RU2791163C1 - Method for detecting probing signals - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: invention relates to the field of hydroacoustics and can be used to build systems for detecting sonar signals in modern hydroacoustic systems. In a method comprising sequential reception of probing signals from a moving source, in which time points t_i of reception of n probing signals are sequentially measured along their leading edge, where n is at least 3, the time interval T_k and between the moments of reception of each two successive signals is determined T_k = t_i+1 - t_i, the difference between the measured time intervals T_k+1 - T_k is determined, where T_k+1 = t_i+2 – t_i+1, t_i+1 and t_i+2 - the time of receiving signals following one after another and the signal that arrived at time t_i, the amplitudes of each received signal are measured, the duration

of each received signal is measured at a level of 0.7 of its amplitude, the average value of the duration

and its standard deviation

are determined for 3 consecutive signals, and if the duration of each subsequent signal lies within

of all detected signals, only those signals that satisfy the condition (t_i + t_i+2)/2 = t_i+1 ± (T_k – T_k+1) are selected and considered as received probing signals.

EFFECT: increasing the reliability of the estimation of the required parameters due to the elimination of false signals and the influence of the movement of the receiver of the probing signals, which distort the measurement results.

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Description

The invention relates to the field of hydroacoustics and can be used to build systems for detecting sonar signals in modern hydroacoustic systems.

Probing signals emitted by sonar located on various carriers, including mobile ones, can be detected at long distances using well-known systems for detecting sonar signals (Yu.A. Koryakin, S.A. Smirnov, G.V. Yakovlev "Korabelnaya hydroacoustic technology, St. Petersburg Nauka, 2004, pp. 89-92). When these signals are detected, the problem of measuring the parameters of the probing signal arises.

Known methods for detecting the location of the source of probing signals, described in the work of A.A. Prostakov "Hydroacoustic means of the fleet" M. 1974, p. 90. The paper considers the problem of determining the location of a random target emitting impulse signals when using several receiving posts.

A known method for measuring the change in the heading angle of movement of the source of probing signals according to the patent of the Russian Federation No. 2515419, publ. the detection threshold is determined, the amplitude of the spectral readings exceeding the threshold is measured, the amplitudes of the spectral readings having the maximum amplitude are determined and stored, and the change in the heading angle of the source movement is determined through the ratio of the difference of the measured successive frequencies.

The disadvantage of this method is that it uses the processing of long probing signals, which has a limited place in the practice of hydroacoustic means. In most cases, sonars are used that emit probing signals of short duration, with a wide spectrum, which will not allow one to select spectral readings for measuring their difference.

A known method for measuring changes in the heading angle of movement of the detected source of probing signals according to the patent of the Russian Federation No. 2545068, publ. March 27, 2015, according to the procedure closest to the proposed method. In this method, probing signals of a moving source are sequentially received, the moment of arrival of the first received probing signal is determined, the time moments t _i of receiving n more probing signals, where n is at least 3, are sequentially measured, the time interval T _k between the moments of arrival of each two following one after another probing signals T _k =t _i+1 - t _i , determine the difference between the measured time intervals ΔT _m =T _k+1 - T _k , where m is the measurement number of the difference of successive time intervals, a T _k+1 =t _{i+ 2} - t _i+1 determine the sign of the difference in time intervals (ΔT _m+1 - ΔT _m ). This difference determines whether the source is approaching or moving away, and in relation to each subsequent difference to each previous difference in time intervals, the magnitude of the change in the heading angle of movement of the probing signal source is determined.

The disadvantage is that there are errors in measuring the time position of the probing signal due to the presence of multipath during propagation, resulting in the formation of signals similar to the probing signal in the immediate temporal vicinity of the main signal, and signals re-emitted by sources of biological origin. The temporal position of such signals is random, which distorts the reliability of processing the parameters of the true source of probing signals. (Timoshenkov V.G. "Statistical assessment of the structure of a noise-like hydroacoustic signal under conditions of positive refraction and sea waves" NTS Hydroacoustics issue 35 St. Petersburg 2018 JSC Concern Okeanpribor, "Ocean Acoustics" edited by Brekhovskikh L.M. Nauka M 1974, p. 128).

In addition, the considered relations are valid if the receiver of probing signals is stationary, and if it moves, then an error occurs associated with the speed of movement and with the direction of movement of the receiver relative to the position of the source of probing signals.

The objective of the invention is to improve the reliability and reliability of the detection of the probing signal.

The technical result of using the proposed invention is the elimination of false signals and the influence of the movement of the receiver of the probing signals, which distort the measurement results, which will increase the reliability of the estimation of the desired parameters.

каждого принятого сигнала на уровне 0,7 от его амплитуды, определяют среднее значение длительности

и ее среднеквадратическое отклонение

по 3-м последовательным сигналам, и если длительность каждого последующего сигнала лежит в пределах

из всех обнаруженных сигналов выбирают только те сигналы, которые удовлетворяют условию (t_i+t_i+2)/2=t_i+1±(T_k - T_k+1), и считают их принятыми зондирующими сигналами.The technical result is achieved by the fact that in a method containing sequential reception of probing signals from a moving source, in which time points t _i of reception of n probing signals are sequentially measured along their leading edge, where n is at least 3, the time interval T _k between the moments of reception is determined each two consecutive probing signals T _k =t _i+1 - t _i determine the difference between the measured time intervals T _k+1 - T _k , where T _k+1 =t _i+2 - t _i+1 , t _{i +1} and t _i+2 - the time of reception of signals following one after another and for the signal that arrived at time t _i , new features are introduced, namely: measure the amplitude of each received signal, measure the duration

of each received signal at a level of 0.7 of its amplitude, determine the average value of the duration

and its standard deviation

on 3 consecutive signals, and if the duration of each subsequent signal lies within

from all the detected signals, only those signals are selected that satisfy the condition (t _i +t _i+2 )/2=t _i+1 ±(T _k - T _k+1 ), and consider them to be received probing signals.

Let us explain the achievement of the technical result.

As a rule, the operation of a probing signal source (SS), which is a sonar, aims to survey the space and detect an object by the presence of an echo signal from it. The propagation range of the probing signal is significantly greater than the detection range of the echo signal from the object detected by this signal. Therefore, the probing signal is detected by the receiving device of the sonar signal detection system (OGS) almost always at the very first emission signals. The amplitude of the received direct propagation probing signal is large and always significantly exceeds the noise. It is known that the presence of multipath leads to the fact that during propagation the number of signals at the receiving device increases, which distorts the reliability of the measurement process. In this case, the input of the receiving device receives several signals with random amplitudes that exceed the interference, random arrival times and random durations.

поэтому зондирующим сигналом следует считать тот, который удовлетворяет условию (t_i+t_i+2)/2=t_i+1±(T_k - T_k+1).For a source of probing signals (sonar), the durations of the probing signals are fixed; therefore, when propagating from approximately the same distance, the durations of the probing signals will not change significantly when measured at a fixed level from the amplitude. The presence of multipath is a random event, as a result of which the signal propagates along random trajectories, which are determined by the mutual position of the transmitter and receiver, as well as the presence of reflection from the surface and from the bottom. In this case, the signals that propagate along the main beam have constant parameters in duration and amplitude, while the signals propagating along other beams have a random travel time from the source to the receiver and a significant fluctuation of amplitudes and durations. Thus, for reliable detection of a probing signal, it is necessary, first of all, to measure the amplitude and duration of the received signal. For a direct propagation signal along the main beam, the durations of consecutively received signals will be equal if they are measured at the same level from the maximum amplitude. Since the amplitudes fluctuate, the measured durations will also differ from each other. It is known that the difference in the reception times of each two successive probing signals will also differ slightly from each other. The signal reception time t _i =t ₀ +D ₀ /C, where C is the speed of sound. The time of the moment of radiation t ₀ is unknown to us and the distance between the sonar and the receiver D ₀ is also unknown. When the speed of the sonar V is the time of receiving the second signal: t _i+1 =t ₀ +T+(D ₀ - VT)/C, where Τ is the time between the emission of probing signals. Then the difference T _k between the reception time of the signal t _i and the signal t _i+1 : T _k = Τ (1-V/C). The time of receiving the signal t _i+2 following the signal t _i+1 : t _i+2 =t ₀ +2T+(D ₀ - 2VT)/C, and the difference between the time of receiving these signals T _k+1 =Τ (1 -V/C). In this case, it should be taken into account that all the values of T, C, V practically do not change during the radiation time. Therefore, the sequence of real probing signals will always satisfy the condition (t _i +t _i+2 )/2=t _i+1 . However, here it is necessary to take into account the non-uniformity of the own motion of the receiver of probing signals, the non-uniformity of the movement of the sonar, which emits probing signals, and the fluctuations of amplitudes during the propagation of probing signals. In this situation, the time of receiving probing signals will randomly fluctuate. The magnitude of fluctuations is unknown, but approximately it will be determined by the difference between the values

therefore, the probing signal should be considered the one that satisfies the condition (t _i +t _i+2 )/2=t _i+1 ±(T _k - T _k+1 ).

The essence of the invention is illustrated in Fig. 1, which shows a diagram of the implementation of the proposed method.

The device (figure 1) contains a receiving antenna 1 connected to a special processor 2, which includes a series-connected receiving device 3, which forms a static fan of directivity characteristics, a block 4 for detecting signals in selected spatial channels, a block 5 for determining signal amplitudes, a block 6 for selecting signals of the required duration, block 7 for determining the time position of the leading edge of the signals, block 8 for selecting probing signals according to the required condition.

It is advisable to consider the implementation of the proposed method together with the description of the operation of the device (Fig. 1).

The sounding signals of a moving source (sonar) are received by the OGS system antenna 1 and fed to the input of the receiving device 3, where they are amplified, filtered and converted into digital form, convenient for further processing and measurement with the required accuracy. Antenna 1, receiver 3 are well-known devices implemented in systems for detecting sonar signals OGS. The signals converted into digital form are processed by special digital processors based on the developed algorithms (see Yu.A. Koryakin, S.A. Smirnov, G.V. Yakovlev "Ship hydroacoustic technology" St. Petersburg Science 2004, pp. 164-176 , pp. 278-295). All systems for detecting sonar signals are designed using a static fan of directivity characteristics, which provide a circular view of space, since the direction of arrival of the sounding signal is a priori unknown.

поступают в блок 7 определения временного положения их переднего фронта. Определение временного положения по максимуму амплитуды сигнала вводит дополнительную ошибку, поскольку амплитуда на самой длительности может флюктуировать и изменяться случайно, что скажется на погрешности определения временного положения. Измеренные временные положения принятых сигналов, имеющих требуемую длительность, поступают в блок 8 выбора зондирующих сигналов по условию (t_i+t_i+2)/2=t_i+1±(T_k - T_k+1). Соблюдение этого условия обеспечивает отсев сигналов, которые могут формироваться случайно. Их временное положение будет случайным и не связано с предыдущим и последующим излучением, что характерно для гидролокатора.The signals received by all directional characteristics enter the signal detection block 4, where the standard detection procedure for exceeding the threshold is performed: signals that exceed the threshold enter block 5, where their amplitude is measured, which is transmitted to block 6 for selecting signals of the required duration. Signal durations are determined at the level of 0.7 of their amplitude. The probing signals of real sonars have a fixed duration, which does not change when propagating along the main beam. If the signal propagates along several beams, then several signals are added and their duration increases. Signals whose duration lies within

enter block 7 to determine the temporary position of their leading edge. Determining the time position by the maximum signal amplitude introduces an additional error, since the amplitude at the duration itself can fluctuate and change randomly, which will affect the error in determining the time position. The measured time positions of the received signals having the required duration are fed into the block 8 for selecting probing signals according to the condition (t _i +t _i+2 )/2=t _i+1 ±(T _k - T _k+1 ). Compliance with this condition ensures the elimination of signals that can be generated randomly. Their time position will be random and not related to the previous and subsequent radiation, which is typical for sonar.

Thus, an increase in the reliability and reliability of the detection of probing signals in the conditions of multipath propagation and the presence of unauthorized signals is provided.

Claims (1)

A method for detecting probing signals, comprising sequential reception of probing signals from a moving source, in which time points t _i of receiving n probing signals are sequentially measured along their leading edge, where n is at least 3, the time interval T _k is determined between the moments of reception of each two following each one after the other probing signals T _k =t _{i+1 -t i} determine the difference between the measured time intervals T _k+1 - T _k , where T _k+1 =t _i+2 - t _i+1 , t _i+1 and t _i+2 - the time of receiving signals following one after another and the signal received at time t _i , characterized in that the amplitudes of each received signal are measured, the duration is measured

of each received signal at a level of 0.7 of its amplitude, determine the average value of the duration

and its standard deviation

on 3 consecutive signals, and if the duration of each subsequent signal lies within

from all the detected signals, only those signals are selected that satisfy the condition (t _i +t _i+2 )/2=t _i+1 ±(T _k - T _k+1 ), and consider them to be received probing signals.

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