共查询到20条相似文献,搜索用时 31 毫秒
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Keiichi Kamada Kouichi Nawashiro Fumiyasu Tamagawa Cha-Yeol Lee Hiroshi Yoshida Sunao Kawasaki Ritoku Ando Masaru Masuzaki 《International Journal of Infrared and Millimeter Waves》2000,21(9):1441-1449
A relativistic electron beam (500 keV, 200 A, 10 ns) generated magnetically tunable microwave radiation in a frequency range of 9-13 GHz when it is injected into an X-band rectangular waveguide immersed in a uniform axial magnetic field (4-10 kG). The mechanism of the microwave radiation was identified as the gyrotron backward wave interaction. The output power of the radiated microwave increased exponentially with the increase of the cavity length. 相似文献
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Keiichi Kamada Kouichi Nawashiro Fumiyasu Tamagawa Hisayoshi Igarashi Satiharu Kizu Cha-Yeol Lee Sunao Kawasaki Ritoku Ando Masaru Masuzaki 《International Journal of Infrared and Millimeter Waves》1998,19(10):1317-1324
A mildly relativistic electron beam (500keV, 200A, 10ns) injected into an X-band rectangular waveguide immersed in a uniform axial magnetic field (4-10kG) produced magnetically tunable microwave radiation in the 9-13 GHz frequency range with an estimated output power of 1MW. The frequency range and tunability of the radiated microwave agreed with a theoretical model for a gyrotron backward wave oscillator taking into account the low energy component of the beam electron. 相似文献
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R. W. McMillan S. M. Sharpe J. Seals M. G. Elis M. L. Studwell V. T. Brady E. C. Burdette 《International Journal of Infrared and Millimeter Waves》1986,7(9):1259-1280
This paper describes a millimeter wave frequency synthesizer based on a single broadband backward wave oscillator tube which is capable of covering the entire 40–60 GHz waveguide band with useful power output, low phase noise, and rapid frequency switching. The synthesizer is controlled by an internal microcomputer which sets the reference oscillator frequency through a General Purpose Interface Bus (GPIB) and generates synthesizer coarse tuning corrections through a programmable digital-to-analog converter. The phase/frequency control system uses a frequency discriminator for capture of the source from large frequency errors and a complementary phase lock for precise phase and frequency control. 相似文献
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In this paper, transmission characteristics of wave modes in a rectangular waveguide filled with lossless anisotropic metamaterial
are theoretically investigated. The wave equation and dispersion relations for TE and TM modes in the waveguide are obtained
and analyzed. It is shown that the negative constitutive parameters of the filling anisotropic metamaterial can be used to
control the wave magnitude and the phase velocity direction in the waveguide over the entire frequency domain, both below
and above the cutoff frequency. Particularly, not only backward waves, but also forward waves can propagate below the cutoff
frequency in the waveguide. Furthermore, a typical example is calculated to demonstrate transmission characteristics of waves
inside the waveguide. Numerical results are obtained in the paper and compared with theoretical predictions: a good agreement
is found. 相似文献
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GYROTRON III is a cw source of near-millimetre wave radiation that is tunable over the frequency range 75 to 330 GHz. The high-order waveguide modes that are characteristic of tunable gyrotrons are converted into a well-collimated, linearly-polarized beam by means of a quasi-optical or Vlasov antenna. 相似文献
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在研究磁探针耦合特性的基础上,设计了中心频率为4.0 GHz的3圈36单元高功率单层径向线螺旋阵列天线,各圈距中心位置分别为45,90,135 mm,单元个数分别为6,12,18。该天线采用磁探针代替电探针给短螺旋单元天线馈电,通过同轴-径向线模式转换器实现径向线TEM外行波激励,采用调整磁探针的探入深度和绕轴旋转短螺旋单元天线的方法改变单元的激励幅度与激励相位。数值模拟结果表明:该口径为324 mm的天线在中心频率上可获得21.58 dB的增益,口径效率可达78.2%,轴向轴比值为1.73;在3.8~4.2 GHz的频率范围内增益大于20.85 dB,口径效率大于73.2%,轴向轴比值小于2.0,反射系数小于0.27,辐射效率大于93%。 相似文献
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表面磁等离子体(surfacemagnetoplasmons,SMPs)是一种在电介质和偏置磁场作用下磁光材料界面处传播的近场电磁波.其独特的非互易传播特性引起了大量科研工作的关注,但在具体的波导结构设计上仍存在很多问题.本文研究了一种银-硅-磁光材料的3层平面波导结构,SMPs在磁光材料和硅的界面处传播,发现在特定的频率范围内,SMPs的基模及高阶模式均具有正向或反向的单向传播特性.分别计算了旋磁与旋电材料平面波导的色散方程,研究了硅层厚度与外加磁场对能带结构及SMPs单向传播区域的影响,发现无论是旋磁或旋电材料的结构,硅层厚度的增加使高阶模式使高阶模式出现在更低的频率位置,使单向传输带宽变小甚至消失,外加磁场的变大使磁光材料的能带结构频率增大的同时带隙中也引入了高阶模式.计算了2种磁光材料平面波导的正向和反向的单向传播带宽宽度,发现旋磁材料YIG的单向SMPs模式出现在GHz波段,最大单向带宽可达到2.45 GHz;旋电材料InSb的单向SMPs模式出现在THz波段,最大单向带宽达到3.9 THz. 相似文献
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C. S. Yeh N. Urimindi Jin Liu G. A. Evans J. K. Butler 《International Journal of Infrared and Millimeter Waves》1993,14(4):885-892
This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20 in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.Supported in part by the Army Research Office. 相似文献
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Q. Wu F.-Y. Meng J. Wu L.-W. Li 《Applied Physics A: Materials Science & Processing》2007,87(2):305-308
In this paper, broadband transmission characteristics of waves in a left-handed miniaturised rectangular waveguide (LHMRW)
loaded with improved split ring resonators (ISRRs), which shows that the bandwidth of negative permeability is up to 5.6 GHz
by an optimization design, are investigated. Some unexpected phenomena such as the discontinuous left-handed passband below
the cutoff frequency of the dominant TE mode, which cannot be transformed into a continuous one by any impedance matching
approach, are observed. The EM field distributions in the LHMRW are calculated so as to explain these phenomena. Results show
that the LHMRW can be considered as an open ended resonant cavity instead of a normal transmission structure. In addition,
the backward wave inside the time domain in the LHMRW is directly observed.
PACS 78.70.Gq; 81.05.Zx; 84.40.Ba 相似文献
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《中国物理 B》2015,(6)
In this paper,the basic equations of beam-wave interaction for designing the 220 GHz folded waveguide(FW)backward wave oscillator(BWO) are described.On the whole,these equations are mainly classified into small signal model(SSM),large signal model(LSM),and simplified small signal model(SSSM).Using these linear and nonlinear one-dimensional(1D) models,the oscillation characteristics of the FW BWO of a given configuration of slow wave structure(SWS) can be calculated by numerical iteration algorithm,which is more time efficient than three-dimensional(3D)particle-in-cell(PIC) simulation.The SSSM expressed by analytical formulas is innovatively derived for determining the initial values of the FW SWS conveniently.The dispersion characteristics of the FW are obtained by equivalent circuit analysis.The space charge effect,the end reflection effect,the lossy wall effect,and the relativistic effect are all considered in our models to offer more accurate results.The design process of the FW BWO tube with output power of watt scale in a frequency range between 215 GHz and 225 GHz based on these 1D models is demonstrated.The 3D PIC method is adopted to verify the theoretical design results,which shows that they are in good agreement with each other. 相似文献
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We investigated the dispersion property of a slab waveguide with an anisotropic metamaterial core whose permittivity tensor is partially negative. The subwavelength guidance characteristics are presented based on the boundary conditions. The results show that, at some specific frequencies, many high-order modes can exist in present waveguide even with the thickness of the guiding core 10 times smaller than the working wavelength. It is also found that different orientations of the optical axis of the anisotropic core will lead to different dispersion of the guided modes. If the orientation of the optical axis is properly chosen, the guided modes show a transition from backward wave to a forward wave as the frequency increases. During this transition, the group velocity of some guided modes can approach zero. Since the anisotropic metamaterial we discuss here can be fabricated in GHz, near- and mid-infra-red frequencies, our result may find some applications in wave trapper, integrated optical and nanophotonic devices. 相似文献
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运用超辐射机理,通过粒子模拟设计了X波段超辐射相对论返波管,并在小型Tesla脉冲源平台上开展了实验研究。通过空间功率积分和直接对辐射微波时域波形的分析得到实验结果:在束压350 kV、束流4.8 kA、脉宽3.1 ns、引导磁场2.2 T条件下,产生的微波辐射功率1.4 GW,中心频率9.36 GHz,脉宽500~700 ps,辐射模式为TE11,能在重复频率100 Hz下稳定运行。功率转换效率超过80%。实验结果与粒子模拟结果比较吻合,成功实现了在短脉冲条件下产生重复频率、亚纳秒脉宽、GW级微波辐射。 相似文献
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设计了一种高功率微波双波段同轴馈源,从理论分析和数值仿真两方面进行了验证。它采用同轴结构馈电,C波段的工作中心频率为4.15 GHz,利用加入轴向波纹的圆波导结构馈电;L波段的工作中心频率为1.75 GHz,利用同轴波导馈电。通过调整外筒半径的大小,可有效抑制低频段高阶模的传输,同时径向波纹结构可有效改善高频段微波的辐射特性。利用模式匹配法和组合散射矩阵理论对馈源结构进行了分析,理论计算和数值仿真结果具有良好的一致性,所设计的双波段馈源结构紧凑,副瓣电平低,E面和H面方向图等化特性良好。 相似文献
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为了研究负载为mH量级的间接馈电两级级联柱-锥构型的爆磁压缩产生器的基本物理过程和能量转换机理,利用描述爆磁压缩物理过程的2维爆轰磁流体力学程序MFCG(Ⅴ),以实验模型结构参数为基础模拟计算了一系列模型,分析了磁压对金属套筒径向膨胀速度及膨胀过程的影响。计算结果表明:套筒的径向膨胀速度取决于爆轰压与磁压的共同作用,在爆磁压缩过程的绝大部分时间里,向外膨胀的爆轰压都远大于向内压缩的磁压,因而套筒的径向膨胀速度主要是由爆轰压决定;但是在功率放大级的后半段,也就是发生器电流增长最快阶段,磁压也迅速增长,它的增长大大降低了套筒的径向膨胀速度;在功率放大级的后期,磁压已经超过爆轰压,它对系统设计的影响已经不能完全忽略。 相似文献