This study presents the study of beamforming capabilities of arrays installed on a non‐conductive unmanned aerial vehicle (UAV). The main purposes of this study are the application of a beamforming algorithm by including the airframe in the optimisations and the study of simplifications of the aircraft model, so as to allow performing full‐wave simulations, even though the UAV is much larger than the operating wavelength. To validate the simplified electromagnetic model, antenna arrays have been designed and installed onto the UAV. Radiation pattern measurements demonstrate that the proposed simplifications yielded very good radiation pattern predictions and can be used as guidelines for simulation of other kinds of non‐conductive aircrafts.
This paper presents the application of optimization methods for the synthesis of a linear array to operate in the frequency range of 4G technology in Brazil. The desired pattern shall exhibit squared-cosecant shape, so as to provide uniform distribution of power inside the base station cell and to reduce co channel interference. Such an array is well suited to operate as a radio base station of mobile communications systems. The synthesis is performed by a combination of optimization methods: the genetic algorithm, which is used for the initial global search, and the sequential quadratic programming, which is applied for local refinement of the solution. This approach allows faster convergence than using only one kind of optimization method. The technique is demonstrated for a linear array of isotropic elements and, subsequently, for an array of E shaped microstrip antennas.
This paper presents an analysis for optimal design of switched beamforming applied to a linear array for wireless communication systems. The beam switching scheme provides coverage of a given sector in azimuth and controls the sidelobe level simultaneously. The analysis was developed considering arrays composed of Quasi-Yagi elements. The model assumes a user moving in the azimuthal direction under a constant velocity and with an estimation of the signal-to-noise ratio (SNR) at the mobile user (MU). The radio base station applies the beam that yields the best performance during transmission. The decision is based on the feedback information received from the MU. The goal of the analysis is to determine the best trade-off between the array size and number of feedback bits necessary to maximize the SNR at the receiver. The results show that a compromise between the number of beam-pointing directions and the array size should be taken into consideration for a wireless communication system design.
This study presents a technique to design antenna arrays with shaped radiation pattern. The efficiency of the proposed technique is demonstrated for the optimisation of a linear microstrip array for radio base stations of mobile communication systems. The main beam is shaped so as to provide uniform distribution of power inside a sector of a cell and to minimise the power radiated above the horizon. The synthesis of the shaped pattern is achieved by a combination of genetic algorithm and sequential quadratic programming. In contrast to several papers found in the literature that consider only isotropic antennas, the proposed approach takes into account all the radiation properties of small arrays, such as the mutual coupling between the array elements and edge effects. Finally, the design of the feeding system to produce the synthesised pattern is discussed. Measurements are used to validate the proposed technique.
Resumo-Este artigo apresenta o estudo de uma antena com geometria do tipo fenda anelar para sistemas de navegação global via satélite. Com o auxílio de resultados numéricos, os principais parâmetros de projeto são analisados. O procedimento de otimização das redes de casamento para ajuste da impedância de entrada do irradiador é descrita. Finalmente, um acoplador híbrido de 90° é conectado às saídas da antena para possibilitar recepção de ondas circularmente polarizadas à direita. Com apenas um laminado de micro-ondas, foi possível projetar uma antena circularmente polarizada com um acoplador híbrido integrado, o que resulta em um processo de construção extremamente simples e com baixo custo.
Palavras-Chave-Antenas para sistemas de navegação, antenas em fenda anelar, fendas eletromagnéticas.Abstract-This paper describes the analysis of an annular-slot antenna for global navigation satellite systems. The main design parameters are analyzed and numerical results are shown. The optimizations performed for the impedance matching networks are described. Finally, a 90°-hybrid is integrated to the antenna outputs, so as to allow reception of right-handed circularly polarized waves. The design of this radiator was possible by employing only one dielectric layer for both slot-ring antenna and the feeding lines. This yielded an optimized geometry that is low-cost and easy to fabricate.
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