ANSYS软件在高频电磁场上的应用

本文介绍了ANSYS软件在高频电磁场仿真方面上的应用,分析了ANSYS软件在进行三维高频电磁场仿真所涉及的有限元分析和电磁场方面的基础理论,简要阐述了ANSYS软件的分析步骤、注意事项、高频电磁场激励源类型和电磁场边界条件等,用ANSYS软件对矩形谐振腔进行了模态分析,得到的数值解与理论分析的结果符合的非常好,也正确的反映了矩形谐振腔的谐振模式。     

探针馈电贴片天线的建模及其在滤波天线中的应用

针对探针馈电矩形微带贴片天线的建模,本文提出了一种新的集总元件等效电路,并给出了等效电路模型中元件参数的相关公式,尤其包含了馈电探针的位置参数.此等效电路的特点是其端口特性能够在比较宽的频率范围内与物理模型保持一致.为了验证该等效模型,以滤波器综合理论和所提出的等效电路模型为基础,设计了一个中心频率为2.4GHz,且具有二阶巴特沃尔斯带通滤波器响应的滤波天线,其中用提取好的2.4GHz探针馈电矩形微带贴片天线等效电路模型取代滤波器的末级谐振回路和端口.整个滤波天线的等效电路仿真结果与其物理结构仿真结果吻合较好,经实测得到的反射系数、方向图和增益也与仿真结果一致.     

SiO2-SiNx体系光学谐振腔中Ti超导薄膜特性的研究

设计良好的光学谐振腔是提高超导转变边沿传感器(TES)光学效率的有效手段，光学谐振腔结构厚度的变化，不仅对TES的光学效率有影响，而且会产生不同的残余应力进而影响TES的超导特性。研究了以超导Ti膜为TES功能层材料，同时选用SiO₂-SiN_x体系作为光学谐振腔薄膜。通过对数值仿真，确定了SiO₂-SiN_x体系光学谐振腔薄膜厚度变化对Ti-TES光学吸收效率的影响。分析了SiO₂-SiN_x体系光学谐振腔不同薄膜厚度的变化自身应力随之变化的趋势，最后制备了不同厚度SiO₂-SiN_x光学谐振腔的TES,并进行光学吸收效率的测试，验证了SiO₂-SiN_x体系光学谐振腔薄膜厚度对Ti-TES光学吸收效率变化的规律。     

一种同轴谐振腔微波增益均衡器设计的新方法

本文给出了用于补偿真空微波管增益波动的同轴谐振腔增益均衡器的一种新的设计方法。文中首先介绍了增益均衡器的作用与原理,然后给出了同轴谐振腔型增益均衡器的基本结构,并利用模式阻抗与驻波函数求得了谐振腔主传输线端的输入阻抗,最后利用等效电路求得了谐振腔的谐振频率。经与仿真软件的结果比对表明,利用本文方法所得到的结果是准确有效的。     

基于波导等效阻抗建模用于钛铁矿微波还原的谐振腔体研究

提出了一种利用等效阻抗的思想来设计微波谐振腔。通过计算传输波导的主模等效阻抗与谐振腔近似等效阻抗匹配来确定谐振腔体的尺寸,从而使多模谐振腔与传输波导具有良好的匹配,微波源能够以最小的反射馈入谐振腔内。以钛铁矿作为加热研究的物料,利用HFSS软件分别对单馈口和多馈口多模腔的反射系数进行了优化仿真,并且给出了腔体内场分布的情况,仿真优化的结果与等效阻抗匹配方法计算值接近,验证了根据波导等效阻抗方法来设计腔体结构的可行性,为设计高温微波冶金多模腔体提供了新的参考依据。     

基于经验模式分解的旋转机械振动信号降噪处理

分析了经验模式分解的滤波性能；针对旋转机械振动信号信噪比低及非平稳特性，应用经验模式分解对振动信号进行降噪处理，突出了有用振动信号，为旋转机械在线监测和故障诊断提供了有效的依据；仿真实验及真实数据分析表明，经验模式分解在振动信号降噪处理中是有效的，为振动信号分析提供了新的方法。     

利用频域求解器模拟计算谐振腔的谐振特性

以“通过法测品质因数”的冷测实验为理论基础,通过理论分析、数值模拟和冷测实验证明了利用三维电磁仿真软件的频域求解器也能模拟获得涂覆衰减材料的谐振腔本征模的谐振特性.对同一个涂覆衰减材料的谐振腔,该方法的计算结果和JDM本征模求解器的计算结果一致,并经冷测实验验证,计算精度很高,最重要的一点是该方法计算速度很快,解决了JDM本征模求解器因考虑损耗降低仿真速度的问题.     

基于ERB尺度的心理声学模型及其数值计算

粗糙度是评价声音幅度变化的一个基本的心理声学参数。针对人耳基底膜的滤波特性,提出了一种基于等效矩形带宽（ERB）的心理声学粗糙度模型。模型通过划分ERB尺度为75个滤波通道,计算幅度调制信号的广义调制指数,然后通过加权滤波并求和得到总的粗糙度。数值计算结果验证了模型对于幅度调制信号粗糙度计算的准确性,并且对于诸如调频信号、未调制信号等非幅度调制信号,模型的计算结果也有较好的一致性。特别是对于非调制信号,模型的计算结果与主观低粗糙感对应良好。     

悬浮石墨烯薄膜的压力敏感特性建模与仿真分析

针对悬浮式石墨烯压力传感器设计缺乏定量分析方法的问题,本文采用有限元建模仿真方法,建立了矩形、方形和圆形等3种不同形状悬浮石墨烯薄膜的压力敏感特性模型,仿真得到了其压力-应变关系,然后进行了不同条件及与实测值的对比分析.对比分析结果验证了有限元建模仿真的准确性,表明3种形状薄膜中矩形薄膜的中心形变位移和应变最大,且二者随薄膜尺寸的增大而增大.上述结果为悬浮式石墨烯压力传感器的结构与性能优化设计提供了有效指导.     

矩形翅片椭圆管束性能研究及场协同分析

应用计算流体动力学（CFD）理论,建立了矩形翅片椭圆管的数学模型,阐述求解的数值计算方法。采用k—ε标准湍流模型、有限体积法（FVM）和SIMPLEC算法,运用FLUENT软件对管外扰流场进行三维数值仿真,得到其阻力特性与换热特性,仿真结果与实验结果相对比,验证了模型的正确性。在此基础上,采用场协同原理分析了温度梯度与速度矢量的夹角对矩形翅片椭圆管换热特性的影响。结果表明：对流换热的强度不仅取决于流体的速度和物性,还取决于速度与温度梯度之间的协同,尽管迎面风速增大,换热得到强化,但随着协同角的增大,换热效率变低,以致换热量非线性增加。     

Optical vernier filter with fiber grating Fabry-Perot resonators

A simple optical vernier filter with fiber grating Fabry-Perot resonators is proposed. This vernier filter comprises two isolated Fabry-Perot fiber resonators in tandem; each is formed with two parallel fiber reflection gratings. A comparison between this vernier filter and one that uses fiber (or waveguide) ring resonators is made. It is found that this vernier grating filter is simpler and usually has better output characteristics than the others.     

Digital filtering for robust 50/60 Hz zero-crossing detectors

An improved digital filtering method for line frequency zero-crossing detectors is proposed. The multistage filter efficiently attenuates harmonics, wide-band noise, commutation notches, and other impulsive disturbances without causing any phase shift on the primary sinusoidal waveform. Our novel signal-processing system is a cascade of a median filter and an adaptive sinusoid predictor, followed by up-sampling and interpolation. The three-point median filter effectively removes impulses, and the predictor provides wide-band noise attenuation while compensating for delays in the other processing steps. The predictor adapts to possible line frequency variations within the specified range by changing the set of coefficients, based on an estimate of the instantaneous line frequency. The adaptive approach allows the use of highly selective IIR bandpass predictors     

Thin film bulk acoustic wave filter

Thin film bulk acoustic wave (BAW) resonators (FBAR) are fabricated on a silicon nitride bridge using a ZnO piezolayer on a glass substrate and surface micromachining by standard thin film technology. These resonators exhibit a coupling constant k/sub t//sup 2/=7.8% at the first thickness extensional wave mode and are used as impedance elements in a ladder filter in the 1-GHz frequency band of mobile telecommunications. An electrical equivalent circuit is used to characterize the properties of the resonators and to show how the performance of the filter depends on the parameters of the resonators. 2.5% bandwidth, 2.8-dB insertion loss, and 35-dB selectivity are obtained in a filter with six resonators. The technology can be used to manufacture miniature microwave filters without any additional inductances.     

Negative permittivity meta-material microstrip binomial low-pass filter with sharper cut-off and reduced size

A binomial low-pass filter provides the flattest pass-band response but slow attenuation transition. A design for improving the roll-off performance based on the negative-epsiv property of complementary split-ring resonators is presented, whilst maintaining the filter pass-band performance. By properly designing and integrating the complementary split-ring resonators with the low-pass filter, not only can the roll-off of the filter be significantly improved, but also the filter size further reduced. The measured results indicate that the proposed structure achieves a flat pass-band with no ripples as well as has a selectivity of 32 dB/GHz. This significantly exceeds the 17 dB/GHz selectivity of the conventional design. Furthermore, the proposed filter has a size smaller by 16%.     

Multi-objective design optimization of electrostatically actuated microbeam resonators with and without parameter uncertainty

Electrostatically actuated microbeam resonators are widely used components in microelectromechanical systems for sensing and signal filtering purposes. Due to the uncertainties resulting from manufacturing processes, material properties, and modeling assumptions, microbeam resonators may exhibit significant variations in their performance compared to nominal designs. There has been limited research on the performance prediction and the design optimization of such microsystems while accounting for relevant uncertainties. In this study, such uncertainties are considered in terms of the variability of parameters that define the dimensions, the material properties, and the operating conditions of the device. In addition, uncertainties with respect to a two-dimensional model of a microbeam resonator subject to electrostatic actuation are considered. A finite element model consisting of both the microbeam and the substrate is developed. The actuation forces are predicted by a reduced order electrostatic model, which accounts for the electromechanical interaction. A computationally efficient procedure is presented for simulating the steady-state dynamic response under electrostatic forces. The probabilistic performance of the microresonator is investigated using Monte Carlo simulation. A genetic algorithm is used to optimize the stochastic behavior of the microbeam resonator. The design is posed as combinatorial multi-objective optimization problem. Two design criteria describing the filter performance in terms of the shape of the frequency–response curve are simultaneously considered. The numerical results demonstrate the effectiveness of this procedure for the multi-objective optimization design of microbeam resonators and the importance of considering parameter uncertainty in the design of these devices.     

A Microwave Bandpass Filter on Dielectric Layers with Metal Grids

A bandpass filter of new design comprising dielectric layers with surface metal grids is developed and studied. Dielectric layers act as half-wave resonators, while metal grids act as mirrors with preset reflectivity and ensure optimum coupling between adjacent resonators and between the boundary resonators and free space. A test prototype of the third-order filter with a central bandpass frequency of ~12 GHz and relative bandwidth ~17% showed good agreement of theory and experiment. The proposed design can be used in making panels radio-transparent within a preset bandwidth for covering microwave antennas.     

Photonic highway switches based on ring resonators used as frequency-selective components

A new concept for a highway switch, which can be used to connect different optical wavelength division multiplexing data highways for data exchange, is proposed and the system relevant properties are outlined. For the required add-drop filter elements we used ring resonators. Typical characteristics of channel bandwidth, channel spacing, free spectral range, amplification, and cross-talk behavior of a highway switch with double-cavity ring resonators are basically examined and to some extent compared with solutions that were obtained with standard single-ring resonators. A signal flow chart transformation for evaluating filter transfer functions is presented.     

A miniature filter on a suspended substrate with a two-sided pattern of strip conductors

A miniature bandpass filter of new design with original stripline resonators on suspended substrate has been studied. The proposed filters of third to sixth order are distinguished for their high frequency-selective properties and mush smaller size in comparison to analogs. It is shown that a broad stopband extending above three-fold central bandpass frequency is determined by weak coupling of resonators at resonances of the second and third modes. A prototype sixth-order filter with a central frequency of 1 GHz, manufactured on a ceramic substrate with dielectric permittivity ε = 80, has contour dimensions of 36.6 × 4.8 × 0.5 mm³. Parametric synthesis of the filter, based on electrodynamic 3D model simulations, showed quite good agreement with the results of measurements.     

Equivalent circuit modeling of coupled resonator filters

Using the stacked crystal filter (SCF) concept, a coupled resonator filter (CRF) can be interpreted as a device in which 2 piezoresonators are stacked on top of each other in such a way that a certain degree of acoustic interaction occurs. The work presented in this paper reports a novel all-electrical model for the CRF. The model associates acoustical coupling with an equivalent electrical coupling between resonators. The resulting equivalent circuit makes it possible to apply classical filter synthesis techniques directly based on the coupling control between resonators. It complements with a synthesis approach the analysis approach of the Mason model.     

Investigation and Simulation of a Two-Channel Drop Filter with Tunable Double Optical Resonators

In this paper, a photonic crystal (PhC) two-channel drop filter based on two 2×2 & 2×3 ring resonators is proposed. This structure is made of Germanium rods in an air background at a two-dimensional (2D) square lattice. Refractive index is chosen in a way in which that device can be easily fabricated. The photonic crystal two-channel drop filter is composed using a horizontal waveguide and two ring resonators, which are placed symmetrically about the horizontal axis. These ring resonators operate as energy coupling and capture the electromagnetic energy propagated in bus waveguide at their resonance frequencies. The filter characteristics are calculated using 2D finite-difference time-domain (FDTD) and plane wave expansion (PWE) methods. We show a two-channel drop filter with two resonators, based on studied basic structures and achieving optimal modes for channel drop filters with one resonator. We have done this through choosing the proper radii for all rods of lattice, setting radii of coupling rods, lattice constant, and studying basic structures having different refractive indexes. Finally, we show 84 % and 100 % dropping efficiencies can be achieved at D and C ports in the communication window and 100 % in direct port. The size of this device is 14.56 μm (length)×11.96 μm (width). This small size makes it possible to use the device in multiplexer applications in future communication systems and in all-optical integrated circuits.