Calculation and Analysis of Near Field of Airborne Short Wave Antenna

Aim To calculate and analyze the near field distribution of ariborne short wave antenna. Methods B-spline method was used to get the mathermatital model of a Boeing 707320Baircraft and simulate its short wave antenna . FDTD (finite-difference time-domain) method are ed tO complete the calculation and analysis. Results The near field distributions on aircraft's surface were obtained, the curve and gray figures of the normalized near field value were shown. Conclusion These modeling and calculating methods can provide data foraircraft's EMC analysis and design.

Microstrip Antennas Loaded with Shorting Post

In this paper, a technical review with recent advances of the microstrip antennas loaded with shorting posts is presented. The overall size of the antenna is significantly reduced by a single shorting posts and the effect of the various parameters of shorting posts on short-circuit microstrip antenna is also discussed.

Numerical Computation of Resonant Frequency of Shorting Post Loaded Gap-Coupled Circular Microstrip Patch Antennas

In this paper, the numerical computation of resonant frequency of the two gap-coupled circular microstrip patch antenna loaded with shorting post by using cavity model is presented. The numerically computed results are compared with simulated results. The two gap-coupled circular microstrip patch antenna loaded with shorting post miniaturize the cross-sectional dimension of the radiating patch at the microwave frequency, which is useful for short range communications or contactless identification systems. The simulation has been performed using method-of-moments based commercially available simulator IE3D.

Design and Development of a 2 ×1 Array of Slotted Microstrip Line Fed Shorted Patch Antenna for DCS Mobile Communication System

Compact microstrip antennas have recently received much attention due to the increasing demand of small antennas for personal communication equipment. The problem of achieving a wide impedance bandwidth for compact microstrip antennas is becoming an important topic in microstrip antenna design. In this paper the design and development of a 2 × 1 array of a low cost slotted microstrip line fed shorted patch antenna (MFSPA) has been presented. Both the shorted patch and microstrip line feed network have air substrate. The material cost is thus reduced to a minimum. The array consists of two adjacent patches fed, using a simple microstrip T network. The impedance bandwidth of nearly 40%, covering the bandwidth requirement of 1750 MHz band is obtained. Also the antenna exhibits dual band operation. The cross polarization radiation in H-Plane observed with a single element antenna has been reduced considerably with 2 × 1 array. A peak antenna gain of 9.2 dBi is obtained with a small variation of 0.8 dBi. From the results obtained it is clear that the antenna array studied has a low cost fabrication and is suitable for applications in DCS mobile communication base station.

A Linear Array Antenna of Microstrip Patch Antennas Fed by the Open-End of Coplanar Waveguides

In this study, we constructed a 4-element linear array antenna using four 20 GHz band microstrip patch antennas with a structure such that the signal is fed to the patch antennas from open-end coplanar waveguides without contact. We investigated factors related to the design of linear array patch antennas. To adjust the maximum radiation direction and reduce return loss, we optimized the spacing between the elements and their shape. With an element spacing of 11.50 mm, patch width of 3.90 mm, and patch length of 4.15 mm, we obtained a resonance frequency of 20.05 GHz and a return loss of -29.59 dB at the resonance frequency. However, in the case of a 4-element linear array antenna structure, undesired resonances occurred in frequency bands other than the design resonance frequency band of 20 GHz. To suppress these undesired resonances and obtaining stable operation at the design frequency, we propose a new structure in which the feed line is loaded with a short stub, and show through computer simulations that the occurrence of undesired resonances can be sufficiently suppressed. Furthermore, we demonstrate the problem of radiation gain reduction caused by introducing a short stub, propose a design method for a new structure in which the feed line has slits between the stubs, and show improvement of the antenna gain by 0.5 dBi.

Numerical Analysis of a Tunable Rectangular Patch Antenna with One Tuning Post

The finite element method(FEM) is applied to a thin substrate rectangular antenna with a shorting post. The results of the resonant frequencies are in good agreement with the experimental data. The input impedances are calculated and the results are presented. In principle, this method is applicable to a microstrip antenna with shorting posts in arbitrary locations.

近钻头随钻测量系统天线参数试验优化研究

近钻头随钻测量系统能够有效避免传统随钻测量系统所面临的数据滞后问题,而天线的参数设计及优化是提高信号传输距离及稳定性的重要因素。本文对某近钻头随钻测量系统的天线参数展开优化研究,通过试验探讨了天线线圈直径、线圈匝数、负载及磁芯等参数与信号传输距离之间的规律。试验结果表明发射线圈匝数为100匝及线径为0.8 mm,接收线圈为180匝及线径为1 mm,且需引入二级功率放大电路并采用铁氧体磁芯或磁片时,信号传输距离及稳定性最优。相关研究成果可为近钻头随钻测量系统天线的优化设计提供理论依据和实践指导。

基于ikPCA-FABAS-KELM的短期风电功率预测

为了增强在短期风电功率预测领域中传统数据驱动机器学习模型的精度,提出基于ikPCA-FABAS-KELM的短期风电功率预测模型.首先,对主成分分析进行改进,提出可逆核主成分分析(ikPCA),在保证数据特征的同时,降低输入数据的复杂度,以提升模型运行速度;其次,引入萤火虫个体吸引策略对天牛须算法(BAS)进行改进,提出FABAS算法;最后,利用FABAS算法对核极限学习机(KELM)的正则化参数C和核参数γ进行寻优,降低人为因素对模型盲目训练的影响,提高模型预测精度.仿真结果显示,提出的预测模型有效提高了传统模型的预测精度.

超宽带低剖面天线设计

介绍了一种超宽带低剖面天线设计,该天线由弯折偶极子、短路寄生结构、接地短路柱、同轴电缆和金属地板构成。给出了天线的设计过程,说明了各部分结构对天线性能的影响。该天线通过加载短路寄生结构,减小了偶极子臂上电流分布,减小了地板对天线的影响,实现了低剖面特性。此外,该天线通过将偶极子中间部分弯折,改善了高频段的辐射方向图。最终,该天线尺寸为750 mm×450 mm×295 mm,剖面高度仅为0.09个低频波长。为了验证天线设计思路的正确性,加工了天线实物。文中给出了天线仿真与测试的电压驻波比以及增益的结果,其测试结果与仿真结果相吻合。该天线在96 MHz~500 MHz(135.57%)频段内电压驻波比小于2.2,并且在该频段内具有定向辐射的方向图,增益大于3.38 dBi。

用于宽角波束覆盖的短路贴片天线设计

针对宽角波束覆盖需求,本文利用辐射模式调制方法,提出了一组短路贴片天线的设计方法,分别对应相控阵天线扫描、单天线宽波束覆盖以及多波束切换三种波束覆盖理论。首先,通过利用谐振模式重分配,设计了单侧宽带短路贴片天线,可以作为具有低互耦特性的相控阵天线单元使用;在此基础上,通过对称单元设计并引入差分馈电,实现了E面宽波束天线设计;此外,利用天线相位中心偏移的特性,结合去耦措施构建了具有双波束特性的宽带短路贴片天线。通过仿真测试,本文提出的三种短路贴片天线相对工作带宽分别为11%、13%和17%,中频E面波束覆盖范围分别为111°、120°和124°,实现了宽带宽波束覆盖性能。

基于时序序列分解和IBAS LSTM的滑坡数据预测模型

针对传统静态机器学习模型在周期项位移预测中的缺陷和动态神经网络超参数人工选择困难的问题,在时序序列分解的基础上,提出一种新的滑坡预测耦合模型。首先,用最大相关最小冗余算法对周期项位移筛选合适的环境特征,作为长短期记忆人工神经网络的输入。然后,在天牛须搜索算法搜索过程中引入反馈机制,以避免原算法中出现远离最优解的问题;在算法迭代过程中将固定的递减因子改为动态递减因子,以提升前期全局和后期局部的寻优能力;利用改进的天牛须搜索算法对长短期记忆人工神经网络超参数进行寻优,以获得最佳的网络参数组合。最后,重构趋势项和周期项预测结果,得到最终预测位移。以发耳滑坡为例进行分析,结果表明:相较于其他方法,所提模型在平均绝对误差、均方根误差以及拟合度等方面更具优势。

短接贴片加载的双频圆极化卫星导航天线

为了降低双频圆极化天线设计的复杂性和成本,文中介绍了一种用于双频全球定位系统(GPS)的紧凑型双耦合短接贴片加载的贴片天线。该天线采用短接贴片加载技术,使得其整体尺寸仅为42 mm×42 mm×9 mm,同时利用超低成本的PPO塑料替代高介电常数的基板,从而实现了成本的降低。提出的紧凑型双耦合短接贴片加载技术使得该天线能够在L1/L2 GPS频段共振。在L1/L2 GPS频段上,该天线在具有大地平面的情况下表现出良好的性能。圆极化辐射增益在L2频段达到3.12 dBic,在L1频段达到4.08 dBic,显示出较高的增益性能。同时,在这两个频段上,该天线的3 dB增益带宽分别为31 MHz和43 MHz。因此,所提出的天线不仅具有低成本、双频、紧凑的特点,而且在L1/L2 GPS频段具有良好的性能表现,是一种理想的贴片天线选择。这种天线的设计和制造对于GPS定位系统的应用具有重要意义,可以满足对于低成本、高性能的天线需求。

BH-VDT垂直钻井工具无线电磁短传模块影响因素分析

垂直钻井工具组合大扭矩螺杆一体化提速技术,是山前高陡构造防斜打快的主要手段。BH-VDT垂直钻井工具采用随钻测量、控制和实时上传一体化设计,如何绕过螺杆将近钻头采集信息高效传输至地面,成为了当下面临的主要技术难题。为此,将脉冲发生器从工具中分离出来,加入无线电磁短传模块,在螺杆的两端接入无线发射模块与无线接收模块,并采用有限元分析软件,建立钻井试验模型来分析影响无线电磁短传模块的因素。仿真结果与现场试验数据符合较好,无线电磁短传模块中的接收天线正极距离套管底部的距离大于20 m时,套管对接收信号强度的屏蔽影响趋于平缓,钻井液电阻率和地层电阻率对该模块的无线传输效果影响较大,接收天线两级的绝缘距离越长对传输效果越有利;而发射端和接收端的距离在8~15 m范围内,对接收信号强度的影响较小。研究结果表明:采用无线电磁短传模块是解决BH-VDT垂直钻井工具绕过螺杆实现井下信息实时高效传输的有效手段,对其他工具为解决此类问题的设计、现象解释有指导意义。

基于深度学习的载体滚转角估计方法研究

姿态测量技术是载体运动状态和安全监测的基础.载体自旋运动使得飞行器各姿态角之间互相耦合,对载体的飞行控制带来严重影响.针对载体滚转下GNSS信号入射方向周期性变化特征,本文提出一种长短期记忆(long short term memory,LSTM)神经网络的深度学习方法,以确定载体的实时滚转角.通过对载体滚转状态下单天线接收卫星信号能量特征的分析,得到载体实时滚转角与接收信号能量幅值关联变化模型,并分析了卫星在轨运行时其空间位置改变对该模型的影响;然后采用LSTM神经网络方法对实测信号中的周期性变化特征进行训练,得到网络各项参数;最后将训练参数用于对实时接收的信号能量进行预测及降噪,并将预测结果通过模型匹配进行载体实时滚转角测算.为验证文中所提出方法的性能,开展了对天滚转实验.实验结果表明:LSTM深度学习方法可还原复杂的信号能量特征,并实现实时载体滚转角测算.

新型集成超宽带开槽天线的研制及其应用

研制出一种用于超宽带短脉宽辐射和接收的新型集成超宽带（ＵＷＢ）槽天线，该天线采用共面波导到槽线的宽带过渡方式馈电，实验结果显示了其高保真的宽带特性及高增益高效率特性．利用所研制的ＵＷＢ天线建立起超宽超带雷达（ＵＷＢＲ）实验系统，测量几种简单目标特性及涂层目标特性，证明了该种天线可用作实际的ＵＷＢＲ天线．

一种新式背射天线

本文提出一种新式背射天线,它把单线背射螺旋作为短背射天线的馈源。这种天线具有结构简单、馈电方便、频带宽、增益中等、易于产生圆极化波等特点,较相同直径接地板的螺旋天线有更优的性能。

一种新型复合结构笼型中馈天线

提出一种新型复合结构的笼型中馈天线．将笼型与不对称双锥结构相结合，展宽了天线的阻抗和方向图带宽，抑制了天线辐射方向图在宽频带内上翘或裂瓣．在馈电位置引入螺旋短截线，有效降低了天线的高度．采用矩量法对天线进行仿真和优化，设计并制作了一副超短波（VHF／UHF）宽频带天线．实测结果表明在100-750MHz频带内无须匹配或加载网络即可满足电压驻波比小于3．0：1，在整个工作频带（100-400MHz）内增益平坦且大于1．5dBi．此外，天线高度和常规偶极子天线相比减小了约50％．

无源毫米波末敏弹

论述了八毫米辐射计的末敏弹的工作原理和设计原则．在搜索过程中末敏弹吊在降落伞下，一面旋转一面以某个适当的速度下降，使辐射计的天线以螺旋线形扫描目标区域。在此有效面积内探测目标，并以很高的命中概率摧毁目标。在天线温度对比度理论计算的基础上研制出探测和定位算法，给出了计算机仿真打靶试验的结果。

机载短波天线间隔离度的全波分析

对飞机等复杂形体及机载短波天线进行全波 FDTD数值模拟所需的数学建模方法的介绍 ,研究了机载短波天线间隔离度的分析计算方法 ,并以波音 70 7- 32 0 B飞机为例计算了机上 4付短波天线间隔离度。所用方法及所得结果可作为飞机电磁兼容分析与设计的手段和依据。

大功率中短波广播天线电磁辐射的预测与防护

随着城镇密集度越来越高,大功率电磁辐射设备如大功率中短波天线不可避免的与建筑越来越近,因而对室内的电磁环境污染逐步加剧。电磁辐射造成的危害通常包括对人体健康的危害(健康效应)和干扰其他电磁设备而造成严重后果(电磁干扰)。针对大功率中短波天线造成的电磁环境污染问题,提出一套远场条件下电磁辐射的预测方法并成功预测了一个典型大功率中短波天线群附近的拟建项目区域的电磁环境,在此基础上,提出有效的针对拟建项目的电磁防护方案。