Stats

Locked Locked
Replies 15
Subscribers 129
Views 25319
Members are here 0

This discussion has been locked.

You can no longer post new replies to this discussion. If you have a question you can start a new discussion

plotting Smith charts

Hello,

I'm running an .sp analysis with a simple setup--port set to 100ohm, with 100ohm load. I'm plotting results on a Z-Smith, which i thought should give me Re(Z)=1 (normalized)... but instead I'm getting something like 2e-12 as the prime center. I don't understand why this is the case. I'm relatively new to Smith charts, but I'm guessing the plot actually shows reflection coefficient, not the impedance? If this is the case, how can I request an impedance plot?

I'm on version 6.1.8.

Many thanks in advance for your help,
David

Parents

ZoltanT over 5 years ago

Hi dzakharian,

It seems good to me. You have a 100 Ohm reference system loaded with 100 Ohm. No reflection, so S11=0. The 2p is probably numerical error. 2e-15 is very good accuracy!

The Z- and Y-Smiths returns the same reflection coefficient plane, just with different grids. Clearly this is not how one works with Smith charts on paper, but once the server does all the calculations it is great, or even better.

Regards,
Zoltan
Cancel
Vote Up 0 Vote Down

Cancel
dzakharian over 5 years ago in reply to ZoltanT

Hi Zoltan,

Yes, the matching at S11=0 is perfect, in terms of scattering parameters. But I'm interested in the actual impedance, not scattering parameters (so Z11, not S11).
Cancel
Vote Up +1 Vote Down

Cancel
Andrew Beckett over 5 years ago in reply to dzakharian

Why not plot Z11 then? You could plot zpm('sp 1 1) on a polar chart (not sure it makes much sense to plot Z11 on a Smith Chart, but I'm not a microwave engineer so I might be talking rubbish). You can also plot real(zpm('sp 1 1)) and imag(zpm('sp 1 1)) on a rectangular graph to see the complex impedance that way. Or plot one versus the other with waveVsWave.

Andrew.
Cancel
Vote Up 0 Vote Down

Cancel
ZoltanT over 5 years ago in reply to dzakharian

It is also there.
Cancel
Vote Up 0 Vote Down

Cancel
ZoltanT over 5 years ago in reply to Andrew Beckett

Andrew, a stereotypical typical microwave engineer is more likely to think in terms of normalized waves, than fuddling with impedances or dealing with the differences between a current or voltage signal.
Cancel
Vote Up 0 Vote Down

Cancel

Reply

ZoltanT over 5 years ago in reply to Andrew Beckett

Andrew, a stereotypical typical microwave engineer is more likely to think in terms of normalized waves, than fuddling with impedances or dealing with the differences between a current or voltage signal.
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.