机载天线隔离度仿真与分析

天线隔离度是机载电子系统实现电磁兼容预测的重要参数.根据反应积分原理,提出采用孤立天线远场方向图来替代实际环境中天线的办法,简化分析模型,在保证分析精度的基础上,提高计算效率,从而高效完成电大尺寸环境中天线隔离度的仿真分析.通过在自由空间情况下进行测试,验证了仿真结果的准确性.     

复杂环境中天线辐射方向图的分析

采用一致性几何绕射理论(UTD)研究了电大尺寸复杂平台中天线的辐射特性。以点源模型分析了天线受周围电磁环境影响后的辐射方向图,与自由空间方向图的对比说明了受影响后天线辐射特性的变化。与低频算法相比,本文算法有计算速度快、占用内存量很少的优点,可应用于工程中类似平台的多天线系统干扰分析。     

GTD分析阵列天线在复杂电磁环境下的近场受扰

给出了应用几何绕射理论(GTD)分析计算机载电大尺寸阵列天线方向图的一种方法,比较好地解决了在复杂电磁环境下,大型阵列天线近场受扰分析的问题.该方法将阵列天线的每个阵元看成电偶极子,由于电偶极子尺寸很小,因而可以认为阵列的近场区仍然是单个电偶极子的远场区.根据这样的远场近似,可以利用几何绕射理论用解析方法计算每个电偶极子受到遮挡影响的场分布.通过独立地对阵列天线的每个阵元单独寻迹计算,并且将所有阵元的场进行叠加,就可以得到整个阵列天线受到处于近场的障碍物遮挡影响的场分布.应用此方法计算了一个阵列天线受到近场遮挡之后的方向图,并与应用HFSS仿真软件计算的结果进行了比较.计算结果表明,这一方法可以很好地应用于复杂电磁环境中大型阵列天线的近场受扰问题分析.     

多层快速多极子技术分析微带天线

分析了电大尺寸的微带天线辐射方向图.从混合位积分方程出发,将空域格林函数写成多层快速多极子技术能够适用的形式,从而使得大尺寸的天线问题得以快速并精确地分析.文中还比较了不同迭代方法在分析时的效率.算例表明,灵活的一般最小余量法(FGMRES)的效率比其他方法高得多.     

Peano分形加载单极子辐射性能的研究

对有限地板尺寸和介质填充情况下Peano分形加载单极子天线的辐射特性进行了研究.利用HFSS分析了地板尺寸和填充介质材料对天线反射系数、辐射方向图和增益的影响.仿真表明:随着地板尺寸的减小,天线的阻抗带宽和增益明显减小,H面方向图变化不大,而E面方向图的半功率波束宽度增大,波束仰角减小;填充材料的介电常数过大会导致天线性能的恶化.在分析研究的基础上,设计并研制了地板尺寸为220mm×220mm的一阶和二阶Peano分形加载单极子天线.天线分别实现了45°和36°的波束仰角,50°和45°的半功率波束宽度.仿真与实测结果均表明凋节地板尺寸是控制Peano分形加载单极子天线E面半功率波束宽度和波束仰角的一种简单而有效的方法.     

W 波段电大尺寸椭圆柱形反射面天线的设计

设计了一种W波段电大尺寸波束扫描椭圆柱面反射面天线,利用椭圆双焦点的几何特性,通过合理设计口径面利用率及天线效率,使得天线在近场具有较窄的焦斑宽度,同时在远场也有较高的方向性,适用于中、远距离均要求较高横向距离分辨率的目标探测雷达。针对电大尺寸反射 面天线仿真工作量大的问题,提出一种简化设计方法,提高了天线设计效率。利用紧缩场（CR）测试方法对天线进行远场辐射方向图测量,通过雷达系统的目标探测实验测试了天线的近场焦斑宽度。实测数据与仿真结果之间的良好一致性证明了整个天线设计方法的可靠性和准确性。     

一种高频电大尺寸天线测试的新方法

文章提出一种简单可行的高频电大尺寸天线辐射测量新方法.该方法基于天线形面光学精密测量,将形面分为多个区域,每个区域带入实际光学测试采样点数据,采用电磁场数值计算得到天线的辐射方向图.光学测试系统提供了足够高的测试精度可以满足微波、毫米波甚至太赫兹等频段天线的测试要求.该方法还可以解决超大型可展开天线测试以及模拟星载环境实验条件下天线辐射测试难题.     

舰载多天线系统电磁兼容性分析

针对舰载多天线系统电磁兼容性(EMC)分析计算量大、耗时过长问题,提出了自动分层的多层快速多极子方法(MLFMA).采用BiCGStab(l)结合近场预条件方法进行求解,进一步提高了MLFMA的综合效率.为了分析天线间的近场耦合特性,运用微波网络理论结合互易定理给出了任意天线间的隔离度表达式.计算并分析了尺度与真实尺寸相当的某舰船模型上多根超短波天线的辐射方向图和天线间的隔离度.数值结果表明算法准确有效,并且对于电大运载平台中天线布局优化具有一定的指导意义.     

卫星导航接收机天线的简单化设计

用模式展开理论分析了卫星导航接收机常用的天线--矩形切角圆极化贴片天线的场结构、圆极化轴比和切角尺寸的关系,导出了该类型天线的内场分布、远场辐射方向图表达式,计算了圆极化轴比受切角尺寸的影响程度,并给出了归一化切角尺寸和圆极化轴比的关系曲线.L波段天线实例表明,理论计算结果和基于有限元法的HFSs软件仿真结果一致性较好,本文分析结果可用于导航接收机天线设计,简化设计过程.     

一种临近有限尺寸导电平板的圆极化天线的辐射

本文应用反应积分方程及统一几何绕射理论分析了临近有限尺寸导电平板的一种圆极化天线的辐射。首先用反应积分方程求得天线在临近无限大导电平板时的辐射,然后用统一几何绕射理论计算天线在有限尺寸导电平板边缘上产生的绕射,最后应用叠加原理求得天线合成方向图。应用这种方法可计算天线方向图、天线效率、天线电流分布及天线输入阻抗。对一种天线的实验结果与理论计算进行了比较,说明了这种分析是正确的。     

Annular slot windshield antenna

An automotive AM/FM hidden antenna using the slot between the body of the automobile and a metal solar heat-reduction film in the front windshield is described. Such solar heat-reduction metal films are becoming common and thus represent an opportunity to incorporate an antenna at only marginal cost. The radio frequency (RF) input impedance and gain patterns are described, and techniques for impedance matching are shown. Theoretical and experimental antenna patterns are compared. A test range measurement system and experimental results is described. A mobile on-road system to characterize the antenna in urban and suburban environments is shown. The application of this mobile system to the measurement of calibrated gain patterns is also demonstrated     

A back-to-back rectangular-patch antenna fed by a CPW

The configuration of a back-to-back rectangular-patch antenna fed by a coplanar waveguide (CPW) is proposed. The characteristics of the proposed antenna element were clarified by experiments. The radiation patterns and input impedances were measured as parameters of the widths of the rectangular patch and the substrate. Experimental results for an array antenna using the proposed back-to-back rectangular-patch antenna element are described. Good omnidirectional radiation patterns and input impedance characteristics were obtained. The proposed array antenna is suitable for microcellular, wireless LAN, and indoor radio systems     

Antenna patterns of nonsinusoidal waves with the time variation ofa Gaussian pulse

The development of antenna theory for nonsinusoidal electromagnetic waves has been based on the idealized rectangular pulse. In practice, an antenna that is designed to operate in the mode of an electric hertzian dipole would radiate a pulse that best approximates a Gaussian one when the driving current consists of a linear transient. The principle of radiation of nonsinusoidal electromagnetic waves with the time variation of Gaussian pulses is discussed. The properties of the Gaussian pulse are presented, i.e., the autocorrelation function, energy spectral density, and spectrum. Antenna patterns, such as peak-amplitude pattern, peak-power pattern, energy pattern, and slope pattern are derived for a Gaussian pulse received (or radiated) by a linear array antenna. Computer plots of the derived antenna patterns are presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for a rectangular pulse     

非赋形双偏置高性能椭圆波束天线

分析了非赋形双偏置天线产生椭圆波束的机理,将馈源的椭圆波束照射到轮廓线为椭圆形的付反射面上,通过双偏置天线的对称转换原理,主反射面产生椭圆波束.馈源波束由矩形口径的多模喇叭产生,它提供了等化的方向图.给出了馈源及天线的方向图计算公式.实验结果表明,实测方向图基本与理论计算一致.与其他类型的椭圆波束天线相比,本天线加工简单,同时天线效率也较高.     

Radiation Characteristics and Mutual Coupling of a Dual: Band Antenna Array Structure

In this paper, an antenna array structure consisting of a reflector plate and a number of printed dipole radiation elements is investigated. This antenna array implementation is suitable for the globally available 2.4 and 5?GHz ISM frequency band facilitating a variety of wireless applications. S-parameters and radiation characteristics are simulated and measured in details. The impact of the plane reflector on radiation patterns and the reflection coefficient are also investigated. Furthermore, mutual coupling effects between adjacent elements and the corresponding radiation patterns are studied for different antenna array configurations. Both simulated and measurement results are useful in antenna array design and antenna applications in wireless communications.     

Maximum directivity beam-former at 60 GHz with optical feeder

We present an optically controlled 60 GHz array antenna which may be used as a smart antenna in an envisaged broadband mobile communication system. The desired field patterns of the antenna were synthesized using the maximum directivity beam-forming algorithm which enables an optimum radio link to a selected mobile terminal to be created while the signals of other terminals are suppressed by the s of the antenna's field distribution. The 60 GHz signals were generated by optically heterodyning the signals of two laser diodes. The field distribution of the antenna was formed by a silica based photonic beam-forming network. The experimentally obtained data confirmed the calculated field patterns.     

Synthesis of antenna arrays with shaped-beam patterns

A method for the synthesis of the amplitude-phase distribution of an antenna array, which uses embedded element patterns, is developed. In the general case, the method ensures formation of an arbitrary shaped-beam pattern. Features of the synthesis of shaped-beam patterns of antenna arrays with elliptical polarization and vector patterns are considered. The numerical analysis of the synthesis method, which is performed for an array of rectangular waveguides with vector patterns, confirms the efficiency of the proposed approach.     

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.      

Compact Switched-Beam Antenna Employing a Four-Element Slot Antenna Array for Digital Home Applications

In this paper a compact switched-beam antenna is proposed. The antenna is composed of a four-element antenna array based on L-shaped quarter-wavelength slot antenna elements. Such an antenna element is a planar structure and presents a directional radiation pattern in the azimuth plane. Its maximum radiation direction is toward near the direction of the open end of the slot. As a result, the open ends of the four slot antennas are arranged toward $0, pi/2, pi$, and $3pi/2$ , respectively. The statuses of these antennas are controlled by some diodes. Consequently, by carefully controlling the diodes, an antenna with several switchable patterns can be achieved. To prove the concept, a 2.4–2.5 GHz switched-beam antenna for WLAN applications is designed and implemented. Its size is 52 mm in square. The antenna possesses eight directional patterns and many nearly omnidirectional patterns in the azimuth plane. The experiment results fully demonstrate the performance of the proposed design. The envelope correlations and the characteristics of the designed antenna are also discussed. Due to the compact size and low manufacture cost, such a design can be a promising solution for digital home applications to overcome multipath problems and increase the transmission data rate.      

Planar inverted F antenna loaded with high permittivity material

Enhanced gain of an inverted F antenna loaded with a very high permittivity substrate has been demonstrated. Measurements show that the size of the antenna can be reduced without sacrificing the antenna radiation efficiency. The gain-enhancement mechanism, bandwidth, and antenna radiation gain and patterns are presented and discussed