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bbspice fitting process taking too much time

Hi,

I have an S parameter file generated by EMX for my oscillator. It has 56 ports and was simulated from DC-900GHz with a 1GHz step. When I used bbspice as the interpolation method for the nport, the rational fitting takes almost 1 day and still has not finished. Could you suggest some techniques I could use to reduce the fitting time? Here I have kept the nport compression as default. I'm curious since Tawna mentioned in an earlier thread that she used to simulate an n-port with 405 ports (https://community.cadence.com/cadence_technology_forums/f/rf-design/37979/how-to-compare-what-spectre-interprets-from-the-raw-s-parameter-file/1352837#1352837).

I'm using Spectre Version 16.1.0.510.isr10 64bit -- 13 Oct 2017, Virtuoso IC6.1.7-64b.500.15, EMX 5.12, interface date 15/7/2020.

I include here the settings for my nport, and the screenshot from transient simulation showing the iterations of the fitting process.

Many thanks and regards,

Anh

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anhchu88 over 4 years ago

For your more information, I attach the settings in EMX as below.

I used additional commands for emx: --double-precision --ans=1e-4 --print-double --solve-for-s --uniform-sources

BR Anh
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Frank Wiedmann over 4 years ago in reply to anhchu88

If EMX produces non-passive S-parameter data, this is probably a bug that you should report to https://support.cadence.com. As a quick fix, especially if your circuit does not really work at these extremely high frequencies, you could try to simply remove all the data above 700 GHz or so from the S-parameter data file.
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Frank Wiedmann over 4 years ago in reply to anhchu88

If EMX produces non-passive S-parameter data, this is probably a bug that you should report to https://support.cadence.com. As a quick fix, especially if your circuit does not really work at these extremely high frequencies, you could try to simply remove all the data above 700 GHz or so from the S-parameter data file.
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