Research On Extended Interaction Device Based On Novel Cathodes

One of the key technologies to realize millimeter wave and terahertz communication and application is to develop millimeter wave and terahertz wave radiation sources,and power source devices are one of the core components of communication equipment.In the millimeter wave and terahertz frequency bands,vacuum electronic devices have irreplaceable advantages in achieving high power.Traditional millimeter-wave and terahertz vacuum radiation source devices mainly use hot cathodes as electron sources.The disadvantages of hot cathode vacuum electronic devices are:low emission current density;cathodes need to be heated by thermal elements and cannot work at room temperature;cathode preheating requires a certain amount The length of time can not meet the needs of immediacy.When traditional vacuum electronic devices develop towards millimeter wave and terahertz frequency bands,they face a series of difficulties and challenges due to the co-transition effect of device structure size and frequency.The extended interaction device is a special type of vacuum electronic device that combines the advantages of traveling wave tube and klystron.It has the advantages of small size,compact structure,high power,etc.,and is suitable for working in millimeter wave and terahertz frequency bands.In order to overcome the shortcomings of hot cathodes and develop compact millimeter wave and terahertz vacuum radiation source devices,this dissertation proposes to use a new type of cathode as an electron source to develop millimeter wave and terahertz extended interaction devices,respectively,to expand the interaction of carbon nanotube cathodes.The oscillator and the pseudo-spark cathode extended interaction oscillator have carried out related theoretical and experimental researches.This dissertation presents a theoretical analysis and simulation study of the pre-modulation mechanism of field emission from carbon nanotube cathodes.The high-frequency electric field component of the microwave signal is used to directly modulate the field emission process of the cold cathode,and the field emission pre-modulation mechanism is verified by simulation.The structural characteristics and basic theory of the multi-gap resonant cavity of the extended interaction circuit are introduced and analyzed.The influence of the structural parameters of the multi-gap resonant cavity on the high-frequency characteristics is investigated,and an extended interaction oscillator operating in the Ka band is designed.The frequency locking of the extended interaction oscillator has been achieved by using a modulated electron beam to excite the Ka-band extended interaction oscillator.Compared with conventional oscillators,the frequency of the output signal of this new frequency-locked oscillator can be frequency locked by modulating the electron beam.In addition,the effect of the modulation depth on the output power amplitude is analyzed and the simulation results show that the power of the output signal depends on the modulation depth.As the modulation depth increases,the amplitude of the output signal increases accordingly.The use of carbon nanotube cathode pre-modulated electron injection as the electron source of vacuum electronic devices can reduce the length of linear injection devices,reduce the size and weight of the devices,etc.,which is of great significance for the development of miniaturized and integrated electronic vacuum devices.The advantages of pseudo-spark cathode electron gun,sheet electron beam and trapezoidal slow-wave structure are combined to design a high-power extended interaction oscillator operating in the terahertz band.The operating characteristics of the trapezoidal slow-wave structure under single-mode operation are analyzed theoretically,simulated,and the influence of processing errors on the circuit performance is analyzed,as well as the possible influence of terahertz high-frequency losses on the output power is analyzed,and the simulation shows that the processing accuracy needs to be less than5?m when the operating frequency is increased to 300 GHz;in the simulation,the influence of the pseudo-spark discharge process generated by the impact of plasma on the output signal frequency and power,as well as the impact of velocity dispersion brought by particle collision on the device output power and other indicators are analyzed in the simulation.The simulation shows that the introduction of plasma will lead to a 1.7%frequency shift,and the output power will be above 1 k W when the velocity dispersion is within 15%,and the output power will drop sharply when the velocity dispersion exceeds15%.In this chapter,the initial research design of the dual-frequency dual-mode terahertz extended interaction oscillator is also carried out.First,the feasibility of dual-mode operation is analyzed,and then the circuit is designed for dual-mode operation,and the simulation of the dual-mode operation extended interaction oscillator is verified by CST software,and the simulation results confirm the feasibility of the dual-frequency dual-mode terahertz extended interaction oscillator,using a pseudo-spark cathode as the electron source.The results confirm the feasibility of the dual-frequency dual-mode terahertz extended interaction oscillator with a pseudo-spark cathode as the electron source,and the power output in the order of kilowatts is obtained in both frequency bands.The design of an electron optical system based on a planar structured of carbon nanotube cold cathode is investigated,and the current emission characteristics and the flow characteristics of electron beams of the planar structured carbon nanotube cold cathode diode and triode are studied experimentally.In the experiments of the triode,the experimental test results show that the electron beam can reach the anode through the grid with almost no electron interception,and the electron beam pass rate is close to 100%.The experimental results of the triode show that the cathode emission current reaches 32m A,and the corresponding emission current density is 1.02 A/cm~2.An experimental exploration of the Ka-band extended interaction oscillator based on carbon nanotube cathodes is carried out,and the transmission characteristics of the high-frequency circuit are tested to show that the measured results of the circuit are consistent with the simulation results of the designed circuit and meet the design requirements.