Journal of Communications Technology and Electronics

The two-dimensional problem of scattering of a plane electromagnetic wave on a flat homogeneous magnetodielectric plate of finite dimensions is considered. The problem is solved by the method of integral equations for auxiliary surface currents. Algebraization of integral equations was carried out using the collocation method and overlapping three-step basis functions. The results characterizing the efficiency of the proposed algorithm are presented. The influence of the geometric and material parameters of the plate on its effective scattering surface (ESS) in the direction of wave incidence, which characterizes the effects of “invisibility” of the plate, is studied. It is shown that the minimum of the specified ESS is achieved at a plate thickness close to the thickness that ensures the in-phase geometry of the geometric-optical rays that have passed through the plate and the rays that have passed by the plate. The ESS of a plate made of a material with positive and negative refractive indices is compared.

The problem of constructing an empirical probability density distribution of the phases of a signal with phase shift keying modulation, as well as nonparametric estimation methods, is considered. The transition from the approximation method using basis functions to the method of windowed kernel functions based on harmonic functions is shown. The results of numerical experiments are presented.

Optical fiber (OF) with a relatively high level of the backward signal at a certain wavelength is developed and studied. An increase in the backward signal is reached due to the recording of multiple weak fiber Bragg gratings (FBGs) in the course of fiber pulling. A scheme that is simpler than the direct FBG recording through a phase mask is proposed and implemented. Fibers with FBG recorded with different ratios of the region with recorded gratings to the total length of OF are fabricated. An increase in the level of the backward signal relative to the level of the Rayleigh scattering by more than 30 dB is reached. Results of experimental study of the proposed OFs and examples of practical application are presented.

The problem of construction of ultra-wideband direct chaotic communication devices in the very high frequency and ultra high frequency ranges of radio waves is considered, the features of this range with respect to the propagation of electromagnetic radiation are discussed, and performance potential is evaluated. Experimental direct chaotic transceivers with a working band of 200–450 MHz, their structure, technical implementation, and characteristics are presented. The results of laboratory and field tests of prototypes are given to demonstrate transmission ranges of up to 1.5 km, which correspond to the calculated characteristics.

The generation and emission of high-power ultrabroadband electromagnetic pulses are studied. The possibility of high-voltage (about 100 kV) bipolar voltage pulses with a duration of about 200 ps is demonstrated. The electromagnetic pulses with a FWHM of less than 100 ps, an effective potential of up to 400 kV, and a repetition rate of 100 Hz are generated using the 16-element antenna array.

In this paper, performance comparison in terms of bit error rate (BER) of proposed WDM compatible optical CDMA system incorporating 3-D spectral-phase-time encoding/decoding to a 7 chip-super-structured fiber Bragg grating (SSFBG)-based optical code division multiple access (OCDMA) system is investigated. Coding and decoding using binary [0, π] phase chips is demonstrated for six users at 5 Gb/s, and a single coded signal is separated with acceptable bit-error rate ≤10−9. In our proposed optical CDMA system encoding and decoding is done by converting hadamard codes (used for conventional CDMA system) to phase codes. It is then compared with two optical pulse retiming and reshaping systems incorporating super structured fiber Bragg gratings (SSFBGs) as pulse shaping elements. Simulation results show that with all input bands having same sample rate, size data rates our proposed codes with even larger number of channels perform better in terms of eye opening & BER.

Abstract—Design and fabrication of photosensitive array elements in the 384 × 288 element format with a step of 25 μm with a long wavelength limit of sensitivity at 0.5 to approximately 9.5 μm were performed. The circuit and topology were developed, according to which matrix high-speed multiplexers are manufactured in the form of 384 × 288 elements with a step of 25 microns, which provide operating modes at a clock frequency of up to 20 MHz. The 384 × 288 element hybrid photodetector (PD) format in 25 μm increments has an average Noise Equivalent Temperature Difference (NETD) of less than 30 mK, while the number of working elements was more than 97%. Examples are given of using the microscanning system to reduce defective pixels in an image frame and/or increase the frame format to 768 × 576. It is shown that as a result of the use of microscans in a thermal imaging channel based on the developed PD during the transition to the 768 × 576 format, an improvement in spatial resolution of 1.4 times was obtained for the same minimum resolved temperature difference (MRTD), while the MRTD at a frequency of 0.44 mrad-1 decreased from 1.6 to 0.9 K compared to the original 384 × 288 format.

A mathematical model of the electromagnetic wave diffraction by specimens of anisotropic nanocomposite materials (3D lattices of oriented carbon nanotubes (CNTs) with magnetic nanoparticles and magnetic nanowires) in waveguides is developed. It is made with the help of a computational algorithm based on a multilevel recomposition and the method of autonomous blocks with the Floquet channels. The transmission coefficients of the H 10 wave with the frequency of 26 GHz that propagates through plates of magnetic nanocomposites in a waveguide are electrodynamically calculated as dependences of an external constant magnetic field (a magnetic bias field) and the number of magnetic nanoparticles filling the CNT.

An analytical solution to the synthesis problem for the generatrices of the mirrors of an axisymmetric two-mirror objective, which are synthesized for a specified mapping law of the incident and reflected wave fronts, is obtained in the geometrical-optics approximation. The solution, in which the generatrix is expressed in the form of a polynomial in even powers of angle, ensures exact focusing of radiation from one system focus to the other and a specified error of the realization of the mapping function via selection of the polynomial degree. Synthesis problems for an aplanatic objective and an objective with uniform amplitude distribution in the output front are considered. It is shown that, in the first case, a sixth-degree polynomial ensures realization of the Abbe sine condition with an error of 10−5 and, in the second case, it ensures a deviation from the specified amplitude of about 0.1 dB.