Fractional phase-locked loop

A phase-locked loop, fractional technology, applied in the field of signal processing, can solve problems such as high spurs, and achieve the effects of eliminating spurs, eliminating quantization noise, and avoiding gain mismatch.

Pending Publication Date: 2021-06-11
BEIJING JINMAIJIE TECHNOLOGY CO. LTD.
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This mismatch introd

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  • Fractional phase-locked loop
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  • Fractional phase-locked loop

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Embodiment 2

[0028] Embodiment 2: On the basis of Embodiment 1, the small signal model of the phase-locked loop of this design is as follows Figure 7 As shown, in this design K DAC and K CP Naturally equal, thus avoiding the fractional spurs caused by the mismatch.

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Abstract

The invention discloses a fractional phase-locked loop which comprises a frequency/phase discriminator PFD, a charge pump CP, a Delta-Sigma modulator, a voltage-controlled oscillator VCO and a multi-mode frequency divider MMD.The input end of the frequency/phase discriminator PFD is connected with the multi-mode frequency divider MMD and a signal FCW, the output end of the frequency/phase discriminator PFD is connected with the charge pump CP, the charge pump CP is further connected with an integrator A and the voltage-controlled oscillator VCO, and the input end of the Delta-Sigma modulator is connected with a signal FCW. An independent digital-analog converter is not used any more, the digital-analog converter is combined with the charge pump, and the extracted quantization noise is directly input into the charge pump. As such, in the small signal model, the gain of the digital-to-analog converter will be normalized into the gain of the charge pump. Therefore, the gain mismatch of the digital-analog converter and the charge pump is avoided, and the aim of eliminating stray and quantization noise at the same time is fulfilled.

Description

technical field [0001] The invention relates to the technical field of signal processing, in particular to a fractional phase-locked loop. Background technique [0002] Common phase-locked loop structures are divided into integer phase-locked loops and fractional phase-locked loops. The significance of the fractional phase-locked loop is that its frequency is not an integer multiple of the reference clock frequency. Compared with the integer PLL, its design is more difficult. In modern wireless communication systems, fractional phase-locked loops are more commonly used, and their general structure is as follows figure 1 As shown, its main modules are composed of frequency / phase detector (PFD), charge pump (CP), loop filter (LP), voltage-controlled oscillator (VCO) and multi-mode frequency divider (MMD). The output frequency of the voltage-controlled oscillator is controlled by the control voltage, and its output is compared with the reference clock (REF) after passing thr...

Claims

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Application Information

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IPC IPC(8): H03L7/08H03L7/18
CPCH03L7/08H03L7/18
Inventor 张昌金沈羿禹沈杰
Owner BEIJING JINMAIJIE TECHNOLOGY CO. LTD.
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