大型天线罩小损耗测量的一种新方法

本文提出了大型整体天线罩小损耗测量的一种新方法,详细讨论了其测量原理和方法程序.给出了某天气雷达工程S波段8.54米天线12米罩子的传输损耗测量结果,测试结果良好.     

两电平和三电平VSC-HVDC系统在输电环节效率的分析与比较

为了计算基于两电平和三电平的电压源换流器在VSC-HVDC系统里呈现的链路效率,我们使用平均根和均方根的方法来计算电压源换流器的转换电流的平方来测量换流器(传导和开关损耗)的转换损耗。剩余的功率损失(直流电缆侧由于I2R产生的传输损耗,耦合变压器的损耗和交流侧谐波滤波器的损耗)用常规熟知的方法进行评价。得到的结果我们通过数字仿真进行分析和验证。     

屏蔽电机推力轴承搅拌损耗研究

介绍了屏蔽电机推力轴承搅拌损耗(旋转损耗)计算的方法。搅拌损耗与速度的3次方成正比,速度越高,搅拌损耗越大。高速推力轴承,搅拌损耗远大于轴承的摩擦损耗。对搅拌损耗的计算结果和测量结果进行了对比分析。结果表明,计算结果和实测的结果吻合。     

有耗宽带匹配网络的实频直接优化方法

提高微波集成电路的设计精度是一重要课题.本文基于以散射参数表示的多级级联网络传输增益表达式,提出微波多级 FET 宽带放大器的实频直接优化方法.其匹配网络可以计及元件的损耗,且元件的损耗可以是任意非均匀的和频率依变的.设计结果能够更加接近于实际性能,有利于微波集成电路投片合格率的提高.     

管内电缆导体传输交流损耗的理论计算和实验

交流损耗是大型超导核聚变实验装置如国际热核聚变实验堆和中国聚变工程实验堆稳定性的重要指标。然而应用于核聚变装置的管内电缆导体(CICC)在无外场下传输损耗数值计算很少。首先分析基于分布参数等效电路方法对CICC的N根股线的电流进行描述和分析;之后算出整个导体的电流分布,从而求出导体的传输电流损耗;同时,将数值计算结果与临界态模型结果作对比,以验证该计算模型的可行性;提出改进的CICC交流损耗测量方法,为国内下一步测试CICC及其线圈奠定了实验基础;最后,提出适用于单根圆股线的定标法则,为计算CICC的传输电流损耗奠定理论基础。     

Ka波段平板光子晶体波导传输特性测量

为了测量在Ka波段下空气孔型平板光子晶体波导的传输特性,提出采用从金属矩形波导将电磁波耦合进光子晶体波导并测量其传输特性的测试方案。根据两种波导传输模式的场分布,用两段介质尖劈作为电磁波从矩形波导到三角形晶格平板光子晶体波导的模式转换结构,该结构使用电磁场仿真软件找出最优结构尺寸。实验使用聚合物聚醚酰亚胺（PEI）作为介质材料,加工出实际结构,采用AV3629网络适量分析仪测试整个系统的S参数;结果在27~40 GHz之间的传输系数为？7 dB左右,将测试数据与数值结果相比较,并重新设置PEI材料的损耗参数进行仿真,最终,测试结果在损耗角正切为5×10？4的情况下与仿真数据相一致,表明本文提出的模式转换结构有效,平板型光子晶体结构在微波波段的应用打下基础。     

一种宽频带微带线垂直过渡结构设计

针对微波多层电路的微带线垂直过渡问题,提出了一种新型的、适用于毫米波频段的微带线垂直过渡结构,通过微带线上的补偿结构实现了匹配设计,使得微波信号在微波多层结构中跨层传输.该过渡电路结构具有信号传输损耗小、频带宽,易于加工的特性,在微波电路设计方面具有较高的实用价值.将该微带线垂直过渡结构在三维电磁场仿真软件中进行了建模,并进行了实物加工和测试.实物测试结果表明,在0.5～38 GHz的频带范围内插入损耗小于2.7 dB(含两个K-2.92 mm接头及微带传输线损耗),回波损耗大于9 dB.     

开关磁阻电动机的机械损耗测量

计算和测量机械损耗是研究开关磁阻电动机的效率和铁耗的重要手段。本文讨论了两种机械损耗的测量方法,给出了两种方法对一台开关磁阻电动机的测量结果以及根据测量数据拟合的机械损耗经验计算公式。     

基于风资源和风机参数的风电场变压器电能损耗计算研究

风机输出功率受风速影响的不确定性,造成了风电场变压器传输功率变化频繁。在风电场节能评估中通常采用《电力系统设计手册》中电能损耗的计算方法,但计算结果与风电场变压器实际电能损耗存在偏差。文中从变压器电能损耗计算的基本原理出发,依据风电场风资源和风机参数,提出了一种新的风电场变压器电能损耗计算方法,通过多个风电场实际计算结果的分析比较,表明了该方法更符合实际,具有较高的精度和实用性。     

不同合金基体Bi2223带材传输损耗的测量和分析

减少交流损耗可以通过带材的扭绞、铠装层采用合金材料或在芯线之间引进一个电阻层来实现。为了研究高阻值基体材料对交流传输损耗的影响,准备了6个具有不同合金基体的Bi2223带材。在77 K下,测量了6个样品基体的电阻率,研究了Ag合金基体对Bi-2223带材交流传输损耗的影响。研究发现,在I0相似文献   

Electrical and optical properties of microwave dielectric thin films prepared by pulsed laser deposition

Abstract

Bi₂(Zn_1/3Nb_2/3)₂O₇, BiZN, materials possess high dielectric constant and low loss factor in microwave frequency region. They have good potential for device application, especially in the form of thin films. However, the microwave dielectric properties of a thin film are very difficult to be accurately measured. Evaluation on the dielectric behavior of the films through the performance of the microstrip line devices made of these films involves metallic conduction and stray field losses. A novel measuring technique, which can directly evaluate the microwave dielectric properties of a thin film is thus urgently needed.

In this paper, BiZN thin films were grown on [100] MgO single crystal substrates using pulsed laser deposition process. The high-frequency dielectric properties of thus obtained thin films were determined using optical transmission spectroscopy (OTS). The [100] preferentially oriented films with pyrochlore structure can be obtained for the thin films deposited at 400–600°C substrate temperature under 0.1 mbar oxygen pressure. OTS measurements reveal that the index of refraction (n=1.95–2.35) and absorption coefficient (k=0.28x10^?4-2.25 × 10^?4 nm^?1) of the films vary insignificantly with the crystallinity of the BiZN films.     

Dielectric resonators raise your high-Q

High-quality resonating elements are the key to the function of most microwave circuits and systems. They are fundamental to the operation of filters and oscillators, and the performance of these circuits is primarily limited by the resonator quality factor. At microwave frequencies, the quality factor (Q) of metal transmission line resonant circuits is proportional to volume. As a result, waveguide structures are often employed to increase Q at the expense of size, weight, and cost. Dielectric resonators overcome these limitations due to the fact that their losses are dominated by dielectric loss (loss tangent), and only in small part to metallic losses (housing). Dielectric losses are improving constantly, whereas metal losses, with the exception of superconductors, have remained substantially the same. These resonators can be made to perform the same functions as waveguide filters, but are, in contrast, very small, stable and lightweight. The popularization of low-loss dielectric resonators roughly coincides with the miniaturization of many of the other associated elements of most microwave circuits. When taken together, these technologies permit the realization of small, reliable, lightweight and stable microwave systems     

小功率无线电能传输系统谐振线圈设计优化

针对胶囊内镜微型化的发展趋势,采用MATLAB详细分析了PCB板平面螺旋线圈构成的无线电能传输系统中接收线圈的线间距、线宽、铜厚、线圈匝数等参数对于品质因数和传输效率的影响.在电源频率为13.56 MHz下,综合考虑各个方面对线圈的影响,得出优化参数如下:线间距为0.254 mm、线宽为2.54 mm、铜厚为35 μm、线圈匝数为6匝.在优化线圈参数的基础上,详细分析了线圈距离对系统传输效率的影响,验证了PCB螺旋线圈应用于胶囊内镜无线供电的可行性.该优化结果对于研究小功率谐振式无线电能传输系统有一定的参考意义.     

试验线段电晕测量技术及结果

为了配合对特高压试验线段电晕测量的研究,介绍了500kV试验线段电晕测量方法(包括测试仪器、信号取样方式、试验方法等问题)及结果并探讨了特高压试验线段电晕损失测试的几个关键问题。在国内有关输电线路电晕损失的各种论述中,基本上是引用国外的实测结果,一般认为国内从未对电晕进行过实测。早在80年代,作为武汉高压研究所承担的国家“六五”攻关项目的重要部分,即在500kV试验线段上对各种气象条件下,3种分裂方式导线的电晕损失和无线电干扰水平进行了测试。试验的目的是为了论证3×400分裂导线在技术、经济上的可行性,探索采用3×300分裂导线的可能性及技术条件,但这些结果从未公开发表;附录中给出了全部的电晕损失测量结果,其测试方法、结果等对特高压试验线段电晕损失的计算和实测亦有借鉴作用。     

Low loss flexible SrTiO<Subscript>3</Subscript>/POE dielectric composites for microwave application

Flexible, high dielectric constant and low dielectric loss composites for microwave application fabricated with SrTiO₃ (STO) ceramic filler dispersed inside a thermoplastic polyolefin elastomer (POE) polymer matrix have been studied in this paper. The dielectric property and the mechanical property of STO/POE composites filled with different volume fraction of ceramic filler were investigated. The results indicated that with the increase volume fraction of ceramic filler, both the permittivity and the dielectric loss of composites increased. Good frequency stability within a wide range was observed in all the samples. For the composites containing 40 vol% STO, the composites has a tensile strength of 2.75 MPa with an elongation of about 90% at break value. The permittivity and the dielectric loss of the composites were 11.0 and 0.01 in microwave frequency, respectively. A microstrip transmission line on the composites containing 40 vol% STO as a microwave substrate is designed and measured after bending at different angles, meanwhile the transmission coefficients of the microstrip transmission line were unchanged when bending angle is less than 60°. This indicates that the STO/POE composites have the promising characteristics for potential applications in microwave substrate, flexible dielectric waveguide and related flexible microwave devices.     

磁性薄膜高频磁导率测量方法及其研究进展

磁性薄膜广泛应用于信息存储、电磁兼容、磁传感器和微波通讯设备等众多领域,其高频复磁导率谱的准确测量是磁性薄膜研究中的一个重要课题。目前薄膜材料复磁导率的常用测量方法包括微波谐振腔法、检测线圈法和传输/反射法等。首先简要介绍了谐振腔法和检测线圈法,然后重点介绍了微波频率(GHz)下磁性薄膜传输/反射法磁导率测量近年来最新研究进展。     

Experimental study of the possibility of reducing the resistance and unevenness of output field of velocities in flat diffuser channels with large opening angles

In modern combined cycle gas turbines (CCGT), when designing the reducers from the output diffuser of a gas turbine to a boiler-utilizer, wide-angle diffusers are used, in which practically from the input a flow separation and transition to jet stream regime occurs. In such channels, the energy loss in the field of velocities sharply rise and the field of velocities in the output from them is characterized by considerable unevenness that worsens the heat transfer process in the first by motion tube bundles of the boiler-utilizer. The results of experimental research of the method for reducing the energy loss and alignment of the field of velocities at the output from a flat asymmetrical diffuser channel with one deflecting wall with the opening angle of 40° by means of placing inside the channel the flat plate parallel to the deflecting wall are presented in the paper. It is revealed that, at this placement of the plate in the channel, it has a chance to reduce the energy loss by 20%, considerably align the output field of velocities, and decrease the dynamic loads on the walls in the output cross-section. The studied method of resistance reduction and alignment of the fields of velocities in the flat diffuser channels was used for optimization of the reducer from the output diffuser of the gas turbine to the boiler-utilizer of CCGT of PGU-450T type of Kaliningrad Thermal Power Plant-2. The obtained results are evidence that the configuration of the reducer installed in the PGU-450T of Kaliningrad Thermal Power Plant-2 is not optimal. It follows also from the obtained data that working-off the reducer should be necessarily conducted by the test results of the channel consisting of the model of reducer with the model of boiler-utilizer installed behind it. Application of the method of alignment of output field of velocities and reducing the resistance in the wide-angle diffusers investigated in the work made it possible—when using the known model of diffusion reducer for PGU-450T, which is bad from the standpoint of aerodynamics— to reduce the value of the coefficient of the total loss by almost 20% as compared with the model of real reducer of PGU-450T.     

电力变压器系统损耗与散热特性研究

油浸式变压器损耗和散热是影响变压器正常运行的关键因素。为获得变压器系统准确发热量,采用传热学外掠平板对流换热、大空间自然对流换热以及漫灰体表面辐射模型对典型变压器系统进行散热量计算,获得典型变压器系统散热特性。结果表明:变压器系统散热主要通过散热器实现,占变压器系统总散热量的77.66%~85.31%;辐射散热是变压器本体的主要散热方式,占散热总量的55.15%~70.25%;在散热过程中,热量主要通过对流散失,辐射散热量仅占2.18%~11.34%。与变压器系统损耗相比,偏差在10%以下,表明损耗经验公式适用于变压器系统发热量计算。变压器损耗与型号和负载系数密切相关,不同型号的变压器损耗不同,同一负载下变压器容量越大,其损耗也越大,同一型号变压器损耗随负载系数增大而增大。     

TLM simulation of microwave hybrid sintering of multiple samples in a multimode cavity

Microwave heating technology is a powerful mean to ensure successful sintering of ceramic materials. In sintering experiments, low loss insulators, conductors and high‐loss ceramics are microwaved so as to get optimal mechanical and structural properties. It is known that low‐loss ceramic materials such alumina and zirconia exhibit long waiting time before reaching a critical coupling temperature at which microwaves can be readily absorbed. On the other hand, some ceramics such as silicon carbid have a high loss factor and therefore can be used as a process stimulus for microwave sintering of microwave transparent ceramics. Furthermore, successful sintering experiments often require the use of carefully designed insulating structure in order to minimize thermal gradients caused by heat loss from surfaces. All these problems have led to the introduction of microwave hybrid heating (MHH) schemes using higher dielectric loss susceptors, insulation or coating. Since MHH depend mainly on human expertise, the optimization of sintering experiments will certainly benefit from numerical simulations. The transmission line matrix (TLM) is used to study two MHH schemes where both a susceptor and an insulating matrix were, respectively, used as process stimulus for microwave heating of multiple alumina samples within a three‐dimensional multimode cavity. The effects of such MHH schemes and target settings on electric field distribution and power absorption rates are reported in this paper. Copyright © 2003 John Wiley & Sons, Ltd.     

测量船卫星通信环境下BBR-TCP协议传输特性分析

依据测量船卫星通信链路的特点,基于CentOS7和Linux-4.18.9内核,使用Netem和tc搭建了一个测量船卫星通信链路模拟仿真环境。研究了BBR-TCP拥塞控制算法的数据传输特性,分析了在特定的链路带宽和时延下,不同的丢包率对BBR-TCP拥塞控制算法数据传输特性的影响,最后分析了BBR-TCP拥塞控制算法与其它拥塞控制之间的公平性。结果表明:在模拟环境中与CUBIC-TCP算法相比,BBR-TCP拥塞控制算法具有较高的数据传输速率,受丢包率影响较小,且具有较好的公平性。对于测量船与地面之间通信环境中,优化信息传输、部署新设备和提高带宽利用率具有一定的参考价值。