Patent ID: 8364098

Claim:
An apparatus for modulating a phase locked loop that includes a variable frequency oscillator configured to generate an oscillator signal at an oscillator frequency; a variable division ratio divider configured to divide the oscillator signal using a variable division ratio; a phase comparator configured to generate an error signal indicative of a phase difference between the divided oscillator signal and a reference signal; and a coupler configured to control the oscillator frequency by applying, to a control input of the oscillator, a control signal based on the error signal, the apparatus comprising: modulation filtering means for providing a low frequency component of a modulation signal and a high frequency component of the modulation signal; scaling means for scaling the low frequency component by a first gain factor and the high frequency component by a second gain factor; outputs for delivering the low frequency component for controlling the division ratio and the scaled low and scaled high frequency components for controlling the oscillator frequency in combination with the error signal; energy estimation means for generating an indication of energy of the modulation signal and the energy of the error signal in a frequency range common to the modulation signal and the error signal; and gain adjustment means for modifying the first and second gain factors dependent on the indication of the energy.