# Transmission line design - RF Cafe Forums

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boon

Post subject: Transmission line design Posted: Sat Jul 22, 2006 3:10 pm

Captain

Joined: Tue Feb 21, 2006 5:19 pm

Posts: 17

Hello,

What's the best way of designing transmission line matching circuits using CAD tools? I am doing a simple single stub tuned match. I have a series line and a open-circuit shunt stub. I used the ideal Tline components in ADS to design the match so I have the value of electrical lengths for both series and the stub. Then, since I know the frequency and effective permittivity I got the approx. guided wavelength; then using

physical length (L) = ((guided wavelenth)*(electrical length))/360

I got the approx. physical length of the transmission line. Then, I went in Sonnet and drew up the line and did EM simulation. But, now I am stuck. For series line, I pretty much was able to match what ADS had i.e. if the electrical length was 20 deg in ADS for series line, its S21 mag. and phase was close to the line simulated in Sonnet. However, I cannot get the Sonnet simulation to match the open-circuit stub. Its phase way way different and I can't figure it out.

Is the way I am doing sound? Now, I am doubting about using the ideal Tlines but my thinking was as long as I am able to match s-param, especially S21, of these ideal Tlines to the simulated lines it should give me the same match.

boon

Posted  11/12/2012