snp file format

Hi guys, I know this question is very basic but it really bothers me...

I am using a s1p block in my ADS project, which contains z-parameters only. What i want to do is to measure the s-parameters of this device and plot it on a graph.

However, there are several problems.

1) The s-parameter plot looks very much like the impedance amplitude and for some frequencies, it is much greater than 1. This is really abnormal and my device is just a resonator, a passive device.

2) The warning keeps showing me that : "Data in the Touchstone file "C\..." does not cover the requested value of 'freq'. Therefore, the required data was obtained by extrapolation."
I guess this might be the reason for my problem 1. However, I really cannot figure out why my s1p file does not cover frequency. Is there any problem with my s1p format? It looks good to me, though.....

So, what is wrong here? Can anybody tell me?

Here i attached my screenshots of ADS schematic, s11 plotting, s1p file and the warning window.

PS: i use term block at the "ref" because i treat it as a load, it is not a port.

SherryWang on Nov 23, 2015 1:31 AM

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Your data file shows impedance data in real and imaginary format, with negative real part at many frequencies, I don't think your data is representing a passive resonator. As a "sanity check," you could run a 1-port simulation, output Z-parameters, and make sure that what you get from this simulation matches what is in the file.

Thank you so much for solving my doubts! ^ ^
- I have tried your method. When i retract one port and replace it with a GND, the Z-parameter showed on the graph is a constant number, e.g. 50 ohm. I guess this is the impedance it measures from the term block. I am totally confused here.
- By the way, do you know the reason why the ADS keeps warning me my s1p file does not cover the required value of 'freq'?

You are simulating from 2.3 GHz to 2.8 GHz but the data starts at 2.31 GHz so the first frequency point is out or the range of the data. Can't see the top end so that may have a problem too but can't tell from the picture.

Probably contacting our Tech Support would be the fastest way to get this resolved.

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