Radioelectronics and Communications Systems

Theoretical estimates of vacuum conductivity of nonlinear channel of short-focus electron beam transport

Igor Melnyk — 2024-02-25

The paper presents analytical relationships obtained for calculating the vacuum conductivity of a nonlinear electron beam transport channel, the geometry of which is described by the power law dependence of the channel radius on the longitudinal coordinate. The dependences of the length of the transport channel on the pressure in the process chamber and also on the inlet and outlet radii of the channel are derived and analyzed. The obtained theoretical results are of practical importance for designing sputtering and welding electron beam equipment based on high-voltage glow discharge electron guns. The results of calculated data have been verified experimentally for a cylindrical transportation channel with an input diaphragm. To harmonize the theoretical and experimental data, a correction factor was introduced into the calculation formula to determine the length of the channel, and the value of this factor was adjusted based on the results of the experimental studies. The resulting relative difference between the calculated and experimental data does not exceed 15%. The calculated results obtained in this study can be used to optimize the geometry of the transport channel to achieve minimal losses of electron beam current in the channel.

Mathematical modeling of moving FMCW radar: signal at receiver input

O. I. Pavlov — 2024-02-25

The paper presents models that allow us to determine the influence of the primary parameters of a moving radar on the features of secondary signals that occur in the receiver when calculating the range of a moving target. This makes it possible to model various signal processing methods, determine the limitations of these methods, and formulate recommendations for the construction and the hardware and software solutions that should be included in the scheme of a moving radar that tracks a moving target.

It has been shown that applying an equilateral triangular LFM law with period 20 µs in a probing signal with carrier frequency 24 GHz and frequency deviation 250 MHz makes it possible to determine the range of a moving target relative to a moving radar. The distance between them is defined uniquely using a coherent processing of received signals. The ideal case of signal propagation has been considered.

Method for estimating average recovery time of radioelectronic equipment after short-term storage

O. S. Babii — 2024-02-25

Radioelectronic equipment (REE) for military purposes is used periodically during exercises; at other times, it is stored on a short-term basis. As is known, the failure rate of elements during storage is reduced by 10–100 times compared to the operation of REE, which leads to the accumulation of hidden defects. Therefore, the maintenance and, if necessary, routine repairs are performed before the field deployment. Depending on the storage conditions (open area, under a canopy, unheated or heated storage) and its duration, the number of hidden defects will vary, which affects the time of preparation (repair) of REE before its use. However, this circumstance is not considered in the known methods of quantitative assessment of partial and complex reliability indicators that do not allow us to predict in advance the time required to restore the operability of REE after short-term storage. The paper proposes a method for estimating the average recovery time of REE after short-term storage, and the functional dependencies of reliability indicators on the initial data and controlled variables depending on the quality of metrological and diagnostic support are obtained and studied. The possibility of practical implementation of conditional diagnostic algorithms (CDA) for diagnosing multiple defects with a quantitative assessment of the total number of checks is investigated. The proposed method is formalized as a block diagram of the algorithm, which allows us to predict the average recovery time of REE after the short-term storage, depending on the initial data. Examples of the use and evaluation of the effect of the implementation of the obtained recommendations in the practice of technical operation of REE under actual conditions are presented. This makes it possible to schedule the work of military repair bodies and effectively use their forces and facilities.

Modeling millimeter wave channels with generative adversarial networks

Yahia Ahmed Zakaria — 2024-02-25

Modern cellular systems increasingly rely on concurrent communication across several discontinuous bands due to broader bandwidth and macro-diversity. Multi-frequency communication is crucial in millimeter wave (mmWave) and terahertz (THz) frequencies, frequently paired with lower frequencies for resilience. Statistical models capable of representing the combined distribution of channel routes over many frequencies are needed to assess these systems. This research presents a broad neural network-based training approach for multi-frequency double-directional statistical channel models. The suggested method involves representing every channel as a multi-clustered set and training a generative adversarial network (GAN) to generate random multi-cluster profiles. The resulting cluster data consists of vectors distributed at various frequencies with random received powers, angles, and delays. Urban micro-cellular connections at 28 and 140 GHz are modeled using ray tracing data to demonstrate the methodology. The model is readily adaptable for multi-frequency link or network layer simulation. As studies show, the model may capture intriguing statistical correlations between frequencies, and the technique involves minimal statistical assumptions.

Increasing sensitivity of sensors-converters of light and magnetic field based on unijunction transistor

I. M. Vikulin — 2024-02-25

Generators based on unijunction transistors (UJT) are used as sensors of light and magnetic fields, the output parameter of which is generation frequency depending on a measured value. This paper shows experimentally the possibility of a significant increase in sensitivity of such sensors by connecting a bipolar transistor (BT) in a connection variant with an open base in the UJT emitter circuit; the current of this BT is dependent on a light flow and magnetic field. Such a generator based on UJT and BT can be used as a radiation and magnetic field sensor. The UJT can also be applied in industrial optical couplers, where it is an input element with contactless control by the alternation of LED. The possibility of additional contactless control of the optic coupler with an external magnetic field extends their functional possibilities.