Omnidirectional Antenna Diversity System for High-Speed Onboard Communication

In this article,an omnidirectional dual-polarized antenna with synergetic electromagnetic and aerodynamic properties is propounded for high-speed diversity systems.The propounded antenna comprises a probe-fed cavity for horizontally polarized radiation and a microstrip-fed slot for vertical polarization.Double-layer metasurfaces are properly designed as artificial magnetic conductor boundaries with direct metal-mountable onboard installation and compact sizes.An attached wedge-shaped block is utilized for windage reduction in hydrodynamics.The propounded antenna is fabricated for design verification,and the experimental results agree well with the simulated ones.For vertical polarization,the operating bandwidth is in the range of 2.37–2.55 GHz,and the realized gain variation in the azimuthal radiation pattern is 3.67 decibels(dB).While an impedance bandwidth in the range of 2.45–2.47 GHz and a gain variation of 3.71 dB are also achieved for horizontal polarization.A port isolation more than 33 dB is obtained in a compact volume of 0.247λ_(0)×0.345λ_(0)×0.074λ_(0),whereλ_(0)represents the wavelength in vacuum at the center frequency,wherein the wedge-shaped block is included.The propounded diversity antenna has electromagnetic and aerodynamic merits,and exhibits an excellent potential for high-speed onboard communication.

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.

Improved Measurement Method of Circularly-Polarized Antennas Based on Linear-Component Amplitudes

An improved measurement method of circularly-polarized (CP) antennas based on linear-component amplitudes is proposed in this paper. By utilizing two sets of orthogonal linear polarization (LP) amplitudes, measurement on axial ratio (AR) of CP antennas can be realized without phase information. However, the rotation sense of the co-polarization cannot be determined due to the absence of the phase information. Above problem is discussed here for the first time, and a solution is presented to determine the rotation sense of the co-polarization by using common auxiliary CP antennas. In addition, there will be some particular cases with large errors in actual measurement. Here a corresponding solution method is given. Finally, co-polarization and cross-polarization patterns can be further obtained from AR results. To verify this improved method, a self-developed CP microstrip array was measured. The measured results are in agreement with the simulated results, which prove this method is correct, effective and practical.

Studies on omnidirectional enhancement of giga-hertz radiation by sub-wavelength plasma modulation

The technology of radio frequency （RF） radiation intensification for radio compact antennas based on modulation and enhancement effects of sub-wavelength plasma structures represents an innovative developing strategy. It exhibits important scientific significance and promising potential of broad applications in various areas of national strategic demands, such as electrical information network and microwave communication, detection and control technology. In this paper, laboratory experiments and corresponding analyses have been carried out to investigate the modulation and enhancement technology of sub-wavelength plasma structure on the RF electromagnetic radiation. An application focused sub-wavelength plasma-added intensification up to ~7 dB higher than the free-space radiation is observed experimentally in giga-hertz （GHz） RF band. The effective radiation enhancement bandwidth covers from 0.85 to 1.17 GHz, while the enhanced electromagnetic signals transmitted by sub-wavelength plasma structures maintain good communication quality. Particularly, differing from the traditional RF electromagnetic radiation enhancement method characterized by focusing the radiation field of antenna in a specific direction, the sub-wavelength plasma-added intensification of the antenna radiation presents an omnidirectional enhancement, which is reported experimentally for the first time. Corresponding performance characteristics and enhancement mechanism analyses are also conducted in this paper. The results have demonstrated the feasibility and promising potential of sub-wavelength plasma modulation in application focused RF communication, and provided the scientific basis for further research and development of sub-wavelength plasma enhanced compact antennas with wide-range requests and good quality for communication.

小型化低剖面全向滤波天线设计

设计了一个小型化全向微带滤波天线。天线由带通滤波器和微带天线组成,二者共用一个地平面以减小尺寸且采用缝隙耦合方式连接,带通滤波器蚀刻在微带贴片天线的馈线位置处,引入选频滤波功能,在输入馈线前端添加一个横向矩形贴片使整个系统达到良好的阻抗匹配。与传统的微带天线相比,所设计的滤波天线在不改变尺寸大小的基础上引入了选频滤波功能,在通带边缘体现出较高的选择性。仿真与测试结果表明,该滤波天线的阻抗带宽为2.31 GHz~2.56 GHz,且通带内增益平缓,平均增益约为2.1 dBi,在工作频段内呈全向辐射特性。

基于双螺旋结构的紧凑型全向圆极化天线

针对混合法向模螺旋天线方向图不对称问题,提出了一种基于双螺旋法向模的紧凑型全向圆极化天线。该天线主要由两种不同尺寸的螺旋、连接不同尺寸螺旋的两对金属短棒以及馈电巴伦组成。其中,大小螺旋分别主要贡献水平极化和垂直极化,从而实现全向圆极化辐射。相对于单螺旋法向模天线,该双螺旋天线结构更对称,能够实现更为均匀的全向辐射方向图。同时,利用两对金属短棒将大小螺旋进行级联,天线结构更加紧凑,横向尺寸仅为0.15λ。研究结果显示,该天线仿真轴比带宽2.29~2.49GHz,全向增益范围1.2~2.2dBic,能够实现良好的全向圆极化辐射。天线采用金属3D打印技术进行加工。实测结果与仿真结果吻合良好,实测轴比带宽2.27~2.47GHz,最大增益2.08dBic,水平面轴比小于3d B,适用于室内物联网等应用场景。

用于车载终端通信的双频段全向偶极子天线

针对露天矿山车载终端通信的需求,文章基于山字型结构设计一款同时满足4G/5G通信的全向偶极子天线。基于双锥天线模型设计全向印刷偶极子单频天线,通过在两侧加载枝节引入高频谐振,并通过在倒三角辐射贴片上开L形缝隙和矩形缝隙实现频段的展宽及谐振频点的偏移;对两侧枝节的末端进行渐变处理,使天线的谐振频率在拐点处可以平滑地过渡,从而在较宽的频带内获得良好的阻抗匹配。仿真和实测结果表明,该天线具备双频段全向的辐射特性,完全满足设计要求,且结构简单小巧、容易安装、不易受到损坏。

新型微带四面阵天线设计

在无线通信系统中,微带天线备受青睐。文章设计的微带四元阵在水平面上有全向的方向图,且极化方式为垂直极化。该天线的每个阵面都是采用串并结合的微带矩形贴片天线形式,并通过短路加载的方式实现天线俯仰面方向图在上半空间绝对增益大于-10.5dBi。测量结果显示,设计的天线在工作频率1090MHz时,电压驻波比小于1.5,方位面最小增益大于7dBi,前后比≥25dB。

具有五陷波的超宽带天线设计

设计了一款具有五陷波特性的小型化超宽带天线,通过改变陷波结构参数和分析天线表面的电流分布,研究了陷波结构对超宽带及陷波特性的影响。天线尺寸仅为25 mm×20 mm×1 mm。辐射贴片由矩形和圆形贴片组成,背板通过切角挖槽实现了超宽带特性;添加对称钩型枝节,蚀刻U型槽及3类U型槽产生5个陷波。天线的工作带宽在3.8~16 GHz。有效抑制了国际卫星波段(4.5~4.8 GHz)、WLAN下行波段(5.15~5.35 GHz)、UNII-2c(5.47~5.725 GHz)、WLAN上行波段(5.725~5.825 GHz)、下行卫星系统频段(7.25~7.75 GHz)、上行卫星系统频段(7.9~8.4 GHz)、国际电信联盟频段(8.01~8.50 GHz)的干扰。天线在工作频带内具有全向性,增益平均在4 dBi以上。仿真和实测结果基本吻合,表明该天线可用于超宽带通信系统。

一种宽带高增益全向天线的设计与实现

针对通信设备宽频带信号传输过程中,信号强度弱无法完成远距离传输、天线设备形式复杂、体积大等问题,本文提出了一种高增益印刷对称振子全向天线。天线两对辐射振子片分别位于印制板两面,通过带有匹配枝节的微带传输线馈电网络将两对辐射振子进行组阵。设计采用金属化过孔连接了电缆的内芯,将电缆金属外皮另一侧的辐射片焊接在一起,通过这种方式来对天线进行馈电。天线设备形式简单,体积小,既改善了天线的阻抗匹配,又有效的提高了天线增益,使得天线在宽频带内实现了全向辐射,相对带宽达到54.77%,且在带内增益大于3 dB,水平面方向图的不圆度小于2.2 dB。经过实际验证,该天线能够满足所设应用场景。

一种应用于5G皮基站的高隔离度全向天线系统的设计

提出并设计了一种工作在5G N41频段的高隔离度皮基站4×4 MIMO全向天线系统,该天线系统由1 mm厚度的铝基板、4个平面倒F天线单元和2个L形隔离单元组成,天线整体结构尺寸为180 mm×180 mm×10 mm。仿真研究表明,该4×4 MIMO天线阵列的4个单元天线,在主要工作频带内输入端回波损耗均小于-10 dB,单元天线之间的隔离度均大于25 dB,单元天线在水平面的增益大于1 dBi。该4×4 MIMO全向天线具有低剖面、高隔离度、结构简单易于加工集成等特点,具有良好的应用前景。

用于橡胶轮胎微波硫化的全向缝隙天线设计

为了实现橡胶轮胎内部的微波硫化,本论文设计了一种5.8 GHz全向圆波导缝隙天线,该天线平行于胎侧,放置于橡胶轮胎内部中心位置,并利用矩形波导TE 10-圆波导TM 01模式转换器实现所需微波模式的馈入。利用CST三维电磁仿真软件对其进行建模仿真优化分析,最终使天线反射系数在中心频点处小于-15 dB,水平方向不圆度小于1.4 dB,3 dB带宽达到59°,并且方向图具有良好的全向辐射特性,当输入功率为5 kW时,不发生击穿打火现象;模式转换器在中心频点处反射参数小于-15 dB,模式转换效率达到99%,能实现良好的模式转换。

Double-Sided Microstrip Circular Antenna Array for WLAN/WiMAX Applications

The design, fabrication, and characterization of the microstrip circular antenna arrays were presented. The proposed antennas were designed for single band at 2.45 GHz and dual bands at 3.3 - 3.6 and 5.0 - 6.0 GHz to support WLAN/WiMAX applications. The proposed single and dual band antennas showed omnidirectional radiation pattern with the gain values of 3.5 dBi at 2.45 GHz, 4.0 dBi at 3.45 GHz, and 3.3 dBi at 5.5 GHz. The dual band antenna array was placed on both top and bottom layers to obtain the desired antenna characteristics. The proposed double-sided dual band antenna provides omnidirectional radiation pattern with high gain.

Design of Ellipse Antenna Array for Cellular Phone Localization Systems

This paper describes our contribution in the ANR (Agence Nationale de la Recherche) project called GELOCOM (GEo-LOCalisation de telephOnes Mobiles) managed by the THALES Communications company, dedicated to the emergency localization of cellular phones. This contribution takes place in the field of antennas, with the development of broad-band systems: a circular array of six elements with separated outputs for the receiving part. In this paper, we present the design and the characterization of broad-band double ellipse array antenna. This special structure is chosen in order to obtain a good omnidirectional radiation pattern, enhance the gain and maximize the V/H polarization ratio. In comparison with the already existing antenna systems in the wireless market for similar purposes, the proposed antenna has considerably shown better performance which makes it competitive among other antenna models. For the design and optimization of antennas, we use CST MWS software. The antennas have been designed and successfully measured.

小型化多陷波新型超宽带天线设计与研究

提出了一种小型化新型多陷波超宽带(UWB)天线,陷波结构简单且紧凑,该天线体积仅为25 mm×18 mm×1 mm。天线由改进矩形辐射贴片和改进的半圆形接地板组成,天线的工作带宽为3.1~15.1 GHz。在辐射贴片上开U形窄缝隙和倒U形槽,实现了4.1~4.8 GHz频段和7.1~7.9 GHz频段的陷波特性,且在微带线上刻蚀U形窄缝隙,产生了5.4~5.9 GHz频段的陷波特性,通过优化测试表明,该天线能有效抑制INSAT波段(4.4~4.5 GHz)、国际卫星波段(4.5~4.8 GHz)波段、部分WLAN波段(5.725~5.825 GHz)以及X波段(7.25~7.75 GHz)多频段的窄带信号干扰。除陷波频段外,该天线具有良好的性能和全向辐射特性,适合应用于各类超宽带系统中。

一种低不圆度的垂直极化全向超宽带天线

文中提出一种可用于3G/LTE/5G室内通信的一种低不圆度的垂直极化全向超宽带天线,该天线由铜制单极子、加载金属片和金属地板构成。通过对铜制单极子馈电,天线实现垂直极化全向辐射。为了改善天线的阻抗匹配,减小天线的不圆度,单极子辐射体顶部增加了加载金属片。为了进一步扩展天线的阻抗带宽,金属地板上设置了一道环形槽。通过测试可得,在1.7~5 GHz范围内,该天线的相对阻抗带宽为104%()||S11<-14dB,不圆度小于1.5 dBi,可实现良好的室内移动通信。

基于超材料的低剖面高水平增益全向天线

设计了一款基于近零折射率超材料(NZRIM)的低剖面高水平面增益全向天线。超材料晶胞由两个对称的C形条带和一个弯折线条带组成。将超材料晶胞组成的阵列轴对称放置在全向天线的四周,有效改变电磁波的辐射方向,使之更靠近水平面,从而提高天线的水平面增益。测试结果表明,天线的-10 dB阻抗带宽为5.78 GHz~6.12 GHz。加载超材料后的天线在工作带宽内的水平增益可以提高0.5 dB~1 dB,最大水平增益达到2.68 dBi。

一种旁瓣匿影天线系统设计

旁瓣匿影是相控阵雷达采用的一种典型抗干扰技术。天线系统是旁瓣匿影的核心硬件设备,其设计直接关系到匿影波束能否有效压制干扰信号。针对目前旁瓣匿影容易出现的波束覆盖穿刺等问题,文中设计了一种旁瓣匿影天线系统,它包括全向匿影天线、低噪放耦合模块。通过匿影天线与低噪放集成设计提高匿影链路的干噪比。全向匿影天线采用方位全向双极化天线设计,水平极化匿影天线采用扁波导缝隙全向天线,垂直极化匿影天线采用扁平双锥全向天线。仿真结果表明,两种天线可实现方位向水平极化与垂直极化的全向覆盖。经实测验证,匿影波束能完整覆盖主天线副瓣区,可有效提升雷达系统的抗干扰能力。

一种宽带并馈全向天线的应用

提出一种中等增益宽带并馈全向天线,该天线包含2个背靠背印制在介质板两侧上的偶极子,以及2对与印制板垂直交叉的非对称寄生金属片。2个背靠背偶极子通过并馈方式组成阵列,增大了该天线的增益;两对非对称寄生金属片的引入,形成了等效的2个三维偶极天线子,提升了天线的全向辐射性能,改善了天线的不圆度。测试结果表明,该天线在800~2 100 MHz频段(89.7%)内电压驻波比小于2.5,增益大于3.5 dB,不圆度小于2.5 dB。

不平衡馈电的宽带全向偶极子天线设计

为了实现在多频段下的无线通信需求,设计了一种宽带偶极子天线。天线由介质基板上下表面的一对多边形覆铜贴片组成,通过2对形状不同的偶极子实现宽频带辐射。天线使用SMA接头直接馈电,为了减轻不平衡电流对天线辐射性能的影响,在天线上表面添加三角形结构,在下表面进行开槽,以调整表面电流的幅值与相位。实测结果表明,天线在1.3~2.5 GHz电压驻波比小于2,且方向图具有全向特性,实测结果与仿真结果具有较好的一致性。该宽带偶极子天线具有质量轻、剖面低的特点,为多频段无线通信提供了一种可能的结构。