Why Port Mapping Matters
S-parameter files don't contain port labels — only numbers. Port 1 in a .s2p file might be "Input" or "Output" depending on who measured it. Wrong port assignment shows reversed S11/S22 and swapped S21/S12 in analysis. Always verify port assignment against the device datasheet before interpreting results.
Two-Port Verification Checklist
For a bandpass filter (Port 1=Input, Port 2=Output): ✓ S11 should dip in the passband (input is matched in passband) ✓ S22 should also dip in passband (output matched) ✓ S21 should show passband peak (signal passes through) ✓ S12 should equal S21 (reciprocal passive filter) If S11 shows passband peak (not dip): ports are probably swapped → Apply port swap in RF View Port Change tool
Three-Port Duplexer Port Convention
| Manufacturer | Port 1 | Port 2 | Port 3 |
|---|---|---|---|
| Murata (SAFFB series) | TX input | ANT port | RX output |
| TDK (DFLBA series) | ANT port | TX input | RX output |
| Qorvo (QPQ series) | TX input | ANT port | RX output |
Always check the datasheet port diagram, not just the pin number label on the component!
Identifying Correct Port Assignment
- Look at S21: should show the TX passband (not stopband) when Port 1=TX, Port 2=ANT
- Look at S31: should show very high attenuation (isolation) when Port 3=RX — TX should be blocked
- If S21 shows high attenuation at TX band: Port 1 and Port 2 are probably RX and ANT (swapped)
- Correct with RF View Port Change → define correct port assignment → save
RF View Port Mapping: Load multi-port .s3p or .s4p file, observe S-parameter patterns to verify port assignment, apply Port Change remapping if needed. Free on Android.