The aim of the thesis entitled "Study of the Ultra Wide Band (UWB) frequency of signal attenuation energy during propagation in biological tissue" is to determine the frequency of a UWB (Ultra Wide Band) wave that can pass through biological tissue with limited losses and deformations. The human body is modeled by four semi-infinite layers: fat, muscle, cartilage and lung. Each is characterized by its thickness, relative dielectric constant and conductivity, localized at a limited distance from the source. The source is a simple, flat, uniform Gaussian pulse arriving normally at the sample surface.