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I am practising questions from old tests for an upcoming exam on EM fields and waves. I came across this question which has me confused. I'm not sure where to start.

A lossless TL of length l and characteristic impedance of Z_0 has its ends joined together forming a loop as shown below. Find the input impedance Z_in.

enter image description here

Is this an open circuit termination? How is the TEM wave travelling in this circuit. This circuit looks bizarre compared to the typical TL questions that I see.

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  • \$\begingroup\$ First you say "power systems", then later "TEM wave"...are you sure you're interpreting this question in the right context? \$\endgroup\$
    – The Photon
    Commented Jun 5, 2017 at 3:53

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Treat it as two open circuit lines of half the length connected in parallel.

Consider what happens at the point diametrically opposite the feed. In the loop case you've shown, the wavefront continues on into the 'other half'. In the simplified version, it's reflected at the open circuit. Compare one situation with the other!

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