Synthesis of linear antenna arrays using Z transforms

It is well known that a linear antenna array with equally spaced elements can be represented by a polynomial whose roots correspond to the nulls of its antenna pattern. Since the linear array has equally spaced elements, its polynomial has only integral powers of the variable, so that the array can be represented by aZtransform. Therefore, the effect of moving roots of the polynomial can be represented as a linear sampled-data system problem, which is solved by using a table ofZtransforms or by discrete numerical convolution. In this paper, the quantitative effects on the array and its antenna pattern caused by moving roots of the polynomial are determined, and these effects are utilized for array synthesis to produce desired antenna patterns. Examples illustrating the use of this new synthesis technique include modification of a uniform array to obtain low sidelobes in the antenna pattern and synthesis of an array to produce nulls in its antenna pattern in the directions of discrete and spatially distributed interference sources.     

Null synthesis by phase control for antenna arrays

The author presents a method for forming nulls in prescribed directions in the radiation pattern P₀ of an antenna array by phase-only control. The method modifies the excitation phases of P₀ , allowing the construction of a sequence of patterns {P_n } having increasingly deeper nulls. A solution is provided by terminating the sequence at a suitable step     

Phase-only synthesis of the radiation pattern of the phased array antenna of a coordinate meter

Design versions of the phased array antenna (PAA) of an object coordinate meter are considered. The array antenna forms the sum radiation pattern and two difference patterns ensuring measuring of the object angular coordinates. The problem of the phase-only synthesis of the PAA sum amplitude pattern with a given shape is solved under the condition of keeping the angular orientation of direction-finding nulls of difference patterns in the pattern scanning direction. Design relationships are derived and a pattern synthesis method based on numerical minimization of a nonlinear functional is described. Synthesis examples are presented.     

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     

Spatial correlations in adaptive arrays

A receiving array antenna can steer its main beam toward any direction by adjusting the complex weight in each element. However it cannot always steer one beam and one null toward two prespecified directions simultaneously with a single set of weights. The ability for an array to steer one beam and one or more nulls simultaneously is determined by five factors: 1) element positions, 2) orientations of elements, 3) antenna patterns of elements, 4) polarizations of signals, and 5) directions of the beams and/or nulls. A coefficient is defined, called spatial correlation, which includes these factors and completely characterizes array beam pointing and nulling. Its application to adaptive arrays is demonstrated. The adaptive array performance is dominated by this coefficient and can be improved by properly choosing the first three factors. Several examples on the selection of element placement in adaptive arrays are presented.     

基于一种新的遗传算法的天线方向图综合技术

给出了一种基于实数编码遗传算法的天线方向图综合方法.在遗传算法模型中采用了向下、向上外推和非一致杂交算子等交叉技术,并结合内插、交换等多种技术形成综合交叉方式.该算法克服了已有算法早熟、对初始群体依赖性等缺陷的同时,较大幅度地提高了算法的收敛速度和可靠性;通过在目标函数中加入零陷方差项克服了现有算法零陷不均衡的缺陷.计算机仿真结果表明,与现有算法相比,该方法用于天线方向图综合具有收敛速度快、零陷均衡、可靠等优势.     

一种干扰零陷加宽的静态波束控制方法

基于静态波束控制技术(Quiescent Pattern Control),提出了一种新的适用于天线零陷加宽的新方法,该方法通过对得到的最优权值按照最小均方误差准则进行二次约束计算出新的权值,从而获得在干扰方向较宽零陷的静态方向图.理论分析和计算机仿真表明,该方法能够很好地克服干扰运动和接收天线平台运动或者震动时对输出信噪比造成的不良影响,具有很好的稳健性.     

On grating nulls in adaptive arrays

The effect of element patterns on grating nulls in adaptive arrays is considered. Two simple array models, a two-element and a three-element array with dipole element patterns, are used to study this question. The element patterns are assumed unequal (i.e., the beam maxima point in different directions). It is shown that element patterns greatly affect the occurrence of grating nulls in the array. Unequal element patterns cause extra grating nulls ("sign reversal grating nulls") to occur, in addition to conventional grating nulls. These sign reversal grating nulls can occur even with element spacing less than a half-wavelength. For a two-element array with dipole element patterns, it turns out that grating nulls cannot be avoided if the spacing is greater than a half-wavelength. However, with more than two elements, the situation is not so bleak. An example is given of a three-element array with dipole patterns and one-wavelength spacing in which all grating nulls are eliminated.     

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.     

A novel nulling algorithm in the subarray of a large array

I. Introduction In order to cancel the interferences from certain directions, the problem of forming nulls in the an- tenna pattern is very important. Many researches in this area of adaptive nulling systems have been done For example, the method discussed by Applebaum[1] maximizes the Signal-to-Noise Ratio (SNR) and the one presented by Drane-McIlvenna[2] maximizes the antenna gain. In most conditions, both methods can meet the requirement. However, the performance of the pattern is unsa…     

Phase-only synthesis of nulls in the sum and difference radiation patterns of the phased array antenna of a coordinate meter

Two approaches to the phase-only synthesis of nulls in radiation patterns (RPs) of the phased array antenna (PAA) of a coordinate meter are considered. The approaches use the specificity of the structure of the sheet of the measuring PAA. Such a PAA forms the sum RP and two difference RPs, which ensure measuring of the angular coordinates of an object. The problem of the phase-only synthesis of pattern nulls in prescribed directions in one or several PAA RPs with the angular orientation of the nulls of difference RPs kept in the RP scanning direction is solved. Design relationships are derived and a RP synthesis method, which is based on iterative univariate minimization of a nonlinear functional and includes analytic determination of the minimum of this functional at each iteration, is described. Examples of the array pattern synthesis are presented. The effect the phasing increment on the depth of formed nulls is analyzed and the dependence of the value of the PAA RP in the scanning direction on the position of the formed null is investigated. The effect of synthesized nulls on the shape of the PAA direction-finding characteristic is analyzed.     

Independent null steering in the sum and difference patterns of antenna arrays using real weights

A method for steering nulls in the sum and difference patterns of a phased linear antenna array using only real weights is introduced. The proposed method decouples the weights so that a given jammer is associated with a given weight value. A change in the jammer's direction changes only its corresponding weight value without affecting the other nulls. The main beam is steered independently using a progressive phase shift. This allows the signal-to-jammer power ratio to be maximized with relative ease. The drawback of this method is that the number of jammers that can be nulled will be reduced to about a quarter of the number of array elements.     

Customized pattern applications of the FM CBR antenna

The CBR (cavity-backed radiator) panel element has been proven to have high versatility and predictability in multiplexed FM antenna array radiation patterns. Special customized patterns with deep nulls (notch patterns) are discussed. The desired patterns can be accomplished by skewing the corresponding CBR elements off center by an appropriate amount and by adjusting the electrical phase of the corresponding feedline in order to obtain the necessary phase difference between the adjacent cavities     

干扰子空间正交投影快速零陷跟踪波束赋形算法

该文针对LEO星载阵列天线抑制角度动态变化的有源干扰的需要,提出一种干扰子空间正交投影的快速零陷跟踪波束赋形优化算法。算法采用干扰子空间动态更新与迭代正交投影,不断快速修正零陷位置,并通过迭代傅里叶变换(IFT)技术进行优化加速。所提出的快速算法在整个干扰零陷跟踪过程中,具有稳健和精确的控制方向图主瓣赋形区形状和阵元电流激励系数动态范围的能力,同时具备自适应最小化方向图旁瓣电平的能力,适用于星载系统在线实时计算。仿真实验验证了算法的快速性、有效性和稳健性。     

Resistive tapers that place nulls in the scattering patterns ofstrips

Tapering the resistivity on the surface of an object modifies the scattering patterns of that object. For instance, gradually tapering the resistivity on a strip, half-plane, or an antenna ground plane reduces the edge effects of that surface. Greater control over the sidelobe response of the scattering pattern of a strip is possible by relating the resistive taper to a low sidelobe taper via physical optics. The idea of relating antenna aperture tapers to scattering patterns is extended to placing nulls in the sidelobes of scattering patterns of strips. A resistive taper for placing nulls is found by solving the scattering integral equations of a resistive strip for the resistivity, then substituting the desired nulling current density taper into the appropriate equation and solving for the resistive taper. This method is capable of placing multiple nulls in the bistatic scattering pattern or a single null in the backscattering pattern     

Antenna array pattern nulling by controlling both amplitude and phase using modified touring ant colony optimization algorithm

This paper presents an efficient method, based on the modified touring ant colony optimization algorithm, for null steering of linear antenna arrays by controlling both the amplitude and the phase of array elements. The maximum sidelobe level, the null depth level and the dynamic range ratio are taken into account in the pattern synthesis. Simulation results for Chebyshev patterns with the imposed single, multiple and broad nulls are given to show the effectiveness of the proposed method.     

Position-only planar hexagonal array antenna pattern nulling with simultaneous side lobe reduction at multiple azimuth planes

This article presents a study on the placement of multiple nulls as well as minimization of side lobe level in the radiation pattern using a planar hexagonal antenna array structure in two different vertical planes. The desired null depth is achieved to suppress the interference signal by the position-only control of the uniformly excited isotropic antennas in the array structure. The immediate solution to the mentioned computational problem is reached by various meta-heuristic optimization algorithms such as teaching learning-based optimization (TLBO), symbiotic organism search (SOS), and moth fly optimization (MFO) within a considerably reduced processing time with a control over the design constrains. Various examples for diversified scenarios are demonstrated to place multiple deep nulls in the radiation pattern without compromising the pattern constraints and all other radiation pattern characteristics. This experiment sought to illustrate and quantify the unique benefits and limitations of proposed technique using three considered meta-heuristic optimization algorithm.     

应用遗传算法进行阵列天线综合

该文采用了两种基于遗传算法的方法对线阵列天线进行了综合。仿真结果表明,这两种方法均能够逼近Chebyshev综合的结果。与Chebyshev法相比,具有灵活性强,不受天线工作频率限制等优点。其中第二种方法将遗传算法与Schelkunoff法结合起来,能够方便精确地在指定位置得到零点并满足其它的优化条件。     

发射自适应波束形成技术研究

在天线阵发射波束时进行方向图零点控制是现代雷达采用的先进技术之一,该文分析了一种唯相位共轭梯度自适应于扰置零算法,并详细叙述了我们研制的基于TMS320C31的雷达自适应干扰对零阵列处理实验系统。理论分析和实验结果均表明系统能有效置零抑制干扰、是一种实用性强的系统。     

基于压缩感知的自适应数字波束形成算法

该文根据目标在空间的稀疏性,提出了接收端的基于压缩感知理论的自适应数字波束形成算法。在阵元稀布的情况下,用压缩感知的压缩采样理论,恢复出缺失通道的回波信息,然后用恢复的信号做数字波束形成。该算法所形成的波束具有波束旁瓣低,指向误差小,干扰方向零陷深,而且没有栅瓣等优点,波束性能接近满阵时候的波束性能,而且使用该方法减少的阵元数远远大于其他稀布阵方法减少的阵元数。采用蒙特卡罗方法对该方法进行了性能评估,给出了不同信噪比、不同干噪比、不同快拍情况下的计算结果,仿真结果也验证了该算法的正确性。