完整的2端口与经济VNA有什么作用

如果你想描述一个双端口非互易设备 - 比如一个放大器 - 每次调整某些东西时，必须交换输入和输出连接以测量所有四个S参数是一件痛苦的事情。
当您不必在测量之间操纵电缆时，精度也会更好。



     以下为原文

  If you want to characterize a two-port nonreciprocal device -- say, an amplifier -- it's a pain in the neck to have to exchange the input and output connections to measure all four S-parameters every time you tweak something.  Accuracy is also better when you don't have to manipulate the cables between measurements.

> {quote：title = DaveAK78写道：} {quote}>嗨，我很好奇获得一个完整的2端口VNA的优点，它可以同时测量S11，S21，S12，S22与刚测量的经济型号相比
S11，S21 - 什么类型的应用程序是完整的测量功能？
我猜这对于非被动/非互惠网络很有用，但是在表征有源RF网络方面没有多少经验，所以任何反馈都会受到高度赞赏。
非常感谢，Dave我假设您正在将网络分析仪与S参数测试集进行比较，而不是那些具有传输/反射（T / R）测试集的网络分析仪。
大多数（可能全部）VNA不能同时测量所有4个S参数。
源在不同的端口之间切换 - 首先将源连接到端口1，然后连接到端口2，然后再连接到1等。可以使用双源获得高端VNA。
我不知道他们是否可以同时测量S11，S21，S12和S22。
大多数无源器件具有S12 = S21，尽管存在诸如隔离器和循环器之类的例外。
但S11，即使在被动设备上也不会与S22相同，所以John Miles说，你需要转动设备。
具有S参数测试集还有其他优点。
*您可以进行未知的校准，从而消除适配器的影响。
*您可以进行TRL校准，如果使用测试夹具，或者您没有DUT校准套件的其他情况，这是特别好的。
这些校准方法需要一个带有4个接收器的VNA，这在低端型号上是不可用的。
8753系列没有4个接收器，它是8720系列的选件，也是8510系列的标准配置。
4个接收器可能是目前安捷伦/是德科技PNA的标准配置，尽管我并不是100％肯定。
您是否想购买新的或二手的VNA？
如果您的预算仅限于使用的VNA，那么8753系列很难被击败。
戴夫



     以下为原文

  > {quote:title=DaveAK78 wrote:}{quote}
> Hi, I'm curious about the advantages of getting a full 2-port VNA which can simultaneously measure S11, S21, S12, S22 compared with the economy models which just measure S11, S21 - what type of applications is the full measurement capability useful for? I'm guessing it's useful for non-passive/non-reciprocal networks, but don't have much experience with characterizing Active RF networks, so any feedback would be greatly appreciated. Many Thanks, Dave

I assume you are comparing network analyzers with S-parameter test sets, against those with transmission/reflection (T/R) test sets. 

Most (perhaps all) VNAs can't measure all 4 S-parameters simultaneously. The source is switched between different ports - first the source is connected to port 1, then to port 2, then back to 1 etc.  It is possible to get high-end VNAs with dual sources. I don't know if they can simultaneously measure S11, S21, S12 and S22. 

Most passive devices have S12=S21, although there are exceptions such as isolators and circulators. But S11, will not be the same as S22, even on passive devices, so as John Miles says, you need to turn the device around. There are other advantages in having an S-parameter test set. 

* You can do unknown thru calibration, which removes the effect of adapters. 
* You can do TRL calibration, which is particular good if using test fixtures, or other cases where you don't have a calibration kit for the DUT. 

Those calibration methods need a VNA with 4 receivers, which are not available on low-end models. None of the 8753 series have 4 receivers, it is an option on the 8720 series, and standard on the 8510 series. 4 receivers is probably standard on current Agilent/Keysight PNAs, although I'm not 100% sure of that. 

Are you looking to buy a new or used VNA? If your budget is limited to used VNAs, the 8753 series is hard to beat. 

Dave