RU2585401C1 - Device for detecting objects in aqueous medium - Google Patents

Abstract

FIELD: electronics.

SUBSTANCE: invention represents an electronic device and relates to hydroacoustics and sonar. Device is intended for search and detection of artificial underwater objects, such as sunken ships, equipment, underwater vehicles, pipelines and other artificial underwater structures. Device comprises receiver (hydroacoustic antenna) (1), amplifier unit and band-pass filters (2), unit of analogue-to-digital converters (ADC) (3), matched filters (4), signal generator sending (5), power amplifier (6), measuring device (7), computer (8) and detector (9). Function of unit of matched filters is optimal for receiving reflected echo signal on background noise. Function of measurement device is a measurement parameter shape distribution and characteristic frequency echo signal at output of matched filter. Computer function is calculated ratio parameter shape and characteristic frequency echo signal. Function of detector is comparison of obtained number at output of computer with a threshold value and making a decision: detected unknown object location or not.

EFFECT: technical result is reduction of random errors and increased reliability of detecting an object in presence of noise and interference.

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Description

The invention relates to the field of sonar and sonar and is intended for the search and detection of artificial underwater objects, such as sunken ships, equipment, underwater vehicles, pipelines and other artificial underwater structures.

From the analysis of the prior art, the known “Sonar detection and classification of underwater and surface targets for surface ships” [RF Patent 20389, G01S 15/02, published October 27, 2001], containing a multi-element acoustic antenna, multi-channel radiation and reception paths connected to the acoustic the antenna, a digital computer system containing a master oscillator connected to the radiation path, a device for digital processing of echo signals connected to the output of the receiving path, and a display and control panel, characterized in that the structure of the digital signal processing device additionally includes a device for generating a classification sounding signal connected to the input of the radiation path parallel to the master oscillator, and a device for digital processing and classification of the echo signal of the classification sounding signal, the input of which is connected to the output of the spatio-temporal processing device for digital processing of the echo signals.

There is also known “A method for detecting an echo signal of a sonar” [RF Patent 2293358, G01S 15/04, published 02.10.2007], which contains the radiation of a sounding signal, receiving an echo signal with a hydroacoustic antenna mixed with noise interference, sampling the electrical signal at the output of a sonar antennas, a set of sampled samples of an electrical signal of duration T, obtaining sequentially, at regular intervals over the entire time of detection of sets of sampled samples of an electrical signal, and quick conversion Fourier analysis of the obtained sets of discretized samples, in this case, for each set of discretized samples of the electrical signal, the complex spectrum is determined, the sets are shifted for a time of 1 / 8T <T <1/2 T, each previous and each subsequent complex spectrum is stored, and the mutual spectrum between each previous is determined and with each subsequent set, select the set with the maximum energy spectrum, which decide on the detection of the signal.

All the solutions known above and other known existing echo-signal detectors in the sonar compare the level of the noise and signal totality with the noise level, and when the specified threshold is exceeded, the decision is made that the desired object has been detected [Evtutov A.P., Mitko V.B. Engineering calculations in hydroacoustics - L .: Shipbuilding, 1988. - p. 34]. To increase the detection range, a consistent technique is used, which allows to obtain a higher signal-to-noise ratio (SIR) at the output of the matched filter.

The disadvantage of this approach is the fact that there is a theoretical limit for the SIR at which such detection is possible with a given probability of false alarm. This leads to a limitation of the maximum range of the detector at a given probability of false alarm.

Closest to the proposed one is the "Underwater object detection device for assessing the measure of randomness of the sonar echo signal" [RF Patent 83344, G01S 15/04, published May 27, 2009], containing a receiver unit (sonar antenna), the function of which is to send a location signal and echo reception, block of analog-to-digital converters (ADC), block of amplifiers and bandpass filters, the function of which is to amplify the signal at the output of the hydroacoustic antenna to the levels necessary for the operation of the ADC, block filters, the function of which is to optimally receive the reflected echo signal against the background of interference, a sending signal generator, a power amplifier, a fractal dimension meter, configured to evaluate a measure of randomness of the amplitudes of the echo signal at the output of a matched filter and express this measure as a number (fractal dimension), a detector whose function is to compare the received number with the threshold of signal energy and interference and make a decision: the desired location object was detected or not .

The disadvantage of this device is that measuring the fractal dimension of various objects (natural and artificial) is an ambiguously solved problem, since there is no exact definition of the very concept of fractal dimension [Mandelbrot B. Fractal geometry of nature. - M.: Institute for Computer Research, 2002. - Page 31; Feder E. Fractals: Per. from English - M.: Mir, 1991. - Page 19] and, as a rule, the required amount of data is missing. Therefore, the fractal dimension of any formation is measured indirectly - by the slope of the dependence of the measured value on the scale, which leads to the appearance of a random error when the approximation is ambiguous and, as a result, the threshold boundary is eroded and detection ambiguity arises.

The technical result of the application of the proposed device is to reduce random error and, therefore, to increase the reliability of detection of an object in the presence of noise and interference.

The specified technical result is achieved by the fact that in the device for detecting underwater objects containing a receiver unit, a unit of amplifiers and bandpass filters, a unit of analog-to-digital converters, a unit of matched filters connected to a measuring device, a send signal generator, a power amplifier and a detector, according to the claimed invention , the measuring device is configured to measure the distribution shape parameter and the characteristic frequency of the echo signal at the output of the matched filter pa and is connected with the calculator relationship shape parameter distribution and characteristic frequency of the echo signal, the output of the calculator is connected to the input of the detector.

The measuring device comprises an ascending echo ranking unit, an echo sample size calculation unit, first and second echo signal ratio-to-average echo signal average ratio calculation units, a block specifying a scaling factor, a first and second multiplication unit, and a division unit, wherein the measuring device is configured to supply an echo signal in parallel to an input of an echo signal sample size calculation unit, an input of a first ratio calculation unit the erected value of the rectified rectified echo signal to the average rectified increment value and the echo signal ranking block input in ascending order, the second unit for calculating the ratio of the erected signal average rectified value to the average rectified echo increment value, the output is connected to the inputs of the first multiplication unit a block specifying the scaling factor and the output of the second block for calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo-s drove, the output of the block for calculating the sample size of the echo signal and the output of the first block of multiplication are connected with the corresponding inputs of the second block of multiplication, at the output of which the value of the shape parameter of the distribution of the echo signal is generated, while the output of the first block of calculating the ratio of the average rectified value of the echo signal to the average rectified value increments of the echo signal and the output of the first multiplication block are connected with the corresponding inputs of the division block, at the output of which the value of the characteristic frequency of the echo signal is generated la. The essence of the technical solution is illustrated by drawings, where

- in FIG. 1 shows a block diagram of an apparatus for detecting underwater objects;

- in FIG. 2 is a block diagram of a measuring device;

- in FIG. 3 and FIG. 4 shows the characteristic forms of the echo signals and their characteristics at the input of the measuring device for the case when the object is not detected (Fig. 3) and detected (Fig. 4).

The device for detecting objects in the aquatic environment contains a receiver unit (hydroacoustic antenna) 1, a unit of amplifiers and bandpass filters 2, an analog-to-digital converter unit 3, a matched filter unit 4, a signal generator 5, a power amplifier 6, a measuring device 7, a calculator 8, and detector 9.

The device for detecting objects in the aquatic environment can be made in the form of a separate printed circuit board with an external transceiver antenna, in the form of several boards or as part of a sonar complex.

The hydroacoustic antenna 1 is located separately from the remaining units of the device to ensure direct contact with the aquatic environment. Any hydroacoustic antenna can act as an antenna, either a piezoacoustic or an induction antenna, an antenna array or a single transceiving element.

The block of amplifiers and bandpass filters 2 and the power amplifier 6 are analog and should be located as close as possible to the antenna to reduce electrical noise in the device for detecting objects in the aquatic environment.

The amplifier and bandpass filter 2 can be implemented on operational amplifiers, consist of one or more stages, and the main requirement for this unit is to receive at the input of the block of analog-to-digital converters (ADCs) 3 echo signals in a given frequency band and with a given coefficient gain.

The block of analog-to-digital converters 3 is an interface between the analog and digital parts of the board, and is structurally located on the digital part. The ADC unit uses standard analog-to-digital conversion chips with the required bit depth, sampling rate and interface.

The blocks of the generator 5, the matched filter 4, the measuring device 7, the calculator 8 and the detector 9 belong to the digital part of the board and can be made in the form of a processor or microcontroller.

The matched filter 4 is calculated to detect a signal of a previously known shape generated by the generator unit, while the output signal of the filter does not coincide in shape with either the input or the signal for which the filter is intended to be detected. The signal with which the filter is matched, however, if it is present in the input signal with noise, allows you to get the maximum amplitude of the filter output signal, that is, this filter maximizes the signal-to-noise ratio for a known signal.

The generator 5 is digital, located inside the processor, and performs the function of generating a probe signal at predetermined times. For reliable operation of the detector, such signals can be either simple short signals or complex signals of long duration.

A power amplifier 6 is needed to provide the maximum detection distance by providing maximum signal energy.

The fundamental difference of the proposed device is the use in it of a measuring device that measures two parameters - the parameter of the shape of the distribution of the echo signal and its characteristic frequency, as well as a calculator of the ratio of the results of these measurements.

The measuring device 7 is designed to measure two parameters of the echo signal - the parameter of the distribution shape and the characteristic frequency. These parameters were first used in the work [Gorshenkov A.A., Klikushin Yu.N. Representation of signal models in the system of identification parameters [Electronic resource] // Journal of Radio Electronics. - 2010. - No. 9. - Access mode: http://jre.cplire.ru], for the quantitative assessment of the set of samples of which any quantized and discretized signal consists.

The physical meaning of the parameter of form A is that it numerically characterizes the shape of the distribution of the echo signal.

The physical meaning of the parameter F, called the characteristic frequency, consists in the fact that it determines the number of local eponymous extrema of the same name per unit time. The characteristic frequency for periodic signals is numerically equal to their natural frequency.

Empirically, the authors of the work [Gorshenkov A.A., Klikushin Yu.N. Representation of signal models in the system of identification parameters [Electronic resource] // Journal of Radio Electronics. - 2010. - No. 9. - Access mode: http://jre.cplire.ru] established that the shape parameter and the characteristic frequency at the logical level together determine the distribution of random signals in accordance with the data in table 1.

Table 1 is called the identification distribution scale (IS) and relates the shape parameter and characteristic frequency at the output of the measuring device with the names of random signals with two-mode (2MOD), arcsine (ARKS), uniform (RAVN), trapezoidal (TRAP), triangular (SIMP), normal (NORM), two-sided exponential (LAPL) and Cauchy (KOSHI) distribution laws. Averaging was carried out over the number of implementations L = 100, sample size N = 10000, signal observation time t _n = 1 s.

The fundamental nature of the identification scale (Table 1) is that it covers the full range of all possible forms of distributions.

The block diagram of the measuring device 7 includes a block for ranking the echo signal in ascending order 10, a block for calculating the sample size of the echo signal 11; the first and second blocks of calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal, respectively, K ₁ and K ₂ ; a block defining a scaling factor - “m”; the first and second blocks of multiplication "X ₁ " and "X ₂ "; division block "/".

The device operates as follows.

The signal generator of the package 5 sends a pulse signal through the power amplifier 6 and the receiver unit 1 (sonar antenna) to the marine environment. A copy of the signal sends to the block matched filters 4 to ensure maximum signal to noise ratio (SIR) at the output of the filter. The echo signal reflected from the location object enters the sonar antenna 1, passes through the block of amplifiers and band-pass filters 2 to reduce the level of interference, goes to the ADC block 3 and then to the block of matched filters 4.

The measuring device 7 measures the shape parameter A of the distribution and the characteristic frequency F of the echo signal at the output of the matched filter block 4. Calculator 8 calculates the ratio of the shape parameter and the characteristic frequency. The detector compares the received number at the output of the calculator with a threshold and gives a signal about the detection of the desired location object.

The operation of the measuring device is as follows.

The echo signal coming from the output of the matched filter block 4 to the measuring device 7 is fed in parallel to the input of the block for calculating the sample size of the echo signal 11, the input of the first block calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal K ₁ and the input of the block echo ranking in ascending order 10.

In block 11, the calculation of the sample size of the echo signal, presented in the form of the implementation of sample values, determines the sample size N, which is input to the multiplication unit "X ₂ ".

In the block “K ₁ ”, the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal, the value of which is input to the division block “/”, is calculated.

In block 10, the echo signal is ranked in increasing order and is input to the second block for calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal K ₂ , which is then multiplied by a scaling factor m in block “X ₁ ” and fed to another input multiplication unit "X ₂ " and in parallel - to the input of the division unit "/".

Block "m" sets the value of the scaling factor to match the value of the characteristic frequency F of the periodic signals with their natural frequency. The value of the scaling coefficient m = 2 was found experimentally.

The ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal in the blocks "K ₁ " and "K ₂ " is determined in a similar way. Consider the operation of these blocks on the example of the block "K ₁ ".

и средневыпрямленное значение приращения эхо-сигнала

по формулам:Let there be a discrete echo signal X at the input of block “K ₁ ” in the form of a series of observations {x ₁ , x ₂ , ..., x _N } of volume N. The average rectified value of the echo signal is determined

and mean rectified echo increment

according to the formulas:

Then, the parameter K is calculated:

The shape parameter A of the echo distribution is calculated by multiplying the observation volume N by mK ₂ in the block “X ₂ ”, and the characteristic frequency of the echo signal F is found by dividing K ₁ by mK ₂ in the block “/”.

The calculator 8 implements the operation of the ratio of the parameter of the form A distribution and the characteristic frequency F of the echo signal:

The detector 9 implements a comparison of the input data with a threshold value:

Where z = 0 - the object is not detected, z = 1 - the object is detected, y - input data, y ₀ - the detection threshold value is set at the preliminary calibration stage.

In FIG. 3 and FIG. Figure 4 shows examples of echo signals acting at the input of the measuring device of the sample size N = 30 for the case when the object was not detected (Fig. 3) and detected (Fig. 4), and also shows the corresponding values of the shape parameter A, characteristic frequency F and their A / F ratios.

раз [Новицкий П.В., Зограф И.А. Оценка погрешностей результатов измерений. - 2-е изд., перераб. и доп. - Л.: Энергоатомиздат, 1991. - Стр. 141], что, как следствие, приводит к увеличению достоверности обнаружения объекта в присутствии шумов и помех.The use of two parameters characterizing a single object gives a decrease in random error in

times [Novitsky P.V., Zograf I.A. Error estimation of measurement results. - 2nd ed., Revised. and add. - L .: Energoatomizdat, 1991. - Page 141], which, as a result, leads to an increase in the reliability of object detection in the presence of noise and interference.

Claims (2)

1. A device for detecting underwater objects, comprising a receiver-emitter unit, an amplifier and band-pass filter unit, an analog-to-digital converter unit, a matched filter unit connected to the measuring device, a sending signal generator, a power amplifier and a detector, characterized in that the measuring device is configured to measuring the shape of the distribution parameter and the characteristic frequency of the echo signal at the output of the matched filter and connected to the calculator of the relationship of the shape distribution parameter the frequency and characteristic frequency of the echo signal, while the output of the calculator is connected to the input of the detector. 2. The device according to p. 1, characterized in that the measuring device comprises a block for ranking the echo signal in increasing order, a block for calculating the sample size of the echo signal, the first and second blocks for calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal, a block specifying a scaling factor, the first and second multiplication blocks, and a division block, wherein the measuring device is configured to supply an echo signal in parallel to the input of the echo signal sample size calculation unit, the input of the first unit for calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal and the input of the block for ranking the echo signal in increasing order, the output of which is connected to the second unit for calculating the ratio of the average rectified value of the echo signal to the average rectified value of the increment of the echo signal, to the inputs the first block of multiplication connected to the output of the block that sets the scaling factor, and the output of the second block to calculate the ratio of the average rectified value of the echo signal to the average the rectified value of the increment of the echo signal, the output of the block for calculating the sample size of the echo signal and the output of the first block of multiplication are connected with the corresponding inputs of the second block of multiplication, at the output of which the value of the shape parameter of the distribution of the echo signal is generated, while the output of the first block of calculating the ratio of the average rectified echo value -signal to the average rectified value of the increment of the echo signal and the output of the first multiplication block are connected with the corresponding inputs of the division block, at the output of which the value the characteristic frequency of the echo signal.

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