Calibration arrangement for frequency synthesizers

An electronic device, the device 4 comprising a calibration arrangement for controlling a frequency characteristic of a circuit, the circuit comprising

• a phase comparator having a first input for receiving a feedback signal and a second input for receiving a reference frequency and a comparator output for generating a phase difference signal,
• a voltage controlled oscillator having a first control input coupled to the phase comparator output and a second control input for receiving a second control signal, and an oscillator output for outputting an oscillator signal at an oscillation frequency controlled by the first and second control input,
• a divider having an input coupled to the oscillation signal and an output for generating the feedback signal, the divisor of the divider being programmable via a divisor input,
• a modulation unit having a modulation input for receiving a modulation signal and a first modulation output coupled to the second control input of the voltage controlled oscillator and a second modulation output coupled to the divisor input such that a change of the modulation signal generates a predefined change of the output frequency and a change of the divisor proportional to said predefined change,
• the calibration arrangement comprising:
• a calibration input for receiving the phase difference signal;
• a ripple detector for providing a detector output signal by detecting a ripple on the phase difference signal correlated to edges in the modulation signal;
• and
• a calibration control unit for adjusting the second control signal based on the detector output signal such that the ripple is reduced.