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.

本信函提出了一种针对5G及其以上频段的多频段多输入多输出频分双工无线电设备的高效数字被动互调干扰（PIM）消除技术。首先，我们引入了一个适用于具有任意数量发射-接收天线的多频段无线电设备的通用PIM信号模型，该模型能够计算所有互调频率下的基函数。在建立此信号模型之后，我们对PIM建模中的最先进的行为模型进行了比较分析。具体而言，通过在商业5G新无线电单频段和双频段无线电单元中进行的真实射频测量，讨论并评估了记忆多项式（MP）、广义MP和Volterra模型在计算复杂度和建模精度方面的表现。所呈现的结果突显了每种信号模型的局限性，并就PIM效应及数字PIM消除的潜力提供了新的见解。