Dual polarised multibeam antenna

A dual polarised four-beam antenna array for the 1850-1990 MHz frequency band is presented. The polarisations are ±45° to vertical. The antenna has eight inputs corresponding to two orthogonal polarisations and four beams. The return loss and cross-polar isolation for a single Butler beam exceeds 15 and 22 dB, respectively. The radiation pattern is similar to an ideal Butler pattern and the cross-polarisation level is <-21 dB in the beams     

A multibeam antenna using quasi-optical antenna-mixers

A multibeam antenna could be designed without using a complicated feeding system by using quasi-optical antenna-mixers. Accurate beam directions could be obtained when practical antenna patterns was taken into account in the design. The effectiveness of a three-beam antenna is demonstrated at K-band showing accurate beam directions which is very useful in modern wireless communications.     

基于阶梯波形的高效时间调制多波束天线

时间调制阵列(time-modulated array, TMA)可产生不同指向的边带多波束,但存在效率低、波束幅度一致性差等缺陷.本文基于阶梯波形提出了一种低成本高效率的时间调制边带多波束实现方法.首先根据任意多波束空间覆盖需求得到TMA的频谱和时域波形,然后基于数控衰减器和0/π移相器的硬件特性实现对理论调制波形的拟合,最终通过阶梯波形优化抑制无用边带功率和边带波动,实现稳定高效的多波束扫描.以8单元TMA为例实现基频、±1、±2次边带对应的5边带,通过调整数控衰减器的衰减步进值寻求调制波形最优解,最终仿真结果显示边带电平抑制在-31.20 dB,工作边带功率波动仅为0.68 dB.该多波束时间调制天线具有成本低、效率高、波束幅度一致性好、无用边带抑制度高等优点,提升了时间调制技术在多波束天线领域的应用价值.     

多波束智能天线性能的研究

对智能天线进行了详细的研究。介绍了智能天线的概念和分类,分析智能天线与传统天线相比所具有的优势。以多波束智能天线为例,对它在各种环境下的表现进行了详细的分析,证明了其具有的优势。     

On the radiation pattern of a multibeam antenna

The optimum radiation of a lens antenna with an array feed ofMelements is desired, which will exhibit maximum gain in a number (k) of specified directions and nulls in other (j) specified directions. This optimum is not derived; however, a condition for the optimum is shown to be some superposition of just (k + j) individual radiation patterns where each individual pattern is obtained by a separate excitation set of allMfeed elements such that the gain is maximized in each of the (k + j) directions. (The feed array excitation set for each of the (k + j) maximum gain individual patterns is derived.) Thus the number of unknown feed excitation coefficients is reduced fromMto (k + j).     

A dielectric bifocal lens for multibeam antenna applications

An iteration technique is applied to the design of a bifocal dielectric lens antenna. A bifocal lens has two conjugate off-axis focal points and offers good off-axis scanning performance. A computer model was developed to aid in the design analysis and far-field performance evaluation of a bifocal lens. The computer simulation results demonstrate that the bifocal dielectric lens can provide a higher-gain radiation pattern for multibeam antenna (MBA) applications over a large field-of-view. The computer study also indicates that the quadratic phase error can be significantly reduced by constraining the feed along an optimized focal arc     

Ka/Ku频段多波束天线研究

文章主要介绍Ka/Ku频段复合多波束天线,采用模拟多波束体制,通过4组移相器分别控制4个独立波束,实现4个波束实时跟踪卫星。实验证明,通过混合布阵减小天线尺寸,可在较小的空间内实现双频段。     

A biconical multibeam antenna for space-division multiple access

The biconical antenna is well known as an easy to build broad-band antenna with omnidirectional radiation. In this paper, the biconical antenna is modified for selective radiation in the azimuth direction. By enlarging the diameter of the coaxial feed to the biconical antenna, a set of higher order modes can be excited. In addition to the angle independent TEM mode, higher order TE-modes are also allowed for propagation, which result in an angle-dependent far-field pattern. Several features of this multimode excitation are of interest. Applying multiple input feed connectors allows simple rotation of the antenna beam by switching or, when independently operated, transmission and reception for communication in different angular directions for real-time space division multiple access (SDMA). As with conventional antenna arrays, adaptive pattern synthesis can also be realized by using multiple input feed connectors in combination with an appropriate amplitude and phase shifting network. The antenna allows an extremely flexible design of its characteristics at low cost, both requisites for SDMA communication     

Realizable feed-element patterns for multibeam reflector antenna analysis

The radiation pattern of a feed element is approximately described by a simple function(cos theta)^{q}. For a given element spacing of the feed array, we give simple formulas for estimating the practical value ofqwhen the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna.     

基片集成波导双极化多波束天线的设计

提出了一种基于基片集成波导技术的双极化多波束天线设计方法,利用Butler矩阵作为波束成型网络,通过激励成对的正交缝隙辐射单元组,实现双极化多波束辐射特性。通过配置正交辐射单元组之间的相位关系为同相或反相,可以分别实现极化共波束和极化独立波束的多波束辐射特性,从而适应不同无线通信场景需求,利用空间波束分集或极化分集方式提升无线通信容量。最终,在X波段给出了一种基于基片集成波导技术的双极化独立波束的多波束天线设计实例,仿真结果表明该天线阻抗带宽为9.64~10.25 GHz,对4个输入端口分别激励时可实现双极化四波束辐射,波束增益为14 dBi,验证了所提出的设计思想和方法。     

Performance evaluation of a cellular base station multibeam antenna

Experimental test results are used to determine the performance that can be achieved from a multibeam antenna array, with fixed-beam azimuths, relative to a traditional dual-diversity three-sector antenna configuration. The performance tradeoffs between the hysterisis level, switching time, and gain improvement for a multibeam antenna are also examined. The multibeam antenna uses selection combining to switch the signals from the two strongest directional beams to the base station's main and diversity receivers. To assess the impact of beamwidth on overall system performance, the following two multibeam antennas were tested: a 12-beam 30° beamwidth array and a 24-beam 15° beamwidth array. Both multibeam antennas were field-tested in typical cellular base station sites located in heavy urban and light urban environments. Altogether, the system performance is evaluated by investigating three fundamental aspects of multibeam antenna behavior. First, the relative powers of the signals measured in each directional beam of the multibeam antenna are characterized. Then, beam separation statistics for the strongest two signals are examined. Gain improvements achievable with a multibeam antenna compared to the traditional sector configuration are determined in the second phase of the analysis. Results indicate that in excess of 5 dB of gain enhancement can be achieved with a 24-beam base station antenna in a cellular mobile radio environment. Finally, the effects of hysterisis level and switching time are characterized based on gain reductions relative to a reference case with no hysterisis and a 0.5-s switching decision time. Useful approximations are developed for the gain effects associated with varying hysterisis levels and switching times. The resulting design curves and empirical rules allow engineers to quantify multibeam antenna performance while making appropriate tradeoffs for parameter selection     

宽频带多波束天线阵及其RCS的缩减设计

设计了一种工作于P,L波段多波束天线阵,形成的9个波束在方位面实现90°空域范围覆盖。多波束通过模拟延迟线构成的移相网络实现,同时运用小型化技术将移相网络集成到功分网络中。通过印制电路板工艺实现各馈线所需的相移值。阵列单元采用印刷对数周期天线形式,同时在阵列安装座底板上粘贴吸波材料,进而显著缩减了阵列在X,Ku波段的雷达散射截面(RCS)。理论仿真分析及实验测量结果证明,该天线阵不仅具有宽频带、波束方向图特性良好,而且方位面180°范围内平均RCS小于16 m2,满足系统设计要求。     

Study of deployed and modular active phased-array multibeam satellite antenna

A deployed, self-cooled and modular (tile-based) active phased array for multibeam applications has recently been proposed in the literature. This novel antenna facilitates the implementation of large array antennas in space with many beams from the same aperture, offering a flexible payload with the potential for high traffic capacity. However, the configuration also raises some questions about degradation in antenna performance, due to constraints such as non-circular aperture, frame gap, uniform amplitude excitation, and a calibration boom deployed in front of the array. Methods dealing with these issues are discussed in this paper. It is shown that a phase-only optimization technique can effectively reduce interference between same-frequency spatially reused beams, and can compensate for EIRP and C/I degradation for tile-correlated errors and failures.     

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.     

Dual offset reflector multibeam antenna for international communications satellite applications

Dual offset reflector antenna systems offer exciting possibilities for achieving both low scan losses and low cross polarization in geosynchronous communications satellite antennas providing narrow (100 leq D/lambda leq 400) and multiple beam frequency reuse coverages over an18degconical field of view. Novel geometrical configurations for the reflectors are characterized by simultaneously achieving: 1) blockage free apertures for all element beams within the18degconical field of view, 2) compatibility with large planar feed arrays, 3) additional degrees of design freedom by orientation and shaping of reflector surfaces for depolarization and scan loss optimization, and 4) large effectivef/Dratio achieved in compact and foldable geometries. A comparison of new front-fed offset Cassegrain (FFOC) and side-fed offset Cassegrain (SFOC) systems is made.     

Analysis of the effects of water on the ACTS propagation terminal antenna

The NASA advanced communications technology satellite (ACTS) propagation experiment was designed to observe the attenuation produced by rain on Earth-satellite paths operating in the Ka-band. Unwanted effects of water on the antenna reflector surface were noted. Wet-antenna attenuation could be attributed to the combined effect of a water layer on the reflector surface and water wetting the feed window surface. A model was developed to calculate the antenna reflector and feed surface water layer thickness values as a function of position on each surface. The thickness values were used to calculate the additional attenuation produced by the water layers as a function of rain rate on the antenna. The wet-antenna-attenuation prediction model was verified by sprayer tests. The goal of the ACTS propagation experiment was to obtain path attenuation statistics, statistics that represent the effects of rain on the Earth-satellite path but not on the antenna itself. The wet-antenna attenuation prediction model was used to remove the effects of water on the antenna from the combined antenna-plus-path attenuation statistics produced by the experiment. The overall efficacy of the model was demonstrated by comparing the corrected path loss statistics from two ACTS propagation experiment sites with earlier COMSTAR path loss measurements made at or near those sites. The empirical distribution functions from both the ACTS and COMSTAR experiments were identical within the expected uncertainty of an empirical annual distribution of attenuation by rain.     

A coma-corrected multibeam shaped lens antenna, part II: Experiments

A dielectric lens based on the shaping technique described in Part I of this communication was fabricated and tested. This lens was shaped to control the sidelobes and zoned for improved scanning characteristics. Basic antenna measurements were conducted and excellent performance results have been observed. In the prototype lens system with unmatched surfaces, a 4 dB crossover between adjacent beams of -30 dB sidelobes was obtained. The beam was scanned up topm 12degwithout significant coma degradations. This coma-corrected zoned lens was developed for satellite multibeam applications. The multibeam antenna so designed not only reduces the total costs and the payload burden, but also enhances the system reliability and the overall gain compared to a conventional design because no complex feed network is required.     

On-board K-band multibeam antenna configuration with low sidelobes and low crosspolarisation

On-board antennas of 2.5/3.5 m in diameter which cover Japan with 13 beams in 30/20 GHz bands are developed. To achieve intense frequency reuse, a 9-horn cluster feed is adopted. A tower mounted type deployable antenna configuration is selected so as to overcome the fairing envelope limitation     

Beamforming experiment with a DBF multibeam antenna in a mobilesatellite environment

This paper describes a digital beamforming (DBF) multibeam antenna that incorporates a compact digital signal processor (DSP) engine, and the results of using it in a beamforming experiment receiving a satellite signal in a land-mobile environment. A considerable reduction in the scale of the DSP engine has been achieved by using field programmable gate arrays (FPGAs). To capture a satellite signal arriving from an unknown direction, a two-dimensional (2-D) spatial FFT signal processing provides orthogonal multibeam patterns on the broad side of a planar array antenna. The experimental results demonstrated the features of coarse acquisition and tracking of a signal arrival by selecting the strongest of the beams without assistance from direction finding sensors or microwave phase shifters. The DBF multibeam antenna will provide high-quality communications and increase traffic capacity if it is applied to high-gain mobile antennas or multispot-beam base station antennas in cellular or satellite mobile communications     

高通量卫星多波束天线馈电系统PIM控制技术

介绍了无源互调(PIM)产生的机理和控制方法,重点研究了高通量卫星多波束天线馈电系统PIM控制技术,通过采用馈电系统高隔离度优化设计、馈源单元法兰面扼流槽设计、馈源阵安装板PIM源控制设计、Ka频段PIM试验系统低PIM设计等手段,将某Ka频段多波束天线馈电单元的7阶PIM性能控制在高低温(-60~+100 ℃)环境下≤-135 dBm,馈源阵7阶PIM性能控制在常温状态下≤-140 dBm。产品的实际应用验证了所述PIM控制技术的有效性,在工程问题中起到指导作用。