S-Parameter Conversion Form
Choose one known RF match metric, enter its value, define angle and reference impedance, then convert it into several related engineering outputs.
Example Data Table
This sample shows how one known value expands into common RF matching metrics for quick engineering review and comparison.
| Case | Known Input | Phase | Z0 | Return Loss | VSWR | Delivered Power |
|---|---|---|---|---|---|---|
| Antenna Match | S11 = -15.00 dB | 20° | 50 Ω | 15.00 dB | 1.43 | 96.84% |
| Filter Port | VSWR = 2.00 | -35° | 50 Ω | 9.54 dB | 2.00 | 88.89% |
| LNA Input | Reflected Power = 4.00% | 15° | 75 Ω | 13.98 dB | 1.50 | 96.00% |
| Test Fixture | Mismatch Loss = 0.50 dB | 48° | 50 Ω | 8.57 dB | 2.21 | 89.12% |
Formula Used
The calculator converts every supported input into the reflection coefficient magnitude first, then derives all other RF matching quantities from that common value.
- |Γ| = 10^(S11 dB / 20)
- |Γ| = 10^(-Return Loss / 20)
- |Γ| = (VSWR - 1) / (VSWR + 1)
- |Γ| = √(Reflected Power % / 100)
- |Γ| = √(1 - 10^(-Mismatch Loss / 10))
- Return Loss = -20 log10(|Γ|)
- VSWR = (1 + |Γ|) / (1 - |Γ|)
- Reflected Power % = |Γ|² × 100
- Delivered Power % = (1 - |Γ|²) × 100
- Mismatch Loss = -10 log10(1 - |Γ|²)
- Γ = |Γ| (cos θ + j sin θ)
- ZL = Z0 × (1 + Γ) / (1 - Γ)
How to Use This Calculator
- Select the type of S-parameter related value you already know.
- Enter the value exactly as measured or reported by your instrument.
- Add the phase angle when you want complex impedance results.
- Set the reference impedance used by the system or test setup.
- Optionally add frequency, port label, and notes for export context.
- Choose decimal precision, then submit the form.
- Review the summary block placed above the form.
- Download the result set as CSV or PDF for reports.
Frequently Asked Questions
1. What does this converter actually calculate?
It converts one reflection-related input into several RF matching outputs, including return loss, VSWR, reflected power, delivered power, mismatch loss, and complex load impedance.
2. Why is return loss shown as a positive number?
Return loss is usually reported as a positive dB value because it represents how much signal is lost in the reflected wave. S11 magnitude in dB is the negative counterpart.
3. When do I need the phase angle?
You need phase when you want real and imaginary impedance values. Without phase, magnitude-based match metrics still work, but the complex impedance direction remains undefined.
4. What reference impedance should I use?
Use the impedance of your RF system, instrument, or transmission line. Fifty ohms is common, but seventy-five ohms appears often in video and cable applications.
5. Can this help with antenna matching reviews?
Yes. Engineers often start with S11 or return loss, then translate it into VSWR and delivered power to judge whether an antenna match is acceptable.
6. Why must the reflection coefficient stay below one?
For passive terminations, the reflected voltage magnitude cannot exceed the incident voltage magnitude. Values at or above one usually indicate invalid input or an unstable active condition.
7. Does frequency change the conversion formulas?
The core conversions do not change with frequency. Frequency is included so exported results keep measurement context, especially when comparing multiple bands or test points.
8. What is mismatch loss used for?
Mismatch loss estimates the power penalty caused by reflections. It is useful in gain budgets, link calculations, and system-level efficiency checks for RF chains.