What is the intermodulation-free dynamic range and how does it differ from the blocking dynamic range?

The intermodulation-free dynamic range (IMDR or SFDR) and the blocking dynamic range (BDR) are two different measures of a receiver's ability to handle unwanted signals, addressing different interference scenarios. The intermodulation-free dynamic range (also called spur-free dynamic range, SFDR) measures the receiver's ability to detect a weak desired signal in the presence of two moderate interferers that produce a third-order intermodulation product at the desired signal frequency. The SFDR is: SFDR = (2/3) x (IIP3 - N_floor) [dB], where IIP3 is the receiver's input third-order intercept point and N_floor is the noise floor (kTB + NF). The SFDR is limited by the receiver's linearity (IIP3) and noise figure. The blocking dynamic range (BDR) measures the receiver's ability to detect a weak desired signal in the presence of a single very strong signal that desensitizes the receiver through gain compression or reciprocal mixing. The BDR is: BDR = P_blocker_max - P_sensitivity [dB], where P_blocker_max is the maximum tolerable blocker power (limited by the 1 dB compression point or the reciprocal mixing level). Key differences: SFDR involves two interferers at moderate power levels creating an in-band intermodulation product (limited by IIP3), while BDR involves a single very strong interferer causing compression or reciprocal mixing (limited by P1dB or LO phase noise). SFDR is proportional to (2/3) x IIP3 and is typically 60-80 dB. BDR is proportional to P1dB and is typically 80-120 dB (larger than SFDR because the compression point is higher than the IIM3 threshold). SFDR is improved by increasing IIP3 (more linear components). BDR is improved by increasing P1dB (more robust components) and reducing LO phase noise.