基于Labview的甚低频场强远程监测系统设计

天线的辐射效率反映了天线的辐射能力,是一个甚低频天线最关键的指标,效率需通过场强测量获得。要使天线的辐射效率达到最大,如何根据实时测量的场强值调整天线的发射参数是问题的关键。本文构建了基于Labview的甚低频(VLF)场强远程监测系统。该系统可对甚低频场强信号进行实时的监控和测量。     

柔性标签弯曲及对RFID系统识读距离的影响研究

针对平面结构标签在使用过程中经常发生弯曲形变的问题,研究一种柔性标签发生圆弧形弯曲和垂直折叠形变时天线性能的变化以及对RFID系统识读距离的影响。介绍柔性标签天线的研究现状,分析影响RFID系统识读距离的关键因素,通过示意图阐述弯曲天线模型的建模方法,基于HFSS仿真分析阻抗、增益和辐射效率等的变化规律。通过实际测量验证了RFID系统识读距离的仿真结果及该方法的可行性。     

卫星通信链路性能分析

针对卫星通信链路传输中对性能参数的分析存在系统误码率过大的问题,提出了一种卫星链路传播特性模型,并在传统正推法的基础上,运用一种新的链路预算方法--倒推法（Backward Pass Algorithm）。该方法通过反向推导、计算出系统载噪比、衰减余量来求得发射端的有效全向辐射功率（Effective Isotropic Radiated Power）值,根据不同情况对EIRP进行动态调整,可以更好地提高地面站的信号传输质量。仿真结果表明,实际情况中,该方法可对地区、天线仰角等不同条件影响下发射端的辐射功率进行优化,在满足系统误码率的同时,提高了系统功率利用率。     

弯折线偶极子射频识别标签天线设计方法研究

由于弯折线偶极子天线具有体积小,辐射效率相对较高等优点,常常被用来设计射频识别标签天线.提出了一种通过弯折线偶极子天线尺寸计算其电感值,从而间接求解谐振频率的方法,分析了设计一般弯折线偶极子天线尤其是应用于射频识别标签的弯折线偶极子天线的局限性,辐射效率低.针对上述问题,提出了改进方法.并利用仿真软件和实验对此改进方法进行验证.仿真及实验结果表明,改进后的计算方法能够跟据已知的谐振频率设计出相应的弯折线偶极子标签天线外形,从而简化了设计步骤,缩短了设计周期,提高天线的效率和准确性.     

相控阵天线等效全向辐射功率测试方法

等效全向辐射功率（EIRP）是发射天线的一项重要指标。在矢量网络分析仪双通道接收模式天线远场测试系统的基础上,通过线极化天线、圆极化天线、椭圆极化天线EIRP公式推导,阻抗失配修正,提出一种准确测量相控阵天线不同极化合成波束等效全向辐射功率的方法,并给出各种极化波的转换关系。最后结合实测举例,通过相关试验证明该方法的可行性。     

天线辐射功率的时空分布仿真

在涉及到天线的仿真中，天线辐射功率时空分布的计算和建模是一个关键问题，对仿真结果的逼真度有重要影响。对影响天线辐射功率分布的主要因素进行了分析，认为在现代高科技条件下，执行重要任务的各种天线往往要频繁的发射不同波长的信号，这时天线的最大增益是变化的，在分析和仿真辐射功率分布时应根据不同的发射频率实时求解最大增益。推导了天线发射不同波长信号时的最大增益求懈方法，然后归纳总结了对天线辐射功率的时空分布进行仿真的方法和步骤，并以一个示例来具体说明仿真过程。所论述的方法已应用到某型模拟训练器项目中，实际应用证明可行。     

基于镜像法的矿井隧道电磁波多径信道模型

针对矿井隧道复杂的电磁波传播环境,利用镜像法建立了矿井隧道电磁波多径信道模型,给出了三维空间的锯齿螺旋射线总传播路径长度和入射角、反射角的计算方法,以及总的接收功率和传输损耗的表达式。仿真结果表明,靠近发射天线的电磁波场强衰减较大,呈现快衰落现象,所建模型能准确预测隧道中电磁波场强分布。     

基于RCS的无源超高频RFID标签识别距离研究*

通过对无源超高频RFID系统中标签功率的获取、传递以及反射的研究,提出了一种基于雷达散射截面(RCS)对标签识别距离进行计算的新方法。采用高频电磁场仿真软件FEKO对不同标签天线进行建模与仿真,计算标签天线在不同负载下的RCS;再结合识别距离表达式计算该标签的最大识别距离,与标签已有的实测参数进行比较,计算结果与实际参数吻合。研究结果证实了该方法对研究标签识别性能具有很好的借鉴意义。     

雷达测试用标准增益天线智能伺服系统设计与实现

微波标准增益喇叭天线由于增益准确、轻质便携等优点,经常用于雷达外场测试;然而极易被人们所忽略的是:天线的架设精度对于能否准确测量同样影响很大;传统测量架设天线的方法是:根据天线所接仪器功率示值变化,人工调节天线姿态,找出最强信号位置后再将天线固定,其缺点是人员遭受辐射,架设效率和准确度较低;该系统采用硬件部件集成,软件优化控制,实现了标准增益天线的快速自动精确架设,通过天线架设时间、架设准确度和重复性等试验数据表明,相比传统方法其测试效率和测量准确度均大为提高。     

MEMS层叠式毫米波天线设计

为了提高天线带宽,改善天线性能,提出并设计了一种基于微机械工艺的层叠式口径耦合毫米波天线,该天线中心频点为35 GHz,利用有限宽地共面波导-微带(FGCPW-MS)进行馈电.分析天线结构中的几个关键参数对天线带宽性能的影响,利用HFSS三维电磁场仿真软件进行天线模型仿真.结果表明,该天线带宽为11.8%,增益为7.8 dB,天线辐射效率为71%.与传统微带天线相比,该天线在带宽、增益等方面均到改善,且易与其他有源元件进一步集成.     

Experimental investigation and comparison of super‐wideband antipodal slot antennas

Three novel, super‐wideband antipodal slot antennas with different tuning stubs are studied and compared with each other. Smooth, half‐circular slot profile is used to improve the antennas' polarization purity and impedance bandwidth, and different tuning stubs are used to finely tune the antennas' radiation performance. As will be reported, low crosspolarization level, stable dipole‐like pattern, and flat gain performances can be obtained within an operation bandwidth of 6.3:1 by introducing a smooth antipodal slot structure and a cup‐shape tuning patch. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

机载天线方向图外场测试技术研究

机载天线装机后,受到机身和机翼的遮挡影响以及载机平台的耦合和散射作用,实际覆盖范围会发生变化,从而引起天线方向图的畸变,使得天线的性能偏离预期效果。在暗室内进行整机天线方向图测量不仅要求暗室静区尺寸足够大,而且对暗室低频性能的要求也很高,因此,室外露天测量是一种可替代的方法。设计了装机天线外场环境测试平台,提出了一种装机天线外场天线方向图校准方法,能够对外场装机天线不同频点的方向图等参数进行测试和校准。外场试验结果验证了所提方法的有效性。     

Broadband and high-aperture-efficiency metasurface antenna using multi-mode radiator

A high-aperture efficiency and broadband metasurface antenna array with multi-mode radiator is put forward in this article. The abnormal slot is etched at the center of the ground plane and fed to the antenna via a microstrip line. Resonant along the slot line, and in the electric field, two short horizontal lines with uniform gaps are symmetrically added near zero. Additional radiation modes have been introduced. Then, broadband slot antenna with two resonances is obtained by combining full-wavelengths provided by the first slot. Working bandwidth increased from 7.6% to 21.1%. By introducing a ring slot, the antenna gain is increased by 0.9 dBi. At the same time, the aperture efficiency is modified by 12.9%. A 2 × 2 array was made to verify the design, with an overall size of 2.01λ₀× 2.01λ₀ × 0.07λ₀. The simulation and measurement results show that the operating bandwidth is 38.9% with maximum gain is 15.8 dBi.     

Probabilistic positioning in mobile phone network and its consequences for the privacy of mobility data

The traditional approach to mobile phone positioning is based on the assumption that the geographical location of a cell tower recorded in a Call Details Record (CDR) is a proxy for a device's location. A Voronoi tessellation is then constructed based on the entire network of cell towers and this tessellation is considered as a coordinate system, with the device located in a Voronoi polygon of a cell tower that is recorded in the CDR. If Voronoi-based positioning is correct, the uniqueness of the device trajectory is very high, and the device can be identified based on 3–5 of its recorded locations.We investigate a probabilistic approach to device positioning that is based on knowledge of each antennas' parameters and number of connections, as dependent on the distance to the antenna. The critical difference between the Voronoi-based and the real world layout is in the essential overlap of the antennas' service areas: The device that is located in a cell tower's polygon can be served by a more distant antenna that is chosen by the network system to balance the network load. Combining data on the distance distribution of the number of connections available for each antenna in the network, we resolve the overlap problem by applying Bayesian inference and construct a realistic distribution of the device location. Probabilistic device positioning demands a full revision of mobile phone privacy and new full set of tools for data analysis.     

二维测试转台偏心误差修正技术研究

雷达天线阵面在暗室或外场测试时,由于转台及天线阵面结构的限制,天线阵面的电气中心不可避免地偏离测试转台的回转中心,因而造成测试误差。使用齐次坐标变换理论建立二维转台和被测天线的坐标变换数学模型,准确求得二维转台在任意伺服角度时,被测目标相对天线阵面的坐标值。仿真结果表明：在40 m跨度的暗室内,天线测试精度可提高0.5°。     

Closed-form expressions for computer-aided design of microstrip ring antennas

This article presents closed-form expressions for the resonant frequency and radiation characteristics of microstrip ring antennas to assist in the computer-aided design of such antennas. Radiation fields are obtained using the vector electric potential calculated from the magnetic currents flowing along the inner and outer edges of the planar waveguide model for the microstrip ring structure. Expressions for radiated power, conductor and dielectric loss factors, resonant resistance, efficiency, and directivity are derived. The smaller the radius of curvature of the ring, the larger is the spacing between the magnetic currents flowing along the inner and outer edges and thus the radiation efficiency is higher. The effect of a dielectric layer covering the ring antenna is also included. Experimental results for the resonant frequency and the radiation patterns agree well with the theoretical predictions. © 1992 John Wiley & Sons, Inc.     

A novel computational intelligence method for broadband dual-polarized base station antenna design

Broadband dual-polarized base station antenna requires wide impedance matching bandwidth, high-polarization isolation, stable radiation patterns, small gain variations, and high-cross polarization discrimination level. For antenna designers, it usually takes much computational time to design broadband base station antenna because there are extensive structural parameter analysis and multiple performance characteristics to be synthesized one by one. In this paper, a novel population-based computational intelligence optimization method is proposed for broadband base station antenna design. The proposed optimization method is based on self-adaptive weight vector strategy and could speedup searching through adjusting weight vectors and decreasing the number of full-time objective function evaluations. To verify its high efficiency of the proposed optimization method, a compact broadband dual-polarized base station antenna operating at 3.3–5.0 GHz is designed. From measurement results, it is observed that polarization isolation is higher than 27 dB, gain variation is smaller than 0.4 dB, and half-power beamwidth (HPBW) is within 65° ± 3°. In addition, XPD level is better than 24 dB at boresight direction and better than 13 dB within a sector of ±60°. Therefore, the designed antenna is promising for 5G broadband cellular base station applications.     

透地通信系统天线小型化设计与测试

针对现有透地通信系统天线尺寸较大、可移动性差、无法实现双向通信的问题,设计了中心频率为500kHz的中波小型方环天线,并对天线的阻抗特性、匹配性能及通信距离进行了理论分析及测试研究。测试结果表明,天线与信号源之间实现了良好的阻抗匹配,匹配网络效率近似为1;天线工作带宽约为8kHz,天线效率为6.1×10-5,与理论计算结果近似相等;天线具有良好的辐射特性,在输入功率为0.25W时有效传输距离为30m。     

嵌入豁口磁芯的13.56MHzRFID读写器天线

本文针对天线线圈产生的磁场强度分布不均匀的现象,提出一种增强天线局部磁场强度的方案.首先,本文从理论出发解释了高频磁场的趋肤效应;其次,基于高频磁场的趋肤效应,提出往线圈中央添加开了豁口的金属磁芯,用以增强磁芯边缘和豁口位置的磁场强度;最后,通过三维电磁仿真软件AnsoftHFSS和MATLAB软件研究不同张角的豁口磁芯对环形天线的磁场强度的影响,旨在找出最优豁口的设计方案,对实际设计的13.56MHz RFID读写器天线具有一定的参考价值.     

矿井提升机自适应无线通信系统设计

目前,矿井提升机有线通信系统布线繁琐、检修复杂,而无线通信系统因发射功率、频率和天线辐射方向固定,存在无线通信距离有限、信号无法根据井筒形状和长度灵活覆盖、通信信号不稳定等弊端。针对上述问题,设计了一种矿井提升机自适应无线通信系统。该系统所有设备的数据均通过以太网接口输入,无线通信部分采用接收信号强度自动感知、工作频率和辐射波束自动调整的自适应天线,可以将无线摄像仪、无线电话等矿用设备进行无线互连,实现提升机、罐耳、油缸、钢丝绳及天轮等主要设施的视频监视、数据监测及语音通信。当提升机运行时,系统根据立井井筒的结构、深度与尺寸,自动调整位于井筒顶部的天线的工作参数,使得天线能够始终对准移动中的提升机,通信设备的工作频率和功率始终处于最佳状态,保证了无线信号的良好覆盖。现场应用结果表明,提升机运行时地面调度人员能够实时监视天轮、井筒、罐耳及提升机内部状况,可随时与提升机内人员通话,图像清晰,语音通信流畅,且设备功耗低。