Digital delay line based frequency synthesizer
AssigneeMediatek Inc.
InventorPing-Ying Wang
Life of this patent
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Abstract
A frequency synthesizer is disclosed. The frequency synthesizer includes a period control word generator, a delta-sigma modulator, and a delay line unit. The period control word generator generates a period control word. The delta-sigma modulator receives the period control word and generates a phase selection signal. The delay line unit generates an output clock based on the phase selection signal. The delta-sigma modulator performs a carry-in operation based on a base number and the base number is adjustable and determined by a calibration process of the delay line unit.
Claims20
A frequency synthesizer comprising:
- a delta-sigma modulator for receiving a period control word and generating a phase selection signal;
- and
- a delay line unit for generating an output clock and a second control signal based on the phase selection signal and a second clock, the delay line unit comprising:
- a digital delay line for receiving the second clock and generating the output clock according to the phase selection signal;
- a delay unit for receiving the second clock and generating a delayed second clock;
- a dummy delay line for receiving the delayed second clock and generating a third clock;
- and
- a phase detection unit for receiving the output clock and the third clock, and generating the second control signal according to a phase relationship between the output clock and the third clock;
- wherein the delta-sigma modulator performs a carry-in operation based on a base number and the base number is adjustable and determined by a calibration process of the delay line unit, and the delta-sigma modulator comprises:
- an adder for generating a difference signal by adding the period control word with a first control signal;
- and
- a value setting device for generating the first control signal;
- wherein the delta-sigma modulator generates a carry signal according to the difference signal, and the value setting device receives the carry signal and the second control signal, and provides the first control signal to the adder for performing the carry-in operation.
A method for compensating for a temperature variation in a frequency synthesizer, the method comprising:
- a delta-sigma modulator of the frequency synthesizer receiving a period control word and generating a phase selection signal;
- a digital delay line of a delay line unit receiving a second clock and generating an output clock according to the phase selection signal;
- a delay unit of the delay line unit receiving the second clock and generating a delayed second clock;
- a dummy delay line of the delay line unit receiving the delayed second clock and generating a third clock;
- a phase detection unit of the delay line unit receiving the output clock and the third clock, and generating a second control signal according to a phase relationship between the output clock and the third clock;
- determining a base number of a carry-in operation based on the second control signal, the carry-in operation being performed by the delta-sigma modulator;
- an adder of the delta-sigma modulator generating a difference signal by adding the period control word with a first control signal;
- a value setting device of the delta-sigma modulator generating the first control signal;
- the delta-sigma modulator generating a carry signal according to the difference signal;
- and
- the value setting device receiving the carry signal and the second control signal, and providing the first control signal to the adder for performing the carry-in operation.
Dependencies are inferred from the claim text.