如何用VNA进行微带线表征

我想我已经确定了一个找到测量结果的解决方案。
我相信我需要使用VNA的TDR功能来找到微带的特征阻抗。
但我仍然不确定如何找到传播速度（相速度）。
我也希望能够找到损失。



     以下为原文

  I think I've identified a solution to find my measurements.  I believe I need to use the VNA's TDR capabilities to find the characteristic impedance of a microstrip. But I'm still unsure of how I could find the propagation velocity (phase velocity).  Also I would like to be able to find the loss as well.

因此，在与我的一些教授交谈之后，似乎使用s参数实际上是使用VNA的更好方法。
S11参数实际上显示了特征阻抗是什么，然后我可以使用S11和S21参数来推导介电常数。
有谁知道一个很好的来源，说明如何做到这一点？



     以下为原文

  So after talking with some of my professors, it seems that using the s-parameters would actually be the better way to go with the VNAs.  The S11 parameter actually shows what the characteristic impedance is, then I can use the S11 and S21 parameters to derive the dielectric constant.  Does anyone know of a good source that shows how to do this?

> {quote：title = bran5写道：} {quote}>所以在与我的一些教授交谈之后，似乎使用s参数实际上是更好的方式来使用VNA。
S11参数实际上显示了特征阻抗是什么，然后我可以使用S11和S21参数来推导介电常数。
有谁知道一个很好的来源，说明如何做到这一点？
我不是这方面的专家 - 我自己从来没有这样做过。
但是，我认为您使用时域选项的想法是最好的。
您将在PCB上的RF连接器（可能是SMA）和微带线之间出现一些不连续性。
同样地，在微带线的末端，无论线路被终止，都会有一些不连续。我认为这样做的方法可能是*使用变换菜单来查看时域。
*在微带的中间放置一个门，这样就可以消除连接器的影响。
*转换回频域，查看微带线的阻抗等，没有明显的PCB /连接器接口的不连续性。
本书中有一整章介绍了本书中的TDR功能，以及关于测量无源器件的另一章。
这本书中将提供您需要的信息。
http://www.amazon.com/Handbook-Microwave-Component-Measurements-Techniques/dp/1119979552/编辑：drkirkby于2013年4月30日下午3:27



     以下为原文

  > {quote:title=bran5 wrote:}{quote}
> So after talking with some of my professors, it seems that using the s-parameters would actually be the better way to go with the VNAs.  The S11 parameter actually shows what the characteristic impedance is, then I can use the S11 and S21 parameters to derive the dielectric constant.  Does anyone know of a good source that shows how to do this?


I'm no expert on this - I have never done it myself. 

However, I think your idea of using the time-domain options are best. You are going to have some discontinuity between the RF connector on your PCB (probably SMA) and the microstrip. Likewise at the end of the microstrip there is going to be some discontinutiy to whatever the line is terminated in. I think the way to do this is probably

* Use transform menu to look at the time domain. 
* Put a gate around the middle of the microstrip, so the effect of the connectors is removed. 
* Transform back to the frequency domain to look at the impedance etc of just the microstrip, without the discontinuty of the PCB/connector interface being evident. 

There is a whole chapter in this book on the TDR functionality in this book, as well as another chapter on measuring passive devices. There will be the information you need in that book. 

http://www.amazon.com/Handbook-Microwave-Component-Measurements-Techniques/dp/1119979552/

Edited by: drkirkby on Apr 30, 2013 3:27 PM

测量电路板的介电常数是使用VNA可以做的更有趣的事情之一。
HP AN-380和HP AN-？
（这个没有没有）解释了几种测量approaches的方法。
据我记得，有2种常用的方法用于测量ɛ，电容法和共振法。
通过使用电容方法，您应该能够接近电路板的额定值（边缘电容是有限的），而谐振方法不需要矢量分析仪，可以使用频谱分析仪等标量工具。
共振方法的数学可能有点毛茸茸，如果你已经采用了电磁学，你应该知道空腔谐振器的方程式。
对于那些测量，我会建议你从一个已知ɛ的电路板开始并向后工作。
FR4和这样的低成本层压板具有不同的制造商和板材之间的变化，因此在解决这些问题之前，请先完成您的程序。
您应该尝试从当地的微波层压板分销商处获取一些样品并进行一些实验。
这可以使您对雇主更有价值，因为您具有进行微波和RF测量的实际经验。
+ LS Napoli和JJ Hughes，“精确测定微波集成电路基板微波介电常数的简单技术”，IEEE微波理论与技术交流，1971年7月。+和：+ Howell，“快速准确
测量微波集成电路基板的介电常数的方法“，IEEE微波理论与技术交易，1973年3月+您的学校图书馆可能能够帮助您处理这些文章。
BR。
Thomas.Edited：ThomasSK于2013年5月11日上午11:33



     以下为原文

  Measuring the dielectric constant of an board is one of the more interesting things one can do with an VNA.
HP AN-380 and HP AN-? (this one dont have an no) explains several approaches to measuring ɛ. 

As far as I remember there are 2 common metods for measuring ɛ, the capacitance method and resonance method. 
By using the capacitance method, you should be able to come close to what the board is rated for (fringe capactiances are limiting), while the resonance method would not require vector analyzer and can be done with scalar tools like an spectrum analyzer. 

The math for the resonance method can be a bit hairy, if you have taken electromagetics, you should know the equation for an cavity resonator. The PCB is treated as an re

For those measurment, I would reccomend you to start with an board with an known ɛ and work backwards. FR4 and such inexpencive laminates have ɛ that vary both between the manufacturers and from sheet to sheet, so get your procedure in place before you tackle those.  You should try to get some samples from the local distributor of microwave laminates and do some experiments. This should make you more valuable to an employer, as you have actual experience doing microwave and RF measurements. 


+ L. S. Napoli and J. J. Hughes, “A Simple Technique for the Accurate Determination of
the Microwave Dielectric Constant for Microwave Integrated-Circuit Substrates”, IEEE
Transactions on Microwave Theory and Techniques, July, 1971. +
and:
+ Howell, “A Quick Accurate Method to Measure the Dielectric Constant of Microwave
Integrated-Circuit Substrates”, IEEE Transactions on Microwave Theory and Techniques,
March, 1973 + 
Your school library may be able to help you with those articles. 

BR.
Thomas.

Edited by: ThomasSK on May 11, 2013 11:33 AM