S11 Targets by Application
| Application | Minimum S11 | Target S11 | VSWR |
|---|---|---|---|
| Mobile phone (smartphone) | −10 dB | −12 to −15 dB | <1.92, target <1.67 |
| Base station antenna | −14 dB | −16 to −20 dB | <1.50, target <1.37 |
| WiFi access point | −10 dB across band | −14 dB | <2.0 |
| IoT sensor (LoRa, BLE) | −10 dB at f₀ | −12 dB | <1.92 |
| GPS patch antenna | −10 dB at 1575 MHz | −15 dB | <1.92 |
| mmWave 5G (28 GHz) | −10 dB across 400 MHz BW | −12 to −15 dB | <2.0 |
What Happens at Different S11 Levels
S11 = −6 dB (VSWR = 3:1):
25% power reflected → 1.25 dB extra loss
PA sees highly variable load → instability risk
❌ FAIL for most applications
S11 = −10 dB (VSWR = 1.92:1):
10% power reflected → 0.46 dB extra loss
✓ Minimum acceptable for most consumer devices
S11 = −14 dB (VSWR = 1.5:1):
4% power reflected → 0.18 dB loss
✓ Good match for professional applications
S11 = −20 dB (VSWR = 1.22:1):
1% power reflected → 0.04 dB loss
✓ Excellent — use for precision instruments
S11 Must Cover the Entire Band
A single good S11 value at one frequency isn't enough. The S11 must stay below the threshold across the ENTIRE operating band. For LTE Band 3 (1805–1880 MHz): S11 must be <−10 dB at every frequency from 1805 to 1880 MHz. A narrowband antenna with S11=−25 dB at 1843 MHz but S11=−4 dB at 1805 MHz fails the specification.
How to Improve a Poor S11
- Load the antenna .s1p file into RF View
- View S11 on Smith chart — identify whether it's inductive or capacitive
- Use Auto Match to design a matching network
- Verify matched S11 <−10 dB across the full operating band
RF View Antenna Analysis: Load any antenna .s1p file. View S11 vs frequency, VSWR, and Smith chart. BW Marker reads the −10 dB bandwidth. Auto Match designs the matching network. Free on Android.