Research On Key Technologies Of Microstrip Meander-line Planar Traveling Wave Tube

Travelling wave tube(TWT)is a very important type of microwave vacuum devices,which has the advantages of wide operating frequency band,large output power and high gain.It's important in intersatellite communication,radar,electronic countermeasures,and also has a good application prospect in terahertz imaging,astronomical research,biological medicine and other fields.With the continuous progress of modern processing technology,TWT is also developing toward miniaturization and integration.Microstrip meander-line TWT is a kind of TWT with great application potential.This paper mainly studies the key problems of microstrip TWT,which is mainly divided into the following three parts:(1)Study on the slow wave structure(SWS)of a three-dimensional microstrip meander-line.To solve the problems of small interaction impedance and charge accumulation in microstrip meander-line TWT,a three-dimensional microstrip meander-line slow-wave structure is proposed.The simulation software is used to study its high frequency characteristics,and the specific parameters working in the W band are designed,and the matching input and output devices are designed.The PIC simulation study shows that when the input power is 0.1W,and the synchronous voltage is 6.7k V and the current is 0.1A,the 3-D microstrip meander-line TWT can obtain the output power of more than 15 W in the 76GHz-94 GHz frequency band,and the corresponding gain is more than 22 d B.The simulation results are compared with those of the conventional N-type microstrip meander-line TWT,and the results show that the3-D microstrip meander-line TWT has certain advantages.(2)Study on a novel N-type microstrip meander-line slow wave structure.From the point of view of convenient machining and improving performance,a new structure is proposed,which has the advantages of large interaction impedance.The high frequency characteristics are studied,and the transmission simulation is optimized.Then the PIC simulation is performed,under the condition of input power of 0.1W,synchronous voltage of 6k V and current of 0.14 A,the new N-type microstrip meander-line TWT can obtain output power of more than 26 W and corresponding gain of more than 24 d B in the 56GHz-62 GHz frequency band.Compared with the simulation results of traditional N-type microstrip meander-line TWT,the new structure has some advantages.Finally,the new structure is processed and cold-measured,and the experimental results are in good agreement with the simulation results,and the transmission effect is good.(3)Research and Design of PCM Focusing System.Firstly,the theory of PCM focusing system is introduced,and then a matching PCM(Period Cusped Magnetic)focusing system is designed for the designed 3-D microstrip meander-line TWT.The magnetostatic simulation and particle simulation and optimization are carried out.When the peak Magnetic field of the PCM focusing system is 0.27 T and the Period is 4mm,the transmission rate of the electron beam reaches 99%.In addition,a scheme of external compensating magnetic field of PCM focusing system is proposed to avoid the possible cathode tilt in the assembly process of electron gun,and the simulation is carried out.The simulation results show that this scheme is effective.