五波束抛物环面天线

本文首先给出了抛物环面天线的辐射场公式,然后利用给出的公式设计和研制出一个90角域的五波束抛物环面天线,并示出了该天线五个波束的测试方向图和中心波束的计算方向图,计算值和测量值吻合很好。最后,还介绍了中心波束和边缘波束的增益测量值。     

宽频带双极化低副瓣偏馈抛物面天线

介绍了一种宽频带双极化低副瓣天线的设计、加工方法和测试结果。采用馈源偏置的方法来减小副瓣,采用波纹喇叭实现天线双极化的要求,并且采用双椭圆切割抛物面来增加天线的效率和减小方位主波束宽度。天线的理论分析与实验结果吻合较好,优于所需的技术指标要求。     

Analytical solution for early-time transient radiation frompulse-excited parabolic reflector antennas

A closed-form analytical solution is developed for predicting the early-time transient electromagnetic fields which are generated by a perfectly conducting parabolic reflector antenna when it is illuminated by a transient step spherical wave due to an elemental Huygen's source located at the focus. This closed-form time-domain solution, which is valid both near and far from the reflector (and anywhere in the forward region) can be used via the convolution theorem to efficiently obtain the early-time transient fields generated by the same parabolic reflector antenna when it is illuminated by a realistic finite-energy pulse which emanates as a spherical wave from the focus. The transient solution is developed here by analytically inverting, in closed form, the corresponding frequency-domain solution in terms of a radiation integral that employs an asymptotic high-frequency geometrical optics (GO)-based approximation for the fields in the aperture. Numerical results are presented for the transient fields both near and far from the reflector. The fields on boresight exhibit an impulse-like behavior similar to that of the impulse radiating antenna (IRA) introduced by Baum et al. (1989, 1993)     

Le Rayonnement D’une Antenne Parabolique Par Une Approche Temporelle Semi-Analytique

This paper describes an original semi-analytic approach to study the field radiated by a parabolic reflector antenna. The method is an extension of Skulkin and Turchin’s work and is based on physical optics approximation in the time domain. Numerical results are presented to illustrate the efficiency of the method. It is noted that the fields can be provided in only a few seconds on a computer with a 400 MHz Rise processor. Numerical results are in good agreement with the finite-element time-domain method.     

用几何光学法计算特殊形状的双镜天线

导出了几何光学法计算双镜天线方向图的求解方程，利用几何光学法并经过特殊处理，计算了椭圆波束变焦距环焦天线和多波束抛物环面天线的方向图。实测结果和理论计算基本一致，从而验证了该方法的正确性。     

On Analysis and Optimization of an Active Cable-Mesh Main Reflector for a Giant Arecibo-Type Antenna Structural System

The active cable-mesh main reflector of a giant Arecibo-type antenna can adjust the illuminated area to a given parabolic surface in time, which is achieved with a flexible cable-mesh structure. This paper addresses the feasibility of the active cable-mesh main reflector, including accuracy adjustment and the influence of the panel curvature. The illuminate area of the reflector needs to be adjusted to a paraboloid, which is implemented by introducing a bias distribution field vector of mesh surface and least norm solution for under-determined equations. Plane panels and spherical panels are investigated. Numerical results show that a much more better surface precision can be obtained using spherical panels     

A high aperture efficiency, wide-angle scanning offset reflectorantenna

A unique single offset reflector antenna has been designed which provides as much as ±30° of scanning in azimuth while maintaining a much higher aperture efficiency than a torus antenna. Like a torus antenna, different portions of the reflector are illuminated for each scanned beam. The reflector profile curve in the plane of scan is found by least squares to minimize the error for the beams with the greatest scan angle, and then polynomial terms of up to sixth order which minimize nonplanar phase errors are added to produce a three-dimensional reflector surface. Numerical simulation indicates very good results for all 0.5° beams in the ±30° azimuth field of view, with peak gain no more than 0.3 dB below ideal and highest side-lobe levels no worse than 13.3 dB below the peak gain. Additionally, comparable performance can be extended to the elevation plane out to 15°/-30°, although full azimuth performance becomes compromised at extreme elevation scan angles. By using an offset design, there is no blockage of the outgoing beam by the feed array assembly for azimuth scanning. With better feed performance than comparably sized paraboloids, and being more compact than similar torus reflectors, this novel antenna should find numerous uses in spacecraft and terrestrial applications     

RF characterization of an inflatable parabolic torus reflectorantenna for space-borne applications

Space-borne satellite applications provide a vast array of services extending from global connectivity to Earth observation systems. The soil moisture radiation mission is a proposed space-borne passive microwave system complementary to the existing Earth observing system operating at low microwave frequencies and requiring an antenna with multibeam, high-beam efficiency, and dual polarization capabilities. To achieve both the large reflector size and the multibeam pattern at the operational frequencies an innovative multibeam reflector antenna design was needed. The advances in inflatable antenna technology has been proposed to overcome the launch vehicle size and weight restrictions. This paper describes a novel offset parabolic torus reflector antenna design that produces the desired multibeam pattern and is compatible with the inflatable antenna technology. Using the system requirements of this mission as an example, the design process for an inflatable parabolic torus reflector antenna is outlined, the development of suitable distortion models is given, and representative RF characteristics are presented. These RF characteristics include far-field patterns, beam contour patterns, beam efficiency, and other key performance parameters. The development of an advanced analytical modeling/numerical tool in support of the design effort is also detailed     

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。     

等离子体前馈抛物面隐身天线的一体化设计

研究了等离子体前馈抛物面隐身天线一体化设计的关键性问题。根据单反射面天线的经典理论公式设计了金属前馈抛物面天线和等离子体前馈抛物面天线,并利用CST仿真软件计算了它们的辐射特性,分析了影响等离子体前馈抛物面天线辐射和散射性能的关键参数。仿真表明等离子体抛物面隐身天线具有和金属抛物面天线一样的辐射性能,同时由于等离子体产生和消失的可控性,不工作时就只有介质外壳,具有极低的RCS,其在带内和带外的单站RCS缩减程度和带宽均大于以往相关文献的设计。通过对等离子体反射前馈抛物面天线的研究,为今后进一步实验研究和开发等离子隐身天线奠定了理论基础。     

Focusing of high power millimeter-wave radiation by a quasi-optical antenna system

The focusing of millimeter-wave radiation from a high power 60 GHz gyrotron is studied using a two-dimensional ellipso-parabolic focusing antenna system. Fine focusing with an elliptic reflector gives a sheet beam of about 10 mm in thickness even at a high power input of about 100 kW. The addition of a parabolic reflector produces a finely focused and nearly Gaussian beam of about 10 mm in diameter with an energy density higher than lOOkWcm^-2. Spatial distributions of beam power are compared with calculations and good agreement is obtained.     

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.     

Parallel plate waveguide antenna for point-to-multipoint communication at millimetre-wave frequencies

Simulation and measurement results for a parallel plate waveguide antenna designed for a point-to-multipoint communication system at millimetre-wave frequencies is presented. The antenna consists of a waveguide feed, an H-plane horn, an enclosed parabolic reflector, a rectangular waveguide containing irises, and corrugated baffles. Half power beamwidths between 4.9/spl deg/-6.0/spl deg/ in elevation and 58/spl deg/-79/spl deg/ in azimuth are achieved for a bandwidth of 13%. The gain varies between 19 and 20 dBi for the frequency range between 21 and 25 GHz. The manufactured antenna is very compact with a size of 200/spl times/147/spl times/50 mm.     

Fan beam generated by a linear-array fed parabolic reflector

The theoretical background and the results of computer simulations and experimental studies for a parabolic reflector fed by a linear array are detailed. The concept of using a parabolic reflector antenna fed by a small linear array to generate fan-beam patterns is validated. Large angle scan along the broad-beam direction of the fan beam can be achieved by offsetting the linear array laterally. It is both empirically and numerically demonstrated that the array feed must be displaced in the reflector's axial direction to an optimum location from the focal plane in order to achieve the best antenna gain performance. As a result, the linear-array fed parabolic reflector can be used in place of a long planar array in a multifunctional reflector antenna system     

抛物环面天线增益和旁瓣特性的研究

本文给出了抛物环面天线的参数方程和辐射场公式。利用给出的公式研究了抛物环面天线的增益和旁瓣特性。最后，对一个实际天线的方向图进行了理论计算，与测量值比较，两者吻合得很好，从而验证了理论分析和计算的正确性。     

一维菲涅尔区相位修正平面反射器的聚焦特性研究

在平面上沿某一个方向进行1/P波长的相位修正,可以构成一维菲涅尔区相位修正平面。由此而得到的平面反射器可作为抛物柱面反射器的替代物来构成扇形波束天线。本文用物理光学法分析了平面波入射时该结构的聚焦特性,并给出了一组焦散区场分布的数值计算结果。     

Antenna factor of compact antenna range for EMC measurements above1 GHz

A formula is proposed for measuring the antenna factor of an offset-fed parabolic reflector operated as a compact antenna range (CAR) by considering the plane-wave approximation and field-distribution in the collimated region. The antenna factor is determined from the half power beamwidth (HPBW) of the feed, the physical geometry of the reflector and a field-distribution correction factor. The proposed formula is in good agreement with the measured results using a standard double-ridged horn antenna as the feed. The formula can be used to design CARs for EMC applications     

Field correlation diffraction theory of the symmetrical cassegrainian antenna

The received field as focused by the parabolic main reflector of a Cassegrainian antenna at the surface of an arbitrary profile subreflector is calculated by a spherical wave expansion. This facilitates the application of the field correlation principle and leads to an expression for aperture efficiency taking into account diffraction effects. A comparison is made with numerical results previously published or obtained by other methods. The potential advantage of the technique is the speed of computation and the capability for synthesis as well as analysis of reflector shapes.     

A high-performance line source feed for the AIO spherical reflector

An aberration-correcting line source feed has been designed, modeled, constructed, and tested in the Arecibo reflector. The feed is a linearly polarized flat wavegnide 40-foot-long array illuminating 700 feet of the 1000-foot-diameter spherical reflector at 318 MHz. The antenna, illuminated by the new feed, yields an aperture efficiency of 70 percent with a peak gain near 56 dB, half-power beamwidth of 16.2 minutes of arc, and sidelobe levels below 4 percent of the on-axis gain. Vignetting losses are approximately 30 percent at the highest zenith angle.     

Ka频段单偏置天线馈源定位精度分析

抛物面天线中,馈源与反射面的相对位置非常重要,因为它直接影响天线电气性能。以Ka频段单偏置抛物面天线为例,分析计算了馈源横向偏焦、纵向偏焦对天线方向图和增益的影响,并给出2组关于馈源偏焦距离与天线第一旁瓣电平和天线增益相对关系图,为今后天线结构设计提供一个理论依据。测试结果表明,该结果可以应用于实际工程。