Aaron Angel Salas-Sanchez

• University of Santiago de Compostela

The present work develops an innovative methodology for fixing deep nulls in radiation patterns of symmetrical thinned arrays while maintaining a low side lobe level (SLL) and a high directivity, implementing an optimization strategy based on the simulated annealing algorithm (SA). This procedure optimizes a cost function that has a term for each c...

Antenna array pattern reconfiguration is usually achieved by changing the relative amplitudes and/or phases of the excitation distribution present in the array, at the cost of complex feeding networks. In this work, the mechanical displacement of a parasitic array perpendicular to another array with a single driven element is proposed. Additionally...

Brain tissue may be especially sensitive to electromagnetic phenomena provoking signs of neural stress in cerebral activity. Fifty-four adult female Sprague-Dawley rats underwent ELISA and immunohistochemistry testing of four relevant anatomical areas of the cerebrum to measure biomarkers indicating induction of heat shock protein 70 (HSP-70), gluc...

In the present paper, an iterative technique devoted to reproducing efficient footprints with arbitrary boundaries for planar arrays is addressed. The methodology here depicted is based on exploiting the nature of the continuous aperture distribution by expressing it as a Fourier series of moderately high orders. In this manner, the resulting illum...

In this study we analyzed the response of parafollicular cells in rat thyroid gland after exposure to radiofrequency at 2.45 GHz using a subthermal experimental diathermy model. Forty-two Sprague Dawley rats, divided into two groups of 21 rats each, were individually exposed at 0 (control), 3 or 12 W in a Gigahertz Transverse Electro-Magnetic (GTEM...

The techniques on the generation of multiple solutions in shaped-beam pattern synthesis are standardly focused on the use of patterns with complex nature as input. Otherwise, in order to derive a symmetric pure real distribution from the canonical pattern synthesis techniques, a generation of a pure-real pattern has to be imposed. In the present wo...

In the present work, the theoretical basis of the multiplicity of solutions obtained from an initial real symmetric distribution is derived. This initial solution is devoted to generating an equivalent pure real shaped-beam pattern for a concrete synthesis scenario. However, these new solutions are not based on real symmetric distributions; hence,...

Environmental factors such as air pollution by particles and/or electromagnetic fields (EMFs) are studied as harmful agents for human health. We analyzed whether the combined action of EMF with fine and coarse black carbon (BC) particles induced cell damage and inflammatory response in RAW 264.7 cell line macrophages exposed to 2.45 GHz in a gigahe...

In this work, the application of a technique for monitoring changes of the dielectric constant of the atmosphere caused by the presence of pollution is discussed. The method is based on changes in the reflection coefficient of the device induced by these dielectric constant variations of the surrounding medium. To that end, several Yagi–Uda-like an...

An inversion strategy for dynamically thinning (i.e.. turning on and off) the radiating elements of ring arrays in order to maximize the signal-to-noise ratio is presented. Since thinned arrays provide only average sidelobe performances, but. the directions of arrival ( DoAs ) of interferences can be arbitrary, a set. of thinning configurations tha...

In this work, the design of monopulse linear arrays generating sum and difference patterns with a partially shared beam forming network is addressed as an inverse problem and solved through a suitable inversion strategy. The array tails are organized into sub-arrays controlled by amplitude weights, while the remaining array elements have two indepe...

Innovative teaching methods that address paramount challenges in modern electromagnetic (EM) engineering education are presented. An entire ecosystem of novel and interconnected strategies and tools has been developed by the ELEDIA Research Center to build a long-term educational and training framework for future EM professionals. According to an E...

Implications and improvements of edge brightening effects led by Q factor minimization restricted to keep the same level of directivity for high efficiency continuous circular aperture distributions are here reported. In this manner, an optimization strategy for a minimum Q value-keeping the same level of efficiency and restricting the maximum side...

Studies are based on the exposure of Sprague-Dawley rats (250 male and 250 female rats) to electromagnetic fields (EMF) at different frequencies in standing and travelling wave chambers. Values of specific absortion rate (SAR) for all of these experiments were obtained from commercially available FDTD-based simulation software based on numerical ph...

A novel hybrid approach to the power synthesis of mask-constrained shaped beams by means of concentric-ring isophoric arrays is presented. The basis of this procedure is to use the complex aperture distribution obtained by Elliott-Stern method as a starting point of an innovative algorithm that combines a classical density tapering method with a si...

Purpose: The aim of this study was to determine whether exposure to radiation from single or multiple radio-frequency (RF) signals at 900 and 2450 MHz would induce effects in the RAW 264.7 cell line. Materials and Methods: Cell cultures were exposed to single or combined RF for 4, 24, 48 or 72 hours in a GTEM electromagnetic test chamber. At the en...

Coating an antenna with a hydrophilic polyimide film has been reported to enhance the effects of atmospheric relative humidity on the characteristics of the antenna. In this letter, we designed Yagi-Uda antennas with polyimide-coated dipoles, and we performed a simulation study investigating the influence of atmospheric relative humidity on their r...

Interest in uniformly illuminated (isophoric) density-tapered planar antenna arrays has recently revived. For arrays consisting of concentric rings of elements, we present a non-stochastic algorithm that calculates ring radii for generation of pencil beams without the need for prior specification of the number of rings. Use of the algorithm is illu...

Particulate atmospheric pollution alters the dielectric coefficient of the atmosphere. In principle, this could allow pollution to be measured via its effects on the performance of an antenna. In this letter, a novel technique for measuring these effects, based on the use of an optimized air-filled waveguide-fed slot linear array, is shown.

A simple and economical method for monitoring the electromagnetic field intensity in built-up areas is presented. The method is based on the measurement of the field level over a limited number of points at street level in the city, and their transmission to an Operative Control Center, where the field values all over the city are correctly interpo...

An antenna design based on the use of an active dipole placed above a ground plane with an array of parasitic dipoles is presented. The presence of the parasitic dipoles increases the effective antenna size and significantly improves directivity over that of an isolated dipole in front of a ground plane. In addition, the use of just one active elem...

The use of Taylor and Ludwig circular distributions are two useful approaches to the synthesis of sum and shaped patterns using planar arrays with circular boundaries. The excitations of the discrete arrays are determined by conventional sampling of these continuous distributions. These two techniques use a transition parameter (n̅) that controls t...

In many places, atmospheric pollution is a serious public health problem. The respiratory systems of children and the aged are particularly affected; for the most vulnerable, atmospheric pollution can be mortal. Other environmental effects include reduction of the ozone layer (which in turn favours skin cancers), and damage to the fabric of buildin...

The objective of this study was to investigate the effects of multiple signal electromagnetic field in rat brain at 900 and 2450 MHz and their combination. Induction of cytoprotective heat shock proteins (HSPs) or pre-apoptotic proteins in response to stress as the source electromagnetic field may suggest that they shift cellular equilibrium toward...

Given a circular antenna array, and a requirement for the sidelobes surrounding a pencil beam or flat-topped beam to have a specified φ dependence, it can be advantageous to optimize the array excitations for the best fit between the far field and a pattern synthesized for a continuous circular aperture of the same size.

Given a circular antenna array, and a requirement for the side lobes surrounding a pencil beam or flat-topped beam to have specified φ dependence, it can be advantageous to optimize the array excitations for best fit between the far field and a pattern synthesized for a continuous circular aperture of the same size.

Multiple simultaneous exposures to electromagnetic signals induced adjustments in mammal nervous systems. In this study, we investigated the non-thermal SAR (Specific Absorption Rate) in the cerebral or cerebellar hemispheres of rats exposed in vivo to combined electromagnetic field (EMF) signals at 900 and 2450 MHz. Forty rats divided into four gr...

In this paper, we describe the synthesis of circular-Taylor-like patterns for antennas composed of concentric rings of uniformly excited elements. Optimization of the ring radii achieves close approximation to the envelope of the desired pattern within a given cone about the main beam. An alternative approach, using annular subarrays, speeds comput...