A ball-and-stick model that illustrates the connectivity of the network. A tight-binding model can be defined when hopping constants are specified for the bonds connecting the sites. (a) A 3D view of the tight-binding model. The A sites and B sites are sublattice sites of a hexagonal lattice in the x-y directions. (b) The 3D model is compressed onto a 2D plane and is realized by transmission lines. The dashed circles mean that a meta-atom is composed of three nodes. (c) Additional transmission lines are added to the nodes to tune the onsite energies.