ВЛИЯНИЕ РАБОЧЕЙ ЧАСТОТЫ И ТОЛЩИНЫ ПОКРЫТИЯ НА ХАРАКТЕРИСТИКИ ИЗОЛИРОВАННОЙ СФЕРИЧЕСКОЙ ЩЕЛЕВОЙ АНТЕННЫ В ПЛАЗМЕ
Authors: Даутов О.Ш. , Аль-Абади М. С. 
Published: February 2025

С помощью строгой модели, полученной на основе метода интегро-функциональных уравнений и приложения MathCad, анализируются направленные свойства покрытой слоем диэлектрика сферической щелевой антенны, окружённой плазмой. Исследуется зависимость диаграммы направленности от частоты и влияние толщины диэлектрического покрытия на характеристики излучения. В рассматриваемом диапазоне частот диаграмма направленности изменяется незначительно, и данная антенна может использоваться в качестве широкополосной. Отмечено значительное влияние толщины диэлектрика на направленные свойства и уровень излучения.

Introduction. The aircraft antenna is coated with a layer of dielectric to protect it from weather, temperature and aerodynamic effects, and may be surrounded by a layer of plasma that is specially created near the aircraft to protect it from radar detection. Taking into account the effect of coating and plasma on antenna properties is topical for developers of onboard electronic devices. Due to the complexity of the object, modeling becomes important. A spherical in-phase slot antenna covered with a dielectric and a plasma layer is considered as a model. The presence of a dielectric layer changes the direction of radiation and the gain. The change in the layer thickness can shift the peak of the main lobe of the radiation pattern and the gain. It is known that with increasing frequency, the attenuation loss increases, but the reflection loss decreases, and there is an optimal operating frequency. The aim of this work is to study the directional properties of an antenna system consisting of a spherical in-phase slot antenna with a dielectric coating under the plasma layer, depending on the operating frequency and thickness of the dielectric coating. Methodology. The study is based on the method of integro-functional equations, which greatly facilitates the construction of an analytical model with further use of the MATHCAD application. Findings. Analytical representations were obtained for the field in the dielectric and behind the plasma layer in the external space in the form of spherical harmonics, as well as the reflection coefficients in the dielectric layer, which allowed to estimate the degree of matching of the antenna with the generator, and the transmission coefficients to calculate the radiation pattern and estimate the signal losses in the dielectric and plasma. The dependence of the radiation pattern on the frequency and the effect of the thickness of the dielectric coating on the radiation characteristics at the operating frequencies from 1 to 10 GHz, with a sphere radius of 1 m, a dielectric layer thickness of 5 cm, and a plasma layer thickness of 5 cm, were studied. For frequencies ranging from 1 to 10 GHz, the radiation pattern exhibited a stable behavior, which allows to use it as a wide-range antenna. In addition to this, it was found that the radiation level rises when the radius of the spherical slot antenna is multiples of half the wavelength. In particular, at a frequency where the antenna has a radius of three wavelengths, the radiation level is greater compared to the other frequencies. It was shown that, the influence of the dielectric layer is manifested in the fact that the radiation pattern changes from one lobe to two lobe with an increase in the layer thickness. In this case, there is observed a modest non monotonic change in the radiation level. We assume that this is associated with the ratio between the wavelength corresponding to the operating frequency and the thickness of the dielectric layer. Conclusion. The findings of the research allowed to choose the parameters of the antenna system taking into account the electro physical properties of the dielectric layer and plasma. In particular, it is reasonable to choose the layer thickness depending on the wavelength, because the typically used dielectric material has a fixed dielectric constant. Using coatings with a different dielectric constant, one may expect a significant fluctuation in the antenna gain.