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[问答] 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?
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对于群延迟测量(PNA-X N5242A),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?
tiA

以上来自于谷歌翻译


     以下为原文

  For a group delay measurement (PNA-X N5242A), what's the dIFference between turning smoothing on and setting the smoothing points to 3 and setting the group delay aperature points to 3?  TIA  
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2019-4-30 09:47:14   评论 分享淘帖 邀请回答
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脑洞大赛9 发表于 2019-4-30 13:57
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。

以下是相关的线程...混音器Cal VMC Ecal - 同步PNA和控制器使用连接到ECal端口的PNA-X端口A步进LO的FCA校准

以上来自于谷歌翻译


     以下为原文

  The following are related threads...
Mixer Cal 
VMC Ecal - syncing PNA and controller  
Using PNA-X port 2 connected to ECal port A  
FCA Calibration for stepped LO
2019-4-30 14:15:45 评论

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juujwfdf 发表于 2019-4-30 14:15
以下是相关的线程...混音器Cal VMC Ecal - 同步PNA和控制器使用连接到ECal端口的PNA-X端口A步进LO的FCA校准

以上来自于谷歌翻译

我对这些先前的线程进行了粗略的回顾,我的记忆非常慢慢:-)然而,似乎在任何时候我们都没有真正讨论过SMC + Phase与VMC的优点,部分原因是整个讨论始于2009年
当SMC + Phase刚刚离开绘图板时。
因此,如果您今天遇到VMC的系统性问题,重新访问SMC +阶段参考方法(应该在8月底之前可用)可能并不是一个坏主意。
还有一个名为Cal All的新校准向导,可以同时轻松校准多个通道。
你可能是时候打电话给当地的FE / AE并要求一些演示。

以上来自于谷歌翻译


     以下为原文

  I did a cursory review of these prior threads and my memory is well jogged :-) However, it does not appear that at any time we really discussed the merits of SMC+Phase versus VMC and that is partly because this whole discussion started in 2009, when SMC+Phase was just getting off the drawing board.  So if you are having systematic problems with VMC today, it might not be a bad idea to revisit the SMC+Phase Reference method (which should be available by the end of August).  there is also a new calibration wizard called Cal All, which should make calibrating multiple channels at the same time a breeze.  It might be time for you guys to call in the local FE/AE and ask for some demos.
2019-4-30 14:26:40 评论

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Topcbpcba 发表于 2019-4-30 14:26
我对这些先前的线程进行了粗略的回顾,我的记忆非常慢慢:-)然而,似乎在任何时候我们都没有真正讨论过SMC + Phase与VMC的优点,部分原因是整个讨论始于2009年
当SMC + Phase刚刚离开绘图板时。
因此,如果您今天遇到VMC的系统性问题,重新访问SMC +阶段参考方法(应该在8月底之前可用)可能并不是一个坏主意。

对于我们来说,等到8月进行升级几乎需要上帝的行为。
但我们可以根据需要考虑未来的升级(我必须做一个商业案例)。
我们将开始讨论w /我们的现场代表。
看起来RDE对于我的初步发现和新的平滑点是初步的乐观。
现在我们必须说服系统工程师。
乔尔博士说,我不应该看到带有不同平滑点的带内变化(最大 - 最小)的这些大波动?
他们也很困惑为什么IFBW似乎没有太大影响(我最近只尝试过1kHz和50Hz)。

以上来自于谷歌翻译


     以下为原文

  It would almost take an act of god for us to wait until Aug for an upgrade.  But we can look at it for a future upgrade IF needed (and I'd have to make a business case).  We'll start discussions about w/ our field rep.

It looks like the RDE is preliminary upbeat about my initial findings w/ the new smoothing points.  Now we have to convince the systems engineer.

So is Dr Joel saying that I shouldn't see these big swings in variation (max - min) in-band w/ the different smoothing points?

They're also confused as to why the IFBW doesn't seem to have much of an effect (I've only really tried 1kHz vs 50Hz recently).
2019-4-30 14:32:32 评论

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juujwfdf 发表于 2019-4-30 14:32
对于我们来说,等到8月进行升级几乎需要上帝的行为。
但我们可以根据需要考虑未来的升级(我必须做一个商业案例)。
我们将开始讨论w /我们的现场代表。

我认为这正是Dr_Joel所说的。
使用性能良好的混频器/转换器,可归因于测量仪器的群延迟变化大约为+/- 0.5 ns,因此任何大于此的值都是其他一些基本问题的症状,这就是你/我们应该
揣摩。
IF带宽减少或平均只能改变数据,如果变化的来源是噪声或至少是噪声(即数据从扫描变为扫描)。
但是,如果变化是由纹波引起的纹波引起的,或者存在于DUT的原始测量中,则改变IF带宽或增加平均值将不起作用。
混频器测量的问题在于有许多纹波源,无论你怎么努力,其中一些都无法校准。
在某些情况下,做一些简单的事情,比如在电缆末端添加3-6 dB焊盘(如果你在晶圆上没有太大帮助),或者在RF和IF端口上使用源衰减可以做很多事情来改善
整体测量,这就是为什么有本地支持可以提供很多帮助。
我们确实有间隙的AE,因此您可以与当地的安捷伦销售代表讨论。

以上来自于谷歌翻译


     以下为原文

  I think that is exactly what Dr_Joel is saying.  with a well behaved mixer/converter, the group delay variation that is attributable to the measurement instrument is on the order of +/- 0.5 ns, so anything bigger than that is symptomatic of some other underlying issue and that is what you/we should try to figure out.  IF Bandwidth reduction or averaging can only improve the data if the source of the variation is noise or at least noise like (i.e the data changes from sweep to sweep).  however, if the variation is due to ripple that was either introduced as part of the calibration or it exists in the raw measurement of the DUT, then changing the IF Bandwidth or increasing the averaging will have no effect.  the problem with mixer measurements is that there are many sources of ripple, some of which cannot be calibrated out, no matter how hard you try.  in some of those cases, doing simple things like adding 3-6 dB pads to the ends of the cables (not much help if you are on wafer), or using the source attenuation on the RF and IF ports can do a lot to improve the overall measurements, this is why having local support can be a lot of help.  We do have AEs that have clearance, so that may be something you could discuss with your local Agilent reps.
2019-4-30 14:42:44 评论

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Topcbpcba 发表于 2019-4-30 14:42
我认为这正是Dr_Joel所说的。
使用性能良好的混频器/转换器,可归因于测量仪器的群延迟变化大约为+/- 0.5 ns,因此任何大于此的值都是其他一些基本问题的症状,这就是你/我们应该
揣摩。

我会检查Mike Finnegan,看看你的员工是否可以有人进入我们的实验室(也许他们可以更好地向你解释发生了什么)。
你想让我试试垫吗?
输入和输出?
我需要重新调整吗?

以上来自于谷歌翻译


     以下为原文

  I'll check w/ Mike Finnegan and see if your people can someone come into our lab (and maybe they can better explain to you what's going on).

Do you want me to try the pads?  Both input and output?  Do I need to recal?
2019-4-30 14:49:14 评论

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juujwfdf 发表于 2019-4-30 14:32
对于我们来说,等到8月进行升级几乎需要上帝的行为。
但我们可以根据需要考虑未来的升级(我必须做一个商业案例)。
我们将开始讨论w /我们的现场代表。

如果变化是由于混频器LO,VNA源或VNA LO的相位噪声引起的,则IF降低通常不会减少群延迟测量的变化。
这是因为群延迟中的噪声与相位迹线中的噪声有关。
由于LO相位噪声导致信号在IF滤波器上来回“摆动”,因此相位会上下变化。
相位变化在滤波器的BW上变化大约360度。
降低IF BW可降低噪声,但也会缩小响应,因此相位斜率(360度/ BW)增加,相位噪声引起的相位偏差与较宽的IF BW相同。
这就是为什么,并且仅对于混频器测量,降低IF BW不会降低混频器的GD响应的噪声(扫描到扫描变化)。
但是,在上一篇文章中,您说测量结果的变化不会随平均值而变化(这将减少GD迹线上的迹线噪声)。
这表明校准中内置了变化。
添加垫可以减少高阶产品的变化,从而可以改善结果。
尝试测试端口电缆上的焊盘(6 dB是一个良好的开端)。
在参考混频器上通常不需要滤波器,但是更高阶的产品可以退出参考混频器并重新混合以产生带内信号。
一切都很棘手。
您需要注意的最重要的事情是校准混频器的群延迟响应。
如果它有很多变化,很可能是错误的;
并且这种变化将被添加到整体测量中。
但是,如果你关闭校准,那么你只能看到GD中的原始变化,并且你已经说过它与校正后的变化类似,所以我对其他一些没有明确定义的问题非常怀疑,例如之间缺乏隔离
参考和测试。
因此,我建议您在DUT调音台上尝试SMC +相位作为原始测量,以查看其响应。
您可以在没有相位参考校准的情况下使用SMC +相位,并且其总涟漪声小于5纳秒。

以上来自于谷歌翻译


     以下为原文

  IF BW reduction does not, in general, reduce variation in the group delay measurement if the variation is due to phase noise of the mixer LO, VNA source or VNA LO.  This is because noise in group delay is related to noise in phase traces.  As the LO phase noise cause the signal to "wiggle" back and forth across the IF filter, the phase varies up and down.  The phase change is on the order of 360 degrees change over the BW of the filter.  Lowering the IF BW reduces the noise, but also narrows the response so the phase slope (360 deg/ BW) is increased and the phase deviation due to phase noise is the same as at the wider IF BW.  That is why,and only for mixer measurements, lowering IF BW does not reduce noise (sweep to sweep variation) of the GD response of mixers.

But, in a  previous post you said the variation in measurement results doesn't change with averaging (which will reduce trace noise on the GD trace).  This indicates the variation is built into the calibration.  

Adding pads reduces varation from higher order products, and so can improve results.  Try pads on the test port cables (6 dB is a good start).

Filter is generally not needed on the reference mixer, but higher order products can exit the reference mixer and remix to generate inband signal.  All very tricky. 

The most important thing for you to look at is the group delay response of your calibration mixer.  If it has a lot of variation, it is likely in error; and this variation will be added to the overall measurement.  But, if you turn off calibration, then you see only the raw variation in GD, and you already said it is similar to corrected variation, so I am very suspicious of some other issue that is not well defined, such as lack of isolation between ref and test.  Thus, I would suggest you try SMC+phase, as a raw measurment, on your DUT mixer to see its response.  You can use SMC+phase without the phase reference calibration and its total ripply shoudl be less than 5 nsec.
2019-4-30 15:02:16 评论

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Joel / Dara博士,请看一下以下主题:https://community.keysight.com/message/56091#comment-56091
在那里,我们(在我们拔牙的地方)讨论另一个单元(具有相同类型的测试集)的不同测试。
在该测试中,我们测量相变率/稳定性。
该测试甚至没有校准GD测试中使用的相同混合器。
然而,当我们测量混合器本身的相变速率时(通过混合器仅通过UNY信号进行测试,然后将相位稳定性与相同设置进行比较而不是混合器显示混合器本身的相稳定性)
每100毫秒增加约0.2-0.3度的变化。我们认为这些信息也可能增加你的理解。我们正在与我们的当地现场代表谈论在这里获得AE(我们确实找到了一个适当的间隙和
门票 - 我们只需要获得他的节目简报批准。我们还要让他在到达这里之前先看一下整个帖子。

以上来自于谷歌翻译


     以下为原文

  Dr Joel/Dara,

Please take a look at the following thread:
https://community.keysight.com/message/56091#comment-56091
 

There, we sort of (where we pulled your teeth) discuss a different test of another unit (w/ the same type of test set).  In that test, we're measuring phase rate of change/stability.  That test does not even cal the same mixers used in the GD test.  However, when we measured the phase rate of change of just the mixers themselves (by testing w/ just a UNY sig gen through the mixer, and then comparing phase stability against the same setup WITHOUT the mixers showed that the phase stability of the mixers themselves added about 0.2-0.3 degrees of change per 100ms.

We think this info may also add to your understanding.  We're currently talking w/ our local field rep to get an AE in here (we did find one w/ the proper clearances and tickets - we just need to get his program briefing approved).  We're also going to have him take a look at this entire thread before he gets here.
2019-4-30 15:15:12 评论

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Joel博士,我的系统工程师问你如何得出5-10%的数字进行平滑?
我请他提供他的数学(我会把它放在这里,如果它没有安全性),他如何得出他低得多的百分比。

以上来自于谷歌翻译


     以下为原文

  Dr Joel,

My systems engineer is asking how you derived the 5-10% number for smoothing?  I asked him to provide his math (and I'll put it here if it's okay w/ security) on how he derived his much lower percentage.
2019-4-30 15:28:28 评论

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juujwfdf 发表于 2019-4-30 15:15
Joel / Dara博士,请看一下以下主题:https://community.keysight.com/message/56091#comment-56091
在那里,我们(在我们拔牙的地方)讨论另一个单元(具有相同类型的测试集)的不同测试。
在该测试中,我们测量相变率/稳定性。

> {quote:title = miyamky写道:} {quote}> Joel / Dara博士,>>请看看以下主题:>> PNA-X N5242A CW时间扫描点数>>那里,我们排序(
我们拔牙的地方)讨论另一个单位的不同测试(与相同类型的测试集)。
在该测试中,我们测量相变率/稳定性。
该测试甚至没有校准GD测试中使用的相同混合器。
然而,当我们测量混合器本身的相变速率时(通过混合器仅通过UNY信号进行测试,然后将相位稳定性与相同设置进行比较而不是混合器显示混合器本身的相稳定性)
每100毫秒增加约0.2-0.3度的变化。>在该线程中未明确的一件事是在CW扫描条件下进行的实际测量。您是在测量比例如“B / R1”还是在测量
像B这样的单个接收器?你说你用一个外部的UNY选项sig gen来刺激混音器;那是去混音器的RF端口还是LO端口?如果它进入RF,你是不是对sig进行采样?
使用PNA-X参考接收器,以便您可以进行比率测量而不进行比率测量,您实际上无法分辨相变的来源,源或混频器,PNA-X的内部LO或
所有的组合。另外,除非你在井里这样做
受控环境和高质量相稳定电缆,您看到的大部分或至少部分相变可归因于电缆和您在设置中可能具有的任何其他管道。
在CW测量中尤其如此,在CW测量中,您无法区分由电缆长度变化引起的恒定相位偏移与混频器相位响应的变化。

以上来自于谷歌翻译


     以下为原文

  > {quote:title=miyamky wrote:}{quote}
> Dr Joel/Dara,

> Please take a look at the following thread:

> PNA-X N5242A CW Time Sweep number of points

> There, we sort of (where we pulled your teeth) discuss a different test of another unit (w/ the same type of test set).  In that test, we're measuring phase rate of change/stability.  That test does not even cal the same mixers used in the GD test.  However, when we measured the phase rate of change of just the mixers themselves (by testing w/ just a UNY sig gen through the mixer, and then comparing phase stability against the same setup WITHOUT the mixers showed that the phase stability of the mixers themselves added about 0.2-0.3 degrees of change per 100ms.


One thing that wasn't made clear in that thread was the actual measurement being performed under the CW sweep condition.  Are you measuring a ratio like "B/R1" or are you measuring a single receiver like B?  You say you are stimulating the mixer with an external UNY option sig gen; is that going to the RF port of the mixer or the LO port?  if it is going into the RF, are you sampling the sig gen with a PNA-X reference receiver, so that you can do a ratio measurement?  without doing a ratio measurement, you really can't tell where the phase change is coming from, the source or the mixer, the PNA-X's internal LO or a combination of all.  Also, unless you are doing this in a well controlled environment and with high quality phase stable cables, most or at least part of the phase change you do see could be attributed to the cables and any additional plumbing you might have in your setup.  this is especially true in a CW measurement, where you can't distinguish a constant phase offset caused by change of length in the cables versus change of phase response of the mixer.
2019-4-30 15:34:35 评论

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Dara,下周她回来时我会得到akalei回答你的问题......但是......看起来Joel博士是个天才。
他首先问了一个完美的问题(当然,我无法回答它 - 向他展示原始痕迹)。
我终于向开发初始设置的系统人员展示了原始痕迹(并且温度过高)(询问他是如何设置的)。
我们确切地看到了为什么我们在炎热(但不是冷)时失败了。
事实证明,完整的迹线(不仅仅是我们绘制的位置与规格相比)显示迹线向左移动以进行热处理,这导致曲线的一部分真正应该是带外的(环境数据也显示出来)
它并没有完全按照我们想要的方式过滤掉,但它仍然通过了)。
我们确实有办法调整滤波器,使其更接近中心(并且跨越温度)。
他还告诉我,这个特定的单位更容易受GD变化的影响。
我们测试的先前单元在滤波器之前和之后具有匹配良好的放大器。
这个没有,因此在过滤器周围可能存在相当糟糕的VSWR。
遗憾的是,我们必须回溯我们以前的数据并告诉我们的客户这个EM单元是不合规的,但很容易修复飞行。
我将在下周发布他的技术响应,说明为什么我们的装置会采用这种方式,以及为什么我们不能使用5%GD光圈。
即使我只是一个SW人,这里的专家真的帮助我更好地理解RF行为。
对不起,这么无知。

以上来自于谷歌翻译


     以下为原文

  Dara,

I'll get akalei to answer your questions when she returns next week...

BUT...it looks like Dr. Joel is a genius.  He asked the perfect question first (of course, I'm unable to answer it - to show him the raw trace).  I finally showed the raw trace (and over temperature too) to the systems guy who developed the initial settings (asking him how he came up w/ the settings).  We looked at exactly WHY we were failing at hot (but not at cold).  It turns out that the full trace (not just where we plot versus the spec) shows that the trace is shifted to the left for hot which brought in the part of the curve that really should be out-of-band (ambient data also shows it's not quite filtering out exactly the way we want it to but it still passed).  We do have a way to tune the filter to shift it closer to the center (and across temperature).

He also told me that this particular unit is much more susceptible to GD variation.  The previous units we were testing had well-matched amplifiers before and after the filter.  This one doesn't and so there's likely a pretty bad VSWR right around the filter.

We unfortunately have to back track our previous data and tell our customer that this EM unit was non-compliant but it's easy to fix for flight.

I'll post his technical response next week as to why our unit behaves this way and why we can't use the 5% GD aperture.

Even though I'm ONLY a SW guy, the experts here really help me get a better understanding of RF behaviors.  Sorry to be so ignorant.
2019-4-30 15:51:11 评论

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juujwfdf 发表于 2019-4-30 15:51
Dara,下周她回来时我会得到akalei回答你的问题......但是......看起来Joel博士是个天才。
他首先问了一个完美的问题(当然,我无法回答它 - 向他展示原始痕迹)。
我终于向开发初始设置的系统人员展示了原始痕迹(并且温度过高)(询问他是如何设置的)。

我要再等一个月;
但是我想daras已经听了差不多一年了:我在新的(即将出版的)书中解释了所有这些:http://www.wiley.com/WileyCDA/WileyTitle/productCd-1119979552.html以下是关于群组的摘录
延迟:

以上来自于谷歌翻译


     以下为原文

  I was going to wait another month; but I guess daras been hearing this for almost a year:  I explain all of that in my new (upcoming) book: http://www.wiley.com/WileyCDA/WileyTitle/productCd-1119979552.html

Here is an excerpt on group delay:

附件

2019-4-30 15:56:19 评论

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juujwfdf 发表于 2019-4-30 15:51
Dara,下周她回来时我会得到akalei回答你的问题......但是......看起来Joel博士是个天才。
他首先问了一个完美的问题(当然,我无法回答它 - 向他展示原始痕迹)。
我终于向开发初始设置的系统人员展示了原始痕迹(并且温度过高)(询问他是如何设置的)。

> {quote:title = miyamky写道:} {quote} >>但是......看起来Joel博士是个天才。
......我们正好看看为什么我们在炎热的时候失败了(但不是很冷)。
事实证明,完整的迹线(不仅仅是我们绘制的位置与规格相比)显示迹线向左移动以进行热处理,这导致曲线的一部分真正应该是带外的(环境数据也显示出来)
它并没有完全按照我们想要的方式过滤掉,但它仍然通过了)。
我们确实有办法调整滤波器,使其更接近中心(并且跨越温度)。
>>>我将在下周发布他的技术回应,说明为什么我们的装置会采用这种方式,以及为什么我们不能使用5%GD光圈。
>因此,当然您不能使用无法正确测量实际延迟响应的平滑。
这里的一个重要线索是平均值对延迟波动没有影响。
平滑用于消除痕量噪声效应;
但是如果迹线没有噪声(也就是说,没有从一个采集到另一个采样的变化...... +旁边:(在这种情况下采用平均值的方法意味着,例如,获得100次平均扫描,将其放入存储器,
重置平均并获得另外100个平均扫描)+)然后不应使用平滑。
以前的帖子详细说明平滑影响附件。
在这种情况下,您的波纹正在准确测量您要测量的内容:转换器的响应,并确保它不会在工作温度下发生变化。
我完全理解你所说的设计差异:我们一直看到这些转换器。
有时一个滤波器对混频器单侧的影响不能计算出它对混频器另一侧滤波器的影响...当然这在第6章中都有所涉及...... :-)

以上来自于谷歌翻译


     以下为原文

  > {quote:title=miyamky wrote:}{quote}

> BUT...it looks like Dr. Joel is a genius. ...We looked at exactly WHY we were failing at hot (but not at cold).  It turns out that the full trace (not just where we plot versus the spec) shows that the trace is shifted to the left for hot which brought in the part of the curve that really should be out-of-band (ambient data also shows it's not quite filtering out exactly the way we want it to but it still passed).  We do have a way to tune the filter to shift it closer to the center (and across temperature).
> > 
> I'll post his technical response next week as to why our unit behaves this way and why we can't use the 5% GD aperture.

So, of course you cannot use smoothing that will not allow proper measurement of actual delay response.  The big clue here was that averaging had no effect on the delay ripple.  Smoothing is used to remove trace-noise effects; but if the trace is not noisy (that is, does not have variation from one acquisiton to another...+aside: (acquistion in this case where averaging is used means for example, acquire an 100 average sweep, put it to memory, reset averaging and acquire another 100 avg sweep)+ ) then smoothing should NOT be used.  Previous post details smoothing affects in the attachement.

In this case, you ripple was measuring exactly what you were trying to measure: the response of the converter, and ensuring that it does not change over the operating temperature.   And I understand completely the design differences of which you speak: we see that all the time in these converters.  Sometimes the influence of one filter on one-side of a mixer doesn't get computed for its effect on another filter on the other side of the mixer...of course that is all covered in Chapter 6... :-)
2019-4-30 16:02:13 评论

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脑洞大赛9 发表于 2019-4-30 13:57
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。

> {quote:title = Dr_joel写道:} {quote}>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。
>>可以从以下问题分析VMC的一些常见问题:>> 1)您对参考混频器使用了什么?
它是在IF过滤的吗?
> 2)您使用什么将LO信号发送到参考混频器?
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 nsec的延迟误差很大,以归因于仪器误差。
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电子邮件,其中包含您的详细信息,我们可以离线进一步讨论。
1)参考混频器(Marki Microwave M2-0026LB)在IF 2)E8257D(w / UNY选项)进行滤波.3)与参考混频器相同的混频器类型。
--- EDIT akalei表示参考混频器未经过滤,但其他校准混频器已经过滤。
试着保持这个,因为有其他人在看我们(有耐力的安静)编辑:miyamky于2012年7月18日下午5:02编辑:miyamky于2012年7月18日下午5:04

以上来自于谷歌翻译


     以下为原文

  > {quote:title=Dr_joel wrote:}{quote}
> 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.

1) The reference mixer (Marki Microwave M2-0026LB) IS filtered at the IF
2) E8257D (w/ UNY option)
3) Same type as mixer as the reference mixer. --- EDIT akalei says the reference mixer is NOT filtered but the other calibration mixer IS filtered.

Trying to keep this here since there are others watching us (be vewy vewy quiet)

Edited by: miyamky on Jul 18, 2012 5:02 PM

Edited by: miyamky on Jul 18, 2012 5:04 PM
2019-4-30 16:15:04 评论

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