CST MWS - microstrip; length changes S11

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mauloftin

Joined: 29 Oct 2008
Posts: 262
Helped: 22
Location: CZ

09 Oct 2009 7:38 CST MWS - microstrip

Hi,

I am simulating microstrip in CST. But i have problem. If I change length of microstrip changes S11 too. I think, that is not correct.

Can you tell me How should I Set CST?

Thank

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Ice Lord

Joined: 12 Oct 2009
Posts: 3
Location: Germany

12 Oct 2009 12:58 Re: CST MWS - microstrip

I have the same Problem and I dont understand the reason for this effect!

I am using Microwave office, and nobody can explain me why the VSWR changes when i edit the length...
We use RO4350 with a 530um Line.
for expamle we increase the lenght of 1500um to 2500um we have a 5dB change of VSWR!!

biff44

Joined: 24 Dec 2004
Posts: 1838
Helped: 244
Location: New England, USA

12 Oct 2009 13:54 Re: CST MWS - microstrip

The most likely reason is that the line is not 50 ohm, but your two meausrement probes are exactly 50 ohm, so you get VSWR ripples from tripple transit signals. Try simulating from 5 to 25 GHz. Is there a repetitive ripple in the data?