Periodic signal synchronization apparatus, systems, and methods

A method comprising:

• generating a periodic output signal from a periodic input signal;
• determining an average phase difference between the output signal and the input signal over a plurality of periods of the input signal including:
• generating a multi-phase clock signal having a plurality of phases, each phase of the multi-phase clock signal having a period approximately equal to a period of the input signal;
• comparing each phase of the multi-phase clock signal to the input signal and the output signal;
• determining a phase difference between the input signal and the output signal for each of a plurality of periods of the input signal based on the comparison with the multi-phase clock signal;
• and
• determining an average phase difference to be an average of the phase differences determined for the plurality of periods of the input signal;
• and
• delaying the input signal based on the average phase difference to generate the output signal.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• obtaining a plurality of samples of a phase difference between the output signal and the input signal;
• and
• adjusting a phase of the output signal based on a calculated phase difference calculated by alternately adding and subtracting succeeding samples of the phase difference.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• obtaining a plurality of samples of a phase difference between the output signal and the input signal;
• and
• adjusting a phase of the output signal based on a calculated phase difference calculated by adding or subtracting differently weighted samples of the phase difference.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• obtaining a plurality of samples of a phase difference between the output signal and the input signal;
• and
• adjusting a phase of the output signal based on a least variance approximation of the samples of the phase difference.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• obtaining a plurality of samples of a phase difference between the output signal and the input signal;
• and
• adjusting a phase of the output signal based on a least squares estimate of the samples of the phase difference.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• obtaining a plurality of samples of a phase difference between the output signal and the input signal;
• and
• adjusting a phase of the output signal based on an Nth root of a product of the samples of the phase difference.

A method comprising:

• generating a periodic output signal from a periodic input signal;
• comparing the output signal and the input signal with a selected clock signal;
• measuring a phase difference between the output signal and the input signal from the comparison with the selected clock signal;
• and
• adjusting a phase of the output signal based on the comparison of the output signal and the input signal with the selected clock signal.

An apparatus comprising:

• a clock generator to generate a selected clock signal;
• a phase detector having a first input coupled to receive a periodic input signal, a second input coupled to receive a periodic output signal, and an output, the phase detector to generate a phase difference signal on the output indicating a phase relationship between the input signal and the output signal;
• a digital circuit coupled to the output of the phase detector to receive the phase difference signal and coupled to the clock generator to receive the selected clock signal, the digital circuit to compare the phase difference signal with the selected clock signal to generate a plurality of phase difference measurements over a plurality of periods of the input signal, and to calculate an average phase difference from an average of the phase difference measurements;
• and
• an output circuit coupled to the digital circuit to adjust a phase of the output signal based on the average phase difference.