Contribución a la transformación en sistemas cilíndricos de campo próximo a campo lejano. Análisis de errores mecánicos y eléctricos y reconstrucción de campo

Resumo

Abstract Long there is interest in developing a mathematical formulation that allows the properties of radiation energy by an antenna or an array of antennas from the area close to them to remote areas. This interest has resulted from demands of very precise measures to develop high performance antennas, improved methods for analyzing them and by the impossibility of measuring large antennas directly into electric far field. The problem of radiation consists of generic electromagnetic fields to find some external sources that are contained in a certain region of space. The use of the modal formulation allows expressing the radiated fields as the superposition of elementary plane waves, cylindrical or spherical. Thus the problem of radiation is reduced to obtain the complex amplitudes of each of the elementary waves that give rise to overlapping fields radiated. Employment expansions and manners come at which their application is limited to cases that contain canonical shapes, however its application to solve any electromagnetic problem. These complex amplitudes or modal coefficients completely describe the fields and with the advantage that allows a finite set of scalar values, it is possible to obtain the radiated fields at any point in space. The spatial dependence of the fields is given by wave functions which are solutions of the wave equation by separation of variables in the system. The properties of wave functions allow the spectral formulation is particularly well suited to the treatment of electromagnetic problems that are involved in areas that are defined by one or more constant coordinates in the coordinate system used. The influence of measurement errors on the radiation patterns is important when measuring antennas with very strict specifications on positioning the main beam and side lobes level. It is important to the study of measurement errors in near-field in cylindrical coordinates where possible to standardize the specification of a measurement range, providing expressions that relate the error in near-field and its effect on the far field. The first chapter on the introduction makes a brief description of the theory of radiation from the antennas, is the mathematical formula of the theory of electromagnetic fields is described briefly, the physical quantities of vector fields, described by Maxwell equations that explain electromagnetic phenomena, allowing to predict the electromagnetic fields generated anywhere in the environment, in addition to relating the electric and magnetic fields with the charges and currents that are created. The second chapter investigates, describes and explains the cylindrical surface of measurement used to transform the near-field calculated on the same far-field. It investigates and describes the method to carry out the transformation of the near-field far-field, based on the theory of wave equation in cylindrical coordinates and decaying modes of the field after the application of reciprocity theorem Lorentz. Under the method of correction of antenna probe to prevent the effect of radiation affects the radiation from the antenna under test, thereby distorting the resulting field to be obtained. In the third and fourth chapters are explained and simulate electrical and mechanical errors. It mentions some automation techniques to avoid positioning errors mechanical or electrical failure in the electrical analysis of errors, we have generalized this idea due to possible errors in judgments of food dishes, or failures by positioning, we have shown through simulations making comparisons between the radiation patterns, thus, reference standards of proper operation. In the fifth chapter, based on the three-dimensional vector cylindrical wave expansion of an electromagnetic field, and the characteristics of the orthogonal modes and the coefficients of the expansion modes, is rebuilt the next field. The method of the field distribution is described in this chapter allows to calculate the near field on a cylinder of any measure. It has also been widespread method that avoids the truncation errors by calculating the near field on an infinite cylindrical surface ideally from field measured on the cylindrical surface with a known dimension.