%X In this report, a two step strategy for the inversion of amplitude-only data in microwave imaging applications is analyzed. At the first step of the proposed method, the illuminating source is synthesized according to a line sources model in order to compute the incident field in the investigation domain starting from the values available in the measurement domain. The second step is aimed at reconstructing the profile of the objects under test thanks to the iterative multi-scaling approach integrated with the Particle Swarm Optimizer, an effective evolutionary minimization technique. The reconstruction accuracy of the proposed phaseless retrieval strategy is analyzed using synthetic data concerned with a multiple scatterer configuration and successively further assessed inverting experimental data %D 2008 %A Andrea Massa %A Laboratory ELEDIA %I University of Trento %L elediasc12527 %T Microwave Imaging from Amplitude-Only Data–Advantages and Open Problems of a Two-Step Multi-resolution Strategy