Phase locked loop fast lock method

Abstract

The present invention is a method for quickly locking a Type II phase-locked loop (PLL) without degrading the output signal in large quantities after a frequency jump. The method disclosed herein to reduce settling time and improve output clock quality during settling includes the steps of estimating the new frequency offset with a separate circuit outside the PLL loop to accurately measure the frequency of the input signal. Ramp up the integrator to the new frequency offset. Perform phase compensation or phase pulling. When edge-to-edge alignment is required, the remaining phase offset is compensated. Conversely, the residual phase offset is pulled while disabling the integrator in the PLL loop filter. Reduce bandwidth and / or reduce damping to allow PLL tuning. Switch the PLL to the final bandwidth and damping required by the application.

Description

[0001] Cross References to Related Applications [0002] This application claims the benefit of US Provisional Patent Application 60 / 703,285, filed July 28, 2005, which is incorporated herein by reference. technical field [0003] The invention relates to a phase-locked loop, in particular to a method for realizing locking in a relatively short time. Background technique [0004] One of the characteristics of a phase-locked loop (PLL) is the lock or setup time; that is, the time it takes for the PLL to lock to an input signal or to respond to frequency and phase jumps. In general, the lock time depends on the loop bandwidth of the PLL, the lower the loop bandwidth, the longer it takes for the PLL to lock. In the art, one generally defines the term "adjustment" as to within some relative or absolute precision. [0005] PLLs are not only used in telecom applications, but also in measurement technology (such as optical long-distance measurement), motor control, medical equipm...

AI Technical Summary

Problems solved by technology

[0017] Phase noise (drift and jitter) on the measured reference can degrade the accuracy of the measured frequency offset

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