| 摘要 |
An apparatus for performing sigma-delta modulation, comprises a pulse generator configured to generate a multi-bit signal having at least one pulse, the at least one pulse having a period P and a variable duty cycle; and sigma-delta modulator configured to modulate the multi-bit signal and to generate a digital code. Independent claims are also included for: (A) frequency synthesizer comprising a sigma-delta modulator configured to generate a random digital code based on a multi-bit frequency resolution control signal having at least one pulse; frequency divider configured to divide a voltage controlled oscillating frequency signal, based on the random digital code; phase frequency detector configured to detect a phase difference and a frequency difference between a reference frequency signal and the divided voltage controlled oscillating frequency signal; charge pump configured to pump charges corresponding to an output of the phase frequency detector; loop filter configured to filter a low frequency component of an output of the charge pump; and voltage controlled oscillator configured to generate the voltage controlled oscillating frequency signal based on an output of the loop filter; and (B) fractional-N frequency synthesizing method comprising generating a random digital code based on a multi-bit frequency resolution control signal having at least one pulse; dividing a voltage controlled oscillating frequency signal based on the random digital code; detecting a phase difference and a frequency difference between a reference frequency signal and the divided voltage controlled oscillating frequency signal; pumping charges corresponding to an output of the detecting step; filtering a low frequency component of an output of the pumping step; and generating the voltage controlled oscillating frequency signal based on an output of the filtering step. |
