Reflection Coefficient Calculator

Reflection Coefficient Calculator. The Reflection Coefficient Calculator measures how much of an electrical signal bounces back when it hits a mismatched load on a transmission line — a critical check in RF, antenna, and microwave circuit design. Enter your Characteristic Impedance (Z₀) and the real and imaginary parts of your Load Impedance to get the Reflection Coefficient Magnitude |Γ| and Phase. Secondary outputs include VSWR and Return Loss in dB. Also try the use the Mixer Spur Calculator.

Reflection Coefficient Calculator inputs
Ω

Impedance of the transmission line

Ω

Real part of load impedance

Ω

Imaginary part of load impedance (reactive component)

Results

Reflection Coefficient Magnitude |Γ|

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Reflection Coefficient Phase

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VSWR

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Return Loss

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What is a reflection coefficient?

The reflection coefficient (Γ) is the ratio of the reflected wave amplitude to the incident wave amplitude at a point of impedance discontinuity. It ranges from -1 to +1 and indicates how much of the signal is reflected back. See also our calculate Directional Coupler.

How is reflection coefficient related to VSWR?

VSWR (Voltage Standing Wave Ratio) is calculated as (1 + |Γ|) / (1 - |Γ|). A perfect match has Γ = 0 and VSWR = 1, while complete reflection has |Γ| = 1 and VSWR = ∞.

What does return loss mean in RF applications?

Return loss is the negative of the reflection coefficient expressed in decibels: RL = -20 × log₁₀(|Γ|). Higher return loss values indicate better impedance matching and less reflected power.

Why is 50 ohms commonly used as characteristic impedance?

50 ohms is a standard characteristic impedance that provides a good balance between power handling capability and signal loss for coaxial cables and RF systems.

What happens when load impedance equals characteristic impedance?

When ZL = Z₀, there is perfect impedance matching. The reflection coefficient equals zero, VSWR equals 1, and return loss approaches infinity - meaning no power is reflected.

How do you interpret the phase of the reflection coefficient?

The phase angle indicates the phase shift of the reflected wave relative to the incident wave. It depends on both the magnitude and nature (capacitive or inductive) of the impedance mismatch.

What is considered acceptable VSWR in RF systems?

Generally, VSWR < 2:1 is considered good (return loss > 9.5 dB), while VSWR < 1.5:1 is excellent (return loss > 14 dB). The acceptable level depends on the specific application requirements. You might also find our Smith Chart Calculator useful.