In this paper the definition of characteristic impedance for lossless microstrip and coplanar lines has been considered. It has been shown that due to a significant value of the displacement current related to longitudinal component of the electric field, impedance definition becomes ambiguous. Such ambiguity can cause considerable errors in design procedure. This effect is especially noticeable in the coplanar lines, in opposite to microstrip ones. To confirm the validity of the applied algorithm (spectral domain approach) the propagation coefficients and characteristic impedances have been compared to values obtained from commercial software.
2. Davis, M. E., E. W. Williams, and A. C. Celestini, "Finite-boundary corrections to the coplanar waveguide analysis," IEEE Transactions on Microwave Theory and Techniques, Vol. 21, No. 9, 594-596, September 1973.
3. Knorr, J. B. and K. Kuchler, "Analysis of coupled slots and coplanar strips on dielectric substrate," IEEE Transactions on Microwave Theory and Techniques, Vol. 23, No. 7, 541-548, July 1975.
4. Jansen, R. H., "Unified user-oriented computation of shielded, covered and open planar microwave and millimeter-wave transmission-line characteristics," IEE Journal on Microwaves, Optics and Acoustics, Vol. 3, No. 1, 14-22, January 1979.
5. Bhattacharya, D., "Characteristic impedance of coplanar waveguide," Electronics Letters, Vol. 21, No. 13, 557, June 1985.
6. Itoh, T., Numerical Techniques for Microwave and Millimeter-Wave Passive Structures, John Wiley & Sons, Inc., New York, 1989.
7. Mirshekar-Syahkal, D., Spectral Domain Method for Microwave Integrated Circuits, John Wiley & Sons, Inc., New York, 1990.
8. Stefanski, T. and B. J. Janiczak, "Analysis of single-ground-plane coplanar waveguide," IEEE Microwave and Wireless Components Letters, Vol. 16, No. 7, 395-397, July 2006.
9. Yildiz, C., K. Guney, M. Turkmen, and S. Kaya, "Neural models for coplanar strip line synthesis," Progress In Electromagnetics Research, Vol. 69, 127-144, 2007.
10. Si, L.-M. and X. Lv, "CPW-FED multi-band omni-directional planar microstrip antenna using composite metamaterial resonators for wireless communications," Progress In Electromagnetics Research, Vol. 83, 133-146, 2008.
11. Kumar, A. V. P., V. Hamsakutty, J. Yohannan, and K. T. Mathew, "Microstripline FED cylindrical dielectric resonator antenna with a coplanar parasitic strip," Progress In Electromagnetics Research, Vol. 60, 143-152, 2006.
12. Kanj, H. and M. Popovic, "A novel ultra-compact broadband antenna for microwave breast tumor detection," Progress In Electromagnetics Research, Vol. 86, 169-198, 2008.
13. Marynowski, W. and J. Mazur, "Design of UWB coplanar antenna with reduced ground plane," Journal of Electromagnetic Waves and Applications, Vol. 23, 1707-1713, 2009.
14. Görür, A. and C. Karpuz, "Effect of finite ground-plane widths on quasistatic parameters of asymmetrical coplanar waveguides," IEE Proceedings --- Microwaves, Antennas and Propagation, Vol. 147, No. 5, 343-347, October 2000.
15. Monti, G. and L. Tarricone, "Negative group velocity in a split ring resonator-coupled microstrip line," Progress In Electromagnetics Research, Vol. 94, 33-47, 2009.
16. Abdelaziz, A. F., T. M. Abuelfadl, and O. L. Elsayed, "Realization of composite right/left-handed transmission line using coupled lines," Progress In Electromagnetics Research, Vol. 92, 299-315, 2009.
17. Vazquez Antuna, C., G. Hotopan, S. Ver Hoeye, M. Fernandez Garcia, L. F. Herran Ontanon, and F. Las-Heras, "Microstrip antenna design based on stacked patches for reconfigurable two dimensional planar array topologies," Progress In Electromagnetics Research, Vol. 97, 95-104, 2009.
18. Aliakbarian, H., A. Enayati, G. A. E. Vandenbosch, and W. De Raedt, "Novel low-cost end-wall microstrip-to-waveguide splitter transition," Progress In Electromagnetics Research, Vol. 101, 75-96, 2010.
19. Wang, Z., Q. Lai, R.-M. Xu, B. Yan, W. Lin, and Y. Guo, "A millimeter-wave ultra-wideband four-way switch filter module based on novel three-line microstrip structure band-pass filters," Progress In Electromagnetics Research, Vol. 94, 297-309, 2009.
20. Williams, D. F., B. K. Alpert, U. Arz, D. K. Walker, and H. Grabinski, "Causal characteristic impedance of planar transmission lines," IEEE Transactions on Advanced Packaging, Vol. 26, No. 2, 165-171, May 2003.
21. Schmidt, L. and T. Itoh, "Spectral domain analysis of dominant and higher order modes in fin-lines," IEEE Transactions on Microwave Theory and Techniques, Vol. 28, No. 9, 981-985, September 1980.
22. Knorr, J. B. and A. Tufekcioglu, "Spectral-domain calculation of microstrip characteristic impedance.," IEEE Transactions on Microwave Theory and Techniques, Vol. 23, No. 9, 725-728, September 1975.
23. CST microwave studio (CST MWS), https://www.cst.com.
24. Advanced design system --- momentum, agilent technologies, http://www.agilent.com.