Electromagnetic Waves Sources

Chapter 2

Abstract

1. Introduction

15

Vacuum Microwave Sources of

Gennadiy Churyumov, Jinghui Qiu and Nannan Wang

Keywords: Cherenkov's radiation, electromagnetic field, electron beam, magnetron, TWT, frequency tuning, millimeter range, terahertz range

nologies, industry and agriculture, medicine, etc.

The applications of electromagnetic fields are of great importance in such areas as radar and navigation, communications, information and communication tech-

It is the interaction of moving charged particles (for example, electrons) with the electromagnetic field that is the cornerstone of electromagnetic phenomena. It is known that the electron moving rectilinearly and evenly with constant speed does not radiate. Moreover, the electromagnetic field, which exists around particle, moves together with particle at the same speed, and its properties remain invariable. If the nature of movement of a particle and/or its speed changes, for example, the trajectory of movement becomes curvilinear or the electron begins to move unevenly (turns to be accelerated or slowed down), the state of its own electromagnetic field also changes. As a result, there arises a free electromagnetic field, i.e., electromagnetic radiation (EMR), which has wave nature and freely advances in the environment in the form of electromagnetic wave. Depending on the existing conditions of its propagation (or accumulation of electromagnetic energy), which are

This chapter contains new simulation results concerning the physical foundations of how microwave tubes operate based on Cherenkov's mechanism of radiation (interaction with slow electromagnetic wave) and some experimental results connected with improving the output characteristics of the magnetrons (a mm band surface wave magnetron and a magnetron with two RF outputs of energy), as well as results of computer modeling of a 320-GHz band traveling wave tube (TWT). The results of analytical calculations and computer modeling, a phase bunching process in the mm band surface wave magnetron, are considered. It is shown that the process of phase focusing has two features associated with a concentration of RF wave energy close to the vanes of an anode block and higher electron hub of a space charge as compared to the classical magnetrons. The features and examples of practical application of the magnetron with two RF outputs of energy are presented. It is shown that the main advantage of the magnetrons is its extended functionalities (for example, possibility of frequency tuning including electronic tuning of a frequency from a pulse to pulse). The presented materials will be of interest not only for starting researchers but also for those who have microwave tube experience.

Electromagnetic Radiation
