An optical subarray antenna having antenna nulling applications

A linear subarray type optical antenna is considered for adaptive applications. The antenna has a small number of subarrays whose radiation patterns cover the region occupied by targets and interference in a near-optimum fashion. The subarray design is such that very low subarray pattern sidelobes are produced, thereby allowing operation in the presence of additional strong interference outside the subarray beams. The design of a near-optimum sheet metal antenna to perform these functions is described and the performance is analyzed.     

星载数字调零天线接收技术

调零天线技术是通信系统中抗干扰的重要手段,以军用卫星抗干扰应用为背景,结合数字波束形成技术,讨论了星载数字调零抗干扰天线的设计思路和系统方案,并对系统中的关键技术进行了分析。     

Planar antenna pattern nulling using differential evolution algorithm

Differential evolution algorithm is used for the pattern synthesis of planar antenna arrays with prescribed pattern nulls by position-only and position-amplitude optimization. The position-only optimization for a planar array allows null synthesis in any prescribed direction. For planar antenna array thinning it is necessary to use position-amplitude optimization for problems involving more than two nulls.     

基于ICGA的星载天线自适应调零算法

有效地抑制干扰,最大程度地保障正常通信,是卫星通信的一项关键技术.采用基于整数编码遗传算法(Integer Coded Genetic Algorithm ICGA )的卫星天线自适应调零算法,利用遗传算法不受初始值选择的局限,全局搜索及整数编码的快速性,可以实时实现天线调零.计算机仿真实验表明了该算法的有效性和鲁棒性.     

Concurrent nulling and locations of multiple interferences inadaptive antenna arrays

An approach for concurrent nulling and location (CANAL) of multiple interferences impinging on an array antenna is presented. It is based on the principle of constructing the signal and the noise subspaces from the nulling weights which correspond to different steering directions. In this respect, the data snapshots and their estimated covariance matrix are not required. As in the MUSIC algorithm, the basis of the noise subspace is then used to form a spectrum in which the peak locations define the estimated angles of arrivals. Applebaum optimum weights are employed to delineate the properties of the proposed approach under the assumption of narrowband uncorrelated jamming sources, and providing that the number of steering directions exceeds the number of interferences. CANAL is presented for the general case of unknown noise power. The effect of the desired signal presence on the performance Is discussed     

Simultaneous nulling in the sum and difference patterns of a monopulse antenna

Most adaptive array research has not directly addressed the problem of nulling in a monopulse antenna. Placing a null in the sum does not automatically place a null in the difference pattern and vice versa. Nulls may be placed in the two patterns with the use of separate adaptive weights and controls for the sum and difference channels. However, this requires two sets of adaptive hardware for one antenna. A technique for simultaneous hulling in the sum and difference channels of a monopulse phased array using one set of adaptive weights shared by both channels is described. First, the technique is described for amplitude and phase nulling, then for phase only hulling. In each case, the ability to simultaneously null in both channels with one set of variable weights is theoretically demonstrated.     

HF零位天线系统及其算法

介绍了一种三元阵HF零位天线系统的设计。系统采用分时采样单通道检测技术代替传统的多通道检测技术,解决了困扰开环系统中通道失配的难题。对系统的关键技术：鞭环组合天线、检测通道、信号处理平台、分时采样技术进行了讨论。实验表明,利用MUSIC测向算法以及最小化干扰信号算法,系统能有效地抑制干扰。     

Partial adaptive nulling on a monopulse phased array antenna system

A partial phase-only nulling (PPON) algorithm has been developed and evaluated on a 496-element monopulse phased array antenna system which employs five-bit phase shifters. Using this PPON algorithm allows nulls in the far-field pattern to be steered to the desired directions for a phased array equipped with low-resolution phase shifters to perform simultaneous nulling in the sum and two difference patterns in the environment of multiple jammers. Simulated and experimental patterns are illustrated     

Wide-band nulling performance versus number of pattern constraints for an array antenna

The problem of wide-band pattern hulling for an array antenna is addressed, in particular the relation between the number of constraints imposed and the sidelobe suppression achieved. The two constraint methods considered are multiple nulling over a narrow angular sector and hulling of the pattern and its derivatives at a single point. To first order the sidelobe cancellation is shown to be independent of the actual pattern type and is determined by only two parameters: the number of null constraintsMand the number of sidelobesvto be cancelled. The latter parameter directly translates into a desired hulling bandwidthDelta f. A numerical solution to the problem is offered in the form of curves, from which the number of nulls required to suppress a jammer over a given bandwidth can be conveniently estimated. This number is indicative of how many degrees of freedom a conventional adaptive antenna system must allocate to attain a specific hulling performance.     

Throughput enhancement of frequency-hopping spread-spectrum networkwith adaptive antenna array and packet combining

Packet throughput is analysed and simulated for a slow FH/SSMA network with an adaptive antenna array and packet combining in a Rayleigh fading channel with shadowing. It is shown that pre-processing by the adaptive antenna array and post-processing by packet combining are effective at improving the reception performance of an FH/SSMA network     

Adaptive nulling with multiple-beam antennas

Some of the more prominent features of an Applebaum-Howells type adaptive nulling processor when used in conjunction with a multiple-beam antenna operating over the earth field of view at synchronous altitude are discussed. Incorporation of this scheme with a multiple-beam antenna allows for the use of a large filled aperture in order to obtain pattern shaping capabilities over a limited field of view while keeping the number of antenna output ports at a tractable number. It also leads to a partial decoupling of the adaptive feedback loops, a property which can be exploited to provide significant improvements in the dynamic performance of the control system. Three techniques for accomplishing this improved dynamic performance particularly applicable to multiple-beam antennas are considered.     

Phase-only adaptive nulling with a genetic algorithm

This paper describes a new approach to adaptive phase-only nulling with phased arrays. A genetic algorithm adjusts some of the least significant bits of the beam steering phase shifters to minimize the total output power. Using small adaptive phase values results in minor deviations in the beam steering direction and small perturbations in the sidelobe level in addition to constraining the search space of the genetic algorithm. Various results are presented to show the advantages and limitations of this approach, in general, the genetic algorithm proves to be better than previous phase-only adaptive algorithms     

基于神经网络的多波束天线自适应调零

具有一定的干扰自适应调零能力是对了卫星通信系统的基本要求。本文结合多波束天线特性，提出了一种基于RBF神经网络的MVDR波束合成器干扰抑制方案。该方法可有效避免采样矩阵求逆带来的影响，收敛速度更快，对所需信号参数具有一定的顽健性。计算机仿真验证了该方法的可行性。     

Construction of non-repeating frequency-hopping sequences with no-hit zone

Based on finite field GF(p/sup m/), a new construction of frequency-hopping (FH) sequences with no-hit zone for quasi-synchronous FH code-division multiple-access systems to eliminate multiple-access interference is presented. These new FH patterns are non-repeating and possess ideal Hamming autocorrelation.     

Simultaneous nulling for monopulse array with partially adaptiveweights

A new simple method is described for synthesizing low-sidelobe sum and difference patterns with partially adaptive weights. By partially adaptive, we mean that only part of the weights are adapted for simultaneous nulling. These adaptive weights are shared by the sum and difference channels, leading to a significant reduction in the number of variable attenuators/phase shifters used, as compared to the fully adaptive implementation. An objective function is derived that yields different configurations of the shared adaptive weights. Numerical examples are presented to ascertain the efficacy of the new method for both point and extended interference     

Fixed power allocation with nulling for TDD-based cellular uplink

We propose two fixed power allocation schemes with nulling (FPA-N1 and FPA-N2) for time division duplex (TDD) based cellular uplink according to the location of mobile stations (MSs). In the FPA-N1 scheme, MSs located near a base station (BS) do not transmit data when the wireless channels between the MSs and their home cell BS experience deep fading. In the FPA-N2 scheme, MSs located near cell boundaries do not transmit data when the wireless channels between the MSs and neighboring cell BSs cause high interference channel gain because, in this case, their data transmission may induce large interference to neighboring cells. Numerical results show that the proposed power allocation scheme improves the uplink capacity in cellular networks.     

短波混沌跳频码的FPGA实现

基于离散混沌系统,为克服有限精度效应,采用了m序列对logistic映射进行异或扰动的方法来构造混沌跳频序列。并分别采用FPGA进行数字仿真。研究结果表明;其仿真得到的混沌跳频序列具有较长的周期,符合理论值的相关性和较小的平衡性。研究结果表明,该方法是可行的。适于用来构造短波跳频序列。     

Use of Gaussian beams to compute antenna pattern

The radiation pattern of the primary feed is developed in a set of elliptical gaussian beams (Egb). Each of them has a limited spatial intersection with the reflector. Under several conditions, any incidentEgb creates a reflected beam which is also anEgb and its parameters can be computed directly. The antenna pattern is achieved by summing all the reflectedEgbS. Such operations require shortCpu time (100 seconds typically on aHa Pa 9000/735 workstation). In the proposed paper, we expose the basic principles and key elements of this method in four points. The first one describes the decomposition of the incident field on a set ofEgb. The second point is the use of improvedEgbS with respect to the paraxial approximation to get stabilized radiation pattern in the far field. The third chapter is related to the interaction of an elementary beam with the reflector. Lastly the radiated field is calculated, at any point of space, as the vectorial superposition of the reflectedEgb. This method allows to obtain the radiated field from the near zone to the remote zone with a similar accuracy in a very short time.     

Use of Euler-rotation angles for generating antenna patterns

Antenna patterns are most naturally expressed in spherical coordinates, since the pattern angles represent directions in space. All patterns can be represented by circles on the coordinate sphere. Most patterns are either polar great-circle patterns or equatorial patterns, referring to the coordinate sphere, where all look directions lie in a plane. In some cases, however, the surface containing all of the look directions is a cone, with the origin at the antenna, and the axis along one of the Cartesian-coordinate axes. In general, all patterns are conical, known in the trade as “conics”, and the axes of the cones can be in any direction. Conical patterns are useful in cases where the beam is electronically scanned, and the sidelobes in the plane perpendicular to the plane of the scan therefore fall on a cone, instead of in a plane. Additional examples are patterns of constant range or constant Doppler shift, for airborne-radar antennas, which are all conical patterns. Calculating antenna patterns, in such cases, presents a problem, since the antenna-pattern-coordinate system will generally not be the same as the antenna- or the antenna-radome-coordinate system. The two systems may not even be "square" with each other. But by using the proper Euler angles, the desired antenna-pattern look direction can be easily converted to a coordinate system better suited to the calculations