Dual band dielectric resonator antenna for wireless application

The proposed technique is an integration of a slot antenna and a dielectric resonator antenna (DRA). This is designed without compromising miniaturisation and efficiency. It is observed that the integration of slot and dielectric structure itself may be merged to achieve extremely wide bandwidth over which the antenna polarisation and radiation pattern are preserved. Here the effect of slot size on the radiation performance of the DRA is studied. The antenna structure is simulated using the CST software. The simulated results are presented and compared with the measured result. This DRA has a gain of 7.1 and 6.3?dBi at 5.7 and 8.1?GHz, respectively, its 10?dB return impedance bandwidth of nearly 4.5% and 5.5% at two resonating frequencies. A total of 98% efficiency has been achieved from the configuration. It is shown that the size of the slot can significantly affect the radiation properties of the DRA and there are good agreements between simulation and measured results.     

Ag圆锥天线阵列的太赫兹波受激辐射仿真研究

根据宽频带THz辐射天线的要求,设计了圆锥结构的微米量级金属Ag天线及其阵列。采用矩量法分析了天线电场积分方程的求解方法,并采用CST软件仿真了Ag圆锥天线阵列能辐射太赫兹波特性,理论分析和数值仿真结果表明,单根Ag微米圆锥天线能产生有效的宽带THz辐射,辐射增益可达22.7dBi。而其组成的纳米圆锥天线阵则可进一步改善辐射方向性,提高增益到42.5dBi。该结果将有助于指导太赫兹波辐射源的实验研究。     

Analysis of the Electromagnetic Absorption in a New Design of PIFA Antenna Using Metamaterials

This paper presents the design, simulation and fabrication of a miniaturized wearable dual-band antenna put on a rigid substrate and operable at 2.45/5.8 GHz for wireless local area network applications. The electrical and radiation characteristics of the developed antenna were obtained by means of the technical insertion of a slot to tune the operating frequencies. To study the impact of the electromagnetic radiation of the structure of the human body, it is necessary to minimize the back radiation towards the user. Therefore, in this work, a multi-band artificial magnetic conductor (AMC) was placed directly above a dual-band planar inverted F antenna to achieve a miniaturization with excellent radiation performance. The simulations were carried out using the computer simulation technology CST Microwave Studio (CST MWS). A good agreement was achieved between the simulation and experimental results. The comparison of the measurement findings indicates that, when the antenna was backed by the AMC plane, the gain improved from 1.84 to 3.8 dB, in the lower band, and from 2.4 to 4.1 dB in the upper band. The front-to-back ratio of the AMC backed PIFA antenna was also enhanced. Then, to ensure that the proposed AMC structure is harmless to the human body, this prototype was placed on three-layer human tissue cubic model. It was observed that, due to the inclusion of an AMC plane, the peak specific absorption rate (SAR) decreased to 1.45 and 1.1 W/kg at 2.45 and 5.8 GHz, respectively (a reduction of around 3.7 W/kg, compared with an antenna without (AMC).

     

Design of wideband dual-band dual-polarized dipole for base station antenna

This article put forward a novel dual-band dual-polarized magneto-electric dipole antenna excited by F-shaped strips. The proposed antenna achieved a common impedance bandwidth of 25.5% and 39.5% in the lower and the upper bands at both input ports, ranged from 0.75 GHz to 0.97 GHz and from 1.73 GHz to 2.59 GHz respectively. The antenna has good performance in isolation, which is more than ?32 dB between the two input ports, and the gain of the antenna is average 4.3 dB and 7.8 dB in the lower and upper bands. The antenna has a stable broadside radiation pattern with low cross polarization and low back lobe radiation over the operating band. Metallic side walls on the ground are added for better performance in gain and radiation pattern.     

可贴敷于人体的RFID 标签天线设计

设计了一款可贴敷于人体的超高频(UHF)射频识别(RFID)标签天线,该天线由矩形辐射单元、环形 馈电和匹配网络组成,其总体尺寸为54. 3 mm×40 mm×0. 8 mm。分析了人体不同部位、天线与人体间距以及天线自 身结构变化对天线辐射性能的影响。通过调节环形馈电和匹配网络尺寸可以实现天线与芯片之间的阻抗共轭匹 配。样品测试结果与仿真结果比较吻合,当标签天线贴敷在人体背部时,实际测量的最大读取距离可达4. 9 m。     

Design and development of a unit element microstrip antenna for aircraft collision avoidance system

Aircraft/traffic alert and collision avoidance system (ACAS/TCAS) is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between the aircraft. In the existing system, four monopole stub-elements are used as ACAS directional antenna and one blade type element is used as ACAS omnidirectional antenna. The existing ACAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties to identify the possible threats. In this paper, the focus is on the design and development of a unit element microstrip antenna which can be used for ACAS application and to overcome the possible limitations associated with the existing techniques. Two proposed antenna models are presented here, which are single feed and dual feed microstrip dual patch slotted antenna. These are designed and simulated in CST Microwave Studio tool. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good reflection coefficient, Voltage Standing Wave Ratio (VSWR), narrow beamwidth, perfect directional radiation pattern, high gain and directivity make this proposed antenna a good candidate for this application.     

不同参数超宽带反射面天线系统辐射特性

在超宽带反射面天线设计中,首要问题是馈电天线的方向图与反射器匹配。以往在频域上对反射面天线的研究发现,当馈源天线方向图给出约-11 dB的边缘照射时,反射面天线可实现其最佳性能。在参数化模拟了作为馈源的透射电子显微镜(TEM)喇叭天线方向图特性的基础上,根据反射面天线的频域设计准则,相应地加入合适的超宽带反射面天线,对其远场辐射特性进行模拟计算。为了获得尽可能大的远场辐射场,采用计算机仿真技术(CST)数值模拟软件,在0 GHz~1 GHz频率范围内模拟了以不同参数TEM喇叭天线作馈源的超宽带反射面天线的远场辐射特性,并在时域上对其结果进行分析。模拟结果表明,由于其相位中心的不确定性,作为馈源的TEM喇叭天线无法与反射面天线完全匹配,其沿着反射面天线主轴移动时产生的反射面口径场相位和幅度的变化影响着远场辐射场的变化,TEM喇叭天线的遮挡效应也不容忽视。     

Novel small-size directional antenna for UWB WBAN/WPAN applications

This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna far field radiation pattern. The different structural antenna parameters were optimized via extensive numerical simulations. Results show that for frequencies above 3.5 GHz, where the power front-to-back ratio of the directional antenna is greater than 10 dB, its impedance is nearly the same as in the free space. It is not the case neither for the omnidirectional slot antenna nor the monopole antenna next to the body. Between 3 and 6 GHz performance of the novel directional antenna, in terms of radiation efficiency and SAR values, is significantly improved compared to omnidirectional antenna designs.     

The Radiation Properties of a Novel Wire Antenna for the Security Fence Radar

The radiation properties of a novel wire antenna are investigated. The main part of this antenna is a sinusoidal wire undulator, which radiates by coupling electromagnetic energy from a Goubau line located near the antenna. Far-field patterns and S-parameters composed of three sets of antenna are measured. The measured patterns are compared with the calculated ones and the phase and attenuation constants of all the antennas are calculated. Frequency behavior and the dependency on the antenna dimensions of those wave parameters are investigated. Measured and calculated field patterns are also compared with the MoM patterns and some properties of the wave propagating along structure are explained by using MoM current distributions. It is shown that a broadside transversal radiation occurs in a narrow frequency band. The radiation intensity strongly depends on the coupling distance between the Goubau line and the sinusoidal undulator. This antenna is used as the basic element of the security fence radar antenna array working at 1.25 GHz in the L-band, which detects intruders approaching the fence. The performance of the antenna in the array is investigated and the near field distribution of the array is measured. The received signals caused by an intruder are given. The effects of rain and wind are also considered. The results suggests that the security fence radar introduced in this study can be used for the perimeter control of closed areas such as airports, malls, etc.      

Evolutionary optimization for pattern synthesis and reduction of mutual coupling of linear antenna arrays

Optimal design of antenna arrays to minimize the mutual coupling effects in the geometrical arrangements of the linear antenna array (LAA) and circular antenna array (CAA) is dealt with in this work. Two different cases are considered to reduce the effect of LAA and CAA: Case‐1 in which the current excitations of the antenna array are considered to get the optimal radiation pattern of two geometry called LAA and CAA and Case‐2 in which inter‐element spacing and current excitations are both optimized for LAA geometry. A cost function that involves the mutual coupling factor as an optimization factor is developed to reduce the side lobe level (SLL), which takes mutual coupling effects into consideration. Excitation values and inter‐elemental spacing are optimized using particle swarm optimization (PSO). In LAA, for 8‐, 12‐, 16‐element arrays, SLLs are reduced by ?15.52, ?16.71, and ?17.78 dB in Case‐1. For the same sets of element arrays, SLLs were reduced by ?17.35, ?19.71, and ?20.26 dB in Case‐2. In CAA, the current excitations of the antenna array are optimized. For 8‐, 12‐, and 16‐ element arrays, SLLs are reduced to ?7.405, ?10.52, and ?9.43 dB, respectively. The arrays coded with the help of MATLAB based computation and the results obtained by MATLAB are validated by using CST.     

一种新型星载小型化AIS天线设计与应用

基于传统的倒F型天线,设计了一种M构型的新型小型化星载自动识别系统(AIS)天线。该天线具有尺寸小、质量轻、便于星体安装等优点,天线外形尺寸仅为324 mm?60 mm?263.2 mm。采用CST MICROWAVE STUDIO电磁软件进行仿真设计,在球面近场进行实物单机测试和辐射模型星(Radiating Mockup,RM)测试。天线的仿真和实测结果一致性好,且天线方向图覆盖区域能够满足卫星AIS系统的应用需求,目前已在多颗小卫星上得到成功应用。     

人体附近天线的辐射特性

使用解析方法研究了无线人体局域网(WBAN)通信中穿戴式天线的辐射特性.将人体简化为有耗介质椭圆柱体,采用椭圆柱面波展开和阻抗边界条件(IBC),利用收、发天线的互易原理,推导了置于人体附近的短振子天线之方向性图和增益的解析表达式.计算了不同极化取向以及离人体不同间距对天线辐射特性的影响.经与软件仿真和实验测试结果对比...     

折合偶极子天线与金属的距离对天线性能的影响

通过Ansoft HFSS 9.0和Matlab软件分析有限尺寸金属片对折合偶极子天线性能的影响。采用矩形且与天线长度比约1.25的有限尺寸金属片,水平对称放置于天线一侧。天线采用结构简单、输入阻抗易于调试的折合偶极子天线。仿真结果表明,通过调整折合偶极子天线与金属片之间的距离可以调节天线的辐射方向,实现较高的增益和阻抗周期变化。此结果已在实际应用中得到验证并可为RFID便携式天线等设计提供参考。     

近场聚焦微带阵列天线研究

设计了一个近场聚焦(NFF[1] )环形微带阵列天线,环上的微带贴片单元均采用同轴线馈电,工作频 率为2. 45GHz。该天线通过控制相邻两个环之间的距离,使相邻两环上的微带单元到达焦点的距离相差一个波长来 实现聚焦,继而探讨了调节两圆环之间的距离和增加圆环数目对焦斑尺寸的影响。利用HFSS 和CST 等电磁仿真软 件对天线进行仿真,并做出实物进行测试,仿真和测试结果表明:环形微带阵列天线可以很好地实现聚焦,并且随着 两环之间距离的减小和圆环数目的增多,焦斑的尺寸越来越小,从而实现在微波热疗等领域的应用。     

Range distance requirements for large antenna measurements

The dependence of the radiation patterns and antenna gains on the measurement distance when both transmitting antenna and receiving antenna have the same order of large dimensions is discussed. The antenna under test is the transmitting antenna. The near-zone radiation patterns (Fresnel pattern) and the antenna gains of various kinds of circular aperture distributions vs the measurement distances are calculated for an arbitrary size of the receiving probe antenna. It is found both theoretically and experimentally that the near-zone measurement error of the radiation patterns introduced when the receiving antenna is of comparable or the same dimension as the transmitting antenna is smaller than the error introduced when the receiving antenna is very small. Thus, it is concluded that as a range criterion 2D²_a/λ is more appropriate than 2(D_a+D_b)² /λ for pattern measurements (D_a and D_b are linear dimensions of the transmitting and receiving antennas, and D_a⩾D_b is assumed). It is shown that the gain error for any aperture distribution obtained by using a large receiving probe antenna is greater at any range distance than the error obtained by using a small antenna such as a dipole     

新型可重构临近耦合偶极子天线阵

提出了一种可重构的临近耦合印刷偶极子天线阵。其通过控制每个振子的间距和振子偏移中心馈线的距离实现方向图的改变,提出的可重构天线阵,将形成不同方向图的偶极子天线阵嵌套排布,并通过pin管开关切换不同的偶极子辐射单元组,从而实现天线方向图的重构,改变天线的最大辐射方向。仿真结果表明在9.8 GHz的中心频点上,该天线可实现最大辐射方向在0°和40°上切换:波束指向为0°方向时,最大增益为12 dBi;为40°时,最大增益为8.7 dBi,两种工作状态下天线输入端s11均优于-30 dB,匹配良好。     

基于MOM的舰船通信天线的特性分析

以舰船通信天线为研究对象，应用网格模型分析法及矩量法（MOM）对其进行计算分析，给出了求解复杂天线问题的一般思路。基于Pocldington积分方程和Galerking法，采用分段正弦函数展开，计算得出此类天线的输入阻抗和辐射方向图，并与无限大导体平面上的天线进行了比较。计算结果反映出了船体对舰船天线本身的影响。     

基于非均匀特异媒质的赋形天线设计

在PCB板表面蚀刻不同尺寸的微带单元结构,构建非均匀特异媒质层,并将其放置在天线辐射单元前方,利用非均匀特异媒质层对电磁波不同的反射系数,实现对天线辐射波束的赋形。设计了由不同尺寸正方形贴片组成的非均匀特异媒质层,并放置于工作频率为5.8 GHz的矩形贴片天线前方。仿真和测试表明:该非均匀特异媒质层能够在基本保持贴片天线工作频点和回波损耗曲线不变条件下,通过调整与贴片天线距离,实现辐射波束由笔形波束向宽角波束和马鞍形波束的赋形转换。为赋形天线设计提供了一种有效的新方法。     

Analysis of a borehole radar in cross-hole mode

A theoretical approach to cross-hole radar measurements is presented. An approximate analytical form for the current distribution on an antenna in a borehole is derived, and the theoretical receiving signal of the borehole radar in the cross-hole measurement is calculated. Theory is compared in the time-domain with the measured borehole radar signal obtained in a salt deposit. The radiation pattern of a borehole radar excited by a pulse is discussed. The accuracy of tomographic analysis, which is often applied to cross-hole radar measurements, is strongly governed by this radiation pattern. It is found that, in practice, most borehole radars have a pattern of a λ/2 dipole antenna. However, the radiation pattern can be deformed by short pulse excitation, loading by the surrounding media, and coupling to the logging cable     

Performance study of a fractal UWB MIMO antenna for on-body WBAN applications

In this paper, a fractal ultrawideband multiple-input–multiple-output antenna is proposed and its characteristics are studied in free space as well as in the proximity of on-body wireless body area network scenario. The performance of the wideband antennas are affected strongly in the proximity of the human body. Koch fractal geometry is used at the outer edges of basic octagonal geometry in the design, which helps to achieve desired miniaturization, wideband and stable radiation pattern. The presented antenna has a compact size of 25 mm × 40 mm. In addition, the effect of body tissues on antenna characteristics is analyzed by a four layered (skin, fat, muscle and bone) human tissue model. The comparative analysis of S₂₁ is performed at a various body parts position such as abdomen, near forehead and chest with different antenna orientations.