Vol 68, No 7 (2023)

New band-passing frequency-selective surfaces (FSSs) are proposed and investigated. Formulas for calculating the modulus and phase of the reflection coefficient of artificial magnetic conductors are obtained based on the proposed FSSs. The comparison of the results of electrodynamic modeling and calculation by formulas is carried out. The possibility of expanding the operating frequency band is shown.

The test methods designed for mathematical reconstruction of input signals of linear stationary information processing systems from distorted and noisy output signals are proposed and analyzed. It is shown that the use of test data allows one to carry out a non-blind reconstruction without determining the hardware functions of processing systems, which, in general, can belong to the class of generalized functions. The features of the use of the regularization technique in test methods are considered when solving ill-posed and ill-conditioned problems of reconstruction of real non-deterministic signals. The criteria for selecting test signals are analyzed. The results of numerical experiments on the restoration of one-dimensional signals and two-dimensional images at different noise levels are presented.

Starting from the definition of the main tone of the speaker’s speech as the minimum frequency of the linear power spectrum of the vocalized segments of the speech signal, an estimation of potentially achievable accuracy of its measurement under the action of background interference such as white Gaussian noise has been made. Based on this estimation, a suboptimal algorithm for measuring the pitch frequency using a short speech frame has been developed. The developed algorithm effectiveness is confirmed by the results of the experiment, during which the author’s software was used.

In this paper, we develop a method for the formation of non-binary Gordon–Mills–Welch sequences (GMWSs) with a period of N = p^(mn) – 1 that are formed over field GF(p) based on the generalization of the binary sequence formation method. An expression for calculating the vector of decimation indices А_m,n,r of the basic M-sequence (MS) for summable sequences in the synthesis of GMWS is obtained. A method for the formation of non-binary GMWSs for arbitrary MSs is presented. The values of the components of the C_m,n,r shift vector of a basic MS are shown to depend on the distribution of digits at the positions of the pth representation of the corresponding decimation indices.

Various solutions of the problem of approximation of high-order fractional transfer functions are considered and a technique for solving the stability problem for such functions is shown. The existing solutions of the problem of approximating function pα are compared with those proposed on the basis of the least mean square error criterion. As an example, the results of filter simulation using the proposed solution are presented.

In this paper, we consider the problem of generation of hypersonic oscillations in the circuit of a magnetostrictive converter covered by a positive feedback circuit. A “coupling parameter” that reflects the amplification of the signal in the feedback loop was introduced. The development of magnetic and elastic oscillations in time is considered. As the coupling parameter increases, three main oscillation modes are revealed: initial relaxation, stationary self-oscillations, and chaotic self-oscillations. The effect of the coupling parameter and the damping parameter of the magnetization on the time of development and the amplitude of oscillations was studied. The characteristic values of both parameters corresponding to transitions between modes are revealed. Practical recommendations for choosing system parameters for the most efficient excitation of hypersonic oscillations are given.

The results of unique experiments on synchronous recording of oscillations of earth’s surface with three laser interferometers–deformographs spaced at a distance of 6740 km, obtained during 2016–2020, are considered: two 100-m laser deformographs (Fryazino, Moscow oblast) and one 18-meter (Karymshina site, Kamchatka krai). It is shown that frequency-stabilized and thermocontrolled lasers, as well as systems for registering shifts of the compensation and modulation type interferogram provide an absolute instrumental resolution of 0.1–0.01 nm.