To detect and classify objects, the source trajectories detected in the process of hydroacoustic observation are used, which contain information about the measured parameters of objects, which are their classification attributes. The analysis of these attributes allows to make a decision about the class of the observed object, for example, a surface or underwater source. As the measured object parameters are used their energy characteristics, parameters of the observed trajectory (bearing, speed of change in bearing and other possible trajectory parameters). In this case, the correctness and speed of the decision on classification depends on the quantity and quality of used classification signs, which are determined by both parameters of the observed object, and the features of sound propagation from the source to the observation device.For signal detection and resolution, we further consider fast projective adaptive algorithms, the use of which, as applied to the problems of in-situ experimental signal detection was considered in [1], [4]. The goal of this class of algorithms is to provide a high probability of detection and accurate measurement of the parameters of the source trajectories under the conditions of a model of multi-beam propagation and scattering in the real ocean environment [5]-[8]. The proposed work is a continuation of the work [1], [4], and aims to ensure the use of experimental field data not only for detection, but also for the classification of the observed sources.The subject of the study are the results of the full-scale experiment of hydroacoustic noise direction finding, given earlier and described in detail in [1], [4]. For the experiment was used antenna of L = 56 vertical daisy chains (of 10 elements each), equidistantly spaced horizontally. The antenna was installed at a depth of 200 meters in the coastal marine zone of the coastal wedge near the shipping lanes. The elements of the flat antenna were affected by signals from surface ships moving ncontrollably in the observation area and one underwater source.A singular decomposition of sampled antenna element data was used to construct adaptive algorithms. Modification of the initial results of singular decomposition allows to create algorithms that provide priority conditions for extraction of separate components of the observed (e. g., weakest) signals when constructing direction finding terrain.In this regard, in addition to the non-adaptive direction finding relief, it is proposed to form three variants of direction finding relief, each of which solves part of the general problem of selection and classification of individual varieties of observed signals:– Initial, corresponding to the energy of the signals of the input sample with amplified components of the weakest signals (overview algorithm);– direction finding relief, which uses an algorithm to detect weak and scattered signals;– direction finding terrain, which highlights the coherent components of signals.Analysis of the trajectories of more than 30 sources in the episode of two hours and forty minutes has been carried out, which increased the reliability of the detection and measurement accuracy of the parameters of the observed objects. Joint analysis of the trajectories of sources based on different variants of the bearing relief allowed to improve the conditions for the detection of weak signals and to make classification decisions using the classification attribute of the width of the area of fluctuations of the surface target trajectory for signals with a strong scattered component.

The article presents the basic relations for correcting sampling estimates of the correlation matrices of adaptive algorithms for detecting the weakest signals in complex interference conditions. The proposed algorithms were used to process field data obtained from a multielement planar array deployed in a maritime zone at a depth of 200 m in coastal wedge conditions. The paper describes the method for processing field data and presents the results of constructing direction-finding reliefs for the case of more than 25 maritime navigation sources in the field of view. It is demonstrated that adaptive algorithms aimed at detecting the weakest signals can yield better results than those obtained by classical adaptive and nonadaptive algorithms.

The relationships for optimizing a selective estimate of the correlation matrix of classical (initial and modified) and fast projection algorithms in a complex noise situation were determined. Model investigations on the comparison of the resolution of classical optimized algorithms with the characteristics of two variants of fast projection algorithms were performed. The algorithms were compared using the criterion of a decrease in the time and reduction of the angular zone of the loss of a contact with a weak target when it intersects the path of an intense interfering signal. The relationships that correspond to the most economical realization of the fast algorithm were determined.

The problem of detecting weak signals in complex noise situations using projection adaptive algorithms is considered. The existing algorithms are analyzed, and a novel algorithm oriented at detecting weak signals is proposed. Results of the algorithm’s operation are demonstrated in a simulated noise situation consisting of interference signals with different intensities under the assumption of their multipath propagation and scattering. The proposed algorithm is compared with the well-known classical Capon algorithm, and a significant reduction in the contact loss time as applied to a low-noise target near strong interference sources is demonstrated.

Рассмотрены различные методы оптимальной и адаптивной обработки гидроакустических сигналов в условиях многолучевого распространения и рассеяния. Приводится анализ положительных и отрицательных сторон классических адаптивных алгоритмов (алгоритмов Кейпона, MUSIC, Джонсона) и “быстрых” проекционных алгоритмов в условиях многолучевого распространения и рассеяния сильных сигналов. Представлены классические оптимальные подходы по обнаружению многолучевых сигналов. Для обеспечения автоматического обнаружения слабых сигналов предлагается механизм контролируемого нормирования сильных сигналов. Представлены результаты моделирования работы различных алгоритмов обнаружения на линейной эквидистантной антенной решетке в условиях многолучевого распространения и рассеяния. Проводится анализ автоматического обнаружителя на основе классических или быстрых проекционных алгоритмов, проводящего оценку фона на основе медианной фильтрации или методом двустороннего пространственного контраста.

This paper presents results on evaluating the impact of a set of physical and technical factors on the effectiveness of classical and projection fast adaptive algorithms. The factors include the conditions of signal propagation, including multipath; the noise-signal situation; signal fluctuations due to scattering in the medium; the parameters of the receiving antenna, including the amplitude-phase value of element dispersion; and the parameters of the spectral signal analysis at the output of the antenna elements.

Приводятся результаты оценки влияния на эффективность адаптивных алгоритмов обработки гидроакустических сигналов совокупности физических и технических факторов, к которым относятся: условия распространения сигнала, в том числе многолучевые; помехо-сигнальная ситуация; флуктуации сигнала, обусловленные рассеянием в среде; параметры приемной антенны, в том числе величина амплитудно-фазового разброса элементов; параметры спектрального анализа сигнала на выходе антенны, а также применение классических или быстрых проекционных алгоритмов.

Different methods of optimal and adaptive processing of hydroacoustic signals for multipath propagation and scattering are considered. Advantages and drawbacks of the classical adaptive (Capon, MUSIC, and Johnson) algorithms and “fast” projection algorithms are analyzed for the case of multipath propagation and scattering of strong signals. The classical optimal approaches to detecting multipath signals are presented. A mechanism of controlled normalization of strong signals is proposed to automatically detect weak signals. The results of simulating the operation of different detection algorithms for a linear equidistant array under multipath propagation and scattering are presented. An automatic detector is analyzed, which is based on classical or fast projection algorithms, which estimates the background proceeding from median filtering or the method of bilateral spatial contrast.

The specific features of detecting signals and estimating their parameters in the far-field zone of an antenna in the presence of intense interferences in the near-field zone are considered using modern adaptive algorithms. An imitative simulation shows the possibilities of the adaptive methods for localizing sources in the far- and near-field antenna zones.

The problem of resolving a weak broadband signal against the background of a strong broadband signal using adaptive superresolution algorithms for signals with distorted coherence is considered. The correlation matrix is estimated using not only time but also frequency accumulation with a differently formed focusing matrix. Imitative simulation has been carried out and the simulation results are analyzed.

Рассматриваются особенности обнаружения и оценки параметров сигналов в дальней зоне антенны при наличии интенсивных мешающих сигналов в ближнем поле антенны с помощью современных адаптивных алгоритмов. При помощи имитационного моделирования показываются возможности адаптивных методов по локализации источников в дальней и ближней зонах антенны.