Fast locking variable frequency phase-locked loop
US5757238A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 19, 1996 |
| Grant date | May 26, 1998 |
| Priority date | — |
| Expiry date | Aug 19, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/189
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
According to the preferred embodiment of the present invention, a phase-locked loop is provided that overcomes the limitations of the prior art by facilitating fast locking on transition to a different output frequency. The phase-locked loop comprises an oscillator that provides a phase-locked loop output signal at various selected frequencies; a feedback divider; a phase comparator; a memory storage mechanism for storing phase-locked loop control information corresponding to selected output frequencies; and a digital circuit mechanism that receives the control information from the memory storage mechanism on transition to a different output frequency. The control information includes a digital counter value corresponding to the last recorded phase difference of the output signal at the different output frequency. On transition, this information is loaded directly to the digital circuit mechanism, reducing the need and time required for the phase comparator operation to drive the PLL to lock. Thus, the phase-locked loop can quickly achieve phase lock at the different operating frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.