Features and Prototypes of HTS High Q Resonant Circuit

High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and experimental approaches have proceeded for the concept verification. This paper presents the theory about this high Q resonant circuit. The operation principle of the circuit is described. A practical prototype for HTS high voltage generation is also demonstrated. The experiment result shows that very high voltages can be achieved by the developed method using HTS technology.

ANALYSIS OF ZERO-VOLTAGE QUASI-RESONANT BOOST DC-DC CONVERTER

The zero-voltage quasi-resonant boost switching DC-DC converter has been inves-tigated by using the time averaging equivalent circuit approach of periodically switching linearnetworks.The DC steady state and AC small signal characteristics of the converter are also given.

Quantum fluctuations of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling

Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics （TFD）, the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.

Novel method to measure unloaded quality factor of resonant cavities at room temperature

We demonstrated a novel method to measure the unloaded quality factor(Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency,not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of^100,000, obtaining good agreement between the measured and theoretical results.

Imaging changes in neural circuits in patients with depression using 1 H-magnetic resonance spectroscopy and diffusion tensor imaging

1 H-magnetic resonance spectroscopy imaging and diffusion tensor imaging were performed in 19 patients with mild depression and in 13 controls.The mean age of the patients was 31 years.The mean Hamilton depression score of the patients was 22.5±13.2.N-acetylaspartate,choline and creatine concentrations and the average diffusion coefficient and fractional anisotropy values were measured in the bilateral hippocampus,striatum,thalamus and prefrontal deep white matter. Compared with the control group,the mild depressed patients had：（1）a higher choline/creatine ratio and a negative correlation between the choline/creatine ratio and the average diffusion coefficient in the hippocampus;（2）a lower choline/creatine ratio and a higher fractional anisotropy in the striatum;（3）a lower fractional anisotropy and a positive correlation between the fractional anisotropy and the choline/creatine ratio in the prefrontal deep white matter;and（4）a higher average diffusion coefficient and a positive correlation between the choline/creatine ratio and the N-acetylaspartate/creatine ratio in the thalamus,as well as positive correlation between the choline/creatine ratio and Hamilton depression scores.These data suggest evidence of abnormal connectivity in neurofibrotic microstructures and abnormal metabolic alterations in the limbic-cortical-striatal-pallidal-thalamic neural circuit in patients with mild depression.

Coupled Electromagnetic Circuits and Their Connection to Quantum Mechanical Resonance Interactions and Biorhythms

The existence of specific biorhythms and the role of geomagnetic and/or solar magnetic activities are well-established by appropriate correlations in chronobiology. From a physical viewpoint, there are two different accesses to biorhythms to set up connections to molecular processes: quantum mechanical perturbation theoretical methods and their resonance dominators to characterize specific interactions between constituents. These methods permit the treatment of molecular processes by circuits with characteristic resonances and “beat-frequencies”, which result from primarily fast physical processes. As examples, the tunneling processes between DNA base pairs (H bonds), the ATP decomposition and the irradiation of tumor cells are accounted for.

Complete eigenmode analysis of a ladder-type multiple-gap resonant cavity

A theoretical model is developed for calculating the eigenmodes of the multi-gap resonant cavity. The structure of concern is a kind of ladder-type circuit, offering the advantages of easy fabrication, high characteristic impedance （R/Q）, and thermal capacity in the millimeter wave to THz regime. The eigenfunction expansion method is used to establish the field expressions for the gaps and the coupling region. Then, the match conditions at the interface are employed, which leads to a group of complicate boundary equations in the form of an infinite series. To facilitate the mathematical treatments and perform a highly efficient calculation, these boundary equations are transformed into the algebraic forms through the matrix representations. Finally, the concise dispersion equation is obtained. The roots of the dispersion equation include both the axial modes in the gaps, which include the fundamental and the high-order modes, and the cavity modes in the coupling region. Extensive numerical results are presented and the behaviors of the multi-gap resonant cavity are examined.

SWITCHING CHARACTERISTICS AND ANALYSIS OF RESONANT TUNNELING DIODES

Resonant tunneling diode （RTD） of AlAs/InGaAs/AlAs double barrier-single well structure was designed and fabricated. The devices showed current-voltage characteristics with peak-valley current ratio of 4 ： 1 at room temperature. The scattering parameter of RTD was measured by using an HP8510（C） network analyzer. Equivalent circuit parameters were obtained by curve fitting and optimized. The RTD switching time was estimated using the measured capacitance and average negative differential resistance. The minimum rise time of the sample was estimated to be 21 ps.

基于MATLAB GUI的交流电路频率特性仿真教学平台设计

为了使学生更加直观地理解交流电路中的频率特性,构建了一种基于MATLAB GUI的交流电路频率特性仿真教学平台。该仿真平台包括RC滤波电路和RLC谐振电路两个模块,其中RC滤波电路能够实现低通滤波、高通滤波和带通滤波电路频率特性的仿真研究,RLC谐振电路能够实现串联谐振和并联谐振电路频率特性的仿真研究。借助该仿真平台,只需手动输入电路元件参数,就能获得各交流电路的幅频和相频特性曲线,最后将源程序封装成.exe文件。该仿真平台操作简单,便于任课教师和学生使用,能够显著地提高课堂教学质量。

基于等效电路模型的超声波电机串联谐振频率识别方法

在超声波电机运行过程中,由于负载、温升等因素的影响,电机的串联谐振频率会发生漂移。为了对电机进行精确控制,需要准确识别并跟踪电机的串联谐振频率。基于超声波电机的Butterworth-Van Dyke(BVD)等效电路模型,提出电机的串联谐振频率识别方法。利用电机端电压和端电流作为反馈信号,对反馈信号进行处理得到差分电压,进而得到电机端电压与差分电压的相位差,并分析了该相位差与串联谐振频率的关系。在此基础上,设计了相应的电路实现方案,制作了电路实物,采用所提出的方法对样机的串联谐振频率进行识别,并用阻抗分析仪测量了样机的串联谐振频率。结果表明:利用所提出的方法识别得到的串联谐振频率与试验测量得到的串联谐振频率相吻合,证明所提出的超声波电机串联谐振频率识别方法的准确性。

无线电能传输系统全桥逆变器性能优化研究

针对无线电能传输系统中全桥逆变器开关管的开通和关断存在振铃,能量传输波形纹波大,导致逆变器温升大和工作不稳定的问题,进行了电路建模分析,开展了全桥逆变器性能优化研究。首先,对逆变器开关管驱动电路进行了简化,建立了RLC串联谐振电路模型,分析了驱动电路结构参数对逆变器性能的影响规律,得出了优化方法;其次,分析了逆变器纹波大的问题,给出了优化方法;最后,搭建了300 W无线电能传输系统并进行实验。实验结果验证了优化方法的正确性和有效性,逆变器性能得到了改善,温升得到了有效控制,系统传输效率提高了5.3%,整机效率达到了89.3%。

基于LC谐振的半桥式高压除尘电源研究与设计

随着环保意识的加强,人们对各种工业尾气的排放要求越来越严,给厂矿企业带来了很大压力,针对该情况,研制一种可以产生高电压、小电流的高压除尘电源.设计了电源的LC谐振主电路和控制电路、保护电路,保证电源工作的安全性和可靠性.通过实验验证了电源具有工作频率范围宽,电压调节宽度大等特点,电源实用性强,具有广泛的推广应用价值.

谐振电路品质因数的计算方法

品质因数是定量衡量谐振电路固有特性的重要参数,由电路的拓扑结构和元件参数决定。采用解析公式法、洛伦兹曲线拟合法和本征值数值计算三种独立的方法,定量对比了简单RLC串联谐振电路和复杂耦合谐振电路的品质因数及相对误差,讨论了这三种计算方法的优缺点和适用条件。拓展了现有教学中复杂谐振电路品质因数的教学内容,能够更好地满足实际的工程应用需求。

电路参数对RLC串联谐振电路特性影响的实验研究

由于谐振电路具有良好的选择性,在通信与电子技术中得到了广泛的应用,串联谐振时电感电压或电容电压大于激励电压的现象在无线电通信技术领域获得了有效的应用。本文采用实验方法,通过保持电阻、电感不变,改变电容;保持电阻、电容不变,改变电感;保持电感、电容不变,改变电阻三种方式,研究了电容、电感、电阻等电路参数对RLC串联谐振电路特性的影响,得到电路谐振时谐振频率、通频带宽度、电感线圈等效电阻、品质因数随电感、电容、电阻变化的规律及不同元件参数对品质因数影响的不同机理。

基于LC并联谐振的轴向自感式位移传感器设计

为了满足磁悬浮轴承面向更高精度的发展需求,提出基于LC并联谐振的轴向自感式位移传感器.通过增大谐振回路的等效电感变化率,提高传感器的灵敏度.分析传感器的工作原理.通过有限元仿真,研究传感器设计参数与灵敏度之间的关系.设计传感器的测量电路,结合有限元仿真和数值仿真,分析LC并联谐振对传感器灵敏度的影响.搭建实验台,对传感器的静态性能进行测试.结果表明,相对于传统的位移传感器,提出的传感器具有更高的灵敏度与更低的线性度.

超声手术刀声学系统设计和实验

为兼顾阶梯型变幅杆的高放大系数以及曲线过渡变幅杆突变截面处的高疲劳强度,提出了一种最速曲线过渡段的复合变幅杆,并对装配有该变幅杆的超声刀声学系统进行一系列实验。首先,基于等效电路法,设计了夹心式压电换能器和最速曲线型变幅杆的基本结构。在此基础上,结合超声刀的工作条件和材料特性,对换能器-变幅杆基本结构进行精确设计。然后,利用有限元法和实验法获取了换能器纵振频率以及频率响应曲线,证明了该文所设计换能器的有效性。最后,对所设计的换能器进行了一系列测试。结果表明:应用最速曲线的超声刀换能器谐振频率与输出端振幅与设计目标、仿真结果相吻合,连接负载后凝血,切割效果良好,满足设计需求。

电气化铁路“车-网”系统串/并联双模式宽频谐波扰动产生装置设计与测量方法

精确测量动车组与电力机车(简称机车)四象限变流器(four-quadrant converter,4QC)和牵引网的宽频带阻抗特性是识别电气化铁路“车-网”系统振荡和不稳定问题的重要途径。然而,已有研究采用单一电压/电流扰动注入方式对牵引网或机车4QC阻抗进行测量,可能造成部分谐波扰动流向非目标测量对象,导致被测对象的谐波扰动信噪比低,影响阻抗测量精度。因此,该文提出一种适用于电气化铁路“车-网”联合系统的串/并联双模式宽频谐波扰动产生装置与阻抗测量方法,装置具有电压和电流两种工作模式,可以发出频带为1~3000Hz的宽频谐波扰动。扰动产生装置拓扑主要由多绕组降压变压器、谐波功率放大单元、并联LC谐振电路和反串联绝缘栅双极晶体管(insulated gate bipolar transistor,IGBT)模块等部分构成,结合双闭环dq解耦控制和载波移相开环脉宽调制(pulse-width modulation,PWM)控制策略,实现频带双边可控、幅值可控且分布均匀的大功率谐波扰动输出。最后,利用MATLAB/Simulink仿真和RT-Lab硬件在环实验验证该文串/并联双模式宽频谐波扰动产生装置设计方案及阻抗测量方法的正确性与有效性。

新型并联谐振直流环节软开关逆变器改进调制策略

针对新型并联谐振直流环节软开关逆变器的辅助电路运行过程中电流应力高、导通损耗大的问题,提出一种基于不连续的脉冲宽度调制且采用斜率正负交替锯齿载波的改进调制策略。与原调制策略相比,首先,该文所提调制策略在保留辅助电路动作频率最小化优点的基础上,不仅实现了全部开关管的软开关,而且将第二辅助开关管的电流应力降为谐振电流峰值。然后,通过合理的参数设计,进一步降低辅助电路电流应力,从而减少辅助电路损耗。然后,根据所提调制策略分析工作原理、对比不同文献、规划参数设计、进行损耗分析。最后,使用SiC MOSFET制作一台5 kW/40 kHz通用样机,通过实验验证所提调制策略对原拓扑效率提升与电流应力降低的有效性。

电路及谐振子参数对YIG调谐振荡器相位噪声的影响

利用单一变量法,详细分析了某型YIG调谐振荡器不同电路参数(如基极反馈电感、负压电阻等)及谐振子参数(耦合环大小、小球饱和磁化强度等)对振荡器相位噪声的影响。结果表明,振荡器相位噪声随基极反馈电感的增大而增高,高频端的相位噪声相对低频端随负压电阻的增大改善更大;而对于YIG小球铁磁共振线宽ΔH,相对于高频端来说,相位噪声随ΔH的增大在低频端增高更多。总之,降低YIG调谐振荡器的相位噪声是根据各指标需求综合优化振荡器电路各参数的结果。

一种三通道三电平宽电压范围LLC谐振变换器

为解决传统LLC谐振变换器在光储系统等宽电压范围应用中存在整体效率低和开关频率范围宽等问题,提出一种三通道三电平宽电压范围LLC谐振变换器。该变换器具有双通道和三通道两种工作模式,通过组合不同模式下的增益实现宽输出电压范围。变换器能在全电压范围内实现软开关,工作于固定开关频率,具有参数与磁性元件设计简单等优点。详细分析变换器各种工作模式的原理与增益特性,并明确变换器实现ZVS的条件。最终基于GaN开关器件设计并搭建一台输入电压200 V、输出电压5~20 V、最大功率200 W的实验样机,验证所提拓扑的可行性与理论分析的正确性。