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.     

三频双圆极化北斗天线的设计

设计了一款新型的小型化多频段圆极化北斗天线。天线采用双层层叠结构设计,上层天线采用矩形贴片切角开缝的方法,实现北斗系统L频段的左圆极化;下层天线利用复合左右手传输线结构进行设计,通过在矩形贴片中间位置加入非对称十字和直角折线槽结构,同时在四角位置加入90o折线结构和金属过孔,实现北斗系统B1频段、S频段以及GPS L1频段的右圆极化。天线尺寸为39 mm×39 mm×6.8 mm。仿真结果表明该天线各项指标均满足北斗系统对天线性能的要求。     

Ray tracing method for doubly curved reflector surfaces

Shaped reflector surfaces designed for microwave antennas are often defined by a regular grid of discrete points. A ray tracing procedure useful for computing aperture and power distributions produced by an arbitrarily shaped reflector surface is described.     

A wider band microstrip antenna for circular polarization

Circular polarization is achieved by separating two degenerate orthogonal modes in an annular ring patch antenna, by using an ear at the outer periphery. The analysis of such a structure is performed by using the generalized transmission line model. It is found theoretically that this structure can be used to generate circular polarization over a wider frequency range than other structures. An annular ring is designed and its performance is evaluated. Good agreement between the theory and the experiment is obtained. It is also found that the axial ratio bandwidth is higher for the TM₁₂ mode than the TM₃₂ mode of operation in an annular ring antenna     

Rectangular microstrip antenna for circular polarization

Richmond's reaction integral equation method is used to design a rectangular microstrip patch to produce a circular polarization. A rectangular patch with the aspect ratioa = W_{x}/W_{y}, in the range 1.015- 1.02 and corner fed by a microstrip line, produces circular polarization. For substrate with thicknessd = 0.16cm,a = 1.017the nearly square patch gives maximum bandwidth.     

Electric tripole antenna for circular polarization

The feasibility of using the tripole antenna for circular polarization was experimentally investigated. Measured impedance and radiation patterns were in agreement with the predictions from the infinitesimal tripole model. For simultaneous operation in both senses of circular polarization the tripole antenna must be fed by a special separator network, preferably of the nonreciprocal type.     

Analysis of circular reflector antenna covered by concentricdielectric radome

The radiation from a two-dimensional cylindrical reflector antenna with a concentric dielectric radome is analyzed in an accurate manner for both H and E polarization cases. The problem is first formulated in terms of the dual series equations, and then it is regularized by using Riemann-Hilbert problem technique. The resulting matrix equation is solved numerically, with a guaranteed accuracy, and sufficiently little CPU time is needed. The feed directivity is included in the analysis by the complex source point method. Various characteristic patterns are obtained for the front-fed reflector antenna geometries in this study     

A design procedure for classical offset dual reflector antennaswith circular apertures

A geometrical optics procedure for designing electrically optimized classical offset dual reflector antennas with circular apertures is presented. Equations are derived that allow the size and spacing of the main and subreflectors of the antenna system, along with the feed horn subintended angle, to be used as input variables of the design procedure. The procedure, together with these equations, yields an optimized design, starting from general system requirements. The procedure is demonstrated by designing both an offset Cassegrain and an offset Gregorian antenna, and is validated by analyzing their radiation patterns using physical optics surface current integration on both the main and subreflectors     

Printed ring slot antenna for circular polarization

A new design of a microstrip-line-fed circularly polarized printed ring slot antenna is proposed. Circular polarization (CP) radiation of the proposed design is achieved by introducing proper asymmetry in the ring slot structure and feeding the ring slot using a microstrip line at 45° from the introduced asymmetry. The asymmetry introduced in the proposed design is a meandered-slot section and the proposed CP design can be applied to printed square and annular ring slot antennas. Prototypes of the proposed design have been implemented. Experimental results show that good CP radiation performances are obtained and the 3 dB axial-ratio CP bandwidths obtained for the square and annular ring slot antennas are about 4.3% and 3.5%, respectively     

Printed figure-of-eight wire antenna for circular polarization

A new printed wire antenna with circular polarization properties is presented. The geometry of the printed wire which takes the form of a figure-of-eight has a total length of 1.3/spl lambda//sub o/ and serves as a nonresonant traveling-wave antenna. It is shown that a 3-dB axial ratio bandwidth of 15% can be achieved. The half-power and 3-dB axial ratio beamwidth is approximately /spl plusmn/45/spl deg/, while its gain is of the order of 6.5 dB.     

Dual-frequency microstrip antenna with dual circular polarisation

A single-feed dual-frequency microstrip patch antenna that can produce dual circular polarisations (CP) is presented. The microstrip antenna has an annular-ring patch and is excited by an L-shaped microstrip line through the coupling of a ring slot in the ground plane. The occurrence of the dual CP is because the magnetic currents circulating along the ring slot at two specific frequencies have opposite flowing directions. Both simulated and measured results are provided to validate the CP performance of the proposed antenna     

A novel frequency-scanned reflector antenna

Theoretical and experimental results are presented for a frequency-scanned antenna composed of a line source and a frequency-scanned reflection grating that is shaped to a cylindrical reflector. The principle considering is to select the grating geometry such that the first higher-order diffracted wave propagates and serves as the frequency-scanned beam. An analytical solution for the cylindrical reflector geometry that gives a line focus is given. The grating structure considered consists of an array of dipoles placed over a ground plane. The design of the dipole grating for optimum blazing (i.e., for optimal power conversion from the incident wave to the diffracted wave) is discussed. For the theoretical analysis Floquet's theorem and the method of moments are used     

Cross polarization in dual reflector antennas--A PO and PTD analysis

A physical optics (PO) and physical theory of diffraction (PTD) analysis of symmetric and offset dual reflector antennas is performed. It is shown that in most cases PO gives sufficient accuracy, but the PTD correction can be of importance to determine the depolarization, especially if the subreflector edge taper is low.     

一种圆极化可重构微带天线的设计

对圆弧寄生单元微带天线进行了理论分析,设计了一种圆极化可重构的圆形微带天线。该天线通过电控开关控制圆弧寄生单元的状态,从而实现左、右旋圆极化的转换。并利用仿真软件HFSS13.0对天线的特性进行了仿真验证。结果表明,在天线回波损耗S11<–10 dB时,该天线在频段为2.38~2.51 GHz,3 dB轴比带宽为30 MHz,且最大辐射方向处正交极化差达20 dB以上。天线的整体辐射性能良好,且结构简单易于实现,很容易在低频段匹配到50,能够满足WLAN在2.4 GHz频段的要求。     

Low-profile dual-frequency circular microstrip antenna for dual ISMbands

A novel dual-frequency design of a singIe-layer, single-feed circular microstrip antenna for dual ISM bands is demonstrated. Due to the embedding of an offset open-ring slot in a circular patch, a novel dual-frequency operation with its two operating modes centred at about frequencies 2.4 and 5.2 GHz has been obtained. The two operating frequencies have similar broadside radiation patterns and same polarisation planes, and small antenna-gain variation. Details of the antenna design and experimental results for the proposed antenna are presented     

High gain linearly polarised dual band horn for multi-feed reflector antenna

A simple linearly polarised dielectric-loaded horn with high aperture efficiency over two separate frequency bands is presented. The horn operates as a fundamental-mode dielectric-lined horn at the low frequency, and as a dual mode horn at the high frequency. Aperture efficiency better than 92.7% has been measured over the dual 4/6 GHz frequency band.     

Cross-slot-coupled microstrip antenna and dielectric resonatorantenna for circular polarization

Circular polarization (CP) design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line is demonstrated. The proposed CP design is achieved by choosing a suitable size of the coupling cross slot, which results in the excitation of two near-degenerate orthogonal modes of near-equal amplitudes and 90° phase difference. This CP design can be applied to both configurations of microstrip antennas and DR antennas and has the advantages of easy fine-tuning and less sensitivity to the manufacturing tolerances, as compared to their respective conventional single-feed CP designs. For the proposed design applied to a low-profile circular disk DR antenna of very high permittivity studied here, a large CP bandwidth, determined from 3-dB axial ratio, as high as 3.91% is also obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed     

一种弹载宽带圆极化天线阵设计

本文设计了一种工作于X波段的弹载宽带圆极化四元阵.该阵列天线以印刷八木天线为基本单元,围绕导弹均匀布置,组成旋转对称的十字型结构.4个馈电端口的相对相位依次为0°、90°、180°和270°.利用镜像原理,使得单元天线尺寸减小了一半,实现了小型化,便于与载体共形.测试表明,该天线阵在整个X波段内回波损耗小于-10 dB,极化轴比基本小于3 dB,主辐射方向指向导弹正前方,平均增益为4.5 dB,满足设计要求,这与仿真结果较为一致.