矩形栅慢波系统的高频特性分析

对于矩形栅这一经典的慢波结构,采用场匹配法来分析其慢波特性,进而得到其耦合阻抗。其中对槽区内的场处理,保留其高次项,表示为一无限本征驻波之和的形式。然后通过数值实例具体分析了矩形栅的两种典型结构：浅槽栅和深槽栅。当增大槽深后,色散增强,系统通带变窄,同时耦合阻抗有明显增大,工作点移向前向波区,适合用在放大器的慢波结构上。     

矩形栅慢波系统的高频特性分析

对于矩形栅这一经典的慢波结构，采用场匹配法来分析其慢波特性，进而得到其耦合阻抗。其中对槽区内的场处理，保留其高次项，表示为一无限本征驻波之和的形式。然后通过数值实例具体分析了矩形栅的两种典型结构:浅槽栅和深槽栅。当增大槽深后，色散增强，系统通带变窄，同时耦合阻抗有明显增大，工作点移向前向波区，适合用在放大器的慢波结构上。     

基于场匹配法的双排矩形栅慢波结构高频特性研究

本文运用场匹配法对具有任意位错的双排矩形栅慢波结构的场分布、色散特性及耦合阻抗进行了研究．研究结果表明,场匹配法推导的色散特性与仿真软件CST和HFSS计算的结果完全一致,耦合阻抗介于CST和HFSS之间．在此基础上,详细研究了上下两排系统之间位错对色散特性及耦合阻抗的影响．当位错严格为半个周期时,第一阻带消失,第一个模式最高截止频率与第二个模式最低截止频率重叠,发生简并;当位错为0．45倍周期时,在保证耦合阻抗不变的情况下,基模的通带虽降低了2．8GHz,但阻带却增大了7．9GHz,从而可以有效避免简并及模式竞争的发生．     

新型自由矩形螺旋线慢波结构高频特性

 在Sheath模型下,采用严格的场匹配法,结合积分形式的边界条件,推导了自由矩形螺旋线的色散方程和耦合阻抗表达式,并与近似理论进行对比。结果表明:与近似理论相比, 严禁场匹配法具有更高的准确性,且采用场匹配法的数值计算结果与3维商业电磁仿真软件结果吻合得很好。从而证明了所采用理论方法的有效性。同时分析了矩形螺旋线横截面尺寸、螺距、螺旋角、纵横比对色散特性和耦合阻抗的影响,结果表明：只有当矩形螺旋线横截面纵横比大于4时,才可忽略横截面的宽度对高频特性的影响,通过调节结构的参数可以改善色散和提高耦合阻抗。     

新型自由矩形螺旋线慢波结构高频特性

在Sheath模型下,采用严格的场匹配法,结合积分形式的边界条件,推导了自由矩形螺旋线的色散方程和耦合阻抗表达式,并与近似理论进行对比。结果表明:与近似理论相比, 严禁场匹配法具有更高的准确性,且采用场匹配法的数值计算结果与3维商业电磁仿真软件结果吻合得很好。从而证明了所采用理论方法的有效性。同时分析了矩形螺旋线横截面尺寸、螺距、螺旋角、纵横比对色散特性和耦合阻抗的影响,结果表明：只有当矩形螺旋线横截面纵横比大于4时,才可忽略横截面的宽度对高频特性的影响,通过调节结构的参数可以改善色散和提高耦合阻抗。     

曲折圆形槽波导慢波系统的高频特性

 对曲折圆形槽波导新型慢波系统的高频特性进行了研究,通过理论分析和数值计算,得到了它的色散曲线和耦合阻抗表达式,并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明：当周期变小时色散减弱,耦合阻抗增加;而增大直波导长度时色散变弱,但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低,可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点,在毫米波及亚毫米波段的行波管中具有较好的发展前景。     

曲折圆形槽波导慢波系统的高频特性

对曲折圆形槽波导新型慢波系统的高频特性进行了研究,通过理论分析和数值计算,得到了它的色散曲线和耦合阻抗表达式,并分析了结构参数变化对色散特性和耦合阻抗的影响。研究表明：当周期变小时色散减弱,耦合阻抗增加;而增大直波导长度时色散变弱,但同时耦合阻抗也会下降。因此较小的周期有利于改善曲折圆形槽波导慢波电路的高频特性。鉴于这种电路的耦合阻抗较低,可以适当地减小直波导长度来提高耦合阻抗。曲折槽波导结合了曲折波导散热能力强、色散特性好、容易加工和槽波导单模工作、低损耗、大尺寸等优点,在毫米波及亚毫米波段的行波管中具有较好的发展前景。     

带状注行波管双矩形螺旋线慢波结构高频特性

针对新型螺旋线慢波结构双矩形螺旋线慢波结构,即在金属屏蔽框内平行加载两个具有矩形横截面形状的自由螺旋线慢波结构,利用三维电磁仿真软件对其高频特性（色散特性和耦合阻抗）进行模拟研究。结果表明：在相同位置处,与单矩形螺旋线慢波结构相比,双矩形螺旋线慢波结构色散特性变化很小,却有着更高的耦合阻抗;同时,在包含这些位置的空间部分,可采用带状电子注与该慢波结构进行注波互作用,使输出功率进一步得到提高。     

金属柱平板慢波系统高频特性研究

对于离散的金属柱结构构建的周期性平板慢波系统,本文利用3维FDTD方法结合HFSS仿真软件深入分析了该慢波系统的高频特性.研究了金属柱高度、周期长度对色散特性的影响,计算了耦合阻抗,并与传统光栅慢波系统特性进行了对比分析.分析表明金属柱慢波系统既有与传统光栅慢波系统相似的高频特性,又具有独自的特点,位于离散的金属柱周期间隙中的电子注互作用耦合阻抗具有对称性;金属柱结构用作真空电子器件的高频系统可增加发生有效互作用的电子注厚度,降低起振电流密度,提高器件效率.本文的分析结果为设计低电流密度工作的多电子注短毫关键词：金属柱平板慢波系统3维FDTD算法色散特性耦合阻抗     

带状注行波管双矩形螺旋线慢波结构高频特性北大核心CSCD

针对新型螺旋线慢波结构——双矩形螺旋线慢波结构,即在金属屏蔽框内平行加载两个具有矩形横截面形状的自由螺旋线慢波结构,利用三维电磁仿真软件对其高频特性(色散特性和耦合阻抗)进行模拟研究。结果表明:在相同位置处,与单矩形螺旋线慢波结构相比,双矩形螺旋线慢波结构色散特性变化很小,却有着更高的耦合阻抗;同时,在包含这些位置的空间部分,可采用带状电子注与该慢波结构进行注波互作用,使输出功率进一步得到提高。     

内开槽矩形波导栅慢波电路高频特性的数值分析

 介绍了用德国CST公司提供的MWS 4.2软件模拟计算色散特性和耦合阻抗的理论方法,对内开槽矩形波导栅结构的高频特性进行了数值模拟。结果表明：在传统矩形波导栅结构的基础上,开槽后的矩形波导栅结构比开槽前的相速更低,用作行波管的慢波结构时,可降低工作电压,工艺上容易实现,而且耦合阻抗均在45 W以上,满足毫米波行波管的要求;在内开槽宽度一定的前提下,槽深、栅间距和栅周期的增大对降低系统相速有利。     

矩形波导栅慢波系统的实验研究

 从实验上研究了矩形波导栅慢波系统的色散特性及其耦合装置的驻波系数,用分布加工的方法分别制作了矩形、燕尾形、梯形3种不同槽形的矩形波导栅慢波结构模型和带输入输出结构的矩形波导栅慢波结构实体模型。采用谐振法测量它们的色散特性和驻波系数,实验结果与理论计算值和模拟值吻合良好。     

Angular spectrum theory to calculate coupling efficiency in rectangular waveguide resonators

Coupling efficiency of the rectangular waveguide resonators are discussed in terms of the method of angular spectrum theory. Under the condition given in the paper, the coupling coefficients for the EH₁₁ mode in the rectangular waveguide resonator are presented as a function of mirror curvature and position. It is shown that there exist two special geometries to provide low coupling efficiency. The method can be applied to the other modes.     

Study of the double rectangular waveguide grating slow-wave structure

A slow-wave structure (SWS) with two opposite gratings inside a rectangular waveguide is presented and analysed. As an all-metal slow-wave circuit, this structure is especially suited for use in millimetre-wave travelling wave tubes (TWTs) due to its advantages of large size, high manufacturing precision and good heat dissipation. The first part of this paper concerns the wave properties of this structure in vacuum. The influence of the geometrical dimensions on dispersion characteristics and coupling impedance is investigated. The theoretical results show that this structure has a very strong dispersion and the coupling impedance for the fundamental wave is several tens of ohms, but the coupling impedance for --1 space harmonic wave is much lower than that for the fundamental wave, so the risk of backward wave oscillation is reduced. Besides these, the CST microwave studio is also used to simulate the dispersion property of the SWS. The simulation results from CST and the theoretical results agree well with each other, which supports the theory. In the second part, a small-signal analysis of a double rectangular waveguide grating TWT is presented. The typical small-signal gain per period is about 0.45 dB, and the 3-dB small-signal gain bandwidth is only 4\%.     

脊加载同轴交错圆盘波导的高频特性

提出脊加载同轴交错圆盘波导慢波结构,并用电磁场仿真软件HFSS对其色散特性和耦合阻抗进行了计算,分析了不同结构参数对其高频特性的影响。研究表明:脊加载同轴交错圆盘波导有较好的色散特性,它比非同轴结构的带宽有明显增加,同时可以降低慢波结构的相速,用作行波管慢波结构时可以降低工作电压。脊加载同轴交错圆盘波导是一种全金属结构,散热性能好,损耗低,在毫米波及亚毫米波段的行波管中有较好的应用前景。     

Resonant waveguide grating: Analysis of polarization independent filtering

We investigate the property of polarization independent reflection using a 1D grating. It is shown to be possible, by choosing the correct parameters of the structure and angle of incidence to adjust the bandwidth of the reflection curves for both polarizations in such a way that these coincide. We expect that the found polarization-independent narrow band filter can be used as a component for WDM applications.     

Novel wavelength-accurate InP-based arrayed waveguide grating

A 13-channel, InP-based arrayed waveguide grating （AWG） is designed and fabricated in which the on-chip loss of the central channel is about -5 dB and the crosstalk is less than -23 dB in the center of the spectrum response. However, the central wavelength and channel spacing are deviated from the design values. To improve their accuracy, an optimized design is adopted to compensate the process error. As a result, the central wavelength 1549.9 nm and channel spacing 1.59 nm are obtained in the experiment, while their design values are 1549.32 nm and 1.6 nm, respectively. The route capability and thermo-optic characteristic of the AWG are also discussed in detail.     

Transmission characteristics of a microscale dielectric slab waveguide device with a deep groove and an embedded metallodielectric grating at low terahertz frequency

We discuss the transmission characteristics of a microscale dielectric waveguide device with a deep groove and an embedded metallodielectric grating illuminated by a continuous wave of TM and TE modes at low terahertz frequency. To study its performance we solve numerically the corresponding Maxwell equations by means of finite difference time domain method with uniaxial perfectly match layer as its boundary condition. By varying the angle of incident, grating filling factor and refractive index of analyte in the deep groove, it is found that the device exhibits a significant transmission enhancement for the TM mode due to the existence of surface plasmon interaction. We also demonstrate its potential application as a biosensor device.     

Generalized source method: New possibilities for waveguide and grating problems

A new, general and exact method for resolving waveguide and grating problems is presented whereby the unknown electric field in a given dielectric distribution in the presence of an arbitrary source distribution can be obtained exactly from the known complete electric field solution in a simpler dielectric structure in the presence of the same source distribution. The method can be used in the form of an iterative scheme. The solution can also be obtained through an implicit equation which can be solved numerically without convergence problem by matrix inversion. The application of the method to the case of abnormal reflection under normal incidence from a segmented waveguide is given as an example.