Patent ID: 7786772
Filing Date: 2010-08-31
Classification: H03L

Abstract:
1. A method for reducing in-band spurs in a fractional-N synthesizer, comprising: generating a compensated current signal having in-band spurs at frequencies within a predetermined frequency bandwidth; selectively dithering the compensated current signal with a sufficient dither level to spread the energy of in-band spurs beyond the frequency bandwidth associated with the loop filter, wherein selectively dithering the compensated current signal comprises dynamically adding at least one magnitude of current to the compensated current signal to produce the dithered compensated current signal by: filtering the selectively dithered compensated current signal so as to attenuate remaining in-band spurs beyond the frequency bandwidth; and applying the filtered compensated current signal to a voltage controlled oscillator (VCO) so as to generate a VCO signal with reduced in-band spurs proportional to the compensated current signal.