A Sub-100MHz Reference-Driven 25-to-28GHz Fractional-N PLL with −250dB FoM
A Sub-100MHz Reference-Driven 25-to-28GHz Fractional-N PLL with −250dB FoM
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具有 −250dB FoM 的低于 100MHz 参考驱动 25 至 28GHz 小数 N PLL
DOI：
10.1109/isscc42614.2022.9731628
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Weiyu Leng
中科院分区：
文献类型：
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作者：
Dihang Yang;D. Murphy;H. Darabi;A. Behzad;A. Abidi;S. Au;Sraavan R. Mundlapudi;Kejian Shi;Weiyu Leng
输出>25GHz的毫米波频率合成器不可避免地面临大闭环增益$f_{\mathsf{VCO}}/f\mathsf{ref}=N$的问题。参考输入上的相位噪声和杂散以及来自环路中参考输入的其他源的杂散被放大了N倍，必须使用窄环路带宽来限制由此产生的抖动。然而，现在环路无法充分抑制振荡器相位噪声，导致一个困难的权衡。在这些工作频率下，振荡器固有的噪声更大，因为用于数字调谐的电容器组极大地损害了整体LC槽质量因子$(Q)$。因此，对于低输出抖动，合成器需要分配比低于10ghz时不成比例的更多电流给VCO，使用带倍频器[1]的低于10ghz的VCO，或者必须将参考频率提高到> 100MHz[2],[3]，这超出了可靠的，广泛使用的晶体振荡器的范围。在这项工作中，我们提出了一种使用谐波混合（HM）锁相环[4]，[5]来抑制噪声放大的合成器，因此，允许使用带宽>5MHz的环路。此外，我们还介绍了一个只有一个谐振模式的耦合毫米波压控振荡器，在1MHz偏置下实现了188dB的FoM （VCO）。结合两者，该合成器由标准74MHz参考时钟驱动，功耗<13mW，提供25至28ghz输出，88fs rms抖动。它达到了−250dB的FoM （PLL）。
A mm-wave frequency synthesizer with output >25GHz inevitably faces the problems of a large closed-loop gain $f_{\mathsf{VCO}}/f\mathsf{ref}=N$. Phase noise and spurs on the reference input and from other sources in the loop referred to its input are amplified by $N$ A narrow loop bandwidth must be used to limit the resulting jitter. However, now the loop is unable to adequately suppress the oscillator phase noise, leading to a difficult trade-off. At these operating frequencies, the oscillator is inherently noisier since a capacitor bank for digital tuning greatly compromises the overall LC tank quality factor $(Q)$. Therefore, for low output jitter, the synthesizer either needs to allocate disproportionately more current to the VCO than at sub-10GHz, use a sub-10GHz VCO with a frequency multiplier [1], or the reference frequency must be raised to > 100MHz [2], [3], which is beyond the range of reliable, widely available crystal oscillators. In this work, we present a synthesizer that uses a harmonic-mixing (HM) PLL [4], [5] to suppress noise amplification and, therefore, allows the use of a loop with a bandwidth >5MHz. Also, we introduce a coupled mm-wave VCO with only one resonant mode that achieves an FoM (VCO) of 188dB at a 1MHz offset. Combining the two, this synthesizer, driven by a standard 74MHz reference clock, consumes <13mW to deliver 25-to-28GHz output with 88fs rms jitter. It reaches an FoM (PLL) of −250dB.