Tuning the bandwidth of a phase-locked loop

US6049255A · kind A · utility

Assignee

• Telefonaktiebolaget LM Ericsson (Publ) · SE

Inventors

• Hans Hagberg · Malmö, SE
• Leif Nilsson · Lidingö, SE

Key dates

• Filing date: Jun 5, 1998
• Grant date: Apr 11, 2000
• Expiry date: Jun 5, 2018

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03L7/1072
• WIPO field: Basic communication processes
• WIPO sector: Electrical engineering

Abstract

A phase-locked loop bandwidth is tuned to a desired level by operating the phase-locked loop in a phase-locked condition at a first frequency and applying a step response to the phase-locked loop by causing the phase-locked loop to begin locking to a second frequency that is different from the first frequency. A parameter is then detected that is related to the applied step response and that is indicative of whether the phase-locked loop bandwidth is at the desired level. The phase-locked loop bandwidth is adjusted, and the steps of operating at the first frequency, applying the step response, detecting the parameter and adjusting the phase-locked loop bandwidth are repeated until the phase-locked loop bandwidth is at the desired level. Where the desired bandwidth level for tuning is not the operational bandwidth, the phase-locked loop bandwidth is further adjusted by a predetermined amount, thereby tuning the phase-locked loop bandwidth to an operational level. The step response may be applied by changing a frequency division value in a feedback path of the phase-locked loop. The detected parameter may be a pulse skip, which indicates that the bandwidth of the phase-locked loop is…