The reflection coefficient is a function of what?

The reflection coefficient is a function of what?

• A. The load and line impedances, indicating how much power is reflected due to impedance mismatch
• B. Antenna gain and radiation pattern
• C. Cable length and dielectric constant
• D. Operating frequency and thermal noise

Answer: (A)

The reflection coefficient measures how much of the incident power on a transmission line is reflected back because the load impedance does not match the line’s characteristic impedance. It depends on the line’s characteristic impedance Z0 and the load impedance ZL, through the relation Gamma = (ZL − Z0)/(ZL + Z0). When ZL equals Z0, Gamma is zero and all the power is delivered with no reflection. A mismatch yields a nonzero Gamma, indicating reflected power and a higher standing-wave ratio. This is why the best answer is about the load and line impedances—the two impedances determine the degree of mismatch and thus how much power gets reflected. Antenna gain or radiation pattern describe the radiated field after power is delivered, not how much is reflected on the feed line. Cable length and dielectric constant influence the line’s impedance and propagation characteristics, but the magnitude of the reflection is set by the mismatch between Z0 and ZL (length mainly affects phase of the reflected wave). Operating frequency and thermal noise relate to other aspects of the system and don’t define the reflection magnitude on the line.

The reflection coefficient measures how much of the incident power on a transmission line is reflected back because the load impedance does not match the line’s characteristic impedance. It depends on the line’s characteristic impedance Z0 and the load impedance ZL, through the relation Gamma = (ZL − Z0)/(ZL + Z0). When ZL equals Z0, Gamma is zero and all the power is delivered with no reflection. A mismatch yields a nonzero Gamma, indicating reflected power and a higher standing-wave ratio.

This is why the best answer is about the load and line impedances—the two impedances determine the degree of mismatch and thus how much power gets reflected. Antenna gain or radiation pattern describe the radiated field after power is delivered, not how much is reflected on the feed line. Cable length and dielectric constant influence the line’s impedance and propagation characteristics, but the magnitude of the reflection is set by the mismatch between Z0 and ZL (length mainly affects phase of the reflected wave). Operating frequency and thermal noise relate to other aspects of the system and don’t define the reflection magnitude on the line.