Passive Intermodulation in real 4G/5G network setup

This letter presents an effective digital passive intermodulation (PIM) cancellation technique for multi-band multiple-input multiple-output frequency-division duplexing radios for 5G and beyond. We begin by introducing a universal PIM signal model for multi-band radios with an arbitrary number of transmit--receive antennas, which enables the calculation of basis functions at all intermodulation frequencies. After establishing this signal model, a comparative analysis of state-of-the-art behavioral models is conducted in the context of PIM modeling. More specifically, the computational complexity and the modeling accuracy of the memory polynomial (MP), the generalized MP, and the Volterra models is discussed and evaluated through true radio frequency measurements in commercial 5G new radio single- and dual-band radio units. The presented results highlight the limitations of each signal model, and also provide new insight into PIM effects and potential of digital PIM cancellation.