| Travelling-wave tubes have advantages of wide bandwidth,high power,high gain,miniaturization and so on.Therefore,TWT becomes one of the most widely used microwave vacuum electronic devices.It has been widely used in industrial,scientific research and military fields.The W-band multi-channel micro-strip TWT can realize simultaneous amplification of multiple signals in a small vacuum cavity.The structure not only shows outstanding performance of multi-channel power synthesis,but also meets the requirements of modern“one-to-many”communication.This thesis mainly consists of the following research details:（1）A W-band multi-channel supported micro-strip TWT is designed.The main work includes:design the high-frequency system;Impedance matching is carried out by means of micro-strip line periodic hopping and coaxial input-output structure.In the frequency band of 81～91GHz,S11can be adjusted to be less than-15 d B,and S21can be adjusted to be between-5d B and-8 d B.The effects of input power,electron beam voltage and electron beam current on the signal amplification of the TWT are studied in detail by PIC simulation.Finally,the working bandwidth of the dual-channel supported slow-wave structure is 85～91GHz,and the stable output power of one single channel is11W at 89GHz.The gain is 16.6d B.The results of multi-frequency signal input are simulated,mainly aiming at the interference between the multiple frequency signal input.Through the analysis and comparison of PIC results and MATLAB simulation results,some expected assumptions for the realization of multi-channel structure traveling wave tube are obtained.（2）A W-band dual-channel suspended micro-strip line structure.In sequence,the slow wave structure’s high frequency characteristics are initially examined;Secondly,transmission characteristics are calculated in detail,the S-parameters are successfully adjusted to meet the impedance-matching requirement in 75-85GHz bandwidth.Finally,the optimal amplification is achieved at 79GHz,the output power is 18W,the gain is14d B,and the working frequency band is 75.5～81.5GHz.The multi-frequency and multi-phase signal input problem involved in the multi-channel structure is simulated in detail.The amplifying amplitude of the signal will be affected by the input of different phase signals.Therefore,the expected application is to modulate the output power by adjusting the phase of the input signal.While the problem of multi-frequency signal input is more complex,mainly aiming at the phenomenon of frequency combination difference caused by multiple frequency input is studied.Through the analysis and comparison of PIC results and MATLAB simulation results,some expected assumptions of the realization of multi-channel structure traveling wave tube are obtained.（3）The two kinds of required electronic optical systems are designed respectively.According to the structure of Pierce electron gun,two electronic optical systems are designed by CST Studio Suit.The electron gun models have been co-simulated with PPM finally.The research on the multi-channel suspended structure is similar to the supported structure.However,due to the different input signal frequencies during simulation,based on the phenomenon of difference frequency and combination frequency in the previous chapter,it is concluded that the amplitudes of the output signals after amplification while adjusting signal frequency are not much different from those of the original single-frequency input signals.（4）By comprehensive consideration of simulation results and processing tech,two complete micro-strip slow-wave structure processing schemes are designed.Although the processing of electron gun and focusing system is not completed due to lack of time,cold test is carried out by assembling the existing processed samples.The suspended micro-strip structure transmission test is classified into three groups,like Rogers 5880,quartz and diamond,according to the substrate material.As for supported micro-strip structure,the supporting pod material is diamond.In addition,linear slow wave structure with wave-guide input/output is designed and tested.Straight lines are used to be an easier comparison to see if the transmission could meets requirements instead of micro-strip.Due to its small size and difficulty in positioning,a series of connection methods are tried,such as ultrasonic bonding machine and silver paste spot coating,and finally the existing sample are successfully assembled and the cold-test has been completed.The experimental results are far away different from what were supposed.Meanwhile,the detailed reason analysis and the next improvement plan are listed. |
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