Vol 28, No 1 (2025)
Articles
Method of estimation of frequency parameters of ultra-wideband signals with an unknown spectrum shape in the presence of interference
Abstract
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.
7-13
Methodology for determining and controlling the load capacity of integrated circuits
Abstract
Background. The relevance of the topic of this work is due to the need to increase the reliability of the quality of determination and control of the load capacity of microcircuits. Aim. Improving the accuracy and expanding the control functions in determining the load capacity of the microcircuits. Methods. The article considers a variant of the diagnostic non-destructive testing of microcircuits. It includes a model, a control device and an algorithm for its functioning. A well-known model was used, which was adapted to specific development and research tasks. The proposed technique makes it possible to find the largest number of inputs of logic elements that can be connected to the output of the tested microcircuits without deterioration of its functional parameters. The device included in the methodology can be used both independently and in the system of the measuring complex in conjunction with other equipment. Operation in three main modes is provided by programming the microcontroller. The program was written in C++. The proposed algorithm ensures the operation of the control device in dichotony modes, sequential and manual. Performs the functions of selecting the initial and maximum values of load elements, the signal level by which the load capacity is determined. Results. The values of the load capacity for three types of chips are obtained. The indicators of control accuracy and reliability have been determined. Using the element base of Microchip and MAXIM companies allowed for a 30% increase in measurement accuracy. Based on the conducted research tests and mock-up of the device, the capabilities of the device in various operating modes are evaluated. Conclusion. Testing of the technique on a number of samples showed its high efficiency. After finalizing the design of the device, instructions for its operation were prepared.
14-19
Plenary reports of the XXI International scientific and technical conference «Physics and technical applications of wave processes»
Calculation of optimal values of weight coefficients for compensation of the mutual coupling of antenna array elements
Abstract
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.
20-32
Solution of electromagnetic inverse problem of inhomogeneity reconstruction in dielectric body by near-field measurements using two-step method
Abstract
Background. The inverse electromagnetic problems of restoring inhomogeneity in a dielectric body from near-field measurements arise, for example, in the early diagnosis of breast cancer by microwave tomography. The solution of such inverse problems is the basis for the development of technology for detecting inhomogeneities using microwave devices. The effectiveness of the corresponding technology depends on the accuracy of solving the inverse problem. Therefore, the development of new, more accurate methods for solving the inverse problem of microwave tomography is very relevant. Aim. The work is devoted to the development of a method for solving the electromagnetic inverse problem of microwave tomography using near-field measurements, that is, restoring the structure of an inhomogeneous dielectric body based on the values of the electromagnetic field outside this body using a measuring installation. Methods. The method of solving the inverse problem is a two-step one for determining the inhomogeneity of a body, which consists in first finding the current function inside the body, and then calculating the permittivity function. The method is not iterative and does not require knowledge of a «good» initial approximation. Results. A two-step method has been applied for the inverse problem of microwave tomography. Numerical results are presented. Inhomogeneous bodies in the shape of a hemisphere are considered. Experimental results are presented. Conclusion. The effectiveness of the proposed technology for detecting inhomogeneities in a dielectric body by microwave tomography is shown. The results of calculations and experimental data are presented.
33-38
Methods of designing bandpass filters on coupled coaxial resonators
Abstract
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.
39-55
Antenna-feeder systems for EHF-radiointerferometers
Abstract
Background. The development of a microwave method for researching shock-wave and detonation processes using radio interferometers requires the development of antenna-feeder systems taking into account the specifics of gas-dynamic experiments. Aim. Design of antenna-feeder systems for radio interferometers in the millimeter and submillimeter wavelength ranges, development of options for constructing feeder lines and probing devices. Methods. Theresultsof numericalmodeling in CST MWS, theoretical calculations and experimental studies of interferometer antenna-feeder systems are presented, confirming the proposed technical solutions effectiveness. Results. The requirements for antenna-feeder systems as an integral part of the radiointerferometer are given. Dielectric emitters advantages are justified and planar dielectric emitters are proposed. Small-sized antenna-feeder systems with dielectric inserts are proposed, which have found their application in diagnostic tasks in closed volumes. In order to reduce losses in the feed line and build lines up to several meters, antenna-feeder systems on rectangular supersized metal waveguides have been studied, including the proposed pyramidal horn transitions from standart waveguide section to a supersized section, and a combined feeder line using a flexible dielectric waveguide to connect metal waveguides. A quasi-optical two-mirror antenna with high spatial resolution and minimal losses is considered. Conclusion. The article shows the microwave diagnostic method advantages, various methods and schemes for feeder lines constructing proposed and justifies probing devices (emitters) types usage depending on the solved problem and the operating frequency range.
56-75
Computationally efficient solution for finding the current density on the illuminated and shadow sides of an infinitely thin circular disk
Abstract
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.
76-87
Reflection and transmission of circularly polarized light for a layered periodic system with distributed defects
Abstract
Background. Periodic layered systems form one-dimensional photonic crystals that have many properties of conventional crystals. Of particular interest are the optical properties of such structures, which attract the attention of researchers and engineers due to the prospects for practical applications. Aim. The paper presents the results of calculating the frequency and angular spectra of reflection and transmission of light for a periodic structure with complex embedded defects. Methods. Using the characteristic matrix method, the energy reflection and transmission coefficients are calculated for such a structure using circularly polarized light. The ellipsometric parameters of the reflected and transmitted radiation are analyzed. Results. The paper shows that oblique incidence of light on the studied periodic structure with a defect leads to a wide variety of angular and frequency reflection and transmission spectra, which allows using this structure for selective reflection, as well as for devices that change the nature of the polarization of incident radiation. Conclusion. The use of circularly polarized radiation during its reflection and transmission for periodic media with complex distributed defects allows obtaining new controlled optical devices.
88-94
Linear and flat antenna arrays focused on a broadband signals in radio communications, microwave technologies and non-destructive testing
Abstract
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.
95-110