Pattern reconstruction from distorted incident wave measurements

This work deals with the question of antenna response to a non-planar incidence, and with methods facilitating the extraction of the desired far-field pattern. The primary objective is to allow antenna measurements to be carried out under non-ideal conditions. Far-field antenna measurements are standardly performed with the antenna, operating in its receiving mode, excited by an incident plane wave. All of the antenna\´s far-field characterizing parameters are defined with respect to its plane wave response. The generation of an uncorrupted plane wave often becomes a rather difficult and at times logistically impossible task. Such difficulties are encountered in conventional ranges (insufficient range, ground and other multipath effects, etc.), in compact ranges (phase front distortions due to edge diffraction and reflector imperfections, "stray radiation", etc.), and are bound to reappear regardless of the measurement method. Much effort, ingenuity and expense must be and has been invested in the attempts to achieve desired plane wave excitations of sufficient purity. The conceptually straightforward data processing techniques proposed in this research, although limited to one-dimensional phase-front distortions, will greatly reduce the need to accurately realize a planar phase front. The processing is not only conceptually simple, but it is efficient owing to the use of the FFT algorithm combined with appropriate numerical filtering techniques which help reduce the required sampling rates to acceptable levels. It is emphasized that the proposed approach facilitates a complete reconstruction of the far-field including polarization data. The proposed concepts and the computational accuracy and efficiency were tested by computer simulation.