COUPLING PROPERTIES OF THE SLOT IN A WAVEGUIDE JUNCTION

The coupling properties of a transverse slot in the common wall between two buttingrectangular waveguides are discussed.By means of Galerkin’s method which takes into accountthe wall thickness,equivalent magnetic currents on the aperture surface of the slot are obtained,and then the general formulae of scattering fields and of equivalent parameters are derived.Thedimensions as well as seats of those two waveguides and the slot,and the thickness of the wall arearbitrary.For example,the transforming coefficients and the VSWRs of numerical calculationand experimental results are given.They are in good agreement.

NUMERICAL ANALYSIS OF CENTERED-INCLINED COUPLING SLOTS IN RECTANGULAR WAVEGUIDES

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides, taking into account the transverse distribution of the electric field across the slot aperture. Integral equations are formulated based on dyadic Green's function theories and solved using the method of moments. Trigonometric basis functions are adopted. It is found that the method will converge with up to ten basis functions. The characteristic parameters can be easily obtained for different slot sizes. Resonant length and resonant resistance of the coupling slots are calculated. It is shown that the calculated results have very high accuracy, compared with simulated results obtained from commercial software. Therefore, it can be effectively applied in the synthesis of antenna arrays. Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed. The results show that if the transverse distribution of the electric field is neglected, the calculated error tends to become larger when the slot gets wider or thinner.

Research on novel multi-layer and multi-polarized slot-coupling planar antenna array

A novel multi-layer planar antenna array to achieve multi-polarized radiation is developed. U-shaped coupling slots are embedded in the ground plane to extend the bandwidth. The phase relation between adjacent elements in the radiation field is analyzed when adjacent elements are fed in opposite phase. Return loss and radiation pattern are measured for a 16-element antenna array at 12.5 GHz. The radiation pattern shows a good agreement with the calculated one in the shape of the main beam. The return-loss of the proposed antenna array is less than -20 dB in the 12.5 GHz frequency band （12.25-12.75 GHz）. Because of two feed ports the antenna can transmit arbitrary elliptic polarized waves if the two feed ports have different amplitude and phase. The main factors such as element spacing, substrate medium and manufacturing imperfection are analyzed and the corresponding conclusions are presented.

Linear theory of beam–wave interaction in double-slot coupled cavity travelling wave tube

A three-dimensional model of the double-slot coupled cavity slow-wave structure （CCSWS） with a solid round elec- tron beam for the beam-wave interaction is presented. Based on the ＂cold＂ dispersion, the ＂hot＂ dispersion equation is derived with the Maxwell equations by using the variable separation method and the field-matching method. Through numerical calculations, the effects of the electron beam parameters and the staggered angle between adjacent walls on the linear gain are analyzed.

Design of a Microwave Filter Based on a Novel Negative Coupling Structure with Conical Through-Hole

This article introduces the design theory of ceramic waveguide filter and proposes a new type of negative coupling structure with a conical throughhole,which has fine-adjustment of negative coupling without significantly increasing the insertion loss of the filter.Based on this,the article proposes an eightcavity ceramic waveguide filter design for 5G base stations.It also presents a detailed discussion on the influence of the cross-coupling slot lengths L2 and L4 on the transmission zeros positions during the filter optimization process and the relevant change rules.For the proposed optimized filter,the observed performance indicators include the center frequency of 3.5 GHz,working bandwidth of 200 MHz,an insertion loss of≤2.0 dB,return loss of≥19 dB,and out-of-band nearend suppression and out-of-band far-end suppression of≥39 dB and≥63 dB,respectively.The test performance results obtained for the sample,with structural parameters as per the simulation model,were in good agreement with the simulation results.

GH4169涡轮盘榫槽电解拉削仿真及其试验研究

榫槽是航空发动机涡轮盘上的重要结构,电解拉削是实现该结构高效、低成本制造的潜在解决方案。为了掌握电解拉削加工参数对轮廓精度和表面质量的影响规律,建立了电解拉削多场耦合模型,阐明了工具阴极长度对加工间隙产物分布的影响规律,获得了优选的工具阴极长度参数。开展了平面电解拉削加工试验,探究了进给速度和加工间隙对工件表面质量和型面进出口去除量差的影响规律,确定了较优的加工参数。试验结果表明,采用优化的加工参数可以获得较好的表面质量并有效控制了型面进出口去除量差。最后,采用优化的参数开展了典型涡轮盘榫槽结构单元件的电解拉削加工试验,试件具有较好的表面质量和轮廓重复精度。

基于4H-SiC的开槽四梁式压阻式加速度计设计及仿真研究

基于4H-SiC设计了一种开槽四梁式的压阻式加速度计,通过分析开槽位置、开槽大小对传感器灵敏度及固有频率的影响确定了开槽的相关参数,并对该结构采用有限元方法进行了热-力耦合仿真,确定了该结构在不同温度场下施加不同载荷时的理论电压输出。研究结果表明:该结构相较于传统双端四梁结构输出灵敏度提升51.4%,固有频率仅下降14.2%,在ANSYS 600℃的稳态温度场环境下,传感器输入载荷与输出电压成线性关系,理论满量程输出为39.71 mV。

卫星导航终端小型化开口缝隙螺旋天线

研究了一种小型化卫星导航终端开口缝隙螺旋天线。天线主体为四条宽度渐变的开口缝隙螺旋臂,蚀刻在外表面覆铜的介质基板围成的方型结构上,由印制于介质基板内表面的微带线结构馈电网络进行耦合馈电;馈电网络由底面回形结构和侧面逐渐向上变宽的折形结构组成,使用同轴线接头在天线底部对其馈电。天线总体尺寸为26 mm×26 mm×29 mm,实测结果表明:|S_(11)|≤-10 dB的阻抗带宽为7.88%(1.523 GHz~1.648 GHz),轴比≤3 dB的圆极化带宽为20.26%(1.490 GHz~1.826 GHz),在北斗B1频段中心频率(1.561 GHz)、GPS L1频段中心频率(1.575 GHz)和GLONASS L1频段中心频率(1.602 GHz)处增益分别达到3.33 dBi、3.18 dBi和2.79 dBi。该天线采用开口缝隙螺旋结构,通过简单的馈电网络串行耦合馈电实现天线的圆极化,在较小尺寸情况下实现了较宽的带宽和较好的增益。

一种紧凑型高效率毫米波整流天线

为了提高毫米波无线输能系统的接收端效率,设计了一款基于缝隙耦合馈电的紧凑型高效率毫米波整流天线,该整流天线通过划分子阵,每个子阵单独进行能量转换,采用直流合成的方式进行整合输出,具有尺寸小、剖面低、易共形等特点。天线采用缝隙耦合馈电,馈线和辐射贴片分别在地板的两侧,有效的减少天线电路之间的影响,同时增大了天线的有效辐射面积。后端整流电路采用单二极管并联整流拓扑,利用扇形枝节作为直通滤波器进行直流滤波。该整流天线工作频率为35GHz,天线阵列增益为23.4dBi,实测在17dBm接收功率下具有最高58.65%的整流效率,可广泛应用于毫米波无线输能系统中。

割缝筛管缝宽优化数值模拟

对于割缝筛管缝宽的选择,大多数是基于经验公式,对防砂效果会产生较大的影响。利用CFD-DEM耦合方法研究不同因素对割缝筛管防砂性能的影响规律,结合正交试验确定各因素影响筛管性能指标的主次顺序,建立筛管防砂性能的回归方程模型,得到割缝筛管缝宽最优选择方式。结果表明:流通性能与挡砂性能最主要的影响因素为缝宽尺寸,抗堵塞性能主要受到流体黏度的影响;使用缝宽优化模型得到的最优解在整体防砂性能上优于经验公式的缝宽尺寸。研究结果可为特定储层条件下油气井防砂性能的预测与防砂介质的精度优化提供参考和借鉴。

Double U-Shaped Slots Loaded Stacked Patch Antenna for Multiband Operation

The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.

Single Layer Slot-Loaded Gap-Goupled Microstrip Array Antenna for Tri-Band Application

A novel method for tri-band microstrip array antenna with improvement in the bandwidth by incorporating wide slots and additional resonators which is gap-coupled to the non-radiating edges of a radiating element is presented. The experimental results show that two element slot-loaded gap-coupled microstrip array antenna gives a ?10 dB return loss band-width for three bands. The design specifications, radiation patterns and gain of the proposed antennas are presented and described.

一种基于曲折枝节去耦的多元滤波天线

针对目前越来越复杂的通信测控要求,提出了一款具有滤波特性的天线单元以及一种有效去除天线单元间耦合的结构。天线单元采用微带天线形式,通过在辐射贴片上开槽的方式实现滤波特性,经测试滤波天线在阻带处增益值下降迅速,滤波频点增益降到-30 dB以下,具备良好的边带滤波特性,反射系数在通带频段内均小于-10 dB,辐射方向图测试结果与仿真结果较为吻合。基于此天线单元,对多元天线的去耦结构进行了研究,经仿真分析并加工实物测试,发现曲折型去耦结构对抑制天线单元间的耦合具有明显作用,在通信频段内隔离度大于20 dB。与现有研究成果相比,该结构具有优势。

带有扼流槽结构的共形波导缝隙阵列天线研究

设计了一款与圆柱面共形的宽边纵缝波导缝隙阵列天线,波导间采用扼流槽结构设计,抑制了表面波的影响、提高了天线增益。仿真结果表明:优化后的扼流槽结构可使共形阵列天线中间波导的互耦系数减小4.4 dB,两侧波导间的互耦系数减小3.6 dB;扼流槽结构参与了阵列天线微波辐射,提高了阵列天线的方向性;阵列天线的增益达23.3 dB,口径辐射效率达67.5%。实验结果表明,共形波导缝隙阵列天线实测增益达22.1 dB(含功分网络损耗1.1 dB),实测天线口径辐射效率达66.0%,功率容量达1.1 GW。实验结果与仿真结果基本吻合。

双分数槽潜油永磁电机磁热耦合分析

针对潜油永磁电机温度过高导致定子绝缘层脱落和转子永磁体受热产生不可逆退磁问题,在定子外径不增大的情况下,提出一种特定空间角度的双分数槽集中绕组结构。首先,根据特殊的绕组结构利用有限元法对该电机模型不同时刻的磁势进行求解分析。其次,在二维瞬态场中分别得到电机空载和额定负载工况下的电磁特性。最后,利用电磁场和温度场结合的多场耦合法求解电机定子、转子、永磁体和线圈的温升。结果表明,在不改变定子外径的情况下双分数槽集中绕组结构能够有效降低电机整体温度,其中永磁体温升下降8.74%,线圈温升下降36.4%,证明了此结构设计的合理性。

用于微波烧结黄土的圆波导缝隙天线设计

在土木建筑领域,湿陷性黄土地基受水浸湿后需进行热加固处理,避免地基承载力下降导致工程安全事故的发生。针对该问题,设计了一种工作在2.45 GHz、结构简单、在黄土中匹配效果良好及加热效果良好的圆波导缝隙天线,用于微波烧结湿陷性黄土,并使用多物理场仿真软件COMSOL Multiphysics对烧结效果进行了仿真与分析。结果表明,使用该天线加热半径为45 cm的黄土40h后,黄土的平均温度可达到使湿陷性黄土水分蒸发的100℃,最高温度出现在缝隙周围,由于黄土对电磁波的衰减,距离天线越远加热效果越不明显。此外,通过对黄土介电常数和尺寸的扫参,发现该天线在土体中的S11参数随黄土介电常数和尺寸的变化不大,因此该天线在不同的土壤环境下都能实现良好的匹配和烧结效果。

中央开槽箱梁颤振非线性特性和振动分叉现象及其机理

为探究超大跨度缆索承重桥梁在大攻角范围内的颤振稳定性,通过节段模型风洞试验对中央开槽箱梁在风攻角±10°范围内的颤振非线性特性和振动分叉现象及其机理进行了研究。结果显示:当风攻角为-2°~10°时,节段模型系统未发生颤振;当风攻角为-3°和-4°时,观察到了含振动分叉的非线性颤振现象,且起振幅值随风速的增加而减小;当风攻角为-5°~-10°时,颤振无需人工激励就会自动发生。两种非线性颤振均为弯扭耦合颤振,并最终做极限环振动。非线性颤振的起振风速随着负攻角的增大而减小,耦合程度随着折减风速的增加而增加。系统等效阻尼比-振幅曲线可以很好地解释非线性颤振机理,曲线的零点为系统平衡点,其中斜率为正的零点为稳定平衡点,对应稳态振幅;斜率为负的零点为不稳定平衡点,对应起振振幅。对于含振动分叉的非线性颤振,系统存在一个稳定平衡点和一个不稳定平衡点;而对于无需人工初始激励的非线性颤振,系统只有一个稳定平衡点。

叶片开缝和边界层抽吸耦合控制压气机失速裕度的数值研究

为了进一步优化压气机的整体性能,提出三种叶片开缝和边界层抽吸的耦合流动控制方案。首先,利用数值模拟的方法,研究叶片开缝或边界层抽吸对跨声速轴流压气机流场结构的影响机理。然后,详细研究了边界层抽吸分别与三种不同叶片开缝的耦合流动控制方案对压气机整体性能的影响。研究结果表明,与叶片开缝或边界层抽吸的单独应用相比,三种耦合流动控制方案都使压气机实现了更宽的稳定裕度。全叶片开缝与边界层抽吸的耦合方案稳定裕度改进量为1.27%,中间叶高开缝的耦合方案和上半叶高开缝的耦合方案稳定裕度改进量分别为1.67%和1.35%;在近失速点处,相比较全叶片开缝与边界层抽吸的耦合方案,局部开缝与边界层抽吸的耦合方案应用后,总压损失和效率降低;上半叶高开缝的耦合方案在三种耦合方案中稳定裕度最高,所以叶片开缝和边界层抽吸的耦合方案是可行的。

开槽对嵌入式水润滑轴承轴瓦变形的影响机理分析

通过在水润滑轴承橡胶轴瓦嵌入微传感器的方法,可实现传感器最大程度接近测点,获得准确的轴承特性数据,对轴承研究具有重要意义。然而,微传感器嵌入要在轴瓦开槽,槽的结构对轴瓦变形会产生影响,其机理需深入研究。根据实际情况,提出了三种开槽结构,分别为长方体结构(结构1)、前槽面弧度面结构(结构2)、前后槽面弧度面结构(结构3)。采用Ansys软件建立热-流-固耦合模型,在不同供水温度、轴转速工况下,分析对比了不同开槽结构对橡胶轴瓦变形的影响机理,结果表明:随着供水温度的升高开槽处最大变形量降低,随着轴转速升高开槽处最大变形量先增大再减小最后趋于稳定,相比之下结构3在开槽表面长度和开槽深度上轴瓦最大变形量最小。

低副瓣微带天线设计

针对传统低副瓣天线工作带宽窄的问题,设计了一种应用于低副瓣天线阵列设计的新型宽带微带天线单元。通过采用H型槽耦合馈电方法,天线单元工作带宽达到11%以上。同时,为实现天线阵列的宽频带工作特性,对宽带馈电网络进行了专门设计。馈电网络采用串、并结合的馈电方式,利用阻抗变换节实现所需要的天线单元馈电幅相分布。基于所设计的天线单元和馈电网络,设计了一种基于道尔夫-切比雪夫电流分布的C波段微带天线阵,并对天线进行了加工、测试。测试结果表明,所设计的天线具有低副瓣、窄波束、高增益的特性,天线的旁瓣电平抑制大于20 dB。