RU2390801C1 - Method of searching for artificial objects in earth and device for implementing said method - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: probing radar signals are generated at the mechanical resonance frequency of the search object F, as well as seismoacoustic signals. Radar echo signals are received and the useful signal at frequency F is picked up. The group delay time of the seismoacoustic signal relative the received radar echo signal is measured. The distance from the search apparatus to the search object is determined. The phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal is measured. The correction value of distance from the search apparatus to the search object is calculated. The device for implementing the said method has a seismoacoustic signal source which acts on a base plate, a reference acoustic signal generator, radar with a transmitter and a receiver, a switched transceiving antenna, a microwave generator, a phase detector, a low-pass filter, a unit for measuring the distance from the search apparatus to the search object, a memory unit, a microcontroller and a computer. The unit for measuring distance from the search apparatus to the search object consists of a unit for measuring group delay time of the seismoacoustic signal relative the received radar echo signal and a unit for measuring phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal.

EFFECT: higher search sensitivity, increased efficiency of the search apparatus.

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Description

The invention relates to a search technique and can be used in geophysics, construction, archeology, the search for mine-explosive barriers.

A known method for determining the location of inhomogeneities in a rock mass (AS No. 1777111, G01V 3/12, publ. 11/23/92), in which radiation is received at two points located at a distance with the expected slight change in the parameters of the studied massif using transceiving antennas of electromagnetic pulses, first polarized in the plane of incidence, then orthogonally to the plane of incidence, by measuring the amplitudes and phases of the spectral components of the received reflected signals, complex dielectric oncity of the host rock and heterogeneity.

Устройство для реализации данного способа содержит на контролирующем объекте передатчик электромагнитных волн, генераторы высокой и низкой частоты, перемножитель, усилитель мощности и акустический излучатель, на контролируемом объекте приемник электромагнитных волн, фазометр, детектор, два фильтра, блок задания инвариантной скорости, два акустических приемника, два усилителя и измерители звукового давления и колебательной скорости.A known method of measuring distance and a device for its implementation (RF patent No. 2039368, G01S 15/18, published 09.07.95), which includes the generation and emission of a high frequency acoustic signal ω modulated by a low frequency Ω, radiation of an electromagnetic frequency signal synchronously with it ω used as a reference signal, measuring the phase incursion Δφ (Ω) at a low frequency during the passage of a controlled distance, measuring at a high pressure frequency P (ω), determining the density of the medium ρ, vibrational velocity in the direction The prevalence of V (ω) and the invariant velocity of sound propagation C _INV, calculating the phase velocity C _f (ω) at high frequency in step reception ratio C _f (ω) = P (ω) / ρ × V (ω), and the distance is determined in relation

A device for implementing this method comprises an electromagnetic wave transmitter, high and low frequency generators, a multiplier, a power amplifier and an acoustic emitter, an electromagnetic wave receiver, a phase meter, a detector, two filters, an invariant speed setting unit, two acoustic receivers, two amplifiers and sound pressure and vibrational velocity meters.

Also known is a method of measuring the distance when the transceiver is exposed to an acoustic signal and a device for its implementation (RF patent No. 2080616, G01S 11/00, publ. 27.05.97), which includes a comparison in the analysis unit of the transit time of the electromagnetic and acoustic signal from the acoustic source signal to the transceiver. The acoustic signal source is located at a determined distance R ₁ from the transceiver, the acoustic signal receiver is located at a distance R ₂ from the acoustic signal source, the degree of statistical dependence and the time difference of the signals arriving at the electromagnetic signal receiver and the acoustic signal receiver are measured, and the difference in the distances is determined from this difference R ₁ -R ₂ and the distance R _{2 is} chosen known. One embodiment of the device comprises a transceiver, an electromagnetic signal receiver, an analysis unit, an indication unit, an acoustic signal receiver, and another embodiment of the device comprises a transceiver, an electromagnetic signal receiver, an acoustic signal source, an analysis unit, an indication unit, an electric signal generator.

Closest to the claimed invention is a method of geophysical integrated exploration and a device for its implementation (RF patent No. 2022301, G01V 1/00, G01V 11/00, publ. 10/30/94), based on the excitation of sounding pulsed seismic-acoustic and radar signals. Received radar echoes are converted to the frequency of seismic acoustic echoes. Further, all echo signals are amplified, filtered, weighed and pre-processed using the same hardware and software. In this case, preliminary processing includes the calculation of the products of the echo signals from successive excitations and the summation of 5-30 works depending on the speed and objectives of the research. To increase the depth of exploration, a mismatch correction is introduced at the signal processing stage, taking into account the difference in seismic-acoustic signals and radio signals from the reference horizon. In addition, the time signal between two pulsed influences is set equal to 0.25-1 period.

This method is implemented by a device containing a radar with a transmitter and receiver connected to a stroboscope, and an analog path controlled by a processor, as well as a seismic acoustic sensor, a computer and a data storage and recording system, while the control output of the processor is connected to a controlled input of the analog path, and the information input - to the output of the analog path. At the same time, the device is additionally equipped with a tracking frequency converter and a carrier for the control and processing application package, while the tracking input of the tracking frequency converter is connected to a seismic-acoustic sensor, the output is connected to a controlled input of a stroboscope, and the controlled input is connected to a processor, the latter is connected to a computer, controlled input which is connected to the carrier of control and processing applications, and the output is to a data storage and recording system.

The disadvantages of this method are the low sensitivity, which does not allow to determine the location of small objects, low noise immunity and a high level of false alarms.

The basis of the invention is the task of improving the performance of the search installation, reducing the likelihood of false alarms and the probability of skipping search objects.

The problem is solved in that in the known method, based on the excitation of seismic-acoustic and sounding radar signals, according to the invention, seismic-acoustic signals are excited at the frequency of the mechanical resonance of the search object F, radar echo signals are received, a useful signal of frequency F is extracted from the received radar echo signals measure the group delay time of the seismic acoustic signal relative to the received radar echo signal t _gr , determine the the melting from the search setting to the search object by the ratio:

D = υ _sound × t _gr ,

where υ _sound - the propagation speed of the seismic acoustic signal in the ground,

measure the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal Δφ _ak (Ω), calculate the correction value of the distance from the search facility to the search object by the ratio:

ΔD = Δφ _ak (Ω) × λ _ak / 2 × π,

where λ _ak is the wavelength of the reference acoustic signal.

The problem is also solved by the fact that in the known device containing a radar with a transmitter and a receiver, a switched transceiver antenna, as well as a series-connected storage device, a microcontroller and a computer, a microwave generator is additionally introduced, the first output of which is connected to the transmitter input, and the second output to the second input of the phase detector, the output of which is connected to the input of the low-pass filter, while the receiver, the unit for measuring the distance from the search, is connected to the first input of the phase detector installation to the search object, consisting of a unit for measuring the time of the group delay of the seismic acoustic signal relative to the received radar echo signal, the output of which is connected to the second input of the storage device, and a unit for measuring the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal, the output of which is connected with the first input of the storage device, while the input of the unit for measuring the distance from the search installation to the search object is connected to the output fi liter of low frequencies, as well as a reference acoustic signal generator, the first output of which is connected to a source of seismic acoustic signal acting on the base plate, and the second output - with the second input of the phase difference block of the first harmonics of the received radar echo signal and the acoustic reference signal.

If the intensity of the seismic-acoustic wave at the surface of the search object is equal to I, and its cross-sectional area is S, then the amplitude of the sound pressure force on the surface of the search object is:

P = I × S.

Since the equation of the dynamics of the surface of an object without taking into account the influence of the medium can be written as:

then the acceleration of the displacement of the surface of the object will be equal to:

where m is the mass of the search object.

The mechanical resonance of the body of the search object increases the action of the force P by a factor equal to the quality factor Q, therefore, expression (2) can be written as:

Since the intensity of the seismic-acoustic wave I at the interface damps inversely with the distance D, it is possible to approximately estimate the value of the effective force at the surface of the object using the expression:

- интенсивность сейсмоакустической волны вблизи источника;Where

- the intensity of the seismic acoustic wave near the source;

R _and is the effective radius of the contact surface of the emitter of seismic-acoustic waves (signals) with soil;

P ₁ - power emitter of seismic waves (signals) ;.

S is the surface area of the body of the object of the search, perpendicular to the acting force;

D is the distance to the search object.

From the solution of equation (1), the displacement of the object’s body under the action of acoustic pressure is:

where τ is the duration of the acoustic pressure force.

With a single impact in the interval 0 ÷ τ, the value P = const, from expressions (3) and (4) we obtain:

With a periodic repetition of seismic acoustic pulses with a period T, the radar signal reflected from the object can be written as:

where ω _i = 2πf _i is the cyclic frequency of the radar signal,

λ _i is the wavelength of the radar microwave signal,

Ω = 2πF is the cyclic frequency of the seismic acoustic signal,

i is the current harmonic number.

For a periodic pulse signal, when 90% of its energy is concentrated in the first harmonic, the phase shift of the first harmonic of the received radar echo signal will be equal to:

By phase detection of the radar signal reflected from the object, highlighting the phase modulation coefficient Δφ, it is possible to obtain information about the displacement r, which is directly proportional to the ratio according to expression (5):

For objects of the same size, the magnitude of this shift is greater, the higher the quality factor of its body and the smaller the mass. For objects of artificial origin such as mines, the Q / m parameter will clearly differ from natural objects (for example, stones) or artificial (for example, scrap metal, etc.).

The proposed method is as follows.

The search zone is simultaneously irradiated with sounding microwave radar signals of frequency f and seismic acoustic signals of frequency F. By changing the oscillation frequency F of the reference acoustic signal generator, the resonant frequency is selected for each individual search object. In this case, the condition c >> υ _cv is fulfilled, where c is the propagation speed of the radar signal, υ _cv is the propagation speed of the seismic-acoustic signal in the ground, therefore, the seismic-acoustic signal relative to the radar signal reaches the search zone with a time delay.

If the radar signal is reflected from a non-vibrating surface, then its frequency is f; and if the radio signal is reflected from the vibrating surface, then its frequency is equal to:

f1 = f ± F,

those. when reflected from a vibrating surface, the received radar echo signal is modulated by frequency F.

A radar echo signal is received, then a useful signal of frequency F is extracted from the received radar echo signals by phase demodulation. The time of the group delay of the seismic acoustic signal relative to the received radar echo signal and the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal are measured.

The distance from the search installation to the search object is determined by the expression:

D = υ _sound × t _gr ,

where υ _sound - the propagation speed of the seismic acoustic signal in the ground;

t _gr - group delay time of the seismic acoustic signal relative to the received radar echo signal,

and the correction value of the distance from the search installation to the search object is calculated by the ratio:

ΔD = Δφ _ak (Ω) × λ _ak / 2 × π,

where λ _ak is the wavelength of the reference acoustic signal;

Δφ _ak (Ω) is the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal.

The invention is illustrated by drawings, where figure 1 presents a block diagram of a device that implements a method of searching for objects of artificial origin in the ground; figure 2 shows the timing diagrams of signals.

On the block diagram of the device (figure 1) are indicated: r is the displacement of the body of the object under the influence of acoustic pressure; d is the thickness of the search object.

The device contains a radar with transmitter 1 and receiver 2 connected to a switched transceiver antenna 3, a microwave generator 4, the first output of which is connected to the transmitter 1, and the second output to the second input of the phase detector 5. The output of the receiver 2 is connected to the first input of the phase detector 5 The output of the phase detector 5 is connected to the input of the low-pass filter 6, the output of which is connected to the input of the unit for measuring the distance from the search facility to the search object 7. The state unit for measuring the distance from the search facility to the search object 7 is t from the unit for measuring the time of the group delay of the seismic acoustic signal relative to the received radar echo signal 9 and the unit for measuring the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal 8, the second input of which is connected to the second output of the reference acoustic signal generator 13. The output of the measurement unit time group delay of the seismic acoustic signal relative to the received radar echo signal 9 is connected to the second input its device 10, and the output of the unit for measuring the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal 8 to the first input of the storage device 10. The storage device 10, the microcontroller 11 and the computer 12 are connected in series. The first output of the reference acoustic signal generator 13 is connected to the input of the source of the seismic-acoustic signal 14, which acts on the base plate 15. The search object is indicated by the number 16.

The device operates as follows.

The radar sounding signals U _radar frequency f ( _figure 2), generated by the microwave generator 4, are fed to the transmitter 1 and using a switched transceiver antenna 3 are emitted in the search direction. Simultaneously radiated through the support plate 15 and extends along the ground seismo-acoustic signal U _au frequency F (2) generated by the reference acoustic signal generator 13, connected to the seismo-acoustic signal source 14. The received radar echo receiver 2 signals U _Neg fed to a first input a phase detector (PD) 5, the second input of which is connected to the second output of the microwave generator 4. From the output of the PD 5, the radio signal is fed to the input of a low-pass filter (LPF) 6. After the LPF 6, the received radio signal is received sends to the input of the unit for measuring the distance from the search facility to the search object 7, consisting of a unit for measuring the time of the group delay of the seismic acoustic signal relative to the received radar echo signal 9 and the unit for measuring the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal 8, the second input which is connected to the second output of the acoustic signal generator 13.

Since the propagation velocity of the radar signal c is many times higher than the propagation velocity of the seismic-acoustic signal υ _sv , i.e. c >> υ _sound , then the time interval between the moment of the onset of radiation and the moment the signal U from _{p arrives} at the input of block 8 can be considered the group delay time t _gr (Fig. 2).

The obtained values of the group delay time of the seismic acoustic signal relative to the received radar echo signal and the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal are recorded in the storage device (memory) 10. The memory device 10 also stores the speed of the seismic acoustic signal in various environments . The information stored in the memory 10 is fed to the input of the microcontroller 11, where the information on the soil vibration parameters is processed, a decision is made on the presence or absence of the search object 16 in the search area and the coordinates of the search object 16 are calculated. Next, the received information is sent to the computer information port 12, where using specialized software on the monitor screen provides an indication of the location of the search object in a convenient form for the search engine operator.

Practically working with the equipment is as follows. In the process, the device is moved with stops with a certain step equal to the area of the radar irradiation (for example, 10 ÷ 20 m). When you stop the base plate 15 with the source of the seismic acoustic signal 14 with a certain force is pressed into the ground, turn on the power of the reference acoustic signal generator 13.

By varying the parameters P ₁ , τ, f, and F, optimal information characteristics Δφ, m, and r are obtained for identifying search objects.

To determine the presence or absence of a search object in the irradiation zone, the obtained informational characteristics are used to train an onboard neurocomputer, consisting of a memory, a microcontroller, and a computer, using specialized software [F. Wossermen. Neurocomputer technology: Theory and practice. / Per. from English - M .: Mir, 1992, 240 pp.].

If there is a search object 16 in the irradiation zone, for example, a separate mine or minefield, the fact of detecting the object is indicated on the indicator (i.e., on the monitor screen). If the search object is not detected, then the search engine carrier moves to a distance R equal to the radar irradiation area, after which the inspection cycle of the next search zone is repeated.

We give a numerical estimate of the phase shift of the carrier of the reflected radar signal Δφ and the displacement of the object’s body r, using relations (7) and (5), respectively.

Прочие параметры: f=1 ГГц; λ=0,3 м; D=10 м; R_и=0,1 м; S=0,002 м²; m=0,3 кг; Q=1; τ=0,001 с. Взятая за основу расчета масса объекта m, равная 0,3 кг, соответствует массе противопехотной мины. Подстановка этих значений в выражения (5) и (7) соответственно дает r=20 м и Δφ≈2,4°. На рабочей частоте радиолокатора f=10 ГГц, величина сдвига фаз составляет Δφ=24°.Let the impact energy be 10 kgm, which corresponds to its equivalent force:

Other parameters: f = 1 GHz; λ = 0.3 m; D = 10 m; R _and = 0.1 m; S = 0.002 m ² ; m = 0.3 kg; Q = 1; τ = 0.001 s. Taken as the basis of the calculation, the mass of the object m, equal to 0.3 kg, corresponds to the mass of an anti-personnel mine. Substitution of these values in expressions (5) and (7), respectively, gives r = 20 m and Δφ≈2.4 °. At the radar operating frequency f = 10 GHz, the phase shift is Δφ = 24 °.

The calculated values of r and Δφ indicate the feasibility of practical implementation of the proposed search method, while the phase measurement technique today allows us to register a phase shift of at least 0.1 °. In seismic exploration today, non-explosive sources of both continuous and pulsed acoustic waves with a single impact force of up to 100,000 kg or more are widely used [Schneerson MB et al. Theory and practice of ground-based non-explosive seismic exploration. - M .: Nedra, 1998], thus, the creation of relatively low-powered oversized non-explosive sources for impact force of 1000-10000 kg is real.

Thus, the proposed method for searching for objects of artificial origin (for example, mines) in the ground, unlike the prototype, provides the ability to remotely determine the presence or absence of a search object in the irradiation zone, indicating the location coordinates of the search object with high accuracy.

Claims (2)

1. A method of searching for objects of artificial origin in the earth, based on the excitation of seismic-acoustic and sounding radar signals, characterized in that the seismic-acoustic signals are excited at the frequency of the mechanical resonance of the search object F, radar echo signals are received, a useful signal is extracted from the received radar echo signals frequency F, measure the group delay time of the seismic acoustic signal relative to the received radar echo signal t _gr , determine the distance from the search engine to the search object by the ratio:
D = υ _sound · t _gr ,
where υ _cv is the propagation speed of the seismic-acoustic signal in the ground, the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal Δφ _ak (Ω) is measured, and the distance correction value from the search facility to the search object is calculated by the ratio:
ΔD = Δφ _ak (Ω) · λ _ak / 2 · π,
where λ _ak is the wavelength of the reference acoustic signal. 2. A device for searching for objects of artificial origin in the earth, containing a radar with a transmitter and a receiver, a switched transceiver antenna, as well as serially connected storage device, a microcontroller and a computer, characterized in that it is additionally equipped with a microwave generator, the first output of which is connected to the input of the transmitter, and the second output - to the second input of the phase detector, the output of which is connected to the input of the low-pass filter, while the receiver is connected to the first input of the phase detector, measuring the distance from the search installation to the search object, consisting of a unit for measuring the time of the group delay of the seismic acoustic signal relative to the received radar echo signal, the output of which is connected to the second input of the storage device, and a unit for measuring the phase difference of the first harmonics of the received radar echo signal and the reference acoustic signal the output of which is connected to the first input of the storage device, while the input of the unit for measuring the distance from the search installation to the objects This search is connected to the output of the low-pass filter, as well as to the generator of the reference acoustic signal, the first output of which is connected to the source of the seismic-acoustic signal acting on the base plate, and the second output is connected to the second input of the phase difference block of the first harmonics of the received radar echo signal and the reference acoustic signal.

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