Radioelectronics and Communications Systems

Image compression and transmission system for LoRa networks

2026-10-30T11:08:59+02:00

Significant advantages of LoRa networks for Internet of Things applications include long-range communication, low energy consumption, and high noise immunity. When applied to image transmission, the primary constraint of a LoRa network is its low data rate, which is characteristic of LPWAN technologies. Usually, images in such networks are transmitted with low resolution. To enable greater-resolution image transmission through the LoRa network, this paper proposes preliminary image processing. This method uses the discrete Haar wavelet transform (DHWT) and JPEG compression. Compared to standard JPEG compression alone, the proposed method reduces the processed image file size by a factor of 1.4–2.9. The paper estimates the effect of LoRa parameters on the transmission of processed images. For instance, it considers the selection of the DataRate and Code Rate parameters to ensure an operational transmission cycle of 1% (36 seconds per hour). As a result, the compression quality level, the number of wavelet transform iterations, and the choice of LoRa network parameters are adjusted.

Method for detecting amplitude jumps in signal processing using their local correlation between windows

2026-10-30T10:45:10+02:00

Rapid changes in signal parameters in the form of “spikes” or “dips” often convey important information about the condition of a technical or other object or the surrounding environment, such as the sudden appearance of obstacles in the path of a vehicle, etc. Such information can be widely used in robotics, radar, medicine, and other fields. The main task is to detect “jumps” or “drops” (hereinafter referred to simply as jumps) with a probability of at least a specified threshold, and in some cases to determine their parameters (amplitude or duration). Detection of jumps by traditional methods is not possible, since they have a short duration and are nearly imperceptible in the signal spectrum. This paper proposes a new window-based method for detecting amplitude jumps in signals and presents simulation results under navigation conditions for autonomous mobile robots searching for ground landmarks. It is shown that the correlation coefficient of a random signal between windows shifted by a certain time interval can change significantly when an amplitude jump appears in one of the windows. As a result, in most cases, the jump in signal amplitude is transformed into a jump-like decrease in the correlation coefficient, and the requirements for selecting window widths and the time shift between them have been substantiated. The probabilities of correct detection of an amplitude jump, a skip of a jump, and a false alarm under various application conditions are calculated. The effectiveness of the proposed method is assessed by using the ROC curve, which characterizes the performance quality of a binary classifier. The obtained results are compared with the Kullback–Leibler information measure and the results of the well-known PELT method.

Band properties of dipole antennas with corner screen at maximum directivity. Bandwidth

2026-10-30T10:51:45+02:00

Based on the asymptotic solution of the three-dimensional vector problem of dipole field diffraction on an ideally conducting corner of finite dimensions within the framework of the method of uniform geometric theory of diffraction, high-speed algorithms and software programs in the FORTRAN environment have been developed for calculating 3D radiation patterns (RP), directivity factor (DF), and radiation resistance of corner antennas when changing their dimensions, aperture angles, and the dipole distance from the inner edge of the corner (dipole–edge distance) over a wide range of operating wavelengths. For antennas with different aperture angles excited by a half-wave vertical dipole, optimization was performed to maximize DF. The maximum DF values depending on the dipole–edge distance, the corresponding radiation resistances, and the optimal screen dimensions at the resonant wavelength were determined. For optimal corner dimensions at a fixed dipole–edge distance of one-quarter of the resonant wavelength and at optimal dipole distances for antennas with different aperture angles, the DF and radiation resistance were calculated in the range from 0.1 to two resonant wavelengths. A quantitative analysis of the passband width of such antennas was performed. It was revealed that at a distance of one-quarter of the resonant wavelength, two passbands are formed only for a flat screen, and the passband width decreases as the antenna aperture angle is reduced. When the dipole distance is increased and a corner screen is used, two and three resonant bandwidths can be distinguished. For flat screens of optimal dimensions, calculations of DF dependencies on wavelength using proprietary software were verified by comparison with DC values calculated with the commercial FEKO software package.

Frequency resolution of nonparametric method for processing complex signals under impact of additive interference

2026-10-30T10:57:39+02:00

This paper presents a study of the nonparametric SG statistic as a criterion function for estimating the probability of separating broadband pulse signals based on Doppler frequency in the presence of additive interference. It is assumed that a priori information regarding the probability density function of the additive interference is not available. The interference under consideration is a random process consisting of independent and identically distributed (IID) random variables. A comparative analysis has been performed to solve the problem of separating signals by Doppler frequency using a target function based on the SG statistic, with its solution obtained by the maximum likelihood method, when the signals are additively distorted by Gaussian interference. A sufficient statistic for the maximum likelihood method is the cross-correlation function between the observation and the expected signal. Estimates of the signal separation probability using the nonparametric SG statistic were obtained for various values of the Doppler frequency shift and the signal-to-noise ratio. The results of a statistical simulation of the signal separation problem using the SG statistic, compared with the maximum likelihood method, demonstrate the effectiveness of signal separation in the absence of a priori information about the interference distribution density.

Matrix photonic modulators with toroidal varizon topology for massive 6G MIMO systems

2026-10-30T11:04:25+02:00

This paper presents a new architecture for matrix-based photonic IR modulators with toroidal varizon topology, designed for the sixth-generation (6G) massive MIMO systems. A model for integrating toroidal modulators into a matrix structure with 8×8 subarrays and flexible row-column control is proposed to ensure high channel density, low power consumption, and high-speed performance. Analytical calculations of RC delays, energy per bit, effective capacitance, and integration density were performed, as well as numerical simulations of the distribution of the varizon field E_g(r) for a single element and a matrix with different configurations. The results of FDTD (finite-difference time-domain) simulations of spectral characteristics and an investigation of the effect of parasitic capacitances on operating speed are presented. Comparative characteristics of arrays of various sizes (8×8, 16×16, 64×64) are presented, along with an analysis of scalability and integration into photonic platforms for 6G. It has been shown that the use of local drivers and a reduction in the wiring line lengths allow us to reduce the effective capacitance by a factor of 1.5–3, and the proposed architecture, based on the results of analytical evaluation and numerical simulation, potentially allows for a reduction in power consumption to 0.5–0.8 pJ/bit at a maximum modulation frequency of up to 100 GHz and a scalability of more than 4096 channels. Potential applications for high-speed communication systems, coherent optics, and hybrid photon-electron computing systems have been discussed.