Hi All,
I have a balanced 50 ohm 915MHz filter on a PCB that I need to test. Would it work OK if I simply shunted one leg of the balanced filter's input and output with a 50 ohm resistor to ground, while sweeping the other balanced input and output with a VNA? Is this the easiest way to test a balanced circuit for gain and return loss with a typical VNA? (I have no room at all to place 1:1 baluns on my PCB for the (unbalanced) 50 ohm VNA).
Thanks!
-Bill
Have a look on Agilent's website. I believe that the "proper" method is to put a connector on every trace going into or out of the device under test, and then to measure in turn between every possible pair of two ports, whilst all other ports are terminated in very good 50 Ohm loads. Then all of these separate traces are put into some software and it will give you the answers you need. The whole process is so long and complicated that instead of doing that, some people go and buy / hire / "borrow for evaluation, because we're thinking of buying" a 4 port VNA or if they don't really need an accurate answer then they use baluns etc.
Chris
Unless your parameters are truly difficult, just plug it in to your unbalanced (normal) VNA. Works pretty well up to 6GHz, of course terminations are paramount.
-- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
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