Scherbina O. Methodology of constructing antenna systems for radiomonitoring with filtering and interference suppression

The thesis is dedicated to solve scientific-engineering problem of increasing the efficiency of the radio monitoring antenna systems. A methodology for constructing low-element antenna systems for radio monitoring with advanced functionality has been developed in this work. The methodology covers compensation and adaptation methods for suppressing and filtering interference emissions. The components of the methodology provide an opportunity to increase the efficiency of antenna radiomonitoring systems in the process of measuring the main characteristics of the investigated electromagnetic wave when the system is exposed to interference radiation at a frequency close to the frequency of the useful signal. The methods of constructing structural diagrams have been improved and the parameters of low-element antenna systems have been estimated with the suppression of the influence of interference when using the principles of amplitude and phase compensation, as well as the principles of adaptation. Adaptive antenna arrays separate the useful signal by electrical beamforming with minima in the directions of incidence of electromagnetic interference waves. In the case of antenna systems with filtering and interference cancellation, both electrical and mechanical beamforming can be used. For antenna systems of radio monitoring stations, mechanical beamforming is the most rational, since it allows to reduce errors in determining the angular position of both the useful signal and the interference signal. With the help of the developed methodology for constructing antenna arrays with a primary signal processing device, it becomes possible to simultaneously perform a number of important functions for radio monitoring systems: automated space survey and identification of the radiation source, automatic determination of the angular coordinates of radiation sources, interference suppression at frequencies close to the frequency of controlled radio emission, measurement of electric field intensity, measurement of the polarization parameters of the radiation field. For the developed scheme of the antenna system, the advantage of using mechanical scanning of space has been substantiated. During electrical scanning, a deformation of the radiation pattern occurs, which can lead to significant complications in determining the useful signal in the presence of interference at frequencies close to the frequency of the useful signal. When using mechanical scanning, the shape of the radiation pattern remains unchanged. This provides better accuracy of aiming at the radiation source than with electrical scanning. At the same time, the phase shift in electrical scanning depends on the meridional angle. This makes it difficult to determine the azimuth bearing of the radiation source. Considering these disadvantages, it is advisable to use mechanical control of the antenna position in space, in which the radiation pattern remains unchanged when viewing space in the range from 0o to 360o . In the thesis, a new method for calculating the accuracy characteristics of measuring the parameters of the electromagnetic field by a radio-monitoring antenna system has been developed. The method is based on the representation of the structural diagram of the antenna system in the form of a mathematical model, in which the number of variable informative voltages is limited to ensure transparent functional connections. From the analysis of the accuracy characteristics of the fourelement antenna system, it follows that the angular resolution depends both on the radiation pattern of the antenna array and on the accuracy of establishing the distances between the phase centers of real and virtual dipoles. The operating frequency range of the antenna array is limited not only by the deformation of the radiation pattern, but also by errors in the design of the antenna structural elements. The obtained scientific results of the thesis can be used in research organizations and operational divisions of radio monitoring and control over the use of the radiofrequency resource.