LOW-PROFILE CIRCULARLY POLARIZED TIGHTLY COUPLED DIPOLE ARRAY

Abstract

The design of a low-profile antenna array of tightly coupled circularly polarized dipoles is considered.
The main design detail is two crossed printed dipoles. Quadrature excitation is provided by arcshaped
strips connecting pairs of orthogonally located arms on the upper and lower metallization layers.
To ensure capacitive coupling between the elements, metal disks are used, galvanically connected to the
base using metal rods. To expand the operating frequency band and improve the radiation characteristics
of the antenna array, a matching layer of Eccostock HiK plastic is located directly above the dipoles. The
results of a numerical study of the characteristics of an elementary cell of an antenna array with periodic
boundary conditions on the faces in the ANSYS HFSS software are presented. The possibility of operating
in a wide frequency band at a given level of matching and ellipticity coefficient is demonstrated. The dependence
of the matching characteristics and the ellipticity coefficient on the size of the strip that provides
quadrature power to the dipole arms is shown. It was established by calculation that the choice of the strip
radius, which ensures quadrature excitation of the dipole arms, is a compromise between a wide operating
frequency band and a better ellipticity coefficient in the center of the range. It is shown that the use of a
matching layer located directly above the dipole layer in arrays of tightly coupled circularly polarized
dipoles ensured matching over a wide frequency band while maintaining an electrically low profile height.
Based on the proposed element, models of finite antenna arrays of 3×3, 4×4, 5×5 and 6×6 elements have
been developed. The influence of elements located at the edges on the characteristics of the antenna array
is shown. The possibility of improving performance by connecting the outermost elements to matched
loads was investigated.