PNA N5221A不平衡的源错误消息

> {quote：title = spstefanop写道：} {quote}>我使用的是PNA N5221A。
我正在尝试测量具有有源匹配网络的天线的S11和S21，该网络需要直流电源（5V，20mA）。
在端口2，我使用另一个天线。
由于有源匹配网络的晶体管引入的非线性，我需要低功率电平来验证小信号s参数模拟。
因此，当我尝试将功率级别设置为小于-16 dbm的值时，我收到此错误消息：'Unleveled source 1，out 1'。
我使用从100 MHz到1 GHz的双端口标准SOLT校准。
什么可能导致这样的错误？
如果忽略错误消息，精度会受到怎样的影响？
嗨，我从未使用过N5221A - 它远远超出我的预算！
我也不为Keysight工作。
但也许以下内容会有所帮助。
1）您应说明您的仪器有哪些选项，以及固件版本。
如果您有可配置的测试装置（可能是任何选项），它可能允许您在适当的位置插入一些衰减器，以使您的信号电平足够低，以便DUT，但同时允许测量。
来自Keysight的人可以为您提供更多建议，但他们需要了解的不仅仅是您拥有的型号。
2）对于“Unleveled source 1，out 1”警告，手册应该告诉你它的含义。但即使不看手册，我也可以合理地猜测它的含义。但我的猜测可能
很多信号源，不仅仅是VNA，都有一系列功率和频率，它们被指定可以工作，然后是另一个可能工作的范围，但不能保证。如果设置的电平低于-16 dBm，
并且仪器告诉你它是不平衡的，那么功率是不能保证的。可能有一些AGC环路，你超出了它的设计范围。如果你将功率设置为-16.1 dBm，它可能会非常接近。如果
你把它设置为-30 dBm，我怀疑它会非常接近。但是所有保证都是关闭的。忽略这样一条消息最明显的问题是如果-16 dBm对你的DUT来说太高了，那么你可能会得到
-16 dBm，即使你已经要求其他东西了。一个显而易见的问题是你想把什么功率输入DUT？给它
一个有源天线，我猜你想要一个远低于-16 dBm的输入。
在这种情况下，我怀疑你真的不能忽视那些警告，并需要解决这个问题。
在输出上增加一个10 dB衰减器会使信号减少10 dB，但我怀疑-26 dBm对你来说太大了。
我怀疑如果你的VNA有正确的选择，或者你可以购买选项，你可以解决这个问题，但我相信，一旦知道更多关于你的VNA，以及什么信号水平，Keysight的某个人可以给你很好的建议
你真的想要投入DUT。
戴夫



     以下为原文

  > {quote:title=spstefanop wrote:}{quote}
> I use PNA N5221A. I am trying to measure S11 and S21 of of an antenna with an active matching network which needs a dc power suplly (5V, 20mA). At port 2 i use another antenna. Because of the non-linearities introduced by the transistor of the active matching network, i need low power level to verify small signal s-parameters simulation. So when i am trying to set the power level to a value smaller than-16 dbm i receive this error message:'Unleveled source 1, out 1'. I use two port standard SOLT calibration from 100 MHz to 1 GHz. What would possibly cause such an error? How accuracy is affected if i ignore the error message?

Hi, 

I have never used an N5221A - it is well outside my budget! Neither do I work for Keysight. But perhaps the following will be some help though. 

1) You should state what options your instrument has, and firmware version too. 

If you have a configurable test set (whatever option(s) that might be), it may allow you insert some attenuators in appropriate places to keep your signal level low enough for your DUT, but while at the same time allowing a measurement. Someone from Keysight will be able to give you more advice, but they are going to need to know more than just what model you have. 

2) As for the 'Unleveled source 1, out 1" warning, the manual should tell you what it means. But even without looking at the manual, I can take a reasonable *guess* at what it is meaning. But my guess may be wrong. 

Many signal sources, not just VNAs, have a range of powers and frequencies which they are specified to work over, then another range where they might work, but it is not guaranteed. If you set a level below -16 dBm, and the instrument tells you it is unleveled, then that power is not guaranteed. There's probably some AGC loop, and you are outside its design range. If you set the power to -16.1 dBm, the chances are it would be pretty close. If you set it at -30 dBm, I doubt it will be very close at all. But all guarantees are off. 

The most obvious problem with ignoring such a message is that if -16 dBm is too high for your DUT, then you might get -16 dBm, even though you have requested something else. 

An obvious question is what power do you want to put into the DUT? Given its an active antenna, I'm guessing you want to have an input far below -16 dBm. In which case, I suspect you really can't ignore that warnings, and need to address the situation. 

Adding a 10 dB attenuator on the output will reduce your signal by 10 dB of course, but I suspect even -26 dBm will be too much for you. 

I suspect if your VNA has the right options, or you can purchase the options, you can get around this, but I'm sure someone from Keysight can give you good advice once they know a bit more about your VNA, and what signal levels you actually want to put into the DUT. 

Dave

感谢您的答复。
我希望我的输入功率水平低于约-20dbm。
当我在没有直流偏置的情况下测量我的DUT时，即使在-30dbm也没有出现错误消息。
当我也降低直流电压时，可以将输入功率电平设置为小于-16dbm的值。
但我只是扩大了我没有得到任何错误信息的权力范围。
错误消息恰好在较低的输入功率水平下发生。
我无法理解的是我的DUT的直流电源如何与此错误消息相关。



     以下为原文

  Thanks for your response.
I want my input power level to be below about -20dbm.
When i measure my DUT without dc bias, i get no error message even at -30dbm. When i also decrease dc voltage, then it is possible to set input power level to values smaller than -16dbm. But i just widen the range of power in which i dont get any error message. The error message just occurs at lower input power level. What i cant understand is how dc power supply of my DUT is related to this error message.

快速查看规格表，最大电平功率为+20 dBm（在您的频率范围内），功率扫描范围为37 dB，这意味着您应该能够达到-17 dBm。
但典型的扫描范围是47 dB，所以你应该合理地能够低于-20。
但那是50欧姆的比赛。
如果您打开或短路，内部ALC探测器可以看到有效功率的变化高达6 dB，这可能会使您超出ALC驱动器的范围。
当您更改偏差时，如果匹配发生变化，您也可以看到最小功率变化。
例如（一个简单的）如果我们说“我们可以产生低至-17 dBm到50欧姆”但你提供一个开路，那么峰值电压可以高出2倍，并导致高达-11 dBm的低级信息
（我们输出-11 dBm，但由于没有负载从电源吸取电流，因此没有电压在其内部50欧姆上降，因此探测器电压不会达到应有的低水平）。
另一种可能的原因：可能是你的电路振荡并产生一个信号注入信号源，关闭频率使ALC探测器饱和。



     以下为原文

  Looking quickly at the spec sheets the max leveled power is +20 dBm (in your freq range) and the power sweep range is 37 dB, meaning that that you should be able to go to -17 dBm.  But the typical sweep range is 47 dB so you should reasonably be able to get below -20.  But that is into a 50 ohm match.  If you are going into an open or short, the internal ALC detector can see a change of up to 6 dB for effective power, and that can put you out of the range of the ALC drive.  As you change the bias, ,if the match changes, you can see the min power change as well.  For example (a simple one) if we say "we can produce down to -17 dBm into 50 ohms" but you provide an open circuit, then the peak voltage can be 2x higher, and cause an unlevel message as high as -11 dBm (we put out -11 dBm, but because there is no load to draw current from the source, no voltage is dropped across it's internal 50 ohms and so the detector voltage doesn't go as low as it should).

An alternative, though specutlative reason: maybe your circuit is oscillating and creating a signal that is injected back into the source, off freqeuncy that is saturating the ALC detector.