An electronic circuit (51) configured to provide an adjustable impedance at a first frequency comprises a transconductance amplifier (52) arranged to provide a current signal proportional to an input signal at an input terminal; at least one conversion arrangement, each comprising a mixer arrangement (53) utilizing a first local oscillator signal at said frequency to down-convert the current signal to a baseband voltage signal; a filtering arrangement (54, 55) connected to said mixer arrangement (53) and comprising at least a resistor and a capacitor in parallel; and a mixer arrangement (56) utilizing a second local oscillator signal at said frequency to up-convert a voltage signal present at the filter arrangement to an up-converted voltage signal; and a transconductance amplifier (57) arranged to provide a second current signal proportional to the up-converted voltage signal and to feed back said second current signal to the input terminal of the electronic circuit.