水下甚低频导航磁场接收天线设计

通过分析 Alpha 甚低频信号空气—海水跨介质及水下传播规律,重点研究了影响水下磁场天线接收性能的主要噪声源,并给出相应解决措施,提出了甚低频磁场接收天线的设计方案,经测试验证具备水下 20 m 接收甚低频导航信号的能力和可行性。     

电磁屏蔽室屏蔽等级和测量方法研究

电磁屏蔽室的屏蔽效能检测是衡量和判定屏蔽室等级的主要手段,因此正确选定其依据的屏蔽等级和测量方法的标准非常重要。文中对现行电磁屏蔽室屏蔽效能等级和测量方法的相关标准进行了梳理和对比,为在实际测量和确定屏蔽室等级时正确选定恰当的标准提出了可供参考的意见。另外结合工程实际,对屏蔽室单点与多点接地、绝缘、屏蔽门的设置等问题进行了讨论。     

单脉冲平面波以不同方向入射时开孔屏蔽室内的耦合场研究

采用时域有限差分(FDTD)法计算了开孔屏蔽室对单脉冲平面波的耦合,取得了与实测波形一致的结果.计算结果表明:若入射波传播方向垂直于开孔面,则屏蔽室内的耦合场仅取决于屏蔽腔体的谐振特性;若入射波传播方向平行于开孔面,则屏蔽室内的耦合场为具有源特征的低频分量与屏蔽室内的高频谐振波分量组成.     

屏蔽室接地线对屏蔽效能和信号泄漏的影响

文章主要介绍屏蔽室的接地问题,通过大量实验得出以下结论:①单点接地的屏蔽效能优于多点接地。②接地电阻大小对屏蔽室屏蔽效能没有影响。③接地线的长短对屏蔽效能影响不明显,而对信号泄漏有影响。④屏蔽接地线比裸露接地线信号泄漏小。     

倒相式音箱的理论与设计研究

本文利用倒相式音箱等效电路图，介绍了倒相音箱的工作原理及设计方法，设计了一套高保真音箱并介绍了调试方法和进行了听音评介。     

信息技术设备的外壳开孔设计

介绍了GB4943-2001《信息技术设备的安全》中的设备外壳开孔设计的目的和原则,分析和探讨了结构设计时的常见问题、具体解决措施以及检验方法。     

甚低频低噪声放大器的设计与测量

为解决深水甚低频无线电接收中微弱通信信号难以检测的问题,设计具有优秀噪声性能的甚低频低噪声前置放大器。通过对放大器噪声匹配问题的深入分析,重点讨论了直流工作点选择、输入阻抗匹配、复合电磁屏蔽结构等关键技术点,大大降低放大器的噪声系数。考虑到放大器噪声测量的特殊困难,设计一套完整的测量方案和实施步骤。测试结果表明该低噪声放大器噪声系数达到1.71dB,比经典放大器提高至少1.5dB。     

关于迷你音箱设计的讨论

从迷你音箱的部件功能分析开始,对迷你音箱产品设计提出了＂能＂、＂形＂、＂神＂三方面的设计原则。这对迷你音箱产品设计是有意义的。     

小型化微波悬置屏蔽微带线滤波器的设计

本文给出了悬置屏蔽微带线交指滤波器的设计公式，并成功的研制了Ｘ线段小型化悬置屏蔽微带线交指滤波器，实验结果和理论计算吻合得很好。     

内屏蔽铁路数字信号电缆的设计与制造

主要介绍了内屏蔽铁路数字信号电缆的设计、生产工艺要点，并结合生产实践讨论了如何进行质量控制。     

剧院扩声设计中的音箱摆位

对于固定扩声系统的剧院,在设计时会面临音箱位置的布局问题。从音箱自身的角度来看,音箱的布局受两个方面因素的影响：单只音箱的指向性及辐射范围;多只音箱的组合结果。结合这两个方面的因素进行考虑,探讨在实际剧院扩声设计中音箱布置的优选法。     

屏蔽室和半电波暗室设计施工的若干问题

介绍了屏蔽室和半电波暗室在设计和施工中需要注意的一些问题,例如:总体布局、供电照明、接地、通风、接口板、吸波材料选用、使用维护等.     

光伏系统DC/DC变换器设计与仿真

本次研修主要针对整个光伏发电系统前端的DC/DC转换器部分进行研究、设计和仿真。此部分不仅要根据设计要求设计选择合理的占空比和元件参数,完成DC/DC变换,还需要考虑最大能量跟踪控制,以保证最大可能的利用能源,提高系统效率。     

农村有线广播用音箱的设计

本文介绍了有线广播用音箱的设计,对动圈扬声器的基本原理与特性及动圈式扬声器的选择,作了深入的分析,对今后研制和生产高质量的音箱很有参考价值。     

Electromagnetic-Wave Propagation in the Shielded Ring Line

A theoretical analysis is presented of a periodic structure consisting of equally spaced perfectly conducting rings. The dispersion relation satisfied by the Werent modes of the shielded ring line is determined. This analysis shows that cylindrically symmetric modes identical with those of smooth guides and hybrid modes can travel in this periodical structure. The asymptotic values of the dispersion relation show the different properties of these hybrid modes. The EH/sub n1/ modes can be slow, fast, or can travel at light velocity according to the frequency. The EH/sub nq/ (q > 1) modes are fast modes and exchange their cutoff frequencies for particular values of the geometrical parameters of the structure. These theoretical predictions are verified experimentally by recording the dispersion characteristics of the first modes. For deflecting radio-frequency structures, the fundamental EH/sub 11/ mode is interesting. This deflection constant is measured on a /spl pi/ / 2 wave structure.     

New Technique for the Determination of the Integrity of Shielded Enclosures by the Measurement of the Perpendicular Magnetic Field

A solution of electromagnetic field equations with appropriate boundary conditions shows that at the surface of a material with infinite conductivity, no parallel electric field or perpendicular magnetic field exists. As conductivity decreases, there are large relative increases in the parallel electric field and perpendicular magnetic field at the surface. A reduction in permeability lowers the parallel electric field while increasing the perpendicular magnetic field. For most practical shielded enclosures of room size, the shielding effectiveness is determined largely by the quality of the seams between panels, along door edges, or filter mountings. Hence an investigation is presented of results of an evaluation of a method developed by the government for finding faults in a shielded enclosure by detecting changes in the perpendicular component of magnetic field along the surface of the conducting wall emphasizing continuity of all types of seams of shielded enclosures.     

MLCC在DC/DC变换器中的应用和优化设计

通过分析电容器的寄生效应和频率特性,研究电容器等效串联电阻对DC/DC变换器电性能和稳定性的影响;明确了多层陶瓷电容器(MLCC)在DC/DC变换器应用中与其他种类电容器的不同之处;并对多层陶瓷电容器的优化设计方法进行探讨,用具体电路说明了优化设计过程。     

Charge and Potential Distributions in Shielded Striplines

A new method is presented for calculating the charge and potential distribution in shielded microstrip lines with stratified dielectric fillings. The boundary value problem associated with this structure is formulated in a rigorous manner and the solution is constructed by an extension of the function-theoretic technique. Several advantages of this method are pointed out. The most important of these is its numerical efficiency. Numerical results are presented for charge and potential distributions for several choices of design parameters. The characteristic impedance and the guide wavelength are obtained from the knowledge of the charge distribution. Comparisons are made with the published data and the agreement is found to be very satisfactory.     

一种多模式降压型DC-DC变换器的分析与设计

为提高轻载下DC-DC变换器的效率,设计了一种降压型多模式DC-DC变换器控制芯片.其特点是在不同负载条件下采用不同的工作模式:在重、中载条件下采用脉宽调制(PWM),轻载条件下采用Burst调制,从而明显提高轻载条件下的效率.同时,采用片上集成功率开关管和同步整流管,提高了功率密度和变换器的效率.该芯片采用BCD 1.5 μm工艺实现.仿真结果表明,在重载和轻载条件下,变换器效率分别达到90%和80%以上.