Complete RF Receive Chain
An RF receive chain converts the weak RF signal from the antenna to a baseband signal suitable for demodulation. Each stage contributes gain (or loss) and noise, determined by the S-parameter characteristics and noise figure of each component.
System-Level Analysis Method
Chain: ANT → Filter₁ → LNA → Filter₂ → Mixer → IF Amp System S21 (gain): G_sys = G₁ + G₂ + G₃ + ... [dB, additive] System NF: Friis formula → dominated by first stages System IIP3: dominated by last high-gain stages Sensitivity = −174 + NF_sys + 10·log₁₀(BW) + SNR_min [dBm]
Example Chain Analysis (LTE Band 8)
| Stage | Component | G (dB) | NF (dB) |
|---|---|---|---|
| 1 | RF switch + duplexer | −2.5 | 2.5 |
| 2 | BPF | −1.5 | 1.5 |
| 3 | LNA (SiGe) | +18 | 1.8 |
| 4 | Trace/connector | −0.5 | 0.5 |
| 5 | Mixer | −8 | 8.0 |
NF_sys ≈ 2.5 + 1.5 + 1.8×(1/0.562)/1 + ... ≈ 6.1 dB Sensitivity @5MHz BW: −174 + 6.1 + 67 + (−1) = −101.9 dBm
RF View NF Cascade: Enter chain NF and gain values in RF View's NF Cascade Calculator to compute system NF and sensitivity instantly. Free on Android.