Fieldfox N9923矢量电压表B/A结果不稳定

我不确定，但更多的可能是HP8508使用锁相环实际锁定在输入信号上。
我不知道Fieldfox会进行这样的锁相，因此如果信号不在通带中，则A和B路径的微小差异会导致抖动。
10 MHz的信号源和Fieldfox是否捆绑在一起？



     以下为原文

  I don't know for sure, but more likley that the HP8508 actually locked onto the input signal using a phase lock loop.  I don't know that the Fieldfox does such a phase locking, and so slight differences in the paths to A and B can cause jitter if the signal is not precisely in the pas***and.  Are the 10 MHz of the signal source and the Fieldfox tied together?

嗨，谢谢你的回复！
是的，我确实从我的sig gen连接了10MHz。
但它仍然波动。
如果fieldfox没有锁相功能，我该怎么做才能解决这个问题呢？



     以下为原文

  Hi, thanks for reply!
yes, i did connect the 10MHz from my sig gen. but it still fluctuates. if the fieldfox does not have the phase locking function, what can i do to solve this?

请检查您的VVM是否已调整到与外部信号源调谐到的频率相同的频率。
使用“Freq”硬键并设置信号源的频率。
如果这没有帮助，您可以发布您的确切设置，以尝试在此处复制问题吗？
重要的信息将是您的连接设置，任何附加的附件，以及呈现给VVM输入的频率和功率级别。
谢谢！
PC3



     以下为原文

  Please check to see that your VVM is tuned to the same frequency your external source is tuned to. Use the "Freq" hardkey and set your source's frequency. 

If this does not help, can you post your exact setup for us to try to duplicate the issue here? The important info would be your connection setup, any attached accessories, and what frequency and power levels that are being presented to the VVM inputs. 

Thanks! 

pc3

DUT是被动还是主动？
DUT是什么类型的设备？
尝试移除DUT并将分离器臂直接连接到VVM的port1和port2，以查看它是否仍然不稳定。
如果它在没有DUT的情况下变得稳定，则DUT中可能存在问题，导致DUT中的信号丢失。
如果将源与Splitter-Input直接连接到VVM不能产生稳定的测量，请确保源的频率与调谐VVM的频率相同。
此VVM不会自动调整频率，因此您必须始终手动设置它。
如果仪器仍然不稳定，那么我担心VVM中可能存在问题。
对VVM功能的快速测试将遵循以下过程：将外部源连接到分离器。
将信号源调至1GHz（或任何属于VVM频率范围的频率.1G适合测试）确认您的信号源输出一个约0dBm的非调制CW音调进入分配器输入。
验证分离器是否正在为模型分离器生成具有正确功率下降的输出。
（检查两个端口）确保从分路器连接到VVM的任何电缆都通电（检查两根电缆是否有故障）。
使用“Freq”硬键然后使用Frequency软键将VVM设置为1GHz，然后输入您的频率。
将分离器的输出臂连接到VVM的端口1和端口2。
观察显示的信号。
如果信号仍然变化很多（几个dB，或几度），那么我怀疑VVM有问题。
我希望这有助于您获得解决方案。
请再次告知您的DUT设备类型。
如果DUT正在转换频率，或者在一只手臂上大量丢弃信号，我会特别担心。
我在没有DUT的情况下在我的工作台上重复了这个测量，并且可以确认您是否按照上面的说明操作，结果将是dB和相位的稳定值。
N9923A将显示相位偏移，屏幕上会显示一个小的dB值，可以通过将仪表归零来消除。
如果更改IFBW或频率，则必须重新归零。
在零之后，在其中一个分离器臂上插入额外长度的电缆应显示相位偏移的增加和额外的dB偏移，这是您对A / B或B / A比率的预期。
最诚挚的问候，pc3



     以下为原文

  Is the DUT passive or active? What kind of device is the DUT? 

Try removing the DUT and connecting the splitter arms directly to port1 and port2 of the VVM to see if it remains unstable. If it becomes stable without the DUT, there could be an issue in your DUT causing signal to be lost coming out of your DUT. 

If the direct connection of the Source to Splitter-Input to VVM  does not produce stable measurement, please ensure the frequency of the source is the same as the frequency you tune the VVM to. This VVM does not autotune the frequency so you must always set it manually. 

If the instrument still remains unstable, then I am worried there could be a problem in the VVM.

A quick test of the VVM functionality would be to follow this process:

Connect your external source to your splitter. 
Tune source to 1GHz (or any frequency that falls in the VVM frequency range. 1G is good for test)
Verify your source is outputting a non-modulated CW tone with about 0dBm into the splitter input.
Verify your splitter is producing output with a power drop correct for the model splitter. (check both ports)
Ensure power is getting through any cables you are connecting to the VVM from the splitter (check both cables for fault).

Set the VVM to 1GHz using "Freq" hardkey followed by the Frequency softkey, and enter your frequency.
Connect output arms of the splitter to port 1 and port2 of the VVM. 

Observe the displayed signal. If the signal is still varying by a lot (several dB, and or several degrees) then I suspect the VVM has a problem. 

I hope this helps you get a solution. Once again, please inform what your type of device is your DUT. I am especially concerned if the DUT is translating frequency, or is dropping signal by a large amount on one arm. 

I have duplicated this measurement on my bench without the DUT, and can confirm if you follow the instructions above that the results will be stable values of dB and Phase. The N9923A will display a phase offset and there will be a small dB value shown on screen, which can be removed by zeroing the meter. If you change IFBW or Frequency, you must re-zero. 
After zero, insertion of an additional length of cable on one of the splitter arms should show an increase in phase offset and an additional dB offset, which is what you expect with A/B or B/A ratios.

Best Regards,

pc3

嗨，谢谢你的回复！
我会稍后再试。
顺便说一句，我的DUT是活动的，它只是一个正常的下转换器。
从我的DUT输出的2个输出具有相同的频率和强度。
1）无论如何，当将外部源连接到分路器然后连接到VVM时，是否必须将10MHz的信号连接到VVM？
2）在测量设置>更多>输出功率下，我应该设置的标称功率是多少？



     以下为原文

  Hi, thx for the helpful reply! i will try it later.
btw, my DUT is active, it just a normal down converter. the 2 outputs coming out from my DUT are of the same frequency and strength. 
1) Anyway, when connecting the external source to splitter then to VVM, is it a must to connect the 10MHz from my sig gen into the VVM as well?
2) under meas setup > more > output power, what is the nominal power that i should set?

1）是的，你应该将所有10 MHz锁定在一起。
如果没有锁定到相同的10 MHz，则两者的频率将不完全相同。
这可能会解决您的问题。
我正在使用更新的N9918A，我猜它有更清晰的LO，但我看到输入信号为-30 dBm时抖动小于0.1度，没有锁定10 MHz。
2）我认为在VVM模式下，它会没有区别，因为源关闭了。



     以下为原文

  1) Yes, you should lock all the 10 MHz together.  The freqeuncy of the two will not be the exactly the same if they are not locked to the same 10 MHz.  This might resolve your problems.  I'm using the newer N9918A, and I would guess it has cleaner LOs, but I see less than 0.1 deg jitter with -30 dBm input signal, without locking 10 MHz.

2) I think in VVM mode, it will make no difference, as the source is turned off.

确保您的VVM频率*调整到您放入VVM端口而不是源频率*的下变频器输出频率（假设它们不同）。
此外，正如Joel所说，当您使用A / B或B / A时，在VVM上设置功率级别并不会执行任何操作，因为内部源已关闭以进行该测量。
问候，pc3



     以下为原文

  Make sure your VVM frequency *is tuned to the downconverter output frequency you are putting into the VVM ports and not the source freq* (assuming they are different). 

Also, as Joel says, setting power level on the VVM when you are using A/B or B/A doesnt do anything because the internal source is shut down for that measurement.

Regards,

pc3

大家好
我按照建议完成了所有事情，但仍然在波动。
当它连接到我的sig gen时，它的稳定性，但是一旦我连接到我的DUT，读数就会继续跳跃。
它似乎是DUT tat造成的。
但是我知道为什么当我使用8508A时，它的稳定性。
无论如何，如果这个问题持续存在，我会尝试让另一个VVM（另一个型号/品牌）尝试。
再次，thx帮助我！



     以下为原文

  Thx guys. i did everything as suggested, but its still fluctuating. when its connected to just my sig gen, its stable, but once i connect on my DUT, the reading keeps jumping. its seems like its the DUT tat is causing it. but i duno why when i use the 8508A, its stable. anyway, i will try to get another VVM(another model/brand) to try if this problem persist. once again, thx for helping me!

嗨，edmw，一些建议......不确定是否有任何帮助，但值得给它一个机会。
确保10 MHz实际上已锁定。
使用您的sig gen的10 MHz作为ref out。
转到N9923A的NA模式，确保它说Ext Ref锁定。
在VVM模式下，没有锁定/解锁指示器，但在NA模式下有。
一旦你知道你有一个很好的10 MHz锁定，然后进入VVM模式。
尝试将IFBW扩展到30 kHz。
我发现使用最宽的BW可以提供最稳定的信号。
此外，我几乎总是使用平均值（从8开始）。
你有N9923A的最新固件吗？
它是A.07.00 http://www.home.agilent.com/agilent/software.jspx?cc=US&lc=eng&ckey=2087549&nid=-33903.799348.02&id=2087549此外，这赢得了'
帮助跳跃信号，但在归零过程中确保您已将信号源设置为输出频率（如果您有下变频器则为IF）。
在测量过程中，您将其切换到RF，但对于归零部分，将其设置为IF。
如果您仍有问题，请告诉我们。
Afsi



     以下为原文

  Hi edmw, 

A few suggestions ....not sure if any will help, but worth giving it a shot.

Make sure the 10 MHz is in fact locked. Use your sig gen's 10 MHz as the ref out. Go to the NA mode of N9923A to be sure it says Ext Ref locked. In VVM mode, there is no lock/unlock indicator, but in the NA mode there is. Once you knwo you have a good 10 MHz lock, then go to VVM mode.

Try widening your IFBW to 30 kHz. I have found using the widest BW gives the most stable signal. Also, I pretty much always use averaging (start with 8). 

Do you have the latest firmware on your N9923A? it is A.07.00

http://www.home.agilent.com/agilent/software.jspx?cc=US&lc=eng&ckey=2087549&nid=-33903.799348.02&id=2087549

Also, this won't help with the jumping signal, but be sure during the zeroing process that you have set your source to the output frequency (the IF if you have an downconverter). During your measurement, you will switch it to the RF, but for the zeroing part, set it to the IF.

Let us know if you still have issues. 

Afsi

嗨，谢谢你的建议。
顺便问一下，为什么我要在测量过程中切换到RF？
我的A和B都来自我的DUT。
在NA模式下，我可以在哪里检查分机？编辑：edmw于2013年7月15日下午11:26



     以下为原文

  Hi, thx for ur suggestion. btw, why should i switch to RF during measurement? both my A and B are IF from my DUT.

In NA mode, where can i check the ext ref locked?

Edited by: edmw on Jul 15, 2013 11:26 PM

> {quote：title = edmw写道：} {quote}>嗨，你的建议。
顺便问一下，为什么我要在测量过程中切换到RF？
我的A和B都来自我的DUT。
我不是100％肯定你的DUT做了什么，但我以为你说你有一个下行转换器。
所以我假设源频率不同于输出。
但是如果输入你的DUT和A＆amp;
B频率相同，然后您永远不会更改信号源的频率设置。
>在NA模式下，我可以在哪里检查ext ref锁定？
在NA模式下，如果您将频率参考更改为外部，它只会在屏幕上显示。
步骤如下：[系统] {系统配置} {频率参考} {频率参考源} {Ext}然后，在屏幕的左下角，您将看到一个Ext R.如果它已解锁，则显示
将在下半部分显示“Ext Ref UNLOCKED”消息。
Afsi Moaveni >>编辑：edmw于2013年7月15日下午11:26



     以下为原文

  > {quote:title=edmw wrote:}{quote}
> Hi, thx for ur suggestion. btw, why should i switch to RF during measurement? both my A and B are IF from my DUT.

I am not 100% sure what your DUT does, but I thought you said you had a downconverter. So I assumed the source frequency was different than the output. But if the input to your DUT and A & B frequencies are the same, then you never change the frequency setting on your source. 
 
> In NA mode, where can i check the ext ref locked?
In NA mode, if you change the frequency reference to external, it just shows on the screen.

The steps are:
[System]
{System Configuration}
{Frequency Ref}
{Freq Ref Source}
{Ext}

Then after this, on the lower left corner of the screen, you will see an Ext R.  If  it is unlocked, the display will show a "Ext Ref UNLOCKED" message on the lower part.

Afsi Moaveni
> 
> Edited by: edmw on Jul 15, 2013 11:26 PM

呀，它的差异。
输入频率高于输出。
但我只是想知道为什么我需要在测量期间切换到RF，因为我的输出是IF。



     以下为原文

  yup, its diff. the input freq is higher than output. but i am just wondering why do i need to switch to RF during measurement since my output is IF.

如果它适用于你的情况，我将用一个例子来证明我的意思。
输入到DUT：3 GHz LO：1 GHz（如果是调音台）A和B输出频率：2 GHz Hookup分离器，但没有DUT。
将信号源频率设置为2 GHz。
零度为2 GHz，因为最终测量的A和B信号为2 GHz，您希望以2 GHz进行归一化。
归零完成。
连接DUT。
将源频率更改为3 GHz。
测量A / B.
如果您没有将源频率更改为3 GHz，那么您的下变频器将无法按照您设计的方式工作，或者如果它工作，您最终会得到1 GHz信号。
这就是改变源频率的意思。



     以下为原文

  I'll use an example to demonstrate what I meant, again, if it is applicable to your case.

Input to your DUT: 3 GHz 
LO: 1 GHz (if it's a mixer)
A and B Output frequencies: 2 GHz

Hookup splitter, but no DUT. Set frequency of source to 2 GHz. Zero with 2 GHz, since eventually A and B signal that is measured is at 2 GHz and you want to normalize with 2 GHz. Zeroing done.

Connect DUT. Change source frequency to 3 GHz. Measure A/B.    If you did not change the source frequency to 3 GHz, then your downconverter wouldn't quite work the way you designed it, or if it worked, you'd end up with a 1 GHz signal. That's all I meant by change source frequency.