Types of Spurious Emissions
| Type | Frequency | Source |
|---|---|---|
| 2nd harmonic | 2×f_TX | PA nonlinearity |
| 3rd harmonic | 3×f_TX | PA nonlinearity (usually weaker than 2nd) |
| LO leakage | f_LO | Mixer LO-to-RF port isolation |
| IM products | mf₁±nf₂ | Multiple signals in nonlinear stage |
| Reference spurs | f_carrier ± N×f_ref | PLL frequency reference feed-through |
Regulatory Limits
FCC Part 15.247 (WiFi 2.4 GHz, USA): TX: +30 dBm EIRP maximum Spurious: <−41.3 dBm EIRP at >1 MHz from carrier Harmonics: same −41.3 dBm limit ETSI EN 300 328 (WiFi EU): TX: +20 dBm EIRP Spurious: <−30 dBm at any out-of-band frequency Required harmonic filter attenuation: At +20 dBm TX, H₂ = −20 dBc raw: H₂ raw = 0 dBm at 4.8 GHz FCC limit: −41.3 dBm → need 41.3 dB filter rejection at 4.8 GHz
Measuring Spurs with RF View
For harmonic rejection analysis: load TX filter .s2p → S21 view → place markers at 2f₀ and 3f₀ → read rejection values → verify compliance against calculated limit.
RF View Spurious Analysis: Load TX filter .s2p, extend analysis to harmonic frequencies, use single markers for rejection measurement at 2f₀ and 3f₀. Verify FCC/ETSI compliance margin. Free on Android.