The GATE Grind

GATE 2014 EC (EC3) – Question 35

Electromagnetics · Transmission Lines · 1 mark · Multiple choice

Transmitter Tx sends a wideband modulated RF signal through the coaxial cable shown to receiver Rx. Transmitter output Z_T, cable characteristic Z₀ and receiver input Z_R are real. Which statement about mismatch distortion is TRUE?

Diagram for GATE 2014 EC (EC3) question 35
  1. Signal is distorted whenever Z_R ≠ Z₀, regardless of Z_T.
  2. Signal is distorted whenever Z_T ≠ Z₀, regardless of Z_R.
  3. Signal distortion implies mismatches at both ends: Z_T ≠ Z₀ and Z_R ≠ Z₀.
  4. Mismatches never distort signals; they only reduce power-transfer efficiency.

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Show answer and explanation

Correct answer: (C) Signal distortion implies mismatches at both ends: Z_T ≠ Z₀ and Z_R ≠ Z₀.

Explanation

If either end is matched, a returning reflection is absorbed or none is produced, leaving a scaled and delayed copy under the ideal-line assumptions. Multiple delayed echoes require reflection coefficients nonzero at both ends. Thus distortion from mismatch implies **ZT≠Z0andZR≠Z0,C**. Both mismatches are a necessary condition here, not a universal sufficient condition for every possible waveform.