Ground penetrating method based on ground penetrating radar and frequency-adjustable impedance matching layer

Abstract

The application discloses a ground exploration method and system based on a ground penetrating radar and a frequency-adjustable impedance matching layer, which comprises the following steps: arranging a frequency-adjustable impedance matching layer on the top of a region to be measured; placing a ground penetrating radar above the impedance matching layer, wherein the ground penetrating radar comprises a host, a transmitting antenna and a receiving antenna; the host comprises a vector network analyzer, which is used to generate a stepped frequency signal; the transmitting antenna is used to transmit the stepped frequency signal generated by the vector network analyzer; the receiving antenna is used to receive a reflected echo signal of the region to be measured; and the spatial position, structure and form of an abnormal body in the region to be measured are determined. The vector network analyzer is a common instrument, and its operation is simple and easy to use. The voltage source of the FPGA is easy to control. The amplitude and phase of the reflection coefficient of the contact surface between the impedance matching layer and the measured body are controlled by loading a variable capacitance diode, so that the wideband reflection weakening and transmission enhancement phenomenon is formed.

Description

Technical Field

[0001] This application relates to the field of ground-penetrating radar and frequency-tunable impedance matching layer technology, and in particular to a ground-penetrating radar and frequency-tunable impedance matching layer method and apparatus. Background Technology

[0002] Ground penetrating radar, also known as ground-penetrating radar, transmits electromagnetic waves into the ground through a transmitting antenna and receives the reflected electromagnetic waves back to the surface through a receiving antenna. When the electromagnetic waves propagate in the underground medium, they are reflected when they encounter interfaces with electrical differences. Based on the waveform, amplitude, intensity, and time-related changes of the received electromagnetic waves, the spatial location, structure, shape, and burial depth of the underground medium can be inferred.

[0003] Most commonly used ground-penetrating radars (GPRs) utilize impulse pulse signals. The GPR travels along the survey line, radiating electromagnetic pulses downwards and receiving the echoes to achieve two-dimensional or three-dimensional imaging. To improve range resolution, these GPRs typically use short transmission pulses. However, limitations in transmission power restrict the effective range, and resolution is also limited by the pulse width. In practical applications, it is difficult to further improve detection depth and resolution.

[0004] Existing ground-penetrating radar (GPR) signal reflection suppression and enhancement technologies primarily employ image data processing to enhance radar signals through various methods, such as direct wave removal, surface reflection removal, background denoising, image filtering, and exponential gain. These methods essentially only enhance the display of the original data without adding any useful information, significantly impacting the real-time display of useful signals in GPR. Furthermore, the filtering and denoising process inevitably loses some useful signals, leading to interpretation errors and omissions in subsequent geological information analysis. While electromagnetic metamaterials can be used to create gain or frequency-selective surfaces or lenses with frequency selectivity, these still generate significant strong reflections when the improved signal propagates through the air-ground interface, resulting in very little electromagnetic signal reaching the ground. Existing metamaterial impedance matching layers are mostly passive and, due to thickness limitations, are costly and bulky, making them difficult to apply in practical detection. Summary of the Invention

[0005] Based on this, and in response to the aforementioned technical problems, a ground-penetrating radar-based method and apparatus based on a frequency-tunable impedance matching layer is provided to solve the problems of strong reflected signals, very few electromagnetic signals fed into the ground, and uncontrollable and thick matching layers when existing detection methods detect anomalies.

[0006] A first aspect is a ground-penetrating radar (GPR) method based on a frequency-tunable impedance matching layer, the method comprising:

[0007] A frequency-adjustable impedance matching layer is deployed on top of the area to be tested. The impedance matching layer includes multiple frequency-adjustable metamaterial units. Each metamaterial unit includes a substrate, a metal etched on the substrate with a special structure, and a varactor diode disposed on the substrate. The substrate is made of an insulating dielectric. Frequency stepping is achieved by applying an FPGA voltage source across the varactor diode to match the radar signal frequency.

[0008] A ground-penetrating radar is placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate the step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test.

[0009] A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar.

[0010] The ground-penetrating radar receives the echo signal reflected from the area under test.

[0011] Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

[0012] Optionally, in the above scheme, the impedance matching layer is connected to a reverse bias voltage source, which is used to regulate the frequency of the impedance matching layer.

[0013] In the above scheme, optionally, the step frequency signal includes at least one of frequency step size and bandwidth.

[0014] In the above scheme, optionally, both the transmitting antenna and the receiving antenna are horn antennas or butterfly antennas.

[0015] Optionally, in the above scheme, placing a ground-penetrating radar above the impedance matching layer includes:

[0016] The transmitting antenna and the receiving antenna are placed above the impedance matching layer.

[0017] In the above scheme, optionally, the distance between the transmitting antenna and the ground penetrating radar, and the distance between the receiving antenna and the ground penetrating radar are both less than a preset distance.

[0018] In the above scheme, optionally, before transmitting the stepped frequency signal to the impedance matching layer and the area under test via ground penetrating radar, the method further includes:

[0019] Initialize the ground-penetrating radar;

[0020] Set and save the sampling parameters of the ground-penetrating radar;

[0021] The dual ports of the ground-penetrating radar were calibrated and saved.

[0022] Secondly, a ground-penetrating radar (GPR) device based on a frequency-tunable impedance matching layer, the device comprising:

[0023] First deployment module: used to deploy a frequency-adjustable impedance matching layer on top of the area to be tested, wherein the impedance matching layer includes multiple frequency-adjustable metamaterial units, each metamaterial unit includes a substrate, a metal etched on the substrate and having a special structure, and a varactor diode disposed on the substrate, the substrate being made of an insulating dielectric.

[0024] Control module: Used to control the frequency-adjustable FPGA voltage source of the impedance matching layer. The FPGA voltage source is used to adjust the step frequency in real time to match the signal frequency emitted by the radar system, so as to achieve a broadband, high-resolution and deep detection effect.

[0025] The second deployment module is used to place a ground-penetrating radar above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test.

[0026] Transmission module: used to transmit step frequency signals to the impedance matching layer and the area under test via ground penetrating radar;

[0027] Receiving module: used to receive the echo signal reflected from the area to be measured by the ground penetrating radar;

[0028] Determination module: used to determine the spatial location, structure and morphology of the abnormal body in the test area based on the step frequency signal and the echo signal.

[0029] Thirdly, a computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the following steps:

[0030] The frequency step of the impedance matching layer with adjustable frequency is controlled on the top of the area to be tested. The impedance matching layer includes multiple metamaterial units with adjustable frequency. Each metamaterial unit includes a substrate, a metal etched on the substrate and having a special structure, and a varactor diode disposed on the substrate. The substrate is made of an insulating dielectric.

[0031] Data is obtained from a ground-penetrating radar placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test;

[0032] A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar.

[0033] The ground-penetrating radar receives the echo signal reflected from the area under test.

[0034] Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

[0035] Fourthly, a computer-readable storage medium having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0036] Data of a frequency-adjustable impedance matching layer is obtained on the top of the region to be tested. The impedance matching layer includes multiple frequency-adjustable metamaterial units. Each metamaterial unit includes a substrate, a metal etched on the substrate with a special structure, and a varactor diode disposed on the substrate. The substrate is made of an insulating dielectric.

[0037] Data is obtained from a ground-penetrating radar placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test;

[0038] A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar.

[0039] The ground-penetrating radar receives the echo signal reflected from the area under test.

[0040] Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

[0041] The present invention has at least the following beneficial effects:

[0042] First, the step-frequency ground-penetrating radar system, implemented using a vector network analyzer and a horn antenna, is low in construction cost, easy and flexible to operate, and features high range resolution, large dynamic range, high signal-to-noise ratio, and high average transmit power.

[0043] Second, the present invention achieves the amplitude and phase of the reflection coefficient of the contact surface between the impedance matching layer and the test object by loading a varactor diode, thus forming a broadband reflection reduction and transmission enhancement phenomenon.

[0044] Third, active control: Compared with passive matching, due to the addition of varactor diodes, the capacitance value of varactor diodes needs to be adjusted by a reverse bias voltage source to achieve adjustable or controllable frequency steps.

[0045] Fourth, wide bandwidth and ultra-thin: Compared with other reflection suppression and transmission enhancement technologies, this invention uses the ordinary electromagnetic interference principle and utilizes the characteristics of varactor diodes to adjust different reverse bias voltages to achieve the same frequency step size and bandwidth as the step frequency ground penetrating radar signal, thus taking into account both wide bandwidth and ultra-thin thickness.

[0046] Fifth, simple to manufacture: The frequency-tunable impedance matching layer structure provided by this invention is easy to process. At the same time, due to the properties of the left-handed material itself, the transmission enhancement performance of the matching layer does not depend on the relative permittivity of the dielectric substrate. This diversity of unit structure and the wide range of dielectric substrate materials have great advantages in manufacturing and application.

[0047] Sixth, wide applicability: The detection method proposed in this invention can be used in a variety of high-precision geological exploration and detection. The frequency-adjustable impedance matching layer detection method can achieve matching between different media, which can reduce the reflection of electromagnetic waves and enhance energy transmission. It can be used for the detection of natural media such as cement, soil and rock, as well as for the detection of artificial facilities such as highways, railways and tunnels. Attached Figure Description

[0048] Figure 1 This is a schematic flowchart of a ground-penetrating radar and frequency-tunable impedance matching layer method according to an embodiment of the present invention.

[0049] Figure 2 This is a schematic diagram illustrating an embodiment of the ground-penetrating radar and frequency-tunable impedance matching layer provided by an embodiment of the present invention.

[0050] Figure 3 A schematic diagram of a frequency-tunable impedance matching layer for a ground-penetrating radar-based method with a frequency-tunable impedance matching layer, provided in an embodiment of the present invention.

[0051] Figure 4This is a schematic diagram illustrating the workflow of a stepped-frequency ground-penetrating radar based on a ground-penetrating radar and a frequency-adjustable impedance matching layer, according to an embodiment of the present invention.

[0052] Figure 5 This is a schematic diagram of an example detection process of a ground-penetrating radar and frequency-tunable impedance matching layer method provided in an embodiment of the present invention.

[0053] Figure 6 A schematic diagram of the step-frequency radar signal scanning and sampling process of a ground-penetrating radar-based method with a frequency-adjustable impedance matching layer provided in an embodiment of the present invention;

[0054] Figure 7 This is a schematic diagram of the frequency-tunable impedance matching layer control and detection method provided in an embodiment of the present invention for a ground-penetrating radar and a frequency-tunable impedance matching layer-based ground-penetrating method.

[0055] Figure 8 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0057] In one embodiment, such as Figure 1 As shown, a ground-penetrating radar (GPR) method based on a frequency-tunable impedance matching layer is provided, including the following steps:

[0058] A frequency-adjustable impedance matching layer is deployed on top of the area to be tested. The impedance matching layer includes multiple frequency-adjustable metamaterial units. Each metamaterial unit includes a substrate, a metal etched on the substrate with a special structure, and a varactor diode disposed on the substrate. The substrate is made of an insulating dielectric. Frequency stepping is achieved by applying an FPGA voltage source across the varactor diode to match the radar signal frequency.

[0059] A ground-penetrating radar is placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate the step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test.

[0060] In one embodiment, the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna;

[0061] The host computer includes a vector network analyzer, which is used to generate the step frequency signal;

[0062] The transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer;

[0063] The receiving antenna is used to receive the echo signal reflected from the area under test.

[0064] In this embodiment, the echo signal is a frequency signal. To facilitate the plotting of Bscan images, the echo signal needs to be subjected to inverse Fourier transform, and then imaged using Matlab or Python software.

[0065] In this embodiment, the present invention provides a step-frequency ground-penetrating radar system implemented using a vector network analyzer and a horn antenna. It has low construction cost, is easy and flexible to operate, and features high range resolution, large dynamic range, high signal-to-noise ratio, and high average transmit power.

[0066] A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar.

[0067] The ground-penetrating radar receives the echo signal reflected from the area under test.

[0068] Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

[0069] In this embodiment, the frequency-tunable impedance matching layer can be fabricated using printed circuit board technology, by etching a specially structured metal onto an insulating dielectric substrate. The insulating dielectric substrate can be FR4, F4B, etc., and the metal is typically copper. Therefore, the cost of the frequency-tunable impedance matching layer is comparable to that of common circuit boards, offering high cost-effectiveness. Once successfully developed, it is suitable for large-scale production applications and is extremely thin.

[0070] In this embodiment, the frequency-tunable impedance matching layer is implemented using electromagnetic metamaterials, which can adjust the frequency in real time to achieve an ultra-wideband impedance matching mechanism, further improving radar detection resolution and depth.

[0071] In this application embodiment, the present application has the following advantages: First, the present application achieves wideband reflection reduction and transmission enhancement by loading a varactor diode to regulate the amplitude and phase of the reflection coefficient of the impedance matching layer and the contact surface of the test object; Second, active control: due to the loading of the varactor diode, the capacitance value of the varactor diode needs to be adjusted by a reverse bias voltage source to achieve frequency tunability; Third, wideband and ultra-thin: compared with other reflection suppression and transmission enhancement technologies, the present invention uses the ordinary electromagnetic interference principle, utilizes the characteristics of the varactor diode, and adjusts different reverse bias voltages to achieve the same frequency step size and bandwidth as the step frequency ground penetrating radar signal, thus taking into account both wide bandwidth and ultra-thin thickness; Fourth, simple manufacturing: the frequency tunable provided by the present invention... The impedance matching layer structure is easy to process. Furthermore, due to the inherent properties of the left-handed material, the transmission enhancement performance of the matching layer does not depend on the relative permittivity of the dielectric substrate. This diversity of unit structures and the wide range of dielectric substrate material choices offer significant advantages in manufacturing and application. Fifth, it is easy to control: the vector network analyzer, as a common instrument, is simple and easy to operate, and the voltage source control of the FPGA is also simple. Sixth, it has wide applicability: the radar system proposed in this invention can be used in various high-precision geological exploration and detection applications. The frequency-adjustable impedance matching layer detection method can achieve matching between different media, reducing electromagnetic wave reflection and enhancing energy transmission. It can be used for the detection of natural media such as cement, soil, and rock, as well as for the detection of man-made facilities such as highways, railways, and tunnels.

[0072] In one embodiment, such as Figure 2 The diagram illustrates a step-frequency ground-penetrating radar (GPR) system and a detection method using a frequency-tunable impedance matching layer. This embodiment provides a surface frequency-tunable impedance matching layer detection method for a step-frequency GPR system, comprising a step-frequency GPR main unit of a vector network analyzer (VNA), a pair of transceiver horn antennas, a frequency-tunable impedance matching layer, and corresponding FPGA-designed electronic equipment. The VNA's step-frequency GPR main unit generates a step-frequency signal. The pair of transceiver horn antennas receive and transmit the step-frequency signal. The frequency-tunable impedance matching layer reduces strong reflected electromagnetic waves at the air-to-ground interface, improves electromagnetic wave energy utilization, and matches the step-frequency signal to improve the radar's dynamic reception range. The FPGA-designed electronic equipment controls the step-frequency of the frequency-tunable impedance matching layer by continuously changing the reverse bias control varactor diode in automatic or manual modes to achieve frequency tuning.

[0073] Specifically, the detection method provided in this embodiment only includes the four parts mentioned above. The overall schematic diagram also includes the underground detection environment and underground anomalies.

[0074] In one embodiment, the impedance matching layer is connected to a reverse bias voltage source, which is used to regulate the frequency of the impedance matching layer.

[0075] In one embodiment, such as Figure 3 The diagram shows a frequency-tunable impedance matching layer provided in an embodiment of the present invention. Matching layer principle: The frequency-tunable impedance layer is designed based on the amplitude and phase conditions of multiple interference principles, which can further improve detection resolution and detection depth. The presence of the varactor diode only changes the phase, achieving a frequency shift in the response. The frequency-tunable impedance matching layer consists of several frequency-controllable metamaterial units; each metamaterial unit includes an insulating dielectric substrate, and the rectangle in the diagram is actually a patterned special metal etching structure. The frequency-tunable impedance matching layer is implemented using an electromagnetic metamaterial with a loaded varactor diode. In the front view, the top layer has a specially patterned metal structure, which is often welded to the varactor diode using a slotted approach. In the side view, the power layer and ground layer are located in the middle to avoid affecting the top layer structure, and separating the power and ground layers effectively avoids signal crosstalk and other problems. To achieve power feeding for the top varactor diode, a blind via is used to process the substrate material, and only two pins are provided for voltage control. By selecting the unit size of the metamaterial and the special metal structure, it can be considered that a basic electromagnetic characteristic with a specific function (such as high-resistance or low-resistance materials) is achieved. By adjusting the external control circuit, the varactor diode can make the center frequency of the matching layer controllable within a certain range.

[0076] In this embodiment, the frequency-adjustable impedance matching layer can be fabricated using printed circuit board technology, by etching a specially structured metal onto an insulating dielectric substrate. Common dielectric substrate materials include FR4 and F4B, and the metal is typically copper. Therefore, the cost of the frequency-adjustable impedance matching layer is comparable to that of common circuit boards, offering high cost-effectiveness. Once successfully developed, it is suitable for large-scale production applications and can be extremely thin.

[0077] In this implementation, since the impedance matching layer is a two-dimensional planar structure and is uniform relative to the ground, it is only necessary to adjust the control reverse bias voltage of each unit structure simultaneously, and the control circuit used is relatively simple.

[0078] In this embodiment, a varactor diode is selected during control. The voltage source controller can use a programmable gate array (FPGA).

[0079] The frequency-adjustable impedance matching layer detection method of this embodiment has the following beneficial effects: It possesses impedance matching characteristics; if this matching layer is applied for detection, surface reflection is weakened, the detection depth increases, and energy utilization and signal-to-noise ratio are significantly improved. The complete ground-penetrating radar system constituted in this embodiment can dynamically adjust and match the frequency range of the step-frequency ground-penetrating radar, further significantly improving the dynamic receiving range of the ground-penetrating radar.

[0080] In this embodiment, the frequency-adjustable impedance matching layer is used to reduce strong reflected electromagnetic waves between the air-to-ground interface, improve electromagnetic wave energy utilization, and match the step frequency signal to improve the dynamic receiving range of the radar.

[0081] In one embodiment, such as Figure 4 The diagram shown is a flowchart of the working logic of the step-frequency ground-penetrating radar system provided in this embodiment. The radar system needs to be powered on and initialized first. After setting the sampling parameters, dual-port calibration is performed, and the above steps are saved as parameters for easy access later. Then, data saving settings are performed, including the data type and storage location. After these steps are completed, data acquisition and storage can begin.

[0082] In one embodiment, the step frequency signal includes at least one of frequency step size and bandwidth.

[0083] In this embodiment, in actual use, the vector network analyzer can be parameterized according to user needs to meet the actual application; the signal provided by the vector network analyzer is a frequency domain signal, so only the frequency step size and bandwidth parameters need to be given to generate a step frequency signal that meets the requirements.

[0084] In one embodiment, such as Figure 5 The diagram illustrates the step-frequency ground-penetrating radar system and frequency-adjustable impedance matching layer detection process provided in this embodiment. The VNA generates a step-frequency signal, which is transmitted through a horn antenna, passing through the impedance matching layer and geological structures, and reflected back to the receiving horn antenna via an anomalous body. The echo signal needs to be mixed and filtered to obtain the I and Q signals corresponding to the real and imaginary parts, respectively, and finally combined into a complex signal. This complex signal is then converted into a time-series signal using an inverse Fourier transform (IDFT) to form an image.

[0085] In one embodiment, such as Figure 6 The diagram illustrates the step-frequency radar signal scanning and sampling process provided in this embodiment. Figure (a) shows the signal scanning process, and (b) shows the signal acquisition process. The VNA step-frequency ground-penetrating radar is a continuous wave radar whose operating frequency is stepped in a stepped manner. Within one scanning cycle, the frequency of the signal transmitted by the radar changes from the initial frequency f... start The frequency gradually increases to the termination frequency f at frequency intervals Δf. stopThe transmitted stepped-frequency signal comprises N coherent pulses with a pulse width (duration) of T. Generally, the frequency interval (referred to as the frequency sampling rate in signal processing) Δf ≥ 1 / T is required. The signal frequency of the nth pulse can be expressed as:

[0086] f n =f0+nΔf n=0,1,2,3,……,N-1

[0087] The signal can be represented as:

[0088]

[0089] In the formula: Its absolute bandwidth B = f stop -f start rect(t) is a rectangular window function.

[0090] Coherent pulses typically increase in increments of a fixed frequency Δf, therefore the frequency interval between coherent pulses is...

[0091] N coherent pulses constitute a step scan frame. The transmission process of one step frequency frame by a VNA step frequency radar is one frequency scan process. The scan time is NT, also known as the correlation processing time, because target information is obtained by relying on the correlation processing time of the coherent pulses in the pulse frame. The single scan time is equal to the correlation processing time (NT) plus the system scan delay δ; the sampling measurement time is τ.

[0092] In one embodiment, both the transmitting antenna and the receiving antenna are horn antennas.

[0093] In this embodiment, the transmitting antenna and the receiving antenna are composed of a pair of horn antennas.

[0094] In one embodiment, placing a ground-penetrating radar above the impedance matching layer includes:

[0095] The transmitting antenna and the receiving antenna are placed above the impedance matching layer.

[0096] In one embodiment, the distance between the transmitting antenna and the ground penetrating radar, and the distance between the receiving antenna and the ground penetrating radar, can be close to the surface of the matching layer.

[0097] In this embodiment, the ground-penetrating radar antenna and receiving antenna are placed directly above the frequency-adjustable impedance matching layer. The distance between the transmitting antenna and the ground-penetrating radar, and the distance between the receiving antenna and the ground-penetrating radar, are both less than a preset distance to reduce direct wave coupling. The preset distance is ten wavelengths of the center frequency. In one embodiment, the maximum distance between the transmitting antenna and the ground-penetrating radar, and the maximum distance between the receiving antenna and the ground-penetrating radar, does not exceed ten wavelengths of the center frequency. At the minimum, they can be placed directly on the surface of the matching layer, as a foam layer provides protection, satisfying the application scenario, and the distance is limited to above the matching layer. Figure 2 As shown.

[0098] In one embodiment, such as Figure 7 The diagram shown is a flowchart of the frequency-adjustable impedance matching layer control and detection method provided in this embodiment. First, the FPGA voltage source needs to be powered on and programmed via JTAG from the computer. Then, the power supply terminal is connected to the corresponding positive and negative terminals of the frequency-adjustable impedance matching layer. The initial voltage is adjusted using buttons and confirmed on the digital display. Next, the voltage switching mode is set. If automatic switching is enabled, the voltage step interval is set before detection begins. If automatic switching voltage is insufficient, manual switching settings can be used, adjusting the frequency and voltage correspondence to achieve adjustable fixed-frequency steps. Finally, the detection results are displayed and the final acquired data is stored.

[0099] Conventional ground-penetrating radars (GPRs) utilize impulse pulse signals. The radar travels along the survey line, radiating electromagnetic pulses downwards and receiving echoes to achieve two-dimensional or three-dimensional imaging. To improve range resolution, this type of GPR typically uses short transmit pulses. However, limitations in transmit power restrict the effective range, and resolution is also limited by the pulse width, making further improvements in detection depth and resolution difficult in practical applications. This embodiment uses a vector network analyzer (VNA) as the radar host to transmit stepped-frequency signals for geological exploration. This can improve resolution and detection depth for shallow targets to some extent, and is cost-effective and feature-rich. However, it cannot avoid strong electromagnetic wave reflections caused by impedance changes between air and the ground, resulting in low electromagnetic energy utilization and failing to meet the resolution and depth requirements for deeper layers. Existing GPR signal reflection suppression and enhancement technologies mainly employ image data processing to enhance radar signals through various methods, such as direct wave removal, surface reflection removal, background denoising, image filtering, and exponential gain. These methods essentially only enhance the display of raw data without adding any useful information, significantly impacting the real-time display of useful signals in ground-penetrating radar (GPR). Furthermore, some useful signals are lost during the filtering and denoising process, leading to misinterpretations and omissions in subsequent geological information interpretation. Gains created using electromagnetic metamaterials, or frequency-selective surfaces or lenses with frequency selectivity, still generate significant strong reflections when the improved signal propagates through the ground interface, resulting in very little electromagnetic signal reaching the subsurface. Existing matching layer technologies, such as quarter-impedance matching layers and layered medium matching layers, are thick, have a single frequency, and relatively narrow bandwidth, which is unfavorable for practical geological exploration scenarios. Although matching layer methods combining electromagnetic metamaterials exist, they are all passive and cannot balance bandwidth and thickness.

[0100] In this embodiment, the step-frequency ground-penetrating radar system implemented using a vector network analyzer and a horn antenna is low in construction cost, easy and flexible to operate, and features high range resolution, large dynamic range, high signal-to-noise ratio, and high average transmit power.

[0101] This embodiment also has the following beneficial effects:

[0102] (1) This embodiment is the first to discover that by loading a varactor diode, the amplitude and phase of the reflection coefficient of the matching layer and the contact surface of the test object can be adjusted to form a broadband reflection reduction and transmission enhancement phenomenon.

[0103] (2) Active control: Due to the loading of varactor diodes, the capacitance value needs to be controlled by an external reverse bias source to achieve frequency adjustment.

[0104] (3) Wide bandwidth and ultra-thin: Compared with other reflection suppression and transmission enhancement technologies, this invention uses the ordinary electromagnetic interference principle and utilizes the characteristics of varactor diodes to adjust different reverse bias voltages to achieve the same frequency step and bandwidth as the step frequency ground penetrating radar signal, thus taking into account both wide bandwidth and ultra-thin thickness.

[0105] (4) Simple to manufacture: The frequency-adjustable impedance matching layer structure provided by the present invention is easy to process. At the same time, due to the properties of the left-hand material itself, the transmission enhancement performance of the matching layer does not depend on the relative permittivity of the dielectric substrate. The diversity of this unit structure and the wide range of dielectric substrate materials have great advantages in manufacturing and application.

[0106] (5) Easy to control: Vector network analyzers are common instruments that are easy to operate and get started with. The voltage source control of FPGA is also simple.

[0107] (6) Wide applicability: The radar system proposed in this invention can be used in a variety of high-precision geological exploration and detection. The frequency-adjustable impedance matching layer detection method can achieve matching between different media, which can reduce the reflection of electromagnetic waves and enhance energy transmission. It can be used for the detection of natural media such as cement, soil and rock, as well as for the detection of artificial facilities such as highways, railways and tunnels.

[0108] It should be understood that, although Figure 1 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0109] In one embodiment, a ground-penetrating radar-based ground-penetrating device with a frequency-tunable impedance matching layer is provided, comprising the following program modules:

[0110] First deployment module: used to deploy a frequency-adjustable impedance matching layer on top of the area to be tested, wherein the impedance matching layer includes multiple frequency-adjustable metamaterial units, each metamaterial unit includes a substrate, a metal etched on the substrate and having a special structure, and a varactor diode disposed on the substrate, the substrate being made of an insulating dielectric.

[0111] Control module: Used to control the frequency-adjustable FPGA voltage source of the impedance matching layer. The FPGA voltage source is used to adjust the step frequency in real time to match the signal frequency emitted by the radar system, so as to achieve a wide bandwidth, high resolution and deep depth detection effect.

[0112] The second deployment module is used to place a ground-penetrating radar above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test.

[0113] Transmission module: used to transmit step frequency signals to the impedance matching layer and the area under test via ground penetrating radar;

[0114] Receiving module: used to receive the echo signal reflected from the area to be measured by the ground penetrating radar;

[0115] The determination module is used to determine the spatial location, structure, and morphology of the anomaly within the test area based on the step frequency signal and the echo signal. Specific limitations regarding the ground-penetrating radar (GPR) and frequency-adjustable impedance matching layer-based ground-penetrating device can be found in the above description of the ground-penetrating radar and frequency-adjustable impedance matching layer-based ground-penetrating method, and will not be repeated here. Each module in the aforementioned GPR and frequency-adjustable impedance matching layer-based ground-penetrating device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the operations corresponding to each module.

[0116] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 8As shown. This computer device includes a communication bus, a processor, a memory, a communication interface, and a voltage output port. The processor, memory, communication interface, and voltage output port communicate and provide feedback to each other via the communication bus. The processor can call computer programs stored in the memory and run on the processor to perform the following steps: setting an initial voltage and displaying it on a digital tube; setting the voltage switching mode to automatic or manual; using the communication interface to program the voltage regulation and displaying the read-back actual voltage value on a serial port assistant; the memory is mainly used to store some programmed data and manually adjusted voltage values ​​for playback and correction of test data; furthermore, the above voltage control is mainly achieved by converting the digital voltage to an analog voltage using a DAC (Digital-to-Analog Converter), and then amplifying it by a specified factor using a power amplifier. The voltage resolution is limited by the DAC, but the accuracy of a typical DAC is sufficient to meet the requirements of this electronic device. This computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor of this computer device provides computing and control capabilities. The memory of this computer device includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The communication interface of the computer device is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a ground-penetrating radar method based on a frequency-adjustable impedance matching layer. The display screen of the computer device can be an LCD screen or an e-ink display screen. The input device can be a touch layer covering the display screen, buttons, a trackball, or a touchpad located on the computer device casing, or an external keyboard, touchpad, or mouse.

[0117] Those skilled in the art will understand that Figure 8 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0118] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program relating to all or part of the processes in the methods of the above embodiments.

[0119] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon relating to all or part of the processes in the methods of the above embodiments.

[0120] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A ground exploration method based on ground penetrating radar and a frequency-adjustable impedance matching layer, characterized in that, The method includes: A frequency-adjustable impedance matching layer is deployed on top of the area to be tested, and the frequency is controlled by an FPGA voltage source. The impedance matching layer includes multiple frequency-adjustable metamaterial units. Each metamaterial unit includes a substrate, a metal etched on the substrate with a special structure, and a varactor diode disposed on the top layer of the substrate. The substrate is made of an insulating dielectric. The FPGA voltage source is used to control the voltage across the varactor diode. The frequency step of the impedance matching layer is achieved by changing the voltage amplitude. The frequency-adjustable characteristic of the impedance matching layer is achieved by connecting the varactor diode to the reverse bias voltage source provided by the FPGA voltage source. The frequency step of the impedance matching layer is achieved by continuously adjusting the corresponding reverse bias voltage. The FPGA voltage source is used to continuously change the reverse bias voltage to control the equivalent capacitance of the varactor diode through automatic switching mode or manual switching mode to achieve frequency adjustment. In automatic switching mode, the voltage step interval is set and then detected. In manual switching mode, the frequency and voltage are adjusted according to the correspondence, thereby achieving adjustable fixed frequency step. A ground-penetrating radar is placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test. A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar. The ground-penetrating radar receives the echo signal reflected from the area under test. Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

2. The method of claim 1, wherein, The step frequency signal includes at least one of frequency step size and bandwidth.

3. The method of claim 1, wherein, Both the transmitting and receiving antennas are horn antennas, but broadband antennas such as dish antennas can also be used instead of horn antennas.

4. The method of claim 1, wherein, Placing a ground-penetrating radar above the impedance matching layer includes: The transmitting antenna and the receiving antenna are placed above the impedance matching layer.

5. The method according to claim 4, characterized in that, The distance between the transmitting antenna and the ground-penetrating radar, and the distance between the receiving antenna and the ground-penetrating radar, are both less than a preset distance.

6. The method according to claim 1, characterized in that, Before transmitting a stepped-frequency signal to the impedance matching layer and the area under test via ground-penetrating radar, the method further includes: Initialize the ground-penetrating radar; Set and save the sampling parameters of the ground-penetrating radar; The dual ports of the ground-penetrating radar were calibrated and saved.

7. A ground-penetrating radar-based device with a frequency-adjustable impedance matching layer, characterized in that, The device includes: First deployment module: used to deploy a frequency-adjustable impedance matching layer on top of the area to be tested, wherein the impedance matching layer includes multiple frequency-adjustable metamaterial units, each metamaterial unit includes a substrate, a metal etched on the substrate and having a special structure, and a varactor diode disposed on the top layer of the substrate, wherein the substrate is made of an insulating dielectric. Control module: Used to control the frequency-adjustable FPGA voltage source of the impedance matching layer. The FPGA voltage source is used to adjust the step frequency in real time to match the signal frequency emitted by the radar system, so as to achieve a wide bandwidth, high resolution and deep depth detection effect. The frequency-adjustable characteristic of the impedance matching layer is achieved by connecting the varactor diode to the reverse bias voltage source provided by the FPGA voltage source. The frequency step of the impedance matching layer is achieved by continuously adjusting the corresponding reverse bias voltage. The FPGA voltage source is used to continuously change the reverse bias voltage to control the equivalent capacitance of the varactor diode through automatic switching mode or manual switching mode to achieve frequency adjustment. In automatic switching mode, the voltage step interval is set and then detected. In manual switching mode, the frequency and voltage are adjusted according to the correspondence, thereby achieving adjustable fixed frequency step. The second deployment module is used to place a ground-penetrating radar above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test. Transmission module: used to transmit step frequency signals to the impedance matching layer and the area under test via ground penetrating radar; Receiving module: used to receive the echo signal reflected from the area to be measured by the ground penetrating radar; Determination module: used to determine the spatial location, structure and morphology of the abnormal body in the test area based on the step frequency signal and the echo signal.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, The processor performs the following steps: The frequency step of the impedance matching layer with adjustable frequency is controlled on the top of the area to be tested. The impedance matching layer includes multiple metamaterial units with adjustable frequency. Each metamaterial unit includes a substrate, a metal etched on the substrate and having a special structure, and a varactor diode disposed on the substrate. The substrate is made of an insulating dielectric. Data from a ground-penetrating radar (GPR) placed above the impedance matching layer is acquired. The GPR includes a main unit, a transmitting antenna, and a receiving antenna. The main unit includes a vector network analyzer, which generates a step frequency signal. The transmitting antenna transmits the step frequency signal generated by the vector network analyzer. The receiving antenna receives the echo signal reflected from the area under test. The frequency adjustability of the impedance matching layer is achieved by connecting a varactor diode to a reverse bias voltage source provided by an FPGA voltage source. The frequency stepping of the impedance matching layer is achieved by continuously adjusting the corresponding reverse bias voltage. The FPGA voltage source continuously changes the reverse bias voltage to control the equivalent capacitance of the varactor diode through automatic or manual switching modes to achieve frequency adjustability. In automatic switching mode, the voltage step interval is set before detection. In manual switching mode, adjustments are made based on the correspondence between frequency and voltage to achieve adjustable fixed-frequency steps. A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar. The ground-penetrating radar receives the echo signal reflected from the area under test. Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the following steps: controlling the frequency stepping of an adjustable impedance matching layer deployed on top of the region under test, wherein the impedance matching layer includes multiple frequency-adjustable metamaterial units, each metamaterial unit including a substrate, a metal etched on the substrate with a special structure, and a varactor diode disposed on the substrate, the substrate being made of an insulating dielectric; the frequency-adjustable characteristic of the impedance matching layer is achieved by connecting the varactor diode to a reverse bias voltage source provided by an FPGA voltage source, and the frequency stepping of the impedance matching layer is achieved by continuously adjusting the corresponding reverse bias voltage; the FPGA voltage source is used to continuously change the reverse bias voltage to control the equivalent capacitance of the varactor diode through automatic switching mode or manual switching mode to achieve frequency adjustability; wherein, in automatic switching mode, the voltage step interval is set before detection; in manual switching mode, the frequency and voltage are adjusted according to the correspondence, thereby achieving adjustable fixed frequency stepping; Data is obtained from a ground-penetrating radar placed above the impedance matching layer; wherein the ground-penetrating radar includes a main unit, a transmitting antenna, and a receiving antenna; the main unit includes a vector network analyzer, which is used to generate a step frequency signal; the transmitting antenna is used to transmit the step frequency signal generated by the vector network analyzer; and the receiving antenna is used to receive the echo signal reflected from the area under test; A step frequency signal is transmitted to the impedance matching layer and the area to be tested by ground penetrating radar. The ground-penetrating radar receives the echo signal reflected from the area under test. Based on the step frequency signal and the echo signal, the spatial location, structure, and morphology of the abnormal body in the area to be tested are determined.

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