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Impedance matching on CST

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rmmstn

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Hello :)

Currently, I am trying to create a network for matching 50ohms to 100ohms in CST. However, im having trouble while introducing the port impedances. My investigations show that discreet port would not be accurate as waveguide port. Therefore, I placed one waveguide port which is 50 ohm to the one port of the network, and I connected a lumped element(100ohm) which is from the ground plane to the top of the transmission line (so the whole thickness is covered actually) at the other port. However, it was not simulated since I am getting an error which is "the surface is not supported over the surface"(thats not the exact expression that cst gives btw.). If I connect a discreet port instead of the lumped element and adjust its impedance as 100ohm. Would the result I get be correct? In this case, I will have one waveguide and one discreet port. If not, how should I solve this matching problem? I really checked everything, but couldnt get an absolute answer.
 

Bryson

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I think the discrete port would be accurate if the width of the transmission line is narrow.
 

radiohead

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I would suggest to use a second waveguide port. This can be also 50ohm, and then you post-process the S-parameters using template based post-processing to change the impedant at port 2 to 100 ohm. Alternatively you change the line impedance at port to 100 ohm directly and you'll see the results wi
 
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    rmmstn

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rmmstn

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Thank u all for turning back.

AKHİLPAULV, I am attaching the screenshots here for you. One is showing the error, one is showing according to what I put the waveguide port.

RADIOHEAD, I did what you said. It seems fine.I wasn't adjusting 50ohm btw, I know that when u put a port in cst, it is coming by 50ohm default(that is why I said 50 is adjusted). When I change the both impedances by using "renormalizing port impedances" option under post processing, difference occurs :) I just put the ports, simulated and then I wrote values for both of them 50 and 100ohm as you said, so is that the way of implementing impedance matching on cst? If so, thank you a lot.

BRYSON, the transmission line is a tapered line, broad side is 6mm wide, while the narrow side is 2mm wide. The thichness of the transmission line is 0.5mm. How much narrow did you mean?

simulation.pngport.png
 

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