RU2754200C1 - Method for panoramic detection of objects making noise in the sea - Google Patents

Abstract

FIELD: hydroacoustics.

SUBSTANCE: invention relates to the field of hydroacoustics and is intended for the detection of objects simultaneously observed in the sector survey of noise direction finding. The method is based on the reception of a hydroacoustic noise process by a multi-element antenna with a developed aperture in the horizontal plane and the formation of a set of spatial channels in the viewing sector, in each of which time-frequency processing of the noise process is simultaneously carried out. The results of time-frequency processing of the process in a set of spatial channels are centered and normalized to interference with the measurement of the set of signal-to-noise ratios in spatial channels, after which a decision is made to detect an object in the spatial channels in which the measured signal-to-noise ratio exceeds the threshold. When implementing the method, a set of accumulation times τ_i is set, where i is an ordinal number from 1 to “x”, each of which is optimal for a specific tangential velocity of the object, “x” time-frequency processing operations of the process with accumulation times τ_i is simultaneously carried out in each spatial channel, respectively, and based on the results of centering, normalization and comparison of the signal/noise ratio with the threshold, a decision is made on detecting an object with a specific tangential velocity.

EFFECT: increase in the signal-to-noise ratio for all noisy objects simultaneously observed in a sector survey, regardless of the speed of their angular movement.

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Description

The invention relates to the field of hydroacoustics and is intended to detect objects simultaneously observed in a sector survey of noise direction finding.

The task of a panoramic view of space in a horizontal plane has always been posed by the developers of hydroacoustic noise direction finding equipment [Koryakin Yu.A., Smirnov SA, Yakovlev GV. Ship sonar technology: state of the art and topical problems. SPb .: Nauka, 2004].

Known methods of detecting objects noisy in the sea [Antipov VA, Velichkin SM, Obchinets OG, Pastor A.Yu., Podgaysky Yu.P., Yanpolskaya A.A. RF patent No. 2353946 dated 04/27/2009. A method of obtaining information about objects noisy in the sea. MPK G01S 3/80, Antipov V.A., Velichkin S.M., Podgaysky Yu.P. RF patent No. 2339050 dated 20.11.2008. A method for detecting objects noisy in the sea. IPC G01S 3/80, G01S 15/04], in which a simultaneous sector (panoramic) survey of the noise space in the horizontal plane is carried out by a static fan of directivity characteristics (HN), where a set of separate channels of time-frequency signal processing at the output of each HN lobe is realized. The methods allow detecting noisy objects and determining the direction towards them. However, if the movement of the signal between the lobes of the directional characteristics in the horizontal plane is faster than the selected accumulation time interval, object detection may be difficult.

The closest analogue of the tasks to be solved and the procedures performed to the proposed invention is a method for detecting objects noisy in the sea [Antipov VA, Velichkin SM, Podgaysky Yu.P., Yanpolskaya AA. RF patent No. 2300118 dated 05/27/2007. A method for detecting objects noisy in the sea. IPC G01S 3/80], which was taken as a prototype.

The prototype method performs the following operations:

receive a hydroacoustic noise signal by a multi-element antenna with a developed aperture in the horizontal plane,

a set of spatial channels is formed in the survey sector (horizontal fan of directional characteristics), in each of which the time-frequency processing of the signal is simultaneously carried out, for which the quadratic detection, frequency filtering and accumulation of the process in time are sequentially carried out,

centering and normalizing signals to interference according to the totality of the processing result in spatial channels with measuring the totality of signal / noise ratios,

make a primary decision on signal detection in those spatial channels in which the measured signal-to-noise ratio exceeds the primary threshold,

carry out tracing of the object along the angle when the detected signal passes between spatial channels,

carry out additional accumulation of signal energy in the process of tracking,

reject falsely detected signals and make the final decision on object detection.

The disadvantage of the prototype method is the use of a time-frequency processing of one fixed accumulation time. Most often, when implementing the method, a short accumulation time is used. This is due to the fact that objects with high angular velocity can exist in the field of view. Usually, these are close objects of high noise. Such objects move rapidly in the horizontal plane, constantly passing along a fan of directivity characteristics from one lobe to another lobe, lingering within one spatial channel for a short time. Therefore, in time-frequency processing, for the possibility of detecting such objects, a short accumulation time is chosen, consistent with the time interval of the object being in one spatial channel.

However, in the field of view, other objects can simultaneously exist that have a low angular velocity. Usually, these are distant objects with low noise. Such objects move slowly in the horizontal plane, being in one spatial channel for a long time. The short accumulation time, when it is chosen when implementing the prototype method, does not allow sufficient accumulation of the signal of an object of low noise. This leads to the fact that some objects cannot be detected. For the possibility of detecting such objects in the prototype method, a small primary detection threshold is selected, and then an additional accumulation of signal energy is carried out during the tracking process. This leads, on the one hand, to the initial false detection of non-existent objects, and on the other hand, to an increase in processing time.

On the other hand, if a long accumulation time is chosen during the implementation of the prototype method, then it may be difficult to detect objects that have a high angular velocity. Such objects are delayed within a single spatial channel for a short time, as a result of which in a spatial channel with a long accumulation time, not a signal, but a noise, begins to accumulate. This also leads to the fact that some objects cannot be detected.

The objective of the proposed method is to increase the possibility of detecting all noisy objects simultaneously observed in the sector survey, regardless of their angular velocity.

To solve the set problem in the method of panoramic detection of objects noisy in the sea, in which the hydroacoustic noise process is received by a multi-element antenna with a developed aperture in the horizontal plane, a set of spatial channels in the viewing sector (horizontal fan of directivity characteristics) is formed, in each of which frequency and time processing of the noise process, for which the quadratic detection, frequency filtering and accumulation of the process are sequentially carried out, the results of the time-frequency processing of the process in the set of spatial channels with the measurement of the set of signal-to-noise ratios are centered and normalized to the interference, a decision is made to detect an object when the measured ratio is exceeded signal / interference threshold value,

new features have been introduced, namely:

set the set of accumulation times τ _i = ϕ / V _i , where ϕ = const is the angular distance between the axes of the adjacent lobes of the directional characteristics, V _i is the set of tangential velocities of the object, i is the serial number from 1 to n,

in each spatial channel simultaneously carry out n frequency-time processing of the process with accumulation times τ _i , respectively,

the results of each of the time-frequency processing of the process are separately centered and normalized to the interference by the set of spatial channels with the measurement of individual sets of signal / noise ratios R _i , respectively,

the decision on object detection is made for those spatial channels in which at least one signal-to-noise ratio from the sets R _i exceeds the threshold value,

consider that an object with tangential velocity V _{i is} detected if the signal-to-noise ratio from the set R _{i is} maximum.

The technical result of the invention is to increase the signal-to-noise ratio for all noisy objects simultaneously observed in the sector survey, regardless of the speed of their angular movement, which increases the noise immunity during detection. And also the possibility of dividing the detected objects according to their tangential velocity is additionally provided.

Let us show the possibility of achieving the specified technical result by the proposed method.

It is known [Zaraisky V.A., Tyurin A.M. Sonar theory. L .: Naval Academy. 1975] that the ability of the time-frequency processing channel to detect a weak signal increases with increasing accumulation time. This is due to the fact that the signal-to-noise ratio Q at the channel output increases in proportion to the accumulation time:

where q is the signal-to-noise ratio at the input of the processing channel, Δ f is the total frequency bandwidth, τ is the accumulation time.

In this case, it is necessary that the object signal be present at the channel input during the entire accumulation time.

Systems with a static fan of directivity characteristics as separate inputs of time-frequency processing channels have a set of separate directions in the horizontal plane. A noise object, being mobile, moves in the horizontal plane between different inputs of time-frequency processing. The time t, during which the mobile object is at the input of one fixed spatial channel (the input of one time-frequency processing) depends on the angular (tangential) velocity of the object V and the angular distance between the axes of adjacent lobes of the directivity characteristics ϕ:

t = ϕ / V

The choice of the accumulation time in the time-frequency processing channel, close to the time the object is at the channel input, will allow the most effective use of the channel's ability to detect a weak signal.

Due to the fact that the tangential velocity of objects simultaneously observed in a sector survey can be different, it is advisable to use simultaneously several processing channels with different accumulation times, each of which will be most effective for its own range of angular velocities of objects. For example, for a set of speed ranges [0, V ₁ ], [V ₁ , V ₂ ],… [V _n-1 > V _n ], we obtain a set of time ranges, during which such objects are at the input of one fixed spatial channel [∞, t ₁ ], [t _1, t ₂ ],… [t _n-1 > t _n ], where t ₁ = ϕ / V _i , ϕ = const. Then, to ensure the highest value of the signal-to-noise ratio for each speed range, according to (1), it is most efficient to use the set of accumulation times τ ₁ = ∞, τ ₂ = t ₁ , ... τ _n = t _n-1 , for each of which to carry out its time-frequency processing. In this case, in each channel of time-frequency processing, the maximum accumulation time possible for optimal detection of an object with a specific angular velocity will be used and the maximum value of the signal-to-noise ratio for such an object will be obtained. Here, as the value of τ _i, it is necessary to choose the maximum time possible from practical considerations. This will allow, firstly, to increase the possibility of detecting all noisy objects simultaneously observed in the sector survey, regardless of their angular velocity, and secondly, to divide the detected objects according to their angular (tangential) velocity.

The essence of the invention is illustrated in FIG. 1 and FIG. 2. In FIG. 1 shows an enlarged block diagram of a device that implements the proposed method. FIG. 2 shows a diagram of signal processing inside the blocks of the device (FIG. 1).

The proposed method is technically implemented by hardware and software according to the block diagram shown in Fig. 1, on the basis of a generalized structural diagram of a typical hydroacoustic system of noise direction finding [Koryakin Yu.A., Smirnov SA, Yakovlev G.V. Ship sonar technology: state of the art and topical problems. SPb .: Nauka, 2004]. The block diagram includes series-connected blocks: antenna 1, block 2 of the directional characteristics formation system (SFHN), block 3 of time-frequency processing (QMO), block 4 for measuring the signal-to-noise ratio (R), block 5 of a threshold detector (PO), block 6 determination of tangential velocity (V).

With the help of the equipment (Fig. 1), the claimed method is implemented as follows. A preliminary analysis is made of the range of tangential velocities of objects for which the implemented equipment is intended to detect, and the angular distance between the axes of adjacent lobes of directional characteristics. The number of time-frequency processing channels n is selected and the set of accumulation times τ _{i is set} for each channel according to the claims. In the process of operation, the noise signal of the object, received by the antenna 1, enters the SFHN unit 2, where a set of spatial processing channels is formed in the horizontal plane. FIG. 2 spatial channels are designated as PKj, where j = l, m. The noise signal of each spatial channel is simultaneously fed to the QMO block 3, in which a set of n channels of time-frequency processing is formed for each spatial channel. FIG. 2 shows a diagram for two channels of time-frequency processing n = 2, which are designated as BBOj1 (the first channel of time-frequency processing for nKj) and BOj2 (second channel of time-frequency processing for PCj). In each channel of time-frequency processing, quadratic detection, frequency filtering and process accumulation are carried out simultaneously. In the first channel BOj1, the accumulation is carried out during the time τ ₁ . In the second channel BOj2, the accumulation takes place during the time τ ₂ . The results of processing all spatial channels for both channels of time-frequency processing are simultaneously fed to block 4 R. In block 4, the results of time-frequency processing of the process in the set of spatial channels are centered and normalized to interference separately for two time-frequency processing. As a result, two sets of signal-to-noise ratios are formed: R ₁ is the set of signal-to-noise ratios Qj1, obtained as a result of the first time-frequency processing of QBOj1, and R ₂ is the set of signal-to-noise ratios Qj2, obtained as a result of the second time-frequency processing of BOj2. Both sets of signal / noise ratios are simultaneously fed to unit 5 of the software. In block 5, in each spatial channel, a comparison with a threshold of two signal-to-noise ratios is performed. If any of the signal-to-noise ratios exceeds the threshold, then a decision is made to detect an object in this spatial channel. Simultaneously, both sets of signal-to-noise ratios arrive at block 6 V, where at the same time a decision on object detection is received from block 5. If Qj1> Qj2, then it is considered that the detected object has a tangential velocity corresponding to the accumulation time in the first channel of time-frequency processing. Otherwise, the object is considered to have a tangential velocity corresponding to the accumulation time in the second time-frequency processing channel. The number of time-frequency processing channels can be two (as shown in the diagram of Fig. 2) or more. A larger number of channels will allow for more accurate tuning of the method for optimal detection of objects with different angular velocities.

All of the above allows us to consider the problem of the invention solved. A method is proposed for the panoramic detection of objects noisy in the sea, intended for the detection of objects simultaneously observed in the sector survey of noise direction finding.

Claims (1)

A method for panoramic detection of objects noisy in the sea, in which a hydroacoustic noise process is received by a multi-element antenna with a developed aperture in the horizontal plane, a set of spatial channels in the viewing sector (horizontal fan of directivity characteristics) is formed, in each of which time-frequency processing of the noise process is simultaneously carried out, for which the quadratic detection, frequency filtering and accumulation of the process are sequentially carried out, the results of the time-frequency processing of the process in the set of spatial channels with the measurement of the set of signal-to-noise ratios are centered and normalized to interference, a decision is made to detect an object when the measured signal-to-noise ratio exceeds the threshold value , characterized in that: set the set of accumulation times τ _i = ϕ / V _i , where ϕ = const is the angular distance between the axes of adjacent lobes of directional characteristics, V _i is the set of tangential velocities th object, i is a serial number from 1 to n, in each spatial channel n time-frequency processings of the process are simultaneously carried out with accumulation times τ _i , respectively, the results of each of the time-frequency processings of the process are separately centered and normalized to interference by the set of spatial channels with the measurement of individual sets of signal-to-noise ratios R _i , respectively, the decision to detect an object is made for those spatial channels in which at least one signal-to-noise ratio from the sets R _i exceeds the threshold value, it is considered that an object with tangential velocity V is detected _i , if the signal-to-interference ratio from the set R _{i is} maximum.

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