A first RF-to-DC circuit receives a radiofrequency signal and produces a first converted signal delivered to an energy storage circuit. A second RF-to-DC circuit, which is a down-scaled replica of the first RF-to-DC circuit, produces a second converted signal from the radiofrequency signal that is indicative of an open-circuit voltage of the first RF-to-DC circuit. The first RF-to-DC section includes N sub-stages, with a sub-set of sub-stages being selectively activatable. A window comparison of the second converted signal generates a first signal and a second signal indicative of whether the second converted signal is within a range of values proportional to a voltage reference signal. The sub-set of sub-stages is selectively deactivated, respectively activated, when the performed window comparison has a first result, respectively, a second result.