How do I calculate the spurious free dynamic range of a receiver chain?

Spurious-free dynamic range (SFDR) is the range of signal levels from the noise floor to the level where the largest spurious signal (typically the third-order intermodulation product, IM3) equals the noise floor. It defines the usable dynamic range of a receiver: (1) Formula: SFDR (dB) = (2/3) × (IIP3 - N_floor). Where IIP3 = input-referred third-order intercept point (dBm). N_floor = noise floor of the receiver (dBm) = -174 + NF + 10×log10(B). B = noise bandwidth (Hz), NF = noise figure (dB). (2) Example: receiver with NF = 6 dB, IIP3 = -10 dBm, bandwidth = 10 MHz. Noise floor: N = -174 + 6 + 10×log10(10e6) = -174 + 6 + 70 = -98 dBm. SFDR = (2/3) × (-10 - (-98)) = (2/3) × 88 = 58.7 dB. This means: the receiver can detect signals from -98 dBm (noise floor) down to -39.3 dBm (where IM3 products would equal the noise floor). The SFDR is 58.7 dB. (3) Why 2/3 factor: the IM3 product level rises 3 dB for every 1 dB increase in input signal (third-order product grows at 3× the input rate). So the IM3 level catches up to the noise floor from below at a rate of 2 dB per 1 dB of input signal increase. The point where IM3 = noise floor is 2/3 of the way from noise floor to IP3. (4) SFDR vs bandwidth: SFDR depends on the noise bandwidth. Narrower bandwidths have lower noise floors, increasing the SFDR. SFDR for 1 Hz bandwidth: multiply the formula by the bandwidth factor. Normalized SFDR (per Hz): SFDR_1Hz = (2/3) × (IIP3 + 174 - NF). This is bandwidth-independent and useful for comparing receivers.