11 ) and a second frequency (f 21 ) such that f 11 =fr 0 −f m /2 and f 21 =fr 0 +f m /2, with f m <f ps −fr pi , allowing a first couple of amplitudes (Pf 11 , Pf 21 ) of first and second reception signals to be defined; a second step of determining the amplitude difference (Δ(Pf 11 −Pf 21 )) between the first and second signals, said difference being positively or negatively signed; a third step allowing a first resonant frequency (fr 1 ), controlled by said signed amplitude difference, to be defined and having the formula fr 1 =fr 0 +K*[Δ(Pf 11 −Pf 21 )−Ca], where Ca is a control set-point and K is a constant; and wherein the first, second and third steps are reiterated and an (i+1)th resonant frequency (fr i+1 ) from an ith resonant frequency (fr i ) is defined having the formula fr i+1 =fr i +K*[Δ(Pf 1i −Pf 2i )−Ca], so as to obtain a determined resonant frequency (fr i+1 ) such that the signed amplitude difference (Δ(Pf 1i −Pf 2i )) is equal to the control set-point (Ca).