Sarmal Antenlerin Boyutlarının Küçültülmesi

Abstract

Helical antennas are generally an easy to design type of antenna. These antenna types, which are designed for wire bending, can have circular polarization, so that their polarization can be represented by two linear components perpendicular to each other. On this side, they can receive signals from both antennas with horizontal and vertical polarization and the ability to receive signals from Faraday rotation has increased its use in satellite and radio communications. The helical type antennas which can be designed with different geometries have various advantages and disadvantages in terms of both physical properties and performances compared to each other. Different width, length and geometry can be used according to the desired antenna characteristics.. Quadrifilar helical, spiro helical, spherical helical are some of the different helical antenna types. The physical obstacles at the places of use of the helical type antennas reveal the question of whether a lower volume antenna can be made with similar performance. As a result of the studies, various methods have been developed and improvements in antenna volume have been realized. Some of these methods, which are effective in different frequency bands, have also been effective in the L band in which the study was conducted.

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In situations where there is no physical obstacle to the antenna volume, it is aimed to achieve maximum performance in the desired direction. In this respect, methods that provide various improvements in antenna gain, bandwidth, polarization, return losses are effectively used. At the top of these methods is to change the antenna geometry. In the thesis, it is aimed to obtain the best results by trying different helical type antennas. Methods such as bending the antenna to have multiple pitch angles (double pitch method), changing the geometry of the antenna ground plane and creating slots on the surface (DGS method), wrapping the antenna around the dielectric cylinder, and adding metal plates or rings to the antenna at the end of the antenna have been studied in the thesis for the L band. As a result, different designs have been realized and the antenna size has been reduced by 20% compared to the conventional helical antennas, a lower axial ratio has been achieved in the wider frequency band, polarization improvement has been achieved, antenna gain has improved to nearly 30%, wider HPBW has been achieved and input impedance is more easily matched.