V.A. Neganov - Dr. Sc. (Phys.-Math.), Professor, Head of Department, Volga State University of Telecommunications and Informatics (Samara) E-mail: neganov-samara@yandex.ru D.P. Tabakov - Ph. D. (Phys.-Math.), Associate Professor, Volga State University of Telecommunications and Informatics (Samara) E-mail: illuminator84@yandex.ru S.B. Filippov - Head of Rroject-to-Construction Group of Antenna-Feeder Devices, JSC «SRC «Progress» (Samara) E-mail: fsb-progress@yandex.ru A.S. Maltsev - Design Engineer, Project-to-Construction Group of Antenna-Feeder Devices, JSC «SRC «Progress» (Samara) E-mail: fsb-progress@yandex.ru

In this article is about Spiral antenna (SA), which designed for transmission of telemetry from onboard control system of the small spacecraft «AIST 2» on terrestrial stations in a mode of the oriented flight. The advantage of two-armed logospiral antennas is greater stability of their parameters and characteristics on the frequency range. Directivity pattern (DP) of such antennas can be calculated if we know the distribution of current on the spiral elements. As a rule, development of the spiral antenna which would provide necessary characteristics, begins with calculations under engineering formulas according to which spiral antennas are considered in the various approximations based on the physicist of happening processes. The main lack of such approach is low level of results equivalence of real measurements to the theoretical calculations. Therefore, the development of the SA it was decided to build a more strict mathematical model of the antenna, based on integral representation of the electromagnetic field, that is going over to integral equations relatively to unknown currents while the inner electromagnetic task is solved. As a result the mathematical model two-armed equiangular conical spiral antenna with a fine-wire reflector of the finite sizes has been developed. Within the model it is possible to change number of coils of a spiral, diameter of peak and the cone base, width of spiral entrances, density of a grid of a reflector and type of excitation of the antenna. Results of calculations and measurements of normalized amplitude direction characteristics for two pre-production models of antennas are shown. As a whole good enough coincidence of results of experiment to results of calculations is watched. It is found that the increasing the size of the SA screen with selected geometry and fixed frequency in the case of antiphase excitation leads to the collapse of DC, and in the case of in-phase excitation - to additional petals in DC. Disadvantages of the mathematical model should be noted that increasing of the size of the screen very quickly increases the total number of segments, and consequently the square of the number of segments increases the dimension of the impedance matrix. Therefore, in the future we plan to develop the model of the screen using a variety of options: pojection of the current distribution on thin-wire screen elements in the basis, reduces the size of solvable linear algebraic equation, the transition to the solid model of the screen on the basis of two-dimensional singular integral equations, or the development of a model circular screen, two-dimensional diffraction problem on which can be reduced to a set of one-dimensional tasks concerning the Fourier harmonics of the current distribution.

 

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