Patent ID: 8405464

Claim:
An electronic device for controlling a frequency modulation index comprising: a frequency modulation index control loop having an input adapted to be connected to a frequency output of a frequency controllable oscillator having a center frequency Fc and an output adapted to be connected to an input of a frequency-modulation unit, the modulation index control loop being adapted to determine the modulation index, wherein the frequency modulation index control loop is adapted to measure the modulated frequency which is output from the controllable oscillator; and wherein the modulation index is calculated by an integration over time of the absolute value of deviation from the center frequency of the measured modulated frequency signal; the frequency-modulation unit being adapted to output a modulation signal to the controllable oscillator for frequency-modulating the oscillator center frequency F c with a modulating frequency F m such that during a first half of the modulating time period T m the oscillator frequency is higher than the center frequency F c and during a second half of the modulating time period T m the oscillator frequency is lower than the center frequency F c ; an integrating unit with an input adapted to be connected to an output of the controllable oscillator and adapted to calculate a difference between an integration of the modulated oscillator frequency over time during the first half of the modulating time period T m and an integration of the modulated oscillator frequency over time during the second half of the modulating time period T m ; and a comparator unit coupled to an output of the integrating unit and adapted to compare the calculated difference with an expected difference and coupled to output a comparator signal to an input of the frequency-modulating unit to adjust the modulation signal output from the frequency-modulating unit accordingly to match the calculated difference with the expected difference.