Abstrakt

Conformal antennas are becoming popular due to their many advantages and possibilities of applications they offer. The advantages of using antennas with a curved surface arise not only from the possibility of integrating them with the object on which they are mounted on but also from the increase, relatively to planar antennas, of their visible angular range. The circular antenna arrays, or arrays of radiators located on the surface of a cylinder may be the examples of such antenna that provide omnidirectional radiation patterns in azimuth plane or provide, in this plane, the possibility of beam control. Such antennas can be used e.g. in base stations for mobile communications systems.In the analysis of conformal antennas one encounters the electromagnetic problem which consists in finding the electromagnetic field resulting from radiation sources placed on curved surfaces. It is a boundary problem, where the fields in the area outside antenna surface and the fields or current distribution on the radiating elements have to be matched. Determination of radiation characteristics is reduced to finding the electromagnetic field in the antenna far zone. For this case, the simplified relations are often used. Determination of the mutual-couplings between the radiators requires finding the fields in the antenna near zone and is therefore more difficult issue, because no simplifications can be utilized. The inclusion of mutual-coupling effect is of great importance in pattern synthesis problems, where if the mutual-coupling is neglected, poor results are obtained especially in the shaped beam region. The microstrip Ultra Wideband (UWB) antennas are very attractive to short pulse technology and have been proposed for wireless communication systems to transmit coded signals. Their compact and simple structures with small dimensions and light weight are suitable for easy integration with system components of phased and active antenna arrays. The analysis of UWB microstrip antennas mounted on a circular cylinder is being conducted in the paper. The influence of curvature of the antennas on their reflection coefficients and radiation patterns is investigated and the comparison between planar and conformal radiators is made. A commercial softwares are used to design the UWB radiators and investigate the influence of the curvature.

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