What does a zero reflection coefficient indicate in a transmission line?

• A. It means the line is perfectly mismatched
• B. Γ is zero when ZL equals Z0
• C. It indicates there is an actively generating source on the line
• D. It indicates a perfect match where ZL equals Z0

Answer: (D)

Zero reflection means all the energy that reaches the load is not reflected back toward the source; the line and load are in perfect harmony. This happens when the load impedance ZL exactly equals the line’s characteristic impedance Z0. The reflection coefficient Γ, which tells you how much of the wave is reflected, is defined as Γ = (ZL − Z0) / (ZL + Z0). If ZL = Z0, the numerator is zero and Γ = 0, so there’s no reflected wave. In this case the system is a perfect match, the standing-wave ratio is 1, and all power is delivered to the load.

Others don’t fit because a perfectly mismatched line would reflect energy back (not zero), and whether a source is active doesn’t determine Γ—the relationship between ZL and Z0 does.