33 lines
1.9 KiB
Markdown
33 lines
1.9 KiB
Markdown
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---
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title: 相位连续、相干
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updated: 2022-02-14 07:52:08Z
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created: 2022-01-10 03:35:59Z
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---
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\> 节选自应用笔记《[射频与微波技术实用手册](file:///E:%5C%E6%96%87%E6%A1%A3%5C%E5%BA%94%E7%94%A8%E7%AC%94%E8%AE%B0%5C%E5%B0%84%E9%A2%91%E4%B8%8E%E5%BE%AE%E6%B3%A2%E6%8A%80%E6%9C%AF%E5%AE%9E%E7%94%A8%E6%89%8B%E5%86%8C.pdf "page=281")》P281
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DDS本身以相位连续方式开关频率
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# 概念
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### 相位==连续== \- Phase Continute
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很好理解，即频率变化时不会出现瞬时相位变化。对于DDS，当FTW变化时，累加器开始从当前所处的相位开始累加新的FTW
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### 相位==相干== \- Phase Coherent
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要求频率变化时瞬时切换到新的相位，就如新频率始终存在一样，相位如果突变，就会表现出明显的断层。
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> 或是说，从频率f1切换到f2再切换回f1，此时f1的相位完全没有变化就像从没有切换到f2一样
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>
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> "Phase Coherent frequency hopping implies that a device, starting at frequency f1, can be sent to a second frequency, f2, then returned to frequency, f1, exhibiting the exact same phase as if it never left original frequency, f1."
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对于DDS，要实现相位相干切换，必须在新旧频率具有相同的绝对相位时进行，具体参见*“在实现相位干零交越切换时必须遵循三条标准”*
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ADI仅有[HMC835LP6GE](file:///E:%5C%E6%96%87%E6%A1%A3%5C%E6%95%B0%E6%8D%AE%E6%89%8B%E5%86%8C%5CADI%5CPLLs%5Chmc835.pdf),[HMC1190LP6GE](file:///E:%5C%E6%96%87%E6%A1%A3%5C%E6%95%B0%E6%8D%AE%E6%89%8B%E5%86%8C%5CADI%5CPLLs%5Chmc1190.pdf),[HMC1197LP7FE](file:///E:%5C%E6%96%87%E6%A1%A3%5C%E6%95%B0%E6%8D%AE%E6%89%8B%E5%86%8C%5CADI%5CPLLs%5Chmc1197.pdf)支持相位相干，其它内置VCO的PLL均不支持
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# 直观对比
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两者对比如下如所示：
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