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     

Cosine pattern synthesis for single and multiple main beamuniformly spaced linear arrays

The method of cosine pattern synthesis for single- and multiple-main-beam equispaced linear arrays is introduced. The cosine pattern function is characterized by the position of the main beam in the &thetas;-domain and its half-power beamwidth. The Fourier series and Woodward-Lawson methods are applied to the special cases of single- or multiple-main-beam cosine pattern synthesis. The patterns produced by application of these classical shaped-beam synthesis methods can then be used as initial patterns for iterative and perturbational techniques. Examples are presented and discussed, including the use of multiple-main-beam cosine pattern synthesis to design a high-power, high-frequency, ground-based transmitter for the creation of an array of `wireless' ionospheric dipoles     

一种有阵元间距约束的稀布阵天线综合方法

提出了一种基于改进遗传算法的稀布阵综合新方法,用于优化设计有最小阵元间距约束的稀布线阵.该方法利用个体的实值编码提高了遗传算法的优化效率,通过设计遗传操作预处理和后处理,并采用一种广义的交叉算子和变异算子,有效地避免了基因重组和变异时出现不可行解.在给定阵列孔径和阵元数的条件下,高效地实现了任意最小阵元间距约束下抑制稀布线阵峰值旁瓣电平的稀布直线阵列综合.给出了应用该方法的具体步骤,并通过仿真实验证实了该方法的有效性和稳健性.     

A flexible optimization method for the pattern synthesis ofequispaced linear arrays with equiphase excitation

A synthesis method is proposed for linear arrays having equiphase excitation currents. In addition to allowing for the exact specification of the beamwidth and for the specification of individual sidelobe levels by index or as a function of bearing (e.g., angularly extended nulls), multiple deep narrow nulls can be specified at arbitrary bearing angles. The method is suitable for the design of broadside or endfire arrays with sum or difference patterns and can also be used for the design of superdirective arrays with good radiation efficiencies and sensitivity properties. For computational efficiency, the method uses a new constrained multivariable Remez-type L_∞ approximation technique     

Pattern synthesis in small phased arrays using adaptive arraytheory

A pattern synthesis technique for low sidelobe difference and scanned beams in small phased arrays is presented. The approach is based on adaptive array theory and is a development of a technique used for beam synthesis in an ideal, λ/2 spaced, isotropic array. The method has been applied to measured element pattern data from a five element linear array, which includes the effects of pattern corruption by mutual coupling. The successful synthesis of low sidelobe sum and difference beams are demonstrated, with the look direction on and scanned off boresight     

A method for the optimal pattern synthesis of linear arrays withprescribed nulls

A new L_∞ optimal method for the synthesis of equispaced linear array functions with asymmetrical far-field pattern functions is proposed. This iterative method provides for the exact specification of the beam width, while at the same time allowing for the specification of the relative levels of individual sidelobes by index or as a function of bearing (e.g., angularly-extended nulls), as well as the realization of specified narrowband nulls. The resulting array factors are optimal in the weighted L_∞ sense and, in general, have complex coefficients. This new Remez-type method employs multiple objective functions to provide the degrees of freedom that are required for exact null placement. Examples which demonstrate the design flexibility offered by the method are included for various sum and difference patterns, including superdirective and shaped-beam arrays     

Evolutionary optimization for pattern synthesis and reduction of mutual coupling of linear antenna arrays

Optimal design of antenna arrays to minimize the mutual coupling effects in the geometrical arrangements of the linear antenna array (LAA) and circular antenna array (CAA) is dealt with in this work. Two different cases are considered to reduce the effect of LAA and CAA: Case‐1 in which the current excitations of the antenna array are considered to get the optimal radiation pattern of two geometry called LAA and CAA and Case‐2 in which inter‐element spacing and current excitations are both optimized for LAA geometry. A cost function that involves the mutual coupling factor as an optimization factor is developed to reduce the side lobe level (SLL), which takes mutual coupling effects into consideration. Excitation values and inter‐elemental spacing are optimized using particle swarm optimization (PSO). In LAA, for 8‐, 12‐, 16‐element arrays, SLLs are reduced by ?15.52, ?16.71, and ?17.78 dB in Case‐1. For the same sets of element arrays, SLLs were reduced by ?17.35, ?19.71, and ?20.26 dB in Case‐2. In CAA, the current excitations of the antenna array are optimized. For 8‐, 12‐, and 16‐ element arrays, SLLs are reduced to ?7.405, ?10.52, and ?9.43 dB, respectively. The arrays coded with the help of MATLAB based computation and the results obtained by MATLAB are validated by using CST.     

Initial value independent optimisation for flat-top power pattern synthesis using non-uniform linear arrays

A multi-stage optimisation method for solving the nonlinear least square error problem in flat-top power pattern synthesis using non-uniform linear arrays is presented. The optimisations are conducted from low to high order in eigenspace, and without the requirement of multidimensional initial value. Simulations show the robustness of the method over a conventional method dependent on initialisation.     

Pencil-beam pattern synthesis for arbitrary arrays

A pencil-beam pattern is synthesised, based on maximisation of the signal-to-interference-plus-noise ratio (SINR). Artificial interference is introduced and is iteratively adjusted to approximate the desired pattern. In particular, a set of linear equations is derived to find an efficient adjustment for the artificial interference which makes the iterations converge quickly     

Mutual coupling and element efficiency for infinite linear arrays

A formulation is presented of the interrelationship among mutual coupling element efficiency, active impedance, and element radiation patterns for infinite linear (uniformly spaced) arrays. Numerical results are obtained for element efficiency and mutual coupling when the array elements are elementary dipoles. A new lower upper bonnd is obtained on element efficiency. This upper bound is expressed directly in terms of the element patterns in the open-circuit array environment.     

Least squares pattern synthesis for conformal arrays

The problem of synthesising low sidelobe beams from conformal arrays consisting of few elements and large radius of curvature is addressed. Experimental results are presented for a 12 element array of linearly polarised elements forming a faceted array with radius of curvature 1.5 m. It is shown that by calculation of an aperture correcting matrix, sidelobe levels of 40 dB can be obtained from the array by application of conventional linear array Taylor weights. Beam steering is achieved by aperture phase tapering while low sidelobe levels are maintained     

A numerical pattern synthesis algorithm for arrays

A numerical technique for pattern synthesis in arrays is presented. For a given set of elements, the technique allows one to find a set of array coefficients that steer the main beam in a given direction and yield sidelobes meeting a specified criterion, if such a set of array coefficients exists. If the pattern specifications cannot be met with the given elements, the algorithm finds the best attainable pattern. The advantage of this technique is that it can be used with an arbitrary set of array elements. Different elements in the array can have different element patterns, and the array can have arbitrary nonuniform spacing between elements. The synthesis technique is based on adaptive array theory. The given array elements are assumed to be used as the elements of an adaptive array. The main beam is pointed in the proper direction by choosing the steering vector for that direction, and the sidelobes are controlled by introducing a large number of interfering signals at many angles throughout the sidelobe region. The algorithm iterates on the interference powers until a suitable pattern is obtained     

期望主瓣响应下任意阵方向图综合方法

为实现任意阵列天线的方向图综合,特别是考虑到不同空间指向对阵列方向图的影响,提出自适应原理与凸优化理论相结合的方向图综合法.该方法首先利用自适应原理综合法得到所需阵列方向图的旁瓣特性;而后,选择零度角的方向图主瓣作为期望主瓣;最后,在该期望主瓣响应下,将阵列方向图综合问题转化为二阶锥规划问题.采用凸优化循环迭代算法,完成对非凸优化问题的求解,从而保证方向图在满足期望主瓣响应的同时,使旁瓣特性与自适应方向图综合方法得到的结果最接近.理论分析与仿真结果表明,综合后阵列方向图在不同空间指向上具有与期望主瓣一致的主瓣特性,且其旁瓣也能够很好地保持对动态干扰的抑制特性.     

Analysis of the element pattern shape for circular arrays

Recent theoretical and experimental investigations have established the phase-mode technique for directional pattern synthesis in circular arrays of nonisotropic sources. For non-isotropic sources the possibility of phase-mode stability has emerged, indicating wideband directional patterns. In the letter a further examination analysing the shape of the element pattern for phase-mode stability is presented.     

Pattern synthesis for arbitrary arrays using an adaptive arraymethod

This paper presents a new pattern synthesis algorithm for arbitrary arrays based on adaptive array theory. With this algorithm, the designer can efficiently control both mainlobe shaping and sidelobe levels. The element weights optimize a weighted L₂ norm between desired and achieved patterns. The values of the weighting function in the L₂ norm, interpreted as imaginary jammers as in Olen and Compton's (1990) method, are iterated to minimize exceedance of the desired sidelobe levels and minimize the absolute difference between desired and achieved mainlobe patterns. The sidelobe control can be achieved by iteration only on sidelobe peaks. In comparison to Olen and Compton's method, the new algorithm provides a great improvement in mainlobe shaping control. Example simulations, including both nonuniform linear and planar arrays, are shown to illustrate the effectiveness of this algorithm     

改进的快速稳健任意阵列天线方向图综合方法

针对任意阵列天线的方向图综合问题,提出了改进的基于线性约束最小方差准则方向图综合方法.该方法充分考虑综合方向图和参考方向图之间的相对幅度对方向图综合的影响,通过对迭代公式增加一比例常数,使得两者之间的相对幅度对干扰功率变化率的影响增强,不仅提高了干扰功率的迭代效率,即降低了迭代的次数,提高了方向图的综合效率,而且使得迭代系数的取值范围得到了扩展,即降低了迭代系数对方向图综合的影响,增强了方向图综合方法的应用范围和适用性.仿真分析验证了理论分析的正确性和所提方法的有效性.     

Reduction of sidelobes in uniformly excited arrays with element pattern control

Uniformly excited arrays of identical elements suffer from high close-in sidelobes. Suppression of sidelobe levels can be achieved by tapering the aperture amplitude distribution, but a more complex feed network results. A novel form of amplitude tapering is described, in which element pattern control in uniformly excited arrays is shown to theoretically reduce close-in sidelobe levels.     

On the scattering cross section of passive linear arrays

A general formula is derived for the scattering cross section of a passiven-element linear array consisting of isotropic radiators. When all the reactances are tuned out and scattering in the mirror direction is investigated, it is found thatA_{sr}, the relative scattering cross section is equal to the square of the maximum gain the array can produce. As a consequence, for forward scattering in the limiting case of zero spacing between the elements,A_{sr} = n^{4}.     

Shaped-beam synthesis of nonuniformly spaced linear arrays

A method which involves only simple calculations is used to design nonuniformly spaced linear arrays for shaped-beam patterns. The method is based on Gaussian quadrature. The examples given show that it is possible to obtain patterns which compare favorably with those of uniformly spaced array methods. This is accomplished by using fewer elements, smaller overall length, and lower variation of element current amplitudes.     

Power pattern synthesis of reconfigurable conformal arrays with near-field constraints

A conformal array power pattern synthesis technique is presented which makes it possible to take into account near-field constraints and to reconfigure the radiated pattern by controlling only the phases of the excitation coefficients. Far-field pattern specifications are given by masks while near-field constraints are given by prescribing the maximum allowable field intensity at points arbitrarily located in a given near-field region. The amplitude of the excitations, common to all radiated beams, and the phases corresponding to each one are obtained as a result of the synthesis algorithm.