Self-Dual Wideband Absorbers

Self-dual balanced structures, comprising finite electric and magnetic regions, are invariant to 90 degrees rotation if electric and magnetic regions are interchanged with the rotation. Such structures will produce no backscattering when subject to plane wave illumination along the axis of rotation provided that the Weston balanced condition ϵ
_r
= μ
_r
is obeyed. When higher order spatial harmonics are suppressed, e.g. in a periodic structure whose unit cell is smaller than the wavelength, the entire incident power is forced to be transmitted through the structure. With proper design, this phenomenon can be exploited to produce absorbers over a wide range of frequencies, provided that the constitutive parameters adhere to the Weston condition throughout this range.