Calibration arrangement for frequency synthesizers
First Claim
1. An electronic device, the device 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 phase comparator output for generating a phase difference signal;
a voltage controlled oscillator having a first control input coupled to receive the phase difference signal 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 inputs;
a divider having a first input coupled to receive the oscillation signal and an output for generating the feedback signal by dividing the oscillation signal by a divisor, the divisor of the divider being programmed based on a divisor control signal received via a divisor input; and
a modulation unit having a modulation input for receiving a modulation signal, a first modulation output to provide the second control signal, and a second modulation output to provide the divisor control signal, and a change of the modulation signal generates a predefined change of the second control signal and a change of the divisor via the divisor control signal that is proportional to said predefined change; and
the calibration arrangement comprising;
a calibration input for receiving the phase difference signal;
a ripple detector for providing a ripple 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 generating a calibration control signal based on the ripple detector output signal,wherein the second control signal is adjusted based on the calibration control signal such that the detected ripple is reduced.
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Accused Products
Abstract
An electronic device has a calibration arrangement for controlling a frequency characteristic of a PLL circuit having a phase comparator having an output for generating a phase difference signal, a voltage controlled oscillator and a divider. The divisor of the divider is programmable, and the oscillator is also directly modulated by an oscillator modulation signal. A modulation unit has a modulation input for receiving a modulation signal and generates the oscillator modulation signal and the divisor such that modulation generates a predefined change of the output frequency and a change of the divisor proportional to said predefined change. The calibration arrangement receives the phase difference signal, and has 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. A calibration control unit adjusts the oscillator modulation signal based on the detector output signal such that the ripple is reduced.
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Citations
17 Claims
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1. An electronic device, the device comprising a calibration arrangement for controlling a frequency characteristic of a circuit, the circuit comprising:
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a phase comparator having a first input for receiving a feedback signal and a second input for receiving a reference frequency and a phase comparator output for generating a phase difference signal; a voltage controlled oscillator having a first control input coupled to receive the phase difference signal 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 inputs; a divider having a first input coupled to receive the oscillation signal and an output for generating the feedback signal by dividing the oscillation signal by a divisor, the divisor of the divider being programmed based on a divisor control signal received via a divisor input; and a modulation unit having a modulation input for receiving a modulation signal, a first modulation output to provide the second control signal, and a second modulation output to provide the divisor control signal, and a change of the modulation signal generates a predefined change of the second control signal and a change of the divisor via the divisor control signal that is proportional to said predefined change; and the calibration arrangement comprising; a calibration input for receiving the phase difference signal; a ripple detector for providing a ripple 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 generating a calibration control signal based on the ripple detector output signal, wherein the second control signal is adjusted based on the calibration control signal such that the detected ripple is reduced. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of controlling a frequency characteristic of a circuit of an electronic device, the method comprising:
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generating, by a phase comparator of the circuit, a phase difference signal representing the phase difference between a feedback signal and a reference frequency, the feedback signal and the reference frequency being respectively received at first and second inputs of the phase comparator; generating, by a voltage controlled oscillator of the circuit, an oscillator signal at an oscillation frequency controlled by the phase difference signal and a second control signal respectively received at first and second control inputs of the voltage controlled oscillator; generating, by a divider of the circuit, the feedback signal by dividing the oscillation signal by a divisor, the divisor being programmed based on a divisor control signal received via a divisor input of the divider; receiving a modulation signal at a modulation unit of the circuit; generating, by the modulation unit, the second control signal of the voltage controlled oscillator and the divisor control signal based at least in part on the received modulation signal, and a change of the modulation signal generates a predefined change of the second control signal and a change of the divisor via the divisor control signal that is proportional to said predefined change; receiving the phase difference signal at a calibration input of a calibration arrangement; detecting, via a ripple detector of the calibration arrangement, a ripple on the phase difference signal correlated to edges in the modulation signal; and generating, via a calibration control unit, a calibration control signal based on the results of the ripple detector, wherein the second control signal is adjusted based on the calibration control signal such that the detected ripple is reduced. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification