Vol 25, No 3 (2022)

In this paper, we propose a method for reducing the energy loss of photosensitive structures based on nanocrystalline silicon using passivating coatings of dysprosium fluoride. Since this material has good optical and photoelectric properties, when preparing Si/DyF₃ structures, the dielectric film makes it possible to reduce the number of recombination centers and increase light absorption. Methods for creating and studying photosensitive structures with coatings are shown. A technique for determining the thickness of a dysprosium fluoride coating due to light interference is described. The results of studying the photosensitivity spectra and the reflectance of the obtained photosensitive structures are presented. The positive effect of silicon nanostructures, as well as dysprosium fluoride films on the photosensitivity spectra of the structures, is shown. With the help of the data obtained, it is planned to improve the existing technology for creating photosensitive structures based on porous silicon in order to increase their output characteristics.

The paper considers the possibilities of 3D printing technology for the manufacture of X-band waveguide photonic crystals. The photonic crystals for an EIA WR-90 standard rectangular waveguide with a cross section of 22,86 × 10,16 mm² in the X-band were designed and manufactured. Numerical modeling of the reflection characteristics of photonic crystals of several designs in the OpenEMS software package was carried out. Based on the simulation results, the best types of the structures were selected, which were manufactured using the physical modeling technique by the fusion method of PETG plastic. Experimental study of the manufactured layouts and comparison of the experimental data with the numerical simulation data were performed. The best types of manufactured models of waveguide photonic crystals showed transmittance and reflection drop in the corresponding frequency bands of the order of 15–20 dB, which is acceptable for technical applications. The numerical modeling results are in good agreement with experiments, thus indicating the high efficiency and good control of the topology and dimensions of the manufactured photonic crystals’ structural elements in the used type of 3D printing technology.

Based on the measured impedance of the dielectrics an equivalent high frequency (0 Hz - 500 MHz) circuit model was built. The equivalent circuit model was built taking into account the physical processes occurring in the dielectric. The attempt explaining why the frequency characteristics (modulus and phase) of the dielectric complex impedance have such a character in a wide frequency band (up to 500 MHz) was made. It was shown that for constructing an equivalent circuit model (structure and parameters), measuring only the dielectric's resistance modulus is not enough. It is also necessary to measure the phase of the dielectric complex resistance, which is ignored in many works on the synthesis of an e dielectric equivalent circuit.

The structure of the antenna array control system with a combination of strengh and flexible scanning programs is proposed, characterized by the introduction of additional modules of statistics and expert assessments in the feedback circuit between the secondary processing module and hardware and software complexes for the formation of transmitting and receiving antenna array radiation patterns. The implementation of this structure allows for the formation of an additional transmitting and several receiving beams to confirm marks that do not meet the specified detection criterion. An algorithm for controlling an active phased array antenna has been developed, characterized by a procedure for additional confirmation of marks with a low signal-to-noise ratio due to the formation of additional transmitting and receiving beams. The estimates of the gain from the implementation of the proposed structural scheme of the antenna array control system and the algorithm of its functioning are obtained.

Currently, neural network methods of fire detection have been used to monitor fires in forests. To date, such systems have been developed as the Prometheus project, the Fire Video Detector, and the Artificial Intelligence University method. These methods make it possible to determine a fire with an accuracy of more than 90 %, for which a combination of recurrent and light-line neural networks is used. The article proposes a method for improving the efficiency of neural network methods for determining fires in forests based on computer colorimetry. The use of this method makes it possible to increase the efficiency of neural network methods for detecting fire when using multiple cameras of a video surveillance system. Thus, the article presents a comparison of the performance of a convolutional neural network with and without the use of a colorimetric module. According to the results, the efficiency of work has increased by more than 20 %.