Parallel Multi-beam Terahertz Radiation Source Based On The Metamaterial Structure

Terahertz technology has attracted more and more attention for its high application potential in wireless communication,safety inspection,environmental science and drug detection.However,due to the lack of high-power,low-cost and portable terahertz radiation sources,the development of terahertz technology is slowing down.The electromagnetic responses produced by most natural materials in the terahertz band are not strong enough,so people have been researching suitable artificial materials to design terahertz radiation sources.Metamaterials refer to a kind of artificially designed materials with superconventional physical properties that are difficult to find in natural materials.By appropriately adjusting its subwavelength structure,the working frequency of metamaterials can be adjusted to terahertz band,and the metamaterial terahertz radiation sources have the advantages of miniaturization,high output power,high conversion efficiency and suitable for processing.Therefore,terahertz radiation sources based on metamaterial structure have broad prospects.Compared with the single electron beam,the advantage of parallel multi-beam is that it can effectively reduce the emission current density of the electron gun.Low current density can reduce the cost and volume of the electron gun,the collector and the slowwave structure,and increase their working life.Moreover,the multi-beam is beneficial to enhance the beam-wave interaction and increase the output power.The main research content of this paper is parallel multi-beam terahertz radiation source based on the metamaterial structure.Firstly,the metamaterials working in terahertz band are designed.Then the structure is applied to the slow-wave structure of the terahertz radiation source.Finally the terahertz radiation source is designed combined with the parallel multi-beam technology.The main work of this paper is as follows:1.The development process and research status of terahertz band,terahertz devices,metamaterial vacuum electronic devices and multi-beam devices are briefly introduced,which is also the research background of this paper.2.The basic theory of metamaterials is studied,including the realization of negative effective permittivity and negative effective permeability of metamaterials and the propagation characteristics of electromagnetic waves in metamaterials,which lays a theoretical foundation for the following research.3.Three kinds of metamaterial structures with frequencies ranging from 200 GHz to310GHz are designed,their effective permittivity and effective permeability are calculated,and their high frequency characteristics are analyzed.In this range,the effective permittivity and effective permeability of the metamaterial slow-wave structure are less than zero,and the interaction impedance is relatively high.4.A metamaterial structure is selected as the high frequency structure of the backward wave oscillator,and the matching rectangular waveguide coupling structure,matched load and antenna length are designed.The beam-wave interaction characteristics of columnar beam and sheet beam in single-electron beam and multi-beam cases are analyzed respectively.The tuning frequency range of the backward wave oscillator with the three columnar electron beams is 20 GHz.When the voltage is 35 k V,the total current is 40 m A,and the magnetic field is 0.5T,the output power is 77.12 W,and the conversion efficiency is 5.52%.A metamaterial extended interaction oscillator is designed using this high frequency structure.When the voltage is 8k V,the total current of three columnar electron beams is 30 m A,and the magnetic field is 0.5T,the output power is 16.25 W.The metamaterials designed in this paper have a simple structure,and their metal plate is easy to be integrated by micro-machining technology,and the structure size of the metamaterial slow-wave structure is ?/4,which is helpful to the miniaturization of the radiation source.The parallel multi-beam terahertz radiation sources,which has excellent performance,can reduce the current density of the single beam and obtain higher output power under the same total current condition.