Graphene-metal based tunable band-pass filters in the terahertz band

The authors propose the concept, analysis, and design of frequency tunable band-pass filters operating in the terahertz band. The proposed structure is composed of two metal tapped line and five metal-contacted graphene hairpin resonators transferred onto a dielectric. This structure implements low insertion loss and frequency tunability by adequately controlling DC bias applied on the graphene. An efficient synthesis method has been presented, through combining classical microwave filter theory and the electrical properties of graphene. The theoretical and extracted resonance frequency of resonator (f(0)), external quality factor (Q(E)) and coupling coefficient (K-ij) are utilised to determine the filter circuit dimensions. Then the authors proposed two examples with different operating bandwidths to validate the theoretical design. The potentially high losses of graphene is also evaluated.