Field distribution measurement and source estimation using metamaterial absorber

Two-dimensional amplitude and phase distributions of radio-frequency waves are measured by a thin metamaterial absorber, which is composed of a mushroom-type metasurface formed on a grounded substrate. A number of lumped resistors interconnecting the square metal patches on the surface absorb the incident waves and work as a dense array of dipole sensors. Measured field distributions are used to estimate the direction-of-arrivals of far-field plane waves, as well as to localize the spherical wave sources in the radiating near-field region. In this study, the location and orientation of a radiating near-field source at a few GHz is estimated by applying a MUSIC technique on the field distributions measured on the absorber surface. The technique is shown to be effective to localize the dipole source of a spherical wave illuminating the absorber surface.