VNA的校准方式那个更好

> {quote：title = RF_Like写道：} {quote}>大家好！
>>我想以两种不同的方式重新开始这个简单的测试：>> 1Way：*没有校准VNA *>我采用了可变阻尼元件（在0 ...... 50dB之间）。
我在0dB处进行了参考测量。
之后，我采取了不同的测量（10 dB，20dB和50dB）。
我从最后的测量值中减去参考测量值。
所以我得到了10dB 20dB和50dB：> >> 2路：* VNA的Witth校准*>我得到了相同的结果。
>>>我知道第二种方式比第一种方式更好，但我不知道为什么。
有什么帮助。
>>我赞成它。
>谢谢你。
你应该说你有什么VNA，也可能是固件。
我不知道变化的阻尼元件是什么。
VNA中的硬件“合理”好。
端口合理匹配50欧姆。
耦合器具有合理的方向性。对于某些型号，频率响应相当平坦。
通过方法＃1，您在校正频率响应方面做了合理的工作，但是在端口匹配的缺陷，耦合器的方向性没有得到纠正。
通过使用已知标准进行校准，VNA可以测量它们并能够确定其自身的错误。
进行测量时，如果启用了错误纠正，VNA会在显示结果之前纠正错误。
GPS /卫星导航系统可以告诉您行进的速度和方向。
有了这些信息，您可以更正车内的speedo和指南针。
由于校正了幅度和方向，因此您已执行矢量误差校正，如VNA所做的那样。
这是一个简化的解释。
您将在许多应用笔记中找到更好的描述。



     以下为原文

  > {quote:title=RF_Like wrote:}{quote}
> Hi All!
> 
> I want to relize this simple Test in Two diffrent Ways:
> 
> 1Way:*Without calibrating the VNA*
> I took a Variable Damping element (between 0.....50dB).  I took  a Reference measurement at 0dB. After that i took diffrent measurennts  ( 10 dB, 20dB and 50dB). I substract the Reference Measurement from the last measurements. so I got 10dB 20dB and 50dB:
> 
> 
> 2 Way:*Witth calibration of the VNA*
> i got the Same Results.
> 
> 
> I know the second Way is Better than the first way, but i dont know why.? is there any help.
> 
> I apreciate it.
> Thank u.

You should say what VNA you have, and probably firmware too. I don't know what a varying damping element is.

The hardware in  VNA is "reasonably" good. The ports are reasonably matched to 50 Ohms. The coupler has reason directivity.. For some models the frequency response is reasonably flat. 

By method #1 you are doing a reasonable job at correcting the frequency response, but imperfections in the match at the ports, the directivity of the coupler is not corrected.  

By doing a calibration,  with know standards,  the VNA measures them and is able to determine its own errors.  When a measurement is made,  with error correction enabled, the VNA corrects the errors before displaying the results. 

A GPS / Satellite Navigation system can tell you the speed and direction you are travelling.  Armed with thay information,  you could correct the speedo and compass in your car. Since both magnitude and direction is corrected, you have performed a vector error correction, as  VNA does. 

That's a simplified explanation. You will find a better description in many application notes.

谢谢你的Raspone。
我的意思是可变阻尼元件是一个可变衰减器。
但为什么我在两种情况下得到相同的结果？
谢谢



     以下为原文

  Thank you for the Raspone. I meant with variable damping element a variable attenuator. but why i get the same Result in both cases?

Thank you

因为在您的情况下，可变衰减器的输入匹配在不同的衰减器设置下不会（显着）改变。
当您以0 dB衰减进行初始扫描并对其进行标准化时，您实际上正在执行响应校准，该校准可校正电缆的频率响应以及DUT（被测设备）的初始不匹配。
现在，当您更改衰减级别并进行后续扫描时，如果输入匹配没有改变，那么您将获得相对于0 dB衰减设置的频率响应的正确差异。
因此，您可以进行合理的未校准测量的原因是1-您有一个表现良好的DUT，而您正在进行相对测量。



     以下为原文

  because in your case, the input match of your variable attenuator does not change (significantly) at different attenuator settings.  when you take the initial sweep at 0 dB attenuation and normalize it, you are essentially performing a response calibration that corrects for the frequency response of the cables and for the initial mismatch of your DUT (device under test).  now as you change attenuation levels and the take the subsequent sweeps, if the input match does not change, then you get the correct difference in frequency response relative to the 0 dB attenuation setting.  So the reasons you can make reasonable un-calibrated measurements are 1- you have a well behaved DUT and 2- you are making relative measurements.

感谢您的回复。
结论是：我们不需要口径



     以下为原文

  Thank you for this helpfull response. the conclusion is: we don#t need to calibr

> {quote：title = RF_Like写道：} {quote}>谢谢你的回复。
Ť



     以下为原文

  > {quote:title=RF_Like wrote:}{quote}
> Thank you for this helpfull response. t