An innovative phase retrieval technique from single-plane near-field intensity by a dielectric slab

This paper deals with a novel technique to determine the far field of a radiating system from near-field intensity data. In particular, the approach exploits two measurements of the intensity of the near field over the same scanning plane. The diversity between the two intensity data sets is achieved by ensuring different conditions of the near-field propagation between the aperture and the measurement plane. In particular, one measurement is performed with free-space propagation while the second one is performed by exploiting a dielectric slab with known properties filling partly the space between the aperture and the measurement plane. Then a phase retrieval algorithm, that faces a nonlinear inverse problem, is solved by assuming as unknown the plane wave spectrum (PWS) of the field. The role of the parameters of the dielectric slab are discussed in ensuring the reliability of the phase retrieval solution algorithm. Finally, the feasibility of the novel approach is presented also compared to the usual near-field phase retrieval technique exploiting measurements of the intensity of the near field over two scanning planes.