Introduction.  Data transmission systems using the  X-ray frequency range of electromagnetic radiation  –  X-ray communication system (XCS) have a number of advantages in comparison with radio or optical communication systems. The most significant advantages for practical use are their higher stealth and external interferences resistance, as well as stability against interception and decryption. It is of importance to develop a method for calculating the main parameters of an X-ray communication system: the range and speed of data transmission. In addition, the construction design and results of experimental research of the current X-ray communication system should be provided.

Aim.  To develop physical and technical foundations of data transmission systems using the X-ray frequency range of electromagnetic radiation.

Materials and methods.  We used an original method of calculating the X-ray emission spectrum, taking into account the attenuation coefficient in the propagation medium.

Results.  A technique for data transmission using the X-ray frequency range of electromagnetic radiation was suggested, including a method for calculating basic parameters e.g. the transmission range and speed, as well as the construction design of the current X-ray communication system model. Relations between these parameters and the operating modes of the X-ray tube were shown. The calculated and experimental data were in good agreement, sufficient for practical use. On their basis, it can be expected that at a voltage across the X-ray tube of 200 kV and the tube current of 1A in a 1-μs pulse, data transmission range in free air will be about 250 m. The maximum possible data transmission rate when using the developed X-ray tube will be 5 Mbit/s.

Conclusions.  The results of analytical and experimental investigations showed that the range and rate of data transmission of the XCS are exclusively determined by the transmitter energetic capabilities: by voltage and average the X-ray tube current during the generation of packages  (series) of the X-ray pulses, as well as by the duration of a single X-ray pulse. It is concluded that the prospects of XCS depend on the development of specialized X-ray sources generating a series of pulses with the minimum possible duration of every single pulse in a series. Taking into account the specific features, XCS can become an alternative to conventional radio and optical systems for communication and navigation.

Introduction.  Large-size phased antenna arrays (PAA) frequently incorporate optical excitation schemes, whose main elements include the feed and the reflective aperture. In turn, the reflective aperture consists of several tens of thousands of radiators and phase shifters. Major distortions of the radiation pattern in reflective arrays occur due to phase errors, leading to a decrease in the gain and an increase in the side lobes of the radiation pattern. In the millimeter wavelength range, ferrite phase shifters can have an initial phase from 0 to 360 °, thus requiring measurements of the array elements following their assembly.

Aim.  To develop a method for evaluating errors in measurements of the parameters of phase shifters incorporated in an antenna array by comparing theoretical and experimental data.

Materials and methods.  A convenient method for determining the parameters of phase shifters is probing, in which a movable probe is connected in series with each array element. In cases where a PAA element represents a single structure consisting of a ferrite segment and a dielectric radiator, measurements are carried out using a probe in the form of a segment of a round waveguide moving towards the radiator. In order to evaluate the measurement error of such a scheme, a mechanically controlled reference phase shifter was used.

Results. Measurement errors for the probe structure used were calculated based on the assumption of the phase error arising from the vector addition of the controlled and uncontrolled reflected signals at the input of the PAA element, in the section of the reference plane at the input of the probe. In addition, the S-parameters of the superposition section were calculated. The extrema of the error function were used to determine the maximum errors in measuring the phase and amplitude.

Conclusion. The performed analysis confirmed the validity of the proposed method for measuring the parameters of phase shifters using a waveguide probe. The measurement error of the PAA elements according to the proposed scheme was found to be about 3 o, which is commensurate with that of recording devices.

Introduction.  Range Cell Migration (RCM) is a source of image blurring in synthetic aperture radars (SAR). There are two groups of signal processing algorithms used to compensate for migration effects. The first group includes algorithms that recalculate the SAR signal from the "along–track range – slant range" coordinate system into the "along-track range  –  cross-track range"  coordinates using the method of interpolation. The disadvantage of these algorithms is their considerable computational cost. Algorithms of the second group do not rely on interpolation thus being more attractive in terms of practical application.

Aim. To synthesize a simple algorithm for compensating for RCM without using interpolation.

Materials and methods. The synthesis was performed using a simplified version of the Chirp Scaling algorithm.

Results.  A simple algorithm, which presents a modification of the Keystone Transform algorithm, was synthesized. The synthesized algorithm based on Fast Fourier Transforms and the Hadamard matrix products does not require interpolation.

Conclusion. A verification of the algorithm quality via mathematical simulation confirmed its high efficiency. Implementation of the algorithm permits the number of computational operations to be reduced. The final radar image  produced using the proposed algorithm is built in the true Cartesian coordinates. The algorithm can be applied for SAR imaging of moving targets. The conducted analysis showed that the algorithm yields  the  image of a moving target provided that the coherent processing interval is sufficiently large. The image lies along a line, which angle of inclination is proportional to the projection of the target relative velocity on the line-of-sight. Estimation of the image parameters permits the target movement parameters to be determined.

Introduction.  There  are  incidences  of  jamming  the  users  of  satellite  communication  systems,  who  apply  e.g. geostationary relay satellites, and the illegal use of such satellite resources. These actions can be both intentional and unintentional, and, among other things, be caused by non-compliance with electromagnetic compatibility standards on part of other users of satellite communication systems. For a prompt and high -quality response of radio monitoring services and satellite operators to these illegal  actions, it seems urgent to develop methods for accurate determination of the geolocation of radio emission sources.

Aim.  To develop a method for improving the accuracy of determining the coordinates of ground-based radio emission sources operating via geostationary relay satellites based on shared operation of a barrage jammer and reference signal sources.

Materials and methods.  The research was conducted using the statistical theory of radio engineering systems, the theory of digital signal processing and the method of simulation.

Results.  A  method  was  developed  for  improving  the  geolocation  accuracy  of  ground-based  radio  emission sources operating via geostationary relay satellites based on shared operation of a barrage jammer and reference signal sources. A method for resolving ambiguity regarding the true correlation peak of a reference source signal using a signal from a barrage jammer was described. An expression was obtained for the probability of a correct  solution  when  resolving  such  ambiguity.  As  a  result,  the  estimates  of  geolocation  accuracy  obtained using the developed method were compared with those obtained by a conventional method relying on the usage of 3 different reference stations.

Conclusions. The method proposed in this paper makes it possible to achieve a relatively high accuracy when determining the geolocation of ground-based radio emission sources in the Earth’s regions of interest, at the same time as involving no organizational and financial costs for the installation of a large number of reference stations.

Introduction.  Requirements for the quality of information about the trajectory of moving objects provided by sensor networks are increasingly becoming more stringent. For Information and Data Processing Centers (DPC) at control and management command posts, the issue of information mapping and forming the true trajectories of moving objects in the area of intersection of network detection zones is of particular importance. The use of conventional approaches to solving this problem involves issues  related to ensuring the efficient provision of users with complete and reliable information about trajectories in real time. In this article, wee propose a new approach to solving this problem using data mining theory, in particular, the methods of data clustering theory. Based on an analysis of the process of processing radar data in a DPC and its similarity with that of data clustering, we synthesized an algorithm for processing the trajectories of moving objects. The algorithm was verified by modelling and experimental research.

Aim.  To develop a generalized scheme for processing object trajectories (TP) in a DPC and to synthesized a TP algorithm using the methods of data clustering theory.

Materials  and  methods.  Data  Clustering  theory,  Systems   Engineering  theory,  Radar  Data  processing  theory (RD), methods of mathematical modelling and experimental research.

Results.  Based on an analysis of the essence of radar data processing (RD) in a DPC and its similarity with the process of data clustering,  an algorithm for processing the trajectories of moving objects was synthesized and verified by modelling and experimental research. A generalized scheme for processing the trajectories of moving objects in a DPC and a TP algorithm for a DPC were synthesized.

Conclusions.  An algorithm for processing object trajectories was proposed based on a new approach of data clustering theory. A generalized scheme and an algorithm for processing object trajectories (TP) in a DPC were suggested. These developments can be  effectively applied in various models, e.g. centralized, hierarchical and decentralized. The synthesized algorithm can provide output information about the true identified trajectories in terms of various indicators of data processing systems (DPS).

Introduction. The most common method for diagnosing cardiovascular diseases is the method of ECG monitoring. In order to facilitate the analysis of the obtained monitorograms, special software solutions for automated ECG processing are required. One possible approach is the use of algorithms for automated ECG processing. Such algorithms perform  clustering of cardiac signals by dividing the ECG into complexes of similar cardiac signals. The most representative complexes obtained by statistical averaging are subject to further analysis.

Aim. Development of an algorithm for automated ECG processing,  which performs clustering of cardiac signals by dividing the ECG into complexes of similar cardiac signals.

Materials and methods. Experimental testing of the developed software was carried out using patient records provided by the Pavlov First State Medical University of St  Petersburg. The software module was implemented in the MatLab environment.

Results. An algorithm for clustering cardiac signals with post-correction for the tasks of long-term ECG monitoring and a software module on its basis were proposed.

Conclusion.  The presence of a small number of reference cardiac signal complexes, obtained through ECG processing using the proposed algorithm, allows physicians to optimize the process of ECG analysis. The as- obtained information serves as a basis for assessing dynamic changes in the shape and other parameters of cardiac signals for both a particular patient and groups of patients. The paper considers the effect of synchronization errors of clustered cardiac signals on the shape of the averaged cardiac complex. The classical solution to the deconvolution problem leads to significant errors in finding an estimate of the true form of a cardiac signal complex. On the basis of analytical calculations, expressions were obtained for the correction of clustered cardiac signals. Such correction was shown to reduce clusterization errors associated with desynchronization, which creates a basis for investigating the fine structure of ECG signals.

Introduction.  Wireless diagnostics of patients’  functional state is important  for ensuring timely detection and treatment of diseases. In this article, the development of a medical hardware-software system for remote monitoring of the state of biological objects is considered on the example of cardiovascular diseases.

Aim. To develop a medical hardware-software system for remote monitoring of the main cardiovascular parameters and to expand the scope of medical remote telemetry equipment, which can eventually lead to improved medical services.

Materials and methods.  On the example of cardiovascular diseases, an analysis of the existing medical hardwaresoftware system for remote monitoring of the state of biological objects was carried out, taking into account the cardiac monitoring of the electrocardiogram. This method is widely used for in the diagnostics and treatment of cardiovascular diseases.

Results.  A  method  was proposed for creating  a  hardware-software  system  for  remote monitoring of the main cardiovascular parameters to ensure timely detection and treatment of diseases. The general structure of such a system, including its advantages and disadvantages and the routing of information, is described.  The proposed technology of  prolonged  remote monitoring of the patient's health state makes it possible to increase  the efficiency of detecting dangerous heartbeat arrhythmia by about 30%.

Conclusions.  The  proposed system  solves  the  problem of registering biological parameters without significant interference in the patient’s vital  activity, which allows typical conditions to be traced. Remote data collection also facilitates the load on medical personnel, reduces the number of contacts with patients and improves their psychological state.