This letter reports a new theoretical analysis of third-order intermodulation (IM3) reduction in nonlinear communication amplifiers by signal injection. On the basis of well-known Volterra series analysis, we put forward a general model that can analyze both the qualitative and quantitative effects of injected signal parameters on output IM3s, which previous literatures failed to achieve. Our theory can directly calculate the optimal amplitude and phase of single injected signal and points out the duality for some dual-signal injections which can help reduce their parameter scanning complexity from 4-D to 2-D. These conclusions are in good agreement with the simulation of two traveling wave tube (TWT) amplifiers by 3-D-FDTD-PIC code and CST and MTSS. Our work proposes an original analysis about how to adjust injected external signals to obtain best IM3 cancellation in communication systems, and boosts the research efficiency for new signal injection techniques from a novel perspective.

中文翻译：

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通过信号注入抑制三阶互调的理论和时域仿真

这封信报告了通过信号注入减少非线性通信放大器中的三阶互调 (IM3) 的新理论分析。在著名的 Volterra 级数分析的基础上，我们提出了一个通用模型，可以分析注入信号参数对输出 IM3 的定性和定量影响，这是以前的文献未能实现的。我们的理论可以直接计算单注入信号的最佳幅度和相位，并指出一些双信号注入的对偶性，这有助于将它们的参数扫描复杂度从 4-D 降低到 2-D。这些结论与通过 3-D-FDTD-PIC 代码以及 CST 和 MTSS 对两个行波管 (TWT) 放大器进行的仿真非常吻合。