Nikola Basta

Beam Synthesis Based on Inverse Discrete Radon Transform for Linear Pulsed Arrays

A method for direct beam synthesis in linear pulsed arrays of isotropic transmitters has been presented. By using the discrete Radon transform (DRT) and its inverse (IDRT), a known Radon transform framework has been adapted for gaining insight into a noniterative beamforming method. Theoretical analysis and numerical modeling, which validate this method, were conducted.

Compact GNSS antenna with circular polarization and low axial ratio

The investigation and development of a compact antenna for GNSS high-performance applications over a high-DK substrate are presented. In order to reduce multipath and achieve best performances, a very good polarization purity over a possibly wide bandwidth is needed. Therefore, a substrate which has both high DK and high thickness is used. However, because of the use of such substrate, the performance of the antenna may severely degrade when the total footprint (i.e. substrate and ground plane dimensions) change or when the antenna is used in array configurations. The reason for that are mainly waves excited into the substrate itself, producing spurious radiation and a high coupling between adjacent antennas. To overcome this drawback, a soft/hard surface (SHS) is employed, resulting in an antenna which has lower coupling with adjacent elements, as well as a relatively broad axial-ratio bandwidth.

ADIBEAM: Design and experimental validation of a robust beamforming platform for Galileo reference ground stations

The increase in navigation accuracy demanded by EGNOS and Galileo and their future evolution encourages the study and design of advance receiver architectures. In that direction, the ADIBEAM project focuses on the design of high accuracy ground stations, specifically GNSS Reference Stations, in order to improve its robustness in front of multipath and interference errors with the goal of achieving centimeter level tracking accuracy. The adoption of antenna arrays and digital beamforming at the ground reference station receivers is one of the most promising approaches to cope with errors induced by multipath and interference. This paper proposes an innovative design of a ground based tracking station. In particular, the architecture proposed is based on the use of an antenna array and digital beamforming techniques, considering both adaptive and deterministic methods. The work carried out here considers the ground based tracking system, including the characterization of the system components (antennas, RF chains, calibration techniques, GNSS software receiver and digital beamforming), and the development of a software based experimentation platform representative of the proposed design for a hardware prototype. The sensitivity to perturbations and the extreme difficulty to perfectly control and calibrate all the components of the system, especially regarding the antenna array implementation, requires that the proposed design take into consideration not only the benefits of the possible solutions but also their feasibility for a real implementation. In summary, this paper will present the design proposed and the Experimentation Platform used for its validation.

SEQAR: An Efficient MATLAB Tool for Design and Analysis of Conformal Antenna Arrays [EM Programmer's Notebook]

SEQAR is a MATLAB-based software tool for the design and analysis of conformal antenna arrays of any type. It uses complex single-element radiation patterns, simulated in commercial electronic design automation (EDA) programs or taken from measurements, to construct arbitrary antenna arrays. Beamforming capabilities, as well as the influences of tolerances and element failures for these arrays, can be investigated. As an example, the pattern synthesis of a conformal antenna array employed in a receiver for precise safety-of-life satellite navigation is presented.

Synthesis of Pulsed Radiation With a Linear Array of Nonisotropic Antennas

This paper deals with the performance assessment of a numerical tool for designing the response of a pulsed antenna array when properties of the embedded array elements and desired space-time radiation pattern are given. The synthesis of a pulsed beam is performed in the framework of the discrete Radon and Fourier transforms with realistic antenna arrays, the properties of which were simulated in a 3-D electromagnetic solver.

Circularly polarized antenna array of digitally controlled linearly polarized elements

This investigation has the purpose of revising the problem of the pattern synthesis based on non-equal antenna array elements. In the context of adaptive reception of the signals for global navigation satellite systems (GNSS) we study the possibilities of digital beamforming (DBF) for an array of linearly polarized elements under the constraints of right hand circular polarization of the desired signal and a presence of linearly polarized interfering signals.

Miniaturized CP patch antenna with low spurious radiation for GNSS applications

This contribution presents investigation and development of a miniaturized antenna on a PTFE/ceramic substrate for GNSS high-performance applications. Due to the use of such a high-DK substrate, the performance of the antenna is very sensitive to variations in substrate and ground-plane dimensions. It may also severely degrade when the antenna is used in array configurations, due to the excitation of surface waves, producing spurious radiation and a high coupling between adjacent elements. A soft surface is employed to deal with this limitation, resulting in an antenna that exhibits lower coupling with adjacent elements and low sensitivity to changes of the substrate outer dimensions.

Study on a stacked patch antenna element for dual-band GNSS arrays

The ever increasing signal processing power of the todays receivers introduced the era of multi-sensor, multi-band and intersystem GNSS operation. This yields numerous advanced techniques, like antenna adaptiveness and digital beamforming (DBF), through which one can efficiently mitigate unwanted multi-path signals and interferers. The presented work shows results of investigations on a candidate antenna element suitable for integration in a DBF-capable GNSS array.