Loop filter of a phase-locked loop
US5783971A · kind A · utility
16Cited by
4References
4Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Dec 4, 1996 |
| Grant date | Jul 21, 1998 |
| Priority date | — |
| Expiry date | Dec 4, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/093
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In a phase locked loop, a loop filter is provided between a charge pump and a VCO. The loop filter includes a passive integrator connected to a non-inverting input of an operational amplifier which supplies a tuning voltage to the VCO. The passive integrator functions to short-circuit pulses from the charge pump to ground, to prevent them from appearing at the output of the operational amplifier. The VCO tuning voltage area may be expanded by shifting a DC voltage level at the inverting input of the operational amplifier. Further low-pass filtering may be provided at the output of the operational amplifier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.