Method and circuit for clock recovery of a data stream description
View Patent ↗A method for clock recovery and data recovery from a data stream on a communication channel includes sampling a data stream on the communication channel at a sampling frequency determined by a clock signal and generating a sampled signal. The method further includes determining a phase shift between the communication data stream and the sampled signal and modifying the phase of the clock signal on the basis of the phase shift to obtain a desired phase difference between the sampled signal and the data stream.
1. A method for clock recovery and data recovery from a data stream on a communication channel, comprising the steps of:
sampling a data stream on the communication channel at a sampling frequency determined by a clock signal and generating a sampled signal;
determining a phase shift between the communication data stream and the sampled signal;
modifying the phase of the clock signal on the basis of the phase shift, to obtain a desired phase difference between the sampled signal and the data stream;
wherein determining the phase shift between the sampled signal and the data stream comprises applying the sampled signal and the data stream to two inputs of a phase comparator that supplies an output phase shift signal; and
wherein the phase shift signal is applied to a calculation block of a delay time between two edges of the phase shift signal, to supply a signal that is a function of the delay time.
2. The method of claim 1 , wherein the data stream is sampled at a predetermined point of the clock signal.
3. The method of claim 1 , wherein the data stream is sampled through a sample-and-hold circuit.
4. The method of claim 1 , wherein the data stream is sampled at the rising edges of the clock signal.
5. The method of claim 1 further comprising:
estimating a transmission frequency of the data stream; and
wherein the frequency of the clock signal is set as a function of the transmission frequency of the data stream.
6. The method of claim 1 ,
wherein the phase shift signal is generated by applying the data stream and the sampled signal to the inputs of an exclusive OR logic gate; and
wherein the phase shift signal is determined by the output signal of the logic gate.
7. The method of claim 1 , wherein the clock signal is modified as a function of the phase shift signal.
8. The method of claim 1 , wherein a signal that is a function of the delay time is applied to a compensator whose output modifies the phase of the clock signal so that the difference in phase between the sampled signal and the data stream converges toward the desired phase difference.
9. The method of claim 8 , wherein the compensator comprises a proportional-integral compensator.
10. The method of claim 8 , wherein the output of the compensator is applied to a clock signal generator.
11. The method of claim 10 , wherein a signal indicating the desired difference in phase between the sampled signal and the data stream is applied to the clock signal generator.
12. The method of claim 10 , wherein the output of the clock signal generator is applied to a sampling delay block and the output of the delay block is used to control sampling of the data stream.
13. A circuit for clock recovery and data recovery from a data stream on a communication channel, the circuit comprising:
a PLL circuit comprising an oscillator configured to generate a clock signal at a clock frequency;
a phase detector circuit comprising
an input configured to receive the data stream at a communication frequency;
a sample-and-hold circuit configured to be controlled by a sampling signal at a sampling frequency;
a phase comparator having a first input configured to receive the data stream and a second input to which a signal sampled by the sample-and-hold circuit is applied, the phase comparator effective to output a phase signal that is a function of the phase difference between the data stream and the sampled signal;
wherein the PLL circuit is effective to generate a control signal for the oscillator, on the basis of the phase signal, the control signal being such as to make the phase difference between the sampled signal and the data stream converge toward a desired phase difference; and
wherein the PLL circuit comprises a time interval extractor block effective to determine the duration of the phase signal, to an input of which the phase signal is applied.
14. The circuit of claim 13 , wherein the sampling frequency is a function of a communication frequency.
15. The circuit of claim 13 , wherein a time interval shifter block is associated with the time interval extractor block.
16. The circuit of claim 13 , wherein the PLL circuit comprises a proportional-integral compensator, the proportional-integral compensator having an input configured to receive a signal that is a function of the phase signal and having an output configured to supply a phase variation signal that modifies the phase of the clock signal of the oscillator.
17. The circuit of claim 16 , further comprising a sampling delay block functional to impose a delay on the sampling signal as a function of the maximum level transition time of the data stream.