S. N. Boyko - Ph.D. (Phys.-Math.), Director of Department of "ISDE" Co. Ltd. E-mail: npk6@mail.ru
S. V. Kosyakin - Ph.D. (Eng.), Head of Department of "ISDE" Co. Ltd.
D. A. Koshevoy - Head of Group, "ISDE" Co. Ltd.
A. S. Kukharenko - Ph.D. (Eng.), Senior Research Scientist, "ISDE" Co. Ltd.
Yu. S. Yaskin - Ph.D. (Eng.), Director of "ISDE" Co. Ltd.

Errors, which occur during antenna radiation pattern measurements in conditions of limited space, are observed. An error, caused by mutual coupling between measuring and measured antennas is less investigated among them. A reason of the error is partly energy diffraction on receiving and transmitting antennas, because of which the signal in receiving antenna is a sum of a source signal and mutual electromagnetic wave diffractions. A mathematical analysis of mutual coupling dependence on distance between antennas, antenna element-s effective reflective surface and source signal incidence angle is made. The result of this analysis is the equations for measuring error evaluation. An analysis of measuring error dependence on measured antenna ground plane diameter, marked in wave lengths, in case of different angles of incidence and different distances between measured and measuring antennas has been carried out using the obtained equations . The analysis showed that the measured antenna ground plane size should be decreased and the distance between antennas should be increased to minimize the measuring errors, caused by mutual coupling between antennas. Graphs for self evaluating of measuring error and for choosing the optimal distance between antennas for organizing a measuring stand are presented. Data of antenna radiation pattern measuring on the frequency 406 MHz, with antenna ground plane diameters 2,5, 1,0 and 0,5 m and distance between antennas 3 m have been presented. These data show that measuring error is minimal in case of minimal measured antenna ground plane diameter, what confirms the mathematical model legality. Recommendations, based on mathematical model, for organizing the stand for antenna radiation pattern measuring in conditions of limited space, which allows minimizing the measuring error, caused by mutual antenna coupling, have been given. An example of a measuring stand, designed according to the given recommendations, has been presented presented.