Linecalc

This app caliculates the impedance of various types of transmission lines.
[reference]
H.A.Wheeler,"Transmisson-Line Properties of a Strip on a Dielectric Sheet on a Plate", IEEE Trans. Microwave Theory Tech., vol.MTT-25, No.8, Aug 1977.
M.Kirschning and R.H.Jansen, "Accurate Wide-Range Design Equqtions for the Frequency-Dependent Characteristic of Parallel Coupled Microstrip Lines", IEEE Trans. Microwave Theory Tech., vol.MTT-32, No.1, Jan 1984.
IPC-2141A, "Design Guide for High-Speed Controlled Impedance Circuit Boards", Mar 2004.