Radioelectronics and Communications Systems

Features of calibration of satellite SARs with multibeam reflector antenna

Dmytro Vasylenko — 2024-07-25

The paper deals with the methodology of internal calibration of the satellite radar with synthesized aperture (SAR) of the EOSSAR project, built based on a hybrid multibeam offset mirror antenna with a low-element horn irradiation array. The purpose of the internal calibration procedure of the X-band multichannel satellite radar of the EOSSAR project is to achieve the required instrumental accuracy of radar images, which requires obtaining a highly accurate copy of the probing pulse on board and completing the identification of characteristics of the radar’s transmit and receive paths during the shooting. The paper theoretically substantiates and analyzes the complex routes of signals in the receiving and transmitting paths during the internal calibration procedure of radar equipment, in particular, to obtain a copy of the probing pulse and improve the correlation function during the digital processing of shooting data of a satellite SAR based on multibeam mirror antennas.

Distortion of compact antenna test range characteristics caused by realistic design of blended rolled edge reflectors

Rostyslav Dubrovka — 2024-07-25

The results of investigations of quiet zone distortion caused by realistic design artefacts of blended rolled edge reflectors (BRE) used in compact antenna test ranges (CATR) are presented. Despite thorough investigations of this type of reflector in recent years, little attention has been paid to accurate scenarios, i.e., characteristics of CATRs are observed for physically fabricated reflectors. Typically, reflectors have a fixed thickness and finite-size edges. As a result, quiet-zone (QZ) performance predicted by physical optics and physical theory of diffraction (PO/PTD) will omit certain phenomena that could potentially impact the performance of the CATR. It is usually caused by in-house or commercial PO/PTD software limitations, which consider only non-shadowed surfaces and generally omit reradiation. Parameters affected by the realized mechanical implementation are side and rear illumination of anechoic chambers, amplitude and phase ripples in the quiet zone as functions of real thickness and trimmed edges of BRE reflector, which are in the deep shadow region. Therefore, this paper concentrates on carefully examining these artefacts where a proprietary, full-wave, three-dimensional, computational electromagnetic (CEM) solver was utilized using a method of moments-based finite element solver.

Properties of 2- and 4-cell metamaterial modules based on double Moebius strips

Vadym Slyusar — 2024-07-25

The article continues the study of a new type of metamaterial cells based on double Moebius strips, which are mathematical constructs with unique properties such as non-orientability and one-sidedness. The authors explored various design options that utilize the variation of the metamaterial cell’s design and parameters. Due to the complexity of describing the interaction between the non-Euclidean geometry of the metamaterial cells and radio waves, numerical modeling methods were employed to analyze the proposed designs. The study evaluated and compared the proposed metamaterial cells based on two characteristics: the electric permittivity and magnetic permeability as a function of frequency. These parameters are essential in determining the cells’ performance and potential applications.

The authors found that combining multiple cells with rings based on double Moebius strips within a single block provides greater degrees of freedom for optimizing such designs’ properties than using individual metacells. Previous research has also demonstrated the benefits of using multiple cells, particularly when they are arranged in a specific pattern to achieve desirable properties. In addition, the authors discovered that the best properties are not necessarily associated with monolithic blocks with the same type of cell. Instead, combining rings with different rotation directions and cutout orientations resulted in the best performance. These findings suggest great potential for using such blocks to create one-layer or multi-layer metacoatings that cover surfaces of any configuration and size. Overall, this study provides valuable insights into the design and optimization of metamaterial cells based on double Moebius strips, which could have many applications in telecommunications, energy harvesting, and sensing.

Controlled patch antenna of axial topology with quasi-fractal substructure

Sergey A. Pogarsky — 2024-07-25

The paper presents the results of numerical simulation of the main electrodynamic characteristics of a controlled planar antenna with a hybrid topology containing an unclosed ring microstrip resonator, a disk microstrip resonator with quasi-fractal internal structure, and a controlled semiconductor element. For numerical simulation an integrated approach was used, including the semi-open resonator method and the finite element method (FEM). The FEM was implemented using the commercial package ANSYS HFSS. A quasi-fractal substructure made it possible to implement an additional frequency selection.

Wideband Ku-band antenna array with circular polarization

Oleksandr Sushko — 2024-07-25

The 4-element antenna array with circular Ku-band polarization for satellite communications is proposed in this paper. The feeding scheme for single elements to expand the antenna array’s operating frequency band is demonstrated. Laboratory measurements of the radiation characteristics and the alignment of the antenna array experimental sample are carried out. The operating frequency range is 10.7–12.75 GHz with a reflection coefficient of no more than –15 dB, and 14–14.5 GHz with a reflection coefficient of no more than –20 dB. The axial ratio does not exceed 6 dB.