Planar Circular Array Research Articles

Arbitrary footprint patterns from planar arrayswithcomplex excitations

Elliott and Stern's (1990) method for synthesising shaped patterns using a circular or elliptical planar aperture or array with a complex excitation distribution is generalised to allow the synthesis of footprints of arbitrary shape. The use of complex excitations allows a given footprint to be synthesised using a smaller array than with real excitations. The procedure is illustrated by synthesising a square footprint using an array with a rectangular grid.

Null steering in planar arrays by controlling only current amplitudes using genetic algorithms

In this paper, a technique to steer the array nulls for planar arrays by controlling only the excitation current amplitudes based on genetic algorithms is investigated. The proposed technique is found to be capable of steering the array nulls to the prescribed interference directions with prescribed null depth and simultaneous sidelobe level minimization. In addition, the technique is simple, easily implemented, and versatile compared with other analytic methods for this problem. To verify the validity of the technique, illustrative examples for both rectangular and circular planar arrays are demonstrated. Numerical results show that for planar arrays, even with large elements for cases of a large number of interferences, the proposed technique does succeed in steering the array nulls with satisfactory nulling performance, as desired. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 97–103, 1997.

A flexible array synthesis method using quadratic programming

A highly flexible synthesis method for an arbitrary array is proposed to best approximate a desired array pattern in a minimum-mean-square-error sense. The basic idea of the technique is to form a quadratic program with its cost function given by the mean-square error between the array response and a properly selected pattern described by a known mathematical function. This quadratic program can be a constrained or unconstrained optimization problem depending on the requirements of the desired array pattern. In formulating the quadratic program, no assumption has been made on the gain/phase response or characteristics of the individual array elements. Therefore, one can synthesize an array of arbitrary shape to any appropriate pattern with the characteristic of the array elements taken into consideration as long as one is able to model the array accurately. The proposed method is used to synthesize arrays of different shapes, linear as well as planar arrays (including rectangular and circular planar arrays), using a Chebyshev polynomial or zero function as a design template, to illustrate the feasibility of the proposed method. >

Array pattern control and synthesis

Antenna array distributions and their associated patterns are now designed on physical principles, based on placement of zeros of the array polynomial. An overview of the synthesis processes is given. Robust and low Q distributions for linear arrays and circular planar arrays that provide variable sidelobe level pencil beam patterns are treated in detail. Associated difference patterns are included. Individual sidelobes or groups of sidelobes may be adjusted in level. The same technique allows synthesis of an efficient shaped beam, with or without sidelobe adjustment. The ultimate pencil beam array, the superdirective array, is evaluated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Scanning of cosecant beams generated by a tilted planar array of nonisotropic radiators

A method of scanning a one-dimensional shaped pattern generated by a tilted circular planar array of nonisotropic elements is presented. A method of synthesis of phase function for a desired cosecant pattern and specified amplitude distribution for excitation of the elements of the array is presented. The phase distribution required in the perpendicular direction for retaining the beam shape in the scanned plane is determined. Computed results on the phase distribution and radiation pattern are presented. The appropriate correction is applied to get a better agreement between the realized and desired patterns in this scanned position of the beam.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Shaped patterns from a continuous planar aperture distribution

A pattern synthesis procedure is developed for a planar aperture with a circular boundary. A (Ø-symmetric continuous distribution is assumed and required to produce a flat-topped beam with controlled ripple, surrounded by ring side lobes of controlled height. With M filled-in nulls in the shaped region, there are 2M solutions for the aperture distribution. Sampling can yield the excitation of a circular grid planar array. Linear stretching extends the results to an elliptical boundary.

Pattern synthesis of spherical circular array antenna by conjugate gradient method

AbstractIn this paper, the spherical circular array antenna pattern is synthesized and the results are compared with the planar circular array. Since the pattern function is complicated, analysis of pattern syntheses of solid surface arrays such as the spherical array becomes difficult. Herein, pattern synthesis is done numerically by minimizing the mean‐square‐error between the desired and synthesized power patterns using the conjugate gradient method. This method is found to be effective in the pattern synthesis of the spherical array. Calculations show that when elements with sharp patterns are used in the array, phase control is more advantageous in practice than amplitude control. Also shown here is the excitation method by which a circularly polarized pattern along the apex direction can be obtained when turnstile antennas are arrayed conformally on the sphere. With this excitation method, the pattern is synthesized and the axial ratio of polarization for main‐beam scan degrades less for spherical than planar array. Furthermore, for spherical array the axial ratio can be improved by placing the elements on a conducting sphere.

Array design for a specified pattern by matrix methods

A new method is presented for designing arrays of parallel wire antennas. The method relates a desired pattern with required feed voltages such that mutual coupling is taken into account in the design procedure. The technique uses matrix methods together with results of the "Method of Moments" to determine the self- and mutual impedances and the required excitations. The design method can be applied to circular, elliptical, and other planar arrays although attention is restricted here to linear arrays. The feed points and the array geometry must be specified.

Planar arrays with unequally spaced elements

The application of the optimization technique known as dynamic programming to the design of thinned planar arrays with unequally spaced elements is described. Two different approaches were investigated. In one method the planar aperture was considered to consist of a number of concentric ring arrays and dynamic programming was applied to determining the radii of the rings which yielded radiation patterns with the minimum peak side-lobe. In the other method the planar array was divided into an even number of equal sectors with elements identically located in each sector. Both methods were selected to avoid excessive calculation times. With the aid of large digital computers designs were obtained and radiation patterns computed for 40λ diameter circular planar arrays and for various degrees of thinning. The results differed from those obtained by other unequally spaced array design methods in that the side-lobes of the radiation pattern tended to decrease with increasing distance from the main beam.

Space tapaering of linear and planar arrays

The recent activity in electronically scanned arrays has stimulated interest in means of reducing both the quantities of elements required for a given size aperture and the number of different types of transmitters which would be necessary in an array using an illumination taper. One method of doing this is presented in this paper. The conventional amplitude tapered array is simulated by varying the spacing of equally excited elements, hence the name "space tapering." Space tapered arrays with predictable gains, beamwidths, and sidelobe levels can readily be designed using graphical techniques and simple mathematics. Reduction in the number of elements of from 50 to 90 per cent for moderate and large size planar arrays are possible while retaining good pattern characteristics. Although only linear and circular planar arrays are discussed, the technique can be applied to other planar and three dimensional arrays.