W波段阶梯型交错双栅慢波结构行波管的研究

为了提高传统交错双栅慢波结构行波管的性能,提出了一种阶梯型交错双栅慢波结构,并基于此新型慢波结构,提出了新型输入输出耦合结构.在此基础上,设计了一只工作在W波段的带状电子注阶梯型交错双栅慢波结构行波管.计算结果显示,阶梯型交错双栅慢波结构行波管的耦合阻抗更高,从而使行波管在更短的互作用电路长度里,实现更高的饱和增益和互作用效率.在90～100GHz频率范围内,阶梯型交错双栅慢波结构的耦合阻抗大于4Ω,高于传统交错双栅慢波结构;W波段带状电子注行波管高频结构的反射系数(S11)小于-15dB;并且行波管的饱和输入功率仅约为0.7W,可以实现最高输出功率约800W,相应的效率大于7.8%,增益大于30.6dB.     

W波段V型曲折矩形槽波导行波管的模拟研究

分析了一种新型慢波线-V型曲折矩形槽波导慢波结构,利用电磁仿真软件CST及HFSS对其高频特性进行了模拟计算,并在此基础上设计了工作在W波段的V型曲折矩形槽波导行波管的互作用结构.利用CST粒子工作室对其注-波互作用特性进行了模拟分析.结果表明:W波段V型曲折矩形槽波导行波管能够有效放大微波信号,且频谱纯净.     

高阻抗电磁表面及其在真空电子器件中的应用

近十年来,一种新型的高电磁阻抗表面得到迅速发展。这种高电磁阻抗表面实际上是一种新的电磁结构——光子带隙晶体结构。在频率禁带,这种结构的表面具有很高的电磁阻抗。利用这种特性,可以构建一种平面型行波管。这种行波管采用曲折线作互作用慢波电路。为了减小电磁波传输损耗,曲折线放置在高电磁阻抗表面上。本文对高电磁阻抗表面的特性和这种平面型行波管的工作原理进行了讨论。     

适用于Ka波段圆形电子注行波管的半圆形卷绕微带线慢波结构

提出了一种基于开槽介质基底的卷绕微带线慢波结构.由于金属曲折微带线印制在介质基底的半圆形槽中,这种卷绕微带线慢波结构非常适合圆形电子注行波管,从而使得采用这种新型慢波结构的行波管可以利用传统的周期永磁磁场进行聚焦.文章对提出的卷绕微带线慢波结构的色散特性,耦合阻抗,传输特性及注-波互作用进行了分析.和传统的平面微带线慢波结构相比,提出的卷绕微带线慢波结构具有更低的相速、更弱的色散和更高的耦合阻抗,从而使得其适合于低电压、宽频带、小型化的毫米波行波管.将同步电压及直流电流分别设置为6 550 V及0.1 A的情况下,基于该卷绕微带线慢波结构的Ka波段行波管在35 GHz处能够输出42.32 W的功率,对应增益为26.26 dB,且均匀聚焦磁场只需0.4 T.     

多注集成阵列梳齿型行波管模拟与冷测研究

多电子注集成实现微波放大是毫米波行波管获得大功率微波的一种实用化途径,研究了一种多注集成阵列梳齿型慢波结构（MCW）。该慢波结构具有天然的电子注通道,同时耦合阻抗明显高于单注的梳齿型慢波结构（DCW）。为了验证该特性,使用Ka波段三注集成阵列梳齿型互作用回路进行了仿真和实验研究。互作用电路的材料选取高电导率无氧铜,通过CNC铣削的工艺进行加工。冷测实验发现仿真和测试的结果具有很好的一致性,且在32~39 GHz的带宽内,S₁₁小于-15 dB。在仿真软件CST PIC工作室中,50个周期的慢波结构与三个电子注（每个电子注的电压为12.9kV,电流为67mA）进行注波互作用模拟仿真。仿真表明,MCW在32~36 GHz的带宽内比DCW具有更高的输出功率,增益和电子效率。该器件的最大输出功率约为132.8 W,相应的电子效率为5.12％,增益为41.2 dB,大于DCW的1.2%和25 dB。MCW行波管的高功率和高效率特性,使其在基于点对多点传输的毫米波无线系统中具有潜在的应用价值。     

W波段多种槽加载折叠波导行波管的研究

该文提出了3种槽加载折叠波导行波管慢波结构:三角形、梯形和燕尾形槽加载折叠波导。分析比较了不同槽形状对慢波结构的色散特性和耦合阻抗的影响。利用粒子模拟的方法对W波段4种槽加载折叠波导行波管的非线性注-波互作用进行了研究;在相同的电子注参数和输入功率的条件下,对输出功率、电子效率和增益等参量进行了比较。在多种槽加载结构中,梯形槽加载折叠波导输出功率(255 W)和增益(37.1 dB)最大,电子效率最高(10.7%);燕尾形槽加载折叠波导达到饱和所需要的互作用电路最短(64.2 mm);三角形槽加载折叠波导的3 dB带宽最宽。     

Ka波段曲折双脊单槽加载波导行波管研究

提出了一种新型的曲折波导慢波结构:曲折双脊单槽加载波导慢波结构.利用HFSS、CST电磁仿真软件对工作在Ka波段的曲折双脊单槽加载波导行波管进行了模拟计算,得到其高频特性及注-波互作用特性.结果表明,在33 GHz可以得到265 W的输出功率,增益为37.2 dB,3 dB增益带宽为6 GHz.     

0.14 THz双注折叠波导行波管的高频系统设计

随着太赫兹通信技术的发展,对于0.14 THz折叠波导行波管(FWTWT)的研究需求向着更高的功率和更宽的带宽发展。对双注行波管中的双路折叠波导慢波电路进行分析,得到不同参数下的高频特性变化规律。并对双路折叠波导慢波电路的功率分配和功率合成效率进行分析计算,得到功率合成效率96.3%。最后对双路慢波电路、功率分配/合成器和集中衰减器进行建模,并对注波互作用进行计算。在高压15 kV和单注电子的发射电流为40 mA条件下,得到0.14 THz频率下的合成输出功率为56 W,增益为31.4 dB,3 dB带宽为7 GHz。     

基于交错双栅结构的混合电路模型

带状注行波管作为一种发展中的新型器件在雷达和通信领域有广泛应用前景。相比于圆形注器件,目前针对带状注行波管的注波互作用模型仍较少。本文针对交错双栅这一常用的带状注慢波结构,从电路理论出发,研究了由分布式的传输线元件和集总电路原件构成的混合电路模型在刻画高频率慢波结构上的适用性,重点解决了从慢波结构几何参数到电路物理参数的映射问题。建立交错双栅混合电路模型,推导了色散方程,同时基于模拟退火算法实现了高精确度参数拟合。结果表明,混合电路模型能够精确刻画交错双栅的色散特性。该模型对后续开发基于混合电路模型的带状注大信号注波互作用程序具有重要意义。     

340 GHz菱形曲折波导慢波结构

提出并研究了一种菱形曲折波导慢波结构。与传统的矩形曲折波导慢波结构相比,菱形曲折波导慢波结构在相同频带下拥有更大的尺寸,在相同尺寸下拥有更宽的带宽。同时提出了适用于这种慢波结构的输入-输出过渡结构和衰减器。在此基础上,设计了一种用于行波管的340 GHz菱形曲折波导慢波结构,并采用相速负跳变技术提高了其增益。模拟仿真结果表明,在加载电压为15.3 kV,电流为35 mA的圆形电子注的情况下,行波管在343 GHz的输出功率和增益分别达到8 W和33 dB,其3 -dB带宽范围为330～348 GHz。     

The mechanism of transformation of a magnetostatic surface wave into an electromagnetic wave

On the basis of the analysis of the variations in the characteristics of a magnetostatic surface wave propagating in an inhomogeneously magnetized plane ferrite/dielectric structure, the physical mechanism of transformation of this wave into an electromagnetic wave has been studied and the radiation patterns have been calculated at various parameters of the structure for the case of a slowly changing surface impedance. The earlier experimental results are analyzed on the basis of these theoretical studies.     

Assimilation of altimeter significant wave height into a third-generation global spectral wave model

Data from three different altimeters (Topex/Poseidon, Jason-1, and European Remote Sensing Satellite 2) have been assimilated in a third-generation global spectral wave model forced by winds observed by scatterometer onboard QuikSCAT. Two different approaches of assimilation have been discussed. In the first approach, a simple scaling has been used to generate wave spectrum from altimeter-derived significant wave heights for assimilation in the model. In the second approach, the influence of altimeter observation has been spread to nearby grid points. Assimilation has been carried out every 6 h for five days. After the expiry of the assimilation phase, the model has been run in pure hindcast mode. Assimilation experiments have been carried out for the months of September and December 2002. Impact of assimilation has been found to be quite high in the Indian Ocean. It has been also found that the model is able to retain the memory of assimilation for a period of two and a half days as far as global ocean is concerned. This memory is more for the Indian Ocean. The wave spectrum generated by the model in the hindcast mode has been validated against the buoy-observed wave spectrum in the high sea conditions. The more significant impact has been seen in the case of altimeter track in the vicinity of the buoy.     

Pulse excitation of a travelling wave array

High-resolution radar becomes limited by the feeding mechanism in traveling wave antennas, forcing the design to some form of corporate feed. A spectral method of solving this problem is introduced which conveniently handles any transmitter pulse shape or receiver bandpass. The equivalence between this approach and an older transient solution is established. The method is applied to a uniform and a cosine illuminated aperture for both one- and two-way transmission through the antenna. It is shown that as a rule of thumb, the traveling wave feed should be less than half the spacial length of the transmitter pulse in the feed (L/V_{g}T < 0.5). Antennas exceeding this length must be divided into several sections, each of which must be corporately fed.     

Scattering of a beam wave by a spherical object

The theoretical analysis of the scattering of a beam wave by a small spherical object, which exists at the neighborhood of the beam waist on the propagation axis, is treated. In this analysis, the property of a spherical object is generalized so as to have anr-dependent dielectric constant. Through numerical calculations for the case of the conducting sphere, the difference between the scattering of a beam wave and that of a plane wave are discussed.     

Analysis of a polarized seismic wave model

We present a model for polarized seismic waves where the data are collected by three-component geophone receivers. The model is based on two parameters describing the polarization properties of the waveforms. These parameters are the ellipticity and the orientation angle of the polarization ellipse. The model describes longitudinal waveforms (P-waves) as well as elliptically polarized waves. For the latter waves the direction-of-propagation of the waveform is in the plane spanned by the ellipse's major and minor axes; Rayleigh waves are treated as a special case. We analyze the identifiability of the models and derive the Cramer-Rao and mean-square-angular-error (MSAE) bounds involving one or two three-component geophones     

Theory of a slow wave cyclotron amplifier

A new type of travelling wave amplifier is proposed which features a slow wave structure and wide bandwidth operation. It is bused on the cyclotron interaction between a slow electromagnetic wave and helically moving electrons. Gain and bandwidths are calculated including the effect of beam velocity spread. It is shown that a bandwidth as high as 50% could be achieved with beam velocity spread?1%.     

Magnetostatic wave technology: a review

Magnetostatic wave (MSW) technology has been under investigation for more than a decade. Using ferrimagnetic films such as liquid-phase epitaxial (LPE) yttrium iron garnet (YIG) films, MSW devices and subsystems offer instantaneous bandwidths of up to 1 GHz at operating frequencies in the microwave bands (0.5-26.5 GHz). Because MSWs travel with velocities two-to-four orders of magnitude slower than electromagnetic waves, compact devices can be built using hybrid and monolithic microwave integrated circuit (MMIC) techniques. These devices include delay lines, dispersive delay lines, filters, resonators, and directional couplers. Subsystems using these devices, such as electronically tunable delay lines channelized filter banks, delay-line discriminators, oscillators, and frequency multipliers can be used for applications in signal identification, control and processing directly at microwave frequencies. An overview of the MSW technology is presented and an assessment of the various devices and subsystems that can be built using thin and thick LPE-YIG films is provided     

Surface wave scattering by a step

The Wiener-Hopf technique is used to study the scattering of a surface wave which is incident upon the junction of two semi-infinite planes joined together by a step of heighta. Both the planes as well as the step have a normalized surface reactanceX, which supports the surface wave. The expression for the scattered field contains a series of unknown constants which require numerical solution. Graphs of the transmission and reflection coefficients for normalized reactances of 0.1 and 0.5 are presented for a step height of less than haft a wavelength.