Miniature Coaxial Cables is used to transmit high frequency energy and signals with low loss, with reflection less matching. Characteristic Impedance and Attenuation are important concepts for such transmission. Characteristic Impedance is determined by the ratio of dielectric OD to conductor diameter. It consists of a core conductor, surrounded by pure PTFE dielectric (solid or foamed or air-spaced), covered with a metal shield, and finally encased in an overall jacket. The shield provides the return path and the confinement for RF energy, and is generally grounded. Transmission through coaxial cables is called an unbalanced transmission because the centre conductor and the shield are not reversible.