平滑开启和将平滑点设置为3并将群延迟温度点设置为3之间的区别是什么？

他们是一样的东西！！
在过去，平滑机制是实际更改默认组延迟光圈（2点）的唯一方法。
然而，当使用时，状态将指示平滑已打开并且与我们的一些更具计量意识的用户不相符（因此它默认情况下从未打开，导致默认组延迟测量比
他们必须是）。
现在我们将所有测量中可用的平滑功能与群延迟孔径设置分开，该设置仅适用于群延迟测量。
我们还将默认光圈设置为11点，这样可以在默认条件下为您提供合理的测量。



     以下为原文

  they are the same thing!!  In the past the Smoothing mechanism was the only way to actually change the default group delay aperture (2 points).  However, when used, the status would indicate that smoothing was turned on and that did not sit well with some of our more metrology minded users (so it was never turned on by default and that resulted in default group delay measurements being way more noisy than they had to be).  Now we have separated the Smoothing function, which is available on all measurements, from the group delay aperture setting, which is only applied to group delay measurements.  We have also set the default aperture to 11 points, which should give you a reasonable looking measurement under the default conditions.

感谢Dara ...现在要拉更多Joel博士的牙齿（记住，我不是射击乐的人，我是一个SW家伙）...我注意到了点数，这个群体延迟了aperature（
或平滑）点对我的测量影响最大。
对于我的一个测试，我有一个5MHz带宽的DUT，但我们测量的是8MHz。
我得到以下结果（近似值）：BTW，平均似乎没有任何影响（至少在我的DUT的带宽上 - 它只是带外的）但我现在平均5次。
此外，IFBW似乎也没有产生很大的影响，但是现在我有一个1000 Hz的IF带宽（但我已经玩了50赫兹，这是我工程师最初想要的）。
由于我没有看到带宽方差的巨大差异，因此它以更快的速度传播。
PTS Aperature Variance（超过80％的DUT带宽）161 3 100 401 3 135 161 5 40 161 4 80我不知道真正的测量是什么。
我想我需要根据带宽“计算”我的＃点数。
我应该使用某种神奇的配方吗？
FWIW，我们最初的Rohde＆amp;
Schwarz ZVRE测量结果我们以1601点的价格出售，温度百分比为.1875（达到3点），平均值为25，IFBW为1kHz。
这是我尝试使用PNA-X重新创建的数据。
对于该测量，方差约为60ns。编辑：miyamky于2012年7月17日下午5:06



     以下为原文

  Thanks Dara...now to pull more of Dr. Joel's teeth (remember, I'm NOT an RF guy, I'm a SW guy)...

I'm noticing that the # of points, the group delay aperature (or smoothing) points have the greatest affect on my measurements.

For one of my tests, I have a DUT w/ a 5MHz bandwidth but we're measuring across 8MHz.

I get the following results (approximates): BTW, averaging doesn't seem to have any effect (at least across my DUT's bandwidth - it only matters out-of-band) but I am averaging 5 times right now.  Also, the IFBW doesn't seem to have a great impact either but right now I have a 1000 Hz IF bandwidth (but I have played w/ 50 Hz which is what my engineer originally wanted).  Since I didn't see a big difference in the variance over the bandwidth I went w/ 1kHz since it goes WAY faster that way.

PTS   Aperature  Variance (over 80% of DUT bandwidth)
161    3              100
401    3              135
161    5              40
161    4              80

I have no idea what's the real measurement. I think I need to "calculate" my # of points along w/ the aperature based on bandwidth. Is there some sort of magical formula I should be using?

FWIW, our original Rohde & Schwarz ZVRE measurement that we sold off on used 1601 pts, aperature percentage of .1875 (which comes out to 3 pts), 25 averages and an IFBW of 1kHz.  This is the data that I'm trying to recreate using the PNA-X.  For that measurement, the variance was about 60ns.

Edited by: miyamky on Jul 17, 2012 5:06 PM

最好知道DUT是混频器，还是放大器或滤波器。
如果您可以发布保存状态（保持扫描），这将提供最佳信息。
是变化类噪声（改变扫描到扫描）还是稳定（系统，如在校准相关）。
试试这个：获取数据 - > mem和data / mem，查看结果。
噪音（变化）大致相同吗？
如果是这样，则是由于跟踪相位响应的噪声。
有时这可以通过更宽的IF BW和更多的平均值来改善。
此外，仅在一些R＆amp; S盒子上，还有一个延迟孔径设置为默认值11 pts，与平滑功能无关。
通过这种方式，即使平滑也总是平滑群延迟。
不确定这是否在ZVR上，但肯定在后期产品上。
与低平滑设置相比，这给人的印象是延迟比预期的更平滑。



     以下为原文

  It would be best to know if the DUT is a mixer, or amplifier or filter.

If you could post a saved state (with the sweep on hold) that would give the best information.

Is the variation noise-like (changes sweep to sweep) or stable (systematic, as in calibration related).

Try this:  Take the data->mem and data/mem, look at the results.  Is the noise (variation) about the same?  If so it is due to trace noise on the phase response.

Sometimes this can be improved by wider IF BW and more averaging.

Also, FYI, at leas on some of the R&S boxes there was also a delay aperture set to by default 11 pts, independent of the smoothing function.  In this way, the group delay was always smoothed even with smoothing off.  Not sure if this was on the ZVR but definitely on later products.  This gives the impression of smoother delay than expected with low smoothing settings.

搅拌机（使用VMC）。
变化非常稳定。
平均几乎没有带内效应。
我运行了一次平均5次（所有w /相同的结果）并将其与5个平均值的样本进行比较，结果几乎相同。
我有另外两个人用垫子检查我的校准（显示垫子的GD的两倍）和一个50欧姆的终止，我们看到-45dBm GD。
所以，在我看来，cal是好的。
你是说没有用于确定正确设置的公式（或者你只是需要这个附加信息）根据DUT和测量的带宽说？
甚至我的工程师现在也有点困惑。
我们意识到平滑会极大地影响变化，但是工程师使用超过3点非常犹豫（这就是他经常使用的以及他的舒适度）。
我想你错过了我之前说过的一些内容（R＆amp; S设置为3分平滑）。
编辑：miyamky于2012年7月18日上午6:58



     以下为原文

  Mixer (VMC used).  The variation is VERY stable.  Averaging has almost NO effect in-band.  I ran a single average 5 times (all w/ the same results) and compared it against a sample w/ 5 averages and the results were virtually identical.

I've had two others check my cal once w/ a pad (to show double the GD of the pad) and once w/ a 50ohm termination where we see a -45dBm GD.  So, it seems to me that the cal is good.

Are you saying that there's no formula for determining the proper settings (or you just needed this additional info) say based on the bandwidth of the DUT and measurement?  Even my engineer is a little confused now.  We realize that the smoothing greatly affects the variation but the engineer is very hesitant to use more than 3 points (that's what he's always used and what he's comfortable w/).

I think you missed some of what I stated earlier (the R&S was set to 3 pts smoothing).

Edited by: miyamky on Jul 18, 2012 6:58 AM

我在另一个帖子中看到你提到IFBW应该是测量带宽的10％。
那么对于我的8MHz测量（5MHz DUT），我应该使用8kHz IFBW吗？
这个带宽适合多少个点？



     以下为原文

  I saw in another thread you mentioned that the IFBW should be 10% of the measured bandwidth.  So for my 8MHz measurement (of a 5MHz DUT), I should use a 8kHz IFBW?  How many points is proper for this bandwidth?

你说“如果是这样，那就是由于跟踪相位响应的噪声。”
你能解释一下吗？
记住我是一个SW的家伙。



     以下为原文

  You said "If so it is due to trace noise on the phase response." Can you explain this to me?  Remember I'm a SW guy.

如果群延迟的变化是稳定的，并且它是混频器测量，那么几乎可以肯定是由于校准问题，很可能是由于校准混频器的特征。
对于窄带测量，我们的接收器的GD误差非常小，如果不仔细校准，校准误差可能大于接收器中的误差。
对于测试，取消选择校准校准集（校准：管理：校准集，然后突出显示通道的校准集，点击取消选择然后关闭（不正常，重新选择它））GD平面度如何？
我认为它可能是一个混音器：它们使GD测量值大大复杂化。
GD是相变的量度;
群延迟= - （相位变化）/（360 *频率变化）;
设置平滑时，您实际要做的是设置选择增量相位和增量频率的跨度;
平滑3个点意味着相位超过3个点（频率的两个步骤）。
顺便说一句：是的，我读到你说平滑是3分，但R＆amp; S有一个额外的类似平滑的功能，称为GD光圈，它可以额外应用11点平滑。
但是，我不认为这是问题所在，因为你说在变化中跟踪不是类似噪声的。
GD轨迹的变化是稳定的，扫描到扫描几乎总是由于以下原因：1）校准错误;
2）DUT的真实变化。
最有可能的是，校准混合器的特性应该归咎于此。
它应该被描述为一个单独的步骤（不要将特征描述作为VMC cal的一部分，而是使用“特征化Cal Mixer”向导来表征它，并调用该文件）。
在进行表征时，不要将任何电缆从PNA端口连接到mxier，而只使用硬线连接（例如和适配器）。
表征结果对表征期间测试端口电缆的变化非常敏感。
如果将特征保存到S2P文件，则可以将其调用到PNA通道并查看混频器的GD变化。
对于GD测量，SMOOTHING和/或GD APERTURE的组合应该是BW的5-10％。
这与IF BW无关，它与平均因子相结合，设置跟踪噪声或跟踪到跟踪变化。
您可以考虑联系您当地的应用工程师，帮助您完成设置。



     以下为原文

  If the variation in group delay is stable, and it is a mixer measurement, then it is almost certainly due to a calibration issue, most likely due to the characterization of the calibration mixer. 

For narrow-band measurements, the GD error of our receivers is quite small, and the error in calibration can be greater than the error in our receivers, if the calibration is not done carefully.  

For a test, unselect the calibration calset (Cal:Manage:Calsets then highlight the calset for the channel, hit Unselect and then CLOSE (not OK, which reselects it))

How does the GD flatness look?

I figured it might be a mixer: they complicate GD measurements considerably.

GD is a measure of PHASE VARIATION;  group delay = -(change in phase)/(360*Change in frequency);  when you set the smoothing, what you are really doing is setting the span over which delta phase and delta-frequency are chosen;  Smoothing of 3 points means the phase is taken over 3 points (two steps of frequency).

BTW: yes, I read that you said smoothing was 3 points, but R&S had an additional smoothing-like function, called GD aperture, that applies an additional 11 points smoothing.  But, I don't think this is the issue, since you say the trace is not noise-like in the variation.   Variation in the GD trace that is stable, sweep-to-sweep is almost always due to either:  1)  Calibration error; 2) real variation in the DUT.

Most likely, the characterization of the calibration mixer is to blame.  It should be characterized as a separate step (don't use characterization as part of the VMC cal, instead characterize it using the "characterize Cal Mixer" wizard, and recall the file).  When doing the characterization, don't put ANY cable from the PNA port to the mxier, but only use a hard-lline connectin (such as and adapter).  The characterization results are very sensistive to variation in the test port cable during characterization.

If you save the characterization to an S2P file, then you can recall it to a PNA channel and look at the GD variation of the mixer.

For GD measurements, the combination of SMOOTHING and/or GD APERTURE shoudl be on the order of 5-10% of the BW.  this is NOT releated to IF BW, which in combination with the averaging factor, sets the trace-noise, or trace to trace variation.

YOu might consider contacting your local application engineer to come out and help with the setup.

联系当地应用工程师对我们没有帮助，因为它们不允许进入实验室。
我们不能再讨论他们的细节而不是你和他们最终问你们（所以我试图摆脱中间人）。
我会和工程师谈谈增加平滑度（实际上我正在使用GD光圈并关闭平滑）但是上次我要求增加它，他不喜欢这个想法。
你说平滑和GD光圈的“组合”。
我以为达拉说他们是一样的。
所以我不确定你对5-10％带宽的意思。
所以w / 161分，每个点覆盖50kHz，然后我应该使用8-16个平滑点（假设我的数学是正确的）应该是9-17，因为通常使用奇数？
顺便说一句，如果我一直不清楚，当我说“变化”时，我的意思是指最大 - 最小GD超过单位带宽的80％。
对于R＆amp; S，我们没有明确设置GD光圈，因此如果设置不相互影响，它可能是默认的。
我没有R＆amp; S了，但我可以查看旧的代码和参数值。
我会在一段时间内回复您想要的校准答案。



     以下为原文

  Contacting the local application engineers is not helpful for us since they aren't allowed in the lab.  We can no more discuss w/ them details than w/ you and they end up asking you guys anyway (so I'm trying to get rid of the middle man).

I'll talk to the engineer about increasing the smoothing (actually I'm using the GD aperture and turn OFF smoothing) but last time I asked to increase that, he didn't like the idea.  You said the "combination" of smoothing and GD aperture.  I thought Dara said they were the same.  So I'm unsure exactly what you mean for 5-10% of the bandwidth. So w/ 161 pts, each point covers 50kHz, and then I should use 8-16 smoothing pts (provided my math is correct) which should be 9-17 since odd numbers are usually used? 

BTW, if I've been unclear, when I say "variation" I mean that to mean the max - min GD over 80% of the unit's bandwidth.

For the R&S, we didn't explicitly set the GD aperture so it probably was defaulted if the settings don't affect each other.  I don't have a R&S handy anymore but I can look at the old code and parameter values.

I'll return w/ the answers you wanted on the calibration in a little while.

我的意思是说它们是相同的，如果你打开例如5点平滑或你在同一数据上打开5点GD光圈，你会得到相同的答案。
但是，既然两个功能是分开的，您可以使用平滑和GD光圈的组合。
通过这种方式而不是具有大的平滑值（大多数工程师不喜欢），您可以将GD光圈和小平滑因子结合起来，这样可以获得与大平滑因子相同的效果，同时减少不良的余味
:-)



     以下为原文

  what I meant by saying that they are the same is that if you turn on for example 5 point smoothing OR you turn on 5 point GD aperture on the same data, you get the same answer.  however, now that the two functions are separated, you can use a combination of smoothing and GD aperture.  that way instead of having a big smoothing value (which most engineers don't like), you can have a combination of GD aperture and a small smoothing factor, which will give you same effect of a large smoothing factor with less of the undesirable aftertaste :-)

所以对于Joel博士关于cal的问题（我认为他现在真的很讨厌我）......我们没有calsets。
我们保存.csa文件并调用它们。
无论如何，所以我尝试将CORRECTION关闭/打开，并且变化中的差异“看起来”可以忽略不计（我必须绘制它们以便查看，如果需要，我当然可以编码这两种情况）。
幅度变化大约90 ns，但迹线看起来相同（至少对于我和akalei的眼睛）w /自动缩放。
如果你想让我尝试任何事情，我会做的。
在这一点上，系统工程师并不喜欢我，因为我告诉他们“看起来”就像他们已经售完的数据（他们花了2-3个月来设置）可能不准确。
他现在要求我在所有情况下获得10倍样本（这需要很多小时/低IFBW）一旦我出现了新的设置，请加上任何理由我为什么会出现这些变化。
所以没有人喜欢我... :(



     以下为原文

  So for Dr. Joel's question on the cal (and I think he's REALLY hating me now)...

We don't have calsets.  We save .csa files and recall them.  Anyway, so I tried just turning CORRECTION OFF/ON and the difference in the variation "looks" neglible (I'd have to plot them to see and if you need that I can certainly code up both cases).  The amplitude changes by about 90 ns but the trace looks identical (at least to my and akalei's eyes) w/ auto-scale on.  If you want me to try ANYTHING, I'll do it.

At this point the systems engineer is NOT liking me either since I told them it "appears" like their already sold off data (that they took 2-3 months to come up w/ the settings) may not be accurate.  He's now asking me for a 10x sample across ALL cases (which takes many hrs w/ the low IFBW) once I've come up w/ new settings PLUS any reasons why I'm coming up w/ the changes.

So NO ONE likes me now... :(

> {quote：title = miyamky写道：} {quote}>我们没有calsets。
我们保存.csa文件并调用它们。
当你有.csa文件（csa = Cal State Archive）时，你有calsets。
如果您不相信我，请转到您的PNA并使用校准管理器，删除您在那里看到的所有校准集。
现在，如果您依赖.csa文件来处理所有事情，这应该不是问题，因为一旦您回想起相应的.csa文件，您将需要恢复任何内容。
删除所有校准集后，调用一个具有校正状态的.csa文件。
现在，如果再次启动校准管理器，您将看到状态中已打开校正的每个通道都有一个校准集。
当然，你可以接受我的话，而不是冒险从你的calset目录中丢失一些有价值的东西:-)



     以下为原文

  > {quote:title=miyamky wrote:}{quote}
> We don't have calsets.  We save .csa files and recall them. 

when you have .csa files (csa = Cal State Archive) you do have calsets.  if you don't believe me, go to your PNA and using the cal manager, delete all the calsets that you see there.  Now if you rely on .csa files for everything, this shouldn't be a problem, because anything you need will be restored once you recall the appropriate .csa file.  after you have deleted all the calsets, recall one of your .csa files that has a correction state.  now if you bring up the cal manager again, you will see that there is a calset for every channel in the state that has corrections turned on.  Of course,  you can just take my word for it and not risk loosing something valuable from your calset directory :-)

我怎能不相信所有强大的强大Dara S（至少那是akalei和我打电话给你）？
所以CH2_CALREG指示VMC（我们正在使用通道2）所以我“取消选择”它，并且X窗口和差异是相同的，就像我关闭校正（约90ns）。
我们错误地认为当前的校准集会突出显示（并且没有）。



     以下为原文

  How can I not trust the all and mighty powerful Dara S (at least that's what akalei and I call you)?  So CH2_CALREG indicated VMC (and we're using channel 2) so I "unselected" it, and X'd the window and the difference is the same as if I turned correction OFF (about 90ns).  We had incorrectly assumed the currect calset would be highlighted (and none were).

> {quote：title = miyamky写道：} {quote}>我们错误地认为当前的calset会突出显示（并且没有）。
不，您只看到卡座前面的通道编号，因为校准管理器向您显示仪器中所有校准的状态，但所有操作（除了删除和视图属性）都与通道相关联
当你抚养校准经理时，这是活跃的。
用户校准集可用于校正多个通道，因此您可能会在一个用户校准集前面看到多个通道编号的列表。
另一方面，通道校准寄存器只能在它们自己的特定通道中打开，因此，如果你有类似CH2_CALREG的东西，如果该通道打开校正，你只能在通道列表中看到“2”。



     以下为原文

  > {quote:title=miyamky wrote:}{quote}
> We had incorrectly assumed the currect calset would be highlighted (and none were).

no you just see the channel number(s) in front of the calset, because the cal manager is showing you the state of all the calibrations in the instrument, but all the actions (other than delete and view properties) are associated with the channel that was active when you brought up the cal manager.  A user calset can be used to correct multiple channels, so you might see a list of multiple channel numbers in front of one user calset.  Channel Cal Registers on the other hand can only be turned on in their own specific channel and therefore, if you have something like CH2_CALREG, you would only see "2" in the channel list if that channel has correction turned on.

如果关闭校准不会对形状造成太大影响（忽略偏移），则可能是由DUT的响应设置形状。
它们在VMC测量中的典型误差非常小心，为0.2-0.5 nsecs。
没有校准，可能是0.5-2纳秒。
如果您的变化更大，则来自DUT，参考混频器或其他东西。
测试设备是否有自己的LO，或者您使用PNA端口作为LO？
如果它有自己的LO，它是否与10 MHz参考相关联。
并且（我应该首先考虑这个问题）LO是固定的，你是否正在扫描RF和IF频率;
还是LO扫过。
你试过SMC + Phase方法吗？
它可以使用与VMC校准混频器相同的混频器，以及更简单的延迟测量设置。
无论如何，在3周左右的时间内，我们推出了一种新的校准方法，不需要任何参考或校准混频器，典型性能约为+ -100psec精度（高达27 GHz）。
非常简单，非常直接。
您可以考虑切换到它。
此外，如果您的LO频率超过1 LO，则新方法一次校准它们，因此可以更快。



     以下为原文

  If turning off calibration doesn't affect the shape much (ignoring offsets) then it is likely that the shape is set by the response of the DUT.

They typical error in VMC measurements with good care is one the order of 0.2-0.5 nsecs.  Without calibrations, maybe 0.5-2 nsec. If your variation is a lot bigger, it is from either the DUT, the reference mixer or something else.

Does the test device have its own LO or are you using the PNA port as the LO? If it has its own LO, is it tied to the 10 MHz reference.

And (and I should have thought to ask this first) is the LO fixed, and are you sweeping the RF and IF frequencies; or is the LO swept.

Have you tried the SMC+Phase method?  It can use the same mixer as the calibration mixer for VMC and a much simpler setup for delay measurements.
In any event, in 3 weeks or so we are introducing a new calibration method that does not require any reference or calibration mixer, with typical performance of about +-100psec accuracy (up to 27 GHz).  Very simple and very straighforward.  You might consider switching to it. 

Also, if you more than 1 LO frequency, the new method calibrations them all at one time, so it can be much faster.

我们的DUT使用外部UNY选项信号发生器（8663B）作为其LO。
所有测量设备都连接到单个10MHz参考。
LO处于固定频率。
关于这个方法，Dara和我们（大多数是我们的测试工程师）一起工作了另外一个线程，大约2个月来开发cal。
我们确实讨论了SMC + Phase方法，但我相信Dara告诉我们使用VMC方法（让我看看我是否可以找到该线程）。
系统工程师，测试装置硬件工程师和所有单位设计工程师同意最终的IFBW，平均，平滑，pts设置（再次超过2-3个月）。
所有这一切出现的原因是我发现我们的SW存在缺陷（不等待所有平均值在读取跟踪之前完成），这是您最近帮助我们修复的，然后我在新设备上重新运行SW
（先前已经用R＆amp; S进行了测试）并且通过R＆amp; S上的变化的DUT现在在高温下失效（现在显着地下降）。
它几乎不在环境温度下通过（R＆amp; S测量具有约20ns的余量）。



     以下为原文

  Our DUT uses an external UNY option signal generator (8663B) for its LO.  All measurement devices are tied to a single 10MHz reference.  The LO is at a fixed frequency.

As to the method, there's another thread someone in here that Dara worked w/ us (mostly our test set engineer) for about 2 months to develop the cal.  We did discuss the SMC+Phase method but I believe Dara told us to use the VMC method (let me see if I can find that thread). The final IFBW,averaging,smoothing,# of pts settings (again over that 2-3 month) period was agreed upon by the systems engineer, test set HW engineer and all the unit design engineers.

The reason that all of this came up was that I found that our SW was flawed (not waiting for all of the averages to complete before reading the trace) which you recently help us fix and then I re-ran the SW on a new device (that was previously tested w/ a R&S) and the DUT which passed the variation on the R&S is now failing at hot temperature (and now by a significant margin).  It barely passes at ambient temperature (the R&S measurement had about 20ns of margin).

在再次与akalei交谈后，我们“认为”这是我们开发VMC时的开始：http：//na.tm.agilent.com/pna/help/latest/Programming/GPIB_Example_Programs/Create_and_Cal_a_VMC_Measurement.htm之后
你会发现我们在实施它时遇到一些问题的几个主题，Joel博士，Dara和Danzy先生在2010年左右帮助了我们。



     以下为原文

  After talking w/ akalei again, we "think" this is what we started w/ in developing our VMC:

http://na.tm.agilent.com/pna/help/latest/Programming/GPIB_Example_Programs/Create_and_Cal_a_VMC_Measurement.htm

After that you'll find a few threads where we had some problems implementing it and Dr Joel, Dara and Mr Danzy all helped us in about 2010.

其中一位DUT设计工程师表示，他同意使用5％的BW平滑设置，但他希望详细查看数据。



     以下为原文

  One of the DUT design engineers said that he'd agree to using a 5% of BW smoothing setting but he wants to look at the data in detail.

如果你能指出前面的线程（考虑到我工作的不同客户和测量设置的数量，我的记忆有点模糊），那将是很好的。
我问的原因是，鉴于我们在SMC +阶段取得了成功（特别是我们即将发布的新阶段参考方法），在极少数情况下，我会推荐VMC而不是SMC + Phase，如果是
客户最终想要的是群延迟而非绝对阶段响应。
因此，链接到我们之前的讨论将告知我们导致当前测量方法的设置细节，并可能有助于解决当前问题。
作为参考，以下是一组测量的屏幕截图，其中我比较了PNA上可用的所有不同混频器/转换器组延迟测量技术：https：//dl.dropbox.com/u/87949221/
MixerDelayComparison.jpg！编辑：daras于2012年7月18日下午3:29



     以下为原文

  It would be nice if you could point out that previous thread (given the number of different customers and measurement setups I work on, my memory is a bit foggy).  the reason I ask is that given the success we have been having with SMC + Phase (and specially our new soon to be released Phase Reference Method), there are very few circumstances, where I would recommend VMC over SMC+Phase, if what the customer ultimately wants is Group Delay and not absolute phase response.  So having a link to our previous discussion will inform us of the setup details that led to the current measurement approach and might be helpful in troubleshooting the current issues.

Just as a point of reference, here is a screen shot of a set of measurements where I compared all the different Mixer/Converter Group Delay measurement techniques available on the PNA:

!https://dl.dropbox.com/u/87949221/MixerDelayComparison.jpg!

Edited by: daras on Jul 18, 2012 3:29 PM

从Daras测量结果可以看出，VMC只有大约0.5 ns的延迟纹波。
所以，除非测试设置有一些非常奇怪的缺陷，否则我无法理解你如何得到20纳秒的纹波。
SMC + Phase应该可以很好地为您设置。
我们看到的主要问题是窄带上的迹线到迹线噪声，并且您声明您没有看到任何迹线到迹线的噪声。
VMC的一些常见问题可以通过以下问题进行分析：1）您对参考混频器使用了什么？
它是在IF过滤的吗？
2）你用什么来发送LO信号到参考混频器？
它是在参考和测试之间隔离的（有时，来自参考混频器的IF滤波和eakage信号从反射混频器的LO端口浮出，穿过分路器并进入测试混频器的LO端口，在DUT输出处显示为IF）
。
- 注意：SMC + Phase消除了这个问题3）您使用什么校准混合器？
它是在IF过滤的吗？
如果在校准后重新测量，它的延迟是什么样的？
它与混频器特性文件相比如何？
20或甚至2纳秒的延迟误差很大，以归因于仪表误差。
它必须是设置和校准问题;
那个或DUT有响应。
您可以向我发送一封包含您详细信息的电子邮件，我们可以离线进一步讨论。



     以下为原文

  From Daras measurements you can see we have only about 0.5 nsec delay ripple with VMC.  So, I cannot understand how you get 20 nsec of ripple unless the test setup has some very odd flaw.    SMC+Phase should work very well for you setup.  The main issue we see is trace-to-trace noise on narrow bands, and you state that you don't see any trace-to-trace noise.  

Some common problems with VMC can be analyzed from the following questions:

1) what are you using for a reference mixer?  Is it filtered at the IF?
2) what are you using to send LO signal to the reference mixer?  Is it isolated between reference and test (sometimes, IF limage and eakage signals from the reference mixer floats out the LO port of the ref mixer, across the splitter and into the LO port of the test mixer to appear as IF at the DUT output).  --note: SMC+Phase eliminates this issue
3) What are you using for a calibration mixer?  Is it filtered at the IF?  What does it's delay look like if you remeasure after calibration? How does it compare to the mixer characterization file.

20 or even 2 nsec of delay error are much to large to attribute to instrumentation error.  It must be setup and calibration issues; that or the DUT has the response.

You might send me an email with your details and we can take further discussion off-line.