Transmission line IHP PDK

[mohemza]

Hi @ra3xdh, I recently read your paper on transmission lines and microstrip lines modeling in qucs-s and would like to extend the models that are present (like Wheeler and Hammerstad) to more accurate models that can model lines embedded in a dielectric environment, as found in IC processes (with ground below and surrounding dielectric) as part of my internship at IHP. Do you perhaps have any leads on relevant models or literature I could explore? Thanks!

[ra3xdh]

Hello,

Thanks for the interest in this research! Here is the list of references about MS lines modelling. The underlying mathematics of TL models in Qucsator, ScikitRF, and Ngspice are taken from the mentioned sources. The possibles patches should be targeted to Ngspice first. The sourceforge.net/p/ngspice/ngspice/merge-requests/33/ could be used as reference. The GUI entries for MS lines in Qucs-S may be corrected if necessary.

1. E. Hammerstad and Ø. Jensen, "Accurate Models for Microstrip Computer-Aided Design", Symposium on Microwave Theory and Techniques, pp. 407-409, June 1980.
2. M. Kirschning and R. H. Jansen, "Accurate Model for Effective Dielectric Constant of Microstrip with Validity up to Millimeter-Wave Frequencies", Electronics Letters, vol. 8, no. 6, pp. 272-273, Mar. 1982.
3. R. H. Jansen and M. Kirschning, "Arguments and an accurate Model for the Power-Current Formulation of Microstrip Characteristic Impedance", Archiv für Elektronik und Übertragungstechnik (AEÜ), vol. 37, pp. 108-112, 1983.
4. M. Kobayashi, "A Dispersion Formula Satisfying Recent Requirements in Microstrip CAD", IEEE Trans. on Microwave Theory and Techniques, vol. 36, no. 8, pp. 1246-1250, Aug. 1988.
5. M. V. Schneider, "Microstrip Lines for Microwave Integrated Circuits", The Bell System Technical Journal, vol. 48, pp. 1421-1444, May 1969.
6. M. V. Schneider, "Microstrip Dispersion", Proceedings of the IEEE, Letters, vol. 60, Jan. 1972, pp. 144-146.
7. H. A. Wheeler, "Transmission-Line Properties of a Strip on a Dielectric Sheet on a Plane, IEEE Trans. on Microwave Theory and Techniques, vol. 25, no. 8, pp. 631-647, Aug. 1977.
8. H. A. Wheeler, "Formulas for the Skin Effect," Proceedings of the IRE, vol. 30, no. 9, pp. 412-424, Sept. 1942.
9. E. Yamashita, K. Atsuki, and T. Ueda, "An Approximate Dispersion Formula of Microstrip Lines for Computer Aided Design of Microwave Integrated Circuits", IEEE Trans. on Microwave Theory and Techniques, vol. 27, pp. 1036-1038, Dec. 1979.
10. C. Svensson, G.E. Dermer, Time domain modeling of lossy interconnects, IEEE Trans. on Advanced Packaging, May 2001, N2, Vol. 24, pp.191-196.
11. Djordjevic, R.M. Biljic, V.D. Likar-Smiljanic, T.K. Sarkar, Wideband frequency-domain characterization of FR-4 and time-domain causality, IEEE Trans. on EMC, vol. 43, N4, 2001, p. 662-667.

[ra3xdh]

Another good source on transmission lines modelling is Qucsator technical manual: https://qucs.sourceforge.net/tech/technical.html The computations are based on the articles mentioned above.

The guides how to design XSPICE models:

• Ngspice manual Sections 21-24: https://ngspice.sourceforge.io/docs/ngspice-html-manual/manual.xhtml#magicparlabel-32157
• My presentation from MOS-AK event in 2017: https://mos-ak.org/lausanne_2017/presentations/T03_Kuznetsov_MOS-AK_DATE_2017.pdf

[mohemza]

Thank you for all the sources! I have found equations in the Transmission Line Design Handbook by Brian C. Wadell which describe the normalisations required to model a buried (embedded) microstrip line. I compared the results with accurate models we have of the microstrip lines and they seem to be quite close. I am currently adding these formulas to ngspice and adding the options in the properties of the transmission line in Qucs-S.