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Question about S-Parameters on Frequency Translation Devices

Question asked by Kanwal on Mar 27, 2015
Latest reply on Feb 2, 2016 by Dr_joel

    I have a question regarding VNA testing on frequency translation devices.

I have tested passive and active devices before on VNA but usually under normal settings, like center frequency and span. That is input frequency sweep on port 1 is same as output port on port 2.

Right now am testing Satellite Block up converters(BUC) and Low Noise Blocks.(LNB)

Here input to BUC is in L-Band(1-1.5 Ghz) and output is in Ku-Band(~14 Ghz).

Testing parameters like Gain,Gain ripple,Phase,Group Delay,Compression.

The whole setup is automated and at first i couldn't figure out anything. 

Instead of usual port 1 and port 2, input seems to be going from source out (from external port 1 on the left side,regular port 1 is not used at all) and output is in port 2.By stopping the software and tinkering a little with the set up, it indeed became clear that the VNA was sending signal at L Band from source even though the front display was showing Ku Band.(there was a feature of frequency offset and frequency settings also confirmed it).

The reverse was true for LNB. Ku-Band signal will go from source output port and L Band output is shown on display.

There is a test box with a switch matrix in the middle of input and output and all testing is done through sample ports on the modules.

Also the display is clearly not measuring S-parameters, its showing something like B1,1(apologies if its wrong, i should have taken a screenshot). Probably its showing the value at Port 2(Port 2 = B?)

So, seems like measurements are calculated by comparing the input signal from the source port and the received signal at port 2.(displayed on the computer screen by the software).

From my understanding, S-parameters are defined in real and imaginary parts and one can calculate Gain and Loss from there, and this is done at each frequency interval between the span.

So, is it possible to extract S-parameters for these BUC and LNB devices and how.

Also related question is, a mixer has similar setup with different input and output frequencies.How is compression and conversion gain measured and are those also defined in S-parameters?

The VNA used is N5230C



Edited by: Kanwal on Mar 27, 2015 8:07 PM

Edited by: Kanwal on Mar 27, 2015 8:09 PM

Edited by: Kanwal on Mar 27, 2015 8:11 PM