RF Receiver Characterization and Spurious-Free Dynamic Range Enhancement for PIM/Weakly Nonlinear Device Measurements

This paper proposes a technique to characterize and postcompensate for the dynamic nonlinearity exhibited by radio frequency (RF) receivers employed in passive intermodulation (PIM) and weakly nonlinear devices characterization (low gain compression of the order of 0.1 dB). The proposed technique begins by accurately characterizing the RF receiver’s nonlinearity using two-tone and multitone stimuli with swept frequency spacing and input power level. Then, a pruned Volterra series-based postcompensation model is devised to mitigate the dynamic weak nonlinear distortions exhibited by the receiver. The technique was validated in two steps. First, the capacity of the postcompensation technique to separate the RF receiver’s intermodulation from the device under test’s intermodulation was assessed. Second, its capacity to postcompensate for the dynamic nonlinearity exhibited by the RF receiver and to enhance its spurious-free dynamic range (SFDR) was assessed using digitally modulated stimuli. The application of the proposed technique reduced the third-order intermodulation (IMD 3 ) of the RF receiver by an average of 10 dB. This technique can significantly relax the requirements on duplexers and tone injection techniques used to enhance the accuracy of PIM measurements. Furthermore, the receiver’s SFDR was extended by up to 15 dB.