Impedance Matching Calculator
Calculate impedance matching parameters including reflection coefficient, VSWR, and power transfer. Determine how well source and load impedances match.
How to Use This Calculator
- Enter the source impedance in ohms (the impedance of the signal source).
- Enter the load impedance in ohms (the impedance of the device receiving the signal).
- The calculator displays reflection coefficient, VSWR, power transfer, and mismatch loss.
- Use this to evaluate impedance matching, design matching networks, or troubleshoot signal issues.
Impedance Matching Formulas
Impedance matching parameters are calculated from source and load impedances:
VSWR = (1 + |Γ|) / (1 - |Γ|)
Power Transfer = 1 - |Γ|²
Mismatch Loss (dB) = -10 × log₁₀(Power Transfer)
Example: Source = 50Ω, Load = 75Ω: Γ = |(75-50)/(75+50)| = 0.2. VSWR = (1+0.2)/(1-0.2) = 1.5:1. Power transfer = 1 - 0.04 = 96%. Mismatch loss = 0.18 dB.
Full Description
Impedance matching is crucial for efficient power transfer and signal integrity in RF and analog circuits. When source, transmission line, and load impedances match, maximum power is transferred and signal reflections are minimized. Mismatched impedances cause reflections that create standing waves, reduce power transfer, and can damage equipment.
The reflection coefficient (Γ) quantifies how much signal is reflected. A perfect match (Γ = 0) means no reflections. VSWR (Voltage Standing Wave Ratio) is another common measure—VSWR = 1:1 means perfect match, while higher values indicate worse matching. Power transfer shows what percentage of power reaches the load, while mismatch loss shows the power lost due to reflections (in dB).
This calculator helps you evaluate impedance matching. Enter source and load impedances, and it calculates reflection coefficient, VSWR, power transfer, and mismatch loss. Use it when designing RF circuits, evaluating antenna matching, troubleshooting signal issues, or understanding how impedance affects power transfer. Proper impedance matching is essential for efficient and reliable signal transmission.
Frequently Asked Questions
What is impedance matching?
Impedance matching ensures that source, transmission line, and load impedances are equal. This maximizes power transfer and minimizes signal reflections. Mismatched impedances cause reflections, standing waves, and power loss.
What is VSWR?
VSWR (Voltage Standing Wave Ratio) measures impedance mismatch. VSWR = 1:1 means perfect match (no reflections). Higher VSWR (like 2:1, 3:1) indicates worse matching. VSWR = (1 + |Γ|) / (1 - |Γ|), where Γ is the reflection coefficient.
What is a good VSWR?
VSWR < 1.5:1 is excellent (very good match). VSWR < 2:1 is good (acceptable for most applications). VSWR < 3:1 is acceptable (some loss, but usable). VSWR > 3:1 indicates significant mismatch and may cause problems.
How do I match impedances?
Common methods: Use impedance matching networks (L-networks, Pi-networks, T-networks), transformers, transmission line transformers, or stubs. The method depends on frequency, impedance values, and application. For 50Ω to 75Ω mismatch, use a matching network or transformer.