多层微带贴片天线单元和阵列设计

该文通过结合经验公式和全波分析法,设计了一种电容补偿双层贴片、四层介质的微带贴片天线单元,该单元天线在频率为995～1125MHz的范围内,在驻波比SWR1.5的情况下,相对阻抗带宽达到12.26％的工程要求。此外,该文给出由该单元天线组成的216天线阵以及天线阵的驻波比的实测结果,最后给出天线阵的各单元排列方式和单元之间的互耦特性曲线的实测结果。     

Genetic design of linear antenna arrays

Discusses a way to optimize both the topology and the numerical parameters of an antenna design. The approach relies on an “antenna language” to define how antennas are constructed, and a genetic algorithm to create new designs using this language. The grammatical rules of a language can be very vague or very specific, depending on the purpose of the designer. With a vague grammar, genetic algorithms search a very large design space, and can occasionally find unexpected solutions to a design problem. Other times, they completely fail to find a reasonable solution because of the vastness of the search space. In this case, including knowledge about the problem into the grammar narrows the search to a region expected to yield good results. This yields more conventional design solutions that usually perform reasonably well. In an example, two languages were used to design a linear antenna array. The general language allowed a wide variety of designs, while the Yagi-log language confined the search to topologies known to perform well. The performance of the antennas produced by both languages was superior to that of a conventional log-periodic design. Further, the Yagi-log design was more fit than the unconventional design from the general language, illustrating the benefits of including knowledge in the grammar     

分形模型在天线设计中的程序自动化构建

为了实现各种复杂分形模型的程序自动化建模,节约建模时间,文中利用Hfss-MatlabApi数据包,通过在MATLAB软件中编写程序运行生成VB脚本,实现了诸如分形等复杂模型在电磁仿真软件中的自动化构建,且此方法灵活高效。     

Fractal design of multiband and low side-lobe arrays

Most array factor design techniques are highly dependent on the operating wavelength. In this paper, a novel technique based on fractal structures is described for multiband operation. The analysis is focused in two different approaches: the fractal spatial arrangement of array elements and the fractal design of array factors. Although the patterns of fractal arrays show some interesting similarity properties at several bands, the directivity is not held constant through the bands. Nevertheless, such structures have been shown to be useful for designing low side-lobe arrays with equally weighted current elements. On the other hand, the fractal array factors presented do keep the same shape at several bands because they are designed as self-similar curves. The arrays that would synthesize such patterns present a characteristic power-law current distribution analogous to the spectral distribution of the bandlimited fractal Weierstrass function     

Novel analysis and design approaches of the planar antenna arrays

New approaches for the determination of the radiation characteristics of planar arrays are proposed. Conventionally, the best compromise directivity-side lobes level is achieved using Dolf-Chebyshev amplitude distribution. However, classical distribution forms present disadvantages in calculation time, possibility in analyzing larger arrays and the array factor is only optimum in the two principle planes. To overcome these problems, the excitation amplitudes are written under the modal form. The obtained radiated fields compared with measurement results validate the technique. It is also shown that square arrays provide improved performances from point of view of directivity compared to those of rectangular arrays with comparable size. However, above specific array size, the directivity saturates. For this, another modification of the array factor of Chebyshev square array is proposed. The modification preserves the radiation pattern configuration (same number of null radiation directions and sidelobes) and improves both directivity and side lobe levels. Analytical expressions of the array factor, the directivity, maximum half-power beamwidth, and the maximum spacing between elements have been derived. It has been shown that the use of this new technique results in an improved directivity with respect to the classical Chebyshev for a square arrays identical in size, element spacing, direction of the main lobe and side lobes level.     

Practical feed network design for antenna arrays

Computational procedures have recently been developed which accurately determine the excitation (including mutual coupling effects) at each element of a closely spaced array enabling it to perform in some desired manner. A procedure for designing a transmission-line feed network capable of realizing these required excitations is described. The result is a narrow-band feed system composed simply of a transmission line together with a small number of stubs. A comparison between theoretical and experimental results is given.     

Modeling and design of electromagnetically coupled microstrip-patchantennas and antenna arrays

This work is an effort to investigate and derive a simple equivalent-circuit model to represent an electromagnetically coupled microstrip-patch antenna. A simplified theory is developed, based on the broadside-coupled lines and improved-transmission-line methods, to provide for the practical design of such antennas without involving complicated, time-consuming, difficult numerical methods. A number of sample patches are designed, made, and tested to verify the theory. These patches are also incorporated into an array, to evaluate their performance in an array environment     

The design of antenna arrays with tapered sidelobe heights

Arrays for many radar and sonar applications have customarily been designed for equal sidelobe levels. This is, perhaps, as much due to the convenience of the analytical Dolph-Chebyshev technique as to any specific requirement. Using a simple adaptation of a previously reported numerical technique for symmetrical arrays, designs can be obtained whose directional response has a specified taper on the envelope containing the sidelobes. The method is applicable to both sum and difference patterns for both line and planar arrays. However, there seems to be little to be gained by this procedure except in the case when the outer sideiobes are to be more severely controlled.     

A mathematical theory of antenna arrays with randomly spaced elements

Various probabilistic properties of a large antenna array with randomly spaced elements have been studied. It is found that for almost all cases of practical interest the required number of elements is closely related to the desired sidelobe level and is almost independent of the aperture dimension, the resolution (or the beamwidth) depends mainly on the aperture dimension, and the directive gain is proportional to the number of elements used if the average spacing is large. As a consequence the number of elements required is considerably less than that with uniform spacings. Starting with a given number of elements and a given aperture size, it is possible to improve the resolution by a factor of ten, a hundred, or more by spreading these elements over a larger aperture with little risk in obtaining a much higher sidelobe level and a lower directive gain. In fact, this method offers a solution which is optimum in a certain statistical sense, i.e., all sidelobes are of equal level with equal probability. In addition, this analysis also gives a simple estimate of the sidelobe level of most nonuniformly spaced antenna arrays. In a number of such arrays studied by various investigators with high speed computers, the agreement found is remarkable.     

A short design method for nonuniformly spaced antenna arrays

A design method is presented for symmetrical nonuniformly spaced linear arrays. Element positions are easily found if one element position is given. Instead of restricting the cosine functions in the array factor, a constraint is placed upon the arguments of the cosine functions. For an array of2Nelements, one obtainsN - 1equations inNunknowns, which can be solved sequentially instead of simultaneously. The array designs are not optimum, but the simplicity of this method will allow arrays to be designed quickly. These arrays could inturn be used as preliminary steps toward more rigorous studies.     

Parameter study and design of wide-band widescan dual-polarizedtapered slot antenna arrays

A parameter study of dual-polarized tapered slot antenna (TSA) arrays shows the key features that affect the wide-band and widescan performance of these arrays. The overall performance can be optimized by judiciously choosing a combination of parameters. In particular, it is found that smaller circular slot cavities terminating the bilateral slotline improve the performance near the low end of the operating band, especially when scanning in the H-plane. The opening rate of the tapered slotline mainly determines the mid-band performance and it is possible to choose an opening rate to obtain balanced overall performance in the mid-band. A longer tapered slotline is shown to increase the bandwidth, especially in the lower end of the operating band. Finally, it is shown that the H-plane anomalies are affected by the array element spacing. A design example demonstrates that the results from the parameter study can be used to design a dual-polarized TSA array with about 4.5:1 bandwidth for a scan volume of not less than &thetas;=45° from broadside in all planes     

随机错位子阵阵列天线及其优化设计

针对大型的二维平面阵列天线,将随机布阵的概念应用于子阵布阵中,提出基于子阵的随机错位布阵方式,并采用二进制粒子群算法对随机错位子阵的错位方式进行了优化.仿真结果表明:采用随机错位子阵布阵方式,通过粒子群算法优化后,平面阵列天线可以在扫描范围内得到较低的旁瓣,避免了栅瓣的出现.     

线天线及天线阵的时域传输线矩阵法分析

本文针对线天线及天线阵的频域分析方法的缺点，首次将时域传输线矩阵法应用到这一领域，应用时域ＴＬＭ法时，只需经过一次运逄就可以得到天线及天线阵各个区域的场特性，本文计算方法及数值结果表明，运用时域ＴＬＭ法可以对各种大型天线阵进行有效的分析，便于工程应用。     

Broad-band array design using the asymptotic theory of unequallyspaced arrays

The problem of designing broadband linear arrays of omnidirectional sensors is addressed. Attention is restricted to the case of shaded delay-and-sum beamforming. Broadbanding is here defined to mean that the beam-pattern function has little or no frequency dependence of peak response, main-lobe width, plateau sidelobe level, and sinespace separation between the main lobe and the plateau sidelobe. The asymptotic theory of unequally spaced arrays is used to derive relationships between beam-pattern properties and array properties. These relationships are used to translate beam-pattern requirements into functional requirements on sensor spacings and amplitude shadings. The functional requirements are then used to derive a broadband array design. In addition to the design equations, the asymptotic theory is used to derive equations for main-lobe level, sidelobe level, beamwidth, and signal-to-noise ratio (SNR) gain in isotropic noise. A specific example is presented to clarify the concepts and verify that the design procedure actually works     

复射线理论应用于天线一体化设计

分析自由空间天线辐射特性的方法已十分成熟,如口径场积分法、平面波谱积分法等,它们大都是行之有效的,但要求对天线及天线罩进行一体化分析时,现有的经典方法往往不能迅速而准确地给出解答,如果用复射线理论这一新方法则可以对某些问题圆满地给出结果.根据复射线理论,利用复源点远场具有的高斯波束特性,无论是在远区或是近轴区域内,复源点场和高斯函数有很接近的相同分布,理论上论证了对于具有高斯波束分布的口径场可以用复源点场来近似模拟.     

Synthesis of linear antenna arrays

Synthesis of antenna arrays employing theL_{2}-norm as well as theL_{infty}-norm is discussed. The approximation in theL_{infty}-norm is obtained making use of Lawson's algorithm. A general iterative perturbation technique has been evolved for pattern synthesis for the case when the antenna currents alone are varied as web as for the case when both the antenna currents and the element positions are simultaneously varied. A few illustrative examples are given. The convergence of the iteration and the uniqueness of the solution are discussed.     

On the empirical optimization of antenna arrays

Empirical optimization is an algorithm for the optimization of antenna array performance under realistic conditions, accounting for the effects of mutual coupling and scattering between the elements of the array and the nearby environment. The algorithm can synthesize optimum element spacings and optimum element excitations. It is applicable to arrays of various element types having arbitrary configurations, including phased arrays, conformal arrays and nonuniformly spaced arrays. The method is based on measured or calculated element-pattern data, and proceeds in an iterative fashion to the optimum design. A novel method is presented in which the admittance matrix representing an antenna array, consisting of both active and passive elements, is extracted from the array's element-pattern data. The admittance-matrix formulation incorporated into the empirical optimization algorithm enables optimization of the location of both passive and active elements. The methods also provide data for a linear approximation of coupling as a function of (nonuniform) element locations, and for calculation of element scan impedances. Computational and experimental results are presented that demonstrate the rapid convergence and effectiveness of empirical optimization in achieving realistic antenna array performance optimization.