Bandwidth enhancement of folded dipole-based microwave absorber surface

A folded dipole is known as a classical wideband antenna and usually analyzed by decomposing into two coupling modes: dipole mode and twin-lead stub mode, which can be seen as an effective 2-pole filter. A wideband microwave absorber surface can be formed by an array of receiving folded dipoles backed by a ground at λ/4, since the combination of the twin modes of folded dipole and the third coupling mode of λ/4 ground can achieve a 3-pole filter. To further broaden the bandwidth of the folded dipole-based absorber, some improvements from two aspects are made on the structures, saying from the element itself and the arrangement of the elements, and then three kinds of folded dipole-based absorbers are proposed in this work. The numerical results show that, all the three kinds of folded dipole-based absorbers above can have a wide relative bandwidth over 100%; especially the one with top-triangle loaded folded dipole absorber surface can even obtain a relative bandwidth of 120%. Besides, by arranging the broadside-folded dipole elements with regular triangle-lattice cells, the bandwidth can be further enhanced and the sensitivity to the oblique incident waves is also decreased.