On the Theory of the Anisotropic Thermoelement

The anisotropic thermoelement (AT) has been studied in generation and cooling modes. A procedure to account for temperature dependences of material kinetic coefficients has been elaborated. The distributions of physical fields in the anisotropic thermoelement have been found. The efficiency and electromotive force (EMF) of the anisotropic thermoelement in the EMF and current generation modes have been calculated. Maximum temperature difference values, cooling capacities, and coefficients of performance have been determined for cooling mode with the use of Bi and CdSb materials.     

Improvements in the Noise Theory of the MMIC Distributed Amplifiers

Exact and simple expressions have been obtained for the intrinsic noise figure of monolithic microwave integrated circuit distributed amplifiers (DAs). The method has been applied on both MESFET and HBT DAs. It has been shown that the complexity of the obtained formulas is much less than that of the previously published literature. The results of the new theory are then compared with that of the previous theories and it has been shown that the results exactly match.      

行波管中聚焦磁场对互作用影响的研究

本文应用MAGIC模拟软件,研究了周期永磁聚焦螺旋线行波管中聚焦磁场的分布对电子轨迹的影响.分别模拟了电子的静态轨迹和互作用轨迹,通过对电子轨迹的分析,设计了一种渐变的磁场分布.应用MAGIC模拟软件对这种渐变磁场进行模拟仿真,结果显示这种渐变磁场可以有效抑制电子散焦,并通过仿真结果分析了如何设置这种新型磁场.     

石英MEMS陀螺的结构特性分析

介绍了石英微机电系统(MEMS)陀螺的工作原理及敏感芯片的音叉结构特点,采用有限元法分析了敏感芯片的结构特性,并对结构进行优化。利用石英晶体的压电效应,设计了合理的电极布局,并结合敏感芯片结构特点介绍了其微机械加工工艺。通过结构优化和合理的电极布局,提高了石英MEMS陀螺的性能。     

CCD摄像机像面中心的激光标定方法研究

论述了采用激光方法对视觉传感用CCD摄像机的像面中心进行标定的原理和方法 ,并对所采集的激光光斑图像进行适当的处理 ,通过求取质心的方法确定其精确位置 ,从而实现对像面中心的精确标定。实验结果表明 ,该方法计算量较小 ,精度较高。     

光轴位置及腔镜变形对多折腔输出特性的影响

本文研究在高功率横流CO2激光器多折腔中,影响光轴位置的几个因素及对输出特性的影响,并用实验方法确定了多折腔的最佳光轴位置。研究了多折腔中反射镜产生形变的原因,并从谐振腔参数出发,找到了克服这类腔型反射镜形变对输出特性影响的措施。     

利用频率选择表面改善微波吸收材料S波段的吸波性能

研究了如何利用金属周期性频率选择表面(FSS)的频率特性来改善微波吸收材料S波段的吸波性能。利用频率选择表面的等效电路和传输线理论分析了FSS和吸波材料涂层双层结构的微波反射特性。采用基于有限元方法的电磁波全波分析软件设计并仿真分析了FSS的结构和尺寸,实际制作了FSS和吸波材料涂层双层结构,测量了微波反射性能。理论分析和实验研究表明,利用FSS可以明显改善吸波材料涂层S波段的吸波性能,展宽涂层的吸波带宽,从而改善吸波材料的低频吸波性能。     

Effect of the green noise on the phase-locked-loop frequency-control system

The operation of the phase-locked-loop frequency-control system under the action of low-passfiltered broadband stationary noise (green noise) is considered. In order to analyze such systems, an averaging method that takes into account the external noise in a zeroth-order approximation has been constructed. Notions of an effective potential and correction process have been introduced and their role in the development of the dynamics of the system has been determined. A numerical experiment has been performed, which confirms the theoretical conclusions.     

A theoretical investigation of the rectangular microstrip antenna element

A theoretical treatment of the rectangular microstrip radiating element has been performed. The element has been modeled as a line resonator with radiation taking place at the open-circuited ends. This has been verified by using a liquid crystal visual detector. With the simplified model, the input impedance and the far fields have been calculated for different resonant modes. The interaction between the radiating ends will effect the input impedance, and this has been considered by defining a mutual conductance. Also, a mutual conductance between microstrip elements has been expressed in far-field quantities and plotted as a function of spacing along theE- andH- planes. The directivity of an isolated element has been calculated as the directivity of one radiating end times the contribution due to the array factor.     

压电光声技术对材料热性能的研究

利用光声压电(PAPE)技术测量研究材料的热扩散率, 开展了对钇铝石榴石(YAG)新型复合材料热扩散率的测量研究。介绍了基于简化热弹模型理论的光声压电法, 对利用简化热弹模型建立的光声压电理论进行推导, 根据简化的热弹模型, 建立了运用光声压电法检测材料热扩散率的实验系统; 运用光声压电法, 在不同的测试条件下, 对参考样品热扩散率进行检测, 完成了对实验系统的校准; 对YAG等新型复合材料的热扩散率开展测量研究。研究结果显示, 光声压电法是可以用来准确测量金属材料的热扩散率。在适当的实验条件下, 光声压电技术可以有效地测量新型复合材料的等效热扩散率。     

石英微机械陀螺敏感芯片的结构解耦特性研究

石英微机械陀螺敏感芯片通常采用双端音叉结构,驱动音叉和检测音叉的振动耦合误差是其主要误差源。对双端音叉结构陀螺敏感芯片进行了结构解耦设计仿真,分析了芯片安装区对检测音叉振动特性的影响。通过解耦设计,减小了零偏误差信号,提高了陀螺敏感芯片的稳定性。     

基于粒子系统的照明弹仿真方法

粒子系统被认为是最成功的模拟模糊物体的图形生成算法。文中针对照明弹效果仿真的问题,根据照明弹的工作原理,使用粒子系统理论,建立了照明弹模型,并利用OGRE图像渲染引擎,实现了照明弹的仿真效果。该仿真效果具有动态性,且视觉真实感较强。     

Effect of the microstructure on the properties of radio-absorbing nickel-zinc ferrites

The main approaches and results concerning an increase in the efficiency of broadband radioabsorbing nickel-zinc ferrites are reported. Requirements to the microstructure that ensure the expansion of the radio-absorption frequency range to 30–830 MHz have been developed. The effect of dopants on the frequency dependence of the absorption of electromagnetic waves has been analyzed. The efficiency of the formation of the coarse-grain structure with grain boundary layers having a high dielectric constant has been confirmed. It has been found that both doping with bismuth oxide and the introduction of a coarse-grain fraction of the same composition into a batch before the sintering of the powder enhance the absorbing properties of the ferrites.     

H表达的ECLD双稳环环宽的研究

采用H参量简化模型研究光栅调谐外腔半导体激光器的双稳特性,导出以H参量表达的双稳环环宽解析式,给出了其适用范围,得到剩余反射率减小时导致双稳环消失的临界值,然后数值模拟了光栅反射率、谱线展宽因子、H参量、剩余反射率对载流子密度与频率关系曲线的影响,从中发现了剩余反射率增大时也存在双稳环环宽为零的情况,数值计算了剩余反射率极限值,并指出了环宽极大值的位置。     

Numerical Solutions of the Integral Equation for Excitation-Transmission-Radiation of the Beam Waveguide

The numerical method of the Integral Equation has been used to model the electromagnetic excitation, transmission, and radiation problems of the beam waveguide. The Mode Matching Method has been used to describe the impedance matching situation at the exciting aperture of the waveguide. The excitation conditions were established based on the expansion of the waveguide modes and the continuity of the tangential components of the fields. The volume-surface integral equations combined with the equavalence principle have been used to model the wave transmission in the beam waveguide. The numerical solutions of the electromagnetic transmission and aperture radiation of the waveguide have been given by using the Multilevel Fast Multipole Algorithm (MLFMA). It has been demonstrated that the method proposed by this paper is able to provide the efficient and accurate numerical solution for the excitation, propagation and radiation problems of the beam waveguide with arbitrary shape and electrically large size.     

Effects of the inversion-layer centroid on the performance ofdouble-gate MOSFETs

The role of the inversion-layer centroid in a double-gate metal-oxide-semiconductor field-effect-transistor (DGMOSFET) has been investigated. The expression obtained for the inversion charge is similar to that found in conventional MOSFETs, with the inversion-charge centroid playing an identical role. The quantitative value of this magnitude has been analyzed in volume-inversion transistors and compared with the value obtained in conventional MOSFETs. The minority-carrier distribution has been found to be even closer to the interfaces in volume-inversion transistors with very thin films, and therefore, some of the advantages assumed for these devices are ungrounded. Finally, the overall advantages and disadvantages of double-gate MOSFET's over their conventional counterparts are discussed     

Analysis of the Effect of Ground Plane Size on the Performance of a Probe-fed Cavity Resonator Microstrip Antenna

In this paper, a probe-fed rectangular microstrip patch antenna with partially reflective superstrate at terahertz frequency (600 GHz) has been analyzed and simulated. The analysis of the partially reflective surface shows the highly reflective property of the surface over the wideband of the frequencies. The analysis of a specific configuration (rectangular patch) of partially reflective surface predicts the directivity of antenna to be the order of 24 dBi and subsequently it has been validated with the simulation. The proposed antenna has been simulated by using commercially available CST Microwave Studio simulator based on finite integral technique. Next to this, the application scenario of this kind of the antenna in the terahertz regime of the electromagnetic spectrum has been discussed and it has been obtained that this antenna is capable to establish 9 m long communication link.     

Effects of the inversion layer centroid on MOSFET behavior

The effects of the average inversion-layer penetration, the inversion-layer centroid, on the inversion-charge density and the gate-to-channel capacitance have been analyzed. The quantum model has been used, and a variety of data have been obtained by self-consistently solving the Poisson and Schrodinger equations. An empirical expression for the centroid position that is valid for a wide range of electrical and technological variables has been obtained and has been applied to accurately model the inversion-layer density and capacitance     

Perturbation theory for the evaluation of the normalised cutoff frequencies in radially inhomogeneous fibres

A simple perturbation theory has been used to study the normalised cutoff frequencies of radially inhomogeneous fibres. The formalism has been developed with a truncated parabolic-index profile as zero-order solution. Numerical calculations have been carried out for ?-profiles and have been found to be in good agreement with more rigorous approaches reported by previous authors.     

A novel bandpass filter using the amplifier pole

A new bandpass filter using the operational-amplifier pole and a single external capacitor has been described. It has been shown that the circuit can realize infinite pole-frequency Q product. The applicability of the circuit for realizing bandpass filters and oscillators has been investigated.