The Millimeter Wave Radiation of a Traveling Wave Sinusoidal Wire Antenna

In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas. Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ?<?0.4). It is shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated antennas (κ?<?0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.     

Effect of near field radiators on the radiation leakage through perforated shields

The electromagnetic coupling through an infinite conducting sheet perforated with a finite array of apertures excited by a metal radiator placed in its near field is investigated. The coupling is analyzed numerically by the method of moments (MoM) with an emphasis on understanding the effect of the interactions between the array of apertures and the metal radiator placed in its proximity. The radiation leakage through the array of apertures is found to be significant due to the proximity to the antenna, even if the apertures are electrically small. The effect of a number of other factors like antenna size, antenna type, aperture spacing, and aperture sizes on the extent of radiation leakage occurring due to coupling between the array of apertures and the radiator is also investigated. Numerical results confirm that plane wave theory underestimates the electromagnetic coupling through small apertures by antennas placed in their near field.     

耦合激励系数及对称振子阵列天线的有源方向图研究

为了深入探讨相控阵天线单元间的耦合对阵中单元方向图的影响,以阵列天线单元S参数为基础,给出了阵列天线单元的耦合激励系数计算公式,利用阵列天线单元间的耦合激励系数分析计算阵中单元的有源辐射方向图.同时利用矩量法分析由偶极子单元组成的阵列,并把阵列中每个单元的感应电流幅度和相位与耦合激励系数的幅度和相位进行比较,二者数据基本一致.矩量法计算的单元有源方向图与本文提出方法的计算结果吻合良好,验证了本文给出的阵列耦合激励系数及阵列天线阵中单元有源方向图计算方法的可靠性.     

A fast MoM calculation technique using sinusoidal basis and testing functions for a wire on a dielectric substrate and its application to meander loop and grid array antennas

The input impedance matrix element of the method of moments (MoM) for an arbitrarily shaped wire antenna printed on a dielectric material Z/sub m,n/ is formulated to be composed of three terms Z/sup /spl psi/s//sub m,n/, Z/sup /spl psi///sub m,n/, and /spl Delta/Z/sub m,n/ involving single-, double-, and triple-integral calculations, respectively. The MoM based on the Z/sub m,n/ formulated in this paper (new MoM) is applied to two antennas-a meander loop antenna and a grid array antenna-as well as a simple loop used as a reference antenna. The computation time to obtain the current distribution of each antenna by the new MoM technique is compared with the time required for the conventional MoM, which has an impedance matrix element composed of four terms, all involving triple-integral calculations. It is revealed that the new MoM drastically reduces the computation time: for example, by a factor of 937 for the grid array antenna. In addition, the radiation characteristics of these two antennas are discussed. It is found that a reduced-size meander loop (62% smaller than the simple loop reference) has a radiation pattern similar to the simple loop reference. It is also found that the grid array has an axial beam radiation pattern without side lobes in the principal planes.     

The Millimeter Wave Radiation of a Dielectric Leaky-Wave Antenna Coupled with a Diffraction Grating: Broad-Face Interaction

The millimeter wave radiation of a dielectric leaky-wave antenna (DLWA) coupled with a metallic diffraction grating with a sinusoidal height profile is experimentally investigated. The interaction between dielectric and grating is contactless and it is from the broad-face of the dielectric line. The measured field patterns are compared with the simulated HFSS patterns. Antenna parameters such as polarization, HPBW, cross-polarization and side lobe levels are measured. The effects of the geometrical parameters of the grating to the radiation are also investigated. Some results are compared with a DLWA which has another diffraction grating profile shape (rectangular). The investigated antenna can be used as a frequency scanning antenna in mm-wave radars because it has low cross and side lobe levels and narrow beam width.     

Analysis of a Wire Antenna in the Presence of Sphere

An integro-differential equation is formulated for the problem of a thin-wire antenna in the presence of a sphere, and this equation is solved by the method of moments. The analysis is valid for an arbitrarily oriented and positioned wire relative to the sphere which may be either a perfect conductor or may be any simple homogeneous material. Input admittance of the wire antenna near a conducting sphere is determined from computed wire current and is corroborated by measured values of admittance. Also presented are calculated radiation patterns for the antenna/sphere structure.     

高阶矩量法计算机身对雷达天线方向图影响

本文采用高阶矩量法计算了某型运输机上加装UHF 雷达天线的受扰后辐射方向图,对计算结果进行了分析,并 与普通的RWG 矩量法、多层快速多级子等算法所需计算资源进行了对比。计算所采用的计算平台为普通的台式工作站。 由于计算资源的限制,采用RWG 矩量法的商业软件无法在相同台式工作站上完成这一计算任务,多层快速多级子则容易 出现迭代不收敛的情况。     

Application of compound coupling slots in the design of shaped beamantenna patterns

The amount of phase control realizable by resonant compound slots for application in a standing wave array is investigated. It is shown that with a proper choice of excitation coefficients, shaped beam antenna patterns can be designed with the use of resonant compound coupling slots. A procedure for designing resonant compound coupling slots in the feed waveguide of a planar array is presented. With the use of this procedure a shaped beam antenna pattern has been realized by a planar array consisting of compound coupling slots in the end-fed configuration and conventional longitudinal radiating slots. Excellent agreement between theory and experiment is found for input VSWR and radiation patterns, thus demonstrating the utility of resonant compound coupling slots     

高隔离度的连续波雷达收发天线系统

连续波雷达在强杂波下低空目标探测方面较常规脉冲雷达具有显著的优势。由于连续波雷达是同时发射和接收, 提高连续波雷达收发天线隔离是实现低空远程探测的关键。文中采用减小收发天线的互耦法和吸收法,极大地提高了连 续波雷达波导缝隙平面阵列天线系统的隔离度,用试验验证了其设计的有效性,实测结果与仿真数据相吻合,隔离度大于100 dB,对连续波雷达收发天线隔离度的工程设计具有一定的参考作用。     

Phased array antenna calibration and pattern prediction usingmutual coupling measurements

A technique which utilized the inherent mutual coupling in an array to both calibrate and predict the radiation patterns of a phased-array antenna is investigated. The only restriction of the technique is that the ability to transmit and receive with pairs of the array elements is required. The theory associated with array mutual coupling and its relationship to both array calibration and array patterns is discussed. The design of a test bed phased-array antenna is covered. The mutual coupling technique (MCT) is used experimentally to calibrate the test array as well as to predict the array radiation patterns. It is shown that the results obtained by MCT are in good agreement with conventional far-field measurements     

An FDTD/MoM hybrid technique for modeling complex antennas in thepresence of heterogeneous grounds

Calculating the current distribution and radiation patterns for ground-penetrating radar antennas is a challenging problem because of the complex interaction between the antenna, the ground, and any buried scatterer. Typically, numerical techniques that are well suited for modeling the antennas themselves are not well suited for modeling the heterogeneous grounds, and visa versa. For example the finite-difference time-domain (FDTD) technique is well suited for modeling fields in heterogeneous media, whereas the method of moments (MoM) is well suited for modeling complex antennas in free space. This paper describes a hybrid technique, based upon the equivalence principle, for calculating an antenna's current distribution radiation pattern when the antenna is located near an air-ground interface. The original problem is decomposed into two coupled equivalent problems: one for the antenna geometry and the other for the ground geometry, with field information passing between them via a rapidly converging iterative procedure. The fields in each region may be modeled using numerical techniques best suited to them. Results for several test cases are presented, using FDTD to model the ground problem and MoM for the antenna problem, that demonstrate the accuracy of this hybrid technique     

自由空间导线天线辐射模式分析

采用分段正弦基矩量法计算线天线电流,借助分段正弦电流辐射场表达式,将各分段电流产生的辐射场进行线性叠加,进而获得天线总的辐射场。该辐射场利用球面波展开法进行展开,同时采用数值积分方法求取辐射场球面波展开式中各模式的系数值。以3种基本单元天线:偶极子天线、圆环天线以及螺旋天线为例,定量分析了3种基本单元天线的辐射模式,验证了这一方法的正确性。     

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.     

分形在天线雷达散射截面减缩中的应用

首次提出利用分形独特的填充性能实现天线雷达散射截面(RCS)减缩，同时，分形单元可以减缩单元间的耦合，提高阵列的性能。给出了分形天线与常规天线辐射、散射特性的对比，表明将分形的概念用于天线设计中，不仅可以减小互耦，提高天线阵列的辐射性能，而且也可以减小天线的雷达散射截面，对天线的隐身有一定的借鉴作用。     

一维液晶全息编码相控阵天线设计与实现

针对小型极化相控阵雷达精确信号目标探测应用背景,为降低传统T/R相控阵天馈系统设计及调试复杂度,满足低功耗、低损耗、低成本制造、轻薄等应用需求,提出了一种液晶全息编码相控阵天线.主体采用小型化全息辐射单元、慢波结构、平行板波导馈电系统构成的一维全息电控扫描相控阵天线,利用成熟液晶面板制造工艺,通过控制全息辐射单元下方液晶分子的偏转状态调节天线谐振频点,组成全息编码相控阵天线.天线结构通过仿真优化确定,并在实物加工和测量基础上通过全息优化算法及电压灰度控制降低由耦合作用引入的副瓣性能恶化度,用梯度递减的搜索算法结合适当的目标函数优化算法实现方向图的最优控制.实测结果表明,该天线的波束扫描角度达到±49°,经过算法优化后,波束指向角准确度改善3°,旁瓣抑制电平改善1.7 dB.     

单脉冲寻向天线和目标的一体化仿真及测角误差分析

本文通过矩量法及其高效数值方法（MLFMA）对近距离目标--单脉冲收发天线的电磁互作用进行一体化数值仿真,定量研究了单脉冲天线的近场角度测量特性.在该近场模型中,目标散射近场的幅、相分布和同轴探针激励的喇叭单脉冲天线的辐射场（对应远场和波束）、接收端响应（对应远场差波束）均采用全波数值模拟获得.首先,计算单脉冲天线的辐射场并将其作为对目标照射的激励条件;接着,计算目标散射近场的空间分布;并计算出单脉冲天线所接收到的目标散射场;最后,使用幅值法和相位法计算出单脉冲天线近场测角角度,并在此基础上对近距离测角误差进行研究.在导弹目标算例中,将天线--目标一体化建模和天线口径面上散射近场的幅、相分布计算结果用于近距离条件下单脉冲天线测角误差的研究,并通过频率、距离的变化对测角精度做了对比分析;发现目标近场散射幅、相分布的非均匀性,是导致单脉冲天线近距离角度测量产生较显著的测角误差的主要原因;而频率较低时,测角误差较小.文中给出了物理解释,并提出近距离测向时借助于较低频信号的校正以降低测角误差的建议.     

一种毫米波相控阵雷达的天线单元

毫米波相控阵天线兼具有毫米波的优点与相控阵多功能等优势,并以其特有的技术特点,非常适合于小型化平台 的集成应用。本文提出一种具有宽扫描角的毫米波天线单元。在单元设计优化时,利用HFSS对其互耦影响和扫描盲角 效应进行了充足的考虑。天线单元组阵后,阵列辐射特性的实测结果与理论设计值具有很好的一致性。证明其非常适合 于一维、二维毫米波相控阵天线的组阵使用。     

一种串馈的非规则天线阵

均匀规则阵列天线的副瓣电平较差,且波束宽度较宽,不太适合于一维高精度相控阵雷达系统.针对这些要求,提出了一种基于串联馈电网络结构的非规则天线阵列.该阵列采用串馈方式,结合带空腔的微波多层板技术,通过带状线缝隙耦合方式,避免了背向辐射,同时获得宽带特性.该阵列采用遗传算法对阵列进行优化,获得低于-18 dB的理论副瓣电平,同时相比均匀规则阵而言,波束宽度仅有0.2°的拓宽.对于20°的波束宽度而言,该波束宽度扩宽量可以忽略不计.该阵列的实测2:1驻波带宽为19.8%,方向图带宽为12.2%,在方向图带宽内,阵列的实测副瓣电平低于-16 dB,阵列的带内测试增益高于11.7 dBi,实测结果和理论设计相吻合,表明该天线阵列适用于一维相控阵天线.     

蘑菇型EBG微带天线电磁辐射特性分析

利用矩量法对探针馈电的蘑菇型EBG微带天线的电磁辐射特性进行了分析。首先建立了天线模型,采用细导线的带模型将馈电探针和EBG短路过孔等效为细带,并与EBG金属表面和微带贴片一样均采用平面三角面元剖分,RWG基函数作为电流展开函数,将线面连接问题转化为面面连接问题。然后给出了采用空域矩量法对天线辐射特性进行分析的全过程,并介绍了激励源的添加模型。最后对蘑菇型EBG微带天线的回路损耗、输入阻抗和方向图等特性进行了分析计算,相关结果与FEKO和文献吻合良好,验证了本文方法的正确性。     

Microstrip-Franklin Antenna

Phasing stubs are employed to achieve a cophase current distribution in microstrip rectangular patch arrays. This technique, originally proposed for resonant long wire antennas by Franklin, avoids spurious radiation from half-wavelength connecting transmission lines as used in conventional patch antenna arrays. A slot-radiator model is derived to describe the basic radiation mechanism of the resultant new type of antenna and experimental results for the slot radiation resistance are given. The design of a 13-element resonant array for 12 GHz is presented together with measured radiation patterns.