G. S. N. Raju

Accelerated particle swarm optimization of pattern synthesis

Pattern synthesis of arrays is one of the most important problems in satellite and radar applications. The synthesis is conventionally carried out using standard methods like Chebyshev and Taylor etc. However in the present work synthesis is optimized by using state of art algorithm namely Accelerated Particle Swarm Optimization (APSO). Using this algorithm the required amplitude and phase distributions are computed to generate low sidelobe narrow beam patterns. Small and large arrays are designed in this work.

Radiation patterns of arbitrarily oriented radiating elements

The radiation patterns of horizontal and vertical dipoles have been reported in the literature. These results are used in the analysis and design of arrays of parallel vertical elements and collinear elements. However no information is available for the arbitrarily oriented elements. The element patterns of such elements are derived from the concept of the vector magnetic potential and co-ordinate transformation. From the derived expressions, the radiation patterns are computed and presented both in linear and polar forms. It is found, from these results, that the orientation of the element changes the main beam direction. Arrays of such elements with arbitrary orientation are considered and the computed results of the radiation patterns are presented. Different possible current distributions for the arbitrarily oriented elements are introduced for the estimation of the radiation patterns. The results of constant and sinusoidal distributions are compared.

Synthesis of Sector Beams from Array Antennas Using Real Coded Genetic Algorithm

In this paper, flat top far field radiation patterns known as sector beams are generated from linear arrays using Real Coded Genetic Algorithm. For all specified angular sectors, the pattern synthesis is carried out. The synthesis involves the determination of complex excitation functions for linear array for different beam widths. These patterns are numerically generated with the designed excitation levels. Controlling the ripples in the trade—in region maintaining the side lobe levels in the acceptable limits in the trade—off region is made possible in the present work.

Design of Linear and Circular Arrays Using Natural Search Algorithms for Generation of Low Side Lobe Patterns

Arrays are designed conventionally using standard distribution functions and also using age old techniques like Woodward, Taylor, etc. It is well known that beam width and side lobe are conflicting and is involved in generating a compromise between these two for deserved radiation characteristics. In this paper, design of linear and circular arrays with such optimization is considered. The optimization is carried using the state-of-the-art natural search algorithms like Cuckoo Search Algorithm. Simulation is carried out with the objective of side lobe level (SLL) suppression considering beam width (BW) constraint. These results are compared with that of Accelerated particle swarm optimization.

Analysis of rectangular waveguide coupled on the effect of waveguide dimensions in common narrow wall

Waveguide slot couplers of present interest consist of longitudinal slot in the common narrow wall of two rectangular waveguides. The concept of self-reaction and discontinuity in model current are used for the analysis. The slots are designed in such a way that they are operated at resonance. It is an established fact that coupling depends on slot dimensions and its parameters along with frequency variations. But it also depends on the waveguide dimensions with which the coupler is fabricated. No data is available in literature on such dependence and effects. In view of this investigations are carried out to obtain such vital data. The effects of waveguide dimensions are consolidated in the present paper.

Generation of low sidelobe beams using Taylor's method and genetic algorithm

Various types of non isotropic radiating elements are used in an array in order to achieve the desired characteristics. The lower the sidelobe levels the more is the directivity. Array synthesis is used to obtain the desired pattern and to find the relative element excitations to achieve the desired characteristics. Among the synthesis methods for the generation of the symmetrical patterns the Taylors synthesis is chosen because in this synthesis there is flexibility to fix the sidelobe level and the number of sidelobes having the same sidelobe level. An attempt is also made to use GA for the synthesis of the amplitude excitation coefficients to yield a desired radiation pattern of a linear antenna array with reduced sidelobes and the patterns are compared with the results obtained using Taylors method. By decreasing the sidelobe levels and beamwidth, pencil beams can be produced which are used for the tracking purposes.

Array pattern synthesis using flower pollination algorithm

In this paper, Synthesis of sum patterns to generate narrow beams with reduced sidelobes using Flower Pollination Algorithm is presented. The array design is first formulated as an optimization problem with the goal of reducing peak sidelobe level to −50dB. The objective of the FPA algorithm is to determine the optimized set of amplitude excitation coefficients to obtain the desired pattern. The patterns are numerically computed for different array lengths and the results obtained are compared with those of conventional method in the present paper. These low side lobe patterns are useful to overcome EMI problems in radar system.

Sidelobe level reduction in linear antenna array synthesis using Cuckoo Search & Accelerated Particle Swarm algorithms

Array pattern synthesis is one of the most important problems in communication and radar applications. The synthesis is usually carried out by controlling amplitude and phase levels (or) element spacing functions of the array. Although, uniform linear arrays cost effective in terms of sources it is not preferred due to high presence of high first side lobe levels. For point to the point communications, and high angular resolutions radars, it is essential to generate low side lobe narrow beams. In view of these facts, a linear array is considered in the present work and it is optimally designed using CSA & APSO algorithms. The desired amplitude levels are evaluated using the algorithm with element spacing d=0.50. The main objective of this work is to minimize the sidelobe level with a constraint on beam width.

Patterns of thinned arrays

Array antennas have become very popular in Communication and Radar applications. Due to their improved characteristics linear arrays where the elements are distributed uniformly are thoroughly investigated by different authors. However, non-uniform arrays are not well focused so far. In view of these facts intensive studies are carried out to generate sector beams using non-uniformly spaced arrays. Focus is made to thin the arrays to produce optimized patterns. The concept of thinning leads to the design of arrays economically. The computed radiation patterns for small and large arrays are presented in u domain.

Realization of amplitude distribution function from slot-fed waveguide junctions for desired beams

Low sidelobe radiation patterns are required to prevent EMI in the receiving systems. Such patterns are generated with the use of highly tapered amplitude distributions. In order to realize a defined taper an array of waveguide junctions is designed. The junctions considered in the array are suitable for producing the desired polarized fields without creating EMI problems.