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。     

用PTD分析双弯曲反射面天线形变和穿孔的辐射特性

该文根据模型反射面天线的爆炸实验测试结果建立了反射面天线形变的数学模型,应用物理光学(P0)法和物理绕射(PTD)理论计钟：了一种赋形反射面天线形变后的辐射特性,同时还计算了反射面天线表面被爆炸破片穿孔后的辐射特性,结果表明,由于反射面的局部形变,直接导致辐射方向图的恶化,并且随着形变部分面积的增大,水平面的副瓣抬高很大,穿孔也会使水平面的副瓣抬高。     

超宽带馈源技术发展综述

反射面天线是最主要的高增益天线形式,在与无线电相关的各个领域具有广泛应用。随着科技的发展,对于超宽带(UWB)反射面天线的要求日益迫切。因此,作为反射面天线核心的馈源,如何在超宽的频带内具有良好的阻抗特性、恒定的辐射特性和稳定的相位中心,已成为当今天线技术的研究热点。给出了超宽带馈源的设计要点,总结了超宽带馈源的类型、特点和发展现状,并对超宽带馈源设计技术的未来提出了展望。     

基于介质波导混合模式的双频馈源喇叭天线

随着大型反射面天线技术的不断发展,天线系统对设备功能的多样化与一体化提出了更高的要求,馈源作为大型反射面天线的核心,其性能决定了反射面天线整体特性.文章基于介质波导混合模式提出了一种介质加载双频馈源喇叭天线,工作于X(7.25～7.75 GHz)/Ka(21～22 GHz)频段.利用特征值理论求解双层介质波导中电磁场表...     

多孔毁伤时赋形反射面天线辐射特性的研究

利用基于表面电流积分的物理光学法对赋形反射面天线的远场辐射特性进行了建模和分析，比较了反射面完好时的计算结果与测试值，取得了良好的一致。着重研究了天线反射面多孔毁伤后辐射方向图特性受毁伤孔数、孔径及其位置的影响。分析发现，只有当孔径大于一定的尺寸(约0．20个波长)时，天线增益和副瓣电平才会发生明显变化。同时，毁伤孔径越大、越靠近反射面中心则天线增益的下降及副瓣电平的提高越显著。     

采用换元物理光学法分析桁架式可展开反射面天线方向图

桁架式可展开反射面天线在未来的星载合成孔径雷达(SAR)中将有着广泛应用,然而目前对该类天线方向图的系统性理论分析还不够完善.该文根据桁架式天线反射面的特殊构型——空间三角形单元拓扑结构,提出了一种将物理光学法与换元法相结合来计算馈源数目任意、位置任意的桁架式天线方向图的方法,仅需反射面上的节点坐标即可求出天线方向图.对矩形喇叭线阵馈源激励下的口径大小为2.8 m×6 m 的桁架式可展开反射面天线方向图进行编程仿真,得到的主要参数计算值与实测值相吻合,通过与几何光学法仿真结果相比较,得出该文提出的算法更为精确有效.该文提出的算法建立了桁架式天线反射面结构与天线方向图的直接联系,实现了该类天线的机电一体化设计.     

偏馈FZP天线的远场辐射特性

利用物理光学法分析了偏馈FZP反射面天线的辐射特性，考察了喇叭馈源的最强辐射中心带来的影响，计算机模拟结果表明了该天线具有较好的辐射特性。     

反射面天线馈源的混合相位中心

本文基于场相关定理严格导出了轴对称反射面天线中馈源的混合相位中心表达式,证明了对于线极化和园极化馈源,馈源混合相位中心表达式是完全一致的.为反射面天线尤其是修正卡塞格伦天线的设计和调整提供了理论依据.     

天线辐射特性计算

介绍了某雷达双反射面天线工程设计，采用Ansoft HFFS对馈源辐射特性进行仿真，获得较精确的初级方向图计算模型，应用等效面电流法和等效抛物面原理，获得反射面天线的次级方向图特性。给出了方向图特性计算值与实测结果的比较。     

球面三反射面天线的计算机辅助设计

本文介绍一种采用球面作主反射面的三反射面天线系统。该天线采用双副反射面对主反射面的球面散焦特性进行矫正,双副反射面由计算机辅助设计生成,固定主反射面不动,转动馈源及副反射面,可实现在空间一定区域内的扫描。由于馈源及副反射面是偏置的,该天线具有理想的副瓣特性和较高的口径效率。此外,本文还探讨了一些先进的计算机软件技术在反射面天线的分析及设计中的应用。     

赋形反射面天线毁伤效应研究

利用物理光学法分析了赋形双弯曲反射面天线在冲击波形变效应和破片打洞效应影响下远区辐射场的变化。由测试结果建立了反射面形变的数学模型，推导出了远区辐射场的计算方法，并提出了反射面打洞的模型及其辐射场的计算方法。结果表明：形变的位置和大小对天线辐射方向图的影响是不同的，破洞的位置和大小对天线辐射方向图的影响也是不同的，文中给出了详细的对比结果。     

用FDTD和物理光学混合法分析毫米波抛物面天线

抛物面天线通常的分析方法是几何光学法和物理光学法,对于电大尺寸的抛物面天线这两种方法都可以得到较好的结果,对于电小尺寸馈源的抛物面天线,馈源方向图不仅取决于辐射器本身的辐射特性,其馈电结构对馈源方向图也有较大的影响,在此情况下,用上述方法得到的结果与实验结果之间有较大的误差.利用FDTD可以把整个馈电结构纳入计算域中,得到辐射器完整的近区场,由等效原理可求出抛物面上电流分布,从而用物理光学方法计算抛物面天线远区场.本文用这种混合方法分析计算了毫米波波导裂缝作为辐射器的抛物面天线,计算结果和测试结果相当吻合,证明了方法的有效性.     

均匀照射赋形反射面天线设计

为提高反射面天线的照射均匀性，利用波束赋形技术设计一款工作在15 GHz的高性能偏置反射面天线.该天线由一个非均匀有理B样条（non-uniform rational B-splines，NURBS）反射面和一个介质棒馈源组成，NURBS反射面通过物理光学法结合Nelder-Mead优化算法来赋形，从而获得理想的天线辐射场.仿真结果表明，赋形后的反射面天线相对旁瓣电平低于-20 dB，增益在-2.7°~2.7°的波束范围内超过20 dBi，且浮动不超过1 dB.该天线具有结构简单、旁瓣低、增益均匀的特点，在卫星通信等领域具有重要作用.     

Ka 波段EBG 天线阵列的仿真与分析

电磁带隙(EBG)天线是一种可以提高天线辐射口径及增益的新型天线,本文首先以FSS 结构作为EBG 反射面,角 锥喇叭作为辐射源,设计了一种可以工作在29.7-30.2GHz,最大增益为23dB 的EBG 天线;其次,研究了7 个喇叭构成六 边形阵列时的阵列特性;最后,将EBG 天线用作单反射面多波束天线的馈源研究了波束的覆盖特性,结果表明,当波束 大小为1.12°时,多波束天线的峰值增益为44.5dB,边缘交叠电平为40.4dB,载干比大于12dB。证明了这种EBG 天线 具有良好的工作性能,为将来小型化反射面多波束天线的设计提供了一种新的思路。     

Hybrid analysis of reflector antennas including higher order interactions and blockage effects

The analysis of a reflector antenna system consisting of a feeder, a sub-reflector, and a main-reflector in microwave frequency bands, where the electrical dimensions of the antenna become prohibitively large for the use of a rigorous numerical method, has been performed by high-frequency asymptotic techniques (HFATs). As a result, the radiation patterns and input impedances of the antenna system were calculated based on an approximation: the radiation characteristics of the feed, sub-reflector and main-reflector are independent from each other. In this study, as an effort to alleviate the inaccuracy due to the exclusion of higher order mutual interactions existing among those subsystems, three different hybrid methods [finite-element method/method of moment (FEM/MOM) + physical optics (PO), FEM/MOM + geometrical theory of diffraction (GTD), and FEM/MOM + PO + physical theory of diffraction (PTD)] are introduced in the context of an iterative algorithm. The interactions between the feed and sub-reflector are accounted by a hybrid method which combines the FEM with the MOM; FEM/MOM. Whereas, the interactions between the objects in the FEM/MOM domain and the main-reflector are taken into account through the iteration: the fields and currents in the FEM/MOM domain are updated using the fields and currents obtained from the HFAT domain and vise-versa. These three methods are applied to two-dimensional reflector configurations, and corresponding results are compared in terms of accuracy and efficiency. The accuracy of the hybrid methods, especially those of FEM/MOM + GTD and FEM/MOM + PO + PTD, is found to be comparable to that of a rigorous numerical method. Furthermore, their computational costs are almost independent to the size of the main-reflector and to the distance from the feed point to the main-reflector.     

Classical axis-displaced dual-reflector antennas for omnidirectional coverage

The aim of this work is to discuss the synthesis and performance of classical dual-reflector antennas suited for an omnidirectional coverage. The reflector arrangements are axially symmetric with surfaces of revolution generated by axis-displaced conic sections, established from geometrical-optics (GO) standpoints to achieve omnidirectional radiation characteristics. Closed-form equations are derived for the design of all possible reflector configurations. The vector GO aperture field is also obtained, yielding an approximate analysis by the aperture method. Some pertinent geometrical characteristics and efficiency curves are then presented and discussed for several antenna configurations fed by transverse electromagnetic coaxial horns (for vertical polarization). A practical antenna design is conducted and analyzed by the method-of-moments technique, demonstrating the accuracy of the efficiency analysis yield by the aperture method for moderately large antenna apertures.     

Numerical analysis of small parabolic antennas using the method of current and change integral equations

The method of current and charge integral equations [1] is applied to numerical electrodynamic analysis of radiation and impedance matching characteristics of parabolic antennas with reflector diameter from 0.5 to 10λ. As a result as opposed to the current method relying on physical optics approximation the influence of feed on reflector’s radiation pattern, the influence of reflector on feed’s impedance matching and the contribution of feed’s rear radiation into reflector’s radiation pattern are all accounted for. A new model of representing a parabolic surface in the form of its square approximation is suggested, which provides almost uniform partitioning grid and has at least 2.5 times less boundary elements that the common revolution surface representation while having the same sampling coefficient. Dependences of antenna’s directivity on reflector dimensions (0.5–10λ) are calculated for six different focus distance to reflector’s diameter ratios using the developed by the authors crystal_U software package. The calculated results are confirmed by good matching with well-known experimental results.     

On the characterization of a reflector impulse radiating antenna (IRA): full-wave analysis and measured results

There is a growing demand for impulse radiating antennas (IRAs) to receive and transmit short pulses. The basic concepts of IRA are reviewed and the far-field pattern versus frequency of an ideal IRA is characterized based on the fundamental properties of IRA. It is shown that the transmitted pulse is ideally in the form of a time derivative of the input pulse. The physical optics simulation results show that the far-field characteristics of a parabolic reflector are very close to an ideal IRA if it is fed properly. The reflector IRA was constructed, analyzed and measured at UCLA. The near-field and far-field characteristics of the reflector IRA are studied using both the method of moments (MoM) full-wave simulations and the frequency domain measurements. In this paper, the radiation mechanism of the reflector IRA is studied using a detailed current distribution on the parabolic reflector and the feeding structure at different frequencies. Applying either the calculated current distribution on the reflector IRA or the measured near-field results, it is seen that the aperture field intensity of the parabolic reflector is not the same in the two principle planes and as a result the beam-widths in the two principle planes are different. The far-field patterns of the antenna are measured and the calculated far-field patterns support the measured results. The calculated current distribution results provide a guideline on how to properly change the feeding structure to achieve a more uniform aperture field and increase the antenna radiation efficiency.