Adaptive seismic correlation object direction finder

FIELD: protection aids.

SUBSTANCE: direction finder can be used for taking azimuth relatively guarded objects at guarded areas, calculating number of objects in group target and classifying found objects. Direction finder has two seismic receivers, two processing channels with delay lines and correlators, maximal signal selector, correlator, testing module, commutator and calculator. To realize the direction finding function the method of passive diversity detection and ranging is used. The main information criterion for finding direction to object has to be the function of mutual signals correlation in two signal processing channels. Value of azimuth is judged from value of signal delay. Change in value of signal delay is equivalent to controlling directional diagram of seismic active aerial which allows classifying detected objects separately. Test influence is used for adaptation of speed of propagation of seismic wave which changes under influence of meteorological conditions. Current value of speed of propagation of seismic wave is judged from time of delay of test influence signal coming to second seismic receiver. Tuning of lines of delay is conducted correspondingly to those changes.

EFFECT: improved precision of direction finding.

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The invention relates to means of protection and can be used to determine the azimuth of a detected object and its classification under the protection of extensive areas, areas and approaches to objects.

Known methods posted passive acoustic location to determine the azimuth of the detected objects implemented in the correlator [1], where the main information characteristic to determine the direction to the object is a function of the cross-correlation between two signals, as well as devices for the classification of the detected objects, which are implemented in recognition device of seismic signals [2] and seismic device detection and classification of objects [3].

Closest to the present invention is a seismic correlation signal of interest (Figure 1) [4]. In each of its channels is implemented mutual correlation processing for a fixed delay value of the signal, then the classifier 10 the decision is made to set the selected signal to the corresponding object class.

Structural diagram of seismic correlation of the signal of interest includes a delay line channel of the first signal y₁(t), a delay line with taps of the channel of the second signal y₂(t), the correlators X1, x2,...Xn, becausealmost, the maximum selector signal and the classifier. Two channels of received signals y₁(t) and y₂(1)formed of identical, spaced, sensitive elements. The nature of the signals is determined by the class of the detected object. The first signal is conditionally adopted by reference and is supplied to the first inputs of all the correlators. The second signal with a different delay time is supplied to the second inputs of all the correlators. The outputs of the correlators is formed mutual correlation function of two signals. The maximum value of the mutual correlation function is formed at the output of the correlator, to which input signal, delayed by the delay time of the entry of the wave front in one seismogenic relative to another geophone, i.e. the condition of compensation of the difference of progress of the wave. The delay time of the signal is dependent on the direction to the object and, therefore, allows us to estimate the azimuth to the object. When the selection of the useful signal simultaneously on multiple channels, the maximum selector signal 9 sequentially connects the outputs of the correlators to the classifier 8, allowing to classify the detected objects.

The disadvantage of this device is to reduce the accuracy of direction finding objects when changing the propagation velocity of seismic the waves in the soil under the influence of meteorological factors (humidity, temperature, atmospheric pressure).

The proposed device provides an increase in the information content of the seismic detection, and spatial selection signals against the background noise. For this seismic correlation signal changes, the signal processing unit: the testing module, the switch control unit and the transmitter (Figure 2).

The speed of propagation of waves depending on the type of soil is 400...1000 m/s, however, the change in soil moisture, temperature, or atmospheric pressure, it can increase or decrease by 2-5 times [6].

Seismic waves are two spaced some distance L geophone amplifiers, where L is the seismic base receiving seismography. The seismic receivers and amplifiers are identical.

The distance traversed by the waves from sources seismography to geophones, are not the same, and, therefore, differ in the phase of the received signal. Delay one of the signals depends on the position of the source of the waves relative to the geophone, the distance L (seismic base) and the propagation velocity of seismic waves U.

Because the signal in both channels is the same, and microseisms and some types of interference (noise of rain, the rustle of grass,...) independent channels, ineach channel will be variations of the form y ₁(t) and y₂(t):

where y₁(t) and y₂(t) is the input vibrations in the first and second channel, which is an additive mixture signal S(t) and noise n₁(t) and n₂(t) in each channel.

In the correlators signals are multiplied together, and the mutually interfering signals are suppressed.

The implementation of the cross-correlation function of signals from one source to two independent channels takes the maximum value in the case of a compensation delay time of the signal on one channel due to the inclusion of the delay line. The number of correlators, is equal to n, is determined by the ease of application of n delay lines with a fixed delay time. The number of correlators is determined by the required accuracy of the azimuth to the object.

In General, you must ensure that the total delay of the signal in the range from -Δt to Δt using n delay lines. The time interval Δt is determined by:

where L is the seismic base;

U is the velocity of propagation of seismic waves.

Since the propagation velocity of seismic waves depends not only on the soil type, but also on humidity, temperature, it is necessary to adjust the delay line to ensure compliance with conditions (3). In the presence of the test module just orientirovanno what about the terrain relative to the geophone (optimally axis) it is possible to calculate the actual velocity of propagation of seismic waves in (4) and rebuild accordingly, delay line:

where t_mecmthe time delay of the signal between the geophones.

The presence simultaneously at the outputs of several correlators of local maxima of the cross correlation function corresponds to the situation when at the turn of the present multiple objects. On this basis the estimated number of objects in the monitored area.

The pattern correlation of the signal with two geophones is an “eight” [5]. The beam width depends on the value of L (seismic base), the working wavelength of the correlator, the average frequency spectrum of the seismic signal and the width of the spectrum of the seismic signal. These parameters are selected based on the requirements of the direction finder.

The mutual correlation function of the signal from the object detection, the received two identical channels, and formed by the correlator (Figure 2), represents nothing more than the autocorrelation function, but with different signal delay times.

The outputs of all multiplier products of the signals of the correlators will be signals obtained by multiplying the input signals. The signal raised to the second degree, will be observed at the output of the multiplier, a second input to the th signal, detained on the lag time of arrival of seismology. Therefore, the signal at the output of the multiplier will contain full information about the class processed object, which allows further classification on any grounds (band frequency, the behavior of the function signal, and so on).

The device is implemented as follows (Figure 2). In the initial state is receiving seismic signals from two spaced Samobranka. The seismic signals through the switch 2 is fed to two channels for processing. The first channel includes a pre-processing cascades and one delay line 5, conditionally accepted reference. The second channel includes a set of delay lines 6 and as many correlators, consisting of the multiplier 8 and the integrator 9 each. The signals at the outputs of all correlators are compared decisive device 12. If the signals generated at the outputs of all correlators are the same or slightly different, the decision about the azimuth to the object will not be accepted and the maximum of the signal selector 13 and the classifier 14 not participate. This corresponds to the situation when in the detection zone the object is missing or is present dispersed in the space of a hindrance.

If an object appears in the detection zone on the outputs of the correlators signals are not the same the. Crucial device 12 according to the criterion of maximum mutual correlation function on the outputs of the correlators, the decision about the azimuth of a detected object. Crucial device 12 determines the correlator with a maximum output signal and generates a command for the maximum of the signal selector 13 how to connect the output of the multiplier 8 of this correlator to the classifier 14. The classifier 14 decides the expected class of the detected object. The switching outputs of the correlators selector maximum signal means 13 control chart the direction of the direction finder. In the case of multiple objects on the protected boundary of the observed maxima at the outputs of multiple correlators. Alternately switching the selector maximum signal 13 of the outputs of the correlators to the classifier 12 allows to classify the detected objects. Count the number of objects on the protected boundary in that case, if the objects are from each other at a distance that allows them to record separately, i.e. in the case of a narrow beam in which the system seismic has a resolution in azimuth.

If you install the tool, as well as changing humidity, pressure, soil or in accordance with the program, the control unit 3 generates a command test is testing, arriving at the testing module 1 and switch 2. The switch 2 at the command of the test control unit 3 switches the input channels from the cable to the transmitter 4, and the testing module excites the seismic wave received Samobranka. The calculator calculates the delay time of the signal between Samobranka and rebuilds delay lines 5 and 6 in accordance with the changing time delay (propagation velocity of seismic waves). After adjustment of the delay lines, the switch switches on them input channels and the device working again in normal mode.

The proposed adaptive seismic correlation signal of interest improves the accuracy of azimuth determination on objects when they change under the influence of meteorological factors physico-mechanical properties of soil.

Sources of information

1. Electronic systems: basic construction and theory. Guide/ Shirman AD Losev SCI, Minerven N.N., and others/ edited Aderman - M.: ZAO "MAQUIS", 1998. - 828 with: ill., Jbeil. 539 name.

2. SU 1832954, 7 G 01 V 1/28, Sharmanov E., Sokolov, I. V., Matveev V.S., Lisitsyn SV recognition Device of seismic signals.

3. EN 2040807, 6 G 08 B 13/00, Horev Peter F., Mashchenko Vladimir Alekseevich, Sirotkin Konstantin N., Shields, Vladimir Petrovich, Denis Lebedev Mikhailovich. Seism the ical device detection and classification of objects.

4. EN 2204849, 6 G 08 13/00, hooks, I.N., Ivanov V.A., Dogowner A.P. Seismic correlation direction finder objects.

5. Binstock V.B. have been the Measurement of the angular coordinates and passive radar. - M.:USAIS, 1967. - 104 S.

6. Gurvich, I.I., Bohanec GN. Seismic exploration: a Textbook for high schools. - 3rd ed., Rev. - M.: Nedra, 1980. - 551 S.

Adaptive seismic correlation signal of interest, which is the reception of seismic signals from two spaced by the geophones, the seismic signal is fed to two channels for processing the first channel processing of seismic signals, comprising a delay line, the second channel processing of seismic signals, comprising a set of delay lines with different delay time and the correlators on the number of delay lines, the first input of each correlator receives the signal from the output of the delay line of the first channel processing seismic signal, the second input of each correlator receives the signal from the output of the delay line with a certain time delay, the outputs of correlators connected to inputs of a casting device, a selector the maximum signal and the classifier, the input selector signals are connected to the outputs of multiplier products correlator, the output of the maximum selector signal connected to the input of the classifier, the output of a casting in which trojstva connected with the control input of the selector maximum signal, characterized in that it further introduced the testing module, the control unit, the switch and the transmitter, the input switch is connected to the geophones, the first group of outputs of the switch is connected to the delay lines of the first and second channel processing of seismic signals, the second group of outputs of the switch are connected to the inputs of the transmitter, the control input of the switch is connected to the first output control unit, the second output control unit connected to the input of the testing module, the third output control unit connected with the control input of the transmitter, the output of which is connected with corrective inputs of the delay lines of the first and second channels of processing seismic signals.