c 2 c 3 through c n can be changed by varying the control voltages applied to the dielectric slabs that contain tunable ferroelectric material the overall capacitance of the laminated structure is the sum of the capacitance of the individual slabs 0026 fig4 is an end view of an alternative embodiment of the invention for tunable coaxial cable applications in which the dielectric material is arranged in concentric cylinders 56 58 60 and 62 here again some of the layers of dielectric material can be tunable material having relatively high dielectric constants low losses and high tunability while the other layers can be tunable or non tunable material concentric cylindrical electrodes 64 66 68 and 70 are positioned between the dielectric materials so that a bias voltage can be applied to the control the dielectric constants of the dielectric cylinders that contain tunable ferroelectric material a metallic center conductor 72 and a cylindrical metallic ground 74 are provided to carry the rf signal through the cable 0027 fig5 is a cross sectional view of the structure of fig4 taken along line 5 5 one of the controllable dc voltage sources is shown to be connected to electrodes 68 and 70 additional controllable voltage sources not shown would be used for applying bias voltages to other electrodes that lie adjacent to the internal and.