A study of near-field imaging and diagnostic applications of surface equivalent current methods

The utilization of surface equivalent current (SEC) methods in near-field imaging and diagnostics of flat scatterers with fine details is discussed. Of special interest is the ability to identify and locate electrically small physical changes on the scatterers by analyzing the equivalent surface current densities obtained by transforming the observed near fields. Using two test objects as scattering targets for an incident plane wave at 77 GHz, it is shown that sub-wavelength physical changes can even be localized using SEC methods. Finally, the need for an appropriate excitation method and measurement setup is discussed in the light of experimental results.