Research On 8mm Miniaturization Radiation Sources Based On Carbon Nanotube Cold Cathode

Traditional vacuum microwave electronic devices use hot cathode as the electron source,the structure is complex,and need for high temperature heating,so the application of the device is subject to many constraints.Cold cathode field emission need no heating,work at room temperature,start fast,and structure simple.By designing a specific electron gun structure,the current emitted from the surface of the emitter can be premodulated.Carbon nanotubes have excellent field emission properties and can be used as field emission cold cathode material.Therefore,in this paper,carbon nanotubes(CNTs)are used as the field emission electron source,and a theoretical model of 8mm microwave radiation source is proposed.The main research work of this paper is as follows:Based on the field emission mechanism of carbon nanotubes and the classical F-N formula,the electron injecting principle of cold cathode electron gun is obtained,and an electron gun model for 8mm carbon nanotube microwave radiation source is constructed.The size and depth of the modulation current of the electron gun are calculated in the electromagnetic simulation software CST.Changing the cathode voltage to observe the effect of voltage changes on the current size and current modulation depth.The single-cycle model of the disk loaded waveguide is constructed.The dispersion characteristics,characteristic impedance,quality factor and resonant frequency of the periodic structure of the disk loaded waveguide are calculated by using the periodic boundary method in the electromagnetic simulation software CST,and study the effects of different structural parameters on the dispersion characteristics,characteristic impedance,quality factor and resonant frequency.A number of patterns are calculated to get the electric field distribution and electric field strength of each mode,and the resonant frequency,quality factor and characteristic impedance of each mode are obtained.Find out the suitable mode of work.First,calculate the single-cycle length of the disk-waveguide and get the corresponding phase velocity.According to the previous structural parameters on the impact of high-frequency characteristics to determine the structure of the disk waveguide parameter values.Under the same high-frequency structure conditions,DC emission and pre-modulation electron injection are used to simulate,and obtain the output power of each other.Through the comparison of the two find that using the pre-modulation of electronic injection as the source,the radiation source not only starting fast,but also the starting current is smaller than the starting current under the DC emission conditions.