Том 64, № 6 (2019)

Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice (with additional capacitances installed between its elements to tune the AMC operating band) were derived. The results of numerical calculations validating the estimates using approximate formulas are presented. The engineering feasibility of a thin radio absorber with a tunable operating band based on this AMC and a resistive film was demonstrated theoretically and experimentally. The results of measurements performed in a waveguide with a cross section of 72 × 34 mm² revealed that the center frequency of the operating band of the radio absorber shifted from 4.9 to 2.7 GHz as additional capacitances varied from 0 to 1.27 cm.

An expression for soft decisions is obtained for incoherent demodulation of signals with m-digit frequency-shift keying in radio communication systems with character frequency hopping in the presence of additional noise with unknown intensity in the frequency channels of the system. Results of simulation are presented.

On the basis of the information theory of speech perception, a substantiation of the symmetric form of the Itakura–Saito divergence as the minimum decision-making statistics of the asymptotically optimal algorithm for recognition of speech signals at the basic, phonetic level of their processing is given. The conclusions of the theoretical study are confirmed by the results of an experiment. It is shown that the use of the synthesized algorithm can significantly improve the accuracy and reliability of the automatic recognition of the most problematic phonetic units.

Variants with generally spatial trajectories with one of the Cartesian coordinates that is cyclic for describing flows have been revealed among three-dimensional invariant solutions of the nonstationary nonrelativistic beam equations. The equations of plane solenoidal flows have been analyzed, whose solutions are not directly related to the group properties of the general beam equations.

Oscillations of magnetization and elastic displacement in a ferrite plate that is normally magnetized with respect to the plate plane are studied in the continuous excitation regime. Frequency multiplication determined by the ratio of the resonance frequencies of the magnetic and elastic subsystems is analyzed. Time and amplitude characteristics of the low- and high-level excitation regimes are studied under conditions for reorientation of magnetization. Recommendations for experiments are proposed.