Direct digital frequency synthesis enabling spur elimination

摘要

The invention relates to a phase lock loop, comprising : means (DIFFERENCE ENGINE)responsive to an waveform having a frequency attribute and an input bitstream representing a desired waveform for producing an output bitstream representing a difference quantity between the analog waveform and the desired waveform; a filter and a digital to analog converter (DAC) cooperating to produce a filtered analog difference signal; a controlled oscillator (VCO) that produces the analog waveform; and a first capacitor coupling the filtered analog difference signal and an input terminal of the controlled oscillator.