V. V. Chebyshev – Dr.Sc. (Eng.), Professor, Head of Department of Technical Electrodynamics and Antennas,

Moscow Technical University of Communication and Informatics

O. I. Yastrebtsova – Post-graduate Student, Moscow Technical University of Communications and Informatics

E-mail: yastrebtsova@rambler.ru

A flat spiral antenna made on the basis of a slot structure can be considered as one of the perspective radiating elements with circular polarization for the phased antenna arrays. From the point of view of construction of broadband phased antenna arrays, these elements have rather good frequency properties, practically the same beamwidth in the orthogonal planes, which determine the scan angle range of the array, and they are characterized by a low-yielding design and small transverse dimensions convenient for placement in the array.

The aim of the work is development of a mathematical model for a phased array as a periodic structure with slot spiral elements that use multilayer dielectrics composing a multilayer substrate and a cover. Also we have carried out numerical analysis of its frequency properties when choosing a spiral topology, parameters of a dielectric multilayer structure, and then determining the spiral dimensions in a phased array antenna. The infinite periodic antenna array has been considered.

The proposed method is based on the inversion of the electrodynamic problem of excitation of a slot spiral with a multilayer dielectric in the unit cell of a periodic array to the integral equation for the spiral magnetic current with its subsequent transformation to the one-dimensional integral Fredholm equation of the first kind. For numerical solution of the obtained equation the self-regularization method is the most suitable as after discretization the equation in the selected set of collocation points it leads to a stable numerical solution of the system of linear algebraic equations because of the predominance of the diagonal elements of the matrix which is due to the singularity of the nucleus.

For the known current of the spiral element of the array its gain and polarization characteristics have been determined, and numerical analysis of the frequency properties of the phased array elements has been performed depending on the choice of the spiral topology, the unit cell of the array and parameters of the multilayer dielectric. The element radiation pattern of the slot spiral determined by the radiation pattern of the unit cell in the free excitation regime is of interest.

Some results of calculations by the proposed method have been presented. It has been shown that special selection of parameters for multilayer structure forming a multilayer substrate and cover of slot spirals in phased antenna arrays, as well as the use of loaded screens with certain surface impedance, allows improving the frequency properties of spirals and reducing height of the screen suspension due to the creation of conditions that prevent the excitation of surface waves which arise in multilayered structure.

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