No 3 (2024)

Relevance. The effectiveness of a radar system depends on both the system's inherent reliability and the accuracy of its output measurements. When checking the reliability of measurements, it's challenging to define specific numerical values for false alarm rates and the omission of unreliable measurements, since it is difficult to compare the effect of omitting an unacceptable measurement error with the costs associated with addressing the consequences caused by a false alarm.

Goal. The indicated problem necessitates further research into ways of improving methods for monitoring the reliability of radar measurements. In response, the authors propose an approach for optimizing radar measurement reliability control based on interval estimation using confidence probability.

Materials and methods. The proposed approach addresses the identified issue by assuming that the impact of both false alarms and unacceptable errors is essentially the same, as both result in reduced accuracy of radar measurements. In the case of a false alarm, the cost is defined by the corrective action taken by the radar tracking system, which introduces a compensatory value proportional to the unreliable measurement. This allows us to treat the cost of the error as the weighted average variance between the unreliable measurement and the compensatory value.

Results. To validate the effectiveness of the proposed approach, simulation modeling was conducted to analyze the joint probability density of radar measurements and interfering influences with varying intensities, up to their maximum. The modeling considered the full range of potential unreliable measurements in the radar system, as well as boundary noise dispersion (based on the simulation results) and the measurement reliability used in technical system calculations.

Conclusions. The findings showed that constructing confidence intervals of a specified size to ensure the required reliability of radar measurements can be reduced to finding the extremum of a specific functional, subject to certain constraints.

Introduction. Radiothermography is a promising medical diagnostic technique that detects the body's natural radio emissions. Variations in physiological properties, such as temperature and electrophysical characteristics, alter the noise temperature of tissues, signaling potential abnormalities. The efficiency of microwave thermometry increases with focusing, which can be achieved using antenna arrays. However, in the context of human diagnostics, the compactness of array elements is critical due to the limited space within the body.

This study aims at assessing the performance of a developed antenna applicator for use in a multilayer model of brain tissue and proving its functionality in experiments. Electrodynamic modeling was performed using CST STUDIO, a software suite for designing, simulating, and optimizing 3D electromagnetic systems. To evaluate the antenna's performance, a tissue phantom was created to replicate the dielectric properties of real human tissues.

Findings. A compact antenna-sensor for contact radiothermometry was developed, operating at a frequency of 3.85 GHz with a 50 MHz bandwidth. The design addresses the challenge of fitting array elements into a small volume. The experimental results correlated with the electrodynamic model, confirming the functionality of the antenna applicator. Its performance was optimized for a multilayer structure of brain tissue using a below-cutoff waveguide design.

Introduction. Publisher-Subscriber technology is an effective tool for organizing real-time interactions between moving and stationary objects, as well as facilitating asynchronous message exchange between system components.

The aim of the research was to improve the efficiency and reliability of communication between moving and stationary objects for use in robotic systems (RTS). The paper discusses the most popular implementations of Publisher-Subscriber technology, including SocketIO-based brokers, hbmqtt, Mosquitto, and RabbitMQ. The study evaluates the computational resources consumed by these implementations, specifically RAM usage, CPU utilization, and client connection times to the brokers.

Findings. Implementation results for the RabbitMQ broker: RAM consumption was 86 MB, and CPU utilization was 0%. For the Mosquitto broker, RAM consumption was 6 MB, and CPU utilization was 0%. The SocketIO-based broker consumed 32 MB of RAM, with 0% CPU utilization. The hbmqtt-based broker used 30 MB of RAM and 0% CPU. The following results demonstrate resource consumption under load. RabbitMQ: RAM consumption was 94 MB, with CPU utilization at 14.3%. The message sending rate was 4,000 messages/second. During the first 15 seconds, latency increased but then dropped to minimal levels, and the broker delivered all subsequent messages with minimal latency. Mosquitto: RAM consumption was 12 MB, with CPU utilization at 17%. The message sending rate was 18,000 messages/second. At 54,000 messages/second, latency exceeded 18 seconds. SocketIO: RAM consumption was 34 MB, with CPU utilization at 3.3%. The message sending rate was 36,000 messages/second. Latency gradually increased, with a 99.8% message loss. hbmqtt: RAM consumption was 60 MB, with CPU utilization at 99.7%. The message sending rate was 20,000 messages/second. At 60,000 messages/second, latency increased to 45 seconds.

Conclusion. It is quite clear from the data that the RabbitMQ broker demonstrates the best performance. Although, it has a limitation of 4,000 messages per second, this does not hinder message passing. Instead, it helps minimize delays and reduces system load. RabbitMQ also offers functionality that is either absent or difficult to implement in the other brokers evaluated.

Practical significance. The results can be applied to further implement Publisher-Subscriber technology for organizing interactions between moving and stationary objects, with the potential for scaling these interactions in RTS.

Introduction. In various applications, such as qualitative and quantitative real-time air monitoring for managing greenhouse gas concentrations and assessing the efficiency of solar panels—both of which are influenced by ambient temperature and relative humidity—there is a significant demand for groups of combined fiber-optic sensors (CFOS). These sensors utilize Fabry-Perot resonators (FPR) and fiber Bragg gratings (FBG) arranged in a quasi-distributed manner, including configurations that are remotely spaced from the data collection and processing points. Each CFOS group requires a reference sensor (RCFOS) dedicated solely to monitoring air parameters, ensuring the reliability and calibration of measurements.

The aim of this work is to formulate design challenges and evaluate the feasibility of implementing a multi-parameter RCFOS for monitoring air parameters, including temperature, pressure, and relative humidity. This implementation aims to enhance metrological and functional characteristics based on the Vernier effect and Edlen equations, while also providing cost-effective address multiplexing and interrogation within multi-sensor networks based on address fiber Bragg structures (AFBS) and microwave photonic technologies.

Methods. A critical metric used to characterize the optical Vernier effect is the sensitivity enhancement factor, or M-factor. This factor compares the Vernier envelope with the interference signal from the measuring FPR. A high M-factor can be achieved through two-parameter parallel measurements, such as air pressure and temperature, or by sequentially activating independent interferometers to monitor each parameter separately, for example, air temperature and relative humidity. The AFBS is a fiber Bragg structure with an optical frequency response that includes two narrow-band FBG components separated by a unique address frequency in the radio frequency range. This address frequency remains constant, even when the AFBS undergoes deformation or temperature changes. The microwave photonic principle of AFBS interrogation allows the inclusion of several structures with the same central wavelength but different address frequencies in a single measurement network. This setup facilitates the parallel interrogation of the RCFOS while minimizing the impact of external physical parameters on the information transmitted through the fiber, making it narrow-band for each sensor.

Conclusion. The research proposes a concept for developing an RCFOS for multi-sensor quasi-distributed networks that enable qualitative and quantitative real-time monitoring of air parameters. Key elements of the concept include a new technology for manufacturing the FPR section within the single fiber structure using catastrophic melting effects for improved reliability in field conditions and microwave photonic technology to simplify interrogation subsystems. The last one employs radiation generated in the AFBS section of the sensor, which was previously used only for reference temperature control. Estimates indicated that the RCFOS designed based on this concept can measure ambient temperatures ranging from -60°C to +300°C with a sensitivity of approximately 13 pm/°C using AFBS. Additionally, it can measure temperatures from +10°C to +60°C with a sensitivity of approximately -500 pm/°C using a sequential FPR scheme. Relative humidity can be measured with a sensitivity of roughly 400 pm/%RH within the 20% to 90% RH range, while air pressure can be measured with a sensitivity of approximately 400 pm/MPa up to 0.5 MPa using the parallel FPR scheme.

Problem. The multifactor distortions inherent in HF radio channels pose significant challenges in designing effective signal processing systems that ensure reliable information transmission. Addressing this issue requires the development of HF communication link simulators capable of diagnosing channel conditions and interference. Leveraging client-server control technology presents promising new avenues for enhancing communication channel diagnostics.

Objective. This study aims at developing an ionospheric HF radio link simulator utilizing GNU Radio technology and a client-server methodology to manage the system effectively.

Findings. The study presents a novel approach and hardware-software implementation of an ionospheric HF radio link simulator based on GNU Radio technology, incorporating client-server control. The simulator models the transmission and reception of spread spectrum communication signals within the GNU Radio environment. Key algorithms implemented include the synthesis of the emitted spread spectrum signal and the digital processing of the received signal. Experimental testing validated the simulator's ability to accurately replicate the transmission characteristics of HF radio links. The developed simulator serves as a practical test model for HF radio communication links, supporting the design of radio engineering systems that utilize diverse coherent signal reception.

Practical significance. The HF radio link simulator offers a valuable tool for testing and developing radio communication systems, particularly those involving diverse coherent signal reception.