耦合增强型“巨”字形左手材料磁谐振器的设计

磁谐振器与电谐振器组合能够实现同时具有负介电常数和负磁导率的左手材料,左手材料磁谐振器的设计对于设计新型左手材料具有重要的意义。针对左手材料磁谐振器设计问题,提出了磁谐振器设计原理,为消除磁谐振器的双各向异性,所设计的结构关于电场方向等效为镜像对称的单回路。根据此原理,设计了耦合增强型"巨"字形磁谐振器结构,并通过实验仿真验证了结构的等效负磁导率。结果表明,所设计的结构在8.9GHz-10GHz之间具有负的等效磁导率,并且结构的双各项异性得到了有效的消除,说明了所提出设计原理的正确性。相对于传统的开口谐振环磁谐振器,"巨"字形磁谐振器结构简单,易于进行加工制作和理论分析。

基于磁谐振器加载的宽频带超材料吸波体的设计

基于加载集总元件的磁谐振器设计了一种宽频带、极化不敏感和宽入射角的超材料吸波体.该吸波体的结构单元由加载集总元件的磁谐振器、介质基板和金属背板组成.仿真得到的加载集总元件和不加载集总元件情况下一维阵列结构吸波体的吸收率表明,相对于不加载集总元件的情况,加载集总元件的一维阵列结构吸波体能够实现宽频带吸波.仿真得到的集总电阻和集总电容取不同值时一维阵列结构吸波体的吸收率表明,集总电阻和集总电容都存在一个最佳值,此时吸波体的吸收率最高、吸收带宽最宽.仿真得到的基板有耗和无耗情况下一维阵列结构吸波体的吸收率表明,吸波体内的能量损耗主要源于磁谐振器中加载的集总电阻,与基板的介质损耗关系不大.仿真得到的二维阵列结构吸波体在不同极化角和不同入射角下的吸收率表明,该吸波体具有极化不敏感和宽入射角特性.

电谐振器和磁谐振器构成的左手材料的实验验证

加工、制作和测试了由电谐振器和磁谐振器构成的左手材料.首先分别测试了电谐振器、磁谐振器各自的传输频谱,得到各自的负参数区域,然后测试了由电谐振器和磁谐振器构成的左手材料的传输频谱,并提取了其等效介电常数和磁导率.实验结果表明,在电谐振器和磁谐振器各自传输禁带的重合区域,出现了一个通带,在该通带内,等效介电常数和磁导率同时为负,验证了材料的左手特性.

有效提高磁耦合无线电能传输距离的仿真实现

基于前期课题组研究的基础上,对四线圈无线电能传输函数和临界耦合系数进行电路理论和物理模型的仿真,提出减小模型中环与线圈的耦合系数(提高环与线圈的耦合距离),能够提高能量稳定高效传输的距离。使用这种方法,系统负载阻抗固定为50Ω,模型中环与线圈距离为22cm,稳定有效传输距离达1.48m,传输距离为0.1~1.8m,输能效率为76.1%~46.8%。

一种基于65nm CMOS工艺的33.5~37.5GHz有源矢量合成型移相器

基于65 nm CMOS工艺设计了一款33.5~37.5 GHz的6 bit有源矢量合成型移相器(VSPS)。该移相器采用Lange类型的90°耦合器作为I/Q信号发生器,其中的电感采用8字形电感实现;此外,矢量合成部分采用电流合成结构,使芯片面积更加紧凑。后仿真结果显示,该移相器覆盖360°移相范围,对于64种移相角度状态,其整个工作频带下的相位均方根(RMS)误差约为0.33°~3.20°,移相附加增益幅度约为-8.38~-4.89 dB,其RMS误差小于0.59 dB,噪声系数约为12.55~15.55 dB,输入反射系数小于-15 dB,输出反射系数小于-7.9 dB,在33.5、35.5和37.5 GHz频率下,其1 dB压缩点输入功率分别为-1.38~0.96、-1.13~0.75和-0.30~1.40 dBm。该移相器核心电路面积仅约为0.11 mm^(2),在1.2 V的电源电压下,消耗14.6 mW的直流功率,具有面积紧凑、功耗较低、插入损耗适中且精度较高的优势,有利于相控阵系统大规模集成和应用。

一种新型X波段宽带左手材料的设计和特性研究

为了更简便的制备宽带内的左手材料,提出一种新型的X波段方形开口磁谐振器(SSRs),通过将该磁谐振器与H型电谐振器的耦合,设计了一种电路板单面印刷的宽带左手材料(Left Hand Materials,LHMs).经过HFSS(High Frequency Structure Simulator)仿真,利用散射参量法计算分析了SSRs、H型谐振器的传输特性和负电磁参数特性、电磁谐振器耦合结构的负介电常数、负磁导率和负折射率.仿真证实:该结构在10.05～11.6GHz频带内具有负折射特性,较同频段其他LHMs带宽更宽.同时耦合结构可以单面印刷,尺寸较大,在一定程度上避免了传统LHMs对印刷电路板刻蚀工艺加工精度的较高要求,便于实际制备.

一种小单元宽频带左手材料的分析与设计

用电谐振器和磁谐振器组合来实现同时具有负磁导率和负介电常数的左手材料是比较普遍的方法,左手材料中磁谐振器的设计最为重要,为抑制磁谐振器中的电响应,提出了单回路镜像对称原理,从而设计了一种小单元宽频带的回型磁谐振结构,再将磁谐振器与电谐振器组合,形成了小单元宽频带左手材料,通过仿真验证了磁谐振结构的等效负磁导率、工型电谐振结构的等效负介电常数和左手材料的左手特性。利用NRW方法提取出该回型结构的有效磁导率和有效介电常数。结果表明:此结构在6.5GHz-11.7GHz间具有左手特性,和传统的史密斯结构相比,本文所设计的左手材料结构简单,易于分析和加工制作,低损耗,低成本。

Variable Frequency Harmonic Oscillator in an Electromagnetic Field

The invariant, propagator, and wavefunction for a variable frequency harmonic oscillator in an electromagnetic field are obtained by making a specific coordinate transformation and by using the method of phase space path integral method. The probability amplitudes for a dissipative harmonic oscillator in the time varying electric field are obtained.

Research on resonance fault caused by dc magnetic biasing in ultra high voltage transformer with parallel static var compensator

For dealing with the resonance fault of ultra-high voltage transformers(UHVTs)with the parallel thyristor controlled reactor(TCR)+the filter compensator(FC)type static var compensator(SVC)caused by dc magnetic biasing,a simulation model of UHVT with parallel SVC for the frequency analysis of the impedance characteristics and a magnetic-field coupling model for UHVT based on classic Jiles-Atherton hysteresis theories are constructed based on the MATLAB/Simulink platform.Both the theoretical and simulation results prove that the resonance fault is caused by the resonance point on the low-voltage side of the transformer,which will approach the 4th harmonic point under magnetic biasing.Based on the fault analysis,a new resonance control method is proposed by adding reactance with by-pass switches in series with FC branches.Under dc magnetic biasing,the cutoff of the by-pass switch will increase the series reactance rate of the FC branches and change the resonance point.In order to avoid the 7th harmonic increasement caused by this method,the firing angle of the TCR branches is locked between 130°and 180°.The effect of the proposed method is validated by the simulation model of a 750 kV UHVT and the results show that the mechanism analysis of the resonance fault is correct and the resonance control method is valid.

Study on Over-Voltage of 220 kV Transformer＇s Neutrals and Protection Strategy

In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula. This article uses the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220 kV power grid. The result shows that the power frequency transient over-voltage on the neutrals may reach 178 kV. If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6 kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7 kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220 kV transformers at the end.

Ferroresonance at Open Phase Operating Conditions of Power Transformers

The reliability of electric supply to consumers is one of the most important factors that determine the requirements imposed on modem utility companies. This paper presents the results of investigation by computer software of the overvoltages resulting from a ferroresonance conditions in MV networks at open phase operating condition with and without connection to earth on source and load sides of distribution transformer. This overvoltage may reach 4.2 pu on one of the HV side of transformer unswitched phases. The results of the study show that ferroresonance overvoltage may be controlled by replacing fuses with circuit breakers on HV side to ensure switching-off all phases. Insertion of resistor or reactor in the neutral of source and loadsides of the transformer with 5% active load will help in suppressing overvoltages.

基于单面金属结构的二维宽带左手材料

利用将磁谐振器与共面短金属导线相结合的思想,设计了一种基于单面金属结构的二维左手材料.理论分析与仿真结果均表明该结构在某一频段同时具有负等效磁导率和负等效介电常数,并且相对左手带宽达到36%.此外,该结构具有良好的容错能力,短金属导线宽度的变化对整体结构的谐振频率及通带宽度影响很小,这不仅有利于实际加工而且对于设计红外及太赫兹频率范围下的左手材料具有参考价值.

Raman lasing and Fano lineshapes in a packaged fiber-coupled whispering-gallery-mode microresonator

We report Raman lasing and the optical analog of electromagnetically-induced-transparency(EIT) in a whispering-gallery-mode(WGM) microtoroid resonator embedded in a low refractive index polymer matrix together with a tapered fiber coupler. The microtoroid resonator supports both single mode and multimode Raman lasing with low power thresholds. Observations of Fano and EIT-like phenomena in a packaged microresonator will enable high resolution sensors and can be used in networks where slow-light effect is needed. These results will open up new possibilities for portable, robust, and stable WGM microlasers and resonator-based sensors for applications in various environments.