Volume 28, Nº 1 (2025)

Background. One of the urgent tasks of processing ultra-wideband signals is the assessment of their frequency parameters in complex signal-noise conditions. Aim. The paper presents the synthesis and analysis of an algorithm for jointly estimating the central frequency and bandwidth of ultra-wideband signals received against the background of Gaussian narrowband interference and Gaussian white noise. Methods. The study uses the computational method of statistical radiophysics and the method of mathematical statistics. Results. The characteristic of the joint estimation of the central frequency and frequency band of ultra-wideband signals, including the values of the offsets and scattering of the estimation, is found. It is established that with an increase in the intensity of interference, the accuracy of the joint estimation decreases. Conclusion. The obtained results allow us to make a reasonable choice of the necessary algorithm for estimating the frequency parameters of ultra-wideband signals depending on the requirements for the accuracy of estimates in a complex signal-noise environment.

Background. Antenna arrays are widely used in a variety of modern radio engineering systems for wireless communication and radar. The phenomenon of mutual coupling of antenna elements, which is manifested in practical implementation, may cause noticeable distortions of one of the most important characteristics of the antenna array – its radiation pattern, which must meet strict requirements in certain tasks. In view of this, the relevance of the question of methods for achieving the most accurate control of radiation patterns becomes clear. Aim. Investigation of the possibility of compensating the mutual coupling of antenna elements by adjusting the weight coefficients at the input of the antenna array, derivation of calculation relations for converting input signals, evaluation of performance measures for reducing distortion of directional characteristics provided by the application of the proposed approach. Methods. The main theoretical relations were derived using a mathematical apparatus that allows applying linear algebra methods to the description of the mutual coupling of antenna elements. The study of the antenna arrays based on half-wave dipoles and considered as an example was carried out using electrodynamic modeling. Quantitative estimates of the effects of mutual coupling and their compensation, as well as verification of the developed mathematical model, were carried out using numerical methods. Results. On the basis of the analysis of matrix equations describing the mutual coupling of antenna elements, the possibility of performing the input signals transformation, providing the restoration of the radiation patterns characteristics as a result of the radiated electromagnetic waves interference, has been established. The basic mathematical relations necessary for the implementation of this procedure are derived, specific examples are considered and numerical accuracy characteristics of the proposed approach are obtained. Conclusion. The developed technique makes it possible to find the explicit form of the correcting linear transformation of input signals for an arbitrary antenna array. At the same time, the use of the correction matrix calculated in this way makes it possible not only to significantly reduce the distortion of the radiation patterns themselves caused by the mutual coupling of the antenna elements, but also to compensate for undesirable changes in such characteristics as the direction of the main beam of the antenna array.

Background. Ultrahigh frequency bandpass filters are widely used in various radio engineering devices. A special place among microwave band-pass filters is occupied by filters that are part of multiplexers, in particular, diplexers used in cellular communication systems. Filter and diplexer designs based on coaxial resonators are widely used in mobile communication systems. Filters on coaxial resonators have a fairly well-developed design and can be used for broadband systems. Aim. Currently, the design of filters and diplexers on coaxial resonators continues to be improved in terms of improving manufacturing and assembly technology. Methods. The method of equivalent circuits, communication matrices. Results. The principles of constructing filters on coupled coaxial resonators are considered. The methods of obtaining a given shape of the amplitude-frequency response of the filter are analyzed. Conclusion. A method for designing transfer functions and synthesizing prototypes of filter circuits with Chebyshev characteristics is considered.

Background. The article is devoted to the development of a computationally efficient numerical solution to the diffraction problem on an infinitely thin ideally conducting circular disk. The main attention is paid to the problem of finding the distribution of the surface current density on each side of the disk separately, which has remained undiscovered in other well-known studies. The aim of this paper is to eliminate this disadvantage by forming a computationally efficient algorithmic solution based on the method of moments and allowing numerically to set a smooth approximation of the surface current density on the illuminated and shadow sides of an infinitely thin ideally conducting circular disk. Methods. The solution is formed by the Galerkin method when determining the desired approximation of the surface current density on the disk. The solution is based on the formation of a smooth vector function given by the sum of global curl-free and curl basis functions relative to the disk. The corresponding basis functions are formed from the modifications of Bessel functions of the first kind and Zernike polynomials proposed in the paper. Results. The operability of the proposed solution is verified on test examples for a disk at different diameter-to-wavelength ratios. The comparison was made with the solution of a similar problem in the Ansoft HFSS CAD system. Conclusion. The obtained results allow us to conclude that the proposed solution is preferable and are the basis for further generalization of the results to more complex geometric structures when using the conformal mapping method.

Background. The main properties and characteristics of focused antenna systems using narrowband signals are known and generally coincide with the properties of broadband discrete antennas with a symmetric spectrum. The use of broadband signals allows expanding the technical capabilities of devices using focused electromagnetic fields. This article is devoted to assessing the properties of broadband focused fields formed by signals with both continuous and discrete spectrums, and the possibility of creating special spatial distributions of focused fields is shown. An approach to the synthesis of broadband focused antenna arrays is proposed. A number of technical applications of antenna arrays focused in the near-field zone by a broadband signal have been developed. The aim of this article is to describe the main properties of focused broadband electromagnetic fields, to demonstrate the possibility of forming special focused spatial distributions and to develop practical application options based on them. Methods. Achieving the goal of the article is due to the use of well-known principles of electrodynamics and aperture theory of antennas. Results. The features of the formation of focused broadband electromagnetic fields are shown and their main properties are given. Options for the technical application of focused broadband antennas in radio communication and direction finding tasks are proposed. Conclusion. The results obtained confirm the importance of assessing the properties of broadband focused antennas and developing a number of technical proposals based on them.