Phase-locked loop frequency synthesizer structure for improving in-band phase noise performance

Abstract

The invention discloses a phase-locked loop frequency synthesizer structure for improving in-band phase noise performance. The phase-locked loop frequency synthesizer structure consists of two loops, namely a coarse tuning loop and a fine tuning loop, wherein the coarse tuning loop is used for selecting different frequency control words to realize the frequency locking of the loop, the fine tuning loop is used for realizing the phase locking of the loop. When in a locking state, the coarse tuning loop can be turned off and only the fine tuning loop works. By utilizing the structure provided by the invention, the problem that the in-band phase noise of the traditional structure is restricted by a frequency divider can be solved. By introducing the fine tuning loop, the noise of the frequency divider can be effectively reduced in the locking state and the in-band phase noise performance of the phase-locked loop frequency synthesizer can be improved.

Description

technical field [0001] The invention relates to the technical field of communication, in particular to a phase-locked loop frequency synthesizer structure for improving the performance of in-band phase noise. Background technique [0002] The phase-locked loop is a key module in the design of the wireless transceiver. It outputs a series of high-precision frequency signals to provide local oscillator signals for the frequency conversion of the transceiver. Among various phase-locked loop structures, the charge pump phase-locked loop is widely used because of its excellent characteristics of low power consumption, high speed, low jitter and low cost. The charge pump phase-locked loop structure is as figure 1 As shown, it consists of a phase-frequency detector, a charge pump, a loop filter, a voltage-controlled oscillator, and a frequency divider connected between the phase-frequency detector input and the voltage-controlled oscillator output. The phase and frequency detecto...

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Problems solved by technology

[0006] In view of this, the main purpose of the present invention is to provide a kind of phase-locked loop frequency synthesizer structure that is used to improve the in-band phase noise performance, to solve the problem that the traditional structure in-band phase noise is limited by the frequency divider, by introducing precision Tuning loop, effectively reducing the noise of the frequency divider in the locked state, and improving the in-band phase noise performance of the PLL frequency synthesizer

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