VNA规范一般问题理解

> {quote：title = SOLT_guy写道：} {quote}>这是一个关于理解VNA规范的一般性问题。
>>我拥有8753C（但我必须使用其他网络分析仪完成我的工作），我必须与客户和管理层就网络分析仪测量的准确性进行对应。
因此，我的回复必须准确并且不能“一般”正确，因为这些测量可能与校准实验室测试或具有严格标准的一些其他应用相关联。
>>>如果我看一下“相位特性” - 频率响应偏离线性部分的接收机仪器规格，从300KHz到3 GHz有一个规格+或负3度。
根据这个规范。
我看到了一个图表。
>如果我回忆正确，这是原始测量。
因此，与校准测量得到的结果无关>我需要根据实际相角测量的正式断言来解释该图。
>>从图中可以看出，6 GHz时线性偏离2度（参见用户手册第19-873C仪器规格部分），3 GHz时偏差约1度。
>>让我们说我运行了性能测试，我的性能测试数据输出与图表完全相同。
>>>我能告诉想知道相位测量精度的客户，我的相位测量值在6 GHz±2度和3 GHz一度（测试数据）吗？
>您必须添加测试方法的不确定性或错误。
>或者我只能说安捷伦在正负3度指定其NA相位测量值（也就是说，如果“线性相位特性”的这种解释等同于相位测量的相位角“精度”测量）。
>同样，这是未经纠正的反应。
>术语“线性相位特征”是否等于相位角“精度”测量值？
>不，它正是它所说的：它是与线性相位的偏差。
但相位精度应包括线性相位效应。
在测试集端口添加一段线路将不会明显改变线性相位的偏差（它将基本上只有线性相位，即直接随频率变化的相位），但肯定会改变绝对相位数。
>请帮我准确定义这些规范的真正含义。
>>感谢您过去的回复。
>>编辑：SOLT_guy于2012年5月21日上午4:11 >>编辑：SOLT_guy于2012年5月21日上午4:13 >>编辑：SOLT_guy于2012年5月21日下午3:54 >>编辑：
SOLT_guy于2012年5月21日下午3:57 >>编辑：SOLT_guy于2012年5月30日上午1:07



     以下为原文

  > {quote:title=SOLT_guy wrote:}{quote}
> This is a general question about understanding VNA specs.
> 
> I own a 8753C (but I have to use other network analyzers for my job) and I have to correspond with customers and management with respect to the accuracy of the network analyzer measurements.    Therefore, my replies have to be exact and cannot be "generally" correct because these measurements may be associated with calibration laboratory tests or some other application with exacting standards.
> 
> If I look at the receiver instrument specifications under the section, "Phase Characteristics" - Frequency Response Deviation from Linear, there is a spec + or minus 3 degrees from 300KHz to 3 GHz.   Under this spec.  I see a graph.
> 
If I recollect correctly, this is for raw measurements.  So it is unrelated to the results you get with calibrated measurements
> I need to interpret this graph with regard to what can be formally asserted with respect to actual phase angle measurements.
> 
> From the graph I can see that there is a 2 degree deviation from linear at 6 GHz (see page 19 - 8753C  instrument specifications section of the user manual) and about one degree deviation at 3 GHz.  
> 
> Let's say I ran a performance test and my performance test data output was exactly the same as the graph.
> 
> Can I tell a customer who wants to know the accuracy of my phase measurements that my phase measurement is within plus or minus 2 degrees at 6 GHz and one degree at 3 GHz (data from a test)?
>
You must add the uncertainty or error of the test method. 
> Or am I only entitled to say that Agilent specifies its NA phase measurements at plus or minus 3 degrees (that is, if this interpretation of "linear phase characteristics" is equivalent to the phase angle "accuracy" measure of a phase measurement).
>
Again, this is uncorrected response. 
> Is the term "linear phase characteristics" equivalent to the phase angle "accuracy" measure?
> 
No, it is exactly what it says: it is the deviation from linear phase.   But phase accuracy should include the linear phase effects.  Adding a length of line to your test set port will not appreciable change the deviation from linear phase (it will and substantially only linear phase, that is phase that changes directly with frequency), but will certainly change the absolute phase number.
> Please help me define exactly what these specifications are really saying.
> 
> Thank you for your past replies.
> 
> Edited by: SOLT_guy on May 21, 2012 4:11 AM
> 
> Edited by: SOLT_guy on May 21, 2012 4:13 AM
> 
> Edited by: SOLT_guy on May 21, 2012 3:54 PM
> 
> Edited by: SOLT_guy on May 21, 2012 3:57 PM
> 
> Edited by: SOLT_guy on May 30, 2012 1:07 AM

亲爱的Dunsmore博士;
谢谢你的回复，这是最具启发性的。
关于相位角精度的测量，我读了一篇两页的文章（由Bird公司出版），标题为“VSWR：电压直立率”。
文章在第2页，第二段说：“开槽线仍然是最准确的仪器，产生VSWR和相角信息”我上传了文章，以便您可以验证其真实性。
这篇文章似乎没有过时。
我的问题是，是否有一项独立的研究报告证实现代网络分析仪比开槽线更准确地进行相位测量？
我意识到每个特定单元的“工艺”可能决定了它的实际测量精度，但我指的是一个一般情况，即被测单元是由制造商和型号识别的随机样本（“现成的”）
。
我知道进行了一项独立研究，比较了专用TDR单元与NA TDR单元，并暗示NA TDR单元在特定条件下输出的数据测量不确定性低于专用TDR单元（“使用VNA和TDR测量不确定度的比较
同轴电缆，“由Paul Pino，WL Gore＆amp; Associates Inc.，Landenberg，PA - Cables＆amp; Connectors 2010 A Microwave Supplement to Microwave Journal）。
是否有研究表明，与使用相对现代的网络分析仪进行相角测量相比，开槽线相位角精度测量结果相比较？编辑：SOLT_guy于2012年6月3日上午9:36



     以下为原文

  Dear Dr. Dunsmore;

      Thank you for your reply, it was most enlightening.   

       With regard to the measurement of phase angle accuracy, I read a two page article (published by Bird corporation), entitled, "VSWR: Voltage Standing Ratio."   The article says on page 2, second paragraph down:

"The slotted line is still the most accurate instrument, yielding both VSWR and phase angle information"

       I have uploaded the article so that you may verify its authenticity.   The article does not appear to be dated.   

       My question is, was an independent study ever published which verified that the modern network analyzer makes more accurate phase measurements than the slotted line?    I realize that the "workmanship" of each particular unit  may determine its actual measurement accuracy, but I am referring to a general case whereby the units under test are random samples ("off the shelf") that are identified by the manufacturer and model number.

       I know that an independent study was conducted comparing dedicated TDR units vs. NA TDR units and it was implied that the NA TDR units output less uncertainty in their data measurements than dedicated TDR units under specific conditions ("Comparision of VNA and TDR Measurement Uncertainty Using Coaxial Cables," by Paul Pino, W.L. Gore & Associates Inc., Landenberg, PA - Cables & Connectors 2010 A Special Supplement to  Microwave Journal). 

        Was a study ever presented that compared slotted line phase angle accuracy measurements as compared to the phase angle measurements using a, relatively, modern network analyzer?

Edited by: SOLT_guy on Jun 3, 2012 9:36 AM

附件

• Bird Article.pdf759.4 KB
  

我不知道有关开槽线精度的任何研究。
自从现代纠错技术的发明以来，我怀疑是否有人认真地使用开槽线作为测量超过30年。
开槽线有许多可以容易出错的区域，包括沿线的探针变化和探测器问题，我认为这些区域很难分析并创建误差范围。



     以下为原文

  I do not know of any study of the accuracy of slotted lines.  I doubt that anyone has seriously used slotted lines as measurements for more than 30 years, since the invention of modern error correction techniques.  Slotted lines have many areas that are open to error including probe variation along the line and detector issues, which I would suppose are very difficult to analyze and create error bounds for.

亲爱的Dunsmore博士;
非常感谢您的反馈。
我倾向于同意您对探头，探测器和其他模拟性设备可能产生的错误的潜在可能性的看法。
但是，我确实认为过于依赖数字化的数据解释有其缺陷。
模拟设备可能不完全准确，但它们作为“球场”数字的输出非常可靠。
我希望有人可能想为我们的讨论做出贡献。
我确实认为必须在某个时间进行比较，遗憾的是，其结论可能只与其发表的时间框架相关。
当网络分析仪处于发展阶段时，可能存在时间范围，而“时隙线”可能是“成熟”技术。
我仍然希望阅读有关这两种测量设备的文章或研究结果。
再次感谢您的反馈，希望有人能为此次讨论做出贡献。



     以下为原文

  Dear Dr. Dunsmore;

       Thank you very much for your feedback.  

        I would tend to agree with your opinions regarding the inherent potential for errors which may arise from probes, detectors, and other devices of an analog nature.   But, I do believe that becoming too dependent upon digitized interpretations of data has its pitfalls.   Analog devices may not be perfectly accurate but their output as a "ballpark" figure is very reliable.  

      I was hoping that someone out there may want to contribute to our discussion.   

      I do believe a comparision had to have been done at some time, unfortunately, its conclusions may only be relevant for the time frame that it was published.   

     It is probable that a time frame existed when the network analyzer was in its developmental stage while the "slotted line" was probably a "mature" technology.   I would still like to read the findings of the article, or the study, with regard to these two measurement devices.   

      Again, thank you for your feedback and, hopefully, someone will contribute to this discussion.

相反，在过去的12年里，我使用了一条开槽线进行100 GHz的测量。
但是，我不推荐它，因为它非常繁琐，需要大量注意细节。
探针通常耦合到直接检测器，该检测器通常不具有外差系统的灵敏度（即使使用斩波/同步检测的方案）。
调整探头深度时，驻波模式的灵敏度和失真之间存在折衷，这取决于VSWR的大小。
你需要在沿着开槽线的几个点进行测量，这样你就可以推断到线的末端等等。所有得到你的是一个频率点。
我已经在~30 GHz和~100 GHz下使用这种方法来测量喇叭反射系数和环氧树脂的介电常数，但是这个词很令人厌烦。
我不认为我曾经用现代（甚至不那么现代）的VNA实现了可能的准确性。
在我看来，使用开槽线的唯一原因是，如果你有一个并且你无法接受VNA ;-)我所知道的最好的（实际上，唯一的）参考是老Rad。
实验室。
1940年代和50年代（可能是Marcuvitz）的系列......



     以下为原文

  On the contrary, I have used a slotted line for measurements at 100 GHz within the last 12 years. However, I would not recommend it as it is very tedious and requires a lot of attention to detail. The probe is usually coupled to a direct detector which generally does not have the sensitivity of a heterodyne system (even when a chopped/synchronously detected scheme is used). There is a compromise between sensitivity and distortion of the standing wave pattern when you adjust the probe depth, and that depends on the magnitude of the VSWR. You need to do measurements at several points along the slotted line so you can extrapolate to the end of the line, etc. And all that gets you is one frequency point.

I have used this method at ~30 GHz and ~100 GHz to do things like measure horn reflection coefficients and the dielectric constant of epoxy, but tedious is the word that springs to mind. I do not think that I ever achieved anything like the accuracy possible with a modern (or even not-so-modern) VNA. The only reason, in my mind, for using a slotted line is if you have one and you can't get your hands on a VNA ;-)

The best (actually, only) reference I know of is the old Rad. Lab. series from the 1940's and 50's (probably Marcuvitz) ...

亲爱的JWL;
谢谢您的回复。
在我回复之前，我倾向于等待一段时间，以便对该主题感兴趣的每个人都可以回复最后一条消息。
我真的很忙，直到现在我都无法回复此消息。
我希望你仍然可以阅读这个回复。
很抱歉迟来的回复。
我倾向于认为虽然开槽线可能不方便操作，但我倾向于相信人们仍然可以从该设备输出的数据中学习。
实验数据输出可以与尚未公布或至少普及的数学分析相关联。
您对此主题有何看法？



     以下为原文

  Dear JWL;

       Thank you for your reply.   I tend to wait some time before I reply so that everyone who is interested in the topic can reply to the last message.   I got really busy and I couldn't reply to this message until now.   I hope that you are still able to read this reply.   Sorry for the belated reply.

       I tend to believe that although the slotted line may be inconvenient to operate, I tend to believe that one can still learn from the data that this device outputs.     

       The experimental data outputs may be associated with a mathematical analysis which has yet to be published, or, at least popularized.   What are your thoughts on this topic?

我猜想50年前发布了有关插槽线的所有兴趣。



     以下为原文

  I would guess everything of interest on slotted lines was published 50 years ago.

亲爱的JWL;
谢谢您的回复。
我实际上是出于学术原因考虑购买一个工作的开槽线系统。
如果您计划出售您的工作系统，请私下给我回信。



     以下为原文

  Dear JWL;

      Thank you for your reply.  

      I am actually thinking about purchasing a working slotted line system for academic reasons.  Write back to me privately if you plan on selling your working system.

SOLT_guy，您最好的文档来源是一些NIST出版物，涉及该学科的测量分析。
您可以找到有关纠错VNA和插槽线技术所需的信息。
我相信在8510系列推出后不久，第一批出版的是1986年或1987年。
我相信它还有几个8409系统，这是一个自动8410系统，它占用了三个机架系统，工作频率从100 MHz到18 GHz。
我使用过这个系统，需要付出很多努力才能让它具有可重复的测量结果。
你必须是一个非常熟练的计量学家。
我知道我们已经获得了.005 dB / 10 dB的可重复性，我相信+/- 2度到12.4 GHz和+/- 3度@ 18 GHz。
我们将测量结果与VM7系统和NIST工件进行了比较，以确保我们获得高质量的结果。



     以下为原文

  SOLT_guy,

Your best source for documentation would be some NIST publications concerning the measurement analysis in this discipline.   You could find the information you need to concerning Error correcting VNA's vs the slotted line technique.  I believe one of the first ones published was about 1986 or 1987 shortly after the 8510 series was introduced.  I believe the also had several 8409 systems which was an automatic 8410 system which took up three rack systems to work from 100 MHz - 18 GHz.   I had used this system, an it took a lot of effort to get it to have repeatable measurements.  You had to be a very skilled metrologist.  I know we had gotten .005 dB/10 dB repeatablity in magnitued and I believe +/- 2 deg to 12.4 GHz and +/- 3 deg @ 18 GHz.  We had compared measurements with a VM7 system and NIST artifacts to ensure we had quality results.

亲爱的DHamilton;
感谢您的回复，我必须为迟来的回复道歉。
我有时候很忙，几周都无法登录这个网站。
一个简单的问题：平均而言，关于您对开槽线相角数据与网络分析仪相角测量的实验比较，与NIST负载相比，您能告诉我哪些数据值更一致，开槽线或网络
分析？
再次感谢您的投入。



     以下为原文

  Dear DHamilton;

      Thank you for your reply and I must apologize for my belated reply.  I get so busy sometimes that I can't log onto this web site for weeks.

      One quick question:

On average, with regard to your experimental comparision of phase angle data from slotted lines vs. network analyzer phase angle measurements, as compared to the NIST loads, can you tell me which data values were more consistent, slotted line or network analyzer?

      Thank you again for your input.

对于大多数用户而言，纠错VNA将提供最可重复的结果。
使用开槽线的熟练计量师可以得到类似的结果。
然而，正如JWL所说，要获得可重复的结果需要大量的练习。
一旦你能够做到这一点，那么你可以依靠你的测量是正确的。
你很愿意向新生展示这种技术，这样他们就可以理解测量技术以及它是如何完成的。
我知道当我开始这个领域时，你必须先手动演示你的技能，然后才能触摸自动化系统。
通过这种方式，您可以更好地确定不良读数的来源，然后解决它们。



     以下为原文

  For most users the error correcting VNA will give the most repeatable results.   A skilled metrologist in using slotted lines can get similar results.  However, as JWL stated it takes a lot of practice to get repeatable results.  Once you are able to do that, then you can rely on your measurements being correct.   It is good that you are willing to demonstrate to new students this technique as so they may understand the measurement technique and how it is accomplished.  I know when I started this field you had to demonstrate you skills manually before you could even touch an automated system.  This way you can better determine the source of poor readings, then resolve them.

亲爱的DHamilton;
谢谢您的回复。
“可重复性”对我来说不是最重要的。
我正在为我的测量寻求“准确性”。
NA具有许多功能，例如平均，平滑等。它输出了良好的数据，但我想要一个即使操作员技能，注重细节和更多时间也需要返回“准确”测量的测试仪器。
我很好奇哪个测试仪器输出数据“最接近”给定负载的NIST指定相角。
此外，我认为，当使用网络分析仪时，时隙线可能输出一些可能不明显的相关物理信息。
这种信念只是假设。
由于我没有开槽线，在购买之前我不会知道这个问题的答案。
也许你可以告诉我一些我错过的东西。
希望JWL有一天会以合理的价格出售他的系统，我很幸运能看到他的广告并购买它。
你可以在e-Bay购买很多插槽线部件，但除非你获得所有部件，否则它们都毫无价值。
将工作系统“拼凑”在一起可能会浪费时间和金钱。
我从经验中学到了，相信我。
很高兴听到你的DHamiliton，希望我能再次收到你的来信。



     以下为原文

  Dear DHamilton;

      Thank you for your reply.

      "Repeatibility" is not the highest priority for me.   I am seeking "accuracy" for my measurements.   The NA has a lot of features such as averaging, smoothing, etc.. which output good data but I want a test instrument that will return an "accurate" measurement even if operator skill, attention to detail, and more time are required.

       I was curious as to which test instrument output data "closest" to the NIST specified phase angles for a given load.  

       Also, it is my belief that it may be possible that the slotted line may output some relevant physical information which may not be obvious when using a network analyzer.    This belief is only hypothetical.  Since I do not own a slotted line, I will not know the answer to this question until I purchase one.   Maybe you can give me a hint about what I am missing.   Hopefully, JWL will someday sell his system at a reasonable price and I will be lucky enough to see his ad and purchase it.     

        There are so many slotted line parts that you can buy on e-Bay but they are all worthless unless you obtain every part.   "Cobbling" together working systems can be such a waste of time and money.   I have learned from experience, believe me.

         It was nice to hear from you DHamiliton, hopefully I will hear from you again.

有趣的话题。
我很久以前就教过使用开槽线。
它们使用起来非常麻烦，并且在测量单个频率点时最准确。
尽管它们准确，但它们在准确性或可重复性方面与VNA不匹配。
使用校准套件可以纠正VNA的主要错误。
开槽线误差包括各种波导法兰和适配器的配合，探测器探头的深度设置，探测器在平方律区域的线性精度，415E SWR仪表到1kHz调制频率的调谐，
415E衰减器和仪表精度，技术人员使用调谐短截线的技巧，以及线路末端终端的质量。
它最终被替换为使用信号发生器的更实用的方法，而415E用于扫频测量。
通过使用旋转叶片衰减器进行RF替换，或使用415E和晶体检测器进行AF替换，以及使用415E和活塞衰减器进行IF替换。
每种方法都有其优点和缺点，但都更快，更便宜，更简单易用。
然后是VNA，这是一种非常昂贵的方法，但是比其他方法更准确，更快速。



     以下为原文

  Interesting topic.  I use to teach the use of slotted lines long ago.  They were very cumbersome to use and were most accurate when measuring a single frequency point.  As accurate as they were, they are no match for a VNA in terms of accuracy or repeatability.  The VNA's major errors are corrected by using a calibration kit.  The slotted line errors included the mating of the various waveguide flanges and adapters, the depth setting of the detector probe, the linearity accuracy of the detector in the square-law region, the tuning of the 415E SWR meter to the 1kHz modulation frequency, the 415E attenuator and meter accuracy, the skill of the technician to use the tuning stubs, and the quality of the termination at the end of the line itself.

It was eventually replaced for a more practical approach of using a signal generator, and 415E for swept-frequency measurements.  By using a rotary vane attenuator for RF Substitution, or a 415E and crystal detector for AF Substitution, and a 415E and Piston attenuator for IF Substitution.  Each method had its advantages and disadvantages, but all were quicker, cheaper, and simpler to use.

Then came the VNA, a very expensive approach, but one that is more accurate and quicker than all the other methods.

在我写这篇文章的时候，我没有一个开槽线。
从那以后我买了几条开槽线（总共3条）。
我真的不得不说，我喜欢开槽线。
更容易理解高频信号对带有开槽线的负载的影响。
此外，尽管VNA可能更准确（即，如果您使用的是规格中的VNA），使用VNA检测测量误差要困难得多。
我喜欢可靠的测量，并且开槽线使用户能够观察正确的相角轨迹必须位于何处。
这个功能无法超越。
现在购买开槽线的问题是你无法获得零件。
ebay上的人们正在销售那些不起作用的垃圾，而且卖家甚至不知道如何确定开槽线是否可以工作。
因此，当他们第一次购买时，新手真的被卡住了。
此外，旧的机械测试仪器可以轻松断开，没有人有资格正确修理测试仪器 - 至少，我找不到一个。
我从经验中知道这一切。
虽然我经历了2条破损的线条，但我发现它非常值得“学习”投资。
我不喜欢HP 415E系统。
我发现它是一个不可靠的系统，用现代标准判断它。
我确信它的鼎盛时期是镇上的谈话，但现在不再了。
我实际上是在EBay上买了一个，但它无法在收货时进行测量。
所以我回来了。
我查看了手册，并不关心它是如何写的。
顺便问一下，你有没有校准过HP 415E？编辑：SOLT_guy于2012年12月5日上午11:04



     以下为原文

  At the time I wrote this post I didn't own a slotted line.   

I bought a couple of slotted lines since then (3 total).   I really have to say, I like the slotted line.   It is much easier to understand the effects of high frequency signals upon a load with a slotted line.    Further, although VNA's may be more accurate (that is, if you are working with a VNA that is in spec.), it is far more difficult to detect errors in measurement with a VNA.    I like reliable measurements and the slotted line offers the user the ability to observe where the correct phase angle locus must lie.   This feature can't be beat.

The problem with buying slotted lines now is that you can't get parts.   People on ebay are selling junk that isnt' working and, further, the sellers don't even know how to determine if the slotted line can even work or not.   Therefore, noobies are really stuck when they make their first purchase.    Also, old mechanical test instruments can break easily and no one is qualified to repair the repair the test instrument properly- at least, I couldn't find one.  I know all this from experience.  

Although I went through 2 broken slottted lines, I found it was well worth the "learning" investment.   

I did not like the HP 415E system.  I found it to be an unreliable system judging it by modern standards.    I am certain in its heyday it was the talk of the town, but not anymore.    I actually bought one on EBay but it was unable to make measurements on receipt.  So I returned it.   I look through the manual and did not care for how it was written.   By the way, have you ever calibrated the HP 415E?

Edited by: SOLT_guy on Dec 5, 2012 11:04 AM