Lorena Lozano

Fast ray-tracing for computing n-bounces between curved surfaces

A new ray-tracing method has been developed for the analysis of antennas on-board complex structures and to compute the propagation at indoor/outdoor environments considering n-bounces. The structures (satellites, ships, aircrafts, etc.) are modeled by planar and/or curved surfaces defined by perfectly electrical conductors or dielectric materials (with or without losses). The structures are defined as parametric surfaces, in particular by NURBS (Non-Uniform Rational B-Spline) surfaces. The approach is based on the Uniform Theory of Diffraction (UTD) for the field computation.

New version of FASANT code

This paper presents an overview of the new FASANT code based on a combination of the uniform theory of diffraction (UTD) and physical optics (PO). This code is a powerful tool to analyze the radiation pattern of antennas on board in complex structures in an easy way. The structures must be electrically large and can be modeled by flat and/or curved surfaces defined by perfect electrical conductors or dielectric materials. This code has been validated using several complex test cases, showing good agreement between simulations and measurements.

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.

Iterative PO method based on currents modes and angular Z-buffer technique

An efficient scheme based on physical optics (PO), the angular Z-buffer (AZB) technique and the volumetric space partitioning (SVP) algorithms for computing the RCS of large and complex bodies is presented. An iterative process to calculate multiple interactions between patches has been considered. Ray-tracing acceleration techniques, like the angular Z-buffer has been applied to reduce the CPU-time

Application of matrix pencil to obtain the current modes on electrically large bodies

The matrix pencil method, in combination with an interpolation using nonuniform rational bi-spline surfaces, is applied for the expansion of the induced currents on complex bodies in terms of current-modes. The approach is useful for solving electrically large problems of radiation or scattering using physical optics with one or more bounces. The techniques presented in this paper can be also useful to improve some rigorous methods

AN EFFICIENT HYBRID-SCHEME COMBINING THE CHARACTERISTIC BASIS FUNCTION METHOD AND THE MULTILEVEL FAST MULTIPOLE ALGORITHM FOR SOLVING BISTATIC RCS AND RADIATION PROBLEMS

A numerically e-cient approach for the rigorous compu- tation of bi-static scattering and radiation problems is presented. The approach is based on an improvement of a previous method scheme that combines the Characteristic Basis Function Method (CBFM) and the Multilevel Fast Multipole Algorithm (MLFMA). The approach com- bines Characteristic Basis Functions (CBFS) and subdomains func- tions for reducing the CPU time in the pre-process and in the solving iterative process for simple or multiple excitations. It is intended for use in very large cases where an iterative solution process cannot be avoided, even considering the matrix size reduction achieved by the CBFM. This reduction is particularly important for solving radiation or bistatic problems in which an integral equation is solved once.

Efficient RCS analysis of complex targets on infinite ground plane

An approach for computing efficiently monostatic and/or bistatic radar cross section of complex target on an infinite perfect electric conductor or dielectric ground plane is presented. The approach is based on Physical Optics and Equivalent Currents Method together with the Image Theory. The last one is used to obtain the scattering from the target above the ground plane, avoiding to model the infinite ground plane. In order to consider realistic targets composed of dielectric or perfect electric conductor, they are modeled by parametric surfaces (NURBS).

Improvements in ray-tracing acceleration techniques to compute diffraction effect and doubles and triples effects in the RCS prediction of complex targets

The paper presents several improvements in ray-tracing acceleration techniques to compute diffraction and doubles and triples effects in the RCS (radar cross section) as fast as possible and minimize the use of computer memory. The approach is based on the application of the angular Z-buffer (AZB) algorithm together with the SVP (space volumetric partitioning) algorithm, for electrically large and complex bodies modelled by a high number of flat and/or curved surfaces.

Ray-tracing acceleration techniques to compute RCS of complex targets

A combination of acceleration techniques to compute the RCS (radar cross section) of complex targets is presented. The approach is based on the application of the angular Z-buffer (AZB) algorithm together with the SVP (space volumetric partitioning) algorithm, for electrically large and complex bodies modeled by a high number of flat and/or curved surfaces.

A new ray-tracing acceleration technique for radio propagation

Since site measurements are costly, propagation models have been developed as a convenient, adequate, and low-cost alternative to design personal communication systems, such as mobile phone. With the rapid advance in computing, ray-tracing techniques have become one of the most popular methods for characterizing the radio propagation in different environments. These techniques are attractive due to its high accuracy in dense urban areas [1]-[3] and indoor environments [4]. The disadvantage of ray-tracing method is the large computational cost that may be inappropriate in complex environments. For this reason, it is necessary to use efficient propagation models and ray-tracing acceleration techniques [5].