In this paper, we present a class of cascaded nonlinear models for complex-valued system identification, aimed at baseband modeling of nonlinear radio systems. The proposed models consist of serially connected elementary linear and nonlinear blocks, with the nonlinear blocks implemented as uniform spline-interpolated look-up tables (LUT) and the linear blocks as FIR filters. Wiener, Hammerstein, and Wiener-Hammerstein models are built, and simple but efficient gradient based adaptive learning rules are derived for all the models. This approach leads to remarkably simple solutions in terms of computational complexity, making the techniques suitable for real-time implementation. The proposed methods are then applied to full-duplex self-interference cancellation and digital predistortion in various real-life scenarios. First, evaluations with measured data from an in-band full-duplex prototype working at 2.4 GHz ISM band show that the algorithms are capable of obtaining similar cancellation performance as existing state-of-the-art solutions, regardless of the clearly reduced complexity. Second, a mmW active antenna array working at 28 GHz center frequency is digitally predistorted with the proposed solutions. The unwanted emissions and nonlinear distortion are suppressed to similar levels as with other state-of-the art solutions, and the corresponding linearity specifications are fulfilled in all cases, while the processing complexity is again drastically reduced.

中文翻译：

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复杂非线性系统的级联样条模型：方法和应用

在本文中，我们提出了一类用于复值系统识别的级联非线性模型，旨在对非线性无线电系统进行基带建模。所提出的模型由串联连接的基本线性和非线性块组成，非线性块实现为均匀样条插值查找表 (LUT)，线性块实现为 FIR 滤波器。构建了 Wiener、Hammerstein 和 Wiener-Hammerstein 模型，并为所有模型导出了简单但有效的基于梯度的自适应学习规则。这种方法在计算复杂性方面产生了非常简单的解决方案，使这些技术适合实时实现。然后将所提出的方法应用于各种现实生活场景中的全双工自干扰消除和数字预失真。第一的，对工作在 2.4 GHz ISM 频段的带内全双工原型的测量数据进行的评估表明，这些算法能够获得与现有最先进解决方案类似的消除性能，而无需考虑明显降低的复杂性。其次，工作在 28 GHz 中心频率的 mmW 有源天线阵列使用所提出的解决方案进行数字预失真。不需要的发射和非线性失真被抑制到与其他最先进的解决方案相似的水平，并且在所有情况下都满足相应的线性规范，同时处理复杂性再次大幅降低。尽管明显降低了复杂性。其次，工作在 28 GHz 中心频率的 mmW 有源天线阵列使用所提出的解决方案进行数字预失真。不需要的发射和非线性失真被抑制到与其他最先进的解决方案相似的水平，并且在所有情况下都满足相应的线性规范，同时处理复杂性再次大幅降低。尽管明显降低了复杂性。其次，工作在 28 GHz 中心频率的 mmW 有源天线阵列使用所提出的解决方案进行数字预失真。不需要的发射和非线性失真被抑制到与其他最先进的解决方案相似的水平，并且在所有情况下都满足相应的线性规范，同时处理复杂性再次大幅降低。