Patent ID: 8183936
Filing Date: 2012-05-22
Classification: H03L

Abstract:
1. A phase-locked loop frequency synthesizer, comprising: a reference route sigma-delta modulator feedback circuit for generating a frequency control code according to a fraction frequency control code and an integer frequency control code; a reference phase integration circuit for generating and outputting reference phase information according to the frequency control code generated by the reference route sigma-delta modulator feedback circuit; a phase/frequency detector for detecting feedback phase information and the reference phase information, and outputting phase difference information; a loop filter including a locking process state machine circuit and a loop filter circuit with a loop parameter, the locking process state machine circuit being for adjusting the loop parameter according to the phase difference information, and the loop filter circuit being for outputting a control signal according to the adjusted loop parameter; an oscillator for generating a frequency output signal according to the control signal outputted by the loop filter circuit; and a feedback phase integration circuit for generating the feedback phase information according to the frequency output signal provided by the oscillator, and outputting the feedback phase information to the phase/frequency detector, wherein, the reference route sigma-delta modulator feedback circuit pulls a negative feedback from the phase/frequency detector to the reference phase integration circuit, enabling the oscillator to generate the frequency output signal corresponding to the reference signal.