An Electromagnetic Bandgap device, comprising: a first substantially planar substrate having an upper surface and a lower surface; a plurality of discrete vias comprising conducting material and extending from said lower surface of said first substantially planar substrate through said first substantially planar substrate to said upper surface of said first substantially planar substrate, a plurality of said vias having conducting material exposed on said upper surface of said first substantially planar substrate, said plurality of vias forming a periodic lattice in said first substantially planar substrate; a second substantially planar substrate having an upper surface and a lower surface, said second substantially planar substrate located adjacent to said first substantially planar substrate such that the lower surface of said second substantially planar substrate is in contact with the upper surface of said first substantially planar substrate; and a plurality of vias comprising conducting material and extending from said lower surface of said second substantially planar substrate through said second substantially planar substrate to said upper surface of said second substantially planar substrate, a plurality of said vias having conducting material exposed on said upper and lower surfaces of said second substantially planar substrate, said plurality of vias forming a periodic lattice in said second substantially planar substrate, wherein said first and second substantially planar substrates (72,76) are aligned such that conducting material of the lower surfaces of a plurality of vias of said second substantially planar substrate is in contact with conducting material of the upper surfaces of a plurality of vias of said first substantially planar substrate; further comprising a ground plane positioned on the upper surface of said second substantially planar substrate, said ground plane in contact with conducting material of the upper surfaces of a plurality of vias of said second substantially planar substrate, further comprising a coplanar waveguide (84,86) positioned in at least one of said second substantially planar substrate and said ground plane characterised in that said vias of said first substantially planar substrate have essentially the same shape and size, and wherein said vias of said second substantially planar substrate have essentially the same shape and size, and wherein the size of said vias of said first substantially planar substrate is greater than the size of said vias of said second substantially planar substrate. a first substantially planar substrate having an upper surface and a lower surface; a plurality of discrete vias comprising conducting material and extending from said lower surface of said first substantially planar substrate through said first substantially planar substrate to said upper surface of said first substantially planar substrate, a plurality of said vias having conducting material exposed on said upper surface of said first substantially planar substrate, said plurality of vias forming a periodic lattice in said first substantially planar substrate; a second substantially planar substrate having an upper surface and a lower surface, said second substantially planar substrate located adjacent to said first substantially planar substrate such that the lower surface of said second substantially planar substrate is in contact with the upper surface of said first substantially planar substrate; and a plurality of vias comprising conducting material and extending from said lower surface of said second substantially planar substrate through said second substantially planar substrate to said upper surface of said second substantially planar substrate, a plurality of said vias having conducting material exposed on said upper and lower surfaces of said second substantially planar substrate, said plurality of vias forming a periodic lattice in said second substantially planar substrate, wherein said first and second substantially planar substrates (72,76) are aligned such that conducting material of the lower surfaces of a plurality of vias of said second substantially planar substrate is in contact with conducting material of the upper surfaces of a plurality of vias of said first substantially planar substrate; further comprising a ground plane positioned on the upper surface of said second substantially planar substrate, said ground plane in contact with conducting material of the upper surfaces of a plurality of vias of said second substantially planar substrate, further comprising a coplanar waveguide (84,86) positioned in at least one of said second substantially planar substrate and said ground plane characterised in that said vias of said first substantially planar substrate have essentially the same shape and size, and wherein said vias of said second substantially planar substrate have essentially the same shape and size, and wherein the size of said vias of said first substantially planar substrate is greater than the size of said vias of said second substantially planar substrate.