Transmission-line theory — infinite (endless) line behavior Statement: In an infinite line, the input impedance at every point equals the characteristic impedance Z0. Choose the correct truth value.

Difficulty: Easy

Correct Answer: True

Explanation:


Introduction / Context:
The concept of an ‘‘infinite’’ transmission line is a theoretical construct where the line extends without termination, so no reflection ever returns. Understanding its input impedance clarifies why a finite line perfectly terminated in Z0 appears the same to the source.


Given Data / Assumptions:

  • Uniform, lossless or low-loss line with characteristic impedance Z0.
  • No discontinuities or terminations to cause reflections.


Concept / Approach:
With no reflection, the voltage and current form a pure traveling wave. The ratio V/I remains constant everywhere and equals Z0. Thus, the input impedance looking into any point of an infinite line is Z0, independent of distance along the line.


Step-by-Step Reasoning:

1) Infinite length → no reflection from any end.2) Pure traveling wave → constant V/I ratio.3) Therefore Z_in = V/I = Z0 at every point.


Verification / Alternative check:
Equivalently, a finite line terminated in Z0 has Γ = 0 and presents Z0 at its input, mimicking the infinite-line condition.


Why Other Options Are Wrong:

  • False: would imply some position-dependent impedance despite the absence of reflections, which contradicts traveling-wave theory.


Common Pitfalls:
Confusing standing-wave patterns (which require reflections) with the reflection-free traveling-wave case.


Final Answer:
True

More Questions from Microwave Communication

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion