ISI pattern-weighted early-late phase detector with function-controlled oscillation jitter tracking

1. A method for function-controlled phase oscillation tracking jitter in a recovered clock signal using an inter-symbol interference (ISI) pattern-weighted early-late phase detector, the method comprising:

receiving an electromagnetic waveform representing an analog serial data stream;

generating an I clock and Q clock having a function-controlled oscillation cycle phase delay with respect to the I clock;

dividing the I clock frequency by n, creating a reference clock;

sequentially sampling the serial data stream with the I clock, creating digital I-bit values;

sequentially sampling the serial data stream with a Q clock having the function-controlled oscillation cycle phase delay, creating varied phase delay digital Q-bit values;

segmenting the I-bit values into n-bit digital words;

segmenting the varied phase delay Q-bit values into n-bit digital words;

in response to analyzing the I-bit values and the varied phase delay Q-bit values, identifying an I clock phase correction;

in response to comparing the I-bit values and the varied phase delay Q-bit values, determining a modulation factor;

identifying bit sequence patterns associated with each I-bit value;

weighting each I-bit value in response to the identified bit sequence pattern and the identified I clock phase correction;

averaging the weighted I-bit values for each n-bit digital word;

applying the modulation factor to the weighted I-bit value averages, generating digital I and Q phase error signals; and,

in response to the I and Q phase error signals, creating electromagnetic signals representing the I clock and the function-controlled oscillation cycle phase delay Q clock, modified in phase.

2. The method of claim 1 wherein generating the I clock and the function-controlled oscillation cycle phase delay Q clock includes generating a function-controlled oscillation cycle phase delay Q clock that has an average delay of about 90 degrees with respect to the I clock phase.

3. The method of claim 1 wherein sequentially sampling the serial data stream with the function-controlled oscillation cycle phase delay Q clock includes generating a Q clock that oscillates between a value having a phase delay of (X−f(d)) and a value having a phase delay of (X+f(d)), where X is the phase delay of the average delay Q clock with respect to the I clock, and where f(d) is a function with a variable d.

4. The method of claim 3 wherein generating the Q clock that oscillates includes generating a Q clock with a rate of change controlled by the variable d.

5. The method of claim 4 wherein generating the Q clock that oscillates includes generating a Q clock having a triangular cycle delay around the value of X, with a cyclic frequency that decreases as the value of f(d) approaches a maximum value (dfinal), and increases as the value of f(d) approaches zero.

6. The method of claim 4 wherein the process of generating the Q clock that oscillates includes the following steps:

a) initializing by setting the values of d and dmax to zero;

b) incrementing the value of dmax one unit value;

c) incrementing the value of d by one unit value every k reference clock cycles, until d=dmax;

d decrementing the value of d by one unit value every k reference clock cycles, until d=−(dmax);

e) incrementing the value of d one unit value each cycle every k reference clock cycles, until d=0;

f) if dmax<dfinal, repeating Steps b) through e);

g) if dmax=dfinal, decrementing the value of dmax one unit value;

h) incrementing the value of d by one unit value every k reference clock cycles, until d=dmax;

i) decrementing the value of d by one unit value every k reference clock cycles, until d=−(dmax);

j) incrementing the value of d one unit value every k reference clock cycles, until d=0;

k) if dmax >0, repeating Steps g through j; and,

l) if dmax=0, repeating Steps b through f.

7. The method of claim 1 wherein creating I clock and the function-controlled oscillation cycle phase delay Q clock, modified in phase in response to the I and Q phase error signals, includes modifying the I clock and the Q clock having the function-controlled oscillation cycle phase delay at time t 1 ;

wherein identifying the I clock phase correction in response to analyzing the I-bit values and the varied phase delay Q-bit values includes:

waiting a time delay t 2 from t 1 (t 1 +t 2 =t 3 ), where t 2 is a delay associated with sampling the serial data stream and creating the digital I-bit values; and,

beginning the analysis of I-bit and varied phase delay Q-bit values associated with the modified I clock and modified Q clock having the function-controlled oscillation cycle phase delay at time t 3 .

8. The method of claim 7 wherein generating digital I and Q phase error signals includes generating new I and Q phase error signals, k reference clock cycles following time t 3 .

9. A system for function-controlled phase oscillation tracking jitter in a recovered clock signal using an inter-symbol interference (ISI) pattern-weighted early-late phase detector, the system comprising:

a phase interpolator having an output to supply an I clock signal, an output to supply a Q clock signal having the function-controlled oscillation cycle phase delay with respect to the I clock signal, and an input to accept digital I and Q phase error signals;

a deserializer having inputs to accept an analog serial data stream, the I clock, and the function-controlled oscillation cycle phase delay Q clock, and having outputs to supply n-bit digital words of I-bit values generated by sampling the serial data stream with the I clock, n-bit words of varied phase delay Q-bit values generated by sampling the serial data stream with the Q clock having the function-controlled oscillation cycle phase delay, and a reference clock signal equal to the I clock frequency divided by n;

an early-late phase detector having an input to accept the I-bit values, varied phase delay Q-bit values, and the reference clock, and in response to analyzing the I-bit and varied phase delay Q-bit values, identifying an I clock phase correction, the detector also identifying bit sequence patterns associated with each I-bit value, weighting each I-bit value in response to the identified bit sequence pattern and the identified I clock phase correction, and having an output to supply a digital average of the weighted I-bit values for each n-bit digital word;

a jitter tracking module having inputs to accept the I-bit and varied phase delay Q-bit values, and in response to comparing the varied phase delay Q-bit values to the I-bit values, supplying a modulation factor;

a feedback circuit having inputs to accept the average of the weighted I-bit values for each n-bit digital word and the modulation factor, the feedback circuit applying the modulation factor to the weighted I-bit value averages, and having an output to supply the I and Q phase error signals; and,

wherein the phase interpolator accepts the I and Q phase error signals and respectively modifies the phases of the I clock and the function-controlled oscillation cycle phase delay Q clock.

10. The system of claim 9 wherein the phase interpolator supplies a function-controlled oscillation cycle phase delay Q clock signal with an average delay of about 90 degrees with respect to the I clock signal phase.

11. The system of claim 9 wherein the phase interpolator generates the function-controlled oscillation cycle phase delay Q clock by generating a Q clock that oscillates between a value having a phase delay of (X−f(d)) and a value having a phase delay of (X+f(d)), where X is the average phase delay of the Q clock with respect to the I clock, and where f(d) is a function with a variable d.

12. The system of claim 11 wherein the phase interpolator generates a function-controlled oscillation cycle phase delay Q clock with a rate of change controlled by the variable d.

13. The system of claim 12 wherein the phase interpolator generates a function-controlled oscillation cycle phase delay Q clock having a triangular cycle delay around the value of X, with a cyclic frequency that decreases as the value of f(d) approaches a maximum value (dfinal), and increases as the value of f(d) approaches zero.

14. The system of claim 13 wherein the phase interpolator generates the function-controlled oscillation cycle phase delay Q clock as follows:

a) initializing by setting the values of d and dmax to zero;

b) incrementing the value of dmax one unit value;

c) incrementing the value of d by one unit value every k reference clock cycles, until d=dmax;

d decrementing the value of d by one unit value every k reference clock cycles, until d=−(dmax);

e) incrementing the value of d one unit value each cycle every k reference clock cycles, until d=0;

f) if dmax <dfinal, repeating Steps b) through e);

g) if dmax=dfinal, decrementing the value of dmax one unit value;

h) incrementing the value of d by one unit value every k reference clock cycles, until d=dmax;

i) decrementing the value of d by one unit value every k reference clock cycles, until d=−(dmax);

j) incrementing the value of d one unit value every k reference clock cycles, until d=0;

k) if dmax >0, repeating Steps g through j; and,

l) if dmax=0, repeating Steps b through f.

15. The system of claim 9 wherein the phase interpolator modifies the I clock and function-controlled oscillation cycle phase delay Q clock phases at time t 1 in response to the I and Q phase error signals; and,

wherein the early-late phase detector waits a time delay t 2 from t 1 (t 1 +t 2 =t 3 ), where t 2 is a delay associated with the deserializer sampling the serial data stream to create I-bit values, and begins the analysis of I-bit and varied phase delay Q-bit values associated with the modified I clock and modified function-controlled oscillation cycle phase delay Q clock at time t 3 .

16. The system of claim 15 wherein the feedback circuit supplies new I and Q phase error signals k reference clock cycles following time t 3 .