R.R. Nizamutdinov, O.V. Potapova, Yu.E. Sedelnikov

Exciting wave fields systems focused of Frenel zone are extensively used in a some technical areas. Focused systems may be present as antennas arrays or virtual synthetic aperture. However, characteristics of spatial distribution of wave fields, focused within lossed material are not studed sufficiently. In this article aperture antennas focused within lossed medium in the Fresnel zone at distances commensurable to aperture size are searched. Focusing effect realizing by approach faze allocation of exciting current. The spatial distributing of wave field nearby focusing point are present relatively thin maximum with few intensive maximums corresponding sidelobes in a directional pattern. Measurement of focused area and sidelobe level are depend on many factors and considerably differ from far-field zone. There are investigation of directive gain in Frenel zone in this paper. Demonstrate the limit of maximum value of directive gain that correspond optimal aperture size. Value of directive gain are depend on relative focusing size, attenuation in material reduce the directive gain. The measurements of focused area and sidelobe levels in loss-free medium are depend compound on electrical size apertures, relative focusing size and form of amplitude allocation of exciting current. Attenuation in material have an impact both on measurements of focused area and sidelobe levels. Heavy lossed decrement of focused effect. Thereby focused antenna systems are very perspective for applications with spatial selective excitation of wave fields at areas adjoining to aperture.