Transmission Line Math |
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These two workbooks show various formulas that are used when dealing with transmission lines.
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T-Line Model.xls shows the details of the mathematical model for transmission lines that is used by the Zplots and TLDetails applications.
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T-Line Measure.xls shows how the characteristic impedance Zo and the propagation constant γ (gamma) may be obtained from two basic impedance measurements, one with the transmission line terminated with an open circuit and a second with a short circuit termination.
The math behind using open/short measurements to determine transmission line characteristics is described in section 7.5, pp. 134-136, of the Chipman text (Robert A. Chipman, Theory and Problems of Transmission Lines, 1968). You can read those three pages here.
Also, W8WWV wrote up some thoughts on this technique.
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Both workbooks make use of the Excel complex number functions. Under Excel 2003 and earlier, click on Tools >
Add-Ins and make sure "Analysis ToolPak" is checked. Under Excel 2007 and later no special action is needed.
Download:
Download T-Line Model.xls and/or T-Line Measure.xls. Free.
Neither of these workbooks contain macros. They may be used with Open Office Calc.