María Jesús Algar

Application of Asymptotic and Rigorous Techniques for the Characterization of Interferences Caused by a Wind Turbine in Its Neighborhood

This paper presents a complete assessment to the interferences caused in the nearby radio systems by wind turbines. Three different parameters have been considered: the scattered field of a wind turbine, its radar cross-section (RCS), and the Doppler shift generated by the rotating movements of the blades. These predictions are very useful for the study of the influence of wind farms in radio systems. To achieve this, both high-frequency techniques, such as Geometrical Theory of Diffraction/Uniform Theory of Diffraction (GTD/UTD) and Physical Optics (PO), and rigorous techniques, like Method of Moments (MoM), have been used. In the analysis of the scattered field, conductor and dielectric models of the wind turbine have been analyzed. In this way, realistic results can be obtained. For all cases under analysis, the wind turbine has been modeled with NURBS (Non-Uniform Rational B-Spline) surfaces since they allow the real shape of the object to be accurately replicated with very little information.

An efficient hybrid technique in RCS predictions of complex targets at high frequencies

Abstract Most computer codes in Radar Cross Section (RCS) prediction use Physical Optics (PO) and Physical theory of Diffraction (PTD) combined with Geometrical Optics (GO) and Geometrical Theory of Diffraction (GTD). The latter approaches are computationally cheaper and much more accurate for curved surfaces, but not applicable for the computation of the RCS of all surfaces of a complex object due to the presence of caustic problems in the analysis of concave surfaces or flat surfaces in the far field. The main contribution of this paper is the development of a hybrid method based on a new combination of two asymptotic techniques: GTD and PO, considering the advantages and avoiding the disadvantages of each of them. A very efficient and accurate method to analyze the RCS of complex structures at high frequencies is obtained with the new combination. The proposed new method has been validated comparing RCS results obtained for some simple cases using the proposed approach and RCS using the rigorous technique of Method of Moments (MoM). Some complex cases have been examined at high frequencies contrasting the results with PO. This study shows the accuracy and the efficiency of the hybrid method and its suitability for the computation of the RCS at really large and complex targets at high frequencies.

Efficient combination of acceleration techniques applied to high frequency methods for solving radiation and scattering problems

Abstract An improved ray-tracing method applied to high-frequency techniques such as the Uniform Theory of Diffraction (UTD) is presented. The main goal is to increase the speed of the analysis of complex structures while considering a vast number of observation directions and taking into account multiple bounces. The method is based on a combination of the Angular Z-Buffer (AZB), the Space Volumetric Partitioning (SVP) algorithm and the A ∗ heuristic search method to treat multiple bounces. In addition, a Master Point strategy was developed to analyze efficiently a large number of Near-Field points or Far-Field directions. This technique can be applied to electromagnetic radiation problems, scattering analysis, propagation at urban or indoor environments and to the mutual coupling between antennas. Due to its efficiency, its application is suitable to study large antennas radiation patterns and even its interactions with complex environments, including satellites, ships, aircrafts, cities or another complex electrically large bodies. The new technique appears to be extremely efficient at these applications even when considering multiple bounces.

A study of the efficiency of the parallelization of a high frequency electromagnetic approach for the computation of radiation and scattering considering multiple bounces

Abstract Different schemes for the parallelization of a new algorithm to accelerate the Ray-Tracing for computing the electrical field radiated from or scattered by complex objects using high frequency techniques are presented. This algorithm is based on a combination of the Angular Z -Buffer (AZB), the Space Volumetric Partitioning (SVP) and the A*Heuristic search method. The algorithm is very useful for different applications. Basically, four kinds of analysis can be done with the tool: radiation pattern of antennas, electromagnetic field values in observation points in the near field, mutual coupling between antennas and propagation at indoor/outdoor environments. A computational analysis is shown for the different strategies of parallelization for shared and distributed memory computers.

Analysis of collision avoidance systems for automobile applications

The analysis of collision avoidance systems in real traffic urban scenarios represent a challenge for computational electromanetics due to its multiscale nature. An approach for solving this problem based on a combination of Multi-Level Fast Multipole Method (MLFMM), Characteristic Basis Functions (CBF), Physical Optics (PO) and Geometrical Theory of Diffraction (GTD) is described. Results for several cases are shown.

Identification of clusters in the fingerprinting method using power measurements

Detection method plays important role in applications of high frequencies techniques for locations systems. One of the most popular techniques is the fingerprinting that operates the relationship between signals. It is considered that in each point in the building has a unique fingerprint or received power by the access points. In this work it was made measurements into an office scenario and it was used cluster identification method to define the fingerprints. Two clustering algorithms, k-means and rek-means was implemented in order to compare both methods.

A Hybrid Technique Based on the Combination of Multilevel Fast Multipole Algorithm and the Geometrical Theory of Diffraction

This paper proposes a hybrid technique for treating electromagnetic problems of scattering and radiation in which the source structure is described as an array of antennas. This strategy is based on the combination of the rigorous method multilevel fast multipole algorithm (MLFMA) and the high frequency technique geometrical theory of diffraction (GTD). Thanks to the use of MLFMA, the source can be discretized into several cubic regions considering each of them as a source point in order to reduce the number of times required to compute the ray tracing when GTD is applied to obtain the scatter field. In this analysis, objects with complex shapes are described by using nonuniform rational B-splines (NURBS) which is a very common way to model geometrical bodies. Numerical results that demonstrate the accuracy and efficiency in terms of CPU time are shown.

Characterization of the Radio Propagation Channel in a Real Scenario

The main goal of this paper is to characterize the radio channel propagation model of studying the impulse response. The observation points have been located along two different areas in the city of Madrid, to analyse LOS and NLOS paths. In order to obtain accurate results the geometry has been modelled with NURBS surfaces, since these allow us to obtain very accurate models of real objects. To perform this work, a deterministic electromagnetic (EM) simulation tool, called NEWFASANT, has been used. This tool is able to achieve this goal applying the Geometrical Theory of Diffraction and taken into account multiple reflections and diffractions between the buildings.

Dynamic Propagation Analysis in Urban Environments

In order to satisfy the demand of the automotive industry about anti-collision systems, related to the protection of pedestrians and drivers, this paper proposes the development of an algorithm that achieves a dynamic analysis of urban scenarios. Typically, some objects of these scenarios can have a translation and/or rotation movement. For each sample of time a new scenario is built according to the information about the movements of the objects. Then, its corresponding simulation is performed using Geometrical Theory of Diffraction to analyse the propagation in outdoor environments and thus, to determine the position of obstacles.

Analysis of Arbitrary Reflector Antennas Applying the Geometrical Theory of Diffraction Together with the Master Points Technique

An efficient approach for the analysis of surface conformed reflector antennas fed arbitrarily is presented. The near field in a large number of sampling points in the aperture of the reflector is obtained applying the Geometrical Theory of Diffraction (GTD). A new technique named Master Points has been developed to reduce the complexity of the ray-tracing computations. The combination of both GTD and Master Points reduces the time requirements of this kind of analysis. To validate the new approach, several reflectors and the effects on the radiation pattern caused by shifting the feed and introducing different obstacles have been considered concerning both simple and complex geometries. The results of these analyses have been compared with the Method of Moments (MoM) results.