Optimum distribution over a circular aperture for best mean-square approximation to a given radiation pattern

The distribution over a cicular aperture in a ground plane that produces the best mean-square approximation to a specified radiation pattern is derived subject to constraints on the mean-square aperture field strength. The result is derived in terms of the functions most natural for a least square fit: the eigenfunctions of a finite (circular) two-dimensional Fourier transform.     

Radiation pattern synthesis for circular aperture horn antennas

A set of radiation pattern functions, suitable for synthesis of radiation patterns from circular aperture horn antennas, is obtained by assuming an aperture distribution consisting of the fields of cylindrical waveguide modes. A technique is presented for using a linear combination of the radiation pattern functions to approximate a desired radiation pattern. Linear combinations of the radiation pattern functions resulting in maximum secondary gain, when used to illuminate a paraboloidal antenna, are obtained empirically. Using spherical wave theory, maximum performance theoretically obtainable from an antenna is derived as a function of the aperture size of the feed system; the feed efficiency resulting from these theoretical limits on performance is compared to the feed efficiency of patterns obtainable from circular aperture horn antennas, and to experimental results of attempts to realize optimum circular aperture horn patterns.     

Synthesis of offset dual reflector antennas transforming a given feed illumination pattern into a specified aperture distribution

The problem of transforming a given primary feed pattern into a desired aperture field distribution through two reflections by an offset dual reflector system is investigated using the concepts of geometrical optics. A numerically rigorous solution for the reflector surfaces is developed which realizes an exact aperture phase distribution and an aperture amplitude distribution that is accurate to within an arbitrarily small numerical tolerance. However, this procedure does not always yield a smooth solution, i.e., the reflector surfaces thus realized may not be continuous or their slopes may vary too rapidly. In the event of nonexistence of a numerically rigorous smooth solution, an approximate solution that enforces the smoothness of the reflector surfaces can be obtained. In the approximate solution, only the requirement for the aperture amplitude distribution is relaxed, and the condition on the aperture phase distribution is continued to be satisfied exactly.     

Synthesis of amplitude-phase distribution and shape of a planarantenna aperture for a given power pattern

The problem of synthesis of an optimum shape of a planar aperture and optimum amplitude-phase distribution over this aperture corresponding to a given power pattern is considered. The functional, which ensures minimization of the mean-square deflection of the magnitudes of the given pattern and of the synthesized one in the area of the main lobe and minimization of the sidelobes, is used as the optimization criterion. The problem of determination of the optimum functions of the shape or a planar aperture and of the excitation over this aperture is reduced to the determination of solution of the system of two nonlinear integral equations. The numerical algorithms of solution of these equations are based on utilization of the method of successive approximations and the Newton-Kantorovich method. The numerical results of synthesis of partial power patterns with rectangular and triangular outlines are presented     

Ultrawide-band modeling of transient radiation from aperture antennas

A new method for the numerical calculation of transient field radiated through aperture-type antennas (slot, open-ended waveguide, and horn) is described. The finite-difference time-domain method is applied for the near-field prediction in the close surrounding of the antenna and a proper data-fitting procedure of the aperture field, involving interpolating functions with separation of space- and time dependence, permits: 1) to calculate "off-line" the radiated field without the need to store a great amount of data; 2) to avoid, in the case of far field, the numerical evaluation of radiation integral; and 3) to obtain approximate far field formulas which are still separable with regard to space and time. The method enables a full data reusability in calculation of field pattern over a wide angular range at a same time, or of the transient response at fixed observation points.     

New technique for efficient pattern computation of aperture and reflector antennas

A new and efficient technique for computing secondary patterns of antennas with known aperture distributions is described. The method is extendable to parabolic reflector antennas with given surface current distribution. The fast Fourier transform (f.f.t.) algorithm is used to compute the coefficients of expansion of a series representing the radiation pattern.     

Fast synthesis of aperture distributions for contoured beam reflector antennas

The use of a gradient function method to optimise aperture fields for contoured beam reflector antennas is shown to be efficient when compared with other approaches. A key feature of the method is that an analytical expression is used to modify the aperture distributions in each iteration.<>     

Antenna pattern synthesis using a relaxation method: application to printed antennas

An antenna pattern synthesis method based on a relaxation technique is proposed. The radiation pattern of the elementary source and the interelement spacings are taken into account. Two examples of linear printed arrays are computed: sector pattern and directive broadside pattern.     

Fast radiation pattern evaluation for lens and reflector antennas

A novel algorithm referred to as the fast physical optics (FPO) for computing the radiation patterns of nonplanar aperture antennas over a range of observation angles is presented. The computation is performed in the framework of the conventional physical optics approximation appropriate for the high frequency regime. The proposed algorithm is directly applicable to reflector and lens antennas as well as to radomes. The method comprises two steps. First, a decomposition of the aperture into subdomains and computation of the pertinent radiation pattern of each subdomain. Second, interpolation, phase-correction and aggregation of the radiation patterns into the final pattern of the whole aperture. A multilevel algorithm is formulated via a recursive application of the domain decomposition and aggregation steps. The computational structure of the multilevel algorithm resembles that of the FFT while avoiding its limitations.     

Radiation pattern synthesis of planar antennas using the iterative sampling method

A synthesis method is presented for determining an excitation of an arbitrary (but fixed) planar source configuration. The desired radiation pattern is specified over all or part of the visible region. It may have multiple and/or shaped main beams with low sidelobes. The iterative sampling method is used to find an excitation of the source which yields a radiation pattern that approximates the desired pattern to within a specified tolerance. In this paper the method is used to calculate excitations for line sources, linear arrays (equally and unequally spaced), rectangular apertures, rectangular arrays (arbitrary spacing grid), and circular apertures. Examples using these sources to form patterns with shaped main beams, multiple main beams, shaped sidelobe levels, and combinations thereof are given.     

Phase synthesis of conformal array antennas

A new phase synthesis method for planar and conformal arrays is presented. The method is based on approximate linearized equations for small phase changes in the excitations, which can be determined by the least-squares method and used iteratively to obtain the final solutions for the excitation phases. Several different kinds of contoured beams can be used in the same array by using only phase shifters in the elements, as demonstrated in the calculated synthesis examples     

Synthesis of a slot radiator with a given radiation pattern

Synthesis of a slot cylindrical radiator with a given radiation pattern is studied. For a Gaussian pattern, the phenomenon of superdirectivity is analyzed and the parameters of the radiator providing for the optimal spread in the orders of the amplitudes of the currents on slots are estimated.     

Legendre distribution for radiation pattern

The electromagnetic field from a group of radiators depends upon amplitude and phase distribution of the source. The distributions, which are of considerable interest in the mathematical theory of linear arrays, are the Chebyshev, uniform, triangular, and binomial. The radiation patterns of these distributions are highly directive. The Legendre distribution is considered     

Improvements to nonnumerical methods for calculating the transient behaviour of linear and aperture antennas

The time-domain response of linear and aperture antennas is analyzed. The results are based on models which have proven to be satisfactory for sinusoidal steady-state analysis. The calculated results correlate the physical parameters of both transmitting and receiving structures with the time-domain characterization of their response. The methods presented herein are useful to provide simple yet powerful alternatives to numerical techniques for the solution of transient radiation problems. The time-domain impulse response is calculated for thin cylindrical dipoles and the aperture formed by two semi-infinite parallel planes. Comparison between experiment and theory is provided. Analytical expressions are derived which characterize the response to excitations that are bandlimited in a manner dictated by the models, e.g., thin wire approximation and TEM mode excitation limitations.     

一种阵列天线的约束最优化综合方法

为同时满足对方向性系数,阵列效率,方向图旁瓣等参数的要求,提出了一种效率和旁瓣约束下的最优方向性综合法.该方法适用于任意的阵列形式,以最大化阵列方向性系数为目标,通过对加权向量的二次约束控制了阵列效率,并采用迭代的方法满足了方向图旁瓣的要求,实现了阵列效率和旁瓣约束下的方向性系数最优化.对多种阵列在不同要求下的仿真结果以及5元圆阵列的实验结果表明了这种方法的有效性和灵活性.     

Phase theory of radiation pattern

The conventional requirements on the antenna are reviewed. The importance of the phase pattern of the antenna in modern science and technology is pointed out. Under such a background, the problems concerning the phase characteristic of the radiation pattern and the current distribution of the antenna aperture are attempted to be systematized on the basis of previous works, namely, the phase reference point, the transformation of the radiation patterns corresponding to different phase reference points of an antenna, the null level and the phase difference between the adjacent lobes, and the resolution of current distribution of a linear source, are summarized and discussed. The general condition of the equiphase lobe and the condition of the symmetric lobe of a linear source are proposed and proved theoretically. Some theorems are proposed by induction from the above and the overall discussion is termed the phase theory of radiation pattern.     

A slot design for uniform aperture field distribution insingle-layered radial line slot antennas

A single-layered radial line slot antenna (RLSA) is proposed for a direct broadcast from a satellite (DBS) subscriber antenna. It utilizes a radially outward-traveling wave and the aperture field is intolerably tapered if the uniform slots are used. Two novel techniques are applied. First, the slot design for uniform aperture field distribution is introduced. Second, the radial line is terminated by a matching spiral, in place of a dummy load. It suppresses reflection and radiates all the residual power in circular polarization. For a model antenna of 600-mm diameter, the efficiency of 65% is observed     

Improved radiation pattern performance of Gaussian profiled horn antennas

A new horn antenna profile is presented. This new profile based on Gaussian techniques offers the best solution when the requirements related to the radiation pattern are very stringent. Short-horn antennas with high-conversion efficiency to a fundamental Gaussian beam, and therefore, very low sidelobe and cross-pol levels in a wide-frequency band, could be obtained by using the design technique presented here. Once the theoretical principles of the Gaussian profiled horn antennas (GPHA) are presented, some other possibilities involving Gaussian profiles are studied and compared with their conventional counterparts. Finally, as an example of the design technique proposed, a particular design of a GPHA for HISPASAT 1C and now also valid for the new HISPASAT 1D satellite is presented, showing the excellent agreement between the theoretical and experimental results.     

基于改进粒子群算法的天线方向图综合技术

针对基本粒子群算法的早熟收敛、易收敛于局部极值的特点，提出一种改进的粒子群优化算法，采用对全局最佳微扰和惯性权重跳变阈值的设置改善了算法的优化速度和收敛精度。经过对一系列测试函数的计算，证明该方法具有良好的优化效果。最后，给出了该方法应用于阵列天线方向图综合中的模型和仿真实例。