ДОПЛЕРОВСКАЯ ФИЛЬТРАЦИЯ РАДИОЛОКАЦИОННЫХ СИГНАЛОВ, ОТРАЖЁННЫХ ОТ МАЛОСКОРОСТНЫХ ВОЗДУШНЫХ ОБЪЕКТОВ
Authors: Леговцова Е.В. , Кудряшова О.Е. , Фитасов Е.С. , Васильев Д.А. 
Published: February 2025

В статье проведено исследование проекционного метода доплеровской фильтрации радиолокационных сигналов при обнаружении малоскоростных воздушных объектов на фоне интенсивных отражений от местных предметов. Были синтезированы группы фильтров с различной шириной зоны режекции, обеспечивающих обнаружение целей на фоне отражений от местных предметов в заданном диапазоне радиальных скоростей. Был проведён анализ зависимости нормированных коэффициентов передачи полезного сигнала от его частоты Доплера для разных значений длины выборки сигнала и параметров доплеровского фильтра (количества нулей зоны режекции).

Introduction.Paper addresses the studies of the projection method of Doppler filtering of radar signals for detecting low-speed small-sized aircrafts, including ones contaminated with intensive reflections from local objects. Such aircrafts include light-engine aircraft with propeller engines, helicopters, powered hang gliders (hang-gliders), unmanned aerial vehicles - UAVs (mini- and micro-UAVs, including multicopters). It should be noted that the problem of detecting and recognizing mini- and micro-UAVs in the context of urban conditions, taking into account their rapid technical development and widespread use both for special and commercial purposes, will become topical in the near future for theoretical and applied radar. The aimof the research was to estimate the efficiency of the projection method of Doppler filtering of radar signals reflected from air objects with low radial velocities. Research methods. To solve the problem of minimizing losses in the detection of a useful signal, works proposed and analyzed a method of inter-period processing, that stems from the optimal procedure of detecting a useful signal contaminated with an interference with given correlation properties. The method implies the approximation of the inverse correlation matrix of the interference by the matrix-projector onto the subspace that is orthogonal to the subspace of the interference. Compared to the existing quasi-optimal methods of inter-period processing, the proposed method is the most effective in case of the presence of intense interferences. This is proved by its structure that is similar to the optimal Bayesian filtering algorithm with a known interference correlation matrix. In addition to this, one of the significant advantages in terms of practical implementation of the projection method, in comparison with the optimal procedure for calculating the weight vector, is that there is no need for performing computational procedures associated with the estimation of the interference correlation matrix and the calculation of the inverse matrices for each element of resolution in real time. Findings. Simulation allowed to synthesize groups of filters with different widths of the rejection zone, ensuring detection of targets contaminated with reflections from local objects in a given range of radial velocities. Besides, there are presented the outcomes of the analysis of the dependence of the normalized transmission coefficients of the useful signal on its Doppler frequency for different values of the signal sample length and the Doppler filter parameters (the number of zeros in the rejection zone). Conclusions. An increase in the sample length with the parameter of the Doppler filter of the projection method M = 1 ensures detection of air objects with radial velocities close to zero with minimum losses in the signal-to-noise ratio (for the case in question at N = 150, the minimum value of the radial velocity of the object is roughly 4 m/s).