VSWR and Return Loss

VSWR (Voltage Standing Wave Ratio) is an indicator of signal return loss characteristics in coaxial cables. As mentioned previously, VSWR is the ratio of the maximum voltage (Vmax) to the minimum voltage (Vmin) of a standing wave.

The Relationship Between VSWR and Return Loss
The Vmax and Vmin of the standing wave can be expressed as follows:

Therefore, VSWR can also be expressed as:

From the above equation, VSWR approaches 1 as the reflection wave (VR) decreases, and becomes infinite when there is total return loss (VF = VR). From the above equation, VSWR approaches 1 as the reflected wave (VR) becomes smaller, and becomes ∞ in the case of total return loss (VF = VR).
VSWR is an important indicator in RF circuit design. Understanding VSWR enables the suppression of signal reflection and the realization of efficient transmission.