PLL apparatus
US8115527B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Feb 10, 2011 |
| Grant date | Feb 14, 2012 |
| Priority date | — |
| Expiry date | Feb 10, 2031 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03L1/02
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
There is provided an art to prevent an unstable operation due to temperature in a PLL apparatus in which a proper range of an amplitude level of an external reference frequency signal is specified and a control voltage is supplied to a voltage-controlled oscillator according to whether the amplitude level falls within the proper range or not. The PLL apparatus includes: a switching unit switching a signal that is to be supplied to a control voltage output unit between a signal of a phase comparison unit and a preset signal of a preset signal output unit; a protection circuit provided between a signal path of a reference frequency signal and a ground and having diodes that are connected in inverse parallel in order to regulate an amplitude level of the reference frequency signal; a temperature detection unit detecting an atmospheric temperature of the protection circuit; and a level detection unit detecting the amplitude level of the external reference frequency signal, and threshold values as references for the switching are set according to the detected temperature, thereby coping with a change in the amplitude level due to a temperature characteristic of the diodes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.