Propagation measurement using antenna array

The design and construction of a 2.4 GHz antenna array suitable for measurement of the time, angle, and complex amplitude of path arrivals in an indoor radio channel are described. Calibration of the array is facilitated with the aid of an anechoic chamber. An optimal least-squares processor is derived, which compensates for systematic calibration errors. Early measurement results are presented, and future direction of the research are indicated     

Design and evaluation of a novel antenna array for azimuthalangle-of-arrival measurement

This paper describes a novel antenna array concept in which a “Y”-shaped distribution of elements is used to achieve uniform angle-of-arrival (AOA) measurement performance in azimuth, and a ground plane is employed to reduce the potential for confusion due to scattering from nearby structures and interference from low elevation angles. A simple method for field calibration of this array is also presented. A prototype has been built and tested in field conditions at 460 MHz. Using maximum likelihood estimation, the array is able to resolve single AOAs to within a few degrees and is able to identify discrete multipath from the same source. A shortcoming of the field-tested design is that it has poor gain along the horizon, due to edge diffraction from the ground plane. To control this diffraction, an elliptical rolled edge termination is proposed. It is shown that a rolled edge increases the horizon gain by 5 dB while maintaining high suppression at low elevations and maintaining a low physical profile     

A novel array antenna for MSAT applications

The issue of reducing the cost of phased array vehicle antennas through the use of a lens feeding arrangement instead of phase shifters at each element is addressed. In particular, the economic viability of a mobile satellite system (MSAT) is largely dependent on the efficient use of the allocated scarce spectrum and orbit as well as the satellite power. The type of vehicle antenna used will play a critical role in achieving this efficiency. A standard design approach for an electronically steered array uses phase shifters at each element to provide beam steering. A method for reducing the required number of phase shifters by using an R-KR lens feed network is outlined. The authors briefly discuss the phase shifter approach to beam steering, examine various lens feed techniques, and describe the R-KR lens approach. The lens feed network architecture is examined, a computer model for simulation of the array is presented, and the results of analysis of a suggested design for the MSAT application are given. In addition, satellite acquisition and tracking considerations are investigated     

一种新型圆形智能天线阵的分析与设计

采用新型同轴直排印刷振子天线结构,易于提高增益和组阵,具有良好的一致性.对优化算法、矩量法、有限元法相结合的方法进行了研究,设计了高效的圆形智能天线阵.验证了其高效性.实验天线为3G通信的研发提供了有效的指导作用,并具有很强的实用性.     

新型强耦合宽带双圆极化阵列天线

空间飞行器由于受到动力和负载的限制, 需要尽可能使搭载的天线轻质小型化.文中提出了一种新型强耦合双圆极化轻质天线.天线单元采用H型缝隙耦合和增加寄生贴片方法, 提高了天线带宽.同时, 通过在辐射贴片、寄生贴片上开圆形槽, 以及金属反射板栅格化的处理, 明显地减轻了天线的质量.采用这种新型天线单元, 设计了8单元的宽带双圆极化阵列天线.仿真结果表明:该阵列天线的中心频率为433 MHz, 左旋和右旋圆极化的相对轴比(Axial Ratio, AR)带宽(AR < 3 dB)分别达到了24.4%和23.2%, 有效实现了小型轻质化宽频带双圆极化阵列天线.     

一种新型和差旁瓣抑制阵列天线

针对传统和差阵列天线旁瓣抑制能力的不足,设计了一种应用于二次雷达的新型和差旁瓣抑制阵列天线.该天线主要由前向阵列、后向单元、波束形成网络和互连的射频电缆构成,其中前向阵列和后向单元共同形成差波束.采用遗传算法对各个天线单元的幅度和相位进行优化,使差波束在工作频带内能够覆盖和波束的旁瓣.仿真和测试结果表明:在13.2％相...     

A novel low mutual coupling microstrip antenna array design using defected ground structure

Defected ground structures (DGS) have been developed to improve characteristics of many microwave devices. In this paper, using FDTD method, effect of DGS to mutual coupling reduction of a two-element microstrip antenna array is investigated. The proposed DGS antenna is compared to other techniques and is shown to have an exceptionally lower mutual coupling between two E-plane coupled elements. Impact of the designed DGS on higher-order modes and radiation pattern of the antenna array is also examined.     

A novel interference suppression scheme for global navigation satellite systems using antenna array

This paper considers interference suppression and multipath mitigation in Global Navigation Satellite Systems (GNSSs). In particular, a self-coherence anti-jamming scheme is introduced which relies on the unique structure of the coarse/acquisition (C/A) code of the satellite signals. Because of the repetition of the C/A-code within each navigation symbol, the satellite signals exhibit strong self-coherence between chip-rate samples separated by integer multiples of the spreading gain. The proposed scheme utilizes this inherent self-coherence property to excise interferers that have different temporal structures from that of the satellite signals. Using a multiantenna navigation receiver, the proposed approach obtains the optimal set of beamforming coefficients by maximizing the cross correlation between the output signal and a reference signal, which is generated from the received data. It is demonstrated that the proposed scheme can provide high gains toward all satellites in the field of view, while suppressing strong interferers. By imposing constraints on the beamformer, the proposed method is also capable of mitigating multipath that enters the receiver from or near the horizon. No knowledge of either the transmitted navigation symbols or the satellite positions is required.     

A retrodirective antenna array using a spatially fed localoscillator

This work investigates a spatially fed local oscillator (LO) for a retrodirective antenna array. Compared to conventional planar transmission-line feed networks, the spatial feed offers a more flexible array layout and easier implementation, especially in large two-dimensional (2-D) arrays. This method of delivery involves radiating the LO through free space to the back-side of the array where it is received by slot-coupled patch antennas and delivered to the mixing elements. A four-element linear retrodirective array utilizing this approach is demonstrated at an LO frequency of 10.7 GHz. Retrodirectivity is observed at scan angles from -40° to +40°     

Locating GSM mobiles using antenna array

The authors consider the problem of accurate estimation of the position of a GSM mobile station based on measurements of the mobile signal made at a single receiving site equipped with an antenna array. Direction of arrival and time of arrival measurements are used to estimate the location of the mobile transmitter. A statistical filtering technique is applied to the location estimates to minimise the effects of multipath fading. Experimental results with a DCS-1800 system are presented which achieve an r.m.s. location error of 133 m, with the error being <250 m for 98% of the time     

Adaptive antenna array using real symmetric array covariance matrix

A novel scheme using a real symmetric array covariance matrix for an adaptive antenna array in DS/CDMA is proposed. A real symmetric array covariance matrix is estimated from a complex array covariance matrix using a unitary transformation and Toeplitz matrix approximation methods. The Hermitian Toeplitzation method not only estimates a persymmetric matrix form for a real symmetric array covariance matrix but also enhances the performance of the received signal by removing the undesired effect obtained from a complex array covariance matrix. Simulation results demonstrate the effectiveness of the proposed scheme     

一种新型宽频带高增益的变极化微带反射阵天线

提出一种由微带反射阵实现的新型变极化天线,它区别于双/多极化天线的固定极化状态.实现变极化的关键是经特殊设计的反射阵阵元结构尺寸和线极化辐射的馈源.理论分析表明:反射极化可涵盖所有极化状态;采用间以空气层的双/多层阵元结构能有效展宽频带;增加阵元数目可提高天线增益.鉴于这些特点,该类天线在雷达、移动通信等领域具有潜在工程应用.还给出了完整的理论分析和实例佐证.     

一种双扼流槽双极化低旁瓣阵列天线

设计了一种新型低副瓣双极化阵列天线,阵列单元采用角锥喇叭,利用探针分层正交馈电实现双极化辐射,利用双扼流槽解决了宽波束降旁瓣的难题.在阵列馈电设计中,利用空气同轴线网络实现泰勒加权降旁瓣设计,同时,利用反相馈电技术改善了极化隔离度和交叉极化.实测结果表明：在工作频带9.5 GHz±500 MHz,回波损耗小于-10 dB,俯仰面、方位面方向图旁瓣电平小于-16 dB,极化端口隔离度小于-30 dB,交叉极化电平小于-35 dB.     

一种新型的介质反射面天线

提出了一种新型的多层介质结构的反射面天线，反射平面上所需要的相位补偿通过选择合适的介质厚度来实现，使用几个多层圆形介质即可满足条件。与传统的高增益天线相比，该结构设计简单，加工方便。验证了几种不同层数的结构和一个等口径的抛物面反射面天线。加工并测试了一个采用Vivaldi做馈源的4层结构的反射面天线。仿真和测试结果均表明该天线具有良好性能。     

A novel wideband antenna design using U-slot

U-slot patch antennas with П-shaped feed slot are studied, and numerical results based on the FDTD method are presented. The effects of varying physical parameters are investigated with a goal of understanding the coupling among different resonators. It is found that the U-slot patch antenna can be designed to attain 50% impedance bandwidth as well as 30-40% gain bandwidth. By altering the sizes of U-slot and feed slot, the wideband characteristic can be changed into a duai-frequency char- acteristic.     

A beam-scanning and polarization-agile antenna array using mutually coupled oscillating doublers

In this paper, a two-dimensional mutually coupled oscillator array is studied for the application of a beam-scanning and polarization-agile antenna array. In the design of antenna array, a two-dimensional oscillator array is implemented in x-y plane, the polarization agility is provided by one dimension (or y-direction) and the other dimension (or x-direction) is for beam scanning. By properly tuning the free-running frequencies of these oscillators, the array radiation direction can be scanned at the selected polarization states including linearly polarized, left-hand and right-hand circularly polarized states. The maximal phase difference of /spl plusmn/180/spl deg/ between coupled oscillating signals is acquired by utilizing their second-harmonic signals. This then gives well-defined phase differences among oscillators for beam scanning in addition to the required quadrature phase difference for circular polarization. The performances of polarization agility and beam scanning for a four-element antenna array are verified experimentally and shown to have the potential for adaptive antenna array applications.     

多波束相控阵天线角度测量方法

在雷达、通信、测控等领域中,基于相控阵天线的幅度和差单脉冲测角技术是基本方法,但该方法通过旋转法向方向图去近似表示子波束方向图,并用一阶泰勒公式近似表示子波束接收信号幅度,从而带来非噪声因素误差,最终导致目标角度估计精度不高。为此,通过相控阵天线同时产生两个形状相同但相互独立的子波束,旋转波束指向中心轴方向的方向图函数来确定两个子波束的方向图函数,并用高阶泰勒公式对子波束接收信号幅度进行近似,从而减少误差。仿真和硬件测试结果表明所提方法能够有效提高测角精度。     

A millimeterwave array antenna using dielectric radiators with pre-beamforming characteristics

An array antenna differing from classical design rules is described. Dielectric primary radiators are used providing prebeamforming features by their inherent characteristic. A line of 1×5 radiators realizes E- and H-plane beamwidths of 8 resp. 40 deg. with an effective aperture equaling less than 50 percent of well-known solutions. An integrated power splitting network ensures equiphase excitation of the radiators.     

频率方向图复合可重构寄生单极子天线阵列

提出了一种能应用于无线通讯系统的新型介质支撑开关寄生阵列天线。基于八木天线原理,天线可以实现频率及方向图的复合可重构。所引入的开关用来切换不同状态的工作频率并实现方向图的扫描。地支结构用来改善天线的阻抗匹配并展宽频带。测量结果表明：天线阵列可以在保证回波损耗小于-10 dB的情况下完全覆盖1710~1880 MHz、1850~1990 MHz及2400~2480 MHz三个移动通信频段,并可以方便地实现频率切换及方向图扫描。     

Integrated active antenna array using unidirectional dielectricradiators

In this paper, design considerations and experimental investigations of an integrated active antenna for space power combining that makes use of unidirectional dielectric radiators (UDRs) are presented and discussed. Attractive electrical performance stemming from proprieties of nonradiating dielectric waveguide structures is used to design a prototype at a frequency of 14 GHz. A UDR feed circuit is implemented by microstrip lines and aperture-coupling is studied experimentally for arrays of two, four and eight radiators. Measurements show high coupling and radiation efficiencies of the proposed excitation method. A power-combining efficiency of 89% was measured and a gain of 23.1 dBi was achieved for an antenna with eight radiators and four amplifiers. It is also shown that such a circuit configuration allows the combination of planar Ku-band monolithic hybrid microwave integrated circuit and UDR components in flexible design of active array antennas