The radio-frequency signal frequency conversion device generates intermediate complex signals (IF) for a correlation stage of a low power RF receiver. In order to do this, the device includes a first selective pass-band filter for filtering radio-frequency signals picked up by an antenna. A frequency synthesizer generates first and second high frequency signals, wherein the frequency of the first signals is higher than the frequency of the second signals. This synthesizer receives reference signals from an oscillator unit. A first mixer unit mixes the radio-frequency signals with the first signals in order to generate frequency-converted signals. A second pass-band filter filters the signals from the first mixer unit, and provides signals to a second mixer unit to mix them with the second high frequency signals. Finally, shaping means for the signals provided by the second mixer unit generate the intermediate signals. The second filter is a not very selective active filter, which is integrated, in an RF/IF integrated circuit with the first and second mixer units, the signal shaping means, and certain parts of the synthesizer and the oscillator unit.