Finite Element Modeling of Surface Acoustic Wave Devices Using COMSOL

Russian Microelectronics - The results of the research and analysis of wave acoustic processes in piezoelectric substrates based on the solution of wave equations of piezoacoustics by the finite...     

用MATLAB模拟三层平板波导的模式特性

本文建立三层平板光波导模型，推导出电场方程的具体形式，运用MATLAB对三层平板波导理论进行分析求解，使以往复杂的计算变的非常简单。将具体数值代人电场方程进行计算，取不同的波导层厚度时得到不同的波导模式，然后做出不同波导模式TE波的三维图形。最后介绍了三层平板波导理论在激光器模式理论中的应用。     

Modeling Rectangular Waveguide Junctions by the Eigenfunction Method

A method to determine the impedance and admittance matrices of a certain class of rectangular waveguide junctions is presented. First, general matrices are obtained relating all of the modes that may exist in the waveguides connected to the ports, The expressions for the matrix entries are given in terms of the eigenfunctions of the volume occupied by the junction and the fields at the ports. Second, to obtain a relationship between the propagating modes of the connecting waveguides, a numerical iterative procedure is developed to eliminate the evanescent modes from the general matrices. Practical applications have shown that the results agree well with the previous ones, and the method can readily be used to analyze different types of junctions in any required frequency range.     

Ensemble Acoustic Modeling for CD-DNN-HMM Using Random Forests of Phonetic Decision Trees

We propose a novel approach to generate an ensemble of context-dependent deep neural networks (CD-DNNs) by using random forests of phonetic decision trees (RF-PDTs) and construct an ensemble acoustic model (EAM) accordingly for speech recognition. We present evaluation results on the TIMIT dataset and a telemedicine automatic captioning dataset and demonstrate the superior performance of the proposed RF-PDT+CD-DNN based EAM over the conventional CD-DNN based single acoustic model (SAM) in phone and word recognition accuracies.     

声表面波小波处理器的计算机模拟与仿真

由于缺乏基本的计算机模拟与仿真手段,我们无法在试制样品前预估所设计的声表面波小波处理器的性能参数。因而,一旦设计参数出现偏差,所试制的样品的性能指标也就不可能满足设计要求,这不但延长研发周期,而且浪费大量不必要的研发经费。为此,该文介绍了一种对声表面波小波处理器进行计算机模拟与仿真的模型,并将其用于声表面波小波处理器的设计研制中,以期在样品试制前对其进行计算机模拟与仿真,直至模拟与仿真结果满足设计要求后再进行样品试制与测试,以尽可能地缩短研究周期,节约研究经费。理论与研究结果表明,采用该文介绍的计算机模拟与仿真模型对声表面波小波处理器进行计算机模拟与仿真,其模拟仿真结果与实测结果相比,其误差小于1%,基本能满足设计研发工作的需要。     

A High-Capacity Digital Communication System Using TE/sub 01/ Transmission in Circular Waveguide

In this paper, we describe the characteristics and several parts of a high-capacity digital communications system using the low-loss circular waveguide.     

数字声波系统设计

该文介绍了用于数字声波的多通道同步数据采集系统设计与实现方案,针对多通道声波数据采集时序控制复杂的特点,每个通道数据由独立的ADC进行处理,同时使用单个FPGA和单个DSP进行数据处理分析,提高了数据处理的实时性和系统的可靠性,缩短了仪器尺寸提高仪器可靠性,降低单只仪器制造成本,提高了市场竞争力。     

无线Mesh网络的新型建模方法研究

对无线Mesh网络准确建模是开展Mesh网络各项研究的基础,基于传统802.11协议模型来分析Mesh网络性能会导致较大的偏差。提出了一种适用于无线Mesh网络的新型模型用以计算网络饱和状态下性能参数的理论值,如丢包率、节点发送概率等,性能分析和仿真结果表明,该方法更能精确地评估无线Mesh网性能。同时在此基础上给出了路由判据ETX理论值的计算方法,该方法可用来预测ETX值而无需实测,从而有效的减少了测量误差和带宽消耗。     

Waveguide Probes Using Single Negative Media

In this work, we show that by using single negative (SNG) media, the sensitivity of open-ended near-field waveguide probes can be enhanced. The enhancement is due to the evanescent wave amplification property of SNG media. As a demonstration of the efficacy of the proposed SNG-enhanced probe, we present a numerical study of the case of detecting precursor pitting in aluminum plates. We show that the SNG-enhanced probe achieves 35 times increase in the phase shift due to the presence of the target in comparison to the case of a classical probe. We show that there is an optimum SNG media thickness and an optimum standoff distance that maximize the sensitivity.     

Submillimeter Components Using Oversize Quasi-Optical Waveguide

Components such as directional couplers, attenuators, introduction and phase shifters have been developed using optical techniques in oversize rectangular waveguide. These components were designed for operation in the 300- to 350-Gc range. They were scaled from a design that was successful at 27 Gc. Preliminary data taken at 330 Gc indicates the feasibility of this technique. The advantages of oversize waveguide as compared with conventional waveguide and freespace optical components are 1) lower attenuation and 2) simpler construction.     

离子束辅助沉积真空镀膜技术制备阵列波导光栅波导材料

采用离子束辅助沉积(IBAD)真空镀膜技术制备阵列波导光栅(AWG)波导材料。以固体石英玻璃材料作为衬底,采用离子束辅助沉积真空镀膜制备SiO2膜层,以实现偏振不敏感的阵列波导光栅。实验表明器件的偏振相关性大大改善,其双折射B约为1.4077×10-5,远小于二氧化硅-硅基波导结构阵列波导光栅的双折射B=2×10-4。器件的热稳定性也得以改善,当工作环境的温度变化范围为-10~70℃时,采用此方法研制的阵列波导光栅最大波长漂移为1.144 nm,小于普通的二氧化硅-硅基波导结构阵列波导光栅的波长漂移1.368 nm。     

Ranging and Data Transmission Using Digital Encoded FM-"Chirp" Surface Acoustic Wave Filters

A digital encoded multislope chirp modem/demodem unit has been implemented using two 3-port surface acoustic wave filters. Each filter operating at a 30-MHz center frequency provides either positive or negative slopes as digital 1's or 0's with a time-bandwidth product of 280, an unweighed bandwidth of 5.6 MHz, and a time dispersion of 50 /spl mu/S.The modems were used to calibrate and compare the operational performance of the conventions multitone CW ranging system with a multislope chirp ranging system. Range measurements and range-rate observations were made to a synchronous satellite with both systems using a ground communication satellite terminal. Both ranging techniques provided accuracies well within the predictable satellite range of 20 000 nmi; the multitone system provided a theoretical range resolution of 1 m, and the chirp system 0.4 m. Data transmission was also accomplished, using 12-bit binary code at a 1.25-Mbit rate. The significant advantage to be noted with the chirp system is the ability to obtain continuous range data from the satellite repeater simultaneously while other modes of information are being transmitted, and to combine the ranging and data-link transmission on a time-order basis using digital encoded chirp sequences. The chirp system was found the more desirable technique, since it provides a more direct range measurement, with minimal calibration requirements, and provided greater processing gain with relative ease and reliability. The data transmission at low data rates provided little deterioration in theoretical compressive gain. However, at the higher data rate a greater loss was encountered due to power sharing of the overlapping chirp coded carriers in the limiting satellite.     

Nonreciprocal Remanence Ferrite Phase Shifters Using the Grooved Waveguide

For the purpose of improving the performance charasteristics of the nonreciprocal remanence ferrite phase shifter, a new configuration with a grooved waveguide is proposed and analyzed. Some results calculated as functions of dielectric and ferrite thickness, waveguide dimensions, and frequency are shown and compared as being in good agreement with experiments at the X band. The figure of merit (differential phase shift per insertion loss) and the handling power of the proposed phase shifter are discussed in comparison with those of the conventional waveguide geometry.     

基于双模谐振器的W波段波导带通滤波器

带通滤波器为现代毫米波系统中进行频率选择的重要器件,而波导滤波器因其低损耗、大功率容量、易加工等优点成为首选。为满足系统的小型化要求,设计了一种基于双模谐振器且具有准椭圆函数响应的W波段波导带通滤波器。该波导带通滤波器结构简单紧凑,由两个双模方形脊谐振腔组成,可获得2 个传输零点及四阶准椭圆函数响应。滤波器样品选取紫铜材质,采用CNC 技术加工制作。经矢量网络分析仪测试,该滤波器通带内插损低,达0.5 dB,3 dB 波束带宽为4.35 %(92.2 ~96.3 GHz),回波损耗优于20 dB,通带外存在两个非对称零点。在全W波段的测试结果与仿真数据高度吻合。     

Broad-Band Ferrite Rotators Using Quadruply-Ridged Circular Waveguide

It has been shown that the rotation of the plane of polarization of a wave propagating in a magnetized unbounded ferrite medium should be independent of frequency. However this is not the case when a ferrite rod of small diameter is placed within a waveguide. For example, if a ferrite rod one-quarter inch in diameter in a fifteen-sixteenth inch diameter circular waveguide is used, the rotation will change by a factor of four to one over the frequency band from 8000 to 10,000 mc. This variation in rotation is substantially due to the waveguide characteristics, and can be minimized by lowering the cutoff frequency of the waveguide. Various methods of lowering the cutoff of circular waveguide are compared. Data on the broadbanding of the rotation by dielectric loading and also by the use of quadruply-ridged circular waveguide is shown. An experimental study showing the effect of the ridge width and height on the cutoff of the circular waveguide and the frequency dependence of the rotation is discussed.     

利用高频结构仿真器分析波导魔T

高频结构仿真器（HFSS）是一种微波器件设计软件，该软件界面友好，通过仿真计算减小了调试工作量，使得微波器件的设计变得简单易行。本文利用HFSS对波导魔T进行了仿真分析，得到了该器件的S参数和动、静态场的分布情况，并对该器件进行了优化设计。     

室内声场建模方法最新发展

室内声场计算机仿真是近年来在声学领域颇受重视的研究方向。近来波导网络法、自适应声束跟踪法和神经网络法开始被引入,并逐渐受到重视。着重介绍这三种新方法的基本思想和优缺点。     

同轴波导空间合成放大器的建模与仿真

放大器设计中,高效率、高功率、宽带、高线性及低噪声是最重要的特性。同轴波导空间合成通过在同轴波导结构中直接合成大量MMIC放大器的输出功率,可以获得得良好的线性性能、良好的相位噪声、更宽的宽带性能、高的输出功率及更高的合成效率。但同轴波导空间合成功率放大器的结构复杂,完整3D电磁场仿真运算量大,不易实现。针对此,把放大器复杂结构分解成易于建模及仿真的单元,进行3D电磁场仿真,然后用电路仿真软件进行联合仿真来对设计进行较好的预测。     

基于声表面波技术实现微流体数字化

微流体的数字化是压电微流控芯片进行微流分析的前提,提出了采用声表面波(SAW)实现微流体数 字化的方法.在128°YX-LiNbO3基片上研制了中心频率为27.7 MHz的叉指换能器,在压电基片上方固定一细针,它经由Teflon软管与注射泵相连,注射泵提供恒定流量的微流体到达细针孔端并聚集,当聚集的微流体高度达到细针孔端与压电基片间距时,叉指换能器激发的声表面波驱动微流体实现微流体数字化.提出了计算细针孔端与压电基片间距的方法和微流体实现数字化的条件.以水为实验对象进行数字化实验,结果表明,声表面波作用下能实现微流体数字化,为压电微流控芯片提供了一种新的微流体引入方法.