Method and apparatus for achieving fast phase settling in a phase locked loop

US5754607A · kind A · utility

Assignee

• Alcatel Network Systems, Inc. · US

Inventors

• William E. Powell · Hersbruck, DE
• David Hayes · Northville, US

Key dates

• Filing date: May 10, 1995
• Grant date: May 19, 1998
• Expiry date: May 10, 2015

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S331/02
• WIPO field: Basic communication processes
• WIPO sector: Electrical engineering

Abstract

A method and an apparatus are provided to achieve fast phase settling when a reference signal for a phase locked loop changes from a first frequency to a second frequency, such as during holdover recovery in a synchronous optical network. The present method acquires the second frequency with a phase locked loop (24). After the frequency is acquired, the integral register (39) of the phase locked loop (24) is loaded with the contents of the output frequency register (34) of the phase locked loop (24). The phase detector (28) of the phase locked loop (24) is then realigned to the reference signal.