MIMO antenna array for highway maintenance

Abstract

This invention belongs to the field of radar technology, and particularly relates to a MIMO antenna array for highway maintenance. It includes antenna modules with transmit / receive channels, two sets of antenna modules scanning simultaneously, and a pair of transmit / receive channels scanning sequentially to form a spatial grid; and a programming module for editing the operating parameters of the antenna elements. The simultaneous scanning of the antenna modules and the sequential scanning of the transmit / receive channels improve scanning efficiency. The programming module, used to edit the operating parameters of the antenna elements, provides more scanning modes suitable for various working scenarios.

Description

Technical Field

[0001] This invention belongs to the field of radar technology, and in particular relates to a MIMO antenna array for highway maintenance. Background Technology

[0002] As one of the most important transportation facilities, highways are closely related to social development and people's lives. Road transportation plays a crucial role in economic development and the modernization of industry and agriculture. During their actual service life, roads are constantly subjected to the influence of various factors such as atmosphere, moisture, vehicles, and sunlight. These factors interact with the road structure, accelerating deformation and aging of pavement materials. Ultimately, this leads to varying degrees of structural defects such as loosening, settlement, and voids, reducing the load-bearing capacity of the road structure, decreasing driving comfort, and even causing road collapse accidents.

[0003] To improve driving comfort and achieve zero-disaster goals, how to quickly, accurately, and scientifically identify and repair potential hazards at an early stage, prevent further deterioration of structural performance, extend the service life of highways, and reduce the waste of social resources has become a critical issue that urgently needs to be addressed in the field of highway engineering maintenance. Ground-penetrating radar (GPR) is an efficient and non-destructive road inspection method. In road engineering applications, GPR emits high-frequency pulsed electromagnetic waves through a transmitter antenna. These electromagnetic waves travel into the road surface structure and undergo reflection, diffraction, and refraction when encountering interfaces with different dielectric properties or underground targets. By analyzing the reflected echo signals received by the GPR receiver, the parameters of the road structure layers, the location and extent of defects, etc., can be analyzed. However, in highway maintenance, GPR is generally used for vehicle-mounted scanning of the road surface structure. Under this working condition, the scanning effect and efficiency of the directional antenna are limited by its narrow bandwidth, thick profile, and large size. Therefore, in order to improve the effect and efficiency of ground-penetrating radar, the radar antenna can be further improved according to the characteristics of highway maintenance. Summary of the Invention

[0004] To solve or improve the above problems, the present invention provides a MIMO antenna array for highway maintenance, the specific technical solution of which is as follows:

[0005] This invention provides a MIMO antenna array for highway maintenance, comprising: an antenna module including a transmit / receive channel, two sets of the antenna modules scanning simultaneously, and a pair of transmit / receive channels scanning sequentially to form a spatial grid; and a programming module for editing the operating parameters of the antenna elements.

[0006] Preferably, the antenna module includes 21 channels consisting of a transmit channel and a receive channel, wherein the first antenna group includes channels 1-10 and the second antenna group includes channels 11-21; the first antenna group and the second antenna group scan simultaneously, and when the signal is transmitted, the transmit channel is spaced 10 TX transmit antennas apart.

[0007] Preferably, the programming module is used to edit the operating parameters of the antenna elements, including: editing the operating parameters of all antenna elements to collect data with a 7.5*7.5cm grid; and editing the operating parameters of some antenna elements to form a sparse grid for data collection.

[0008] Preferably, the antenna module uses a butterfly antenna as the basic unit, has a frequency selection surface with low-pass or band-stop characteristics, and applies resistance loading technology.

[0009] Preferably, the antenna module uses a lumped or distributed resistor loading method to improve current reflection at the antenna end.

[0010] Preferably, the frequency selective surface is provided with an absorbing material to absorb the back electromagnetic waves radiated by the antenna.

[0011] Preferably, the transmitting antenna and the receiving antenna in the antenna module use non-coplanar dielectric substrates and ground planes to suppress the propagation of surface waves; the dielectric substrate is an FR-4 dielectric substrate with a dielectric constant of 4.3±0.1 and a dielectric loss tangent of 0.025.

[0012] Preferably, a single negative material is loaded between the antennas to suppress the transmission of space waves.

[0013] Preferably, the transmitting antenna and the receiving antenna are arranged in a V-shape to suppress the transmission of space waves.

[0014] Preferably, the operating frequency of the MIMO antenna array is 200MHz-2000MHz.

[0015] The beneficial effects of the present invention are as follows: the antenna module includes a transmit / receive channel, two sets of the antenna modules scan simultaneously, and a pair of transmit / receive channels are scanned sequentially to form a spatial grid, which can improve the scanning efficiency; the programming module is used to edit the working parameters of the antenna element, which can provide more scanning modes and is suitable for various working scenarios. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a MIMO antenna array according to the present invention. Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0019] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0020] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0021] To address or improve the problems mentioned in the background, the present invention provides, as follows: Figure 1 The MIMO antenna array shown for highway maintenance includes: an antenna module 1, including a transmit / receive channel, two sets of the antenna modules scanning simultaneously, and a pair of transmit / receive channels scanning sequentially to form a spatial grid; and a programming module 2, used to edit the operating parameters of the antenna elements.

[0022] The antenna module includes 21 channels consisting of a transmit channel and a receive channel. The first antenna group includes channels 1-10, and the second antenna group includes channels 11-21. The first antenna group and the second antenna group scan simultaneously, and when transmitting signals, the transmit channels are spaced 10 TX transmit antennas apart.

[0023] The programming module is used to edit the operating parameters of the antenna elements, including: editing the operating parameters of all antenna elements to collect data with a 7.5*7.5cm grid; and editing the operating parameters of some antenna elements to form a sparse grid for data collection.

[0024] The antenna module uses a butterfly antenna as its basic unit, has a frequency selectivity surface with low-pass or band-stop characteristics, and applies resistance loading technology.

[0025] The antenna module improves current reflection at the antenna end by using a lumped or distributed resistor loading method.

[0026] The frequency-selective surface is provided with absorbing material to absorb the back electromagnetic waves radiated by the antenna.

[0027] The transmitting and receiving antennas in the antenna module use non-coplanar dielectric substrates and ground planes to suppress the propagation of surface waves.

[0028] A single negative material is loaded between the antennas to suppress the transmission of space waves.

[0029] The transmitting antenna and the receiving antenna are arranged in a V-shape to suppress the transmission of space waves. Example

[0030] The antenna system is a crucial component of ground-penetrating radar (GPR), significantly influencing its performance. The antenna system is designed based on the application scenario and design objectives. Specifically, antenna elements can be arranged into one 1×21 element transmit / receive array; the antenna array can be divided into two groups (elements 1-10 and 11-21), with both groups scanning simultaneously and a pair of transmit / receive antenna elements scanning sequentially, forming a relatively sparse spatial grid for high-speed surveying; simultaneously, the spacing between antenna elements is maintained at 10 TX transmit antennas to ensure that the two transmitted signals do not interfere with each other. The antenna array system can acquire multiple scan sections in a single acquisition. Depending on the application, the system can be programmed to use all antenna elements of the antenna array to acquire data in a 7.5×7.5cm grid, thereby obtaining a 3D image. When using vehicle-mounted scanning, it can provide antenna technology support for road surface detection at speeds ranging from a minimum of 5 km / h to a maximum of 90 km / h.

[0031] The detection depth of ground-penetrating radar (GPR) is related to energy attenuation and dispersion. When electromagnetic waves enter the ground, their amplitude decreases exponentially with increasing propagation depth. Therefore, the choice of operating frequency is crucial for GPR. From the perspective of detection depth, a low frequency should be chosen. However, too low a frequency will result in insufficient resolution, and an excessively low frequency will also lead to an excessively large antenna size. Considering detection depth, accuracy, and resolution, this embodiment determines the operating frequency to be between 200MHz and 2000MHz.

[0032] By employing multimode coupling technology and LCR circuit / absorbing material loading technology, the problems of narrow bandwidth, thick profile, and large size of directional antennas are solved, resulting in an ultra-wideband, low-profile, and miniaturized directional antenna to support the system in achieving high-resolution and dense scanning grids at great depth. Phase correction technology is used to ensure a stable radiation direction within the 200MHz-2000MHz frequency band.

[0033] To achieve rapid scanning, the system employs a frequency-stepping mechanism. Simultaneously, to accelerate ground scanning speed, the antenna system utilizes a gridded design, with 21 antenna channels (including transmit and receive channels). During measurement, the radar scans sequentially in pairs (transmit / receive) antenna arrays, divided into two groups (1-10) and (11-21), with both groups scanning simultaneously to expedite the process. Furthermore, a spacing of 10 TX transmit antennas ensures that the two transmit signals do not interfere with each other. The antenna elements are arranged linearly, with transmit and receive signals corresponding to each other. Multiple scan sections can be acquired in a single acquisition. Depending on the application, the system can be programmed to use all antenna elements in a 7.5×7.5cm grid to acquire data, thus obtaining a true 3D image. Alternatively, the system can be programmed to utilize only a subset of antenna elements to form a sparser spatial grid for high-speed surveying. When using a vehicle-mounted scanning method, it is expected to operate normally at a minimum speed of 5 km / h and a maximum speed of 90 km / h.

[0034] A wavelength of 200MHz reaches 1500mm, while the channel spacing is only 75mm; therefore, the antenna size must be very small. Simultaneously, due to size constraints, the antenna profile should be low. These requirements necessitate designing an antenna system with an ultra-wide bandwidth, low profile, and extremely small size. Furthermore, this embodiment requires the antenna to achieve a stable radiation pattern within the 200MHz-2000MHz range, which presents significant challenges for antenna design. Therefore, this embodiment proposes using a butterfly antenna as the basic unit and employs the following technologies to meet these requirements:

[0035] (a) A resistor loading technique is proposed. By using lumped or distributed resistor loading, the current reflection at the antenna tip can be improved to some extent, thereby improving impedance matching and widening the effective operating bandwidth of the antenna. To achieve the directional radiation characteristics of the antenna, a metal plate is loaded on the back of the dipole antenna. To reduce the impact of the loaded metal plate on antenna matching, a metal back cavity is typically loaded at a distance of one-quarter wavelength from the antenna plane. The addition of the metal back cavity also introduces capacitive loading, which improves the antenna impedance matching to some extent. Resistive loading also helps suppress the time-domain signal tailing effect and improve the antenna resolution. Regarding the impact of the tailing effect on the received waveform, a thicker dielectric substrate is usually used. Increased thickness leads to a decrease in Q value, thus expanding the bandwidth. An FR-4 dielectric substrate with a dielectric constant of 4.3 ± 0.1 and a dielectric loss tangent of 0.025 is proposed.

[0036] Dipole antennas radiate in both directions. According to the phase compensation principle, the electromagnetic wave radiated backward by the antenna, after being reflected by the metal ground plane, will not be in phase with the electromagnetic wave radiated forward, resulting in a null point in the main radiation direction. Based on the periodicity of electromagnetic wave propagation, the metal ground plane is typically positioned at a quarter wavelength from the dipole. This ensures that the reflected wave returns to the dipole's radiating surface precisely in phase with the forward-radiated electromagnetic wave. To address issues such as radiation pattern distortion and split lobes in ultra-wideband antennas at high frequencies, this embodiment introduces a frequency selective surface (FSS) and absorbing materials.

[0037] (b) Frequency Selective Surface: To ensure that the ultra-wideband antenna maintains good radiation performance over a wide frequency band, the frequency selective surface must have wideband characteristics and meet the following conditions: (1) Low-frequency electromagnetic waves are unaffected, that is, electromagnetic waves can be transmitted through the antenna in the low-frequency part; (2) High-frequency electromagnetic waves are blocked from passing through, that is, electromagnetic waves are totally reflected by the antenna in the high-frequency part. This requires the frequency selective surface to have low-pass or band-stop characteristics. After loading the frequency selective surface, the phase of the electromagnetic wave at a specific frequency point can be changed, thus solving the problem of antenna radiation pattern distortion.

[0038] (c) Absorbing Material Technology: Frequency selective surfaces can achieve phase correction by changing the reflection phase of the back-radiated electromagnetic wave, thereby aligning the phase of the back-radiated electromagnetic wave with the forward electromagnetic wave. However, both electromagnetic bandgap and frequency selective surfaces typically have narrow bandwidths, requiring multi-layer structures to achieve broadband characteristics.

[0039] Coupling between antennas not only affects their radiation efficiency but also interferes with useful received signals, degrades system performance, and can even cause system failure. This system uses a 21-channel antenna array, and the miniaturized antennas result in excessively close spacing, leading to significant coupling between them. This necessitates research into decoupling techniques for this antenna array. In this system, the transmitting and receiving antennas are arranged in separate columns, and the effects of mutual coupling can be divided into those between transmitting antennas and those between transmitting and receiving antennas.

[0040] The radiation characteristics between antenna array elements (between transmitting antennas) are analyzed, including near-field and far-field characteristics. Surface currents can also be used to analyze the effects of mutual coupling between antennas. The analysis identifies two types of coupling between antenna elements: one caused by spatially coupled electromagnetic waves, where, under near-field conditions, some electromagnetic energy is coupled to other adjacent antenna elements, resulting in enhanced coupling and poorer isolation; the other caused by surface waves, where some electromagnetic energy is transmitted through the ground plane or coupled to other antenna ports after the antenna is excited at the feed point, generating surface currents and causing mutual coupling between antenna elements. In this embodiment, two methods are used to improve the isolation between the two transmission channels: electromagnetic bandgap to suppress surface wave transmission and single-negative metamaterials to suppress spatial wave propagation.

[0041] In nature, materials can be classified into four categories based on their constitutive parameters, namely equivalent permittivity and equivalent permeability: (1) materials with both positive equivalent permittivity and equivalent permeability; (2) materials with both negative equivalent permittivity and equivalent permeability; (3) materials with negative equivalent permittivity and positive equivalent permeability; and (4) materials with positive equivalent permittivity and negative equivalent permeability. In (3) and (4), electromagnetic waves will attenuate sharply in the material, exhibiting stopband characteristics. Therefore, applying this material to the isolation between antennas can effectively suppress the influence of space waves. In the 2.9-4.7 GHz range, electromagnetic waves cannot be transmitted with a single negative material at frequencies less than -10 dB. After loading a single negative material between antennas, the isolation between antennas is significantly reduced, effectively suppressing the transmission of space waves.

[0042] On the one hand, if the distance between the transmitting and receiving antennas is too close, the electromagnetic waves radiated by the two antennas may interfere with each other. The transmitted signal from the transmitting antenna may be directly transmitted to the receiving antenna, confusing the received echo signal and making it difficult to extract the information of the target being measured.

[0043] On the other hand, since the transmitting and receiving antennas share a common substrate and metal ground plane, surface waves propagate on this plane. According to the principle of surface wave propagation, when a surface wave propagates to any discontinuous plane, it will generate traveling wave diffraction, radiating energy into free space. Therefore, it is proposed to use non-coplanar dielectric substrates and ground planes to suppress the propagation of surface waves, thereby improving the isolation between the transmitting and receiving antennas. The transmitting and receiving antennas adopt a V-shaped array arrangement to suppress the transmission of surface waves. The radiation areas of the transmitting and receiving antennas only partially overlap, which can effectively reduce the coupling between the transmitting and receiving antennas and improve the isolation between the transmitting and receiving branches.

[0044] By comparing the isolation between collinear and non-collinear transmitting and receiving antennas (distance difference s), the results show that the isolation is maximized when s = I / 2 (where I is the spacing between antenna elements) when the transmitting and receiving antennas are non-collinear. Furthermore, since the system uses 21 channels, antenna reusability requires each of the 10 antenna elements to serve as a receiving branch twice for each detection. Therefore, a cross-distribution helps to fully utilize the internal space of the ground-penetrating radar and facilitates wiring. This scheme improves the isolation between the transmitting and receiving antennas without significantly increasing the array size.

[0045] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of each example have been generally described in terms of function in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0046] In the embodiments provided in this application, it should be understood that the division of units is only a logical functional division. In actual implementation, there may be other division methods, such as multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A MIMO antenna array for highway maintenance, characterized by, include: An antenna module includes a transmit / receive channel. Two sets of the antenna modules scan simultaneously, and a pair of transmit / receive channels are scanned sequentially to form a spatial grid. The programming module is used to edit the operating parameters of the antenna vibrator; The antenna module includes 21 channels consisting of a transmit channel and a receive channel, wherein the first antenna group includes channels 1-10 and the second antenna group includes channels 11-21; The first antenna group and the second antenna group scan simultaneously, and when the signal is transmitted, the transmission channel is spaced 10 TX transmission antennas apart; The MIMO antenna array operates at frequencies ranging from 200MHz to 2000MHz.

2. The MIMO antenna array of claim 1, wherein, The programming module is used to edit the operating parameters of the antenna vibrator, including: Edit the operating parameters of all antenna elements to 7.

5. Data was collected using a 7.5cm grid. Edit the operating parameters of some antenna elements to form a sparse grid for data acquisition.

3. The MIMO antenna array according to claim 2, characterized in that, The antenna module uses a butterfly antenna as its basic unit, has a frequency selectivity surface with low-pass or band-stop characteristics, and applies resistance loading technology.

4. The MIMO antenna array according to claim 3, characterized in that, The antenna module improves current reflection at the antenna end by using a lumped or distributed resistor loading method.

5. The MIMO antenna array according to claim 4, characterized in that, The frequency-selective surface is provided with absorbing material to absorb the back electromagnetic waves radiated by the antenna.

6. The MIMO antenna array according to claim 5, characterized in that, The transmitting and receiving antennas in the antenna module use non-coplanar dielectric substrates and ground planes to suppress the propagation of surface waves. The dielectric substrate is an FR-4 dielectric substrate with a dielectric constant of 4.3±0.1 and a dielectric loss tangent of 0.

025.

7. The MIMO antenna array according to claim 6, characterized in that, A single negative material is loaded between the antennas to suppress the transmission of space waves.

8. The MIMO antenna array according to claim 7, characterized in that, The transmitting antenna and the receiving antenna are arranged in a V-shape to suppress the transmission of space waves.

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