Hybrid particle swarm-based algorithms and their application to linear array synthesis

A heuristic particle swarm optimization (PSO) based algorithm is presented in this work and the novel hybrid approach is applied to linear array synthesis considering complex weights and directive element patterns so as to analyze its usefulness and limitations. Basically, classical PSO schemes are modified by introducing a tournament selection strategy and the downhill simplex local search method, so that the hybrid algorithms proposed combine the strengths of the PSO to initially explore the search space, the pressure exerted by the genetic selection operator to manage and speed up the search, and finally, the ability of the local optimization technique to quickly descend to the optimum solution. Four classical real-valued PSO schemes are taken as reference and synthesis results for a 60-element linear array comparing those classical schemes and the hybridized ones are reported and discussed in order to show the improvements achieved by the hybrid approaches.This work was supported by the Spanish Ministry of Science and Innovation (project number TEC2008-02730/TEC)

Aplicación de algoritmos genéticos y recocido simulado a la reconstrucción del diagrama de radiación de antenas

The performance of different local and global optimisers applied to antenna far-field pattern prediction from planar near-field information is presented. The method proposed replaces the antenna under test by equivalent magnetic surface currents whose components are computed from reference near-field data using an appropriate optimisation technique. From the optimised equivalent model, antenna far-fields can be reconstructed. The Nelder Mead downhill simplex algorithm, along with global optimisers such as genetic algorithms (GA) and simulated annealing (SA) were all investigated and compared. Numerical results demonstrate that hybrid GA outperform local optimisers, classical real and binary encoding GA and SA. Results of near-field to far-field transformation are also included and discussed

Synthesis of planar arrays using a modified particle swarm optimization algorithm by introducing a selection operator and elitism

A modified particle swarm optimization (PSO) algorithm applied to planar array synthesis considering complex weights and directive element patterns is presented in this paper. The modern heuristic classical PSO scheme with asynchronous updates of the swarm and a global topology has been modified by introducing tournament selection, one of the most effective selection strategies performing in genetic algorithms the equivalent role to natural selection, and elitism. The modified PSO proposed combines the abilities of the classical PSO to explore the search space and the pressure exerted by the selection operator to speed up convergence. Regarding the optimization problem, the synthesis of the feeds for rectangular planar arrays consisting of microstrip patches or subarrays of microstrip patches is considered. Results comparing the performance and limitations of classical and modified PSO-based schemes are included considering both test functions and planar array complex synthesis to best meet certain far-field radiation pattern restrictions given in terms of 3D-masks. Finally, representative synthesis results for sector antennas for worldwide interoperability for microwave access (WiMAX) applications are also included and discussed

Optimización con enjambre de partículas aplicada a la reconstrucción del diagrama de radiación de antenas

A particle swarm optimization (PSO) based algorithm applied to antenna far-field radiation pattern prediction from planar near-field data is presented. The radiation of the antenna is modelled using equivalent magnetic surface currents (EMC) whose components are optimized using a global PSO with asynchronous updates of the swarm. A general overview of the PSO algorithm is included and the most widely used schemes of the optimizer are presented and discussed. A parametric study of the main parameters to be tuned in PSO, along with results of near-field to far-field transformation are also included to demonstrate the usefulness of the optimization method

Transformación de campo cercano a campo lejano utilizando corrientes equivalentes y algoritmos genéticos

A method for computing far-field antenna patterns from planar near-field samples is presented. The method, based on the equivalence principle, replaces the antenna under test by a set of equivalent magnetic currents (EMC), and a binary micro genetic algorithm is used to optimise the amplitudes of the EMC from the near-field data. A second approach, using an equivalent model for the source made up of electric short dipoles, is also analysed. From the optimised equivalent model, the antenna far-field pattern can be easily computed. Numerical results using synthetic near-field data are reported and discussed

Reciprocal circular polarization handedness conversion using chiral metamaterials

Chiral metamaterials (CMMs) are widely used to implement devices that transform the polarization of an incident electromagnetic wave, such as polarization rotators and linear to circular converters, but rarely used as circular polarization converters. This letter presents a CMM that changes the handedness of a circularly polarized incident wave. This structure, which presents subwavelength thickness, provides polarization conversion with independence on both the front and back directions and the handedness of the incident wave. High polarization conversion efficiency is shown by both simulations and experiments.This work has been partially supported by the Spanish Government MINECO through the FEDER co-funded Research Project TEC2014-55463-C3-3-P and the Research Project TEC2012-33321

Binary phase-controlled multi-beam-switching antenna array for reconfigurable 5G applications

The paper presents a two-phase state based multi-beam-switching scheme implemented on a customdesigned 4 × 4 antenna array operating with a bandwidth of 1.5 GHz around 14 GHz. The antenna array and the beam-switching scheme have been experimentally validated. A phasing network designed to produce two phase states is used to experimentally validate the beam-switching and five beam states are presented, though this can be extended to other configurations using the split beam as a building block to construct multiple beams. The antenna can find potential use in multi-user millimetre-wave massive MIMO scenarios which require simultaneous multiple beams along selective directions.This work was supported by the 5G wireless project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 641985 and by the University of Cantabria PAR project P111

Asymmetric chiral metamaterial superstrate for patch antenna polarization transformation

Planar superstrates constituted by Chiral Metamaterials structures can transform the radiation properties of an antenna. In this communication, an asymmetric chiral metamaterial based structure is proposed. Due to the lack of C4 symmetry in the design, the transmission coefficients depend on the incident wave polarization and display high transmission for one circular polarization but low transmission for the other one. The proposed structure is then used to improve the radiation characteristics of a microstrip patch antenna. Taking advantage of the properties of the asymmetric chiral structure, the polarization of the radiated field is modified, transforming the linear polarization of the microstrip antenna into a circular one.This work has been partially supported by the Spanish Government MINECO through the FEDER co-funded Research Project TEC2014-55463-C3-3-P and the Research Project TEC2012-33321

Quasi-optics-inspired low-profile endfire antenna element

In this paper, the design, operational principle and experimental validation of an endfire antenna element that is inspired by the energy-focusing characteristics of graded-index optical fibre are presented. The antenna operates with a bandwidth of 1.5 GHz centred around 14 GHz. It has a gain of around 5.5 dBi along the band of interest and a good pattern stability over the band. The antenna derives its unique nature from the arrangement of the arc-shaped parasitics, that couple onto the antenna´s driver dipole. An electromagnetic refractive index retrieval mechanism is used to guide the placement of the parasitics to enhance the gain. In addition to the design principle, a parametric study of the main parameters and their influence on the antenna behaviour is presented. The antenna is a potential candidate for use in multi-user massive MIMO antenna arrays for 5G communications where space is premium and in antenna array applications where a low-profile antenna element with a high gain is a necessity.This work was supported by the 5G wireless project that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 641985

Síntesis de agrupaciones planas mediante optimización con enjambre de partículas

In this work, classical real–valued particle swarm optimization (PSO) schemes have been modified by introducing a selection operator commonly used in genetic algorithms (GA), the tournament selection strategy (TS). The usefulness and limitations of the hybridized approach have been analyzed by comparing it with some well–known PSO classical schemes, when both are applied to planar array synthesis using complex weights. The preliminary statistical results obtained demonstrate the usefulness of the hybrid approach. For those purposes, the synthesis of the complex element weights to best meet certain far–field radiation pattern restrictions given in terms of 3D–masks has been considered as the canonical problem. Finally, further representative synthesis results for a planar array to be considered as a 60 degrees sector antenna for local multipoint distribution systems (LMDS) are also included