Vol 62, No 2 (2017)

The possible character and peculiarities of dispersion distortions of a supershort radio pulse are considered on the basis of the analytical description obtained beforehand for the propagation of an electromagnetic pulse in a resonance absorbing medium. The pulse has a rectangular initial form and the carrying frequency coinciding with the resonance frequency of the strongest line characterizing the water vapor absorption in the millimeter wave range.

Propagation of a surface plasmon-polariton in a three-layer system consisting of the half-space filled with a metal, a layer of the gain medium of a finite thickness, and a half-space filled with vacuum is considered. The existence of the optimum thickness of the amplifying layer at which the plasmon is amplified several times stronger than in the case of infinite thickness is demonstrated. In particular, the plasmon loss can be compensated at a lower pumping intensity than in the case of infinite thickness of the gain layer.

Application of the method of the combined maximum principle to the synthesis of filters for tracking maneuvering aircrafts is demonstrated. The derived estimation equations are determined to within the synthesizing function. In constructing this function, the condition of stationarity of the Hamiltonian function on the switching hypersurface is used, which ensures adaptation to the observed motion. A tracking algorithm characterized by a lower, as compared to the Kalman filter, computational complexity and higher estimation accuracy during aircraft maneuvering has been synthesized.

For the complete composite binary offset carrier (CBOC) signals of new-generation global satellite radio-navigation satellite systems (SRNSs), analytical expressions for correlating functions (CFs) characterizing the single components of the modulating function are derived in terms of the inverse Fourier transform (IFT) of energy spectra at different fractional coefficients. The CF calculation technique is based on the energy spectra of complete CBOC signals represented as a partial sum of the series of cosines of the angles that are multiples of the angle γ_CBOC = ωτ_M2, where τ_M2 is the meander-pulse duration of the subcarrier oscillation of binary offset carrier (BOC) signals with BOC(6,1) modulation. In a number of cases, the IFT of energy spectra applied to calculating the CFs of complete CBOC signals is preferable (in particular, from the viewpoint of labor intensiveness) to the procedures by which CFs are obtained using the general definition. The CFs graphs constructed with the help of complete CBOC signals employed in the E1 band of the Galileo SRNS are presented.

Physical and mathematical reasons for the divergence of functional Volterra series in calculation of nonlinear electronic circuits described by algebraic differential equations are considered. It is shown that the main reason is the character of the feedbacks involving nonlinear elements and leading to a high level of repeated combinational interactions. On model examples, the disruption of the iterative process due to the loss of continuity and differentiability of nonlinear operators on the real axis or on the complex plane is demonstrated.

A problem of local subsurface probing of an orthotropic paramagnetic composite using a point source of stepwise external current that is parallel to a plane surface is formulated. Multidimensional Laplace–Carson transform is used to obtain transforms of the x (and y) Cartesian projection of the transmission and reflection characteristics. Analytical characteristics are determined at the origin. Expressions for the real and imaginary components of the x (and y) projections of characteristics are derived, the main properties are studied, and the computations are minimized at a predetermined accuracy using the Horner scheme. The relation of main stages and specific moments of the local development of transmission and reflection of elementary field of stepwise excitation is determined for orthotropic paramagnetic composite.

The luminescence, absorption and circular dichroism spectra of langasite family crystals La₃Ga₅-SiO₁₄ and Sr₃Ga₂Ge₄O₁₄ doped with chromium ions (0.1 at %) are studied in the region of 300–1200 nm. It is demonstrated that these spectra contain bands typical of both a Cr³⁺ ion in an octahedral environment (position 1a) and a Cr⁴⁺ ion in a tetrahedral site (position 2d). The intensities of these bands differ considerably.

Dynamic characteristics of compact vacuum gaps are studied. Experiments are performed in the microsecond range of current pulses with amplitudes ranging from 50 A to 5 kA and rates of rise ranging from 10⁹ to 10¹⁰ A/s at switching voltages ranging from 2 to 10 kV. The most stable operation of the gaps is reached when the cathode is triggered using positive pulses. The instability of the initial stage of burning of vacuum arc leads to an increase in the stabilization time of the main discharge. Electrical valve-like properties of compact gaps are manifested in the stable quenching of vacuum arc at a current attenuation rate of 0.5 kA/μs.

New designs of planar three-resonator bandpass filters with cross coupling having a large variety of frequency characteristics are considered. In addition to better one-sided selectivity, such filters implement symmetric amplitude–frequency characteristics with an attenuation pole at each side of the passband. These filters can also have constant delay time in the passband. Concatenation of the proposed three-resonator filters leads to multiresonator filters with high selectivity determined by two attenuation poles at each side of the passband. It is found that the type of connection of the middle resonator in the circuit of a three-resonator filter with cross coupling results in substantial differences in amplitude–frequency characteristics. The results of modeling of different frequency characteristics are presented. It is shown that filters have small dimensions, which are comparable to overall dimensions of microwave ceramic filters. For example, dimensions of a three-resonator stripline filter designed for a frequency of 1.9 GHz are 9.4 × 5 × 2 mm for the permittivity of the filter material ε_r = 92 and dimensions of a six-resonator filter are 10 × 9.4 × 2 mm.