Investigation and development of an optimization technique for antenna characterization

The goal of this thesis is to reconstruct with a certain level of accuracy the far-field radiation pattern of an antenna from only amplitude near-field measurements The planar configuration was chosen to acquire the amplitude measurements over two scanning planes located few wavelengths away from the antenna aperture. Since the phase is missing in this context, suitable methods have been investigated and developed to reconstruct the phase of the field from the amplitude data. The Fourier Iterative Algorithm has been implemented to reconstruct the phase from the amplitude data but presents the problem of the strong dependence on the initial guess of the field over the antenna aperture. A Global Optimization technique based on a Genetic Algorithm has been developed to find the initial estimation of the field over the antenna aperture which feeds the iterative technique and the effect of using this global optimization on the accuracy of the reconstructed far-field radiation pattern have been investigated. Apart from that, a technique that combines the Genetic Algorithm and the Fourier Iterative Algorithm has been implemented to reconstruct the phase information from the amplitude data. For the Horn antenna as the antenna under test it has been found that, by implementing the Global Optimization as the method to find the initial condition for the Fourier Iterative Algorithm, no enhancement on the accuracy of the far-field is found. On the other hand, by applying the second method that combines the Genetic Algorithm and the Fourier Iterative technique the improvement of the accuracy of the reconstructed radiation pattern is finally obtained in the region of the main lobe and the secondary lobes.Ingeniería de Telecomunicació