LC振荡器寄生振荡的分析和消除

振荡器在不需要的频率发生的寄生振荡(不一定是由寄生参数引起,在这里暂且称其为寄生振荡),对振荡器的设计与调试带来了很大的困扰。本文对寄生振荡进行理论了分析,并提出避免寄生振荡的措施。     

面泵浦钕玻璃激光器的液体涂层

大孔径钕玻璃激光放大器圆盘中寄生振荡问题最近受到相当大的注意。参考资料1和3计算了寄生振荡对最大增益和(或)钕玻璃圆盘孔径的限制并强调了抑制这些寄生振荡的要求。本文报导了能大大提高抑制钕玻璃圆盘中的寄生振荡的能力的一种包层液体的发展。     

广播发射机寄生振荡的产生与消除原理

寄生振荡对于广播发射机的安全稳定运行有着严重的危害,本文通过对寄生振荡的产生与危害进行了分析与描述,总结了检查和消除寄生振荡的原理与方法,对发射机的实际调试与维护有很强的理论与实际指导意义。     

电视发射机差转机寄生振荡的产生与排除

发射机差转机内存在寄生振荡而引起网状干扰。微弱的寄生振荡可以从扫频仪显示的频响曲线上看到，如有额外的频标点或使频响曲线长毛刺等；较为严重的寄生振荡使频响曲线无固定形状，扫频仪的扫频基线上跳；严重的寄生振荡会改变放大器的工作状态，有时无法将放大器的静态工作点调到标准值；更严重的寄生振荡往往会使阴流过荷，并通过电控系统自动将高压切断，使发射机差转机无法正常工作。１电子管功放的寄生振荡在米波段，即使电子管功放都采用栅地电路，但因工作频率很高，管子极间电容和引线电感所产生的反馈还是比较明显的，为了使电子…     

消除中波广播发射机寄生振荡的探讨

中波广播发射机产生寄生振荡可使发射信号失真，工作频率的输出功率和效率下降，播出质量变差。无论是中小功率还是大功率的发射机，寄生振荡容易损坏管子和零件，局部过压打火，使发射机工作不稳定。倘若出现强烈的寄生振荡，尤其是硬自激，将导致阻碍基频振荡的产生，进而烧坏播出设备。为了使广播设备能够正常运行，消除中波广播发射机的寄生振荡是一项十分重要的技术工作。１检查寄生振荡的方法在检查确定寄生振荡时可采用如下方法：（１）把小氖灯固定在长绝缘棒一端上，手握绝缘棒另一端，使氖灯触及电路中有电压之处，然后根据氖灯发…     

DF-100A型PSM短波广播发射机的防振措施

对寄生振荡产生的条件和原因进行了阐释,分析了DF-100A型PSM短波广播发射机在射频功率放大器中所采取的抑制各类寄生振荡的措施,说明了在技术维护工作中应注意的问题。     

含有多程室的多光程谐振腔的寄生振荡分析

讨论了用于同轴放电气体激光器的含多程室的多光程谐振腔的寄生振荡，分析了寄生振荡存在的条件，对激光输出的影响及克服办法     

可调谐TEA CO2序旬带激光放大中光栅对寄生振荡的抑制

本文讨论了可调谐TEA CO2序列带激光放大级中的寄生振荡的成因,提出了一种在放大级中旋转一闪耀光栅来抑制放大过程中产生的常规带寄生振荡的方法,经实验验证,结果表明该法有效可行。     

脉冲半导体泵浦掠入射Nd:YVO4板条振荡器储能优化

板条放大器中寄生振荡的存在严重影响了激光放大器的效率,降低了板条晶体的储能。为抑制掠入射板条寄生振荡、提高晶体储能,对掠入射板条放大器的增益介质Nd:YVO4晶体进行了表面处理。该处理用离子溅射的方法,对板条的上下两个梯形面和梯形长边所在的矩形面镀锗,抑制板条内部的寄生振荡。通过实验对镀锗和未镀锗板条振荡器的自由振荡输出和调Q输出特性进行了对比,镀锗板条振荡器在调Q下的阈值电流降低了15%,晶体的储能提高了86.9%;而两种板条在调Q条件下输出的光束质量、脉宽大小、光斑形状基本一致。实验结果表明,板条表面镀锗是抑制其内部寄生振荡、提高储能的有效方法。     

GZ—200—1型中波广播发射机的防振电路

本通过典型机型，对于调幅发射机寄生振荡做了较为详尽的阐述。     

Characterization of parasitic residual deposition on passivation layer in electroless nickel immersion gold process

The problem of parasitic residual deposition on the passivation layer in electroless deposition process is studied in this paper. The characterization analysis tools involved are focused ion beam (FIB), scanning electron microscopy (SEM), electron dispersive X-ray (EDX) and metallurgical interface analysis. Samples were identified as either good or bad prior to the characterization process via a high power microscope. A good sample is the one without parasitic deposition while a bad sample contains parasitic residual deposition on the passivation surface. Ultrasonic vibration has been able to remove the parasitic deposition and reveal crack presence on the passivation surfaces. Crack was found extended to the aluminum underneath that leads to the formation of the parasitic residual deposition. Additional sacrificial photoresist on top of passivation was able to eliminate this parasitic deposition.     

边缘负载FBAR谐振器有限元仿真分析

外部激励施加于薄膜体声波谐振器(FBAR)时会激发纵向与横向剪切的振动,引发能量损耗,为了减少寄生谐振,降低FBAR器件的工作损耗,提高器件的品质因数,故需要抑制横向剪切振动。该文采用有限元仿真法讨论了顶电极边缘负载参数对FBAR器件横向寄生的影响,并通过COMSOL仿真软件实现且制备了结构完整的谐振器。测试结果表明,负载结构可有效提升器件品质因数约10%。     

薄膜体声波谐振器有限元仿真与设计

为了抑制薄膜体声波谐振器的寄生谐振,建立了薄膜体声波谐振器的二、三维有限元模型。通过频率响应仿真,分析了不同电极结构的谐振器在中心频率处的振动位移分布情况和频率响应曲线,评估了不同电极结构对谐振器寄生振动的影响,并完成谐振器电极结构的优化设计,实现了谐振器寄生振动抑制。根据仿真优化结果表明,设计并制作了工作频率在1.873GHz的薄膜体声波谐振器,谐振器插入损耗0.7dB,无明显寄生谐振,对设计进行了验证。     

Parasitic noise on the output of a CW YAG:Nd+3laser

An experimental investigation was conducted to reduce the parasitic noise appearing on the output of a 6-W CW YAG:Nd⁺³laser. Initially, low-frequency fluctuations as high as 30 percent and relaxation oscillation bursts exceeding 80 percent of the CW power level were present. Low-frequency modulation was reduced by the addition of an active feedback loop to control lamp current. Relaxation oscillations were determined to be influenced by laser rod cooling, pump-lamp aging, vibration, and intracavity optical interface quality. At the conclusion of the program, low-power fluctuations and relaxation oscillation excursions did not exceed 2 percent.     

Optimal design of a tunable electromagnetic shunt damper for dynamic vibration absorber

Dynamic vibration absorber (DVA) is an effective device for suppressing resonant vibration of noisy machineries and structures. However, the optimum design of DVA requires precise tuning of the damping force in the DVA, which unfortunately is often not practical and prone to changes of working conditions. In this paper, a tunable electromagnetic shunt damper (EMSD) with different opposing magnet pairs configurations is tested for the optimum design of DVA. The optimum magnet pairs configuration is derived to provide the maximum damping force in the DVA. Both simulations and experiments are conducted to verify the damping coefficient variation with the number of magnet pairs in the EMSD. The experimental optimization procedure of the DVA is designed according to the fixed-points theory. The damping force generated by the EMSD can be readily adjusted by varying the external resistance of the EMSD. This is the first experimental implementation report of the optimization procedure described in the fixed-points theory. The proposed tunable EMSD can conveniently allow for onsite optimal tuning of DVA. The proposed design methodology provides fine tuning of the damping coefficient of EMSD to achieve robust optimal DVA performance, even when subject to changes of external parasitic damping.     

Packaging technology for a 10-Gb/s photoreceiver module

We designed a 10-Gb/s photoreceiver module integrating a flip-chip avalanche photodiode (APD), a Si-preamplifier IC, and a slant-ended fiber (SEF). Flip-chip bonding minimizes parasitic reactances in the interconnect between the photodiode and the preamplifier IC. The optical coupling system consists of a slant-ended fiber and a microlens monolithically fabricated on the photodiode. This gives a flat IC-package assembly, which enables stripline interfaces to extract high-speed signals, increases misalignment tolerances, and lowers package height. Tolerances of over ±9 μm were obtained in every direction, which matched our theoretical predictions. To attach and hermetically seal the optical coupling, the fiber ferrule was directly laser-welded to the package wall with a double ring structure. The module withstood shock and vibration tests and had a 10-GHz bandwidth and -23-dBm minimum photosensitivity at 10 Gb/s     

Dynamics of Ultrasonic Transducer System for Thermosonic Flip Chip Bonding

Thermosonic flip chip bonding is used in certain fine pitch IC packaging for its unique features. By using this bonding process in this paper, 1 mm$, times ,$1 mm chip with 8 gold bumps has been bonded onto a silver-coated substrate. Dynamical properties of transducer system, which is the key component for providing the ultrasonic energy, have been investigated using finite element model (FEM) and measurement using impedance analyzer and laser doppler vibrometer (LDV). The simulation results show that the ultrasonic transducer vibrates by coupling with all excited modes, therefore resulting in complicated motions during bonding. The third axial mode, which includes 1.5 wavelengths and 3 nodes, is the dominant working vibration. However, this axial mode is severely disturbed by undesirable non-axial modes such as flexural modes. There are some other unwanted parasitic modes close to dominant mode. Measured velocities of the transducer horn show that the system vibrates under several modes simultaneously. The impedance measurements reveal additional frequencies overlapping the working frequency. All non-axial modes of the ultrasonic transducer disturb the bonding process and degrade the bonding quality. A subtle control is needed to obtain unique axial mode and stable vibration for high bonding quality.      

寄生电感对碳化硅MOSFET开关特性的影响

相比于传统的Si IGBT功率器件而言,碳化硅MOSFET可达到更高的开关频率、更高的工作温度以及更低的功率损耗.然而,快速的暂态过程使开关性能对回路的寄生参数更加敏感.因此,为了评估寄生电感对碳化硅MOSFET开关性能的影响,基于回路电感的概念,将栅极回路寄生电感、功率回路寄生电感以及共源极寄生电感等效成3个集总电感,并且从关断过电压、开通过电流及开关损耗等3个方面,对这3个电感对SiC MOSFET开关性能的影响进行了系统的对比研究.研究表明:共源极寄生电感对开关的影响最大,功率回路寄生电感次之,而栅极回路寄生电感影响最小.最后,基于实验分析结果,为高速开关电路的布局提出了一些值得借鉴的意见.     

精确区分器件和互连寄生电阻电容的方法研究

随着器件线宽的不断缩小,在集成电路仿真中互连线延迟所占的比重逐渐变大,而MOSFET延迟所占的比重慢慢减小,这就意味着互连的寄生电阻电容对延迟的影响越来越大.研究了如何区分并计算器件部分和互连部分的寄生电阻电容.其中区分本地互连寄生电阻电容和器件电阻电容是关键.以90 nm器件为例,通过提取不同部分的寄生电阻电容,对环形振荡器进行延迟仿真,得到了它们对延迟的影响.通过不同的测试结构达到精确计算器件寄生电阻电容的目的,最终实现了对电路的精确仿真.