# Influence of Dielectric Plate Parameters on the Reflection Coefficient of a Planar Aperture Antenna
## 1 Introduction  
Antennas provided with radomes and their influence on the radiated electromagnetic field were investigated as early as the 1980s [1]. The antenna radome was originally intended as a form of physical protection of the antenna, connectors, cables, and all components of the antenna system against environmental influences. All these parts of such system can have a bad effect on the antenna reflection coefficients and, thus, affect the operation of the antenna at the desired wavelength. Several studies have been conducted that are focused on the antenna radome and its influence on the operation and parameters of antennas [2; 3; 4; 5; 6; 7]. The authors in [2] provide the design of a dielectric radome created to protect the antenna from environmental conditions via a series of conductors in the structure that enables a lower reflection coefficient of incident electromagnetic waves at the operating wavelength of the antenna. A modified Paris' model of a flat multi-layer radome structure (with anisotropic material) is presented in [3], and it is combined with a measuring method for accurate determination of the dielectric constant and dielectric loss. The study presented in [4] reviews the design of antenna radomes (electrically thin, half-wave, A-sandwich, C-sandwich) and their influence on antenna parameters (RF reflection and insertion loss), and the authors conclude that a proper selection of the radome and its characteristics can help to improve the performance of the entire antenna system. The quality and the impact of the dielectric-radome weather radar antenna are analyzed in [5] from the radiation pattern point of view to verify the antenna and radome specifications of the new Hohenpeissenberg radar. Measurements obtained from three different source locations in the far field of the antenna show that all major parameters of the antenna (i.e., 3-dB beamwidth, beam squint, and sidelobe levels) are satisfied with and without the radome. In article [6], the author highlights a very important role of radar in air and sea communications, remote data reading, weather forecasting, and defense. The radome placed on the antenna serves several purposes. It protects the antenna and its constituent parts from external disturbances (such as snow, rain, wind, etc. ), but research has shown that the exact choice of the material covering the antenna can significantly affect its properties and performance. The article explains the design and construction of the radome without compromising radar performance. Another study [7] also recommends radome types such as polycarbonate, Teflon, and polystyrene to maintain good antenna performance and a satisfactory reflection coefficient, i.e., materials with the lowest possible dielectric constant and tangent loss. This describes the medium through which electromagnetic waves propagate, their dielectric constants, their effects on impedance matching, the ideal distance of the radome from the antenna, and the results of the antenna radiation pattern when the antenna radome is properly selected. Article [8] deals with a similar topic in that the author describes in detail the properties and types of shield, the interaction with the antenna, the requirements for shielding, and the advantages of antenna shielding. As can be seen from the above literature overview, covering antennas with a specific dielectric plays a very important role in the physical protection of antennas and radars and can even be used to improve antenna characteristics in the context of impedance matching, i.e., reflection coefficients [9]. The authors in [10] analyze the input admittance of a circular aperture antenna fed by a waveguide of a circular cross-section mounted on a spherical grounded surface. The analytical approach is based on the moment method in the spectral domain in the Fortran programming language.