应变超晶格中粒子运动的混沌不稳定性

利用Fourier展开,将应变超晶格中的粒子运动问题转化为多频激励的摆方程问题.用Melnikov方法和Lyapunov方法讨论了系统的稳定性,并对双频激励和单频激励进行了具体分析.结果表明,多频激励系统可通过奇阶次谐分叉进入混沌;当阻尼系数比较大或激励强度比较弱时系统是稳定的.     

系统频域分析的等效激励法和传递函数法

本文讨论了应用于线性时不变LTI系统的频域分析的两种技术。通过使用傅立叶变换FT的因果时域微分性质,给出了计算非零初始条件下因果激励的LTI系统响应的频域等效激励法;同时通过使用FT的非因果时域微分性质,给出了计算非因果激励的LTI系统响应的传递函数法。频域等效激励法和传递函数法分别是时域分析中的等效激励法和卷积法的频域版本,与时域等效激励法等效于时域卷积法一样,频域等效激励法也等效于传递函数法。     

X波段ISAR波形激励与失真补偿

论述一种X波段可扩充相控阵高分辨逆合成孔径雷达波形激励设计过程,分析了波形激励及其内单元电路的原理及指标分配方法,该波形激励采用调制器产生宽带线性调频(LFM)信号,且采用了倍频法提高激励带宽,突破了宽带信号产生及校正、宽带激励等宽带相控阵雷达系统的关键技术,解决了宽带、窄带系统的波形激励硬件共用问题,随整机进行外场实验,性能指标满足要求。     

企业设备绩效激励工作失效的原因研究与分析

从分析企业设备绩效激励失效的成因出发,借鉴和运用西方的激励理论,对设备绩效考核存在的问题进行了较为系统的研究与分析。对企业设备激励工作失效的原因进行较为详细而系统的分析且运用激励理论提出一种适合企业发展的新型激励机制。     

基于DAC的电阻层析成像系统激励信号源设计

为了解决传统电阻层析成像系统中激励信号源的问题,如电路的频率、幅值调节困难,电路设计模块复杂等问题,本文设计了一种新的电阻层析成像激励信号源产生系统。该系统利用微控器控制DAC芯片产生幅度频率可调的激励信号,该信号驱动精密电压/电流转换电路后产生双极性脉冲电流激励信号。研究表明,此系统可以满足使用要求,同时,在一定程度...     

大型民用飞机航电系统总线激励技术的研究

在对航电系统进行仿真验证时,需要按照接口控制文档(ICD)的要求发送和接收航电总线信号,通常都是根据具体型号飞机开发对应的航电总线激励系统,通用性和扩展性较差、开发周期长、成本较高。针对该问题,对大型民用飞机的主要航电总线如AFDX,ARINC429等航电总线的激励技术进行了研究,建立了航电总线激励系统的层次抽象模型和组织结构模型,设计了一套具有良好通用性和扩展性的航电总线激励系统,对该系统进行了测试,并给出了应用实例。结果表明,该系统具有良好的通用性和扩展性,为大型民用飞机航电系统的设计开发与集成验证提供了有力支撑。     

数字闭环加速度计带宽测试方法的研究

为了消除传统电模拟法引入的激励信号对力矩器驱动模块造成的影响,提出了一种在数字闭环加速度计系统反馈回路数模转换器输入端叠加一个激励信号来测试系统带宽的方法.通过对该方法的电激励模型进行分析,表明在带宽测试时系统反馈回路D/A输入端叠加激励信号可以等效为外界输入的加速度.搭建测试平台测试系统带宽,实验表明,用该方法测得的数字闭环加速度计系统带宽与传统机械振动法的测试结果相接近.该方法未增加其它电路,降低了系统的复杂度,消除了电模拟法外加激励信号源对力矩器驱动模块的影响.此外,该方法操作快速简单、便于在线测试,可满足大多数数字闭环加速度计的带宽测试要求.     

基于Python与腾讯乐享的本科生学习激励系统设计

为在“新冠”疫情线上教学背景下激发学生学习动力,文章利用信息化手段开发学习激励系统。阐述了使用成绩排名发放电子奖状的业务需求,分析了实现该系统的技术架构,利用Python中Pandas的数据分析能力、Tkinter的图形用户界面交互能力及腾讯乐享证书功能,联合打造了本科生学习激励系统,并在激励学生方面取得了良好效果。     

基于FPGA的导管式超声治疗系统设计

导管式超声在临床治疗上受到广泛关注。为实现方便、稳定的导管式超声激励系统,该文基于直接数字频率合成（DDS）技术在现场可编程门阵列（FPGA）上,设计了一款由上位机控制,波形、频率、占空比和电压幅值可灵活调节的导管式超声治疗系统,实现了脉冲激励信号的输出。测试表明,该系统人机交互方便,参数灵活,输出波形稳定,实现了对微型超声换能器的激励要求。用该系统对定制的超声换能器进行激励,实验测试了超声作用下仿体的温升情况。结果表明,该系统可有效激励超声换能器实现仿体内特定区域的热消融。     

一种机械式多稳态压电俘能器及其特性研究

该文提出了一种机械式非线性多稳态压电悬臂梁装置。利用集中参数法建立了系统的数学模型,分析系统势能可知,随着系统参数的变化,系统具有多稳态的特性;采用数值仿真法分析了在简谐激励和随机激励下系统的运动状态及俘能性能。结果表明,在简谐激励下,中低频环境中系统为三稳态时具有较好的俘能特性,高频环境中系统为单稳态时具有较好的俘能特性;在随机激励下,系统为三稳态时能在较低噪声强度下越过势垒而做大幅运动,从而输出较大电压;随着噪声强度增加,阱间运动发生的频率增加,输出电压也增加。     

Comparison of power deposition patterns produced by microwave andradio frequency cardiac ablation catheters

Transcatheter microwave and radio frequency (RF) electrodes are used for the ablative treatment of cardiac arrhythmias. The authors compare the power deposition patterns of microwave antennas and RF electrodes in saline phantoms of biological material. The decrease in power deposition as a function of distance away from the electrode is nearly exponential for RF and is considerably steeper than microwave antennas. These results suggest that microwave antennas are capable of heating a larger volume and thus creating a greater lesion than RF     

Design and characterization of a 10-Gb/s dual-drive Z-cut Ti:LiNbO/sub 3/ electrooptical modulator

The design and characterization of a dual-drive (DD) Z-cut Ti:LiNbO/sub 3/ electrooptical modulator are presented. Both the radio frequency (RF) electrode layout and the optical splitters and combiners of the Mach-Zehnder interferometer are investigated: The former is designed to avoid RF line crosstalk, whereas the latter is to obtain a low-loss longitudinally short splitter structure, able to properly separate the interferometer straight optical waveguide sections. First, the RF analysis is addressed, simulating the small-signal behavior of the DD coplanar waveguide electrode structure as a function of the central ground width. The performances of different splitter layouts (circular segment bends, sin-bends, and offset bends) are then investigated using the beam propagation method. Finally, experimental results on the electrical and optical test pattern structures, and of the DD Z-cut complete modulator, are discussed and compared with simulations.     

Piezoelectrically actuated RF MEMS DC contact switches with low voltage operation

In this paper, fully integrated radio frequency (RF) microelectromechanical system (MEMS) switches with piezoelectric actuation have been proposed, designed, fabricated, and characterized. At a very low operation voltage of 2.5V, reliable and reproducible operation of the fabricated switch was obtained. The proposed RF MEMS switch is comprised of a piezoelectric cantilever actuator with a floated contact electrode and isolated CPW transmission line suspended above the silicon substrate. The measured insertion loss and isolation of the fabricated piezoelectric switch are -0.22 dB and -42dB at a frequency of 2GHz, respectively.     

Independent control of ion density and ion bombardment energy in adual RF excitation plasma

A dual RF excited discharge is described. The dual RF excitation system provides a method to control the substrate self-bias without affecting the state of the discharge. The substrate can be RF-biased utilizing an appropriate excitation frequency and power significantly less than the plasma generating RF power. The substrate self-bias dependence on various system parameters, including substrate excitation frequency, pressure, plasma generating upper electrode RF power, substrate material, and process gas compositions, is described. For a simplified model, a linear relationship between self-bias and RF power is derived using the space-charge limited assumption. The effect of substrate bias on the thermal-oxide etch rate has been studied. The results show good correlation between the ion bombardment energy, i.e., the potential difference across the substrate dark space, and the SiO ₂ etch rate. The SiO₂ etch rate in a CF₄ plasma increases linearly with the ion bombardment energy, having a threshold etch energy of ~19 V     

射频波导激光器电极参数的测量

根据传输线理论,射频波导激光器的电极可近似为无损耗均匀传输线,采用扫频方法,可测量出射频波导激光器电极的重要参数,如特性阻抗、相移常数、相速、分布电感及分布电容等     

ANALYSIS OF DUAL FREQUENCY CONFINED CAPACITIVELY COUPLED PLASMA AT LOW POWER

Confined dual frequency hydrogen plasma discharge has been investigated with microwave interferometer method and radial profiles are taken by Abel inversion technique. Dual radio-frequency sources, operating at 27.12MHz and 1.94MHz, are coupled to each other through the plasma. 27.12MHz RF power is used to enhance plasma density and 1.94MHz power is used to enhance ion acceleration energy to the electrode. Radial density profiles has been taken for comparing the effects of low frequency source that the secondary RF source causes reduction in plasma density due to the sheath expansion. Instead radial density profile is assumed as flat by most of the models, there is about 2.5eV of potential drop occurs from centre to boundary at 40W of primary source power. It has been observed that increasing sheath width (increasing the secondary source power to primary source power) reduces the bulk plasma volume and makes potential profile flattening in y direction. While the high frequency power is dissipated by electrons in the bulk plasma; low frequency power is mostly dissipated by ions in the sheath region. Using both high and low frequency power, we may control plasma density and ion acceleration energy to the electrode simultaneously.     

Velocity-matching in millimeter wave integrated optic modulatorswith periodic electrodes

One method of increasing the efficiency of a high-frequency integrated optic modulator is to use a periodic electrode to repeatedly “correct” the phase mismatch that results from unequal RF and optical propagation velocities. The center frequency of such a modulator's passband can be determined analytically by expanding the traveling RF field in terms of space harmonics, and by then matching the phase velocity of the dominant space harmonic to the phase velocity of the optical carrier. The theory of space harmonic velocity-matching is presented for the simple case of periodic intermittent interaction and periodic phase reversal modulators having no back-reflections at electrode discontinuities. Velocity-matching with Bloch waves is then described for nonideal structures where significant back-reflections can occur. The measured modulation response for several 35-GHz periodic intermittent interaction modulators that were designed using these concepts is presented and compared with the theoretical predictions     

ICP等离子体刻蚀系统射频偏压的实验研究

对于上下电极双射频源的电感耦合(ICP)等离子体刻蚀设备的关键工艺参数--下电极射频偏压的变化特性进行了实验与物理定性分析.实验以氧气作为反应气体,采用可满足300mm硅晶片刻蚀的ICP刻蚀设备的射频系统进行实验数据测定.结果表明,下电极射频偏压与其他工艺参数在可适用的工艺窗口中(改变上下电极功率和气体压力)不再是平常认为的简单的比例关系,而是随着条件的改变,对应的趋势比例关系会发生转折性变化,这种变化在高上电极射频、低下电极射频功率和低气压的条件下很容易发生.     

一种L～E波段的混合型射频MEMS单刀双掷开关设计

针对传统RF MEMS单刀双掷(SPDT)开关应用存在频段低、插入损耗高、隔离度低等问题,设计了一种混合型SPDT开关,通过在一条通路上设置接触式开关和电容式开关,实现了在L～E频段下的低插入损耗和高隔离度。通过设计蛇形上电极结构,降低了上电极的弹性系数,进而降低开关上电极下拉所需的驱动电压。采用HFSS仿真软件对混合型SPDT开关的射频性能参数进行了优化,并利用COMSOL对开关的蛇形上电极进行应力-位移分析。仿真结果表明,在DC～90 GHz的频段下,SPDT开关的插入损耗小于1.5 dB@90 GHz,隔离度大于52 dB@67 GHz、29 dB@90 GHz。此开关适用于无线通信系统、雷达系统和仪器测量系统等对工作频段要求高的领域内。     

Analysis and characterization of traveling-wave electrode in electroabsorption modulator for radio-on-fiber application

Comparing with a lumped electroabsorption modulator (EAM), we show the merits of a long EAM with traveling-wave electrode with high radio-frequency (RF) gain that could be used in high-frequency analog application. By terminating the RF output port with the characteristic impedance of 30 /spl Omega/, the device exhibited a large enhancement of 6 dB above 10 GHz in the electrical-to-optical response and a wide fractional bandwidth as estimated from simulation. In addition, an input impedance matching circuit of stub embedded on the device chip was found to be very effective for improving RF characteristics in the narrow band of frequency.