Technology and design in electronic equipment

Single-channel doppler frequency detector of coherent synchronously fluctuating signal packets under gaussian noise

Igor Tsevukh — 2025-06-30

The need to further simplify the systems for detecting useful signals against a background of complex noises calls for the development of simple algorithms subject to certain restrictions on the detector structure and the type of input signal.
This article presents the developed optimal detection algorithm invariant to Doppler phase shifts of the signal for the class of single-channel Doppler frequency detectors of a Gaussian signal against the background of an additive mixture of uncorrelated and correlated Gaussian noises and under restrictions on synchronous fluctuations of pulses in a packet. The authors prove that the synthesized algorithm is optimal according to the criterion of the likelihood ratio averaged over the signal phase φс , as well as according to the criterion of the maximum of the “detection quality indicator” averaged over φс when solving the problem of detecting a Gaussian signal that fluctuates synchronously under Gaussian noise. The authors prove that the synthesised algorithm is optimal according to the criterion of the signal phase-averaged likelihood ratio,
A comparative analysis of the efficiency of the developed algorithm with the efficiency of the optimal multi-channel algorithm for a completely defined signal and with the potential efficiency of the algorithm forming the Hotelling statistics for various spectral-correlation parameters of the additive mixture of correlated and uncorrelated noise, both in terms of probabilistic characteristics — the probability of correct detection at a given probability of false alarm depending on the signal / uncorrelated noise ratio at the input of the system, and in terms of the "improvement index", which is the fraction of the signal/noise ratio at the output of the nonlinear system to the signal/noise ratio at its input, averaged over all possible radial velocities of the target. The research established the parameters of the signal and the additive mixture of uncorrelated and correlated noise for which the potential efficiency of the developed algorithm turns out to be higher than the efficiency of the algorithm implementing the known Hotelling statistics.
The obtained results allow us to determine the theoretical limit of improvement of real systems of this class and directions of search for new systems for practical application. In particular, they can be used to analyse the efficiency in designing coherent-pulse radar systems for detecting signals of moving targets against the background of an additive mixture of uncorrelated and correlated noises.

Quantum approach to direction of arrival estimation

Oleksandr Usatyi — 2025-06-30

The article analyses methods for determining the direction of arrival (DOA) of radio signals, particularly the MUSIC and ESPRIT algorithms. It is shown that the complexity of traditional approaches grows cubically with the number of antennas, which complicates their application in large-scale systems. The use of quantum algorithms for solving systems of linear equations and computing eigenvalues is proposed, allowing for a significant reduction in computational costs. The study examines the processing of complex matrices and presents a comparison table between classical and quantum versions of the algorithm in terms of computational complexity and structure.

Comparison of modulation methods for quasi-impedance source inverter in an autonomous power system with electrical energy storage

Dmytro Zakharchenko — 2025-06-30

This paper presents a comprehensive study of a modern autonomous power supply system with energy storage devices, focusing on all significant components within the system. Modern inverter control systems are described, highlighting the advantages and disadvantages of each method, the calculation approaches for key parameters, and the proposed implementation of control systems using MatLab/Simulink software. The modeling of control systems for a two-level quasi-impedance inverter within an autonomous power supply system with energy storage is conducted.
Based on the simulation results for powering a 2 kW AC load (220 V, 50 Hz) using lithium-ion energy storage and various control methods, a comparative table of the main performance indicators of modulation techniques is provided. Under the specified system requirements, the optimal control method is simple boost control (SBC), which offers the best efficiency among the considered techniques while maintaining low total harmonic distortion and a low implementation complexity.
It should be noted, however, that in real-world applications, the choice of modulation technique for a quasi-impedance inverter depends not only on conversion efficiency but also on practical constraints. For example, pulse-width modulation (PWM), the simplest to implement, lacks voltage-boosting capability due to the absence of shoot-through mode, reducing its effectiveness in low-input-voltage systems and potentially degrading output quality under high load. SBC, in turn, is limited by the absence of a zero switching state, increasing stress on passive inverter components. Additionally, the simultanІeous activation of all transistors during shoot-through mode leads to higher thermal losses and increased cooling requirements.
The practical application of constant boost control (CBC), which extends the voltage gain range by adding a third harmonic to the modulation signal, is hindered by higher harmonic distortion (up to 6.8%) and the need for additional filtering. Moreover, its implementation is more complex and demands precise parameter tuning for stable operation.
Other techniques, such as maximum boost control (MBC) and maximum constant boost control (MCBC), although capable of achieving the highest voltage gain, introduce significant low-frequency ripples, complicating passive component design, and cause considerable switching losses due to simultaneous key activation. These methods are more suitable for stationary systems with robust cooling and high-quality filtering.
The results of this study can support the justified selection of optimal modulation techniques for autonomous power systems with energy storage devices.

Application of solar tracking systems for enhancing the energy yield of photovoltaic modules: a review

Vitalii Fedenko — 2025-06-30

This paper presents a classification of solar trackers, their types, and the advantages and disadvantages of various algorithms for tracking the Sun’s daily movement. It is demonstrated that ensuring an optimal tilt angle of photovoltaic modules is one of the primary factors influencing the amount of electricity generated by solar power plants. Moreover, the economic benefits of their use are significant, as an increase in the generated electricity can enhance the profitability of investments in generation systems. The conducted studies indicate that efficiency improvements depend on the classification of the selected tracker based on its degrees of freedom, the tracking algorithm, and the installation site.

Wireless deformation monitoring system using strain sensor based on silicon whiskers

Anatoliy Druzhinin — 2025-06-30

Structural health monitoring of steel pipelines in industrial environments remains a critical challenge due to mechanical loads, pressure variations, temperature fluctuations, and external degradation. Traditional foil strain gauges, though widely used and inexpensive, suffer from thermal instability, limited operational life under cyclic loading, and the need for hermetic protection, restricting their application in infrastructure monitoring. Optical fiber sensors offer high precision, but are costly and difficult to integrate. This paper presents a wireless deformation monitoring system based on silicon whiskers used as strain-sensitive elements embedded into a Wheatstone bridge. One of the bridge’s four arms includes a silicon whisker sensor, while the others use 350 Ω precision tantalum resistors, ensuring thermal stability. The analogue output of the bridge is amplified and digitized by an HX711 ADC and processed by an Arduino-compatible microcontroller, which transmits the data via Wi-Fi. For thermal compensation, a “bridge within a bridge” configuration is used, allowing real-time correction of temperature-induced drift.
Experimental validation was carried out on a water pipeline segment under simulated pressures of up to 12 bar. The silicon whisker-based sensors demonstrated a stable gauge factor of ~120 ± 10% and a thermal resistance drift within +(0.1 ± 0.02)%/°C over the temperature range from −150 to +200 °C. The system reliably measured strain up to ±5ꞏ10⁻³ (0.5%), matching expected deformations in steel pipeline applications. The results of the extended temperature test showed that when heated to +350°C, the measurement error caused by the temperature coefficient of resistance does not exceed 1.2% after digital correction. Therefore, for the practical system, a “bridge-in-a-bridge” thermal compensation scheme was used, where one of the arms acts as a reference thermal control link.
The proposed system offers a compact solution for real-time strain monitoring in industrial settings. Its wireless functionality, thermal resilience, and measurement precision make it highly suitable for continuous diagnostics and early fault detection.

Research of dynamic characteristics of Si-photodiodes in the region of small currents using a computerized measuring complex

Oleg Kshevetskyi — 2025-06-30

Studying the current-voltage characteristics (IVC) of photodiodes, as well as any other device with a p–n junction, allows us to determine their quality and compliance with the stated requirements for reverse dark current. However, in the development and production of photodiodes, dark currents are usually investigated with the aim of achieving a certain level. The mechanisms of dark current generation are rarely studied in detail.

Some researchers are faced with the problem of the dynamics of small values of dark current (at the level of 10^–9 A), when the photodiode is a part of a high-resistance electrical circuit.

This study investigated the dynamic IVC of silicon photodiode samples in the zone of small currents using a newly developed, specialised, computerised system.

To carry out the research, we first tested the original computerised setup we had developed and manufactured by measuring the dynamics of dark currents of a UFD 337 type photodiode. The tests allowed establishing that the voltage changes within the range from +1.5 to –9 V (which can be expanded by using other power sources), the number of measurements of dark current values per second is up to 5000 (can be increased when using a higher-frequency controller), and the resolution when measuring dark current is 0.02 nA. During our research, we studied the behaviour of the dark currents of silicon photodiodes over a range their lower values: 10^–10–10^–7 A. The experimental results show that the investigated photodiodes have hysteresis of dynamic I–V characteristics in the range of currents of 1–10 nA at a negative voltage from 10 to 0 V.

If the diode structure is technologically perfect, then for static IVCs such hysteresis should either not exist at all or may be within the dark current measurement error, which is usually about 5%. In our case, the current drop in the hysteresis loop on the dynamic IVCs increases with the voltage change rate. On average, it is about 5 nA, which is much larger than the measurement error of 0.01 nA.

If the photodiode is intended for recording photocurrents below 1 nA (for example, low levels of illumination in photometry: 0.01 – 0.1 lux) or for operation in high-speed devices, then the detected hysteresis phenomenon can significantly distort the results of photocurrent measurement.

Thus, the detection of this hysteresis in the low-current region by the created complex can be used to test manufactured photodiode structures (crystals) prior to assembly into a housing. Such selection will be effective for precision photodiodes designed to measure small fluxes of optical radiation.

Photo receiver device of increased reliability and resistance to background lighting for FSO

Volodymyr Lipka — 2025-06-30

The exchange of information signals using optical channels is one of the main directions of development of modern telecommunication systems. Such communication channels include, in particular, the rapidly developing free space optical (FSO) technology. Since such communication is carried out in the open air, it is necessarily affected by optical interference, which is mainly created by solar radiation. Therefore, in FSO conditions, the issue of counteracting background illumination created by sunlight becomes relevant. It is capable of generating a large photocurrent of a photodiode that receives a useful optical signal. The question arises of how to filter the useful signal, which is transmitted at a certain wavelength (in our case, it is 980 nm), from the background signal of optical interference, which can suppress the useful monochromatic signal. This is especially important when the spectral ranges of sensitivity of the photodetector and the source of optical interference overlap.
Therefore, the purpose of the research and development was to create a design of a background-resistant photo-receiving device (PRD), operating at a wavelength of 980 nm, under the conditions of illumination of the photodiode by solar radiation.
To achieve the specified goal, a study of known technical solutions was conducted, which showed that the optimal design should be one that uses optical and electronic methods. In addition, the possibility of tracking the useful signal was shown, taking into account the time during which the photodetector reacts to irradiation of the working wavelength. Namely, the growth time of the photodetector. Thus, the counteraction to the background illumination of the photodetector consists in a combination of an optical cut-off light filter, an automatic gain control circuit that compensates for the component of the photocurrent caused by the constant frequency composition characteristic of solar radiation, as well as an algorithm for selecting the useful signal based on the growth time of the photodiode at the working wavelength. This selection, as well as the general operation of the PRD, is carried out and controlled using specialized software, which is loaded into the corresponding microcontroller. Studies of the created PRD have shown that it is resistant to background solar radiation of power up to 17 mW. A study of the reliability of the PRD and software has been conducted. The reliability of the PRD is at least 500 hours of operation.
The probability of failure-free operation of the software in the operating interval from 0 to 10 hours is at least 0.98.

Radiator temperature regimes for the cooling system of a powerful LED lighting device

Dmytro Kozak — 2025-06-30

High-power lighting devices based on LED sources are the most effective solution for the lighting at emergency rescue operations in emergency zones. At the same time the challenges with thermal management of chip on board (COB) LED elements becomes more significant, since increasing electric power leads to an increase in heat flux and LED die temperature which negatively affects their reliability and light characteristics. One of the ways to solve this problem is to use highly efficient two-phase heat transfer devices for the cooling systems, such as gravity-assisted heat pipes built into the base of several aluminum heatsinks. The authors carried out an experimental study of the temperature regimes of the aluminum heatsink at natural convection, taking into account the following factors: thermal power, environment orientation, and different locations of the heat source relative to the height of the heatsink. The results of experimental studies of the heatsink temperature parameters were used to verify the computer model. This enables the computer model to be used for thermal simulations and the optimisation of heat sink designs under free convection, taking into account radiation heat transfer over a wide temperature range and with different heatsink locations. The comparison of experimental data with simulation results confirmed that the computer model is adequate and can be used to design cooling systems based on gravity-assisted heat pipes for lighting devices.

Vaporization processes during cooling of miniature electronic devices

Vladimir Kravets — 2025-06-30

The widespread introduction of new technologies contributes to the rapid development of various fields of technology, both in terms of increasing the functionality of systems and equipment and reducing the weight and size characteristics of individual components and devices in general. This is especially evident in radio electronics, particularly in computer technology, where the heat flux densities emitted by individual electronic components can be very high. In such a case, the temperature of the chips increases and may exceed the maximum permissible values. To ensure the specified operating temperatures of electronic equipment, the bubble boiling process is used. The highest intensity of heat transfer is observed during boiling. This is due to the evaporation of a thin microlayer of liquid under the growing steam bubble.
This paper describes an experimental study of the peculiarities of the bubble boiling process on small surfaces. The experiment’s unique feature was the visual observation of the combined appearance and growth of a steam bubble, as well as the temperature pulsation of the surface beneath it. The process of bubble boiling occurred in a large volume at atmospheric pressure on small copper surfaces with a diameter of 0.4 to 5.0 mm. The surface temperature was recorded using a specially designed thermocouple. The signal from the thermocouple was fed through an amplifier to a two-beam oscilloscope. Using a system of mirrors, the process of evolution of the vapour bubble and surface temperature fluctuations were recorded on the film of a high-speed movie camera. The film speed varied from 800 to 4000 frames per second.
Experimental results have shown that both spherical and hemispherical vapour bubbles grow on the surface during boiling. Moreover, the surface temperature fluctuation depends on the size of such bubbles at the moment of their detachment. The larger the bubble bursting diameter, the greater the amplitude of the surface temperature fluctuations. It is shown that the main factor in increasing the intensification of heat transfer is the evaporation of a microlayer of liquid under the vapour bubble. The dependence of the surface temperature fluctuation on the values of the detachable diameters of the steam bubbles is obtained.
Thus, if bubble-boiling cooling systems are used to maintain the temperature regime of electronic devices, it is necessary to take into account the temperature fluctuations of the heat transfer surface, as they can affect the operating characteristics of the devices.

Thermal analysis of cooling systems based on two-phase heat transfer devices

Sergii Khairnasov — 2025-06-30

Lighting devices are critical tools for the emergency rescue operations at the dark as well for the other urgent actions directly in the area of emergency situations, since it is necessary to ensure a high level of illumination with constant intensity during the entire time of work. The current status of semiconductor technologies allows to create highly efficient high-power light sources, which allows to develop of a number of lighting systems based on LED sources (COB — chip-on-board — modules). But one of shortcoming of LED technology is a significant part of the electrical power is converted into the heat. So, such devices require special thermal management systems to ensure thermal requirements, which is determined primarily by the optical efficiency of COB modules and, accordingly, the total amount of electrical energy converted into heat. Today the heatsink based on passive two-phase heat transfer devices, such as heat pipes or vapor chambers, are widely used in the electronics and high-power LED lighting devices. In this case the thermal analysis of high-power LED lighting devices with such cooling systems at the early development stage is very important. So, in this work the thermal analysis of the three variants of high-power LED lighting device thermal management system with electrical power not less than 500 W was performed. The cooling systems designs based on aluminium heat sink with different two-phase heat transfer devices: heat pipes (copper powder heat pipes and aluminium grooved heat pipes), thermosyphons, pulsating heat pipes and vapor chamber were considered. The results of thermal simulation and their analysis of the above-mentioned cooling system variants options are shown in the paper. Based on thermal analysis of the cooling system design has been proposed and it has been shown that copper thermosyphons application with diameter 12 mm and with working fluid pentane in the aliminium heatsink increases its efficiency and ensures the heat dissipation at least 360 W by natural air convection into the environment at a maximum temperature of the LED COB module case of 100°C.