Downsampling phase locked loop for preventing in-band noise from being amplified to square times of frequency dividing ratio

Abstract

The invention discloses a down-sampling phase-locked loop that prevents in-band noise from being amplified to the square of the frequency division ratio. Down-sampling phase detector, transconductance charge pump, loop filter, and voltage-controlled oscillator; frequency-locked loop, including, three-state frequency detector, dead-zone generator, differential charge pump, and frequency converter. When the down-sampling phase-locked loop circuit of the present invention is locked, the frequency-locked loop does not work, and the down-sampling loop does not contain a frequency divider, so from the reference frequency signal, the frequency and phase detector and the charge pump The noise of the phase-locked loop will not be amplified to the square of the frequency division ratio at the output of the phase-locked loop. It can be widely used in clock generation circuits based on phase-locked loops in analog integrated circuits, especially clock generation with high frequency and low phase noise. .

Description

technical field [0001] The invention relates to a phase-locked loop structure, in particular to a down-sampling type phase-locked loop structure which prevents in-band noise from being amplified to the square times of the frequency division ratio. Background technique [0002] The phase-locked loop circuit is the core unit circuit of the analog integrated circuit, especially in the clock generation circuit with high frequency and low phase noise, the phase-locked loop determines the performance index of the clock generation circuit. At present, there are various loop structures of phase-locked loops, including charge-pump phase-locked loops, self-bias phase-locked loops, multi-loop phase-locked loops, etc. There are fewer phase-locked loops that use down-sampling loop structures. figure 1 It is the loop structure of the traditional charge-pump phase-locked loop. The main building blocks include a three-state frequency and phase detector, a charge pump, a loop filter, a volt...

AI Technical Summary

Problems solved by technology

The phase-locked loop is characterized by a simple structure and a stable loop, but its disadvantages: due to the existence of the frequency divider in the loop, the noise from the phase detector / charge pump and the frequency divider (also known as in-band noise) When passed to the output of the phase-locked loop, it will be enlarged by the square of the frequency division ratio

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