探究如何利用谐振电路准确测量电容和电感

当正弦波信号源的输出达到某一频率时,RLC电路的电流达到最大值,即产生谐振现象.目前大多数实验主要是通过描绘RLC串并联电路的相频特性、幅频特性曲线来研究RLC电路的谐振现象,进一步测定谐振曲线、电路品质因数Q值等.那么,能不能利用RLC电路的谐振特性反过来测量电路中的电容和电感呢?为此,本文首先通过谐振电路理论推导得出测量电容及电感的实验原理,然后进行大量的实验探究和数据分析,得出了准确测量电容和电感的条件.     

RL-C并联谐振电路品质因数Q的简易推导

指出一般教材在介绍谐振电路品质因数中的不足，根据品质因数的能量定义，对RL—C并联谐振电路的品质因数进行了简单推导。     

RLC串联谐振电路实验的相关问题探讨

通过理论分析了串联谐振电路的谐振原理,探讨了RLC串联电路的谐振特性,包括谐振频率、谐振电压和品质因数.由于电感阻抗的存在对电路谐振特性造成了一定的影响,在实验中发现,谐振特性曲线比理论曲线更平坦,测量的品质因数Q值比理论值偏小.     

用研讨教学法进行RLC串联谐振实验教学

由于电阻器、电感器和电容器并非理想的电路元件,如果实验方法不当将造成较大的系统误差,使学生对RLC谐振理论与实验产生难解之惑。采用“研讨教学法”,引领学生分析讨论RLC串联实验电路的谐振原理,确定减小系统误差的实验方法,使学生更好地通过实验研究RLC串联谐振特性,并探讨实验中电感和电容的特性,培养学生分析解决实际问题的能力,并领悟RLC串联谐振实验的物理思想。     

损耗电阻对RLC串联谐振电路品质因数的修正

RLC串联谐振是大学物理实验的一个重要内容.实验中发现电路品质因数的实验值总是小于理论计算值.对电路中的损耗电阻进行了估算,并对品质因数的理论值进行了修正,从而有效地降低了实验相对误差.     

LRC串并联谐振电路的品质因数与电容和电感关系的实验研究

在LRC串并联谐振电路中,回路的谐振特性通常由回路中的品质因数决定,而回路中的品质因数又与回路中的电容、电感、电阻有关。本文通过实验的方法,对回路的品质因数与电容和电感的关系进行了研究。得出了在串并联谐振电路中电容和电感的合理取值范围。所得结论将为今后LRC谐振回路的选择和设计提供一定的参考。     

品质因数的多重内涵及其教学探讨

从正弦激励下线性二阶系统的微分方程出发,结合阻尼振子的受迫振动以及RLC串联、并联谐振电路等具体物理情境,剖析了品质因数Q在频率特性、能量转换以及系统各物理参数等多个层次上的内涵,进而探讨如何更好地为工科各专业学生讲授品质因数这一概念.     

串联谐振电路Q值的计算与意义

在实际电路中,即使是一个简单的线圈,不仅有电感,还有电阻,不能分割,但可以用集中的电感L与电阻R串联电路模型来表示.作为具有代表性的典型模型,经常研究电阻、电感、电容串联电路.1RLC串联电路的特点与谐振现象如图1所示是由电阻、电感和电容相串联所组成的RLC串联电路.在此电路中,电容和电感是储能元件,其中能量的转换是可逆的,而电阻是耗能元     

关于分数阶RL_α-C_β并联谐振品质因数Q的讨论

根据电路理论求得分数阶RL_α-C_β并联电路的导纳,以α=β、CR~2/L1为条件,求得电路谐振频率的简易表达式.在此基础上推导出了RL_α-C_β并联谐振电路品质因数的简易表达式,并对其进行了分析讨论.用MATLAB软件进行了仿真分析,理论分析和仿真分析基本吻合,从而找到了品质因数Q随元件参数及分数阶次数变化的规律.     

R取值对测量并联谐振频率的影响

采用测量电容两端电压最大值的方法来确定RLC并联谐振的谐振频率。发现在RLC电路中,电阻R值愈小,η（η=f实验/f理论）愈接近于1;并且当电阻取值一定时,电容C取值越小,测量越准确。最后给出了简化电路图,即R=0,此时R′=RL。     

外加载谐振腔的理论计算与分析

 通过建立外加载谐振腔的等效电路模型,给出了加载以后外加载谐振腔的频率、品质因数和间隙阻抗的解析计算公式,并使用电磁场模拟软件证明了计算结果的正确性。由计算和模拟结果显示,在使用谐振腔加载的方法降低品质因数的同时,还可以利用模式重叠进一步展宽频带。由等效电路模型分析了主腔和负载腔的品质因数、主腔和负载腔之间的频率差以及耦合口的大小对加载后谐振腔的品质因数和间隙阻抗的影响。     

Equivalent circuit for coil-patient interactions in magnetic resonance imaging

An equivalent circuit is presented which accurately models the performance of magnetic resonance imaging receiver coils used with conducting samples. Coil-sample interaction is determined by measuring either the complex impedance or the associated resonant frequency and quality factor when samples of different conductivity are placed in the coil. The equivalent circuit component values are obtained from these data using a global nonlinear least squares fit. This equivalent circuit contains a minimum number of components necessary for understanding and quantifying the detuning and losses caused by electric and magnetic field coupling with the sample.     

Ka波段分布作用速调管多间隙谐振腔研究

谐振腔作为速调管的高频互作用电路,其特性对速调管的功率、效率、增益和带宽等性能具有决定性影响。主要介绍了某Ka波段分布作用速调管谐振腔的设计过程:基于多间隙谐振腔理论,利用电磁仿真软件CST详细分析了谐振腔不同结构尺寸对特性参数,如品质因子、特性阻抗、耦合系数、有效特性阻抗的影响,优化得到谐振频率为35 GHz的五间隙谐振腔的物理结构模型,并给出互作用仿真结果,为Ka波段分布作用速调管设计及其高频注波互作用的计算提供重要的参考和依据。     

Investigations of thickness-shear mode elastic constant and damping of shunted piezoelectric materials with a coupling resonator

Shear-mode piezoelectric materials have been widely used to shunt the damping of vibrations where utilizing surface or interface shear stresses. The thick-shear mode(TSM) elastic constant and the mechanical loss factor can change correspondingly when piezoelectric materials are shunted to different electrical circuits. This phenomenon makes it possible to control the performance of a shear-mode piezoelectric damping system through designing the shunt circuit. However, due to the difficulties in directly measuring the TSM elastic constant and the mechanical loss factor of piezoelectric materials, the relationships between those parameters and the shunt circuits have rarely been investigated. In this paper, a coupling TSM electro–mechanical resonant system is proposed to indirectly measure the variations of the TSM elastic constant and the mechanical loss factor of piezoelectric materials. The main idea is to transform the variations of the TSM elastic constant and the mechanical loss factor into the changes of the easily observed resonant frequency and electrical quality factor of the coupling electro–mechanical resonator. Based on this model, the formular relationships are set up theoretically with Mason equivalent circuit method and they are validated with finite element(FE) analyses. Finally, a prototype of the coupling electro–mechanical resonator is fabricated with two shear-mode PZT5 A plates to investigate the TSM elastic constants and the mechanical loss factors of different circuit-shunted cases of the piezoelectric plate. Both the resonant frequency shifts and the bandwidth changes observed in experiments are in good consistence with the theoretical and FE analyses under the same shunt conditions. The proposed coupling resonator and the obtained relationships are validated with but not limited to PZT5 A.     

Simulation Investigation of Millimeter Wave Varactor-tuned Transmission Cavity-stabilized Oscillator

A new circuit configuration for millimeter wave varactor-tuned transmission cavity-stabilized oscillator has been proposed in this paper. Compared to conventional varactor-tuned reflection cavity-stabilized oscillator, in this configuration, a high quality factor transmission cavity directly coupled to varactor diode is employed to improve the performances of the oscillator. The operation frequency of this oscillator can be tuned by varying the resonant frequency of the transmission cavity through changing bias voltage of the varactor diode. An equivalent circuit model for the oscillator has been presented in order to theoretically investigate the performance characteristics of the oscillator. On the basis of this model, electrical tuning characteristics have been studied. Mode jumping phenomena during electrical tuning process have been analyzed for obtaining stable operations of the oscillator. The analytical formulae of quality factor and efficiency have been derived in terms of relevant circuit parameters. Particular emphasis has been paid on several circuit parameters which have a substantial impact on circuit performance. Some design considerations have been pointed out according to the simulation results, which are useful to the design and fabrication of this type of oscillators.     

左手介质对谐振腔谐振频率的影响

在谐振腔设计过程中, 谐振腔的品质因数以及谐振频率都是需要考虑的关键因素. 传统的方法是通过减小谐振腔的尺寸或者利用高次模来提高谐振腔的谐振频率, 但是由于两种方法都有其局限性, 导致设计结果并不理想. 通过理论计算与模拟仿真相结合的方法, 对影响谐振腔谐振频率的因素进行分析, 得出了填充介质的材料属性与谐振腔谐振频率的关系. 理论计算显示: 当用“左手介质”作为谐振腔的填充物质时, 可以在不改变谐振腔尺寸的基础上提高谐振频率. 高频结构仿真器(high frequency structure simulator)的仿真数据也证明了以上结果, 从而得出谐振腔的谐振频率可以不受谐振腔尺寸的限制. 相较于传统理论而言, 研究结论有进一步的发展, 为探索和设计新颖的谐振腔提供了理论依据.     

三间隙耦合腔输出回路的等效电路

 给出了三间隙耦合腔输出回路的等效电路,利用等效电路确定了谐振频率及间隙阻抗矩阵。从间隙阻抗出发,结合双间隙耦合腔输出回路探讨了模式重叠的机制,并将其应用于Ka波段的三间隙耦合腔输出回路。基于能量守恒的观点得到了三间隙耦合腔输出回路的互作用阻抗频率特性,从而调整电路参数,使所研究电路的3 dB带宽达到了4.48%。     

On the application of radio frequency voltages to ion traps via helical resonators

Ions confined using a Paul trap require a stable, high voltage and low noise radio frequency (RF) potential. We present a guide for the design and construction of a helical coil resonator for a desired frequency that maximises the quality factor for a set of experimental constraints. We provide an in-depth analysis of the system formed from a shielded helical coil and an ion trap by treating the system as a lumped element model. This allows us to predict the resonant frequency and quality factor in terms of the physical parameters of the resonator and the properties of the ion trap. We also compare theoretical predictions with experimental data for different resonators, and predict the voltage applied to the ion trap as a function of the Q factor, input power and the properties of the resonant circuit.     

采用单开关谐振电路的脉冲电源设计

谐振电路可以实现软开关,减小开关损耗,而广泛应用于电力电子领域。谐振电路工作在特定模式下可以产生脉冲形式电压,相较于其他脉冲发生器拓扑具有开关数量少、低开关损耗和低电磁干扰(EMI)的优点。谐振电路通常需要半桥或全桥转换器产生一个方波激励,本文提出了一种结合脉冲变压器和单开关谐振电路的脉冲电路,主电路只需使用一个半导体开关,便可通过谐振电路和脉冲变压器在副边得到高压脉冲,且可以实现零电流关断(ZCS)。对电路的工作过程进行了理论分析,并搭建了样机进行了带载实验。试验结果表明,在介质阻挡放电(DBD)负载上实现了频率为10~20 kHz、幅值为5~10 kV的正弦脉冲电压。该电路结构简单,成本低,安全可靠。     

Sisyphus effects in a microwave-excited flux-qubit resonator system

Sisyphus amplification, familiar from quantum optics, has recently been reported as a mechanism to explain the enhanced quality factor of a classical resonant (tank) circuit coupled to a superconducting flux qubit. Here we present data from a coupled system, comprising a quantum mechanical rf SQUID (flux qubit) reactively monitored by an ultrahigh quality factor noise driven rf resonator and excited by microwaves. The system exhibits enhancement of the tank-circuit resonance, bringing it significantly closer (within 1%) to the lasing limit, than previously reported results.