Define return loss and explain its relationship to VSWR.

Define return loss and explain its relationship to VSWR.

• A. RL = -20 log10|Γ|; VSWR derived from Γ via SWR = (1+|Γ|)/(1−|Γ|).
• B. RL = 20 log10|Γ|; VSWR = (1−|Γ|)/(1+|Γ|).
• C. RL is a measure of forward power; VSWR is a measure of reflected power.
• D. RL equals VSWR; They are the same quantity.

Answer: (C)

Return loss is a measure of how much of the incident signal is reflected back from the load due to impedance mismatch. In decibels, it is defined using the magnitude of the voltage reflection coefficient Γ as RL = -20 log10|Γ|. This makes return loss a ratio between forward and reflected power: RL(dB) = 10 log10(P_forward/P_reflected) = -20 log10|Γ|. A larger return-loss value means less power is reflected and the system is better matched. VSWR, on the other hand, describes the mismatch in another form: VSWR = (1+|Γ|)/(1-|Γ|). The two are linked because |Γ| = (VSWR-1)/(VSWR+1). You can combine them to relate return loss and VSWR: RL = -20 log10[(VSWR-1)/(VSWR+1)]. So return loss is not a direct measure of forward power; it’s a logarithmic ratio of forward to reflected power. VSWR is a separate mismatch metric, both derived from the same reflection coefficient.

Return loss is a measure of how much of the incident signal is reflected back from the load due to impedance mismatch. In decibels, it is defined using the magnitude of the voltage reflection coefficient Γ as RL = -20 log10|Γ|. This makes return loss a ratio between forward and reflected power: RL(dB) = 10 log10(P_forward/P_reflected) = -20 log10|Γ|. A larger return-loss value means less power is reflected and the system is better matched.

VSWR, on the other hand, describes the mismatch in another form: VSWR = (1+|Γ|)/(1-|Γ|). The two are linked because |Γ| = (VSWR-1)/(VSWR+1). You can combine them to relate return loss and VSWR: RL = -20 log10[(VSWR-1)/(VSWR+1)].

So return loss is not a direct measure of forward power; it’s a logarithmic ratio of forward to reflected power. VSWR is a separate mismatch metric, both derived from the same reflection coefficient.