Radio-frequency field distribution incident on a finite size thin metamaterial absorber

A finite size thin metamaterial absorber is used to measure the field distributions incident on its surface. Absorption is realized by lumped resistors interconnecting the surface patches arranged on a grounded substrate at the resonance frequency of the absorber structure. The 2-d distributions of the absorbed power and electric field distributions are obtained by measuring the voltages induced on the lumped resistors. When using a finite size absorber, the measurement accuracy is degraded over the entire surface because of edge scattering, which creates an interference pattern due to a scattered wave overlapping with the incident wave. It is shown that the edge scattering can be suppressed by removing the part of patches at the edges which does not contribute to incident wave absorption from the viewpoint of receiving cross-section. Suppression of edge scattering is achieved for the incident waves with a single polarization as well as with both polarizations. This technique should be useful to accurately measure the incident field distributions absorbed by a thin metamaterial absorber.