Optimization-based reconstruction of electromagnetic fields from UAV measurements

In this abstract I briefly describe my six months thesis, carried out at LINKS-foundation and at CNR, under the supervision of my tutor Dr Righero Marco. The main argument of the thesis is to perform a near-field to far-field transformation of the electromagnetic field radiated by array of antennae, starting from the measurement of some samples taken in the near field of the scattering object. There are two main challenging scenarios: the former is given by the fact the near field samples are measured in external enviroment by means of a quadrotor; the latter is a consequence of the first one: in order to minimize the time flight of the quadrotor, it is performed an under-sampling of the near field, i.e. it is measured only in a few points, less than required by the Nyquist’s criteria according to the electric size of the scattering object. Starting from several articles, I exploited different techniques of the reconstruction of the near field of electromagnetic field, but, unlikely the articles, the points where the near field is measured are not selected randomly but they belong to a deterministic path that can describe a 2D flight of the drone; these techniques relies on the minimization of the nuclear norm of the matrix that collects the values of the near field samples taken on an uniform observation grid. Once that the best method for the reconstruction of the near field has been selected, the successive step was to pass from the measured near field to the computed far field; the intermediate step was the computation of the equivalent electric currents on a generic surface that encloses the scattering object. From these equivalent electric currents, it is possible to compute the radiated far field. At this stage, I examined the best trajectory of the quadrotor in the near field in order to achieve better results in far field. The thesis ends with a conclusive analysis of the activity carried out and what are the possible future developments.