如何使用75欧姆VNA进行50欧姆的测量？

> {quote：title = mirek写道：} {quote}>你唯一的选择就是在每个端口上使用匹配的打击垫。
标准电阻匹配垫的问题在于它们具有大约5.7dB的插入损耗，并且网络分析仪在回波损耗的动态范围内将损失大约11.4dB，在某些情况下可能是一个问题，但您不会有任何频率限制。
如果您的操作频率不能覆盖整个3GHz并且您担心电源丢失，您可以尝试使用变压器基座匹配电路。
我看到的例子可以在1MHz到1.5GHz之间工作，性能非常合理：插入损耗高达0.5dB，回波损耗高于20dB。
谢谢。
8751A的频率上限仅为500 MHz，因此变压器的1.5 GHz频率上限不会成为问题。但他希望响应低至5 Hz，因此变压器不是一种选择。
我怀疑电阻焊盘可能是要走的路，虽然从他的说法来看，75欧姆测试装置似乎已经将电阻焊盘转换为50欧姆至75欧姆。
我想这是否有可能从75欧姆版本更改测试集，使其成为50欧姆版本。
也就是说，这样做可能会使测试集贬值（尽管可能会增加其价值！），并且意味着安捷伦可能永远不会尝试校准测试集。
我怀疑外面的电阻垫是最好的选择。
DaveEdited：drkirkby于2012年12月19日上午9:54



     以下为原文

  > {quote:title=mirek wrote:}{quote}
> The only option that you have is to use matching pads on each port. The problem with standard resistive matching pad is that they have around 5.7dB insertion loss and the Network Analyzer will lose around 11.4dB in dynamic range for Return Loss, that in some cases might be a problem, but you will not have any frequency limitation. If your frequency of operation do not cover entire 3GHz and you are concern about loss of the power, you may try transformer base matching circuits. I see example that can operate from 1MHz up to 1.5 GHz with very reasonable performance: Insertion loss up 0.5dB and return loss better than 20dB.


Thank you. 

The upper frequency limit of the 8751A is only 500 MHz so a 1.5 GHz upper frequency limit of a transformer would not be a problem.. But he wants response down to 5 Hz, so the transformer is not an option. 

I suspect resistive pads is probably the way to go, although from what he says, the 75 Ohm test set appears to have resistive pads already which convert 50 Ohms up to 75 Ohms. 

I guess it leaves the question as to whether it is possible to change the test set from the 75 Ohm version, to make it a 50 Ohm version. That said, doing that would probably devalue the test set (though perhaps it would increase its value!), and mean Agilent would probably never attempt to calibrate the test set. 

I suspect resistive pads on the outside is the best option. 

Dave

Edited by: drkirkby on Dec 19, 2012 9:54 AM

噢我没有依赖8751 ..源，R接收器和A接收器有50欧姆的N型连接器吗？
如果是这样，请查看87512A传输/反射测试装置的互联网。
有人应该为便士出售。
我想知道8751是否有可以移除的B接收器匹配垫。
接收器本身应为50欧姆。
否则，只需放入匹配垫，你就回家了。
我记得8751也可以选择全传输/反射测试装置（87511A），但最低频率限制在100KHz。
那是一种潮人。



     以下为原文

  Ooo I did not relies that 8751.. 

Does the Source, R Receiver and A receiver have 50 Ohms N-type connector? If so look at the internet for 87512A transmission/reflection test set. Somebody should sell that for penny's. I wonder if 8751 have on B receiver matching pad that you could remove. The receiver itself should be 50 Ohms. Otherwise, just put in there matching pad and you are home. 

I remember the 8751 also have option for full transmission/reflection test set (87511A) however the lowest frequency was limited to 100KHz. That was kind of boomer.

> {quote：title = mirek写道：} {quote}>噢我没有依赖那个8751 ..>> Source，R Receiver和A接收器有50欧姆的N型连接器吗？
我假设但不知道。
我从未见过它。
>如果是这样，请查看87512A传输/反射测试装置的互联网。
有人应该为便士出售。
我想知道8751是否有可以移除的B接收器匹配垫。
接收器本身应为50欧姆。
否则，只需放入匹配垫，你就在家他有75欧姆测试装置，我认为想要修改它而不是购买另一个测试装置。
>我记得8751也可以选择全传输/反射测试装置（87511A），但最低频率限制在100KHz。
那是一种潮人。
你让我想到那里。
他认为这是测试集中的一个问题。
我怀疑任何变压器都能以5 Hz的频率工作，所以也许测试装置对他来说没用，因为他需要以5 Hz的频率工作。
戴夫



     以下为原文

  > {quote:title=mirek wrote:}{quote}
> Ooo I did not relies that 8751.. 
> 
> Does the Source, R Receiver and A receiver have 50 Ohms N-type connector?

I assume so but do not know. I have never seen it. 

>  If so look at the internet for 87512A transmission/reflection test set. Somebody should sell that for penny's. I wonder if 8751 have on B receiver matching pad that you could remove. The receiver itself should be 50 Ohms. Otherwise, just put in there matching pad and you are home

He has the 75 Ohm test set and I think was wanting to modify that rather than buy another test set. 

> I remember the 8751 also have option for full transmission/reflection test set (87511A) however the lowest frequency was limited to 100KHz. That was kind of boomer.

You are making me think there. He thought theere was a blaun in the test set. I doubt any transformer can work at 5 Hz, so perhaps the test set is useless to him, as he needs to work at 5 Hz.

Dave