Ultra-wideband horn antennas with a considerable difference in radiation pattern width in <Emphasis Type="Italic">E</Emphasis>- and <Emphasis Type="Italic">H</Emphasis>-planes

The paper presents results of theoretical and experimental investigation of ultra-wideband horn antennas with a rectangular aperture and input formed by a symmetric H-waveguide. The antennas show a considerable difference in their radiation pattern widths in the E-and H-planes, and good matching properties in a range of frequencies from 1 to 10 GHz. The required difference between radiation patterns of the antennas is attained by proper selection of horns’ geometry and application of a diverging dielectric lens in each horn. Optimal profiles of the horn antenna generatrix and of the dielectric lens placed inside are determined. Reliability of results of the theoretical analysis is confirmed by testing the designed prototypes of the ultra-wideband H-sectorial and E-sectorial horns.     

Gaussian mode analysis of Cassegrain antenna efficiency

Gaussian mode analysis is a convenient way to characterize long focal length systems, such as the Cassegrain antenna at the secondary focus. We use multimode Gaussian optics to derive several interesting results concerning the aperture efficiencies of Cassegrain antennas fed by corrugated conical horns. The highest efficiency is obtained when the antenna is illuminated by a wide-band, wide-angle horn which has its phase center at the secondary focus, or equivalently by a narrow-band diffraction limited horn with its phase-center located at a confocal tertiary focus. In both cases this corresponds to placing the horn aperture at a position where the incoming fields are frequency-independent and have limited spatial extent. We generalize these results to show that a true image of the aperture distribution can always be formed on the spherical cap in the aperture of any arbitrary scalar horn, by using a single refocusing tertiary lens or mirror. Since both the incoming fields and the horn aperture fields on this surface are frequency independent, it follows that the aperture efficiency is also independent of frequency with either of these arrangements. We suggest that devices for shaping the aperture illumination, such as shaped lenses or dual shaped subreflector systems, should, in general, be installed near an image of the telescope aperture distribution.     

Antennes embarquées à réflecteurs multisources

Three telecommunication satellite antennas, developed under the research and development programme of the European Space Agency, ESA, are described. The first one, operating around 1.6 GHz, is to equip advanced mobile communications satellites. It includes an 8 m unfurlable reflector and a system of multiple feeds. The influence of facets in the mesh reflector surface on the radiation patterns is discussed. The second one, for European coverage in the 10.7 to 11.7 GHz band, includes a 1.1 m offset reflector fed by 23 horns backed by a numerically machined waveguide distribution network. Performances of the antenna, with emphasis on the distribution network, are discussed. The third antenna, operating at 19 GHz, generates 0.25° low sidelobe spot beams to cover major European traffic centers. Its 4 m offset Cassegrain reflector is fed by a system of about a hundred horns. Each beam originates from a cluster of seven horns, some clusters, corresponding to closely adjacent beams, partially overlap. The design and performances of the antenna and its components are discussed in the paper.     

基于口面场方法的W波段高口面效率单脉冲卡塞格伦天线

本文提出来一种应用于直升机防撞雷达的高口面效率W波段单脉冲双反射面卡塞格伦天线。口面分析方法的提出解决了W波段反射面天线口面相位分布不均匀的缺陷,从而有效的提高了口面的利用效率。利用该方法,本文研究并制作了口径为135mm、焦距为40.5mm的W波段卡赛格伦天线,并且设计了由四个E面多缝隙电桥和四个四分之一波导波长延迟线级联构成的和差网络。经测试,该单脉冲天线在93GHz具有38.6dBi的和波束增益,相应的口面效率为54.7%;差波束的零深优于-22dB,副瓣电平小于-18dB。测试结果与基于口面分析方法的仿真结果吻合,从而证明了本文所研究天线可以应用于高口面效率的W波段单脉冲系统中。     

集成鳍线为脊的新型圆锥及方锥TEM喇叭及其在目标瞬态特性中的应用

发明了一种共面波导到鳍线的宽带过渡结,采用该结构方式馈电,研制了一种新型超宽带集成鳍线辐射器,把此种鳍线作为圆锥ＴＥＭ喇叭或者方锥ＴＥＭ喇叭的脊,成为超宽带鳍线加脊的ＴＥＭ喇叭,该种喇叭及其脊的形式均为国内外首创。     

Designing classical offset Cassegrain or Gregorian dual-reflector antennas from combinations of prescribed geometric parameters

This paper proposes a simple procedure for the design of classical offset Cassegrain or Gregorian dual-reflector antennas from combinations of prescribed geometric parameters. This procedure has already been applied to classical Cassegrain and Gregorian antennas, to classical displaced-axis Cassegrain and Gregorian antennas, and to classical offset Dragonian antennas. The antenna systems can be fully characterized by 21 parameters, of which only five need to be provided by the antenna designer, as the remaining 16 parameters can be derived in closed form using the procedure described here. In this paper, we assume that the main reflector has a circular aperture, while the subreflector has an elliptical aperture All the antenna geometries presented satisfy the Mizugutch condition (1976), which is the geometric-optics condition for zero cross-polarized radiation. This procedure is very close to the one used for offset Dragonian systems, but all the relevant information is repeated here for completeness.     

Application of rectangular and elliptical dielcore feed horns toelliptical reflector antennas

The pattern characteristics of elliptical reflector antennas are investigated when they are fed by rectangular and elliptical horns partially filled with a dielectric. The bandwidth characteristics of these dielcore horns are superior to those of their corrugated horn counterparts. Representative reflector patterns are computed to properly demonstrate the utility of these feeds for reflector antennas with elliptical apertures. This reflector antenna exhibits high efficiency and low cross polarization, and may be suitable for radar and satellite antenna applications. The antenna configuration may become useful in relatively small antennas where more than 10% cross-polar bandwidth is required. The efficient dielcore horns may also be used as feeds for elliptical nonshaped dual-reflector antennas     

A comparison among 1-, 3-, and 7-horn feeds for a 37-beam MBA

A very common multiple beam antenna (MBA) configuration consists of a collimating device illuminated by an array of feeds. The collimating device is usually a reflector or a lens. The feeds are usually horn antennas with a circular aperture. The reflector is usually offset-fed to eliminate aperture blockage; the lens is center fed. The antenna's feeds are excited to produce a finite number of beams, so as to provide contiguous coverage of the field of view. The designer is forced to minimize the angular spacing between adjacent beams in order to maximize the minimum gain over the antenna's field of view. On the other hand, the feed horn's aperture gain is maximized when the feed horn spacing and its aperture diameter are equal. This results in antenna efficiency of the order of 30% when a single feed horn is excited to produce a beam. When a cluster of 3 or 7 adjacent feed horns are excited to produce a single beam, antenna efficiency can be increased to 50%. When it is tolerable, several identical antenna apertures can be used to replace a single aperture configuration. In this case, each of M apertures produces approximately N/M beams of an MBA that produces N beams. Horns producing adjacent beams do not illuminate the same aperture. This permits the use of a much larger horn aperture for a given beam spacing. This results in reduced spillover, higher gain of each beam, and increased antenna efficiency of each aperture. This paper investigates the maximization of gain for several lens antennas. It shows that antenna gain is increased as its focal length is decreased. That is, a focal length-to-diameter ratio (F/D) less than 1 is preferred     

An offset reflector antenna with low sidelobes

The corrugated conical horn is considered to be an ideal feed for low sidelobe reflector antennas because of its unique characteristics. Analysis is carried out to show that low flare horns are preferred over high flare horns to give rise to low sidelobe performance for a given offset reflector antenna system.     

纵向槽和径向槽组合波纹喇叭馈源的优化设计

研究了纵向槽和径向槽组合的波纹喇叭馈源的优化设计方法.基于旋转体时域有限差分算法分析波纹喇叭的性能,结合协方差矩阵自适应进化策略,以天线口径效率为目标,优化设计了一款Ku频段波纹喇叭馈源,并加工和测试了馈源样机.计算与实测结果表明,在10.7~12.75 GHz频带内,该喇叭具有良好的阻抗匹配和辐射特性,应用于标准卡塞格仑天线时,天线口径效率优于78%,验证了这种优化设计方法的有效性.     

Designing classical Dragonian offset dual-reflector antennas fromcombinations of prescribed geometric parameters

This paper proposes a simple procedure for the design of classical offset-Dragonian dual-reflector antennas from combinations of prescribed geometric parameters. This procedure has already been applied to classical Cassegrain and Gregorian antennas, and to classical displaced-axis Cassegrain and Gregorian antennas. We provide a list of 20 parameters from which the antenna system is fully characterized, but only five of these parameters need to be provided by the antenna designer, as the remaining 15 parameters can be derived in closed-form using the procedure described. We consider that the main reflector (MR) has a circular aperture, while the subreflector (SR) has an elliptical aperture     

Wide-scan spherical-lens antennas for automotive radars

A new approach to wide scan-angle antennas at millimeter-wave frequencies is introduced with special focus on ease of manufacturing and reliability. The system is composed of planar feed antennas (tapered-slot antennas), which are positioned around a homogeneous spherical Teflon lens. Beam scanning can be achieved by switching between the antenna elements. The spherical-lens system is analyzed through a combined ray-optics/diffraction method. It is found that a maximum efficiency of 50%-55% can be achieved using Teflon, Rexolite, or quartz lenses. The efficiency includes taper, spillover, and reflection loss. Calculations also indicate that the maximum lens diameter is 30-40 λ₀, which results in a maximum directivity of 39.5-42 dB. Measurements done on a single-element feed and a 5-cm Teflon lens agree very well with theory and result in a 3-dB beamwidth of 5.5° and better than -20-dB sidelobe levels at 77 GHz. Absolute gain measurements show a system efficiency of 46%-48% (including dielectric loss). A 23- and 33-element antenna array with a scan angle of ±90° and a -3.5- and -6-dB crossover, respectively, in the far-field patterns was also demonstrated. The 23-element array resulted in virtually no gain loss over the entire 90° scan angle. This represents, to our knowledge, the first wide scan-angle antenna at millimeter-wave frequencies     

Comparison of G/T between dual-reflector and primary-focus antennas

Cassegrain operation of moderate-sized antennas at low frequencies often poses difficulties because of the large feed horn required. Primary-focus operation using a two-hybrid-mode feed horn is shown to give a G/T ratio close to that provided by classical Cassegrain operation using a single-hybrid-mode feed.     

双馈源偏置卡塞格伦天线研究

文章根据偏置卡塞格伦天线设计原理,通过双馈源、副反射面的正反面将两种不同结构的偏置卡塞格伦天线结合在一起,研究出一种双馈源-单副反射面-双主反射面的新型偏置卡塞格伦天线。该天线充分利用了偏置双反射面天线的扫描特性好、可避免遮挡效应等优点,在两个不同方向上产生双波束,实现双方向扫描,拓宽了卡塞格伦天线的应用领域。     

一种多功能反射面天线的设计

介绍了一种多功能反射面天线的设计方法,利用同一反射面实现跟踪和干扰的功能。跟踪采用副面为栅条形式的卡塞格伦天线,干扰采用前馈抛物面天线。2种天线正交极化,通过理论计算、仿真优化结合合理的结构设计,保证2种天线的电性能及相互之间的隔离度。     

A method for designing high-power offset Cassegrain antennas

Starting from the geometrical parameters of the feed and the desired gain of the Cassegrain antenna, a method to determine the design starting parameters for a high-power offset Cassegrain antennas is discussed. Then, by numerically solving the equations governing the antenna geometry, a set of design curves are obtained, with which the structure of the antenna can be determined by trading off the electrical and geometrical system requirements. The method presented can be applied to both high or low gain feeds for constructing a high power microwave electromagnetic environment, where complex electronic systems can be tested. For linearly polarized feeds with high gain, the structure parameters of antenna with zero cross polarization can be obtained, which is equal to the design results of Brown and Prata (see IEEE Trans. Antennas Propagat., vol.42, no.8, p.1145-53, 1994)     

Amplitude aperture-distribution control in displaced-axistwo-reflector antennas

A design method for improving the efficiency and reduction of sidelobes in displaced-axis two-reflector antennas is presented. The method is based on an analysis of the geometrical-optics field transformation in the displaced-axis two-reflector arrangement. The principal difference of the displaced-axis antenna from the Cassegrain/Gregory two-reflector antenna is pointed out. While decreasing the level of illumination of the subreflector edge in the Cassegrain/Gregory antenna leads to decreasing the sidelobe levels, and, respectively, the efficiency of the antenna system, in the displaced-axis antenna, decreasing the level of illumination of the subreflector leads to an increased level of sidelobes and an essentially nonuniform amplitude distribution in the aperture. The aperture-amplitude-distribution dependence of the illumination level of the subreflector edge in displaced-axis antennas is much stronger than in Cassegrain/Gregory antennas     

Scattering of Spherically and Hemispherically Stratified Lenses Fed by Any Real Source

An analytical method to compute the scattering of spherically and hemispherically stratified lens antennas is described. The expansion of any real source on spherical wave functions is detailed and validated by comparison to commercial software simulations and measurements at both 50 GHz and 77 GHz. A mode matching technique (MMT) based on spherical wave functions is first used to analyze the scattering by spherically stratified lens antennas. The far field patterns and directivity obtained are in excellent agreement with commercial software simulations and measurements for a six-shell Luneburg lens at 6 GHz. This MMT is then extended to hemispherically stratified lens antenna analysis. Its validation is also carried out by comparisons to both commercial software and measurements for a three-shell half Maxwell fish-eye lens fed by an open-ended waveguide at W-band. The expansion on spherical modes gives direct access to the field everywhere. To highlight the progressive focusing effect of inhomogeneous lens antennas, the electric field is mapped in terms of magnitude and phase in the neighborhood of the entire structure. One of the originalities of this work is the quantification of the reaction created by the scatterer on the feed. Narrowing the scatterer to a stratified lens does not affect the generality of the presented procedure. While providing controlled accuracy, the MMT tremendously reduces both computation time and memory load in comparison to commercial software.     

激光通信与成像卡塞格林形式收发光学天线结构初解

在激光通信和成像系统中,卡塞格林形式的光学天线不论作为激光信号收发装置还是光学成像装置,像差的存在必然会降低其信号强度和成像质量等性能。通过分析三级像差理论和光学天线微扰理论,依据天线增益因子与遮挡比之间的关系,提出一种方便快捷求解卡塞格林式光学天线结构的方法。此方法在考虑光学天线效率的同时,也可以满足光学系统设计的体积尺寸、像差的要求,在仅知道光学系统焦距、主次镜间距和遮挡比的情况下,可以快捷求出光学天线结构参数。不但给出了四类卡塞格林式光学天线的光学结构参数计算公式,并且结合实际使用对不同的适用场合进行说明及优缺点对比。通过四种典型光学天线的实例计算结果和最优结果比对,表明此方法是一种方便快捷精准求解卡塞格林式的光学天线结构的方法,在工程上具实际指导意义。     

基于球谐函数天线间相互影响快速分析方法

针对系统内多天线电磁兼容性难以快速分析和评估的问题, 基于球谐函数提出了一种天线间相互影响的准确快速分析方法.由电场积分方程出发, 将天线间耦合电流的计算变量引入至天线的辐射方向图上, 同时利用矢量系数球谐函数对天线方向图进行分解, 一方面解决了因天线姿态变化而产生的多次建模、目标剖分和数值计算问题, 另一方面也解决了标量系数球谐函数在分解天线方向图产生的奇异点问题.与电磁仿真软件FEKO的仿真结果相比, 该方法具有较强的准确性, 且分析时间大大缩短, 为多天线电磁兼容性的快速分析评估提供了技术支撑.