A resonant circuit comprises an input terminal and an output terminal and at least: a group of N resonators, where N≧1, the resonators having the same resonance frequency and the same antiresonance frequency; a first and a second impedance matching element having a non-zero reactance, the first element being in series with the group of resonators, and the second element being in parallel with the group of resonators, the resonant circuit comprising: first means for controlling the group of resonators, enabling the static capacitance of the group to be fixed at a first value; second control means, enabling the impedance of the first impedance matching element and that of the second element to be fixed at second values; the first and second values being such that the triplet of values composed of the static capacitance of the group, the impedance of the first element, and the impedance of the second element can be used to determine the following triplet of parameters: the characteristic impedance Zc of the assembly formed by the group, the first impedance matching element and the second matching element; the resonance frequency ωr of the assembly; the antiresonance frequency ωa of the assembly, in order to stabilize the impedance of the circuit at a chosen characteristic impedance.