The paper deals with the calculation of the electric field strength distribution of a circular antenna focused in the Fresnel zone. To express the electric field strength distributionnWv−1(w, x) functions defined by Lommel functions of two variables are used. On the basis of the calculated electric field strength distribution the fundamental properties of an antenna focused in the Fresnel zone are determined. The width and depth of the focused beam are calculated and the results of the numerical computations are plotted. Formulae for determining the wavelengths in the focused beam are expressed as a function of the circular aperture illumination.