Method and apparatus for phase detection in digital signals

A method of digital signal phase detection comprising the steps of:

• providing a data signal;
• providing a clock signal;
• providing a phase difference signal responsive to and representative of both the clock period of the clock signal and the difference in phase between the clock signal and data signal;
• providing a reference signal responsive to and representative of the clock period of the clock signal and duration of whose pulses is dependent only on the clock period of the clock signal;
• extending by a predetermined amount the duration of the signal pulses of the phase difference signal;
• and
• comparing the phase difference signal with the reference signal whereby to provide an indication of the phase difference between the clock signal and the data signal and an indication of the magnitude of said phase difference, which indication varies linearly with said phase difference.

The method of digital signal phase detection comprising the steps of:

• provision of a reduced data digital output signal which changes state upon receipt of either only rising or only falling state transitions in a digital input signal;
• resynchronisation to provide a resynchronised reduced data signal upon receipt of a clock input signal and the reduced data output signal;
• phase-shifting to provide a first phase-shifted resynchronised reduced data signal upon receipt of the resynchronised reduced data signal and one or more clock signals;
• phase-shifting to provide a second phase-shifted resynchronised reduced data signal upon receipt of the first phase-shifted resynchronised reduced data signal and one or more clock signals;
• provision of a phase difference signal being the exclusive OR of the reduced data signal and the first phase-shifted resynchronised reduced data signal;
• provision of a reference signal being the exclusive OR of the resynchronised reduced data signal and the second phase-shifted resynchronised reduced data signal;
• and
• whereby the difference between the phase difference signal and the reference signal varies linearly with the difference in phase between the data signal and the clock signal used in resynchronisation.