Determining the Minimum Scan Step of an Electronically Scanned Antenna

Introduction. Electronically scanned antennas (ESA) appeared about a century ago. Although the methods of their design and production have been sufficiently studied, some individual parameters are yet to be revealed. One of such parameters is the minimum step of movement, along with a related parameter – the accuracy of beam alignment in a given direction. From the electrodynamic problem of radiation, it is obvious that the step is associated with the number of radiators and the accuracy of phase adjustment in analogue phase shifters, or with the quantization step in the case of using phase shifters with a discrete step.Aim. To discover a connection between the design parameters of ESA and the step of beam steering; to investigate the dependence between the step and the parameters of the phase shifter and types of beam forming phased array circuits; to create a mathematical apparatus for calculating the minimum step of beam movement for the sum and difference radiation patterns.Materials and methods. Analytical relations were determined for calculating the step depending on the geometric dimensions and location of the radiators. A software application was developed for calculating radiation patterns. A software and hardware complex was designed for beam control of an experimental C-band ESA.Results. A method was developed for calculating the minimum step of ESA scanning. Mathematical relations for calculating the minimum step and accuracy of the ESA beam setting were obtained. A comparison of the experimental and theoretical data on the minimum step of movement of the sum and difference beams of a C-band ESA with the ratio D/λ=10 in the X coordinate and D/λ=5 in the Y coordinate showed good agreement.Conclusion. The created mathematical apparatus makes it possible to calculate the minimum step of electron beam scanning with sufficient accuracy. The experimentally measured steps of the beam movement for an array of 144 elements confirmed the obtained analytical relationships. In an ESA with a small number of elements (N < 10), the minimum step of movement can be variable. The theoretically achievable minimum step of beam movement is determined by the phase shift of the least significant bit of the phase shifter and the electrical length of the antenna aperture.

Solving problems of radiation and diffraction electromagnetic waves based on integral representations electromagnetic field

Annotation Various forms of integral representations of the electromagnetic field are considered. It is shown that the use of analytically developed integral representations of the electromagnetic field instead of the vector potential method makes it possible to significantly simplify the formulation of the internal and external electrodynamic problem for specific structures. The numerical results of solving problems of radiation and diffraction of electromagnetic waves are presented. It is shown that taking into account the peculiarities of the geometry and using projection functions close to the eigenfunctions of the integral operator of the internal electrodynamic problem for basic elements make it possible to construct effective algorithms for the electrodynamic analysis of metastructures. A mathematical model of a multistage chiral frame is proposed. By the example of a tubular vibrator, the possibility of approximating the solution of an internal electrodynamic problem using eigenfunctions is demonstrated. The prospects for further development of the integral representations of the electromagnetic field method are considered.

Thin-wire radiating structures with double symmetry

The problems of electrodynamic analysis of thin-wire radiating structures with double symmetry are considered. New generalized integral representations of the electromagnetic field are obtained for the case of structures with single and double symmetries. Based on the obtained expressions, mathematical models of two - and four-way elliptical spiral antennas are constructed. It is shown that taking into account double symmetry in solving the internal electrodynamic problem leads to a set of independent Fredholm integral equations of the first kind written with respect to the distributions of normal current waves, which significantly simplifies the solution of the internal electrodynamic problem. Comparisons of current distributions along conductors, their input resistance dependences on the radius of the structure, and normalized radiation patterns for two- and four-way spiral emitters are presented.

Experimental Research of Induction Heating in Inner Hollow of Cylindrical Solenoid

Purpose. Experimental determination of the dependence of the magnetic field strength distributions and the density of induced currents in the metal of the tubular blank from its position in the cylindrical inductor internal hallow. Methodology. The electrodynamic problem solution using mathematical apparatus for analytical calculations. To describe the processes that arise in the material under processing, expressions for fields and currents flowing in non-magnetic metals under the action of a multi-turn cylindrical solenoid that derived from the system of Maxwell's equations. Accepted mathematical assumptions and simplifications do not affect the correctness of the results. Carrying out an experiment to determine the intensity of the magnetic field in the solenoid inner hollow and the induced currents density on the surface of the nonmagnetic blank. Results. The obtained experimental distributions of the magnetic field strength and induced currents with the full blank placement in the cylindrical inductor hollow correspond to the analytical relations derived earlier and coincide with the fundamental physical concepts of the processes taking place in the system. When the billet is partially placed in the inner hollow of the inductor, there is a sudden increase in the tangential magnetic field strength component. In this case, an extremum is observed in the end zone of the billet. This is explained by the concentration of induced currents in this region, as well as on the cylindrical surface of the billet. Originality. The average induction heating speeds correspond to the calculated values for the materials of the processed samples used in the experiment, which indicates the effectiveness of using this processing technology in equal measure, both non-magnetic metals and magnetic. The practical value of the results consists in the possibility of estimating the qualitative indices of the concentration of induced currents and heat release in the end part of nonmagnetic cylindrical preforms with their partial overlapping by an inductor to perform heating operations.

Comparison of subsurface object recognition by artificial neural networks and correlation method

Background: The problem of searching for subsurface objects has a particular interest for construction, archeology and humanitarian demining. Detection of underground mines with the help of remote sensing devices replaces the traditional procedure of finding explosive objects, as it excludes the presence of a human in the area of possible damage during a charge explosion. Objectives: The aim of the work is to improve the recognition of three-dimensional objects and demonstrate the benefits of using a more informative data set obtained by a special antenna system with four receiving antennas. In addition, it is necessary to compare the effectiveness of artificial intelligence and the method of cross-correlation for recognition by subsurface radar, taking into account the additive noise of different levels present in practice. Materials and methods: The electrodynamic problem was solved by the finite difference time domain (FDTD) method. An artificial neural network (ANN) is trained on ideal signals to detect the features of the field that will be found in noisy data to determine to the position of the object. Cross-correlation also involves the use of an array of ideal signals, which will be correlated with noisy real signals. Results: The optimal and effective ANN structure for work with the received signals is created. It was tested for noise immunity. The recognition problem was also solved by the classical method of cross-correlation, and the influence of noise of different levels on its responses was studied. In addition, a comparison of the efficiency of their recognition using 1 and 4 sensors was made. Conclusions: For subsurface survey problems, a deep neural networks with at least three hidden layers of neurons should be used. This is due to the complexity and multidimensionality of the processes taking place in the surveyed space. It has been shown that artificial intelligence and cross-correlation techniques perform the object recognition well, and it is difficult to identify the best among them. Both approaches showed good noise immunity. The use of a larger data set of four receivers has a positive effect on the recognition results.

Решение электродинамической задачи для микрополосковой излучающей структуры с киральной подложкой

We present a solution of the electrodynamic problem for a microstrip radiating structure with a substrate of a chiral metamaterial using the singular integral representation of the field, which in turn is reduced to a singular integral equation with the Cauchy-type singularity relative to the longitudinal component of the surface current density. Graphs of the current distribution for different types of substrates and the chirality parameters of a substrate are given.

Analysis of Electrodynamics Properties of Materials with High Dispersity Metal Powder in Axial Moving Systems

This paper describes the reception, researching and electrodynamics investigations of recently obtained materials. These materials demonstrated the losses dielectric behavior and represent a wide interest as radio markers with controlled distortion. The investigated samples can be used as a coating for rotating machine elements for radio diagnostics. The considered materials performed by epoxy warp with high dispersity metal powder content established the required properties for iron 60 % and nickel 60 %. Primary materials parameters are taken in the natural experiment and electrodynamics properties are studied based on a mathematical model. The presented results can be extended to seminatural experiment setup in future. This paper does not contain the formulation of electrodynamic problem.