“…For example, the BPFs in [2,3,9] are not planar implementation, i.e., defected ground structure is employed in [2], while multilayer structure is utilized in [3] and [9], which makes the fabrication procedure more complex. Two or more resonators are utilized in the multiband BPFs proposed in [6,8,12,13], which leads to large circuit size. Besides, to the authors' knowledge, very few works about the resonating structure which can be utilized for both wideband and multiband BPFs are reported.…”