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The propagation factors measured for several propagation paths above the water surface are compared with the results of calculations for two modern coverage prediction systems. In calculations, numerical values of the parameters characterizing the current state of the environment observed at moments of signal measurements are used as initial data. It is demonstrated that both systems provide good accuracy for the line-of-sight and twilight zones, but the prediction accuracy is unsatisfactory for the scatter propagation.

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Numerical solution of the wave parabolic equation on a rectangular grid is analyzed, when the method of discrete split-step Fourier transform (FT) is used to calculate the values of the field in an inhomogeneous medium at the next step in the range. The goal was to identify the limiting possibilities of the FT method itself, so studies were carried out for the case of radio wave propagation in free space. Two related problems were solved: what is the minimum value of the root-mean-square error (RMSE) of the field calculation and what should be the values of the transfer coefficients of the Fourier series harmonics and the values of the coefficients of the artificial absorbing layer (AL) both depending on the parameters of the computational scheme. It is shown that the dependence of the RMSE on the distance to the source always has the maximum. The forms of the optimal AL differ from those traditionally used primarily due to the presence of a significant imaginary component.

Простая аппроксимация дискретной функции Грина в частотной области при численном решении параболического уравнения Рассматривается задача расчета параметров электромагнитного поля путем численного решения параболического уравнения методом дискретного преобразования Фурье с расщеплением. Определены точные значения коэффициентов передачи отрезков плоских волн от источника излучения на расстояние x в однородной среде (дискретная функция Грина для спектральной области) и описан характер их зависимости от поперечного размера прямоугольной области расчета. Для ближней зоны предложена простая экспоненциальная аппроксимация дистанционной зависимости этих коэффициентов, использование которой не меняет традиционного алгоритма расчета, но существенно повышает его точность. Ключевые слова: распространение радиоволн, параболическое уравнение, метод дискретного преобразования Фурье.

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The principles of operation of active-pulse television systems used in robotic complexes, remotely controlled or Autonomous unmanned vehicles are considered. A mode control device is provided that allows to increase the depth of the visibility range and the efficiency of the systems in various environmental conditions as a result of scanning the observation zone by distance.

The systems intended for detecting objects of artificial and natural origin are widely used while implementing the remote sensing methods. In this case, such different frequency ranges of sounding signals as radar, acoustic and optical ones are used. This article presents the results of patent analysis of the detection systems for such groups of the International Patent Classification as G01S13, G01S15, G01S17. The analysis has been carried out using the database of the United States Patent and Trademark Office (USPTO) inventions registered from 2015 to 2019. The aim of the given study was to compare the development trends of the object detection systems using the reflection or reradiation of radio-, acoustic or electromagnetic waves. It is shown that the proposed approach makes it possible to identify the promising (breakthrough) technological directions, as well as to form predictive estimates of their development in the short-term.