Shielding Effectiveness of Rural Concealed Communication Cable of Asymmetric/Symmetric Slots with Different Shapes

With the rural concealed communication cable as the study object, the shielding effectiveness of different slot shapes was analyzed by using LBEM （linear boundary element method）. The engineering example results showed that for twocore shielded cable, the coupling capacitance of trapezoid slots （asymmetric and symmetric） changed the most, followed by rectangular slots （asymmetric and symmetric）, and the changes of wedge slots were the smallest, but the change tenden- cies were consistent. In addition, with the increase of slot width of different slots, the coupling capacitance of tow-cored shielded cable showed small change.

Theory and Experimental Verification on Cymbal-shaped Slotted Valve Piezoelectric Pump

Valve piezoelectric pumps usually have larger flow rate than that of valveless ones. However, the traditional cantilever valve easily induces stress concentration which impacts the reliability of pumps. Therefore, a cymbal-shaped slotted check valve is proposed to be applied in a piezoelectric pump in order to reduce the stress concentration of the valve and thus improve the reliability of the piezoelectric pump. The structure and working principle of the piezoelectric pump are analyzed; the stress analysis of the cymbal-shaped slotted valve diaphragm is conducted. In addition, finite element software is employed to analyze the difference of the Von-Mises stress between the cymbal-shaped slotted diaphragm and the slotted flat diaphragm. The simulation results show that, the Von-Mises stress of cymbal-shaped slotted diaphragm is smaller than that of the slotted flat one. Furthermore, the cymbal-shaped slotted valve piezoelectric pump is also fabricated, and flow rate experiment is performed. The experimental results indicate that the flow rate of piezoelectric pump working in low frequencies(0 Hz < f< 50 Hz) is larger than that working in high frequencies(200 Hz < f< 2000 Hz). When driven at voltage of 160 V and frequency of 5 Hz, the pump reaches its maximum flow rate of 6.6 g/min. The experimental results validate the feasibility of the cymbal-shaped slotted check valve. This research can effectively solve the problem of stress concentration of valve piezoelectric pumps and is helpful for improving the reliability of them.

Plus Shape Slotted Fractal Antenna for Wireless Applications

Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.

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.

Triple Notched Band Characteristics UWB Antenna Using C-Shaped Slots and Slot-Type Capacitively-Loaded Loop (CLL)

Ultra wide bands antennas with notched bands characteristics have recently been considered for efficient communication between devices. In this paper, a compact ultra-wideband antenna (UWB) for UWB applications with triple bandnotched characteristics is presented. The proposed antenna consists of a square patch with four truncated corners and a partial ground plane with a rectangular slit. The operation bandwidth of the designed antenna is from 2.66 GHz to more than 13.5 GHz. Band-notched characteristics of antenna to reject the frequency band of 3.18 - 3.59 GHz and 4.70 - 5.88 GHz, is realized by inserting two C-shaped slots in the patch, the third band of 9.54 - 12.22 GHz is achieved by slottype capacitively-loaded loop (CLL) inserted in the patch near the feed line. Details of the proposed antenna design and simulated results are presented and discussed.

N Design of an H-shaped Slot Multi-frequency Microstrip Antenna

Conventional slot microstrip antenna is analyzed,an h-shaped multi-frequency and miniaturization slot microstrip antenna is proposed.Numerical simulation is performed for the characteristics of the antenna with the software HFSS11.0,which is a kind of simulation software based on Finite Element Method,the simulation results shown that the antenna operated at 2.26~2.42GHz,2.67~2.82GHz,4.28~4.39GHz and 5.76~5.89GHz when the return loss S11<-10dB,the size reduced compare to general microstrip antenna,demonstrated the effectiveness of the design scheme.The antenna structure is simple and easily to be implemented,met the wireless LAN 802.11a/b/g/n mobile terminal antenna miniaturization and multi-band requirements.

On the Design of Plus Slotted Fractal Antenna Array

A new technique which is a combination of fractal antenna and array antenna is presented to design Plus Slotted Fractal Antenna Array (PSFAA) in this paper. PSFAA with corporate feed operates at 2.5 GHz frequency. PSFAA is designed on FR4 substrate material with permittivity 4.4 and height 1.6 mm. PSFAA is designed up to 2nd iteration. High Frequency Structure Simulator (HFSS) software is used for simulation of PSFAA. The proposed antenna array operates at three bands with five frequencies 2.5 GHz, 4.1 GHz, 6.9 GHz, 7.4 GHz and 8.2 GHz. Simulated Return losses results of proposed PSFAA are -22.15 dB, -19.44 dB, -25.21 dB, -10 dB, -12.45 dB at above frequencies respectively. It has a gain of 9.22 dB at resonant frequency 2.5 GHz whereas conventional antenna array has a gain of 5.15 dB at resonant frequency 2.5 GHz. Return losses and gain of PSFAA also improved from conventional antenna array at various resonant frequencies.

基于齿靴型槽楔不等宽组合的PMSLM齿槽力抑制

针对永磁同步直线电机(PMSLM)初级铁心开槽引起的齿槽力和推力波动大的问题,以两单元电机组合的6槽8极PMSLM为研究对象,提出一种齿靴型槽楔(TBSW)结构。通过TBSW不等宽组合,使得各单元电机齿槽力反相位抵消,达到削弱PMSLM总体齿槽力的目的。利用有限元法,分析不等宽TBSW各结构参数变化对电机齿槽力和推力特性的影响,对不等宽TBSW结构参数进行优化;对比分析原电机、采用等宽TBSW和不等宽TBSW电机的各项电磁特性,结果表明,采用不等宽TBSW后,电机齿槽力降低96.88%,平均推力增加3.83%,推力波动减小83.57%,电机性能得到显著提高。最后根据组合式PMSLM单元电机奇偶数量的不同,提出相应的不等宽TBSW齿槽力抑制方案,并验证了所提方案的有效性。

窄河谷大夹角挑流消能工体型优化研究

针对窄河谷大夹角条件下挑流消能易出现冲击两岸、冲坑过深的问题,采用水工整体模型试验方法对具有代表性的某水利枢纽深孔放水冲沙洞挑流鼻坎体型开展优化研究,并对比分析了水舌形态和下游河道冲刷特性。结果表明,不对称收缩的异型窄缝式消能工可使水流在狭窄河道归槽,水舌纵向拉伸效果较好,大幅减轻了河床冲刷;提出了收缩比、收缩角差、斜切面积比等特征参数适宜的挑流消能工体型,可供窄河谷大夹角条件下挑流消能设计参考。

节流槽形状对液压滑阀卡滞力的影响

液压滑阀是液压系统中的关键控制部件之一,其结构简单可靠,易于实现流量、压力控制。但是运行过程中由于热负荷产生的微小变形会导致阀芯卡滞现象的出现。当阀芯发生卡滞现象时,可能会严重降低液压阀的精度和灵敏度。基于热-流-固耦合模型,分析了节流槽形状对液压滑阀卡滞力的影响。首先建立了阀内固定开度流道模型,计算获得了不同节流槽形状下阀内流动特性;其次,将流体分析得到的温度场信息作为边界条件加载到热分析中,得到阀芯上的温度分布特性;最后研究了不同节流槽形状下阀芯间隙的变形量,分析阀芯卡滞的变化,为减小阀芯卡滞措施的研究提供参考。

偏斜转子槽形感应电机正反转性能差异的研究

转子槽形沿径向偏斜后的电机电磁性能受电机转向影响。为减小偏斜转子槽形电机正反转时的性能差异,提出一种槽身偏斜槽形,保证槽形的槽口区域轴对称。基于转子槽漏磁模型,对比径向偏斜与槽身偏斜槽形,探讨槽形偏斜后的等效磁路变化,以及转子槽漏抗与主电抗参数随偏斜距离的变化规律。利用冻结磁导率法隔断主磁通的气隙路径,假设由槽内导体电流产生的转子漏磁场仅包括槽漏磁场,计算电机正反转下不同槽形偏斜距离时的槽漏抗值,并根据等效电路模型计算相应的主电抗值。最后,仿真计算两类偏斜转子槽电机的输出转矩与功率因数,结果表明转子槽身偏斜电机正反转时的性能接近,而且受槽形偏斜距离的影响较小。偏斜转子槽形的不对称槽口区域是引起电机正反转性能差异的主要原因。

5G毫米波三频单阶ISGW腔体滤波器设计

本文提出了一种紧凑的三频单阶集成基片间隙波导(ISGW)腔体滤波器。为了限定腔内模式数量,通过分析ISGW腔模的谐振频率关系,设计了一个腔内只有三个谐振模式的ISGW腔体。为了改善频段之间的带外抑制同时提高频率选择性,提出了新颖的三频单阶滤波响应耦合拓扑,然后在研究该腔体内的腔模位于四个端口处的耦合关系的基础上,设计了不同于传统输入输出端口的位置关系,其输入输出端口各有一个“U”型槽,呈90°布局作馈电结构。最后得到了三个通带内只有一个谐振模式的三频单阶腔体滤波器。对该滤波器进行了建模、仿真和构造,然后利用网络分析仪测量了其端口反射传输系数。测试结果表明,该滤波器的三个频段的中心频率分别为f_(01)=24.25 GHz、f_(02)=27.57 GHz和f_(03)=31.14 GHz;插入损耗(IL)分别为IL_(1)=1.58 dB、IL_(2)=1.07 dB和IL_(3)=2.51 dB;有限传输零点(FTZ)分别为FTZ_(1)=20.55 GHz、FTZ_(2)=26.20 GHz、FTZ_(3)=29.37 GHz和FTZ_(4)=33.17 GHz;频段之间的带外抑制优于13 dB。测量结果与仿真结果之间存在一定的频移,但相对带宽优于仿真结果。相比较传统滤波器器件,该款滤波器具有设计频段高、在毫米波频段带外抑制水平高、频率选择性强、整体体积小和质量轻等优势。

一种可任意幅相调制的波导缝隙波束赋形天线

为实现搜索雷达余割平方的波束赋形性能,设计了一款“几”字形波导缝隙阵列波束赋形天线。该天线采用“几”字形折叠结构和缝隙偏移以实现相位与幅度调制,实现了阵列的余割平方波束赋形。通过电磁仿真计算,最终确定了天线的最优结构参数,进行了实物加工和测试。实测结果表明,在16.4~16.6 GHz的频率范围内,该阵列天线的电压驻波比小于1.25,增益高于15.4 dBi,实测结果与仿真结果具有较好的一致性。该天线具有大功率、高增益、剖面低等特点,可作为波束赋形相控阵天线的组阵单元。提出的波导缝隙阵列赋形天线实现方式可有效减小赋形波束范围内理论值和设计值之间的差异,使波导缝隙天线波束赋形的设计不再受限于缝隙的幅度和相位控制,可适用于多种波束赋形场合的应用。

基于DGS的紧凑型低通滤波器

文中提出一种基于缺陷地结构的新型低通滤波器。其由位于微带结构顶部的加宽微带线、位于接地层中的经典哑铃型缺陷地结构(DGS)和蛇形缝隙缺陷地结构(DGS)组成,结构设计紧凑,容易调整。文中选用0.01 dB等波纹的切比雪夫型低通滤波器,分别采用哑铃型DGS、蛇形缝隙DGS替换LPF原型电路中的电感,加宽微带线替换并联电容,同时将加宽微带线产生的寄生电感考虑进去。哑铃型DGS产生的高频衰减点加宽阻带,蛇形缝隙DGS提供的低频衰减点使得通带到阻带陡峭过渡。实验结果表明,所设计的截止频率为2.54 GHz的低通滤波器具有明显的截止频率响应,通带内插损均在0.9dB以下,阻带抑制均在21dB以下。经实物加工测试验证,所设计的低通滤波器实际结果与仿真结果基本一致,具有可行性。

具有解耦结构的宽带定向双圆极化天线设计

本文设计了一种具有宽带特性的定向双圆极化天线。该天线具有三层结构:辐射层、反射层和解耦层。辐射层为矩形驱动贴片以激励U型缝隙产生圆极化辐射,天线通过两个对称的微带馈电端口可分别实现左旋圆极化和右旋圆极化。反射层为放置于天线正下方的金属板以实现定向辐射,但是这导致了天线轴比和端口隔离度性能下降。针对这一问题,在辐射层U型缝隙处倒角和开缝以改善轴比带宽,并在辐射层上方加载了刻蚀周期分布的寄生贴片解耦层以改善端口隔离度。仿真和测试结果表明,天线的阻抗带宽和3 dB轴比带宽分别为1.59 GHz~7.79 GHz(132.1%)和2.75 GHz~5.78 GHz(71%),天线的端口隔离度在工作频带内均小于-10 dB,峰值增益达到8.1 dBi。

小型化双向波束矿用定位终端天线设计

双向天线可有效提高信号覆盖范围和天线耦合效率,削弱由巷道侧壁反射所带来的多径效应,适用于结构狭长、断面较小的煤矿井下巷道。针对现有双向天线尺寸大、增益低、带宽不满足井下UWB精确定位系统要求等问题,设计了一种小型化双向波束矿用定位终端天线。通过布置2个等幅同相U形单极子天线并在金属地板上引入U形槽结构,在保证天线整体结构紧凑的同时,实现了双向边射波束辐射特性。仿真和实测结果表明:天线的-10 dB带宽为1GHz(3.6~4.6 GHz),可有效覆盖煤矿井下UWB人员精确定位系统的工作频段(3.7~4.2 GHz);在3.6~4.6 GHz频段内,天线峰值增益为2.2~2.5 dBi,具有良好的幅频响应。

L形肋桥面板单元-上隔板组装制造工艺研究

张靖皋长江大桥南航道桥采用桥跨为2300m+717m的双塔双跨钢箱梁悬索桥,北航道桥采用主跨1208m双塔单跨钢箱梁悬索桥;钢箱梁桥面板单元预采用纵向L形肋-苹果形孔槽口的正交异性钢桥面板构造。为了满足上隔板槽口与L形加劲肋间的组装间隙要求,提出了钢箱梁桥面纵向L形肋板单元与苹果形孔槽口上隔板组装制造工艺,以期为类似板单元与隔板组装提供参考。

通过优化泄荷槽降低楔形封闭容积对压缩机的影响的分析和实验

大多数基于不对称型线的双螺杆压缩机,壳体排气端面与转子排气端的接触线之间会形成一个楔形封闭容积,楔形封闭容积对压缩机的比功率、噪声、振动烈度等都有着不小的影响。在设计压缩机轴向排气口时增加泄荷槽,可以降低楔形封闭容积带来的不利因素。为了进一步降低这种不利因素,可以优化原有泄荷槽的形状、位置等,并通过实验作对比,验证方案的可行性。

缝隙加载H形双频天线

为了适应现代双频通信系统的要求 ,双频天线必须具有小尺寸和频率易调节的特点。通过在H形微带天线的辐射边附近采用U形缝隙加载 ,在单层微带天线上实现了双频效果。和常规的双频微带贴片天线相比 ,该天线的尺寸可以大大减小。通过改变天线的尺寸参数 ,高频段和低频段可以很容易地调节 ,本设计中得到频率比范围是1.716～ 2 .36 3。该天线在两个频段有相同的极化平面和较宽的辐射波束。