Yu. I. Choni – Ph.D. (Eng.), Associate Professor,

Kazan National Research Technical University n.a. A.N. Tupolev

E-mail: tchoni@rambler.ru

V. V. Mochalov – Leading Engineer,

JSC “Academician M.F. Reshetnev Information Satellite Systems”; Applicant,

Kazan National Research Technical University n.a. A.N. Tupolev

E-mail: mvv115@mail.ru

The most important element of modern high-capacity satellite communications systems is the large-sized multi-beam hybrid mirror antenna (MHMA), which provides high energy potential. Forming many narrow beams with a width of fractions of a degree, such antennas cover the area within the required boundary. Under operating conditions, the surface of the MHMA reflector undergoes distortion. Even at its low level, this leads to deterioration in the energy coverage of the working areas due to beam displacement and to deterioration in electromagnetic compatibility.

In modern MHMA, clusters of elements of antenna array form beams. This allows you to maintain the nominal state of the beams by adaptive correction of the vectors of the weighting coefficients (VWC) of the clusters. An analysis of the utmost achievable characteristics of MHMA with adaptive control of VWC requires hundreds of multivariate calculations for a number of beams and a set of reflector states. The evaluative nature of such studies makes it unnecessary the use of strict methods of electrodynamics modeling of MHMA, implemented, for example, in the CST Microwave Office software. Additionally, this would be much time-consuming. For these purposes, we used a high-performance algorithm for approximate electrodynamics modeling of large-sized MHMA, the accuracy of which is the subject of this publication.

Permissibility of the simplifications used is due to the following factors. Firstly, the satellite MHMA usually has a long-focus reflector of offset scheme, so there is no need to calculate the diffraction on the antenna array and take into account the depolarization of the field reflected from the reflector. Secondly, the ranges of working angles in elevation angle θ and azimuth φ are limited by ±3,6° and ±1,8°, respectively, which justifies the use of geometric optics in scalar formulation. At the same time, when calculating both radiation patterns and focal spots on the antenna array, the same matrix of transmission coefficients between thousands of reflector points and hundreds of antenna elements appears. Saving this matrix in RAM significantly improves the performance of the corresponding program.

To verify the modeling algorithm and the Delphi program implementing it, comparative calculations have been performed with the Ticra Grasp software, which is a certified and powerful tool for calculating large-sized mirror antennas. The time required to calculate the radiation pattern is the same in both programs. However, in Ticra Grasp it is impossible to calculate directly the focal spots on the antenna array, and their forming from the values of the radiation pattern of all antenna elements in a given direction (θ0, φ0) will take too long.

Due to the noted features of the Ticra Grasp software, the means of verifying is the accuracy of calculating the radiation pattern, which indirectly characterizes the accuracy of calculating focal spots. The comparison results, including those with operational distortions of the reflector surface, showed that the values of the relative mean square error lie in the range from 3% to 10%, which is more than acceptable for estimating the utmost characteristics of the MHMA.

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