THE FEATURES OF RADIATION FORMATION BY THE SMALL-APERTURE SHF ANTENNAS

摘要

Currently, one of the major problems is to create the broadband individual small-aperture radiators and antenna arrays for wireless local area networks, non-destructive problems, environmental monitoring, biology, medicine etc. Under the conditions when the radiator size is comparable to the operating wavelength, the increasing mutual influence of the individual antenna elements and the increasing role of edge effects in the formation of antenna radiation become principal and require separate and detailed studying. The approach involving the analysis of near-field distributions of the specific individual radiator is realized in the paper in order to explain the features of the radiation formation in the antenna array and planar spiral antenna. The near-field distributions are measured and their analysis is carried out along with the electromagnetic field distributions measured in the far-field domain. The special waveguide probes are used. It is shown that relative to the antenna array electromagnetic waves scattered at the edges of array elements and at the ground plane cause the field intensity oscillations in the main lobe of the radiation pattern and the increase of the cross-component level. As regards the spiral antenna, the differences in the near-field distributions for the orthogonal components lead to a difference in the suitable radiation patterns and to the irregular changes of the axial ratio in the operational frequency band. The proposed approach to the analysis of antenna performance, as well as the presented and tested antennas can be used in designing different wireless communication systems.