A tuneable impedance surface for steering and/or focusing a radio frequency beam. The tunablesurface comprises a ground plane; a first plurality of elements disposed in an array a firstdistance from the ground plane, the distance being less than a wavelength of the radio frequencybeam; and a second plurality of elements disposed in an array for controlling the capacitance between the elements of the first array. The second plurality of elements include, in one embodiment, variable discrete capacitors and, in another embodiment, a plurality of platesarranged to be moveable relative to the first plurality of elements.