Multi-block electret-based mechanical antenna model for low frequency communication

In an LF/VLF transmission system,the performance of the antenna is of great importance to the entire system.Currently,the electret-based mechanical LF/VLF antenna uses mechanical movement to accelerate electret charges to produce LF/VLF electromagnetic waves,and the frequency of these electromagnetic waves is limited by the rotation speed of the actuating motor.Based on research that addressed the relationship between antenna structure and electromagnetic wave frequency,this paper—in order to increase the frequency of electromagnetic waves—alters the charge distribution mode of the mechanical antenna while keeping the motor’s rotational speed constant to realize an increase of transmission signal frequency.The effectiveness of this method was verified by model simulation.

A Study on The Multi-Antenna Geometrical Depolarization Channel Modeling

The traditional geometrical depolarization model that single transmitter to single receiver provides a simple method of polarization channel modeling. It can obtain the geometrical depolarization effect of each path if known the antenna configuration, the polarization field radiation pattern and the spatial distribution of scatters. With the development of communication technology, information transmission spectrum is more and more scarce. The original model provides only a single channel polarization state, so the information will be limited that the polarization state carries in the polarization modulation. The research is so significance that how to carries polarization modulation information by using multi-antenna polarization state. However, the present study shows that have no depolarization effect model for multi-antenna systems. In this paper, we propose a multi-antenna geometrical depolarization model. On the basis of a single antenna to calculate the depolarization effect of the model, and through simulation to analysis the main factors that influence the depolarization effect. This article provides a multi-antenna geometrical depolarization channel modeling that can applied to large-scale array antenna, and to some extent increase the speed of information transmission.

An Error Equivalent Model of Revolute Joints with Clearances for Antenna Pointing Mechanisms

Joint clearances in antenna pointing mechanisms lead to uncertainty in function deviation. Current studies mainly focus on radial clearance of revolute joints, while axial clearance has rarely been taken into consideration. In fact, own?ing to errors from machining and assembly, thermal deformation and so forth, practically, axial clearance is inevitable in the joint. In this study, an error equivalent model(EEM) of revolute joints is proposed with considering both radial and axial clearances. Compared to the planar model of revolute joints only considering radial clearance, the journal motion inside the bearing is more abundant and matches the reality better in the EEM. The model is also extended for analyzing the error distribution of a spatial dual?axis("X–Y" type) antenna pointing mechanism of Spot?beam antennas which especially demand a high pointing accuracy. Three case studies are performed which illustrates the internal relation between radial clearance and axial clearance. It is found that when the axial clearance is big enough, the physical journal can freely realize both translational motion and rotational motion. While if the axial clearance is limited, the motion of the physical journal will be restricted. Analysis results indicate that the consideration of both radial and axial clearances in the revolute joint describes the journal motion inside the bearing more precise. To further validate the proposed model, a model of the EEM is designed and fabricated. Some suggestions on the design of revolute joints are also provided.

Mathematical Simulating Model of Phased-Array Antenna in Multifunction Array Radar

A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.

An Inductor Model for Analyzing the Performance of Printed Meander Line Antennas in Smart Structures

Meander line antenna has been considered desirable on flight vehicles to reduce drag and minimize aerodynamic disturbance;however, the antenna design and performance analysis have made mostly by trial-and-error. An inductor model by simulating the meander line sections as electrical inductors and the interconnecting radiation elements as a quasi-monopole antenna is developed to analyze the antenna performance. Experimental verifications of the printed meander line antennas embedded in composite laminated substrates show that the inductor model is effective to design and analyze. Of the 4 antennas tested, the discrepancy of resonant frequency in simulation and experiment is within 4.6%.

天气雷达站电磁环境影响监测研究

天气雷达站产生的超标电磁辐射会对人体造成严重的损伤。为此,提出天气雷达站电磁环境影响监测与分析。分析天气雷达站电磁影响因素,结合发射天线的方向函数,构建雷达功率密度模型。测试结果表明,对于S波、C波段、X波段,真实值与计算值呈现随距离增加而降低的趋势。对于三个波的频段,当接近天线的远场区时,计算值与真实值逐渐接近,相对误差均较小,说明模型在远场区的适用性更强;研究算法与实测值的拟合程度较高;在模型的应用中,真实反映了某市区的电磁辐射情况。

1.8 m车载雷达天线的风载数值模拟仿真分析

风载是雷达天线的主要载荷。采用ANSYS Workbench CFX软件的k-ε湍流模型对1.8 m车载雷达天线进行数值模拟,得出整个车载系统的压力云图以及天线工作面风压的分布特性,并计算出不同风向角下天线的阻力系数,与风洞试验结果进行比较。研究表明:数值分析计算结果与风洞试验结果比较吻合,风速变化虽然对风压有影响,但是对风载阻力系数影响很小。

基于单天线视轴信号传播模型的RFID定位方法

为了解决现有单天线超高频RFID技术在室内静态目标定位中精度不高的问题,本文提出了一种基于天线视轴信号传播模型的RFID定位新方法。该方法首先通过天线纵向扫描确定目标的高度位置;其次,调整天线高度与目标高度一致,然后步进旋转扫描以识别目标的方向角;进一步的,利用麻雀搜索算法优化的反向传播神经网络建立路径损耗模型并用于测距;最后,综合高度、方向角和距离数据完成目标的定位。实验结果表明,在室内环境测试中,所提出的方法平均定位误差为7.2 cm,能够满足一般室内场景下物品的定位需求。

并联天线机构尺度优化分析与验证

天线机构尺度优化设计是天线样机研制和工程应用的重要环节,将承载能力与驱动分支运动范围作为并联天线机构尺度优化目标,基于参数化设计模块开展尺度优化分析.首先对并联天线机构结构进行描述,建立了机构运动学模型;然后根据天线工作要求定义机构的设计变量、目标函数和约束条件,利用ADAMS优化设计模块建立机构的参数化模型;其次研究设计变量对目标函数的影响,得到综合性能优异的机构尺度参数;最后根据尺度优化结果研制天线样机并开展实验研究,实验结果表明,天线样机可实现预期运动且未出现干涉现象,其结果为并联天线机构的优化设计和样机研制提供参考.

Electromagnetic Analysis of the EAST 4-Strap ICRF Antenna with HFSS Code

A new ICRF antenna has been designed in EAST, whose aims are to reduce the parallel RF electric fields Ell and to investigate the current drive using the fast magnetosonic wave. This antenna consists of four toroidally spaced radiating straps. The electrical characteristics of the new antenna are estimated by using a three-dimensional electromagnetic commercial code. The S-parameters, RF current distribution and electromagnetic field distribution on and near the 4-strap antenna are analyzed, and the RF potentials influenced by antenna phasing and radial position are investigated.

空间可展开天线模态测试与模型修正技术

为准确预测结构的力学特性,使仿真结果精确逼近试验结果,必须对有限元模型进行修正。由于网状可展开天线的有限元模型中存在着各类结构参数且内部索网属于柔性结构,索网索段由于预张力才具有刚度,结构的这一特殊性导致模型修正困难。对3 m可展开天线样机进行了模态测试,在样机自由状态下获取了结构的模态频率和振型;针对可展开天线这种柔性复杂结构模态参数难识别、待修正参数多的特点,对修正参数进行了有针对性的选择;使用基于设计参数灵敏度型的模型修正方法对有限元模型进行了修正,缩小了样机与仿真固有频率和振型之间的误差,得到一种处理含有索网结构的模态测试流程和模型修正方法。

基于并联差速机构的通信天线及指向建模和跟踪方法

随着卫星星座互联网的发展及通信装备实战化升级换代,通信天线性能指标的要求越来越高。设计了一种基于并联差速机构的通信天线,介绍了通信天线的结构,分析了并联差速机构的原理,并进行通信天线指向建模和跟踪方法研究。在研究中,定义了运动数学模型,推导了解析式,进而得到跟踪方法。相较于传统采用串联驱动结构的通信天线,基于并联差速机构的通信天线具有刚度大、体积小、指向精度高等特点,在民品通信和军用通信领域具有良好的适用性。

5G基站对其他业务系统集总干扰的仿真分析方法

在分析5G系统与其他业务系统的兼容共存性时,计算5G基站对其他业务系统的集总干扰是最重要的研究内容之一。为解决传统蒙特卡洛仿真方法计算集总干扰计算量大、耗时长的问题,提出了一种基于系统抽样的计算方法。首先采用系统抽样的方法计算发射天线和接收天线的增益、传播损耗等仿真各环节的参数及其概率密度,然后根据乘法原理计算单一干扰链路的干扰信号功率及其概率密度,最后从单一干扰链路的全样本空间中进行抽样,计算集总干扰功率。仿真分析结果表明,所提方法能准确进行频谱兼容仿真分析,当对干扰台站大规模部署或对极低概率事件进行仿真时,可大幅提高仿真效率。

基于均匀分布偶极子的天线辐射场建模方法

针对雷达观测目标近场电磁散射的天线相关问题,发展了基于偶极子模型的天线辐射场建模方法。偶极子模型包括电偶极子与磁偶极子,其位置均匀分布于天线辐射口面,通过偶极子辐射场坐标变换和天线辐射场球面波展开(spherical wave expansion,SWE),建立了偶极子参数与天线辐射场SWE系数之间的线性矩阵方程,并采用奇异值分解(singular value decomposition, SVD)方法实现了偶极子参数的最小二乘估计。对喇叭天线、波导缝隙天线和微带贴片阵天线进行偶极子建模实验,建立了这三种天线辐射场建模误差小于1%的等效偶极子模型,通过对等效偶极子模型预测任意观测距离天线辐射场精度的评估,验证了基于均匀分布偶极子建模天线辐射场的有效性。

VICTS天线的波束指向误差补偿方法

针对可变倾角连续断面节阵列(Variable Inclination Continuous Transverse Stub,VICTS)天线的波束指向误差问题,提出了一种补偿方法。首先介绍了VICTS天线的基本原理和组成,建立了波束指向模型。然后分析了误差来源,包括结构误差、馈源层及辐射枝节层的角度关系等因素,通过仿真得出了波束指向角与馈源层和辐射枝节层夹角的关系。在此基础上,提出了通过二次曲线拟合进行误差补偿的方法,并进行了对星试验。实验结果表明,该方法能够有效减小波束指向误差,提高通信系统的性能,具有较高的实用性。

基于正确解码率的ADS-B天线配置模型分析

提出一种广播式自动相关监视(ADS-B)天线配置分析模型,该模型可实现基于本地具体情况获得满足空管管制要求的ADS-B天线部署方案,为后续ADS-B站点部署实施时选择定向/全向天线提供决策工具。本文以报文正确解码率作为评估定向/全向天线效果的直接指标,从飞机数量、雷达/TCAS部署情况、飞机应答/广播速率等3个角度出发,获得空域单目标每秒发送报文的数量,分析其与定向/全向ADS-B接收设备报文解码率的关联性,从而得到定向天线与全向天线配置下报文解码率分析模型,然后设置模型相关参数,通过模型解算获得相应的正确解码率。通过实际录取数据对该模型正确性进行相关验证,结果与理论模型基本保持一致,证明ADS-B天线配置分析模型是正确有效的。

钢塔桅结构与天馈线系统检测设计加固维护一体化模式标准及应用

随着广播、电视以及通讯事业的不断发展,钢塔桅结构及其上架设的天馈线设备得到越来越广泛的关注,广播电视发射塔钢塔桅结构和天馈线系统整体可靠性成为保障安全播出的重要基石。提高钢塔桅安全冗余度,保证天馈线系统正常运行,“检测、设计、加固维护一体化”是有效预防、解决安全播出事故的重要举措,三个环节相辅相成,缺一不可,传统的“分部实施、单项解决”已不再适用,“检测、设计、加固维护一体化”将成为管理模式的必然趋势。本文以工程案例为基础,详细探究广播电视发射塔“检测、设计、加固维护一体化”应用过程,总结应用要点,验证加固改造方案的可靠性,为今后类似项目的实施提供了参考。

主动主反射面天线促动器调整量计算与误差分析

主动主反射面天线通过调整安装在面板下方的促动器来提高表面精度,现有的促动器调整量计算方法多数忽略了面板弹性变形对调整精度的影响。文中通过力学仿真模拟来表征促动器调整过程对面板自身弹性变形的影响。首先,构建单块反射面面板变形拟合模型,并对拟合模型的权重进行优化,进而推导出整个反射面的变形拟合模型;其次,考虑到实际工程中相邻面板共用促动器,因此对促动器编号进行归并,进而推导出相邻面板共用促动器时促动器最佳调整量的计算模型。为了验证面板变形拟合模型的计算精度,分别从拟合模型的变形表征能力和促动器调整量的计算精度两个方面开展仿真验证工作,并从促动器调整误差和促动器故障两个方面分析促动器调整误差对反射面调整精度的影响,为工程中评估促动器调整精度提供参考。

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。

A new calibration model for pointing a radio telescope that considers nonlinear errors in the azimuth axis

A new calibration model of a radio telescope that includes pointing error is presented, which considers nonlinear errors in the azimuth axis. For a large radio telescope, in particular for a telescope with a turntable, it is difficult to correct pointing errors using a traditional linear calibration model, because errors produced by the wheel-on-rail or center bearing structures are generally nonlinear. Fourier expansion is made for the oblique error and parameters describing the inclination direction along the azimuth axis based on the linear calibration model, and a new calibration model for pointing is derived. The new pointing model is applied to the 40 m radio telescope administered by Yunnan Observatories, which is a telescope that uses a turntable. The results show that this model can significantly reduce the residual systematic errors due to nonlinearity in the azimuth axis compared with the linear model.