Patent ID: 6946915

Claim:
A fractional-N frequency synthesizer for generating the high frequency signal at frequency that may be a non-integer multiple of the frequency of the reference signal, having a voltage controlled oscillator ( 3 ) the output of which is fed to a first order Delta-Sigma frequency discriminator ( 4 ) having a dual modulus frequency divider ( 1 ) and a D flip-flop ( 2 ), where a bit stream related to the frequency and phase of said voltage controlled oscillator is generated by using said reference signal and is then processed to generate a feedback error signal by using the information provided by comparing said bit stream with a bit stream generated by an accumulator digitally performing the first order Delta-Sigma modulation to the desired fractional number for the controlling of said voltage controlled oscillator after the said feedback error signal is properly filtered, amplified and converted, which will maximally suppress the fractional spurs due to the frequency quantization of said Delta-Sigma frequency discriminator.