70GHz二次谐波倍频回旋速调管高频系统研究

【作者】 王建勋；

【导师】 罗勇；

【作者基本信息】 电子科技大学 ， 物理电子学， 2007， 硕士

【摘要】 谐波倍频回旋速调管能在毫米波、亚毫米波产生高峰值功率，高平均功率，并有一定的带宽的微波毫米波，而且由于其谐波和倍频的两个特性使得它所需的磁场和对输入信号源的要求大为降低。这使它成为一种容易实现的高功率THz源。在军事和科研上都具有极其重要的应用前景，受到各国的重视，取得了长足的发展，并迅速成为一种极有潜力的高功率毫米波及THz源。本文利用模式匹配与散射矩阵级联的办法，分析计算了单级和多级突变及渐变结构的模式耦合与转化。结合高频计算软件HFSS设计了70GHz二次谐波倍频四腔回旋速调管的高频结构，包括输入腔，漂移段，群聚腔和输出腔。研究了TE₀₂模腔体绕射与模式转化问题，有效解决了谐波TE₀₂模工作时，由于漂移段不能截止70GHz的TE₀₁模而引发的一系列问题。利用HFSS对回旋速调管输入耦合器和回旋行波管输入耦合器进行了仿真与优化。提出了一种理论与软件模拟计算相结合的办法，有效的解决了输入耦合器内腔模式纯度的计算问题。研究了回旋速调管输入耦合器的耦合缝的分布形式、几何参数及个数对内腔模式纯度和耦合效率的影响。利用轨道理论对回旋速调管的输出腔进行了非线性非自洽的计算，并进行了优化。结果表明恰当的预群聚可以有效地提高互作用效率，而且即使二次谐波工作也能达到很高的互作用效率。建立了70GHz二次谐波倍频四腔回旋速调管的PIC计算模型，并进行了模拟计算和优化。研究输入功率和频率、电子电流、电子横纵速度比和纵向磁场强度等参数对输出功率、增益、效率的影响。通过优化得到了中心频率69.81 GHz的二次谐波倍频四腔回旋速调管放大器设计方案。粒子模拟表明：在工作电压70 kV，注电流13 A，电子注横向与纵向速度比为1.5，输入功率约10W时，输出功率256 kW，带宽160 MHz，电子效率28％，饱和增益44 dB。为配合课题研究需要，对基波TE₀₁模和基波TE₀₂模四腔回旋速调管进行了PIC模拟计算。对TE₀₁模在工作电压70kV，注电流12A，电子注横向与纵向速度比为1.5，输入功率约10W时，输出功率406kW，电子效率48.3％，饱和增益约46dB，绝对带宽约为650MHz，相对带宽1.9％。对TE₀₂模在工作电压70kV，注电流20A，电子注横向与纵向速度比为1.5，输入功率约12W时，输出功率708kW，电子效率50.6％，饱和增益约47dB，绝对带宽约为510MHz，相对带宽1.5％。本文在大量阅读和研究国内外相关文献的基础上，在导师的悉心指导下，对基波和谐波倍频回旋速调管进行创新性研究，取得了如下的一些新成果和新结论。对回旋速调管的设计研究具有重要的意义。1．对工作模为TE₀₂模的群聚腔绕射Q值随腔长成准周期性变化的研究。研究表明TE₀₂模与TE₀₁模群聚腔相比，端面处的相位和幅值以及绕射Q值和模式转化都有很大不同，且TE₀₂模群聚腔绕射Q值随腔长的变化成准周期性变化。并由此特点成功解决了二次谐波回旋速调管漂移段不能截止工作频率的TE₀₁模，从而引起的腔体间高频串扰的问题。这种研究对基波TE₀₂模工作也有相当大的价值。2．对回旋速调管输入耦合器模式纯度的研究，提出了一种模式纯度计算方法。回旋速调管输入耦合器国内外都有相关研究和报道，但对模式纯度只是一些定性的分析。本文首次提出了一种模式纯度计算方法，并对回旋速调管输入耦合器模式纯度进行定量计算，并对耦合缝的分布及几何参数等参量的变化对输入耦合器的模式纯度、频率、Q值和内腔储能等进行研究，成功设计了基波回旋速调管输入耦合器，并进行了试验冷测，结果基本一致。3．对预群聚电子注输出腔注波互作用的优化研究。利用非线性非自洽注波互作用理论优化计算，研究了预群聚基波和二次谐波输出腔注波互作用。进一步的研究将会极大的促进基波和二次谐波回旋速调管的研究及设计。4．对二次谐波倍频、基波TE₀₁模和基波TE₀₂模回旋速调管的PIC模拟优化。利用对TE₀₂模工作特性的研究，成功设计了基波和谐波倍频回旋速调管高频系统。PIC优化结果表明：所设计的70GHz二次谐波倍频回旋速调管的效率在高于国外相关PIC模拟报道的前提下，带宽是其报道的两倍多；所设计的Ka波段基波回旋速调管的效率达到50.6％和48.3％，带宽达到1.5％和1.9％。更多还原

【Abstract】 The frequency-doubling gyroklystron amplifiers not only can produce high pulsepower and high average power in millimeter and sub-millimeter wave bands withmoderate bandwidth, but also because of the harmonic and frequency-doubling property,it needs very low magnetic field, low frequency and power of the input signal. And thismade it become a good candidate sourse of high power THz microwave. So greatmilitary countries pay attention to development of frequency-doubling gyroklystronamplifier’s research, and spend a lot to develop them. Its research had become the frontand hotspot in the field of high power microwave and THz sourse.In this paper, the single and multiple abrupt section were studied usingmode-matching technique and scattering matrix formulation. A high frequency circuit ofa four cavities 70-GHz second-harmonic frequency-doubling gyroklystron has beenstudied in this method. The problem of mode conversion of the TE₀₂ mode is studied.A effective method is used to reduce the RF crosstalk of the 70GHz TE₀₁ mode betweencavities for drift section not cut off.The input coupler of gyroklystron is simulated and optimized by HFSS. A method,which combine theory and simulation, is proposed to solve the problem of calculatingthe purity of modes in coupler. The influence of the number and position of slots to thecoupling efficiency and purity of the modes were studied.The ballistic bunching theory was used to calculate and optimize the nonlinearproperty of the output cavity of gyroklystron. The results show that the prebunchingcould improve the interaction efficiency, even on second harmonic, the high efficiencycould achieved also.A 70GHz second-harmonic frequency-doubling gyroklystron with four cavities hasbeen studied. The Q factor and mode conversion of the bunching cavities were studiedin detail with field matching analysis to reduce the RF crosstalk of the 70GHz TE₀₁mode between cavities. And the RF circuit was designed and optimized to enhanceoperating bandwidth and electron efficiency. And then a 70GHz second-harmonic frequency-doubling gyroklystron was designed. 256kW output power, 44dB saturationgain, 28% electron efficiency can be obtained with about 160MHz instantaneousbandwidth were obtain by PIC simulation at 70-kV, 13A electron beam.The two kinds of first harmonic gyroklystron which working in TE₀₁ mode and TE₀₂mode was simulated too. When working in TE₀₁ mode, 406kW output power, 46dBsaturation gain, 48.3% electron efficiency can be obtained by PIC simulation at 70-kV,12A electron beam. While working in TE₀₂ mode, 708kW output power, 47dBsaturation gain, 50.6% electron efficiency can be obtained by PIC simulation at 70-kV,20A electron beam.更多还原