G. K. Mahanti

Synthesis of Thinned Linear Antenna Arrays with Fixed Sidelobe Level Using Real-Coded Genetic Algorithm

In this paper, we propose an optimization method based on real-coded genetic algorithm (GA) with elitist strategy for thinning a large linear array of uniformly excited isotropic antennas to yield the maximum relative sidelobe level (SLL) equal to or below a fixed level. The percentage of thinning is always kept equal to or above a fixed value. Two examples have been proposed and solved with different objectives and with different value of percentage of thinning that will produce nearly the same sidelobe level. Directivities of the thinned arrays are found out and simulation results of different problems are also compared with published results to illustrate the effectiveness of the proposed method.

Phase-Only and Amplitude-Phase Only Synthesis of Dual-Beam Pattern Linear Antenna Arrays Using Floating-Point Genetic Algorithms

In this paper, we present a comparison study between phase-only and amplitude-phase synthesis of symmetrical dual-pattern linear antenna arrays using floating-point or real-valued genetic algorithms (GA). Examples include a sum pattern and a sector beam pattern. In the former, phase is only optimized with predetermined Gaussian amplitude distribution of fixed dynamic range ratio (|amax/amin|) and in the latter, both are optimized with less dynamic range ratio than the former and yet share a common amplitude distribution.

Comparative Performance of Gravitational Search Algorithm and Modified Particle Swarm Optimization Algorithm for Synthesis of Thinned Scanned Concentric Ring Array Antenna

Scanning a planar array in the x-z plane directs the beam peak to any direction ofi the broadside along the same plane. Reduction of sidelobe level in concentric ring array of isotropic antennas scanned in the x-z plane result in a wide flrst null beamwidth (FNBW). In this paper, the authors propose pattern synthesis methods to reduce the sidelobe levels with flxed FNBW by making the scanned array thinned based on two difierent global optimization algorithms, namely Gravitational Search Algorithm (GSA) and modifled Particle Swarm Optimization (PSO) algorithm. The thinning percentage of the array is kept more than 45 percent and the flrst null beamwidth (FNBW) is kept equal to or less than that of a fully populated, uniformly excited and 0:5‚ spaced concentric circular ring array of same scanning angle and same number of elements and rings.

SYNTHESIS OF THINNED PLANAR CIRCULAR ARRAY ANTENNAS USING MODIFIED PARTICLE SWARM OPTIMIZATION

In this paper, the authors present an optimization method based on modifled Particle Swarm Optimization (PSO) algorithm for thinning large multiple concentric circular ring arrays of uniformly excited isotropic antennas that will generate a pencil beam in the vertical plane with minimum relative side lobe level (SLL). Two difierent cases have been studied, one with flxed uniform inter-element spacing and another with optimum uniform inter-element spacing. In both the cases, the number of switched ofi elements is made equal to 220 or more. The half- power beam width of the synthesized pattern is attempted to make equal to that of a fully populated array with uniform spacing of 0:5‚. Simulation results of the proposed thinned arrays are compared with a fully populated array to illustrate the efiectiveness of our proposed method.

FIRE FLY AND ARTIFICIAL BEES COLONY ALGORITHM FOR SYNTHESIS OF SCANNED AND BROADSIDE LINEAR ARRAY ANTENNA

This paper describes the application of two recently developed metaheuristic algorithms known as flre ∞y algorithm (FFA) and artiflcial bees colony (ABC) optimization for the design of linear array of isotropic sources. We present two examples: one for broad side arrays and the other for steerable linear arrays. Three instances are presented under each category consisting of difierent numbers of array elements and array pattern directions. The main objective of the work is to compute the radiation pattern with minimum side lobe level (SLL) for specifled half power beam width (HPBW) and flrst null beam width (FNBW). HPBW and FNBW of a uniformly excited antenna array with similar size and main beam directions are chosen as the beam width constraints in each case. Algorithms are applied to determine the non-uniform excitation applied to each element. The efiectiveness of the proposed algorithms for optimization of antenna problems is examined by all six sets of antenna conflgurations. Simulation results obtained in each case using both the algorithms are compared in a statistically signiflcant way. Obtained results using flre ∞y algorithm shows better performances than that of artiflcial bees colony optimization technique provided that the same number of function evaluations has been considered for both the algorithms.

Design of Phase-Differentiated Reconfigurable Array Antennas With Minimum Dynamic Range Ratio

In this letter, we propose a real-coded genetic algorithm (GA) for optimal design of reconfigurable dual-beam linear array antennas with phase only control. The problem is to find a common amplitude distribution with minimum dynamic range ratio (DRR) that will generate a pencil beam with zero phases and a flat-top beam with continuously controllable phases of an analog phase shifter. Results are also shown for the same design without minimizing dynamic range ratio (amax /amin) of excitation amplitude

Design of a Fully Digital Controlled Reconfigurable Switched Beam Concentric Ring Array Antenna Using Firefly and Particle Swarm Optimization Algorithm

Reconflgurable antenna arrays are often capable of radiating multiple patterns by modifying the excitation phases of the elements. In this paper a method based on Fire∞y Algorithm (FA) has been proposed to obtain dual radiation pattern from a concentric ring array of isotropic elements, by flnding out two difierent combinations of states for the switches, which are assumed to be connected with the rings of the array, along with optimum set of 4-bit radial amplitude and 5-bit radial phase distributions of the array elements for the speciflc switch combinations. The optimum excitations of the array elements in terms of discrete amplitudes and discrete phase, and the difierent switch combinations for the speciflc excitations are computed using Fire∞y Algorithm. To illustrate the efiectiveness of Fire∞y Algorithm, the two beam pairs have been computed by the same procedure from the same array, using Particle Swarm Optimization (PSO) algorithm, without changing their design criteria. Results clearly show the superiority of the Fire∞y Algorithm over Particle Swarm Optimization to handle the proposed problem.

Design of Fully Digital Controlled Reconfigurable Array Antennas with Fixed Dynamic Range Ratio

In this paper, we propose an optimization method based on Genetic Algorithm (GA) for design of reconfigurable dual-beam linear isotropic antenna arrays with phase only control of digital phase shifters. The problem is to find a fixed amplitude distribution using four-bit digital attenuator that will generate two broadsided symmetrical beams in vertical plane: a pencil beam with zero phases and a flat-top beam with discrete phases of a five-bit digital phase shifter, with or without pre-fixing the dynamic range ratio (I max /I min) of excitation amplitude distribution to a value equal to or less than seven.

Design of Fully Digital Controlled Reconfigurable Dual-Beam Concentric Ring Array Antenna Using Gravitational Search Algorithm

In this paper, we propose an optimization method based on Gravitational Search Algorithm (GSA) for design of reconflgurable dual-beam concentric ring array of isotropic elements with phase only control of flve-bit digital phase shifters. The problem is to flnd a common radial amplitude distribution using four-bit digital attenuator that will generate three difierent types of broadsided beam pair in vertical plane: a pencil/pencil beam pair, a pencil/∞at-top beam pair and a ∞at-top/∞at-top beam pair (sector pattern) with desired value of side lobe level, flrst null beam width and ripple. The two patterns difier only in radial discrete phase distribution while sharing a common discrete radial amplitude distribution. The optimum sets of four- bit discrete radial amplitude distribution generated by four-bit digital attenuators and flve-bit discrete radial phase distribution generated by flve-bit digital phase shifters for obtaining dual radiation patterns are computed by Gravitational Search Algorithm.

Minimization of side lobe level and side band radiation of a uniformly excited time modulated linear antenna array by using Artificial Bee Colony algorithm

In this work, the Artificial Bee Colony (ABC) algorithm is used to minimize the side lobe level of the main beam and the first two side band radiation of the uniformly excited time modulated linear antenna array. ABC searches the switch on or excitation time duration of each of the element of the antenna array under consideration. This approach gives satisfactory results without changing the amplitude of the antenna elements.