宽频天线罩结构设计及制备工艺进展

天线罩是保护罩内各种仪器在恶劣环境条件下能够正常工作的一种设施,现代战争对天线罩的宽频化提出了越来越高的要求.在简述宽频天线罩设计原理和方法的基础之上,着重对国内外宽频天线罩的结构设计及工艺实现研究现状进行了综述,指出了我国与国外的差距及宽频天线罩的发展方向.     

软磁高频测量仪的校准方法研究

本文提取并分析了软磁高频测量仪的次级电压、初级电流的整周期瞬时点,并使用宽频多功能数字表,宽频阻抗分析仪测量其次级电压、初级电流、相角等电参数,从而实现了软磁高频测量仪磁参量的校准和量值溯源.     

一款透明柔性超材料宽频微波吸收器

超材料作为一种新型人工复合材料,因其独特的电磁特性,已成为物理学、材料学和电磁学界的研究热点.本文提出了一款兼具微波宽频吸收和透明、柔性特点的超材料.该反射型超材料共3层,分别为周期单元吸波层、介质基板和反射底板.基于阻抗匹配理论推导的吸波层阻抗匹配曲线,为宽频吸波优化设计提供了准确、高效的理论指导.仿真结果表明,当超...     

宽频段雷达表面波衰减特征规律研究

目标物体上表面波的衰减吸收对目标的隐身起到很大的作用.研究了雷达吸波涂层对宽频段雷达表面波衰减吸收的规律以及频率选择表面与吸波涂层相结合的复合吸波涂层对宽频段表面波衰减吸收的规律.实验结果表明,低厚度的雷达吸波涂层就可以实现高频表面波的强衰减吸收,而频率选择表面与低厚度雷达吸波涂层相结合的复合涂层与雷达吸波涂层共同交替使用可以实现宽频段表面波的强衰减吸收,有望实现目标物体在宽频段范围内的高性能均衡雷达隐身.     

轴流叶轮尾涡脱落宽频噪声计算模型研究

对低速轴流风机尾涡宽频噪声的计算模型进行研究,提出了叶片尾涡脱落噪声声功率与掠向角余弦值的五次方成正比的结论,基于高斯分布函数建立尾涡宽频脱落噪声频谱的计算方法,并对以上结论和计算方法进行了实验验证.     

高模态密度结构宽频振动分析的小波有限元方法实现

高模态密度结构的宽频振动分析问题是声振分析领域内关注的重点问题之一，可实现宽频振动预测的数值分析方法是该领域内重要的研究内容，有效的宽频振动数值分析方法应在低频至高频域可同时提供精准的数值解。然而，由于明显的耗散误差和计算成本过高导致传统有限元方法(traditional finite element method, TFEM)在对高模态密度结构进行宽频振动分析时，难以在高频域提供精准的数值解，致使无法实现有效的宽频振动分析。而小波有限元分析方法(wavelet finite element method, WFEM)在进行结构分析时具有潜在的求解效率优势，并且可大幅度降低耗散误差带来的影响。为此，本文首先构造了基于小波有限元理论进行宽频振动分析时的自耦合算法，并据此介绍了小波有限元方法对高模态密度结构进行宽频振动分析的架构，形成了宽频小波有限元分析方法(wide wavelet finite element method, WWFEM)。随后，采用数值分析研究方法，基于WWFEM对具有解析解的高模态密度薄板结构进行了宽频振动分析。最后，采用实验分析研究方法，预测了高模态密度结构在宽频...     

LC4铝合金阳极氧化膜的电参数特性与封孔性能研究

通过LCR宽频数字电桥直接测量LC4铝合金阳极氧化膜封孔前后的各种电参数变化,获得封孔信息,评价封孔质量;同时与测得的极化曲线、电化学交流阻抗谱进行对比,并结合FESEM和EDS对结果进行分析,结果表明,使用LCR宽频数字电桥评价铝合金阳极氧化膜的封孔质量,数据规律性强,操作简单易行.     

一款新型高准确度三相标准电能表的设计

本文设计的新型高精度三相标准表由信号处理模块、核心算法处理模块、基本功能模块和电源模块组成,三相多功能标准表基于低噪声模拟信号处理技术、宽频I/V、宽频V/V转换器技术、高精度高速数据采集技术、非整周期采样等信号处理技术,采用模拟输入通道独立的系统架构提高通道间隔离度,实现宽频率范围内高精度的电压、电流和功率测量功能。     

水声测量中的宽频技术应用方法

讨论一种基于宽频分析技术进行水声测量的方法——宽频噪声比较法。该方法从频域分析的角度出发,根据水声测量的实际需要,通过修改Welch法理论,以噪声为信号源,运用现代信号处理技术和数字化硬件系统,实现了水听器的宽频噪声比较法校准系统在宽频范围内的快速高效测量,是对单频脉冲比较法的一个重要补充。对于高Q值水声换能器的测量,避免信号瞬态效应的影响,采用宽频噪声技术更有优势。还对不同采样频率条件下的测量结果进行了比较．结果表明宽频噪声比较法采用脉冲序列内多个脉冲处理结果累加取平均的方法,可以降低对采样频率的要求,或者在设备最高采样频率一定条件下可以实现更高频率范围的测试。     

阻尼结构的宽频域振动及其辐射噪声的试验研究

本文讨论了两种阻尼性能差异较大的粘弹材料采用自由阻尼处理后对结构的宽频域振动响应及其噪声辐射的影响,从试验上考察了阻尼处理抑制平钢板和压筋板结构宽频振动响应和噪声辐射的有效性,比较了两种材料性能差异所带来的结构减振降噪效果的差异.结果表明,从减振降噪效果与阻尼材料性能所具有明显的依赖关系,对于工程设计和选用阻尼材料、阻尼材料的研究和开发也具有重要的指导意义.     

High power universal piezoelectric transformer.

This study describes a multilayer piezoelectric voltage and power transformer that has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed isolation gap. The electrode pattern is a ring/dot structure such that it uses radial mode for both input and output part that are built-in on the same ceramic disk. A prototype transformer was fabricated of size 15 x 2.78 mm2 having mass of 3.8 gm. In the step-down configuration at the constant output power of 6 W, the transformer characteristics across a 100 ohms load were found to be efficiency = 92%, gain = 0.21 input voltage = 110 Vrms, and temperature rise = 20 degrees C from the room temperature. In the step-up configuration at the constant output power of 5 W, the transformer characteristics across a 5 kohms load were found to be efficiency = 97%, gain = 9.5, input voltage = 16 Vrms, and temperature rise = 8 degrees C from the room temperature. A detailed equivalent circuit analysis of the transformer was done, and the results were found to be in excellent agreement with the experimental results.     

High power universal piezoelectric transformer

This study describes a multilayer piezoelectric voltage and power transformer that has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed isolation gap. The electrode pattern is a ring/dot structure such that it uses radial mode for both input and output part that are built-in on the same ceramic disk. A prototype transformer was fabricated of size 15 x 2.78 mm2 having mass of 3.8 gm. In the step-down configuration at the constant output power of 6 W, the transformer characteristics across a 100 omega load were found to be efficiency = 92%, gain = 0.21 input voltage = 110 V(rms), and temperature rise = 20 degrees C from the room temperature. In the step-up configuration at the constant output power of 5 W, the transformer characteristics across a 5 komega load were found to be efficiency = 97%, gain = 9.5, input voltage = 16 V(rms), and temperature rise = 8 degrees C from the room temperature. A detailed equivalent circuit analysis of the transformer was done, and the results were found to be in excellent agreement with the experimental results.     

三维连通网络陶瓷的电磁特性Ⅰ网络结构特性

分别用矩形谐振腔微扰法和波导传输线法测量了三维连通网络陶瓷及其同质粉末压片的电磁参数的温度特性和频率特性。结果表明，无论是磁性还是非磁性三维连通网络陶瓷在较宽的温度范围及整个测试频段内都比其同质粉末具有更大的电磁损耗，这种损耗差异来自它的三维连通网络结构特性，三维连通网络结构使材料电损耗的增加远远大于磁损耗的增加，三维网络陶瓷的这一特点，为研制兼具耐高温，宽频，廉价于一身的结构吸波材料提供了新思路。     

Ferromagnetic and microwave absorption properties of copper oxide/cobalt/carbon fiber multilayer film composites

The copper oxide/cobalt/carbon fiber multilayer film composites were synthesized by thermal oxidation route. In order to investigate the intrinsic reasons for microwave absorption properties of absorbers, the complex permittivity, complex permeability and the microwave absorption properties of composites were studied in the 1-18 GHz range. The strongest reflectivity loss (RL) of microwave absorber was further enhanced to − 42.7 dB (microwave absorption rate > 99.9%) at 10.8 GHz for a layer of 2.0 mm thickness, and the strong absorption (RL < − 10 dB) was obtained between 8.72 and 18 GHz for the thickness of 1.3-2.2 mm. The results indicated that the dielectric loss and magnetic loss led to the excellent microwave absorption property of CuO/Co/CF composites. It is believed to be ideal for making a lightweight, strong absorption and wide-frequency microwave absorbing material.     

Lamb Wave Phase Velocity Imaging of Concrete Plates with 2D Arrays

In the nondestructive evaluation of concrete structures, ultrasonic techniques are considered to be more capable than low-frequency techniques such as the impact-echo method. This is especially true with the recent development of ultrasonic transducers, synthetic apertures, and results in an image form, and because low-frequency techniques are usually limited in their evaluation to the frequency of one single resonant mode. With the aim of reducing this gap in capabilities, we present a 2D array and wide-frequency bandwidth technique for Lamb wave phase velocity imaging. The presentation involves a measurement on a newly cast concrete plate using a hammer and an accelerometer as an example. The key concept of the technique is the use of 2D arrays that record a full wave field response over a limited surface subdomain within the complete measurement domain. Through a discrete Fourier transform, a spectral estimate is obtained for the 2D array in the frequency-phase velocity domain. The variation of the phase velocity is then mapped using a stepwise movement of the 2D array within the complete measurement domain. With two different types of 2D arrays, the variation of the phase velocity for the A0 Lamb mode is mapped and displayed in a polar and image plot, and low variation is observed for both cases. This result verifies the expected condition of a homogenous material and plate thickness and, more importantly, highlights the potential of wide-frequency bandwidth techniques based on full wave field data.     

35kV母线电压不平衡原因探究

电网电压不平衡影响电能质量,由于运行方式改变后消弧线圈补偿度不够,导致35kV母线电压不平衡,分析了电压不平衡原因,总结了孝路接地、电压导感器高压高压熔丝熔断、铁磁谐振、电压互感器原因造成35kV母线电压不平衡,并提出了解决办法。     

高电压脉冲校准装置研究

为解决高电压脉冲的校准问题,对高电压脉冲的校准方法进行研究,并建立了一套脉冲校准装置。校准装置将高电压脉冲信号进行电压转换,变为脉冲小电压,通过数据采集系统,在频带范围10Hz~1kHz、电压范围1~1600V内,对脉冲电压的关键参数进行测量,得到高电压脉冲的电压幅度、脉冲频率、脉冲宽度、上升时间和下降时间。通过实验室标准仪器设备对高电压脉冲校准装置进行测试,其中脉冲幅度的测量误差为 0.02%~0.4%。     

交流电压源毫伏级量值准确测量的技术研究

基于电压比例和交直流转换技术,提出了一种对交流电压源的毫伏级量值进行准确测量的方法。采用自行研制的二进制级联结构电压比例装置和792A交直流转换标准,将被测交流电压源的毫伏级量值溯源至交流电压国家基准。实验采用替代测量法,通过选用不同电压比例和不同792A量程的组合,在55Hz~5kHz频率范围内,对1台5720A多功能校准源10~200mV范围的交流电压进行准确测量。结果表明,各毫伏级交流电压示值相对误差的绝对值均不超过±40μV/V,测量结果扩展不确定度优于80μV/V,满足交流电压源毫伏级量值溯源需求。     

空心阴极N2+等离子体放电电子温度的研究

利用双层辉光放电空心阴极效应，针对N2发射光谱相对强度的变化，采用SⅡ-Ⅳ型全息凹面光栅单色仪对各种工艺参数条件下的光谱进行测绘，获得一系列谱线及测量数据。通过玻尔兹曼方程式求得不同工艺条件下的N^2＋等离子体的电子温度。并分析了工件电压、源极电压和工作气压对电子温度的影响。结果表明：当工作气压和工件电压一定时，电子温度随源极电压的升高先减小后增大，最后又减小；当源电压一定时，电子温度随工件电压和工作气压的升高而明显减小，并且其减小幅度随源极电压的升高而逐渐降低；当工作气压一定时，工件电压的变化较源极电压的变化对电子温度的影响大。     

CMOS voltage reference with multiple outputs

A voltage reference with two outputs is presented. Both of them are insensitive to temperature, supply voltage and threshold voltage. One of the outputs is ~0.8 V, and the other one is ~0.38 V. For the output voltage of 0.8 V, this voltage variation because of supply voltage change from 2.0 to 3.5 V is plusmn0.66%, and because of temperature change from 0 to 80degC is plusmn52 ppm/degC. For the output voltage of 0.38 V, this voltage variation because of supply voltage change from 2.0 to 3.5 V is plusmn1.8%, and because of temperature change from 0 to 80degC is plusmn50 ppm/degC. The active area of the circuit is the supply voltage of 2 V is 0.8 mW.