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MATLAB Demonstration of Transmission Line Phenomena in Electromagnetics

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2012 ASEE Annual Conference & Exposition


San Antonio, Texas

Publication Date

June 10, 2012

Start Date

June 10, 2012

End Date

June 13, 2012



Conference Session

Software and Web-based Learning in ECE

Tagged Division

Electrical and Computer

Page Count


Page Numbers

25.918.1 - 25.918.12



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Paper Authors


Stuart M. Wentworth Auburn University

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Stu Wentworth received his electrical engineering doctorate from the University of Texas, Austin, in 1990. Since then, he has been with Auburn University’s Department of Electrical and Computer Engineering, specializing in electromagnetics and microelectronics. He has authored a pair of undergraduate electromagnetics texts and has won several awards related to teaching. He is the department’s undergraduate Program Director and Chair of its Curriculum and Assessment Committee.

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MATLAB Demonstration of Transmission Line Phenomena in ElectromagneticsTransmission lines constitute an important application of electromagnetics. Signal reflection andimpedance matching are critical concepts in wireless communications and radar. However, whilestudents often can properly apply formulas to solve transmission line problems, they often lack a deepunderstanding of how these lines work. MATLAB can serve as a useful tool for illuminating theoperation of transmission lines. For instance, a MATLAB movie can demonstrate wave travel on aterminated transmission line, and can also show how a so-called standing wave is established.The first investigation in this paper demonstrates under what conditions a length of connecting wire mustbe treated as transmission line. Essentially, if the operating frequency is high enough that the wire lengthis a significant portion of a wavelength, then a transmission line model must be used. Here, a MATLABdemonstration clarifies when this is so and why it is important.The second investigation concerns wave propagation in an impedance matching network realized usingsections of transmission line (the so-called stub matching network). A MATLAB demonstration showshow the waves on each section of line behave and how they combine to achieve the impedance matchingcondition. An especially interesting aspect of this problem concerns how long after the wave is launchedit takes for the matching condition to be achieved, and how the waves perform in the meantime.

Wentworth, S. M. (2012, June), MATLAB Demonstration of Transmission Line Phenomena in Electromagnetics Paper presented at 2012 ASEE Annual Conference & Exposition, San Antonio, Texas. 10.18260/1-2--21675

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