JP2016090297A - Underground radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a chirp signal as a transmission signal, receive a reflection wave from an underground buried object and reduce unwanted components generating in a correlation signal undergoing correlation processing by a reference signal.SOLUTION: An underground radar device using a chirp signal (S) as a transmission signal transmitting (2) toward an underground, receiving (3) a reflection wave from an underground buried object, and exploring the buried object on the basis of a correlation signal (S) undergoing correlation processing (4) of a reception signal of the radar device (S) with a reference signal (S). As the transmission signal and reference signal (S), the underground radar device uses a plurality of kinds of chirp signals, and explores the buried object by a signal (S) of an average waveform in which an addition averaging (5) of a plurality of kinds of correlation signals obtained by the correlation processing is executed.SELECTED DRAWING: Figure 1

Description

  The present invention uses a chirp signal as a transmission signal to be transmitted toward the ground, receives a reflected wave from the buried object in the ground, and searches for the buried object based on a correlation signal subjected to correlation processing with a reference signal. Specifically, the present invention relates to a ground penetrating radar apparatus that reduces unnecessary components generated in the correlation signal.

  In a general use environment of a ground penetrating radar apparatus, a reflected signal component from the ground surface on which the apparatus is placed is received in addition to a reflected signal component from an underground object to be originally searched. When the amplitudes of these signals are compared, the reflected signal component from the ground surface is generally much larger. If the reflected signal from the underground object is sufficiently amplified in the amplification system of the receiving unit, the reflected signal from the ground surface may saturate beyond the limit of the output amplitude of the amplifier. .

  As a conventional device of this type, an electromagnetic wave is transmitted from the electromagnetic wave transmission unit to the ground, a reflected wave based on the electromagnetic wave is received by the electromagnetic wave reception unit, and the underground is received based on a reception signal of the electromagnetic wave reception unit. A ground penetrating radar apparatus has been proposed for exploring buried objects (see, for example, Patent Document 1).

  As another device of this type, an electromagnetic wave transmitting / receiving means for radiating an electromagnetic wave into the medium while moving on the surface of the medium and receiving the reflected wave, and a movement with respect to the received intensity based on the received signal data There has been proposed an embedded object exploration device including image data generating means for generating two-dimensional image data indicating a relationship between a distance and a reflection time indicating an elapsed time from emission to reception of electromagnetic waves (for example, Patent Document 2). reference).

JP 2010-210394 A JP 2011-247844 A

  In recent years, for pulse wave radar exploration, for the purpose of increasing transmission energy, improving resolution, increasing the exploration depth, etc., the frequency of the transmitted signal has changed from low to high as the time elapses. Alternatively, a chirp radar exploration underground radar apparatus using a chirp signal that is a signal that continuously changes from a high frequency to a low frequency has been proposed.

  In such a chirp radar exploration underground radar device, a chirp signal is used as a transmission signal to be transmitted toward the ground, a reflected wave from a buried object in the ground is received, and the received signal is used as a reference signal. By performing correlation processing, a pulse-like correlation signal is obtained, and the buried object is searched based on the correlation signal. However, if the amplification amount of the amplifier is increased in order to sufficiently amplify the reflected signal from the buried object in the receiver's amplification system, the received chirp signal due to reflection from the ground surface will limit the output amplitude of the amplifier. There is a possibility of saturation beyond this, and the result of correlation processing between the received signal (chirp signal) in this saturated state and the reference signal (correlation signal) is an unnecessary ringing component (side lobe) other than the side lobe due to the correlation of the original chirp signal. ) May occur.

  If this is expressed in the exploration data of the ground penetrating radar device, for example, an image parallel to the reflection image on the ground surface is generated in a deep portion. Of the parallel images other than the reflection image of the ground surface, it is difficult to distinguish the reflection image from the buried object that is originally located at the depth and the image due to unnecessary ringing components. The search performance of the radar device may be degraded.

  In order to avoid this, the conventional apparatus has taken measures such as determining the amplification amount of the amplifier of the receiving unit to such an extent that the reflected signal from the ground surface is not saturated. As a result, the amplification of the reflected signal from the buried object having a small amplitude compared to the reflected signal becomes insufficient, and it becomes difficult to search for the buried object. Therefore, the exploration performance of the ground penetrating radar device may be deteriorated.

  Accordingly, the problem to be solved by the present invention that addresses such problems is a correlation in which a chirp signal is used as a transmission signal, a reflected wave from an underground buried object is received, and correlation processing is performed using a reference signal. An object of the present invention is to provide a ground penetrating radar device that reduces unnecessary components generated in a signal.

  In order to solve the above problems, a ground penetrating radar apparatus according to the present invention uses a chirp signal as a transmission signal transmitted toward the ground, receives a reflected wave from a buried object in the ground, and refers to the received signal. A ground penetrating radar apparatus that searches the buried object based on a correlation signal subjected to correlation processing using a signal, using a plurality of types of chirp signals as the transmission signal and a reference signal, and a plurality of types obtained by the correlation processing The buried object is searched for using an average waveform signal obtained by averaging the correlation signals.

  According to the underground radar apparatus of the present invention, a plurality of types of chirp signals are used as reference signals for correlation processing of transmission signals transmitted toward the ground and reception signals from underground objects, and the received signals are The buried object can be probed by a signal having an average waveform obtained by averaging a plurality of types of correlation signals obtained by performing correlation processing with a reference signal. In this case, an unnecessary component generated in the correlation signal can be reduced by obtaining an average waveform signal obtained by averaging the plurality of types of correlation signals. Therefore, it is possible to suppress the deterioration of the exploration performance of the underground radar device.

It is a block diagram which shows embodiment of the underground radar apparatus by this invention. It is a block diagram which shows the internal structure of the 1st and 2nd chirp signal generation part of the said underground radar apparatus. It is a block diagram which shows the internal structure of the addition average process part of the said underground radar apparatus. It is a wave form diagram which shows a reference | standard chirp signal waveform. It is a wave form diagram which shows the chirp signal waveform which changed the starting phase with respect to the reference | standard. It is a wave form diagram which shows the chirp signal waveform which inverted frequency transition with respect to the reference | standard. It is a wave form diagram which shows the chirp signal waveform which changed the start phase and reversed the frequency transition with respect to the reference | standard. It is a graph which shows an example of a received signal when there is an underground thing in the ground. It is a graph which shows an example of the correlation signal obtained by the correlation process of a received signal and a reference signal. It is a wave form diagram which shows the correlation signal waveform which performed the correlation process in the state in which the reference | standard chirp signal was saturated. It is a wave form diagram which shows the correlation signal waveform which performed the correlation process in the state which the chirp signal which changed the start phase with respect to the reference | standard is saturated. It is a wave form diagram which shows the correlation signal waveform which carried out the averaging of the correlation signal in the state where the reference chirp signal was saturated, and the correlation signal in the state where the chirp signal whose start phase was changed with respect to the reference was saturated. It is a wave form diagram which shows the correlation signal waveform which performed the correlation process in the state which the chirp signal which inverted frequency transition with respect to the reference | standard is saturated. It is a wave form diagram which shows the correlation signal waveform which carried out the average of the correlation signal of the state where the reference chirp signal was saturated, and the correlation signal of the state where the chirp signal which inverted the frequency transition with respect to the reference was saturated.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The ground penetrating radar device transmits an electromagnetic wave from the electromagnetic wave transmission unit to the ground, receives the reflected wave based on the electromagnetic wave at the electromagnetic wave reception unit, and is embedded in the ground based on the reception signal of the electromagnetic wave reception unit Exploration of buried objects. In recent years, for pulse wave radar exploration with a simple circuit configuration, the frequency of the transmitted signal has increased over time for the purpose of increasing transmission energy, improving resolution, increasing the exploration depth, etc. A ground penetrating radar apparatus using a chirp radar exploration using a chirp signal that is a signal that continuously changes from low frequency to high frequency or from high frequency to low frequency has been proposed.

  FIG. 1 is a block diagram showing an embodiment of a ground penetrating radar apparatus according to the present invention. The underground radar apparatus uses a chirp signal as a transmission signal to be transmitted toward the ground, receives a reflected wave from the underground embedded object, and performs a correlation process using a reference signal, thereby the embedded object. As shown in FIG. 1, a first chirp signal generator 1a for transmission, a second chirp signal generator 1b for correlation processing, a transmission antenna 2, a reception antenna 3, and a correlator 4, an addition average processing unit 5, a display unit 6, a waveform switching control unit 7, and a timing control unit 8.

  The first chirp signal generator 1a generates a chirp signal used as a transmission signal to be transmitted toward the ground, and generates a plurality of types of chirp signals with an internal configuration as described later. . The second chirp signal generator 1b generates a chirp signal used as a reference signal for correlation processing of a received signal that has received a reflected wave from a buried object in the ground. Thus, a plurality of types of chirp signals are generated.

  The transmission antenna 2 transmits the chirp signal as the transmission signal generated by the first chirp signal generator 1a to the ground after being amplified by the amplifier 9. The receiving antenna 3 receives a reflected wave reflected from an underground object, and the signal is amplified by the amplifier 10 and then sent to the correlator 4 as a received signal.

  The correlator 4 receives the reception signal from the amplifier 10 and also inputs a plurality of types of chirp signals generated from the second chirp signal generation unit 1b, and uses the reception signal as the reference signal as the chirp signal. Correlation processing is performed to generate a plurality of types of correlation signals. The addition average processing unit 5 averages a plurality of types of correlation signals obtained by the correlation processing of the correlator 4, and generates an average waveform signal with an internal configuration as described later. ing.

  The display unit 6 creates display data based on the average waveform signal generated by the addition average processing unit 5 and displays it as an image.

The waveform switching control unit 7 sends the waveform switching signal S ₁ to the first and second chirp signal generation units 1 a and 1 b and the addition average processing unit 5. This waveform switching signal S ₁ switches waveform data of a plurality of types of chirp signals stored in first and second chirp signal generation units 1 a and 1 b described later, and is stored in an addition average processing unit 5 described later. The waveform data of a plurality of types of correlation signals is switched.

Further, the timing control unit 8, the first and second chirp signal generator 1a, is for sending the timing control signal S ₂ to 1b. This timing control signal S ₂ is a chirp signal for correlation processing generated from the second chirp signal generator 1 b (transmission signal) with respect to the chirp signal for transmission (transmission signal) generated from the first chirp signal generator 1 a. The reference signal) is generated while being shifted little by little at the nanosecond (ns) level, so that the correlator 4 can perform correlation processing on the received signal from the amplifier 10 with the reference signal.

  FIG. 2 is a block diagram showing an internal configuration of the first and second chirp signal generators 1a and 1b. Since the internal configurations of the first and second chirp signal generators 1a and 1b are the same, only the first chirp signal generator 1a will be described here. As shown in FIG. 2, the first chirp signal generator 1 a includes a data memory 11, a memory address controller 12, and a D / A converter 13.

  The data memory 11 serves as a waveform storage unit for storing waveform data of a plurality of types of chirp signals. The data memory 11 is made to correspond to chirp signals having different waveforms such as waveform data 1, 2, 3,... In an internal unit storage area. Each of which is stored. For example, waveform data of a reference chirp signal (start phase 0 deg.) As shown in FIG. As the waveform data 2, as shown in FIG. 5, the waveform data of a chirp signal (start phase 90 deg.) In which the start phase is changed with respect to the reference chirp signal shown in FIG. As the waveform data 3, waveform data of a chirp signal (frequency transition inversion) obtained by inverting the frequency transition with respect to the reference chirp signal shown in FIG. 4 is stored. As the waveform data 4, the waveform data of the chirp signal (composite) in which the frequency transition is inverted with respect to the chirp signal (start phase 90 deg.) Shown in FIG. In FIG. 2, the data memory 11 stores four types of waveform data, but any number of waveform data may be stored as long as it is two or more types.

  Further, the plurality of types of chirp signals are not limited to the chirp signals having the waveforms shown in FIGS. 4 to 7, and a theoretical autocorrelation is based on one chirp signal (for example, a chirp signal as shown in FIG. 4). A plurality of chirp signals having the same waveform may be included.

  The data memory 11 is a waveform storage unit that stores waveform data of a plurality of types of chirp signals as software. However, the present invention is not limited to this, and corresponds to the data memory 11 and the D / A converter 13. A hardware circuit may include a plurality of waveform generation circuits that generate waveforms corresponding to chirp signals having different waveforms.

Memory address controller 12, and outputs switch the waveform data of a plurality of types of chirp signals stored in the data memory 11, a waveform switching signals S ₁ sent from the waveform switching controller 7 shown in FIG. 1 The address control signal S ₃ is input and sent to the data memory 11.

The D / A converter 13 performs D / A conversion on the digital chirp signal read from the data memory 11 under the control of the memory address control unit 12, and is sent from the timing control unit 8 shown in FIG. A timing control signal S ₂ is input, and a specific chirp signal S ₄ is output to the amplifier 9 shown in FIG. 1 by the timing control.

Note that the second chirp signal generator 1b is a first chirp signal generator 1a basically the same configuration described above, the correlation as a chirp signal S ₄ the reference signal outputted from the D / A converter 13 The difference is that it is output to the device 4.

  FIG. 3 is a block diagram showing an internal configuration of the addition average processing unit 5. This addition average processing unit 5 selects and averages a plurality of correlation signals from a plurality of types of correlation signals. As shown in FIG. 3, an A / D converter 14, a data buffer 15, and an addition A divider 16 is provided.

The A / D converter 14 receives a plurality of analog correlation signals S ₅ output from the correlator 4, performs A / D conversion, and sends them to the data buffer 15.

  The data buffer 15 serves as a storage unit for storing data of a plurality of types of correlation signals sent from the A / D converter 14, and the correlation signal data 1, 2, 3,... In addition, they are stored in correspondence with correlation signals having different waveforms. At this time, each correlation signal having a different waveform is stored in each storage area while performing address control. In FIG. 3, the data buffer 15 stores four types of correlation signal data. However, any number of two or more types of data may be stored.

The adder / divider 16 adds and divides a plurality of correlation signals read from the data buffer 15 and averages them. The waveform switching signal S ₁ sent from the waveform switching control unit 7 shown in FIG. Thus, a plurality of correlation signals read from the data buffer 15 are added and averaged. The average waveform signal S ₆ output from the adder / divider 16 is sent to the display unit 6 shown in FIG.

Next, the operation of the ground radar device configured as described above will be described.
In FIG. 1, first, the waveform switching signal S ₁ is transmitted from the waveform switching control unit 7 and the timing control signal S ₂ is transmitted from the timing control unit 8 to the first chirp signal generation unit 1 a for transmission. At the same time, the waveform switching signal S ₁ and the timing control signal S ₂ are similarly sent to the second chirp signal generator 1 b for correlation processing.

Then, in FIG. 2, the first chirp signal generator 1 a receives the waveform switching signal S ₁ sent from the waveform switching controller 7 and sends the address control signal S ₃ from the memory address controller 12 to the data memory 11. The waveform data of a plurality of types of chirp signals stored in the data memory 11 are switched and output. For example, the reference chirp signal waveform (reference: start phase 0 deg.) Data shown in FIG. 4 is read from the address of the waveform data 1 and sent to the D / A converter 13. The D / A converter 13 receives the timing control signal S ₂ sent from the timing control unit 8 and outputs a specific chirp signal S ₄ by the timing control. Chirp signal S ₄ that is output is amplified by the input to the amplifier 9 shown in FIG. 1, it is transmitted from the transmitting antenna 2 toward the ground as a transmission signal.

Thereafter, similarly, from the data memory 11 in the first chirp signal generator 1a, the data of the chirp signal waveform (start phase 90 deg.) With the start phase changed from the address of the waveform data 2 with respect to the reference shown in FIG. Read, read the data of the chirp signal waveform (frequency transition inversion) with the frequency transition inverted with respect to the reference shown in FIG. 6 from the waveform data 3 address, and set the start phase with respect to the reference shown in FIG. The data of the chirp signal waveform (composite) changed and inverted in frequency transition is read out. In the same manner as described above, the chirp signal S ₄ generated by the first chirp signal generator 1a is transmitted as a transmission signal from the transmission antenna 2 toward the ground.

In parallel with this, the second chirp signal generator 1b operates in the same manner as the first chirp signal generator 1a, and from the address of the waveform data 1 in the data memory 11 therein, the reference shown in FIG. Read the chirp signal waveform (reference) data. Then, after D / A conversion by the D / A converter 13, that particular chirp signal S ₄ as a reference signal for correlation processing, sent to the correlator 4 shown in FIG.

Thereafter, similarly, from the data memory 11 in the second chirp signal generator 1b, data of the chirp signal waveform (start phase 90 deg.) With the start phase changed with respect to the reference shown in FIG. Read, read the data of the chirp signal waveform (frequency transition inversion) with the frequency transition inverted with respect to the reference shown in FIG. 6 from the waveform data 3 address, and set the start phase with respect to the reference shown in FIG. The data of the chirp signal waveform (composite) changed and inverted in frequency transition is read out. In the same manner as described above, the chirp signal S ₄ generated by the second chirp signal generator 1 b is sent to the correlator 4 as a reference signal for correlation processing.

On the other hand, the transmitted wave transmitted from the transmitting antenna 2 toward the ground is reflected from an underground object or the like, and the reflected wave is received by the receiving antenna 3 shown in FIG. As shown in FIG. 8, when the received signal is buried in the ground, the reflected wave W ₁ from the ground surface appears at a certain time and from the buried object at a time farther than that. A small reflected wave W ₂ appears. The received signal received by the receiving antenna 3 is amplified by the amplifier 10 and sent to the correlator 4.

The correlator 4, and inputs the received signal S ₇ amplified by the amplifier 10 receives the chirp signal S ₄ that is output from said second chirp signal generator 1b as a reference signal, the received signal S ₇ Correlation processing is performed with the reference signal (S ₄ ) to obtain a pulsed correlation signal S ₅ . At this time, in order to see the waveform of the correlation signal corresponding to a small reflected waves W ₂ from buried object shown in FIG. 8, when increasing the amount of amplification of the reception side of the amplifier 10, the chirp of the reception due to reflection from the ground surface The signal saturates beyond the limit of the output amplitude of the amplifier 10, and as shown in FIG. 9, a ringing component different from the original side lobe (unnecessary) is present on both sides or one side of the main lobe of the reflected wave W ₁ from the ground surface. Component) occurs.

  FIG. 10 is a waveform diagram showing a correlation signal waveform obtained by performing correlation processing in a state where the reference chirp signal shown in FIG. 4 is saturated. A ringing component as an unnecessary component is generated in a range indicated by reference symbol A. Since this ringing component is a false image in the distance direction in the waveform of the correlation signal, it needs to be reduced.

Correlation signal S ₅ output from the correlator 4 is input to the averaging process unit 5 shown in FIG. In FIG. 3, the correlation signal S ₅ from the correlator 4 is input to the A / D converter 14, A / D converted, and sent to the data buffer 15. Data buffer 15, and an address control for each correlation signals of different waveforms, and stores the data of the correlation signal S ₅ to the respective storage areas. For example, the correlation signal waveform (reference) data obtained by performing the correlation process in a state where the reference chirp signal shown in FIG.

Thereafter, the correlator 4 correlates the received signal S ₇ with the reference signal (S ₄ ) read from the address of the waveform data 2, 3, 4 in the data memory 11 in the second chirp signal generator 1b. A pulse-like correlation signal S ₅ is obtained and sent to the averaging processor 5. In this averaging processing unit 5, the data buffer 15 is processed in the same manner as described above, and the data buffer 15 performs the correlation signal waveform (starting) in a state where the chirp signal whose starting phase is changed with respect to the reference shown in FIG. Data of phase 90 deg.) Is stored as correlation signal data 2 and data of a correlation signal waveform (frequency transition inversion) obtained by performing correlation processing in a state where a chirp signal whose frequency transition is inverted with respect to the reference shown in FIG. 13 is saturated. Is stored as correlation signal data 3.

  In FIG. 11, a ringing component as an unnecessary component is generated in a range indicated by a symbol B, and a ringing component as an unnecessary component is generated in a range indicated by a symbol C in FIG. 13. Further, FIG. 13 shows a correlation signal waveform obtained by performing correlation processing in a state where a chirp signal whose frequency transition is inverted with respect to the reference is saturated. However, as a similar waveform, a signal (start phase changed with respect to the reference). 90 deg.), The correlation signal waveform (composite) data obtained by performing the correlation process in a state where the chirp signal whose frequency transition is inverted is saturated may be stored as the correlation signal data 4.

The data buffer 15 receives the waveform switching signal S ₁ from the waveform switching control unit 7, selects and reads data of a plurality of types of correlation signals, and sends them to the adder / divider 16. The adder / divider 16 adds and divides and averages a plurality of correlation signals read from the data buffer 15. For example, the saturation correlation signal waveform (reference) shown in FIG. 10 and the saturation correlation signal waveform (start phase 90 deg.) Shown in FIG. 11 are selected and averaged. Then, as shown in FIG. 12, the signal S ₆ of the correlation signal waveform (start phase 90deg.) And averaging the averaged waveform shown in FIG. 11 and the correlation signal waveform (reference) shown in FIG. 10 is obtained. As is apparent from FIG. 12, the ringing component in the range A shown in FIG. 10 and the ringing component in the range B shown in FIG. 11 are small.

Further, for example, the correlation signal waveform at saturation (reference) shown in FIG. 10 and the correlation signal waveform at saturation (frequency transition inversion) shown in FIG. 13 are selected and averaged. Then, as shown in FIG. 14, the signal S ₆ of the correlation signal waveform (reference) and the correlation signal waveforms at saturation shown in FIG. 13 (frequency transition inversion) and averaging the averaged waveform shown in FIG. 10 is obtained. As apparent from FIG. 14, the ringing component in the range A shown in FIG. 10 and the ringing component in the range C shown in FIG. 13 are small.

The average waveform signal S ₆ output from the adder / divider 16 in the addition average processing unit 5 is sent to the display unit 6 shown in FIG. The display unit 6 creates display data based on the average waveform signal S ₆ generated by the addition average processing unit 5 and displays it as an exploration image of the underground object. In this case, unnecessary components (ringing components) generated in the correlation signal can be reduced. Therefore, it is possible to suppress the deterioration of the exploration performance of the underground radar device.

  Note that the configuration, shape, size, arrangement relationship, and the like described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented. Therefore, the present invention is not limited to the embodiments described above, and can be modified in various forms without departing from the scope of the technical idea shown in the claims.

DESCRIPTION OF SYMBOLS 1a ... 1st chirp signal generation part 1b ... 2nd chirp signal generation part 2 ... Transmitting antenna 3 ... Reception antenna 4 ... Correlator 5 ... Addition averaging process part 6 ... Display part 7 ... Waveform switching control part 8 ... Timing control part 9 , 10 ... Amplifier 11 ... Data memory 12 ... Memory address control unit 13 ... D / A converter 14 ... A / D converter 15 ... Data buffer 16 ... Adder / divider

Claims (6)

A chirp signal is used as a transmission signal to be transmitted toward the ground, a reflected wave from the underground buried object is received, and the buried object is searched based on a correlation signal obtained by correlating the received signal with a reference signal. A ground penetrating radar device,
A ground penetrating radar that uses a plurality of types of chirp signals as the transmission signal and a reference signal, and searches for the buried object using a signal having an average waveform obtained by averaging the plurality of types of correlation signals obtained by the correlation processing. apparatus.   The ground radar apparatus according to claim 1, wherein the plurality of types of chirp signals include a plurality of chirp signals having the same theoretical autocorrelation waveform based on one chirp signal.   The plurality of types of chirp signals are based on one chirp signal and a chirp signal with a start phase changed with respect to the reference, or a chirp signal with a frequency transition inverted with respect to the reference, or the start phase 2. The ground penetrating radar apparatus according to claim 1, wherein the chirp signal is a chirp signal obtained by inverting frequency transition with respect to a chirp signal obtained by changing the frequency.   4. The chirp signal of the plurality of types is output from a chirp signal generation unit including a waveform storage unit that stores waveform data corresponding to chirp signals having different waveforms. The ground penetrating radar device described in 1.   4. The chirp signal is output from a chirp signal generator having a plurality of waveform generation circuits that generate waveforms corresponding to chirp signals having different waveforms. The ground penetrating radar apparatus according to item 1.   6. The average waveform signal obtained by averaging the correlation signals is generated by an averaging processor that selects and averages any number of the plurality of types of correlation signals. The ground penetrating radar apparatus according to any one of the above.