Theoretical investigation on wideband folded dipole microwave absorber using filtering concept

A microwave absorber constructed by an array of the folded dipole with resistive loads and backed by a ground plane with distance from λ/8 to λ/4 are investigated. The admittance of a folded dipole shows that it is actually a two-port filter which is adjustable by changing the radii and the separation between the two lines of the folded dipole, and therefore can improve the bandwidth of unfolded dipole absorber. Comparing to the absorber with unfolded dipole array, the bandwidth can be broadened by 200% with unequal radii of two lines, and the thickness can be decreased by 25%. The operating frequency of the improved dipole absorber is f₀ = 10 GHz and is constructed on substrate with dielectric constant 2.65.