Synthesis Of Circular Arrays Research Articles

Synthesis of circular arrays with sidelobes of individually arbitrary levels

Synthesis of circular antenna arrays to have individually arbitrary sidelobe levels, is investigated. Circular arrays are synthesized by applying a transformation to previously designed linear arrays. The antennas of the circular arrays are considered either isotropic or directive. The synthesized patterns are steerable without any distortion. Some examples are brought to verify the effectiveness of the proposed procedure for both isotropic and directive antennas.

Synthesis of Circular Array Antenna for Sidelobe Level and Aperture Size Control Using Flower Pollination Algorithm

Sidelobe level suppression is a major problem in circular array antenna (CAA) synthesis. Many conventional numerical techniques are proposed to achieve this which are time consuming and often fail to handle multimodal problems. In this paper, a method of circular array synthesis using nature inspired flower pollination algorithm (FPA) is proposed. The synthesis technique considered here adapts one and two degrees of freedom, namely, amplitude only and amplitude spacing. The effectiveness of the FPA is studied by comparing the results with genetic algorithm (GA) and uniform circular array antenna (UCAA) with uniform spacing. Also the effect of additional degree of freedom on the aperture size and the computational time is analyzed. A relative side lobe level (SLL) of −25 dB is achieved using the algorithm under both no beam scanning (0°) and beam scanning (15°) conditions for 20 and 40 elements of CAA.

Pattern Synthesis of Circular Array Antenna by Improved Genetic Algorithm

Propose an application of multi-objective genetic algorithm (GA) for pattern synthesis of circular arrays with equally spaced isotropic elements. Aim at reduce the side-lobe level and deep the null of array antenna patterns, adopt improved real-coded genetic algorithm, which modify the crossover operator and mutation operator compare with standard GA, both the crossover and mutation probability adjustable in accordance with the generation numbers, in the final, the approach for antenna pattern synthesis can suppress interferences by deep the nulls at directions of interfering sources and placing main beam in direction of desired signal by controlling amplitude weights. Numerical results show effectiveness of the procedure proposed.

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 at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -band, was measured and reasonable agreement with theory was obtained.

Pattern synthesis of circular arrays in a moving medium

Based on a modified expression for the radiation field of a circular array in a moving medium, pattern synthesis is performed for medium motion both in the direction of and parallel to the main beam. It is shown that medium motion, even considering only first-order effects, changes the synthesized patterns significantly. The required excitation amplitudes and phases for the proper synthesis of a 21-element circular array to yield a cosine-square pattern in a moving medium are given.

Pattern synthesis of circular arrays with many directive elements

A method for synthesizing the radiation pattern of a circular array with directive elements is presented. The required excitations are determined from an explicit formula which requires no reduction or inversion of matrices. It is particularly useful for designing large circular arrays with many elements.

Discussion on “Optimum directional pattern synthesis of circular arrays”

Discussion on “Optimum directional pattern synthesis of circular arrays”

Optimum directional pattern synthesis of circular arrays

An attempt is made to deduce rules for designing circular arrays which produce desired directional patterns. The paper considers circular arrays consisting of equally spaced radiators distributed on the whole circumference or on a coherent part of it.First the general relation between the desired far-field amplitude distribution and the complex input amplitudes of the individual radiators is deduced. The results can be written as a linear system of equations. Its order depends only on the ratio of diameter to wavelength. This form permits a clear and simple numerical treatment of the task by means of a digital computer. Additionally, practical hints are given for the realization of the array feed function. There by it is found that a problem of the directional pattern synthesis can be reduced to a synthesis of linear networks.In a second step the actual optimizing problem is dealt with. It is intended to find, for a given ratio of circular array diameter to wavelength, the design for which the maximum array gain is obtainable with simultaneous maximum attenuation of side-lobes. The result shows that there exists a theoretical limit for the obtainable attenuation of the dominating side-lobe, a limitation which is independent of the ratio of circular array diameter to wavelength. In the investigated case this boundary is at −26-43 dB. The array gain increases in a nearly linear mannerwith the indicated ratio and there seems to be no theoretical limit to any desired increase of the gain.All considerations are valid for transmission and for reception. The correctness of the treatment has been confirmed by a laboratory experiment.