The traveling-wave tube (TWT), also known as the traveling-wave amplifier (TWA) or traveling-wave tube amplifier (TWTA), is a widely used amplifier in satellite communications and radar. An electromagnetic signal is inputted on one end of the device and is amplified over a distance until it is extracted downstream at the output. The physics behind this spatial amplification of an electromagnetic wave is predicated on the interaction of a linear DC electron beam with the surrounding circuit structure. Pierce, known as the ‘father of communications satellites,’ was the first to formulate the theory for this beam-circuit interaction, the basis of which has since been used to model other vacuum electronic devices such as free-electron lasers, gyrotrons, and Smith-Purcell radiators, just to name a few. In this paper, the traditional Pierce theory will first be briefly reviewed; the classic Pierce theory will then be extended in several directions: harmonic generation and the effect of high beam current on both the beam mode and circuit mode as well as ‘discrete effects’, giving a brief tutorial of recent theories of TWTs.

行波管（TWT）又称行波放大器（TWA）或行波管放大器（TWTA），是卫星通信和雷达中广泛使用的放大器。电磁信号在设备的一端输入，并在一定距离内放大，直到在输出端向下游提取。这种电磁波空间放大背后的物理原理是基于线性直流电子束与周围电路结构的相互作用。被称为“通信卫星之父”的皮尔斯是第一个为这种光束-电路相互作用制定理论的人，该理论的基础已被用于模拟其他真空电子设备，如自由电子激光器、陀螺仪和Smith-Purcell 散热器，仅举几例。在本文中，审查; 经典理论皮尔斯然后将在几个方向进行扩展：谐波产生和高束电流的同时在光束模式和电路模式以及“离散效应”的影响，给予简要教程最近行波管的理论。