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.     

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.     

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.     

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.     

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     

基于EIRP最优的智能天线阵赋型算法研究

在实际天线阵列中,由于互耦的影响会使得单天线阵元辐射方向图畸变,导致传统的波束赋形算法性能恶化甚至失效。针对这个问题,文中提出了基于等效全向功率约束条件的粒子群算法,避免了传统的波束赋形算法的失效,提升了系统的等效全向功率。同时,为了减弱干扰方向的影响,文中进一步提出了零陷生成方案。仿真结果显示本文提出的算法不仅能够提升波束的等效全向功率,而且可以有效地生成干扰方向的零陷。     

A retrodirective microstrip antenna array

A Van Atta retrodirective reflector was designed and developed, using an aperture-coupled microstrip antenna array. This reflector possesses the advantage of reflecting high fields to the source point over a wide range of incidence angles and, owing to the low cost and conformability of the structure, is suitable for applications in intelligent vehicle highway systems (IVHS). An approximate theory associated with the reradiation and scattering principles of the reflector is presented for the purpose of understanding and designing the reflector. The utility of the retrodirective reflector was demonstrated by comparison with a plate reflector and a microstrip antenna array without a feed structure. Finally, a reflector with switches in the middle of the microstrip feed lines was investigated for possible applications in communications and remote identification     

A highly integrated millimeter-wave active antenna array using BCB and silicon substrate

A simple and inexpensive packaging scheme is implemented in the design of an active antenna array module. The package consists of etched wells in a silicon wafer in which the components of the module are placed. A benzocyclobutene (BCB) film covers the components and serves as a substrate for interconnections. Prefabricated metallic bumps on the components are used for connection through the BCB film, eliminating the need for wire bonds. Aluminum coating of the silicon wafer isolates the lossy substrate from the millimeter-wave circuitry. This packaging process is applied to form an array of four cavity-backed patch antennas and then integrate it with a down-converter. The resulting active antenna array down-converts a 39-GHz received signal. The only off-wafer interconnects are for the 16-GHz local-oscillator input and a 7-GHz IF output. The effect of the packaging on the down-converter is described and important design features are noted. A detailed loss analysis is conducted based on measurements of the array performance.     

一种新颖的Ku频段宽带微带天线阵的设计

文章设计了一种新颖的Ku频段宽带微带天线阵。该阵列的天线单元为分层结构,通过在馈线增加匹配枝节,上层贴片附加寄生单元,实现了宽频带性能。仿真表明,天线单元的相对阻抗带宽(S11<﹣10 dB)达到了17.2%,频带内增益大于8.4 dBi,四单元天线阵的增益大于15.1 dBi。     

Circularly polarised microstrip antenna array using proximitycoupled feed

A 2×2 circularly polarised (CP) microstrip antenna array using a proximity coupled feed and sequential rotation is described. As compared with a previously presented single-element circularly polarised microstrip antenna with a cross-slot, the new array achieves a much wider impedance bandwidth of 11.18% and has an axial ratio bandwidth of 4.1%. The return loss, radiation patterns and axial ratio of the antenna array were measured and are presented     

Wideband smart antenna theory using rectangular array structures

Smart antenna techniques at the base station can dramatically improve the performance of the mobile radio system by employing spatial filtering. The design of a fully spatial signal processor using rectangular array configuration is proposed. Two-dimensional (2-D) spatial filters that can be implemented by microstrip technology are capable of filtering the received signal in the angular domain as well as the frequency domain. Furthermore, it has wideband properties and, hence, eliminates the requirement of different antenna spacing for applications including various carrier frequencies. The desired frequency selectivity of the smart antenna can be combined with compensation of the undesired frequency performance of a single antenna element, and the result is quite satisfactory for practical implementation. In addition, if the elements of the array are not perfectly omnidirectional or frequency independent, we can compensate for these deficiencies in the design algorithm. Two different algorithms for calculating the real-valued weights of the antenna elements are proposed. The first algorithm is more complex but leads to sharper beams and controlled performance. The second method is simpler but has wider beam and lower fractional bandwidth. Some computer simulation results demonstrating the directional beam patterns of the designed beamformers are also presented.     

Beam scan using the quasi-optical antenna mixer array

The quasi-optical antenna mixer system transforms an RF signal into an intermediate frequency signal just after it spatially receives the RF signal and the local oscillator's (LO) signal. In this paper, we present a novel beam scanning system using the quasi-optical antenna mixer array and describe its principle of operation and the experimental results in the microwave band. The arrival direction of RF signals can be controlled by adjusting the LO incident angle and/or the LO frequency without implementing RF circuits such as phase shifters. Therefore, the novel beam-scanning system has no loss due to RF circuits and can be easily designed because of its simple composition     

Low-cost monopulse antenna using bi-directionally-fed microstrip patch array

A new technique for realising a simple low-cost monopulse antenna using a symmetrical bi-directionally-fed microstrip patch array is described. The antenna is designed and demonstrated at Ka-band. Two squinted beams are radiated from a bi-directionally fed microstrip patch array, and a sum/difference pattern is synthesised using the in-phase and out-of-phase signals achieved using a hybrid ring coupler. The measured return loss is better than 10 dB at the sum and difference port, and the depth at broadside is more than 30 dB.