Effect of Partial Ground Plane Removal on the Radiation Characteristics of a Microstrip Antenna

This study presents a new, simple method for reducing the back-lobe radiation of a microstrip antenna (MSA) by a partially removed ground plane of the antenna. The effect of the partial ground plane removal in different configurations on the radiation characteristics of a MSA are investigated numerically. The partial ground plane removal reduces the backlobe radiation of the MSA by suppressing the surface wave diffraction from the edges of the antenna ground plane. For further improving the front-to-back (F/B) ratio of the MSA, a new soft-surface configuration consisting of an array of stand-up split ring resonators (SRRs) are placed on a bare dielectric substrate near the two ground plane edges. Compared to the F/B ratio of a conventional MSA with a full ground plane of the same size, an improved F/B ratio of 9.7 dB has been achieved experimentally for our proposed MSA.

Different Feeding Techniques of Microstrip Patch Antennas with Spiral Defected Ground Structure for Size Reduction and Ultra-Wide Band Operation

Different feeding techniques of microstrip patch antennas with different spiral defected ground structures are presented in this paper. The investigated structures illustrate some merits in designing multi-electromagnetic band-gap structures by adjusting the capacitance and changing the inductance through varying the width and length of spiral defected ground structure. Then by applying the three different spirals shapes (one, two and four arms) as the ground plane of microstrip patch antenna with different feeding techniques to create multi or ultra wide-band, improve the antenna gain and reduce the antenna size, it is found that the four arms spiral defected ground structure of microstrip patch antenna with offset feed gives good performance, electrical size reduction to about 75% as compared to the original patch size and ultra-wide bandwidth extends from 2 GHz up to 12 GHz with ?8 dB impedance bandwidth.

Predicting Ground Effects of Omnidirectional Antennas in Wireless Sensor Networks

Omnidirectional antennas are often used for radio frequency (RF) communication in wireless sensor networks (WSNs). Outside noise, electromagnetic interference (EMI), overloaded network traffic, large obstacles (vegetation and buildings), terrain and atmospheric composition, along with climate patterns can degrade signal quality in the form of data packet loss or reduced RF communication range. This paper explores the RF range reduction properties of a particular WSN designed to operate in agricultural crop fields to collect aggregate data composed of subsurface soil moisture and soil temperature. Our study, using simulation, anechoic and field measurements shows that the effect of antenna placement close to the ground (within 10 cm) signi?cantly changes the omnidirectional transmission pattern. We then develop and propose a prediction method that is more precise than current practices of using the Friis and Fresnel equations. Our prediction method takes into account environmental properties for RF communication range based on the height of nodes and gateways.

Triple-Band L-Shaped Monopole Antenna with Defected Ground Plane for WLAN and WiMAX Application

This paper presents the simulation and measured results of a triple-band L-shaped monopole antenna with defected ground plane for applications in wireless local area networks（WLANs） and worldwide interoperability for microwave access（WiMAX） bands.The triple-band L-shaped monopole antenna with defected ground plane was fabricated on a FR4 substrate. The lower band is associated with the shorted parasitic strip in the protruding stub of the ground plane; the middle band is expected to be controlled by the longer strip of L-shaped monopole in the front side,while the higher band is associated with the short strip of L-shaped monopole in the front side. The proposed antenna has a good agreement between the measured and the simulation results. It has a 10 d B return loss with the bandwidth of 250 MHz（2270 MHz to 2520MHz） in the lower band, 600 MHz（3320 MHz to 3,920MHz） in the middle band, and 1110 MHz（5030 MHz to6140 MHz） in the higher band. The proposed antenna covers the ISM（industrial, scientific and medical）,HIPERLAN（high performance radio local area network）, UNII（unlicensed national information infrastructure）, and WiM AX bands.

Increasing Microstrip Patch Antenna Bandwidth by Inserting Ground Slots

Microstrip patch antenna (MPA) is widely implemented in different communication systems. One of the main disadvantages of MPA which limits its applications is its narrow bandwidth. In this paper I enhanced the bandwidth of MPA by inserting multiple slots in its ground plane. I used FR-4 substrate to design this antenna. The dimensions of this antenna are 59 mm and 79 mm. The dielectric constant is 4.4 and the height is 1.6 mm. I inserted up to 15 slots in ground plane with 1mm width. The spacing between slots is 3 mm. I investigated two designs. In the first design, slots were arranged in parallel to the feeding line. In the second one, slots were arranged horizontally to the feeding line. The main objective of this paper is to design and simulate MPA suitable for wide number of applications. Antenna bandwidth improvement is 18%. All the simulations were obtained by using HFSS simulator.

Stitched Ground Planes for Textile Antenna Application: An Experimental Study

This paper presents an application of stitched ground plane for microstrip patch antenna design. In this work Matlab interface to computer embroidery techniques were used to implement the felt and denim substrates on microstrip patch antenna. These antennas were simulated using a commercial full 3D electromagnetic CST Microwave Studio 2019. A method to optimize the stitch patterns with conductive thread for antenna ground plane for 2.45 GHz industrial, scientific, and medical (ISM) band and 5 GHz wearable wireless local area networks (WLAN) frequencies was achieved. Rigid and flexible wearable antennas (microstrip patch antennas) were fabricated using the stitched ground plane. The electrical resistance was reduced between the meshes during the stitching design process. Results in terms of bandwidth, radiation patterns and reflection coefficients (S11) are presented.

一种分段的超短波对数周期天线设计与实验

超短波的传播方式主要为视距传播,这种传播方式需要天线具有强方向性且有较高的增益。而对数周期天线是一种超宽带、中等增益的天线,非常适用于超短波通信。然而在超短波频段下,常规对数周期天线的长度较长,小型化程度不高。为了实现超短波对数周期天线的小型化,提出一种分段的超短波对数周期天线的设计方案。根据应用需求,在满足天线增益的情况下,采用分段设计缩减天线长度,同时调整集合线之间的夹角,以实现天线的阻抗匹配。经过仿真设计,天线在30~70 MHz频段内典型增益大于8 dBi,天线的长度缩减至7 m。采用基于无人机飞行平台的外场测试系统对天线进行实验测试,测试结果表明,天线在工作频率范围内驻波比小于1.5,测试与仿真的辐射特性基本一致。该天线具有带宽宽、增益高、结构简单等特点,可以满足实际场景中超短波天线的需求。

探地雷达介质谐振天线的原理研究

为了增加探地雷达的探测深度,提高探地雷达增益,本文从物理学中周期性力作用下的阻尼振动的角度出发,推导周期信号作用下电磁波在介质谐振天线中的谐振过程,阐述了天线的基本工作原理,并对其谐振放大作用进行了仿真.研究发现,在周期信号作用下,天线谐振腔内的信号通过谐振形成驻波实现能量增强,证明了以时间换取能量是可行的.这种谐振放大作用使天线具有更高的辐射功率,对解决探地雷达的探深问题具有重要意义.

有限大接地板对圆极化微带贴片天线等化波束宽度影响的研究

基于数值仿真和实验测量,研究了接地板尺寸对微带贴片天线圆极化等幅条件的影响规律。结果表明:当接地板尺寸变化时,铅垂极化分量幅度(|E_(θ)|)和水平极化分量幅度(|E_(φ)|)受到地板尺寸变化的敏感度和规律不同,从而影响了圆极化天线主波束范围内保持其幅值相等的条件。最终推得接地板尺寸在0.6~1.0波长范围内,铅垂、水平极化分量保持等幅条件(按幅度差不大于3dB计)的“等化波束宽度”经验公式,为可穿戴圆极化贴片天线的波束宽度调控及选择提供理论依据。

天线外场测试中地面反射的影响分析

低频天线外场测试时往往很难彻底消除地面反射的影响,而地面反射波对直达波的矢量叠加导致待测天线口面上场强分布不均匀,引入较大的测试误差。为消除或减小误差,本文通过建立地面反射模型分析了收发天线高度、收发天线水平距离及地面反射特性对待测天线口面上的反射波或合成场的影响,推导了合成场分布、最佳发射天线高度等计算公式。利用该模型基于实测数据拟合得到地面反射系数幅度和相位,从而得到优化后的测试天线布局。本文基于该模型对外场测试天线高度进行优化后,待测天线口面垂直方向上场强幅度最大值与最小值比值由5.4 dB降到1 dB以内,证明了该分析方法的有效性。该方法可用于低频大口径天线的外场测试方案设计及试验验证工作。

地网部分架空对长波天线影响分析

长波天线的损耗主要来自地损耗电阻,通过在天线正下方铺设埋地地网可以改善损耗电阻,提高长波天线辐射效率。然而受实际地形影响,需要对地网进行部分架空。本文使用基于矩量法的全波仿真计算工具,分析部分地网架空对单塔伞形长波天线电气性能的影响,为长波天线工程实施和地网维修改造提供指导作用。

水平分层大地对低架天线电流分布影响分析

论文研究在水平分层大地条件下,不同接地方式对甚低频水平低架天线在有耗半空间中的电流分布特性。建立了水平低架天线的数学结构模型,理论推导了甚低频水平低架天线的电流分布公式,采用数值分析软件解析了大地介质层厚度、电导率对天线电流分布的影响。结果表明,在改变大地上下介质分层厚度时,对于中间馈电的天线,采用两端接地的方式比两端架空方式的天线性能好约0.485%。同样,改变大地上下介质层电导率时,采用天线接地的方式比架空的方式的性能好约0.385%。

双频一体化超宽带探地雷达天线设计

针对目前探地雷达(Ground Penetrating Radar,GPR)产品单一频段工作所导致的耗时费力、效率低等缺点,文中设计实现了一种中心频率分别为400 MHz、1000 MHz且带宽为200~1500 MHz的双频一体化复合阵列天线,并将其应用于超宽带(Ultra-Wide Band,UWB)探地雷达系统中。阵列天线包含3个中心频率为400 MHz和6个中心频率为1000 MHz的蝶形天线,具备双频段同时探测能力,可实现一条测线含两种不同频段的探测结果,克服了传统探地雷达不同频率的重复探测问题,增强了探地雷达系统的实用性。所提出的双频一体化探地雷达天线具有超宽带、高增益、波束窄等特点,其相对带宽为153%,整个带宽内最高实现17.6 dBi峰值增益,半功率波束宽度最窄为7.6°,为高分辨率、高效率探地雷达应用提供了一种新的天线方案。

一种低驻波宽角波束超宽带双锥线阵列天线研制

设计和制作了一种实现宽角波束扫描的1×3超宽带双锥线极化阵列天线,可以应用于无人机上实现空地宽带通信。由于无人机平台安装尺寸受限,通过用椭球形阵子代替传统锥形阵子,并切割椭球振子外部轮廓使其安装在250 mm×130 mm×90 mm的空间内,实现了低剖面、小型化等特点。仿真结果表明,该阵列天线在0.8~2.4 GHz的频带范围内电压驻波比均小于2.5,在±45°波束扫描范围内的4个波束的最低增益均超过了2 dBi,满足实际的应用需求。

一种多天线地面站的设备级资源调度算法

针对多天线地面站接收设备共享使用的需求,设计了一种设备级资源调度算法,以充分利用站内设备资源,提高地面站任务能力。首先,分析了多天线地面站资源调度需考虑的各类约束,并建立了各类调度资源和关系模型。然后,将所有卫星接收任务的时间分布抽象为无向图,通过定义边的权重计算任务冲突度。最后,提出了基于优先级和匹配性的概率选择算法,以迭代方式实现调度方案的寻优。仿真结果显示,所提算法的平均调度成功率较优先级算法和遗传算法分别提高了11.9%和6.9%,有效提高了接收设备使用效率。

迁址导致电磁环境变化对中波发射系统影响的研究

中波广播发射系统的搬迁不仅需要技术上的精准操作,还需要管理上的科学规划与协调。本文详细介绍了现有电磁环境情况,并分析了迁入后新电磁环境对中波广播发射系统可能产生的具体影响。技术团队需制定详细的迁入方案,全面考量新环境的电磁条件,识别潜在问题,并提出相应的应对措施。文章还提出了相关的解决方案和具体的迁入建议,以确保搬迁过程的顺利进行。通过充分的新电磁环境分析调研,为台站的迁入提供了重要的参考依据。

天线地网对中波广播发射效果的影响

中波广播作为一种传统信息传播手段,在偏远地区和特定应用场景中发挥着重要作用。然而,中波广播在传播过程中面临着一系列问题,会直接影响广播信号的清晰度和接收质量。基于此,分析天线地网对中波广播发射效果的影响,并提出一系列优化天线地网设计的策略,旨在实现中波广播传播效率的最大化,为偏远地区提供更稳定的广播服务。

实时三维探地雷达关键技术的设计与实现

为了提高市政道路检测水平,快速有效地解决市政道路塌陷灾害预警、市政管网分布查找等问题,设计研发了一款实时三维探地雷达。实时三维探地雷达基于FPGA&DSP架构,完成了多通道高速采集系统多个关键技术的设计与实现,丰富了道路检测领域的探测技术和方法。实时三维探地雷达天线采用五发六收模式的水平极化方式,实现了十通道雷达数据高速采集,通道间通过高速开关实现切换,所有通道以交互内插方式进行工作;雷达最大可支持扩展到32通道工作,用开关切换天线阵列,满足60 km/h(2cm道间隔)以上的探测速度。通过对空洞实验场和金属板实验场的实验数据进行对比,验证了最佳的天线极化方式设计,最终确定了天线的最优方案。实测结果表明,相比于通用的LTD-2600型雷达,实时三维探地雷达具有更高速的采集速度以及良好幅度与相位性能,有利于改进道路灾害的检测技术,具有较大的市场需求。

基于缺陷地和开口谐振环的三频段小型化天线

提出了一种新型三频段工作的小型微带贴片天线,天线采用不对称结构,在接地板上引入缺陷地结构(DGS)改变了天线表面电流分布,改善工作频率,衍生在无线局域网(WLAN)(2.4 GHz)处的频带。加载开口谐振环(SRR)金属环结构在独立控制WLAN(5.8 GHz)的频带的同时,减小了12%的天线体积。天线结构紧凑,整体尺寸为12.5 mm×28.5 mm×1.5 mm。结果表明,天线覆盖3个独立的阻抗带宽,分别为800 MHz(1.96~2.76 GHz),200 MHz(5.65~5.85 GHz)和1 460 MHz(7.64~9.1 GHz),在频段内的回波损耗均小于-10 dB,具有良好的方向性和增益,支持WLAN(5.8/2.4 GHz)频段和国际电信联盟(ITU)(8.0~8.7 GHz)频段的应用。

低轨卫星微波毫米波PCB的技术发展与应用

低轨卫星移动通信系统与地面5G移动通信系统相融合,以及未来的6G时代,将推动构建全域内无缝覆盖和全时接入的通信网络、实现空天地海一体化。卫星通信向微波毫米波频段演进已成为发展趋势,与此同时也面临着更大的挑战。本文从互联网的概念入手,介绍了目前国内外低轨卫星技术发展及其应用进展,梳理了低轨天上端与低轨地面端两类PCB产品,阐述了用于降低PCB重量的低密度发泡材料PMI(聚甲基丙烯酰亚胺)混压加工技术、相关高频高速材料选型加工及其非对称结构的板翘控制技术、毫米波封装天线与阵列天线技术研究等关键技术,希望对低轨卫星工程推广和相关PCB加工制造产生一定的积极意义。