微波激励CO_2激光器表面波放电特性的分析

提出一种放电结构和理论模型，对表面波发生器的表面波放电等离子体特性进行了分析。在给定的工作气压、注入微波功率及所吸收的外场功率情况下，利用这一理论可以求出放电管内电子密度、电子温度以及微波电场强度的绝对值和径向分布。分析表明，这种放电结构很适于ＣＯ２激光器高效率的微波激励。     

Cherenkov radiation in a plasma-filled coaxial cylindrical dielectric slow-wave structure

In this paper, a new type of plasma-filled coaxial cylindrical dielectric slow-wave structure that is very beneficial to the beam-wave interaction of the high-power microwave source is developed. The Cherenkov radiation in the plasma-filled coaxial cylindrical dielectric slow-wave structure is examined by use of the self-consistent linear field theory. The dispersion equation and the synchronized condition as well as the wave growth rate of the beam-wave interaction are derived. The dispersion equation clearly shows that the Cherenkov radiation excited in the plasma-filled coaxial cylindrical dielectric slow-wave structure results from the coupling between the slow electromagnetic wave, TM-modes, propagated along the slow-wave structure and the negative-energy space-charge wave propagated along the relativistic electron beam. The numerical results indicate that the dispersion curves are divided into two branches due to the presence of the background plasma in the coaxial cylindrical dielectric slow-wave structure for the identical electromagnetic wave mode, and the radial distributions of the longitudinal fluctuating electric field corresponding to the two dispersion curve branches are completely different. Injection of the background plasma into the slow-wave structure can enhance the output frequency and the wave growth rate of the beam-wave interaction and enables the high-power microwave source that utilizes this kind of slow-wave structure to gain more output power of the microwave with higher output frequency.     

Linear Theory of Plasma-Filled Coaxial Cylindrical Cherenkov Maser

Injection of background plasma into the beam-wave interaction region can greatly enhance the beam-wave interaction efficiency and the microwave output power of the device. In this paper, a new type of plasma-filled slow-wave structure, i.e., plasma-filled, dielectric-loaded coaxial cylindrical waveguide with a dielectric ring enclosing tightly the inner conductor, is developed. The Cherenkov radiation excited by the beam-wave interaction in the slow-wave structure is examined by use of the self-consistent linear field theory. The dispersion equation and the synchronized condition of the beam-wave interaction are derived. It's clearly shown that the Cherenkov radiation excited by the beam-wave interaction results from the coupling between the slow electromagnetic wave, TM-modes, propagated along the slow-wave structure and the negative-energy space-charge wave propagated along the relativistic electron beam. And the wave growth rate is solved, and the beam-wave energy exchange in the presence of the background plasma is discussed. Finally, the effects of the background plasma density on the dispersion characteristics, the distribution of the longitudinal fluctuating electric field, the wave growth rate and the beam-wave energy exchange are calculated and discussed.     

多注行波管慢波结构的色散特性分析

多注行波管是一种具有工作电压低、瞬时工作带宽宽、容易实现大功率等优点的新型微波器件;本文主要利用CST Microwave Studio软件对多注行波管慢波结构的色散特性进行设计计算,并将计算结果和实验值进行比较分析。结果表明,计算值和实验值基本吻合。     

A Cylindrical Waveguide Structure with Helical Grooves for High Power TWTs

In this work, the field analysis of a cylindrical interaction structure, with helical grooves, and an inner dielectric lining for possible employment in high power TWT amplifiers in the conventional slow-wave regime, is presented. The Ohmic dominance of the microwave power on the walls of this propagating circuit is deduced.     

一种非均匀周期慢波结构返波管的模拟研究

为了提高返波管的工作效率,本文模拟设计了一个X 波段非均匀周期慢波结构的相对论返波管。模拟结果表 明：在电压为719kV,电流为10.2kA,磁场为3.0T 条件下,微波输出功率为2.81GW,工作频率为9.04GHz,效率为 38.3%,输出模式为TM01 模。模拟结果表明,采用非均匀周期慢波结构有效地提高了器件的工作效率。论文同时模拟 研究了电子束电压对器件输出功率、效率、工作频率的影响。     

A six-junction GaAs laser power converter with different sizes of active aperture

We investigate a novel GaAs-based laser power converters (LPCs) grown by metal-organic chemical vapor deposition (MOCVD), which uses a single monolithic structure with six junctions connected by tunnel junctions to obtain a high output voltage. The LPCs with diameters of active aperture of 2 mm and 4 mm were fabricated and tested. The test results show that under an 808 nm laser, two LPCs both show an open circuit voltage of above 6.5 V. A maximum power conversion efficiency of 50.2% is obtained by 2 mm sample with laser power of 0.256 W, and an output electric power of 1.9 W with laser power of 4.85 W is obtained by 4 mm sample. The performances of the LPCs are deteriorated under illumination of high flux, and the 4 mm sample shows a higher laser power tolerance.     

Compact Grating Structure for Application to Filters and Resonators in Monolithic Microwave Integrated Circuits

Possible high-Q circuits based on a new crosstie overlay slow-wave structure are proposed for monolithic microwave integrated circuits. Configurations and results of slow-wave factors are presented. This structure is used for construction of a frequency-selective reflector with a compact size. The effect of loss is considered.     

0.5 THz双电子注返波管注波互作用的高频结构优化

返波振荡器是一种重要的真空电子学太赫兹源,具有高功率、高工作频率和宽带调谐等特点。为提高圆形电子注与光栅慢波结构的互作用,提出一种双电子注嵌入矩形光栅的慢波结构,使电子注与光栅表面电场更好地充分相互作用,从而提高互作用效率和输出功率。通过数值求解和仿真计算其色散特性,结果表明,相比于相同结构参数的普通矩形单栅,该结构可以实现更高的工作频率和耦合阻抗。利用CST进行PIC仿真,优化结构和电子注参数,最终得到工作频率501 GHz,10.6 W的稳定输出。研究成果为设计0.5 THz的返波管提供了理论指导。     

A spiral-shaped defected ground structure for coplanar waveguide

The authors present a spiral-shaped defected ground structure for coplanar waveguides (DGSCPW), which can be used as a kind of periodic structure for a planar transmission line. The proposed spiral-DGSCPW adopts spiral-shaped defects on both ground planes of CPW. Due to the spiral-shaped defects, the equivalent shunt inductance and slow-wave effects increase more rapidly than the standard CPW or CPW lines combined with the conventional PBG. The modeling and analysis to extract the equivalent circuit, increased slow-wave factor, and simulated and measured performances are presented.     

A vertically periodic defected ground structure and its application in reducing the size of microwave circuits

The microstrip and coplanar waveguide transmission lines combined by a vertically periodic defected ground structure (VPDGS) are proposed. The slow-wave effect, equivalent circuit, and the performances are shown. As an application example, VPDGS is adopted in the matching networks of an amplifier for size-reduction. Two series microstrip lines in input and output matching networks of the amplifier are reduced to 38.5% and 44.4% of the original lengths, respectively, due to the increased slow-wave effects, while the amplifier performances are preserved.     

Characteristics of Metal-Insulator-Semiconductor Coplanar Waveguides for Monolithic Microwave Circuits

Using a full-wave mode-matching technique, an extensive analysis is presented of the slow-wave factor, attenuation, and characteristic impedance of a metal-insulator semiconductor coplanar waveguide (MISCPW) as functions of the various structural parameters. Design criteria are given for low-attenuation slow-wave propagation. By a proper optimization of the structure, performances comparable with or even better than those of alternative structures proposed in the literature are theoretically predicted.     

Slow-wave electrode for use in compound semiconductor electroopticmodulators

A slow-wave electrode structure for integrated optic traveling-wave modulators in which the microwave's effective refractive index is matched to the optical wave's effective refractive index is described. The electrode structure is a capacitively loaded coplanar strip waveguide which can be formed in a single layer of metallization. Fabrication can be accomplished by a single photo-resist patterning, followed by an etching and a standard lift-off technique. Based on the use of gallium arsenide substrates and modern lithographic techniques allowing fabrication with micron scale resolution, slow-wave electrodes having a microwave effective refractive index of 3.5, as well as 50 and 75 Ω characteristic impedances are proposed. The theory of slow-wave electrodes is developed, and slow-wave electrodes have been designed, fabricated, and tested to verify the theory. Measurement results are found to agree well with the theory     

带慢波结构的虚阴极振荡器

为探索新型高效率微波器件,受其它带慢波结构器件的启发,设计了由微波预调制腔、慢波结构腔和 微波提取腔组成的新型虚阴极振荡器。研究表明,由于慢波结构的存在,束-波转换效率高于普通虚阴极振荡器,在 电压550kV、电流16kA 下,可以获得频率为1. 95GHz,1. 4GW 的周期平均功率,16%的转换效率。随后在加速器平台 进行了初步的实验研究,获得了辐射功率约600MW,频率约1. 94GHz 的微波输出,频率单一,可实现锁频。分析知, 由于阴极制作过程导致电子发射不均匀是影响效率的主要原因。实验所测得的束-波转换效率达5%,表明该结构 的高功率微波器件可以提高束波转换效率。     

利用反馈环路稳定CO_2激光器的功率

本文报导CO_2激光器功率稳定环路的构成与性能。以荧光饱和吸收稳频的CO_2激光作基准,测定了功率稳定后的频率稳定性,结果表明,功率稳定可改善频率的长期稳定性。     

Perforated microstrip structure for miniaturising microwave devices

The perforated slow-wave microstrip is proposed for high-frequency microwave devices and characterised experimentally and theoretically up to 7 GHz. The perforated structure is realised with a periodic-inductive-section-maintained uniform edge-shape. The slow-wave factor is demonstrated to be 1.2 times larger than that of a conventional microstrip over a wide frequency range. The perforated slow-wave microstrip shows reduction of physical length and superior quality-factor. The proposed structure is easier to fabricate than other slow-wave structures, which require multilayer substrates     

盘荷波导慢波结构色散特性的变分分析

盘荷波导慢波结构可以看成由无数多个波导不连续性组成，每个波导不连续性可用一个T型网络描述，其参数能用变分方法得到，再根据无耗的四端微波网络理论，可以得到这种慢波结构的色散方程，因此本文得到了一种用于计算盘荷波导慢波结构色散特性的变分法。该变分法获得的色散特性结果与用场匹配法和HFSS模拟获得的结果符合得比较好。     

基于慢波基片集成波导的X波段功分器设计

针对传统基片集成波导（substrate integrated waveguide,SIW）功分器设计中宽带化和小型化不易兼顾的问题,提出了一种基于慢波SIW（slow-wave SIW, SW-SIW）的功分器. 采用微带折线构成的慢波结构单元加载于SIW金属表面上,代替传统SIW连续的金属表面,与同尺寸的SIW相比,SW-SIW的截止频率下降了40%,能够实现横向尺寸的缩减,尤其当SW-SIW达到与SIW相同的相移量时,SW-SIW所需纵向尺寸更小. 所提出的基于SW-SIW的功分器在具有较宽带宽的同时实现了器件尺寸的减小. 通过测试结果可得,该功分器在8.25～12.8 GHz频带内的反射系数|S₁₁|相似文献   

Measurement and Characterization of Microwave Interaction between Integrated Distributed Feedback Laser Diode and Electro-Absorption Modulator

Integrated electro-absorption-modulated distributed feedback laser diodes (EMLs) are attracting much interest in optical communications for the advantages of a compact structure, low power consumption, and high-speed modulation. In integrated EML, the microwave interaction between the distributed feedback laser diode (DFB-LD) and the electro-absorption modulator (EAM) has a nonnegligible influence on the modulation performance, especially at the high-frequency region. In this paper, integrated EML was investigated as a three-port network with two electrical inputs and a single optical output, where the scattering matrix of the integrated device was theoretically deduced and experimentally measured. Based on the theoretical model and the measured data, the microwave equivalent circuit model of the integrated device was established, from which the microwave interaction between DFB-LD and EAM was successfully extracted. The results reveal that the microwave interaction within integrated EML contains both the electrical isolation and optical coupling. The electrical isolation is bidirectional while the optical coupling is directional, which aggravates the microwave interaction in the direction from DFB-LD to EAM.     

Effect of microwave power and reactive gas ratio on the properties of silicon nitride thin films deposited by ECR PECVD

Silicon nitride films were deposited at room temperature on a single crystal silicon substrate by ECR PECVD (electron cyclotron resonance plasma enhanced chemical vapor deposition). Effects of the microwave power and the reactive gas ratio (SiH₄/N₂) on the film properties, such as, refractive index and breakdown field were investigated. It turned out that the microwave power was closely related to the change in refractive index of the silicon nitride films, while breakdown field did not change much from 6 MV/cm. It was also found that the deposition rate, refractive index, and breakdown field were changed in a certain way with respect to the change in SiH₄/N₂ ratio, which could be explained in terms of the activated chemical species concentrations in the plasma during deposition.