Voltage Standing Wave Ratio

Calculate reflection coefficient, reflected power, and mismatch loss from VSWR.

The Voltage Standing Wave Ratio (VSWR) is a statistic used to assess the level of impedance mismatch over transmission lines in electrical and electronics systems. It measures how much signal reflection is brought on by impedance mismatches — calculated by dividing the maximum voltage along a transmission line by the minimum voltage.

VSWR is primarily used to evaluate impedance matching and signal transmission quality between linked components. It assists in locating possible problems including power inefficiency, signal loss, and electromagnetic interference brought on by reflections in transmission lines.

Understanding Voltage Standing Wave Ratio

Effects of High VSWR on Performance

A high VSWR can have several negative effects on the performance of a transmission system:

Effect	Description
Transmitter Power Amplifier Damage	Elevated voltage and current levels caused by standing waves pose a risk to the output transistors of the transmitter
Reduced Output Power	Many transmitters incorporate protection mechanisms that lower output power in response to increased SWR to prevent damage to the power amplifier
Feeder Damage	Peak currents can induce localized overheating, degrading or melting plastic components — elevated voltage may also trigger arcing
Signal Distortion	Reflected signals travel back to the source and may bounce back towards the antenna, causing delays equivalent to twice the signal's transmission duration — leading to inter-symbol interference in data transmission and ghost images in analog TV

What is Standing Wave Ratio (SWR)?

The Standing Wave Ratio (SWR) represents the relationship between the highest and lowest amplitudes of a standing wave. It describes the operational principles of impedance mismatch and its practical consequences on transmission systems.

VSWR in Antenna Systems

VSWR serves as a measure of the disparity between an antenna and the connecting feed line — also referred to as the Standing Wave Ratio (SWR). Key reference values:

VSWR Value	Interpretation
1.0	Perfect match — no reflected power
Below 2.0	Generally deemed adequate for the majority of antenna applications
Above 2.0	Indicates significant mismatch — may require corrective action
∞	Complete mismatch — total signal reflection

Applications

Antenna Systems
RF and Microwave Systems
Telecommunications
Test and Measurement Equipment
Radio and Broadcasting

About This Calculator

This online calculator determines the Voltage Standing-Wave Ratio (VSWR) and related transmission line parameters. Enter the VSWR value to find the Reflection Coefficient, Reflected Power, Return Loss, and Mismatch Loss — providing insights into transmission line efficiency and signal loss.

Formulas

$|\Gamma| = \frac{v - 1}{v + 1}$

$p = 100 \times \Gamma^2$

$d = 20 \times \log_{10}(\Gamma)$

$l = 10 \times \log_{10}(1 - \Gamma^2)$

where:

$v$ = Voltage Standing Wave Ratio (VSWR)
$\Gamma$ = Reflection Coefficient
$p$ = Reflected Power (%)
$d$ = Return Loss (dB)
$l$ = Mismatch Loss (dB)

Inputs

Voltage Standing Wave Ratio

Voltage standing wave ratio — must be ≥ 1 (1 = perfect match, ∞ = total reflection)

Results

Reflection Coefficient0.000e+0Voltage reflection coefficient (0 = no reflection, 1 = total reflection)

Reflected Power0.000e+0%Percentage of incident power reflected back

Reflected Power0.000e+0dBReturn loss in decibels (negative value — more negative = better match)

Mismatch Loss0.000e+0dBInsertion loss due to impedance mismatch in decibels (negative value)