E. V. Ovchinnikova, Tay Zar Oo

In the base station of third generation of mobile communication antenna system, it is necessary to work on three frequencies or in a wide range of frequencies in each cell. Now-a-day, for the base station of cellular communication of third generation use the planer antenna arrays made by printed antenna system of the second generation are used. Each array has the beam width of 120 degree sector in the horizontal plane and 6 degree in the vertical plane. Although planer antenna arrays have fairly high wind loads, they have been widely distributed. Typical flat antennas are manufactured using printing technology. Printed antennas have certain advantages compared with other types of antennas: low profile, light weight and manufacturing cost, compatibility with integrated circuits. However, the printed antenna has a narrow working bandwidth, for the base station of cellular communication networks of third generation the antenna array is used for each frequency. Placement of the three antennas for each band has significant disadvantages and can lead to overloading the structure. Therefore, the transition of broadband antennas from narrow-band antennas is developed. The main requirement for these antennas are: the beam width of 90, 60 and 45 degrees in horizontal plane, VSWR less than 1.5 in the three frequency range, low weight characteristic and low cost of manufacture. From economic point of view, characteristics of the Vivaldi antenna are matched but the Vivaldi antennas do not get the constant beam width in all frequencies bands. The Vivaldi antenna can get the small change in the beam width, but the optimization of beam width is needed in only in vertical polarization. We need to use reflector not only to get the sector in horizontal polarization, but also to reduce back radiation. Broadband antennas working with a given sector of radiation in three frequencies band in the horizontal plane are designed. Antennas have good weight characteristics and low cost of manufacture. Directivity characteristics of antenna arrays constructed on the basis of such antennas are defined.