Frequency synthesizer with controllable loop filter
US5559474A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 26, 1995 |
| Grant date | Sep 24, 1996 |
| Priority date | — |
| Expiry date | May 26, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L7/187
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In accordance with a loop open/close control signal, an analog switch closes or opens a loop including a voltage controlled oscillator, a variable frequency divider, a phase comparator, and a first loop filter, the analog switch, and a second loop filter. In order to reduce the change of frequency caused when the open loop state is set immediately after the output frequency is changed, the second loop filter uses a capacitor which shows properties of a small change of capacitance in response to an applied voltage and a small hysteresis. In another embodiment, the voltage controlled oscillator includes a second diode, one terminal of which is grounded, connected in reverses parallel to a first diode switch which switches the output oscillation frequency ranges of the voltage controlled oscillator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.