Three Touchstone Data Formats
| Format | Options Line | Data Per S-Param Pair | Best For |
|---|---|---|---|
| DB (dB + degrees) | # GHz S DB R 50 | 20·log₁₀|S|, ∠S° | Human reading, Excel plots |
| MA (mag + degrees) | # GHz S MA R 50 | |S| linear, ∠S° | Interpolation, some tools prefer this |
| RI (real + imag) | # GHz S RI R 50 | Re{S}, Im{S} | Mathematically correct interpolation, SPICE |
When to Use Each Format
- DB: Default for most VNA exports; easy to read IL and RL directly in text editor
- RI: Best for interpolation near nulls; required by some EDA tools (SPICE netlists)
- MA: Linear magnitude useful for custom processing; intermediate format
Conversion Formulas
DB → RI:
mag = 10^(dB/20)
re = mag × cos(ang × π/180)
im = mag × sin(ang × π/180)
RI → DB:
mag = √(re² + im²)
dB = 20 × log₁₀(mag)
ang = atan2(im, re) × 180/π
DB → MA:
mag = 10^(dB/20)
[ang unchanged]
RI → MA:
mag = √(re² + im²)
ang = atan2(im, re) × 180/π
Batch Conversion in RF View
- Open RF View → SNP Converter tab → Format Change
- Select source files (one or many)
- Choose target format: DB, MA, or RI
- Tap Convert → RF View applies correct RI-domain conversion for all files
- Verify: load original + converted on same chart → traces must coincide exactly
Common Conversion Error
Never interpolate S-parameters in dB or MA format. Near a filter null, |S21| passes through zero — the dB value goes to −∞ and then comes back. Linear interpolation in dB fails catastrophically here. Always convert to RI before any interpolation or mathematical operations.
RF View Conversion: RF View uses correct RI-domain conversion internally for all format changes, interpolations, and resampling. You get accurate results without worrying about the math. Free on Android.