Patent ID: 7039380

Claim:
A frequency synthesizer usable in a wireless communication device, the frequency synthesizer having a phase locked loop comprising: a controllable oscillator operable to generate an output signal having an output frequency, said controllable oscillator being arranged for adjusting said output frequency within a predefined frequency range dependent on the value of a first control signal; a phase/frequency detector operable to generate an error signal in response to a phase and/or frequency difference between an input signal generated by frequency dividing said output signal, and a reference signal; a loop filter connected to generate said first control signal based on said error signal and output the generated signal to said controllable oscillator; and a control unit connected to the loop filter to receive a loop filter signal and generate a second control signal therefrom, and further connected to said controllable oscillator to provide said second control signal to said controllable oscillator, wherein said controllable oscillator is arranged for modifying said predefined frequency range based on said second control signal, and wherein said control unit further comprises an estimation unit configured to estimate a center frequency value, wherein said control unit is adapted to generate, at channel switching, a new value for the second control signal in response to the estimated center frequency value.