High efficiency and low sidelobe design for a large aperture offset reflector antenna

A design method giving high efficiency and low sidelobes is discussed for large aperture offset reflector antennas. A new reflector shaping technique using the subreflector and the beam waveguide reflector with the parabolic main reflector is proposed to simplify the main reflector manufacturing process. The effectiveness of the technique is confirmed by the model experiments. One problem with this reflector shaping technique is that the subreflector edge level cannot be controlled independently of the main reflector edge level. By investigating the relation between the gain reduction and the subreflector edge level, which affects the wide-angle sidelobe levels, the realizable characteristics of antennas are studied. In order to decrease the subreflector edge level without reducing the aperture efficiency, a technique using an extended reflector is also proposed. Its effectiveness is shown by theoretical and experimental investigations.     

Module sharing design technique for dual reflector antenna

Module sharing technique for a dual reflector antenna is presented, which makes different apertured main reflectors of the same focus sharing one set of module by means of optimizing the subreflector. To optimize the subreflector, a fast convergence optimization method is given with a satisfactory result.     

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.     

Ku band electric models for large deployable mesh reflector antenna

Two scaled mesh reflector electric models have been constructed for the design of a 30 m diameter large deployable antenna. Radiation characteristics of the antennas have been measured and compared with calculated results. The similarities between measured and calculated results are very close. The cross-polarisation level especially is considerably low.<>     

An offset bifocal reflector antenna design for wide-angle beam scanning

A synthesis procedure and performance results for an offset dual reflector with perfect focusing atpm 8degof beam scan are presented. This bifocal antenna extends the theory of the previously reported symmetric system to an offset design. Approximations, such as the smearing of focal points into a "focal ring," are eliminated, as is blockage. The offset design affords greater design flexibility, although the synthesis is more complex. Computed and experimental results demonstrate the improved beam-scanning performance of this antenna.     

一种折叠反射面天线的结构设计

针对机动雷达反射面天线结构尺寸运输超限问题,介绍了在结构设计过程中依据载荷分析计算结果,应用三维建模技术,虚拟装配技术,优化结构布局,完成自动展开/折叠反射面天线的结构设计。该天线在工作状态展开,在运输状态收缩到规定运输界限范围内,满足了雷达机动要求。     

Calculated scan characteristics of a large spherical reflector antenna

A previously published numerical method to calculate the radiation properties of parabolic reflectors has been modified to also include very large spherical reflectors. The method has been verified by comparing the calculated and the measured results for a 120-wavelength spherical reflector.     

宽角扫描赋形对称单反射面天线的优化设计

为满足宽角扫描的要求,基于几何光学理论对一种对称单反射面天线进行了赋形设计。以扫描口径面上射线路径的方差为目标函数,采用Powell方法极小化该函数,最终确定出了反射面的方程、特定扫描角度下的馈源位置以及馈源对反射面的照射区域,实现了天线扫描工作时的最小增益损失和最高口径利用效率。分析结果表明,所设计的单反射面天线在宽角扫描范围内,方向图无大的畸变,增益损失很小,副瓣电平达到了设计要求。本文赋形方法为宽角扫描双反射面天线的赋形设计奠定了基础。     

大型反射面天线轨道不平度对指向精确度的影响

针对奇台110 m口径射电望远镜高指向精确度特点,在现有天线指向模型的基础上,推导了轨道误差源(轨道不平度)对指向精确度影响的关系模型。基于功率谱函数傅里叶级数系数归并法,建立了天线轨道不平度数学模型。针对国外某完全焊接式50 m天线,轨道水平度测量数据,通过实验数值仿真,采用查表法补偿轨道不平度造成的天线指向误差,使俯仰角误差精确度提高了1.5″,对高指向精确度天线实现的研究提供了有力支持。     

Analysis of active surface reflector antenna for a large millimeterwave radio telescope

The authors analyze the effects of imperfect segment alignment on the aperture efficiency of a large millimeter telescope. A 50 meter diameter instrument of this type specified to operate to wavelengths as short as 1 mm is being designed with an actively controlled main surface. By simulating the performance of the control system, they generate samples of tilt and piston errors for the segments from which the antenna radiation patterns and aperture efficiencies are calculated. They make a comparison of these results with models of antenna tolerance theory developed by Ruze (1966), which relate the aperture efficiency to the RMS phase error. They find that Ruze's formulas have a different range of validity when the aperture RMS phase error, rather than the RMS surface error, is used as a parameter. When appreciable tilt errors are present in large segmented antennas, the aperture RMS phase error tends to a constant value, independent of the aperture illumination and of the shape of the segments. They conclude that the antenna RMS surface error is a better tracer of the aperture efficiency than is the aperture RMS phase error when Ruze's formula is used. They find that this well-known expression stands as a lower limit to the performance of large segmented reflector antennas     

An array-compensated spherical reflector antenna for a very large number of scanned beams

There are many stringent demands imposed on the applications of spaceborne antenna systems. One of the most challenging demands is the generation of multiple beams with the ability to scan a very large number of beamwidths. Since the parabolic reflectors have limitations in this application, a 35-m spherical reflector antenna is proposed for a geostationary radar antenna at Ka-band (35.6 GHz) due to its inherent capability of scanning the beams to very large number of beamwidths. The utility of using planar array feeds for correcting spherical phase aberrations is investigated to overcome the performance degradation effects. Two different methodologies are developed for the array excitation coefficients determination based on phase conjugate matching and the results are compared. Using the compensating feed array, the radiation characteristics of the compensated spherical reflector are simulated for no scan and large scan cases and the results are compared with the uncompensated case to show performance improvement. In order to demonstrate the technological readiness of the concept a 1.5-m breadboard model is designed to be built for experimental measurements. Some important mechanical design tolerances and realistic array feed topologies are investigated. The antenna concept developed in this paper is advocated to be used in the next generation of geostationary satellite antenna systems for remote sensing radar applications.     

赋形反射面多波束天线优化设计与分析

为了以较低的技术难度实现多个点波束对服务区的高增益、低旁瓣覆盖,提出了一种新型的赋形单口径多波束天线设计方法,通过对反射面赋形来解决传统单口径多波束天线旁瓣电平与波束宽度之间的矛盾.在对反射面优化过程中,将天线口径投影面内的相位分布作为优化变量,利用基于实数编码的遗传算法对其进行调整来获得满足要求的多波束覆盖.数值仿真结果表明:在保证增益大于40 dBi、旁瓣电平低于20 dBi的前提下,该设计能够将波束宽度拓宽为1°,可有效地提高了波束交叠增益,降低了旁瓣电平.     

宽频带平板反射器阵列天线分析与设计

采用表面电流有间隙馈电的Hallén积分方程分析了大直径振子的驻波特性,对限制平板反射器阵列天线工作带宽的主要因素进行了研究,探讨了展宽天线带宽的基本方法和途径;以大直径振子为单元设计了一副八单元平板反射器阵列天线,在一个倍频程内,驻波比小于1.5,增益可达18 dBi,带内起伏小于2 dB,具有较好的方向性,在工程实践中具有广阔的应用前景.     

Bicollimated Gregorian reflector antenna

A bicollimated Gregorian reflector is structurally similar to a classical confocal Gregorian reflector, but its surfaces are shaped to have better scan capability. A geometrical optics procedure is used in designing the reflector surfaces. A three-dimensional ray tracing procedure is used in analyzing the aperture phase errors as the beam is scanned to different angles. The results show that the bicollimated configuration has about 45 percent greater angular scanning range than the equivalent confocal Gregorian reflector antenna.     

Bifocal dual reflector antenna

A bifocal dual reflector antenna is similar to and has better scan capability than a classical Cassegrain reflector antenna. The method used in determining the reflector surfaces is a modification of a design method for the dielectric bifocal lens. Computed radiation characteristics of the bifocal reflector system are compared with those of a classical Cassegrain reflector system. The results confirm that the bifocal reflector has superior scanning performance.     

极小极大值法在赋形反射面天线设计中应用研究

为了使星载天线的远场方向图与服务区的形状相匹配,并在服务区内获得高的增益和交叉极化隔离度,通过雅可比-贝塞尔（Jacobi-Bessel）函数来表示反射面的形状,应用极小极大值（Minimax）算法对单偏置抛物反射面天线进行优化设计。在优化过程中,把表征反射面形状的展开系数作为优化参数,利用物理光学（PO）与物理绕射理论（PTD）相结合的方法来计算远场,同时考虑了天线的增益和交叉极化隔离度,并对反射面的形变量加以限制来保证最终优化得到的星载反射面天线能够应用现有技术和材料加工出来。最后以产生一个覆盖巴西全部领土的赋形波束为例进行了优化设计,数值仿真结果表明：在服务区内主极化增益都高于28.5 dBi,交叉极化隔离度都在21 dB以上。     

Contoured beam reflector antenna for wireless applications

Wireless coverage in urban, suburban, and light industrial areas is a challenging problem for cellular network planners. This is mainly due to scattering from buildings and structures but also because area specific demographic features such as parks, streets, and sports arenas require specialized coverage. A contoured beam reflector antenna is a simple and effective solution for this problem, providing excellent control in both planes of the radiation pattern and a very sharp taper at the edge of coverage. The problem of wireless coverage planning using existing base-station antenna types is discussed, and a potential solution for these problems using contoured beam reflector antennas is demonstrated by examples. The implementation of this solution is made possible by using an inexpensive manufacturing technique involving a reconfigurable mould and a foam extrusion process     

Compact primary source for W-band reflector antenna

A double slot array antenna pasted on the aperture of a standard WR-10 waveguide is presented. Its compactness and airtightness make it suitable for serving as a primary source for reflector antennas. Compared to a standard WR-10 open-ended waveguide, it acts as a small FSS to provide up to 12 dB return loss enhancement within 9% bandwidth centred on 94 GHz, whereas radiation pattern and gain are similar. Good agreement is found between measured and predicted characteristics between 90 and 100 GHz. A return loss improvement is of particular interest while considering an antenna system with short focal length.     

Microwave technique for reflector antenna profile measurement

A method for microwave measurement of the reflector antenna surface profile is described. The technique uses a focused monostatic secondary reflector located on axis at approximately two focal lenths from the reflector under test. Measurement of the two-ways phase change provides profile error information over a set of annular sections. Practical results are provided to illustrate the spatial resolution and sensitivity of the technique.