Slave clock generation system and method for synchronous telecom

Details Slave clock generation system and method for synchronous telecom Slave clock generation system and method for synchronous telecom

1999-04-23

2000-09-19

Wambach, Margaret R.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Clock or pulse waveform generating

327 2, 327 7, 327 12, 327144, 327145, 327147, 327150, 327298, 327299, 327407, H03K 300

Patent

active

061218162

ABSTRACT:
A slave clock generation system and method suitable for use with synchronous telecommunications networks generates one or more slave clocks from a selected reference clock using a direct digital synthesis technique. A multiplexer selects a reference clock from a number of available sources, each of which can be at its own spot frequency, based on a predetermined selection order. Toggle detectors monitor each of the available clock sources, and block the selection of any that are not within a specified frequency range. A local oscillator establishes short-term and long-term measurement periods; the cycles of the selected reference clock are counted over consecutive short-term measurement periods to determine the relative frequency of the selected clock with respect to the frequency of the local oscillator. The cycle counts are fed to a phase-to-clock converter, which produces a slave clock output having a frequency that varies with the relative frequency measured for the selected clock. Rounding errors are countered by monitoring both the generated slave clock and the selected reference clock over a long-term measurement period, with the difference between these two cycle counts used in a feedback path to correct the output frequency. The invention's mostly-digital implementation improves its noise-rejection and suppression characteristics, and enables the system to be integrated on a common substrate.

REFERENCES:
patent: 4562402 (1985-12-01), Irvin
patent: 5146585 (1992-09-01), Smith
patent: 5864252 (1999-01-01), Tran et al.

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