A method of determining at least one characteristic parameter of a resonant structure (4) comprising the following steps: firstly placing the resonant structure (4) at a location, said location being located in the far field of a first antenna (2) and in the far field of a second antenna (5), and secondly emitting electromagnetic waves (EEW) with different frequencies in a given frequency range by means of the first antenna (2) such that the emitted electromagnetic waves (EEW) are modified by the resonant structure (4) and modified electromagnetic waves (MEW) are achieved, and thirdly determining during a first determining step a first electric power-value being representative of the power associated with the emitted electromagnetic waves (EEW), and fourthly receiving the generated modified electromagnetic waves (MEW) by means of the second antenna (5) and fifthly determining during a second determining step a second electric power-value being representative of the power associated with the received modified electromagnetic waves (MEW), and sixthly determining the at least one characteristic parameter by using the first and second power-values determined during the first and second determining steps.