| Extended interaction oscillators(EIOs)have been developed greatly in recent years due to the advantages of outstanding performance in the power,bandwidth and efficiency.Especially in the terms of the development in millimeter-wave devices,EIOs have been the subjects of great interest in many professional domains,including low altitude navigation and the airborne radar used in target seeking.In addition,high power radiation has been widely used in high data rate communication,molecular spectroscopy,biological spectroscopy,medical diagnosis,etc.The contradiction between the ever-increasing operating frequency and the size of devices restricts the development of high-power radiators.In the bands of millimeter and terahertz,the emergence of extended interaction devices overcomes the difficulty of the size reduction of traditional klystrons and enables these devices to operate in a higher frequency range.EID combines the advantages of klystron and traveling-wave tube to develop a radiation source of electric vacuum with high gain,wide bandwidth and high power.With the development of EID in higher millimeter band,dimension keeps decreasing.How to improve the high frequency structure of EID to increase the power output has become one of the research focuses of EIO.The main contents of this paper include: The development,operational principle and current situation of EID are summarized.The basic theory of EID is introduced briefly.A new type of coupling slot structure in coupled cavity has been studied.The cold-cavity characteristics of coupled cavity with different coupling slot structures are analyzed.Design and optimization of high frequency systems with different coupling slots are operated.The influence of different coupling slot structures and several important parameters on the output power are analyzed by PIC simulation.At the same time,one of the coupling slot structure is selected and applied to the EIK.The characteristics of the cold and hot cavity of the EIK are studied and analyzed.The research contents and innovation points include as the following:(1)A new type of coupling slot structure has been designed.The characteristic of cold cavity is analyzed.According to this structure,a new EIO has been designed,and its characteristic of hot cavity has been also studied.(2)Different types of coupling slots in coupling cavities have been selected,for instance,Hughes-type structure,Chodorow-type structure,single-slot type structure,chodorow-based type structure,etc.Keeping these structures in the same size to avoid other factors affecting the research.(3)EIOs based on different high frequency structure are designed according to different coupling slots.By comparing the cold parameters,such as dispersion characteristics,field distribution,interaction impedance and coupling coefficient,the differences of different coupling slot structures are preliminarily obtained.It can be inferred that which type of the coupled cavity based on coupling slot has the better output performance in PIC simulation.(4)Four types of typical coupling slot structures are selected to work as the high frequency sructures.Therefore,four EIOs based on different coupled cavities are designed.By analyzing the PIC simulation,a coupled cavity with maximum output power is obtained.Change two important parameters to study the variety of the output power.The final result shows that the EIO output power of these four structures is greater than 1.7kW,and the single-slot type structure has the maximum power output.The output power is 2.8kW and the efficiency is 18%.(5)A four-cavity EIK has been designed based on the Chodorow-type coupled cavity structure.By means of parament scanning,the optimum output power is 265.65 W,the efficiency is 2.95%,the gain is 21.55 dB,the 3dB bandwidth of this EIK is 230 MHz. |
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