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RF Receiver Chain Designer

Build your RX chain stage by stage. Computes cascaded NF, IIP3, P1dB, sensitivity, dynamic range and SFDR using the Friis formulas. Per-stage signal levels, SNR and compression warnings tell you exactly where your chain is struggling.

// System Parameters

Input Signal Power (P_in)

dBm

Noise Bandwidth (B)

Required SNR (demod)

Reference Temperature

// Chain Stages — drag order matters. IIP3 and P1dB are input-referred. Leave blank if not applicable.

Stage Name Type NF (dB) Gain (dB) IIP3 (dBm) P1dB (dBm)

⚠ Please check inputs — NF and Gain must be numbers for all stages.

// Signal Flow — Power at Each Node

// System Performance

Per-Stage Breakdown

Stage	Type	NF contrib	Cum. NF	Cum. Gain	IIP3 contrib	Signal @ out	SNR @ out	Status

Friis — Noise: F_tot = F₁ + (F₂−1)/G₁ + (F₃−1)/(G₁G₂) + … · NF = 10log(F_tot)
Friis — Linearity: 1/IIP3_tot = 1/IIP3₁ + G₁/IIP3₂ + G₁G₂/IIP3₃ + … (linear power)
Sensitivity: S_min = −174 + NF + 10log(B) + SNR_req dBm
Dynamic Range: DR = IIP3_sys − S_min (approx) · SFDR = ⅔·(IIP3_sys − noise_floor)
Note: Later stages dominate IIP3 (opposite to NF where first stage dominates).

About the RF Receiver Chain Designer

Every RF receiver is a cascade of components â€” LNA, bandpass filter, mixer, IF amplifier, IF filter â€” each adding noise and each potentially compressing the signal. Understanding the cascade performance before building is essential. This tool computes the complete receiver budget using the Friis formulas for noise and linearity.

Cascaded Noise Figure â€” Friis Formula

The total noise figure of a cascade is dominated by the first stage. The Friis formula states: F_total = F1 + (F2-1)/G1 + (F3-1)/(G1*G2) + ... A high-gain, low-noise LNA at the front suppresses the noise contribution of every subsequent stage. This is why LNA placement immediately after the antenna is critical â€” every decibel of loss before the LNA directly adds to the system noise figure.

Cascaded IIP3 â€” Linearity Budget

Unlike noise figure where early stages dominate, IIP3 is dominated by later stages that receive a larger signal. The cascaded IIP3 is calculated as: 1/IIP3_total = 1/IIP3_1 + G1/IIP3_2 + G1*G2/IIP3_3 + ... High gain before a nonlinear stage (like a mixer) reduces the system IIP3 significantly. The art of receiver design is balancing the gain distribution to meet both NF and IIP3 requirements simultaneously.

Sensitivity and Dynamic Range

Receiver sensitivity is the minimum detectable signal: S_min = -174 + NF + 10*log(B) + SNR_min dBm. Dynamic range is the difference between the maximum receivable signal (before compression) and the sensitivity. SFDR (Spurious Free Dynamic Range) accounts for the intermodulation products that limit usable range in the presence of blockers.