Microstrip adaptive array antenna

A planar adaptive array of three microstrip patch antennas consisting of a central active microstrip antenna and two symmetrical lateral passive antennas is used to steer the beam. An electronic beam scanning of ±20° can be achieved with the control of reactive loads located into the lateral patches     

Tamed adaptive antenna array

The adaptive array under directionaily constrained minimization of power (DCMP) algorithm is improved by adding a "pseudonoise." It is effective to protect the desired signal from cancellation or distortion in such cases as 1) where a coherent interference is incident, or 2) where the desired signal direction for the constraint contains some pointing error, or 3) when the desired signal is broad band, The optimum amount of pseudonoise to be added is also discussed and its formula is given. This system is named "tamed adaptive antenna" since its killing capability is somewhat moderated so as not to hurt the desired signal.     

The control of adaptive antenna arrays with genetic algorithmsusing dominance and diploidy

Adaptation of an antenna array controlled by digital-phase shifters using an advanced operator genetic algorithm is demonstrated. The genetic algorithm continuously optimizes the antenna's received signal-to-noise-plus-interference ratio (SINR) (Applebaum (1976) criterion) under changing interference conditions. Unlike earlier attempts to control adaptive array antennas using evolutionary optimization techniques, the current study uses a genetic algorithm with a population composed of individuals characterized by two chromosomes. Several numerical examples demonstrate that this “diploid” structure improves the ability of the genetic algorithm to adapt to changing conditions when compared with a simple genetic algorithm     

A lens antenna array with adaptive optical processing

This paper presents an X band smart antenna array in which adaptive processing of the received signals is performed by dynamic holographic optical circuitry. The optical circuitry adaptively extracts the principal component of the received signal space, that is the strongest first-order independent temporal component of the ensemble of received signals. The adaptive receiver system can be used, for example, to mitigate multipath interference effects and can separate one received signal from another even though their power spectra may entirely overlap. A prototype two-channel system is designed to fit in a standard-size briefcase and consume less than 50 W of power. The input to the system are modulated waves with a carrier in X band and the output is an electronic demodulated signal. Three major components of this system are described in detail: (1) the quasi-optical lens antenna array front end with angle-of-arrival preprocessing and downconversion, (2) the two-channel electrooptic modulation and optical carrier suppression stage, and (3) the smart optical processor (auto-tuning filter). Component and end-to-end system measurements give quantitative indicators for the usefulness of optical processing in wireless communications     

超宽带平面天线阵列的微带馈电

设计、分析、制作了3种类型的4单元平面超宽带天线阵列,采用宽度按指数渐变的微带线网络馈电,馈电网络和天线单元设计在同一介质基板上,易于加工和集成.给出了天线单元、馈电网络各自的输入特性,并将其与整个阵列输入特性进行了比较.仿真和测量结果表明:这3种类型的天线阵在3.1～10.6 GHz绝大部分频段内的回波损耗小于-10 dB,最大不超过-8 dB,天线阵的增益在8～12 dB之间,远大于单元的增益.     

A high-speed adaptive antenna array with simultaneous multibeam-forming capability

A new type of adaptive beamforming antenna system architecture is proposed for multichannel wireless communications. Multibeam communication with high data throughput is accomplished using the proposed beamformer architecture. The system consists of analog mixers, a multitone direct digital synthesizer (DDS), and a digital signal processor (DSP) controller. The essential idea of multibeam forming is based on a multitone weighting scheme combined with analog-digital hybrid signal processing. While the real-time multibeam construction is realized by the analog mixer circuits and a DDS, the complicated adaptive beamforming and direction-of-arrival estimation algorithms are carried out by the DSP. In this architecture, only one beamformer circuit is required to handle multiple beams, leading to significant reduction in hardware counts. A 5.8-GHz eight-element adaptive beamforming array successfully demonstrates two-beam simultaneous beamforming with less than three degrees of peak and steering errors and more than 20-dB interference suppression. The test-bed exhibits successful two-channel data recovery at 25-Mb/s data throughput in each channel with binary phase-shift keying modulation, for simultaneous dual-beam reception. The bit-error-rate measurement validates the robustness of the communication quality under strong interferences.     

窄波束全向接收的自适应天线阵研究

为了实现对短波频段全空域低信噪比信号的良好接收，本文提出了一种窄波束全向接收的知适应天线阵。文中首先简要回顾了自适应天线阵的基本理论，并针地短波波段频程较宽的特点，提出了一种接收信号频率决定阵元间距的阵元间距动态可变组阵方案，文末通过计算机仿真比较了该方案实现的窄波束全向接收自适应天线阵和常规短波天线阵的性能。     

An adaptive antenna array under directional constraint

The concept of the adaptive system working on the principle of minimizing the output power under the constrained response to specified directions is introduced. Theoretical analysis and computer simulation experiments on this directional constraint system are also presented. By comparison with the computer experiment, the differential equation approach is shown to be useful to predict the behavior of the system. The effect of error in setting the constraint direction is investigated, and it is demonstrated that the system is not very sensitive to such error. This margin can be made even greater by adopting the double directional constraints system. This system is also analyzed theoretically and experimented by computer simulation. History of output power components during adaptation is shown, which enables the comprehension of the behavior of the system.     

Robust perturbation algorithms for adaptive antenna arrays

The generation of a perturbation sequence for an adaptive beamformer is described. This perturbation sequence permits simultaneous adaption and reception by use of weight perturbations that do not obstruct the look direction constraint. It is shown that this sequence is generally shorter in length than previously described sequences and offers scope for computational savings through reduction of the number of projection operations required. Convergence in the mean of the resulting adaptive algorithm is demonstrated. Experiments conducted using a four-element linear array operating in the MW RF range have confirmed that the predicted results are achievable under the nonideal conditions of quantized array weights and finite word length arithmetic     

Modified pre-FFT OFDM adaptive antenna array with beam-space channel estimation

A modified pre-FFT OFDM adaptive antenna array with max-SNIR criterion is proposed, in which the CSI estimation is made on the beam-space. Simulation results show that the proposed scheme can outperform the element-space scheme, especially when strong cochannel interference is present.     

Application of genetic algorithms and simulated annealing techniquein optimising the aperture distributions of antenna array patterns

Simulated annealing and genetic algorithms are used for finding optimum excitations for patterns with null-filling. These methods have the advantage that the optimum aperture distribution with a minimal variation between excitations of adjacent elements is found without searching the entire solution space. A comparison between the performance of both methods shows that genetic algorithms are faster than simulated annealing, for this problem     

Optimum beamforming for pre-FFT OFDM adaptive antenna array

It is well known that orthogonal frequency-division multiplexing (OFDM) is robust to frequency-selective fading in wireless channels due to the exploitation of a guard interval that is inserted at the beginning of each OFDM symbol. However, once delayed signals beyond the guard interval are introduced in a channel with a large delay spread, intersymbol interference causes a severe degradation in the transmission performance. In this paper, we propose a novel pre-fast Fourier transform (FFT) OFDM adaptive antenna array, which requires only one FFT processor at a receiver, for suppressing such delayed signals. We derive the optimum weight set for beamformers based on the maximum signal-to-noise-and-interference power ratio (Max-SNIR) and the minimum mean square error (mmse) criteria, respectively. In addition, we propose a novel mmse-criterion-based commutative optimization scheme, which is more robust to the estimation error of the channel state information. Furthermore, we show the equivalence between the Max-SNIR-criterion-based scheme and the proposed commutative optimization scheme. Computer simulation results show its good performance even in channels where directions of arrival of arriving waves are randomly determined.     

Application of adaptive algorithms to RF antenna arrays

Digital adaptive null-steering techniques are extended to RF antenna arrays by a hybrid approach in which the sampling rate is governed by the processor speed rather than by the signal frequencies involved. Numerical results obtained by computer simulation are presented to demonstrate the feasibility of the concept.     

Synthesis of antenna arrays using genetic algorithms

In this article, two particular methods for the synthesis of the complex radiation pattern of a linear and a planar array, based on genetic algorithms (GAs), are discussed. First, we present a combination of Schelkunoff's method and GAs for linear arrays with arbitrary radiation patterns; then, we consider the synthesis of planar arrays with rectangular cells. The results show the flexibility of GAs to solve complex problems related to antenna synthesis, subject to many restrictions which are difficult to treat by classical optimization techniques. There is good agreement between the desired and calculated radiation patterns     

Co-channel interference canceller using CMA adaptive array antenna

A co-channel interference canceller that uses a constant modulus algorithm (CMA) adaptive array antenna is presented. In this canceller, when a CMA adaptive array antenna captures a co-channel interference signal, a replica of this signal is generated and then eliminated from a received signal, thus a desired signal can be obtained. Computer simulation results show that the proposed canceller can effectively reduce co-channel interference     

The tripole antenna: An adaptive array with full polarization flexibility

The performance of an adaptive array using three mutually perpendicular dipoles (a "tripole") is studied. A desired signal and an interference signal, each with arbitrary angle of arrival and polarization, are assumed incident on the array. Uncorrelated thermal noise is also assumed present on each element signal. The output desired signal-to-interference-plus-noise ratio (SINR) is computed as a function of the signal arrival angles and polarizations. It is shown that for most angles of arrival and polarizations, the array has an excellent ability to protect a desired signal from interference. Certain special cases where the performance is not good are discussed in detail.     

基于共形天线阵的免搜索来波方向估计算法研究

运算量大,受阵列拓扑结构限制是传统基于子空间分解的来波方向(DOA)估计算法的主要问题,这些问题大大限制了其在实际工程中的应用。针对共形天线阵的特殊性,结合实际的共形阵,研究了几种可以应用于任意阵列结构的免搜索DOA估计算法,并比较了这些算法在共形阵上的性能。理论分析和数值仿真表明:在一定条件下这些算法均可在共形阵上取得较优的估计性能。     

Downlink adaptive array algorithms for cellular mobile communications

The capacity of wireless downlink communication to mobile receivers in a dense urban environment is limited primarily by co-channel interference. Downlink adaptive arrays can be used to mitigate this limitation by maximizing the power transmitted to desired in-cell mobiles in the reference cell while minimizing power to co-channel mobiles in neighboring cells. This is accomplished by using uplink measurements to estimate downlink covariance matrices and then solving a generalized eigenvalue problem. Several algorithms are proposed to adaptively estimate the optimal solution and are evaluated using a simplified signal model that allows efficient deterministic performance calculations.     

抗干扰自适应天线阵波束形成零陷算法

针对传统的功率倒置算法应用在卫星信号接收时,不能在有用信号方向上形成主波束,不具有提高信噪比的功能,提出一种新的波束形成零陷算法,提高了该功能。通过软件仿真验证,结果表明提出的新算法克服了功率倒置算法在有用信号方向不能形成主波束的不足,不仅能在干扰方向形成更深的＂零陷＂,而且具有更高的输出信噪比。