Phase locked loop having plural selectable voltage controlled oscillators
US5389898A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 22, 1993 |
| Grant date | Feb 14, 1995 |
| Priority date | — |
| Expiry date | Jun 22, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/183
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The invention discloses a PLL formed by a phase detector, a filter, three VCO's (VCO1, VCO2, and VCO3), a multiplexer, and a frequency divider. The VCO1, VCO2, and VCO3 have different mean frequencies, each oscillating at a frequency controlled according to the voltage value of a phase control signal from the filter. The multiplexer selects one of the VCO's which operate in parallel. If a pulse of a digital phase difference signal UP indicating that an internal signal is delayed in phase with respect to a reference signal is output twice in succession, or if a pulse of a digital phase difference signal DOWN indicating that an internal signal is advanced in phase with respect to a reference signal is output twice in succession, a counter makes the multiplexer change its current VCO selection via a shift register. Accordingly, high-speed PLL pulling is achievable even if a PLL frequency variable-range is expanded.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.