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This paper presents a study on the synthesis of a position-phase optimized reconfigurable linear array antenna with uniform amplitude distributions. The objective is to produce a pencil/flat-top beam pair. In this position-phase method, a pencil beam is duly generated with zero degree phases and phases are varied between −180° and 180° to produce a flat-top beam keeping position of the elements and amplitude excitations common to both pencil and flat-top beams. The amplitude distribution of the elements is kept uniform. The phases as well as position of the elements are optimized by Teaching Learning Based Optimization (TLBO), modified Quantum Particle Swarm Optimization (QPSO) and Symbiotic Organisms Search (SOS) algorithms to produce the beam pair. The simulations are done for two Sets of elements and a null placement is included in one of the Sets. The results obtained using these algorithms are duly compared with each other and it is found that SOS algorithm performed in par with TLBO algorithm in the generation of the radiation pattern parameters and better over TLBO and QPSO in statistical values.

In this paper, the optimal reduction of side lobe level with constraints of a suitable first null beam width of a non-uniform concentric elliptical array antenna of uniformly excited isotropic elem...

In this paper, a cuckoo search algorithm based on the combined characteristics of the brood parasite behavior and Levy flights is applied to correct the radiation pattern of a linear antenna array composed of parallel dipoles with faulty elements. An effort is made to restore the radiation pattern similar to one without any faulty elements, and the difference in the values of side lobe level and wide null depth of both patterns, as well as the voltage standing wave ratio obtained from the new voltage excitations become diminished. The examples presented in this paper show the effectiveness of this algorithm in correcting the radiation pattern of a linear array of 36 and 120 dipole antennas with four and ten failed elements, respectively. The results show that the matching condition and the wide null control produced by Cuckoo Search algorithm are more efficient in comparison with the benchmark failure correction algorithm. The approach adopted herein may be applied to other array configurations as well

This paper presents a method based on the Moth Flame optimization evolutionary algorithm for the synthesis of Flat-top/pencil beam pair of dual beam reconfigurable concentric circular antenna array...

A compact CPW-fed slot antenna is proposed here. The antenna has a pentagonal patch nested within an asymmetrical slot along with a coplanar waveguide feed. The suggested antenna also has a circula...

In this paper, a method relying on Symbiotic Organisms Search optimisation algorithm is proposed for the design of a reconfigurable concentric circular array with phase-only controls differentiatin...

In this paper, a novel method for designing unequally spaced time-modulated arrays (UESTMAs) with fewer optimization parameters in two steps has been investigated. Different cases of synthesis method such as position-only (PO), on-time only (OTO), on-time then position (OTTP) and position then on-time (PTOT) have been considered to design the array. For each case under consideration, the global search stochastic algorithm based on differential evolution (DE) has been employed to achieve the array pattern with significantly suppressed sidelobe levels (SLLs) and sideband levels (SBLs) by separately considering the element position and switch on-time of the array elements as the optimization parameters. Through detail comparative results, it is shown that the performance of PTOT synthesis method with fewer optimization parameters in two steps provides better or equivalent performance as compared with the reported approach where both position and on-time are considered simultaneously. The representative numerical results for a 32 element linear array have been presented to show the effectiveness of the proposed approach.

In this paper, a novel approach to synthesize sum and difference pattern through time modulation in unequally spaced linear arrays with uniform amplitude excitation is presented. Both the patterns are obtained with same element position, whereas the two patterns differ only in switch on-time sequence of the fast electronically controlled switches commutating the radiators. Stochastically, the global exploring capability of differential evolution (DE) is employed to obtain the optimized element position and on-time sequence of the antenna elements. The suitability and usefulness of the proposed method are illustrated through representative results of a 20 element linear array.

Researchers on antenna arrays usually neglect the effect of mutual coupling of antennas placed in proximity to each other. The interchange of electromagnetic energy happening between an antenna and a far field point depends not only on the transmitting antenna, but also from its neighbouring antennas. This effect is referred to as mutual coupling between dipole antenna elements and it is considered here in the synthesis of phase only reconfigurable antenna arrays. The main objective of this work is to produce desired Side Lobe Level and Voltage Standing Wave Ratio in addition to few other radiation pattern parameters. Multiverse Optimization algorithm is employed for the purpose of generating voltage amplitude and discrete phase distributions in the dipole elements for the generation of flat-top beam/pencil beam patterns. These two patterns share the common amplitude distributions and differ in phase distributions. Results obtained using MATLAB simulations prove that this algorithm accomplished its task successfully and is also found to be superior over other algorithms like Particle Swarm Optimization, Grey Wolf Optimization and Imperialist Competitive Optimization algorithms.

A method based on quantum particle swarm optimization is proposed for correcting radiation pattern of a uniformly spaced linear array of parallel half-wavelength vertical very thin dipole antennas when more than one element of the array is completely defective. The generated pattern is broadside in the horizontal plane. Mutual coupling between the half-wavelength parallel dipole antennas has been taken care of by induced EMF method considering the current distribution on each dipole to be sinusoidal. Side lobe level and minimum return loss of the corrected pattern with defective elements are also calculated and an attempt is made that these parameters be equal to their respective specified values. This is usually done by changing excitation current amplitude of the non-defective elements without replacing the faulty elements. The element pattern of half-wavelength dipole antenna has been assumed omni-directional in the horizontal plane. Two examples are presented to show the effectiveness of the proposed approach.

A compact circularly polarized CPW-fed slot antenna is proposed here. The antenna consists of a pentagonal patch within an asymmetrical slot with a single coplanar waveguide feed. The proposed antenna is excited with CPW feed mechanism and investigated experimentally. The structure is fabricated on FR4 epoxy substrate with a permittivity of 4.4. The impedance bandwidth of 10[Formula: see text]GHz (4[Formula: see text]GHz to 14[Formula: see text]GHz) and the axial ratio bandwidth of 1.2[Formula: see text]GHz with the corresponding fractional bandwidth of 113%. The simulation results fulfil the bandwidth requirements of IEEE 802.11a (5.15–5.35[Formula: see text]GHz/5.47–5.725[Formula: see text]GHz) for wireless applications. In terms of bandwidth, compactness and circular polarization comparable results between simulated and measured results clearly show the validity of the proposed structure.

In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switch- ofi of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs) and on-time durations (OTDs) of a time-modulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the flrst positive and negative harmonics of the time- modulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at difierent harmonics can be simultaneously used as independent communication channels. By employing a difierential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a ∞at-top or a cosec square pattern at flrst positive and negative sidebands of side-lobe levels (SLL) i20dB can be synthesized by suppressing the higher sideband level (SBL) to below i10dB.

In this paper, a new technique is proposed to optimize the con∞icting parameters like low value of maximum side lobe level (SLL), narrow beam-width of the main beam and low value of maximum sideband radiation level (SRL) of time-modulated linear antenna arrays (TMLAAs). The method is based on minimizing a multi-objective fltness function by using single-objective difierential evolution algorithm (DEA) technique. The method is applied to both uniformly excited TMLAA (UE-TMLAA) and non-uniformly excited TMLAA (NUE-TMLAA) to synthesize low side lobe optimum pattern at operating frequency by suppressing the sideband radiation level to a su-ciently low value. For UE-TMLAA only the switch- on time durations of the array elements and for NUE-TMLAA the switch-on time durations and the static amplitudes with predetermined dynamic range ratio (DRR) of static amplitudes are taken as the optimization parameters for the DEA. To show efiectiveness of the proposed approach, the single-objective DEA optimized results are compared with those obtained by other single objective and multi- objective techniques that has been reported previously. Also, flrst null beam width (FNBW) and half power beam width (HPBW) of the DEA optimized patterns at fundamental radiation are compared with those of the Dolph-Chebyshev (D-C) pattern of same SLL.

In this paper, authors propose a method based on the modified particle swarm optimization (PSO) for beam reconfiguration of linear array of mutually coupled parallel half-wavelength dipole antennas with real excitation voltage amplitude distribution. Two different beam pairs are generated, one pencil/pencil beam pair and another pencil/flat-top beam pair in the horizontal plane. One beam is changed to another through switching while sharing a common amplitude distribution. Two examples are presented, one without ground plane and another in presence of ground plane. Dipoles are connected to its feed network through a switch, so that it can be turned on or off, depending on the switch position. Beam reconfiguration is achieved by suitably turning the array elements on or off using same voltage excitation distribution. Modified PSO is used to compute the excitation voltages as well as the switching configuration for each pattern having a prefixed side lobe level. The current in the driven and parasitic elements is determined via induced EMF method considering the current distribution on each dipole to be sinusoidal. Proposed method efficiently synthesizes dual-beam switching the power pattern from pencil to pencil and pencil to flat-top having same or different side lobe levels using common excitation voltages. It calculates the maximum variation of the active impedance of driven elements and the power losses when the radiation patterns switch from one beam to another. The paper calculates the array directivity as the distances between antenna array and the ground pane varies. Three other state-of-the-art metaheuristics like differential evolution, gravitational search algorithm, artificial bee colony algorithm are also employed for achieving a comparative evaluation.

In this paper, we propose an optimization method based on Particle Swarm Optimization (PSO) algorithm for thinning a large multiple concentric circular ring array of uniformly excited isotropic antennas and generate a pencil beam in the vertical plane with minimum relative side lobe level (SLL). The half-power beam width of the pattern is attempted to make equal to that of a fully populated array of same size and shape. The synthesis is performed with a standard particle swarm optimization technique as well as with an improved version of standard PSO. Simulation results of the proposed thinned array are compared with a fully populated array to illustrate the effectiveness of our proposed method.

In this paper, we present a new method based on real-coded Genetic Algorithm (GA) with elitist model for optimal design of a reconfigurable symmetrical dual-beam uniformly spaced linear isotropic antenna array with phase-only control of quantized phase shifters. The problem is to find a common amplitude distribution that will generate a pencil beam with zero phases and a flat-top beam with discrete phases of a six-bit discrete phase shifter, without or with pre-fixing the value of dynamic range ratio (|I max/I min|) of excitation current amplitude distribution equal to or less than five.

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.

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.

In this paper, sideband radiations which are generally regarded as the undesired effects of time-modulated antenna arrays (TMAAs), are exploited to design multi-beam antenna arrays. Time modulation (TM) is applied into uniformly excited linear array of half wave dipole radiators to generate low side-lobe sum and difference patterns at the center frequency and first sideband respectively while the maximum power level at the higher sidebands are suppressed significantly by optimizing the periodical on-off switching instants of the antenna elements by using fire-fly algorithm (FA). The FA optimized pattern as realized in MATLAB platform is validated by designing the uniformly excited time modulated linear array (UE-TMLA) in CST-MWS with the same on-time sequence as obtained by using FA and the patterns are compared.

In this work, the effectiveness of a relatively newly developed optimization algorithm, artificial bee colony (ABC) algorithm has been employed to synthesize uniformly excited, non-uniformly spaced, symmetrical linear arrays. ABC is used to reduce the side lobe level (SLL) of uniformly excited linear antenna arrays by taking the element spacing as the optimization parameters. The effectiveness of the proposed approach is demonstrated by considering a linear antenna array of 32 elements. The array of isotropic elements is synthesized for the different search space of the element spacing and a typical variation of the SLL with different limiting values of the maximum element spacing is presented. It is observed that, for the isotropic element array when the search range of the normalized element spacing's relative to the operating wavelength is (0.5, 1), the maximum reduction of side lobe level (-21.22 dB) is obtained. At the end the array with half-wavelength dipole is considered and with the search range of the element spacing's, (0.5, 1), SLL is reduced to -22.99 dB.

In this paper, a cosecant squared shaped beam pattern is synthesized from a uniformly spaced but nonuniformly excited linear antenna array where the uniform spacing of the array elements is considered as half of the desired signal wavelength. The shaped beam pattern is synthesized for the angular beam width of 320 by reducing the side lobe level (SLL) to -20.06 dB and almost without any ripple in the shaped region. To get the desired pattern, excitation coefficients and the static phase shift of the array elements are taken as the optimizing parameters and the differential evolution (DE) algorithm is used as the optimizing algorithm. It is further observed that the desired array pattern is remained unaltered for a band of frequency on either side of the operating frequency.

This paper presents a method based on iterative fast fourier technique to minimize peak side lobe level of a linear array of uniformly spaced isotropic antennas by 3-bit digital attenuator. One example has been presented with 30 isotropic antennas. The synthesis is performed by varying only discrete amplitude values of a 3bit attenuator. Pattern generated is broadside when all excitation phases of the elements are kept constant, i.e. zero degree. Array factor is related to element excitations via inverse Fourier transform for a linear array of isotropic antennas with uniform element spacing. This property is used in this method.

In this paper, a new approach to reduce the side band radiation level of time modulated linear array is presented. Keeping normalized on-time duration of the array elements at each modulation period remains unchanged for a given pattern at fundamental radiation, a suitable time delay is provided before the switch-on instants of the array elements. The method is applied to the pattern where the fundamental radiation is a static Dolph-Tschebyscheff (DT) pattern with SLL of −40dB. The optimum time delay required for the array elements are explored through particle swarm optimization technique and it reduces the maximum of first side band radiation level from −12.7dB to −18.7dB and that of second side band from −17.5 dB to −22.1 dB.

In this paper, a flat-top beam pattern is generated through time modulation of linear array. Three parameters; side lobe level (SLL), ripple (R) and transition width (T) related are obtained as −30.2dB, 0.1dB and 6.4° respectively. To simplify the complexity of the feeding network, only two states of static phase shift (0, π) is considered. The maximum side band radiation level of the first two sidebands are also reduced to less than −33.4dB and −34.4dB respectively. Artificial Bee colony algorithm is used as the searching and optimizing algorithm for getting the desired results.

The Inverse Fast Fourier technique (IFFT) combined with Artificial Bees Colony (ABC) and Modified Particle Swarm Optimization (MPSO) is used for the synthesis of thinned mutually coupled linear array with uniform element spacing. Coupling effect has been taken into account via induced EMF method and used to calculate the induced current on each element. Proposed technique is employed to thin the array optimally to yield a minimum possible SLL and low return loss (RL). Performances of both the algorithms are compared to show the effectiveness of each optimizer. Introduction of Inverse Fast Fourier transform to calculate the array factor reduces the computation time significantly. The effectiveness of the proposed technique is demonstrated for 100- element linear array and results are compared with that of a fully populated array.

In this paper, the authors present a method based on modified particle swarm optimization for generating pencil beam in the vertical plane with minimum side lobe level and fixed first null beamwidth. The first null beamwidth is made equal to that of a uniformly excited and uniformly spaced multiple concentric circular ring array of same number of elements and same number of rings. The excitation amplitude is radially varied and optimized to achieve the goal. Example illustrates the potential of the method.

In this paper, the authors describe the synthesis of flat-top beam power pattern for antennas composed of concentric rings of isotropic elements. The synthesis is performed by particle swarm optimization (PSO), varying amplitudes and phases of the elements radially, so as to obtain desired side lobe level and ripple of flat-top beam in the vertical plane. Example illustrates the potential of the method.

[Abstract] In this letter, the authors propose an optimization method based on the genetic algorithm (GA) to reconfigure a linear array of vertical half-wavelength dipole antennas to generate two patterns with minimum active impedance variation when the antenna switches from one pattern to other in the presence or absence of a ground plane behind the array. The problem is to find a fixed voltage amplitude distribution that generates two broadside symmetrical beams in the horizontal plane: a pencil beam with zero phases and a flat-top beam with phases in the range from -180deg to +180deg. Mutual coupling effect is taken into account via open circuit mutual impedance matrix

Sidelobe reduction in an array antenna results in increased first null beamwidth. In this paper, the authors present a method based on a novel particle swarm optimisation with time-varying maximum velocity for focusing a beam at any direction in the vertical plane of a concentric ring array antenna with minimum sidelobe level while keeping the first null beamwidth of the array fixed. The excitation amplitude of the array elements along with the central element are radially varied and optimised using the proposed algorithm to reach the goal. Three different cases have been presented to illustrate the potential of the method.