RU2234112C1 - Geophysical radar - Google Patents

Abstract

FIELD: geophysics, in particular, devices of geoelectric prospecting with the use of high-frequency electromagnetic waves, applicable in prospecting of mineral resources, for tracing of engineering service lines and other concealed discontinuities in the subsurface layer of the ground surface, as well as for detection of alive people under ground, snow, etc.

SUBSTANCE: the geophysical radar has a processing and control unit, interface, transmitter, transmitting antenna, two mixers of a stroboscopic converter, two strobe conditioners, receiving antenna, two delay lines, flip-flop, gate, digital-to-analog converter, amplifier, analog-to-digital converter, aural indicator, liquid-crystalline indicator, subtraction unit, integrator, division unit, standard voltage generating unit, comparison unit, quadrature demodulator, preamplifiers, multiplexers, multichannel band-pass filters, demultiplexers, electronic short-circuiting keys, low-pass filters.

EFFECT: expanded functional potentialities.

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Description

The proposed radar relates to geophysics, in particular to devices for geoelectrical exploration using electromagnetic waves of high frequency, and can be used in mineral exploration, to search for engineering communications and other hidden heterogeneities in the investigated subsurface layer of the earth’s surface, as well as to detect living people underground , in the rubble, under the snow, etc.

Known devices for geoelectrical exploration (ed. Certificate of the USSR No. 321783, 344391, 385251, 397877, 455307, 708277, 746370, 817640, 1078385, 1092453, 1100603, 1151900, 1247805, 1300396, 1317378, 1420574, 1469488, 1469488, 1469488 1721566; RF patents No. 2044331, 2105330, 2194292; A. Petrovsky, Radio wave methods in underground geophysics. - M., 1971 and others).

Of the known devices, the closest to the proposed one is "Geophysical radar" (RF patent No. 2194292, G 01 F 3/12, 2000), which is selected as a prototype.

The principle of operation of this geophysical radar is based on the method of ultra-wideband radar sensing, in which the change in the unsteady electromagnetic field formed by electromagnetic waves reflected from a subsurface object after its irradiation with a probing radio signal is estimated, which is used as a sequence of radio pulses with a small number of periods of high-frequency oscillations in each of them ( down to one). In this case, the separation of the transceiver channels over the air is carried out using two antennas (transmitting and receiving), which form a two-antenna unit. The formation of a probe ultra-wideband radio signal is carried out by a shock excitation generator and a transmitting antenna.

At the soil - object interface, characterized by a jump in relative permittivity and specific attenuation, a reflected signal is formed that returns to the receiving antenna. The received ultra-wideband signal with the aid of a stroboscopic receiver undergoes a time-scale conversion and is digitized, convenient for presentation and processing. This signal contains information about the depth of the object, and about its shape, material, etc. Useful information is extracted using processing in a special calculator and displayed on the screen of a visual indicator in real time.

An electromagnetic wave reflecting from a subsurface object acts on the receiving antenna; the same antenna is affected by interfering direct radiation from the transmitter and the reflected signal from the air-ground interface.

To eliminate direct radiation from the transmitter and reflected from the surface of the air - soil and from layers with different depths in the known radar, "vertical gating" is used.

“Horizontal gating” allows against the background of electromagnetic field variations not related to the electromagnetic wave reflected from the subsurface object to reliably distinguish subsurface objects in the subsurface layers. To exclude the influence of periodic and quasi-stationary variations of the Earth’s electromagnetic field, a periodic measurement of the field strength and the normalization of the difference signal of two successive measurements are carried out, i.e. ignore the difference signal, divide the difference signal by the integrated difference signal. The operation of comparing a normalized signal with a delayed threshold value makes it possible to decide on the presence or absence of a subsurface object.

An object of the invention is to expand the functionality of the geophysical radar by searching for bombarded bioobjects or their remains in earthquake areas during search and rescue operations, as well as in mountaineering when searching for bioobjects bombarded with, for example, avalanches or mountain landslides.

The problem is solved in that a geophysical locator containing a processing and control unit, an interface, a transmitter, which uses a shock excitation generator and a transmitting antenna is connected to the second output, the first stroboscopic conversion mixer, the second input of which is connected through the first gate former with a second interface output, and a trigger, a receiving antenna connected in series, a second mixer of a stroboscopic converter, a second the input of which through the second gate driver is connected to the third output of the interface, the first delay line, a trigger, a key, the second input of which is connected to the output of the second mixer and an amplifier, the second input of which is connected through the digital-analog converter to the fourth output of the interface, to the fifth, sixth and seventh outputs which is connected to the processing and control unit, sound and liquid crystal indicators, respectively, and an analog-to-digital converter, a second delay line, and a subtracting unit are connected to the second input the second input of which is connected to the output of the amplifier, an integrator, a division unit, the second input of which is connected to the output of the subtraction unit, and a comparison unit, the second input of which is connected to the eighth output of the interface through the unit for generating the reference voltage, and the output is connected to an analog-to-digital converter equipped with a switch, a quadrature demodulator and two processing channels, each of which consists of a series-connected pre-amplifier, a multiplexer, the second input of which is connected to the output of W an alternating strobe driver, a multi-channel bandpass filter, a demultiplexer, an electronic short-circuit key, the second input of which is connected to the tenth output of the interface, and a low-frequency amplifier, the output of which is connected to an analog-to-digital converter, with a switch and a quadrature demodulator connected to the first output of the transmitter, the second input which is connected to the output of the comparison unit, and two outputs are connected to the first and second processing channels, respectively.

The geophysical radar comprises a processing and control unit 1, an interface 2, a transmitter 3, a transmitting antenna 4, a first gate converting mixer 5, a first strobe driver 6, a receiving antenna 7, a receiver 8, a second strobe driver 9, a second strobe transmitter 10, a first line 11 delays, trigger 12, key 13, digital-to-analog converter 14, amplifier 15, analog-to-digital converter 16, sound indicator 17, liquid crystal indicator 18, second delay line 19, subtraction unit 20, integ OP 21, division unit 22, reference voltage generating unit 23, comparison unit 24, switch 25, quadrature demodulator 26, pre-amplifiers 27.1 and 27.2, multiplexers 28.1 and 28.2, demodulators 30.1 and 30.2, electronic short-circuit keys 31.1 and 31.2, low-pass filters 32.1 and 32.2.

Geophysical radar operates as follows.

The main mode of radar operation is the “Search” mode. This mode is set automatically when the device is turned on and is used when searching and recognizing subsurface objects.

When applying power to the radar, the processing and control unit 1 initiates the installation of the initial modes of all nodes of the radar. At the command of the processing and control unit 1, the shock excitation generator 3 generates a pulsed ultra-wideband signal in the form of a single period of a sinusoid with an amplitude of 25 V and a duration of 1 ns, emitted by the transmitting antenna 4 in the direction of the Earth's surface.

Detection of objects in the “Search” mode is carried out by the operator by moving the antenna unit mounted on the bar in front of him right and left, and moving forward in a given direction. In this case, it is necessary to ensure that the antenna unit moves parallel to the surface being examined at a fixed distance (at least 5 cm from it). The speed of movement of the antenna unit is selected depending on the search conditions and should be within 0.1 ... 1.0 m / s. In the search process, it is necessary to alternate the transverse and longitudinal displacements of the antenna unit so that after each swing from right to left or left to right, the antenna unit moves forward up to 20 cm (by the size of its linear size). In this case, it is necessary to ensure that the entire checked area is examined.

An electromagnetic wave reflected from a subsurface object acts on the receiving antenna 7. The same antenna is affected by interfering direct radiation from the transmitter 3 and the reflected signal from the air-ground interface.

Part of the energy of the probe signal from the reference output of the transmitter 3 is supplied to the first mixer 5 of the stroboscopic converter, where a short strobe pulse is also supplied from the shaper 6 of the strobe. The pulse generated in the mixer 5, which is the instantaneous value of the probing periodic signal, is fed to the installation input of the trigger 12. The trigger 12 is transferred to the first (zero) state, in which a negative voltage is generated at its output.

The reflected signal containing information about the interface between the media and the subsurface object is fed from the output of the receiving antenna 7 to the second mixer 10 of the stroboscopic converter, where a short strobe pulse from the gate former 9 is also supplied. The pulse generated in the mixer 10, which is the instantaneous value of the received periodic signal, is transmitted through the delay line 11 to the second input of the trigger 12. The latter is transferred to the second (single) state, at which a positive voltage is generated at its output. This voltage is supplied to the control input of the key 13 and opens it. In the initial state, the key 13 is always closed.

The delay line 11 is necessary for the most complete control of the effect of reflections from the media interface on the operation of the amplifier 15 and subsequent stages. The delay line 11 can be made variable, which will eliminate the influence of direct radiation of the transmitting antenna 4 and signals reflected from the air-ground interface from layers of different depths, i.e. “vertical gating” is carried out, which provides sequential viewing of subsurface space to layers of different depths.

“Horizontal gating” allows against the background of electromagnetic field variations not related to the electromagnetic wave reflected from the subsurface object to reliably distinguish subsurface objects in the subsurface layers. To exclude the influence of periodic and quasi-stationary variations of the Earth’s electromagnetic field, periodic measurements of the field strength and the operation of normalizing the difference signal of two successive measurements are carried out, i.e. integrate the difference signal, divide the difference signal into the integrated difference signal. The operation of comparing a normalized signal with a delayed threshold value makes it possible to decide on the presence or absence of a subsurface object.

To do this, the pulse generated in the mixer 10, which represents the instantaneous value of the received periodic signal reflected from the subsurface object, or the pulse due to variations in the electromagnetic field, through the public key 13 is supplied after amplification in the amplifier 15 to the subtraction unit 20 directly and through the delay line 19. Moreover, at each observation point, at least two consecutive measurements of these pulses are made. Then, the operation of subtracting two consecutive measurements is performed. For this, the pulse corresponding to the previous measurement is delayed by the delay line 19 until it is compared with the subsequent pulse in the subtraction unit 20. The operation of integrating the difference signal and dividing the difference signal by the integrated difference signal is performed in blocks 21 and 22. In block 24, the normalized signal is compared with the threshold value of the signal set by block 23. If the threshold level is exceeded, the signal is input to the analog-to-digital converter 16, where it is converted to digital form and enters through the interface 2 in block 1 processing and control. The digital-to-analog converter 14 is designed to convert digital information coming from the processing and control unit 1 into analog information.

The frequency of formation of the strobe pulses differs from the stable frequency (100 kHz) of the generator, as a result of which the next strobe pulse is shifted relative to the periodic received signal, and the instantaneous values thus formed are added up to the time-scale implementation of the received signal.

After analog-to-digital conversion, the data through the interface board 2 goes to the processing and control unit 1, and then to the screen of the liquid crystal indicator 18. The frequency of vertical (horizontal) and horizontal (frame) scans can vary within certain limits. On the screen of the indicator 18 in real time there is a flat luminance picture of subsurface targets.

The maximum amplitude of the received signal is compared with the set threshold value, above which the sound indicator 17 turns on.

The appearance of an audio signal, a visual signal on the screen requires the operator to stop and indicates that an object is located in the detection area of the antenna unit, the origin of which should be established, and if necessary, its location and shape should be clarified. To analyze the object, you should scan the object (moving the antenna unit from the detection boundary to the loss boundary) at a speed that defines the light bar on the indicator screen.

The “Scan” mode and the formation of a vertical cut of soil with an object (“Slice” mode) is carried out by switching from the “Search” mode by pressing the “Scan” button. 20 seconds after the signal is processed, a radar image of the object appears on the indicator screen, giving an idea of the shape and size of the object. At the request of the operator, the contrast of the image can be changed using the "<", ">" buttons in the direction of decreasing or increasing.

To identify the detected object with the available standards, the operator needs to turn to the trained algorithm, and the corresponding name (for example, “object 2”) is displayed on the indicator screen when identifying the detected object with the standard in memory. In case of discrepancy, the message “object not recognized” is displayed.

To determine the material of the detected object, the operator switches to the basic algorithm by pressing a button. By pressing the “Scan” button, the basic algorithm is launched. A message about the type of material is displayed on the screen: “Metal”, “Composite”, “Plastic”, “Bioobject”.

Pressing the “Scan” button and moving the antenna unit above the object makes it possible to re-examine the object, if necessary, according to the criteria of the basic and trained algorithm.

Identification of the detected object by the trained algorithm, recognition of the type of material by the basic algorithm, analysis by the operator of the image and “slice” of the object allow the operator to decide on further actions regarding the detected object and continue exploration.

If the detected subsurface object in shape and material corresponds to the bioobject, then the operator closes the switch 25 and proceeds to determine the life functions of the detected bioobject, due to which living organisms can be reliably distinguished from the dead.

It is known that living organisms and, consequently, living human bodies unexpectedly affect high-frequency electromagnetic signals due to their main vital functions, that is, heartbeat and respiratory activity.

Since these vital functions usually manifest themselves within the known frequency ranges, which for the human heart rate are 0.5 ... 3.4 Hz, normally 1 ... 2 Hz, and for the respiratory rate 0.1 ... 1, 5 Hz, this defines the characteristic frequency ranges.

In any case, the frequency range from 0.01 to 10 Hz includes all frequencies of interest from the point of view of the vital functions of the body.

In this case, the reflected signal from the output of the comparison unit 24 is fed to the information input of the quadrature demodulator 26. As a heterodyne signal to this demodulator, part of the transmitter power 3 is supplied through the switch 25. The difference-frequency quadrature signals acting on the two outputs of the quadrature demodulator 26 are amplified by preamplifiers 27.1, 27.2 and enter the inputs of multi-channel bandpass filters 29.1, 29.2 through the multiplexers 28.1, 28.2. The control input of the multiplexers 28.1, 28.2 is connected to the output of the gate former 9.

Therefore, the preamplifiers 27.1, 27.2 isolate the spectral components of the differential frequency signal caused by respiration and cardiac activity. To extract information about the amplitude and phase of the reflected signal, the two generated quadrature signals of difference frequency at successive times are sent using multiplexers 28.1, 28.2 to the outputs of two multi-channel bandpass filters 29.1, 29.2. Multichannel bandpass filters 29.1, 29.2 suppress the component of the quadrature signals of the difference frequency caused by reflections from stationary objects, and isolate the variable component caused by movements, breathing and a heartbeat. The lower frequency bandwidth of each cell of a multichannel filter, which is determined by the parameters of the filter elements and the input impedance of the low-frequency amplifier, is selected on the order of 0.1 Hz to pass the spectral components caused by respiration. The signals from the outputs of the multi-channel band-pass filters 29.1, 29.2 are fed to demultiplexers 30.1, 30.2, made on standard analog microcircuits, with the help of which the outputs of the cells of the multi-channel band-pass filters 29.1, 29.2 are polled with the frequency specified by the processing and control unit 1. The sampling frequency of the channels of multi-channel bandpass filters 29.1, 29.2 is chosen so as to provide the possibility of digital processing of the signals acting on the outputs of the demultiplexers in real time.

The signals acting on the outputs of the demultiplexers are time-stretched copies of the variable components of the quadrature signals supplied to the inputs of the multiplexers. The outputs of the demultiplexers 30.1, 30.2 are connected to the inputs of short-circuit electronic switches 31.1 and 31.2, which carry out program-controlled discharge of the cells of multi-channel bandpass filters 29.1 and 29.2 to eliminate transients associated with the action of strong short-term signals that arise when moving objects in the irradiated zone. The control inputs of the electronic keys 31.1 and 31.2 through the interface 2 are connected to the processing and control unit 1. The signals from the outputs of short-circuit electronic switches 31.1 and 31.2 are fed to low-pass filters 32.1, 32.2 and further to the inputs of the analog-to-digital converter 16. The signal from the output of the analog-to-digital converter 16 through interface 2 is sent to the processing and control unit 1, in which spectral analysis is performed quadrature components of the signals corresponding to respiration and heartbeats. From the output of the processing and control unit 1, these signals are supplied to the liquid crystal indicator 18.

With the purposeful detection of living people in the rubble, under snow, etc., the calculator 25 closes and the geophysical radar provides an increase in the probability of detecting weak signals caused by respiratory and cardiac activity.

The interaction of the processing and control unit 1 with the remaining nodes of the radar, as well as the organization of the operation control, is carried out through interface schemes 2.

Controls, switching and indication are placed on a common control panel. Various options for using the display in search mode, as well as the operation of the device in auxiliary modes, do not change the essence of the described physical processes, but are determined only by the program of work of the processing and control unit 1.

Thus, the proposed radar, in comparison with the prototype, provides not only high reliability of detection and identification of various subsurface objects at different depths, but also hidden living creatures. This is achieved by spatial resolution and suppression of signals from stationary objects, which eliminates the interference caused by the presence of moving objects in the irradiated zone, increases the dynamic range of the receiving device and increases the likelihood of detecting weak signals caused by respiratory and cardiac activity. Thus, the functionality of the geophysical radar is expanded.

Claims (1)

A geophysical radar comprising a processing and control unit, an interface, a transmitter, which uses a shock excitation generator and a transmitting antenna connected to a second output, a first stroboscopic mixer, the second input of which is connected to the second output of the interface through the first gate driver, and trigger, receiving antenna connected in series, second mixer of a stroboscopic converter, the second input of which through the second form a strobe gate is connected to the third output of the interface, the first delay line, a trigger, a key, the second input of which is connected to the output of the second mixer, and an amplifier, the second input of which is connected via a digital-to-analog converter to the fourth output of the interface, to which the unit is connected to the fifth, sixth, and seventh outputs processing and control, a sound and liquid crystal display, respectively, and an analog-to-digital converter, a second delay line, a subtraction unit, the second input of which is connected to the second input, are connected nen with the output of the amplifier, an integrator, a division unit, the second input of which is connected to the output of the subtraction unit, and a comparison unit, the second input of which is connected to the eighth output of the interface through the unit for generating the reference voltage, and the output is connected to an analog-to-digital converter, characterized in that it is equipped with a switch, a quadrature demodulator and two processing channels, each of which consists of a series-connected pre-amplifier, a multiplexer, the second input of which is connected to the output of the second pho a gate master, a multi-channel bandpass filter, a demultiplexer, the second input of which is connected to the ninth output of the interface, an electronic short-circuit key, the second input of which is connected to the tenth output of the interface, and a low-frequency amplifier, the output of which is connected to an analog-to-digital converter, and to the first output of the transmitter in series a switch is connected, and a quadrature demodulator, the second input of which is connected to the output of the comparison unit, and two outputs are connected to the first and second channels brabotki respectively.