The present invention relates to a tunable microwave/millimeter-wave arrangement comprising a tunable impedance surface. It comprises an Electromagnetic Bandgap Structure (EBG) (Photonic Bandgap Structure) comprising at least one tunable ferroelectric layer (3), at least one first, top, metal layer (1) and at least one second metal layer (2A, 2B). Said first (1) and second metal layers (2A) are disposed on opposite sides of the/a ferroelectric layer (3), and at least the first, top, metal layer (1) is patterned and the dielectric permittivity of the at least one ferroelectric layer (3) is dependent on a DC biasing voltage directly or indirectly applied to first (1) and/or second (2A, 2B) metal layers disposed on different sides of the/a ferroelectric layer.