Method and apparatus utilizing direct digital synthesizer and spread spectrum techniques for reducing EMI in digital display devices
US6982707B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 18, 2002 |
| Grant date | Jan 3, 2006 |
| Priority date | — |
| Expiry date | Dec 26, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2215/067
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A DDS circuit arranged to provide a selectable spread spectrum based output clock signal is described. The synthesizer includes a phase accumulator circuit, a reference clock source coupled to the phase accumulator circuit arranged to provide a reference clock signal, a frequency shifter unit coupled to the phase accumulator, a nominal phase source coupled to the phase accumulator coupled to the frequency shifter unit arranged to provide a nominal phase signal, and a modulated phase source coupled to the frequency shifter unit arranged to provide a modulation signal. The frequency shifter unit combines the nominal phase signal and the modulation signal to form a frequency shift signal as input to the phase accumulator which uses the frequency shift signal to sample the reference clock signal so as to produce the output clock signal having a central frequency and a frequency spread based upon the modulation signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.