GATE 2014 EC (EC2) – Question 34
The shown lossless transmission line is matched to a resistive load by a λ/4 transformer. Find transformer characteristic impedance (Ω).
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Correct answer: 70 to 72
Explanation
A lossless quarter-wave section transforms a real load RL into Zin=Zt²/RL. Requiring Zin=50Ω with RL=100Ω gives Zt=√(50×100)=**70.7107Ω**. The transformer impedance is the geometric mean of the two matched resistances.