双极变张角时域天线设计

传统的超宽带天线概念是在频域下定义的,有些不能作为时域脉冲天线使用。为实现时域天线的定向性、低剖面、小尺寸、可承受高功率等性能,结合领结天线的低剖面特性和TEM喇叭天线的定向辐射特性设计双极变张角时域天线,该天线是根据光导开关的时域响应设计天线激励源的低剖面定向时域超宽带天线,仿真结果表明．该天线是一种高性能的时域天线。     

一种超宽带高增益的透镜喇叭天线的设计

该文提出了一种适用于微波通讯系统的超宽带(UWB)高增益透镜喇叭天线。该天线由一个E面喇叭天线,一个球面介质透镜和双楔形金属脊构成,并由同轴线馈电及采用HFSS软件仿真。仿真结果表明,双楔形金属脊可有效增加喇叭天线的带宽,有效频率带宽达到2～12 GHz。当仅使用双金属脊来改善喇叭天线的性能时,喇叭天线的增益会下降。文中使用一种球面介质透镜来补偿双金属脊对喇叭天线增益的负面影响。仿真结果表明,该透镜可有效提高喇叭天线在工作频带内的增益。采用透镜和金属脊结构后,该喇叭天线拥有超宽带,高增益和较强的定向辐射性能,可以应用于各类通信系统中。     

E-plane analysis of a modified horn antenna withsuppressed far-out sidelobe level

It is shown that the far-out sidelobes of a horn antenna can be suppressed by curving the edges in the aperture. A three-dimensional uniform geometrical theory of diffraction (UTD) analysis of the E -plane radiation pattern of the modified horn antenna was performed and compared with straight edges. This analysis indicates that the curvature of the edges does indeed influence the sidelobes to the effect that the modified horn antenna has significantly lower far-out sidelobes. The radiation patterns for modified horns were measured and compared with the calculated patterns and were found to be in good agreement     

Millimeter-wave integrated-horn antenna. II. Experiment

For pt.I see ibid., vol.39, no.11, p.1575-81 (1991). The impedance and radiation patterns of a dipole-fed horn antenna in a ground plane are experimentally investigated at microwave and millimeter-wave frequencies. The agreement with the full-wave analysis technique presented in part I is good. The results indicate that for a 70° flare-angle horn, horn apertures from 1.0 λ-square to 1.5 λ-square with dipole positions between 0.36 and 0.55 λ yield good radiation patterns with a gain of 10-13 dB a cross-polarization level lower than -20 dB, and resonant dipole impedances between 40 Ω and 120 Ω. It is also found that the impedance measurements can be safely used for 2-D horn arrays, but the radiation patterns differ because of the Floquet modes associated with the array environment. The integrated horn antenna is a high-efficiency antenna suitable for applications in millimeter-wave imaging systems, remote-sensing, and radioastronomy     

Radiation pattern synthesis for circular aperture horn antennas

A set of radiation pattern functions, suitable for synthesis of radiation patterns from circular aperture horn antennas, is obtained by assuming an aperture distribution consisting of the fields of cylindrical waveguide modes. A technique is presented for using a linear combination of the radiation pattern functions to approximate a desired radiation pattern. Linear combinations of the radiation pattern functions resulting in maximum secondary gain, when used to illuminate a paraboloidal antenna, are obtained empirically. Using spherical wave theory, maximum performance theoretically obtainable from an antenna is derived as a function of the aperture size of the feed system; the feed efficiency resulting from these theoretical limits on performance is compared to the feed efficiency of patterns obtainable from circular aperture horn antennas, and to experimental results of attempts to realize optimum circular aperture horn patterns.     

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。     

Linear array of woodpile EBG sectoral horn antennas

A technique is described for creating linear array antennas that conform to the natural stacking sequence of the woodpile electromagnetic bandgap (EBG) material. Each element in the linear array consists of a woodpile EBG sectoral horn antenna. The electromagnetic confinement mechanism within each horn antenna relies wholly on the 3-D EBG of the woodpile material. The array element has a typical sectoral horn pattern with a directional beam in one principal plane and a broader beam in the other. The bandwidth of the sectoral horn is almost equal to that of the defect EBG waveguide. Measured and theoretical results for radiation patterns, impedance bandwidth and gain of a sectoral horn antenna made from alumina are described, and theoretical results for a design made from silicon are presented. It is shown that the layer-by-layer nature of the woodpile EBG material enables sectoral horn antennas to be easily stacked together in the E-plane to create linear arrays. Analysis of the mutual coupling as a function of element separation and its effect on reflection coefficient are presented for a two-element linear array in silicon. Theoretical analyses for fixed and scanned beam linear arrays of silicon woodpile EBG sectoral horns are described and finite-difference time-domain results are compared with array theory. The fixed beam arrays are designed for high directivity while the scanned beam array enables wide angle beam steering through the use of parasitic array elements.     

Finite-difference time-domain method for antenna radiation

The finite-difference time-domain (FDTD) method is used to model and predict the radiation patterns of wire and aperture antennas of three basic configurations. A critical step in each is the modeling of the feed. Alternate suggestions are made and some are implemented. The first antenna is a quarter-wavelength monopole and the second is a waveguide aperture antenna. In both bases the antenna is mounted on ground planes, either perfectly conducting or of composite material. The results obtained using the FDTD technique are compared with results obtained using the geometrical theory of diffraction (GTD) and measurements. The third configuration of interest is a pyramidal horn antenna. To model the flared parts of the horn, a staircase approximation was applied to the antenna surface. The computed radiation patterns compared well with measurements     

Wide-band circular groove guide horn antenna

A novel horn antenna based on a circular groove guide is analyzed and measured at Ku-band and Ka-band, respectively. This horn antenna can cover a frequency range from 14 to 40 GHz. Its optimum dimension was obtained according to the maximum directivity. The antenna can be matched efficiently to free space through its large aperture. Moreover, its input VSWR is low. The theoretical radiation patterns are close to the measured ones.     

Plasma simulation with an artificial dielectric in a horn geometry

The simulation of a plasma sheath using an artificial dielectric is studied in this investigation and is applied to an antenna geometry which is similar to some configurations encountered in aerospace applications. The antenna configuration is equivalent to a horn in an infinite ground plane with an unbounded plasma layer in front of the horn. The plasma layer is simulated by a rodded medium, and the radiation patterns of the antenna system are studied experimentally at 9, 10, and 11 Gc/s. Two constructions of rodded media are utilized in the pattern measurements. The experimentally determined radiation patterns have a secondary maximum associated with the properties of the plasma sheath. More energy is radiated in the OFF-axis region when the plasma sheath is present.     

Ultra-wide band corrugated gaussian profiled horn antenna design

Nowadays, an increasing number of applications need stable radiation patterns with low sidelobes and low crosspolar levels in a very wide bandwidth. Gaussian profiled horn antennas (GPRAs) have demonstrated their feasibility as one of the best solutions. A corrugated Gaussian horn antenna design with more than 40% bandwidth is proposed. The measured radiated far field patterns are in good agreement with the simulated ones. The measured results show a Gaussian antenna with extremely wide bandwidth, low sidelobes, and low crosspolar levels     

Radiation patterns of metal and dielectric wall diagonal horn antennas

The radiation patterns and gain of dielectric wall diagonal horn antennas of various thicknesses (0.15cm and 0.32 cm) and dielectric constants (? = 2.54, 2.56 and 3.03) have been experimentally studied and compared with a metal diagonal horn antenna having the same aperture at 9.418 GHz. Radiation patterns of these dielectric horn antennas when used as square horns are also presented and compared with a similar metal horn. The use and applicability of dielectric horn antennas is discussed.     

The corrugated horn as an antenna range standard

The corrugated horn discussed here is a valuable tool for use in microwave pattern ranges. It has the properties of concentrated energy in the main beam, low backlobes, high efficiency and almost monotonic amplitude, and phase radiation patterns which make the corrugated horn useful for a source antenna in a pattern range and also as a possible standard antenna for calibration purposes. A sample of the references that have dealt with the corrugated horn is given for the benefit of the reader [1]-[7].     

Analysis of rectangular horn antennas via uniform asymptotic theory

Approximate analytic expressions for the far-field radiation pattern and modal reflection coefficient of the three-dimensional horn antenna have been developed. Based upon a multiple-image model of the two-dimensional horn-waveguide structure, this approach offers greater generality than previously proposed ray analyses with comparable complexity and accuracy. The uniform asymptotic theory (UAT), which is employed throughout, provides information when this approach is valid for a desired degree of accuracy in the solution. It is demonstrated that, in most cases, the far-field pattern of the horn is reducible to the pattern of a simple slit in an absorbing screen illuminated by an array of patterned line sources. The measured patterns of several horns are convincingly recovered by the prediction of the analytical model. The same model is used to calculate the modal reflection coefficient of the horn-waveguide structure and, again, comparison with measured results is excellent.     

Computer-aided radome analysis

A procedure is presented for predicting by computer the radiation pattern of an antenna in the presence of a radome. The case of a horn antenna radiating through an actual aircraft radome is treated in detail, and a comparison is made between computed and measured antenna patterns. Good agreement between theory and experiment is noted.     

一种高功率多模喇叭天线

为满足高功率微波系统对天线的需求,设计了一种覆盖15.9~21.8 GHz频带的多模喇叭天线,并研究了其高功率性能。仿真计算表明,该喇叭天线在频带内驻波＜1.2,并具有良好的辐射特性。在16.3~20.8 GHz满足E面和H面方向图在20 dB范围内等化度良好,且喇叭输出功率达526 MW时不会出现击穿现象。     

基于阻抗超表面的高效率角锥喇叭馈源

研究了一种基于阻抗超表面的高效率角锥喇叭馈源.将阻抗超表面放置于金属角锥喇叭内壁, 获得了一种性能良好的新形式高效率馈源.首先分析了超表面对表面阻抗特性的调控作用, 并证明该超表面对TE波和TM波呈现不同的阻抗特性.在特定的阻抗条件下, 该喇叭内壁可以支持平衡混合模式, 从而获得旋转对称的辐射波束.然后设计和加工了Ku频段的超表面高效率馈源, 馈源的测试方向图表明其辐射性能优良.最后将该馈源照射一款1.25 m Ku频段环焦天线, 测试其辐射方向图, 同样显示出其优异性能.与该环焦天线原有的波纹喇叭馈源相比, 超表面高效率馈源的性能与波纹喇叭馈源相当, 同时在体积、重量和成本方面具有明显优势.     

Comprehensive analysis for E-plane of horn antennas by edge diffraction theory

Edge diffraction theory is used in analyzing the radiation characteristics of typical horn antennas. The far-sidelobe and backlobe radiation has been solved without employing field equivalence principles which are impractical in the problem. A corner reflector with a magnetic line source located at the vertex is proposed as a model for the principalE-plane radiation of horn antennas. A complete pattern, including multiple interactions and images of induced line sources, is obtained in infinite series form. Diffraction mechanisms are used for appropriate approximations in the computations. The computed patterns are in excellent agreement with measured patterns of typical horn antennas. Radiation intensity of the backlobe relative to mainlobe intensity is obtained as a back-to-front ratio and plotted as a function of antenna dimensions.     

A study of radiation from circular groove guide horn

A novel horn antenna for millimeter waves based on circular groove guide is presented and investigated in this paper. Its radiation patterns are calculated by employing the aperture field method. The patterns obtained by experiment show agreement with calculated results.     

Biconical antennas and conical horns with elliptic cross section

The mode-matching technique is applied to the problem of radiation from a conical antenna with elliptic cross section including the degeneration to a sector antenna. In the `guiding region' of the antenna the transverse electromagnetic wave is considered as well as higher-order waves which are described by products of Lame functions which satisfy the boundary conditions. In the exterior region, the field is expanded into products of Lame polynomials. Antenna input impedances and far-field patterns are shown as results. In addition to computing the far-field patterns of a conical horn with elliptic cross section by the aperture field method, the authors analyze the radiation field by a multipole expansion to the mode-matching technique