Optimum aperture monopulse excitations

A unified formulation of the optimization of monopulse antenna performance indices for a specified sidelobe envelope function and/or specified nulls of the pattern is presented. The performance indices considered are beam efficiency, gain factor, and angular sensitivity factor of rectangular and circular apertures. The unconstrained optimization of beam efficiency result in an integral equation, the solutions of which are prolate spheroidal wave functions for rectangular aperture and hyperspheroidal wave functions for circular aperture. These functions reduce, respectively, to Legendre and Zernike polynomials in the case of gain factor and angular sensitivity factor. The double orthogonality properties of these eigenfunctions are used for constrained optimization. The results obtained by this technique for the near-in sidelobes constrained at a uniform level are shown to be in agreement with the earlier works. The method is applicable for other aperture surfaces such as elliptical, ellipsoidal, and spherical.     

圆柱面上的轴向偶极子阵的低副瓣方向图优化综合

本文利用新的非线性最优化方法讨论圆柱面上的轴向偶极子阵的低副瓣方向图优化综合问题，利用阵列的单元可实现增益方向图，我们把阵列综合问题表述为一个约束非线性规划问题，采用新直接法求解该问题即可得出一组使阵列的总方向图满足副瓣指标要求，同时具有尽可能高的方向性系数的激励系数，如果阵列的总方向图不能达到副瓣指标，则可得出一组使阵列方向图在可达到的副瓣方向图综合设计的模拟计算结果。     

空间扫描柱面轴向偶极子阵的低副瓣控制

本文利用约束非线性最优化方法，研究空间扫描柱面轴向偶极子阵的低副瓣综合问题。     

Mutual coupling and sidelobe tapers in phase-only antenna synthesisfor linear and planar arrays

A method of obtaining the lowest possible peak sidelobe levels, given a specified sidelobe envelope, by phase-only variation of the generator phases is presented. A generalization of earlier work by the authors, this technique involves the optimization of a piecewise differentiable objective function using the method of steepest descent to obtain desired generator phases, given prescribed excitation magnitudes. The method has been applied to both linear and planar arrays of radiators, with single-mode mutual coupling effects included to provide realistic data. Values for the various array performance indices are presented, and results indicate that introduction of sidelobe taper improves the array gain while raising the peak sidelobe level somewhat. Inclusion of mutual coupling effects alters the required phases for optimum patterns but does not significantly affect the performance indices of the array     

A simple algorithm to achieve desired patterns for arbitrary arrays

A simple iterative algorithm which can be used to find array weights that produce array patterns with a given look direction and an arbitrary sidelobe specification is presented. The method can be applied to nonuniform array geometries in which the individual elements have arbitrary (and differing) radiation patterns. The method is iterative and uses sequential updating to ensure that peak sidelobe levels in the array meet the specification. Computation of each successive pattern is based on the solution of a linearly constrained least-squares problem. The constraints ensure that the magnitude of the sidelobes at the locations of the previous peaks takes on the prespecified values. Phase values for the sidelobes do not change during this process, and problems associated with choosing a specific phase value are therefore avoided. Experimental evidence suggests that the procedure terminates in remarkably few iterations, even for arrays with significant numbers of elements     

低副瓣任意波束直接合成算法研究

在传统阵列天线波束赋形设计中，通过对阵元天线辐射方向图进行幅度相位加权，获得阵列合成方向图.通常阵元激励幅度相位权值的获取，取决于优化算法对目标方向图和阵列合成方向图的对比，通过对阵元激励幅度相位进行大量随机选参后，获得优化结果.由于算法通常是基于相关的阵元方向图，且算法中缺乏副瓣抑制机制，使得方向图合成效率不高且副瓣效果通常不理想.该文设计了一种任意波束直接合成算法.该方法首先在阵元方向图的基础上获得一组互相独立的高增益窄波束（自由基波束），然后基于此波束进行方向图的直接合成，使波束赋形问题统一到基于自由基波束权值运算的范畴内，对波束赋形问题进行了统一，避免了未知参量的随机优选过程，极大提升了阵列天线波束赋形设计的效率.同时在自由基设计的过程中结合了副瓣抑制机制，且这种副瓣抑制机制与波束赋形过程互相独立，使合成波束的副瓣天然地具备了低副瓣的特征.     

Constrained optimisation technique for general array patternsynthesis

A new technique for controlling the sidelobe level for general array pattern synthesis is presented. The basic idea is to introduce a weighting function to the performance index based on the integral of the power response over the sidelobe regions. This function more heavily weights the array power response further away from the mainlobe, so that in the minimisation of the integral of the weighted power response over the sidelobe regions, very low sidelobes can be achieved. The resulting beam pattern is highly directional. Numerical results show that the proposed technique is very effective for general array geometry sidelobe control design     

基于凸优化的共形阵二维波束优化算法研究

传统波束优化手段应用于共形阵二维波束优化时,存在旁瓣水平高的问题.文中基于凸优化理论,提出了两种适用于共形阵列二维波束旁瓣优化的二阶锥规划方法.第一种是设定主瓣宽度下的最低旁瓣波束形成,第二种是设定期望旁瓣级的高增益等旁瓣波束形成.仿真结果表明相比于常规波束形成和其它波束优化方法,第一种方法在相同主瓣宽度约束条件下可以...     

A pattern synthesis of circular arrays by phase adjustment

A problem of sidelobe suppression of a uniformly excited circular array of monopoles through the adjustment of the excitation phases is dealt with. For this purpose, the method of approximation programming (MAP) is used to determine the optimum excitation phases which minimize the sidelobe level. Galerkin's method is used to analyze the mutual coupling between array elements. The resulting radiation pattern has equal amplitude sidelobes that are lower than those obtained with a cophasal array. The resulting radiation pattern of a 32-element double-ring array, operating atX-band, was measured and reasonable agreement with theory was obtained.     

Difference pattern synthesis in small planar phased arrays

A pattern synthesis technique for low sidelobe arbitrarily scanned difference beams in small planar phased arrays is presented. The approach is based on adaptive array theory and is the development of a technique used for radiation pattern synthesis in linear arrays. The method has been applied to measured element pattern data from a small planar array, which includes the effects of pattern corruption by mutual coupling. The successful synthesis of low sidelobe difference beams is demonstrated, with arbitrary difference plane and scan angle     

Beam pattern design of circular antenna array via efficient biogeography-based optimization

In this paper, an efficient biogeography-based optimization (EBBO) method is proposed to synthesize the circular antenna arrays (CAA) for specific radiation beam pattern properties and null controls. The proposed method achieves the desired beam patterns by jointly optimizing the excitation currents as well as the spaces between the array elements. Three improved components, including chaotic search theory, model learning method and a new random perturbation operator, are introduced into the standard biogeography-based optimization (BBO) to improve the performance of the algorithm. Simulation results show that the maximum sidelobe level obtained by EBBO can be suppressed effectively compared with other algorithms. Moreover, the null controlling performance of EBBO is the best among the algorithms.     

Comparison of different antenna arrays for the BER reduction in indoor wireless communication

In this paper, we use the ultra wideband antenna array combined with particle swarm optimization (PSO) to minimize the BER for indoor communication systems. Three types of antenna arrays, namely the circular shape, L shape, and Y shape arrays, are used in the transmitter and their corresponding BER on several paths in the indoor environment are calculated. On the basis of the topography of the antenna array and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the PSO. The novelties of our approach is not only choosing BER as the object function instead of the sidelobe level of the antenna pattern, but also considering the antenna feed length effect of each array element. The particle swarm optimization algorithm is employed to optimize the excitation voltages and feed lengths for these antenna arrays to reduce the BER. The strong point of the PSO is that it can find the solution even if the performance index cannot be formulated by simple equations. By the obtained antenna patterns, we can know the route with the lowest BER; meanwhile, transmission power using this route can be reduced. Numerical results show that the synthesized antenna array pattern is effective in focusing maximum gain to the line‐of‐sight path for these antenna arrays. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environments. As a result, the BER can be reduced substantially in indoor ultra wideband communication systems. The investigated results can help communication engineers improve their planning and design of indoor wireless communication.Copyright © 2011 John Wiley & Sons, Ltd.     

幅相误差对均匀圆阵列系统性能的影响

幅相误差是制约天线阵系统性能的一个重要因素。本文通过建立存在随机幅相误差时的均匀圆阵列模型,分析了此时均匀圆阵列场方向图函数和功率方向图函数的统计特性;围绕方向性系数、旁瓣电平和半功率波瓣宽度三个系统指标,计算了随机幅相误差对均匀圆阵列系统性能的影响;最后在数值分析的基础上进行了计算机仿真和验证。     

一种相控阵体制的抗干扰分析方法

从信干比角度考虑,传统的全向辐射体制系统很难实现远距离抗干扰通信,而相控阵体制的高增益、低旁瓣特征可以使系统获得一定的抗干扰能力。从信干比分析入手,引入干扰概率指标,给出了一种针对抗干扰能力的统计分析方法,并进行了仿真分析,结果表明,由于阵面规模直接决定了方向图特性,而天线阵的体积、重量、功耗、成本均随阵元数目的增多而增长,所以在总体设计时需要对阵面规模进行折中考虑。该方法已成功应用于系统硬件总体设计。     

Analysis of Effects of System Mismatches on the Performance of Adaptive Generalized Sidelobe Canceller and Compensation Methods

The effect of system mismatches on an adaptive linear constrained generalized sidelobe canceller(LC-GSC) is discussed in this paper.Based on the array gain index,two classic system mismatches,the direction of arrival(DOA) mismatch and the mismatches arising from array disturbance,are studied,respectively.To obtain the effective methods for compensating for the system mismatches,we analyze the performance of the improved LC-GSC with the diagonal loading and additional constraints(such as the directional constraints and derivative constraints).The computer simulations show that the techniques of diagonal loading and additional constraints can effectively compensate for the system mismatches.The loss of array gains can be controlled within 3 dB in the presence of 20% of array disturbances or DOA mismatch when the signal-to-noise ratio is less than 10 dB.The analysis illustrates that the proposed compensation methods are valid and feasible.     

有源相控阵雷达天线实时校正方法

针对有源相控阵天线的超低副瓣、高增益及精确波束指向等性能的实现进行分析研究。首先分析一般相控阵雷达天线及其校正耦合网络的结构,并对实时校正的原理以接收校正为例进行详细的阐述,最后通过某有源相控阵雷达天线实测数据验证该方法的有效性及可行性。     

Array beamforming in the presence of a mounting tower using genetic algorithms

A beamforming method based on genetic algorithms (GAs) is proposed for antenna arrays in the presence of strong platform effects. A GA is used to maximize the mainbeam radiation and minimize sidelobe levels based on the active element patterns of the array. Simulation results show that the array excitations optimized by the GA can achieve superior beamforming performance than those from array theory or phase conjugation. Experimental results collected from a seven-element circular array further demonstrate the beamforming and direction finding performance of the GA based beamformer. In addition, an array element position optimization is carried out. Simulation results show further improvement in the beamforming performance.     

Array pattern synthesis with a controlled mean-square sidelobelevel

The author presents a technique for synthesizing an antenna pattern with a controlled mean-square sidelobe level and a smallest possible beamwidth. The basic idea is to minimize the mean-square error between the array response and the desired response over a mainlobe width subject to a mean-square sidelobe constraint. This formulation results in a quadratically constrained minimization problem. An efficient numerical technique to obtain the optimum weights is presented. Numerical results showed that, under high interference-to-white-noise ratio, the new design approach performs better, on the average, than the Chebyshev technique, in terms of interference rejection     

A variable-coverage satellite antenna system

A multibeam antenna system and-combiner switch capable of producing a variable-coverage radiation pattern are described. The antenna consists of a waveguide lens illuminated by a 19-element feedhorn array. The combiner switch consists of a corporate arrangement of variable power dividers; the latter is made up of two phase shifters and two conventional hybrid power-dividers. An earth-coverage radiation pattern with less than 2-dB ripple and an antenna gain ≈ 20 dB is obtained by equally exciting all beams of the muItibeam antenna simultaneously. Excitation of a single feedhorn results in a narrow beam with an antenna gain ≈ 30 dB and a near-in sidelobe level less -20 dB. The side|obe level can be reduced appreciably by appropriately exciting the adjacent feedhorns. The frequency bandwidth corresponding to 0.5-dB decrease in antenna gain is 10 percent. A technique for computing the radiation properties of the antenna is described; the agreement with measured data is shown to be excellent.     

Array pattern distortion and remedies in space-time adaptiveprocessing for airborne radar

Space-time adaptive processing (STAP) for airborne early warning radar has been a very active area of research since the late 1980's. An airborne rectangular planar array antenna is usually configured into subarrays and then partial adaptive processing is applied to the outputs of these subarrays. In practice, three kinds of errors are often encountered: the array gain and phase errors existing in each element, the channel gain and phase errors, and the clutter covariance matrix estimation errors due to insufficient secondary data samples. These errors not only degrade the clutter suppression performance, but also cause the adapted array patterns to suffer much distortion (high sidelobes and distorted mainbeams), which may result in the rise of false-alarm probability and make the adaptive monopulse tracking and sidelobe blanketing more difficult. In this paper, the causes of the above three kinds of errors to array pattern distortion are discussed and a novel quadratic soft constraint factored approach is proposed to precisely control the peak sidelobe level of adapted patterns. The soft constraint factor can be determined explicitly according to the peak sidelobe level desired and the known or desired tolerant error standard deviations. Numerical results obtained by using high-fidelity simulated airborne radar clutter data are provided to illustrate the performance of the proposed approach. Although the method is presented for STAP, it can be directly applied to the conventional adaptive beamforming for rectangular planar arrays used to suppress jammers