Equivalent Permittivity Analysis for Periodic Wedge -- Type Absorber Using Transmission Mode Approximation.

To obtain a matching over a wide frequency range, pyramid-type and wedge-type matching layers are used in front of the multilayered wave absorbers. In this paper, a transmission mode approximation is proposed in which the period of the wedges and the incident polarization direction are taken into account in the calculation of the characteristics of a wedge-type wave absorber. The degree of difference of the equivalent permittivity derived by the propagation mode approximation from the one by the conventional method (corresponding to the low-frequency limit) is presented by numerical calculations. It is also shown that there is a difference from the wave absorber characteristics derived by the conventional method even at a wavelength longer than the wedge period. The tendency of the reflection to increase at the higher frequency side is visually explained by replacing it with the taper shape. [ABSTRACT FROM AUTHOR]