Standardised measurement method for measuring the modulation of an amplitude-modulated radio signal and method for filtering the radio signal

1. A method for filtering an amplitude-modulated radio signal, comprising implementing a method for measuring a standardized modulation level in an amplitude-modulated radio signal, said amplitude-modulated radio signal having a bandwidth and a carrier, said measurement method comprising:

transforming said amplitude-modulated radio signal into baseband, such that the representation of a Fourier transform of said radio signal as a function of frequency has a bandwidth centered on a center frequency equal to 0 Hz,

determining a frequency range between 200 Hz and 1.5 kHz,

measuring a level of the amplitude-modulated radio signal, by frequency steps, in said frequency range,

determining a standardized modulation level in the amplitude-modulated radio signal, corresponding to a sum of the level measurements by frequency steps, in the frequency range under consideration, divided by the measurement of the level of the amplitude-modulated radio signal in baseband calculated around the center frequency equal to 0 Hz, corresponding to the level of the carrier of the amplitude-modulated radio signal,

said filtering method moreover comprising:

comparing the standardized modulation level thus determined with a predetermined threshold,

on the basis of said comparison, selecting a first filter applied to the amplitude-modulated radio signal.

2. The method for filtering an amplitude-modulated radio signal as claimed in claim 1 , moreover comprising selecting a second filter, symmetrical to the first filter about the center frequency of the amplitude-modulated radio signal transformed into baseband, applied to said amplitude-modulated radio signal.

3. The method for filtering an amplitude-modulated radio signal as claimed in claim 1 , wherein the amplitude-modulated radio signal comprises a message consisting of an audio signal formed of a human voice.

4. The method for filtering an amplitude-modulated radio signal as claimed in claim 1 , wherein the first filter is chosen in real time so as to ensure dynamic selectivity in the amplitude-modulated radio signal.

5. The method for filtering an amplitude-modulated radio signal as claimed in claim 1 , wherein the first filter is a finite impulse response filter.

6. A modulation sensor configured so as to measure levels in an amplitude-modulated radio signal, by frequency steps, in a frequency range, and so as to determine a standardized modulation level of the radio signal in said frequency range, said standardized modulation level corresponding to a sum of the level measurements by frequency steps, in said frequency range, divided by a measurement of the level of the radio signal in baseband around the center frequency equal to 0 Hz, so as to implement the method for measuring a standardized modulation level as claimed in claim 1 .

7. A radio receiver comprising a modulation level sensor as claimed in claim 6 .

8. A motor vehicle comprising a radio receiver as claimed in claim 7 .

9. The method for filtering an amplitude-modulated radio signal as claimed in claim 2 , wherein the amplitude-modulated radio signal comprises a message consisting of an audio signal formed of a human voice.