Extending the plane wave based Fast Irregular Antenna Field Transformation Algorithm for amplitude-only data

The Fast Irregular Antenna Field Transformation Algorithm (FIAFTA) is extended and employed to construct a near-field far-field transformation algorithm using amplitude-only data. The problem is posed as a minimization of a quadratic functional and it is solved in an iterative fashion using FIAFTA and the nonlinear conjugate gradient method. Since the linear radiation operator inside the nonlinear formulation is evaluated with FIAFTA, its characteristics are inherited and have a beneficial effect when solving the nonlinear problem. Numerical results show the usefulness of the method.