Author Topic: Disparity Between Datasheet and S-param Model for Mini-Circuits Transformer  (Read 547 times)

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Offline niconiconiTopic starter

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It's me again, asking another RF noob question.

I'm trying to learn the behavior of a RF impedance transformer at different frequencies, and I used Mini-Circuits T16-1-KK81+ (0) (impedance radio 1:16) as my example. I want to look at its complex impedance (S11) on a Smith Chart when the secondary is terminated with a matched load. Mini-Circuits provided a raw 4-port S-parameter model (1) measured by a VNA for simulation, so I downloaded the model and imported it in the Qucs simulator and obtained some results.

The shape of the curve is identical, but the numerical values don't match the S11 shown in the datasheet (2), S11 has an error of around 6 dB, please see the attached screenshots. For exmaple, the return loss in datasheet is around 2 dB at 100 MHz, but the simulator says it's 5 dB.

Is it possible that my simulation setup is incorrect? I'm sure it's not a glitch in the simulator, I tried ADS2008 and I obtained the same results. I believe the different is due to the fact that the device is measured under different conditions, the official return loss figures are measured with a matched 800R load, but the S-parameters are measured by a 4-port 50R VNA, so the error is inevitable? Is it the correct interpenetration of my results?

Also, the Smith Chart shows the transformer becomes capacitive at high frequencies, is it normal? I would expect a transformer to be inductive.

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(0) https://www.minicircuits.com/WebStore/dashboard.html?model=T16-1-KK81%2B

(1) https://www.minicircuits.com/pages/s-params/T16-1-KK81+_S4P.zip

(2) https://ww3.minicircuits.com/pdfs/T16-1-KK81.pdf
« Last Edit: October 18, 2019, 08:32:15 pm by niconiconi »
 


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