An integrated radiofrequency circuit (1) is provided that includes an antenna (2) for receiving radiofrequency signals, a rechargeable battery (3) and a battery charger (5) using the radiofrequency signals to charge said battery. The circuit is characterized in that the battery charger is integrated in the same substrate as the integrated radiofrequency circuit and in that the battery charger includes a calibrating mechanism, a current source calibrated by the calibrating mechanism and delivering a charge current of constant maximum intensity drawn from the received radiofrequency signals, and a comparator between a reference quantity representative of the end of battery charge level and a variable quantity representative of the battery charge level supplying at output a control signal (batchend) for charging or not charging the battery.