TDM-MIMO solid side slope three-dimensional high-resolution foundation monitoring system

Abstract

The invention discloses a TDM-MIMO (Time Division Multiplexing-Multiple Input Multiple Output) solid-state slope three-dimensional high-resolution foundation monitoring system, which comprises a TDM-MIMO solid-state monitoring unit and an intelligent corner reflection system, the TDM-MIMO solid state monitoring unit comprises an MIMO antenna array, a dual-frequency antenna array and a fully polarized antenna array; the TDM-MIMO solid state monitoring unit is used for three-dimensional high-precision calculation of the slope direction, and the intelligent corner reflection system is used for fine adjustment of the azimuth angle and the elevation angle in the process of high-precision three-dimensional deformation monitoring of the slope. By adopting the technical scheme of the invention, the observation angle is automatically adjusted according to the real monitoring environment, the one-dimensional sight line direction calculation of the side slope is improved to the three-dimensional high-precision calculation of the slope direction, and the resolution of distance direction and azimuth direction imaging is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ground slope monitoring, and in particular relates to a TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system. Background Art

[0002] The concept of GB-SAR technology was first proposed by Italian Professor D. Tarchi in 1999. The technology is an active radar remote sensing technology. The first linear scanning GB-SAR IBIS system abroad was jointly developed by the Italian IDS company and the University of Florence, and is mainly used for monitoring the displacement changes of ground slopes. Ground-based synthetic aperture radar interferometry has the advantages of all-day and all-weather observation. As a supplement to satellite-borne synthetic aperture radar interferometry, it is often used for deformation monitoring of glaciers, landslides, volcanoes and other surfaces, as well as fine monitoring of artificial buildings. Compared with satellite-borne and airborne platform SAR, GB-SAR has more advantages in observation angle, revisit cycle, flexibility of use and cost. More importantly, the GB-SAR zero-baseline interferometry mode can remove baseline errors, and the multi-angle observation mode can remove terrain errors. In view of the defects of the existing GB-SAR, many institutions have started the research of solid-state GB-SAR. The Italian IDE company first developed IBIS-L / S / M and other equipment. Later, IDS GeoRadar developed IBIS-FM, IBIS-ARC, IBIS-FS+ and other equipment, which are widely used in slope instability monitoring at home and abroad. In view of this, the Fast-GBSAR system of Metasensing Company in the Netherlands, the ISPAS system in Norway, the interferometric radar system of ONERA in France, the Risk-SAR system of the Polytechnic University of Catalonia in Spain, the MELISSA system of the University of Florence and the GBSAR produced by Multimedia University have been launched one after another. In China, the China Nonferrous Metals Changsha Survey and Design Institute has developed the OnlineSAR2000 arc GB-SAR, the China Institute of Work Safety has developed a slope synthetic aperture radar (S-SAR) system, the China Coal Research Institute Shenyang has established a "on-site + remote" slope radar monitoring and early warning system, Zhonghong Ruida (Xiamen) Technology Co., Ltd. has developed a fully polarized GB-SAR system, Beijing Institute of Technology Leiko Electronic Information Technology Co., Ltd. has developed a slope deformation monitoring system, Inner Mongolia Autonomous Region Directional Pattern Technology Co., Ltd. has developed a micro-deformation monitoring rotating radar RSA system, and Suzhou Institute of Technology Leiko Sensing Technology Co., Ltd. has produced a fully solid-state MIMO GB-SAR system, which has greatly made up for the shortcomings of domestic equipment.

[0003] At present, the ground-based radar monitoring equipment for slopes at home and abroad is limited to one-dimensional line-of-sight deformation, and its three-dimensional solution accuracy is limited by the assumption of zero deformation in a certain direction. In addition, the vertical deformation of the conventional decomposition is only a projection mapping of the actual slope deformation, which makes it difficult to accurately reveal the temporal and spatial evolution law of the slope body; in addition, the azimuth resolution of existing equipment is generally low, which restricts the establishment of an accurate linkage model between the apparent parameters and hidden parameters of the slope. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] A TDM-MIMO solid-state slope three-dimensional high-resolution ground-based monitoring system includes: a TDM-MIMO solid-state monitoring unit and an intelligent corner reflection system; the TDM-MIMO solid-state monitoring unit includes: a MIMO antenna array, a dual-frequency antenna array, and a fully polarized antenna array; the TDM-MIMO solid-state monitoring unit is used for three-dimensional high-precision solution of slope direction, and the intelligent corner reflection system is used for fine-tuning the azimuth and elevation directions during the process of high-precision three-dimensional deformation monitoring of the slope.

[0007] Preferably, the TDM-MIMO solid-state monitoring unit adopts a concave shaft design, which is integrated by three sets of independent transmitting and receiving antenna array devices on the left, middle and right, and the three sets of antennas share one main control unit.

[0008] Preferably, the TDM-MIMO solid-state monitoring unit adopts the TDM method to achieve signal separation. First, a range-Doppler fast Fourier transform is performed on each transmit-receive pair, and each two-dimensional FFT corresponds to a virtual antenna; then an incoherent summation is performed to create a pre-detection matrix, and the peaks corresponding to valid targets in the matrix are identified; for each valid object, an angle FFT is performed on the corresponding peaks of multiple two-dimensional FFTs to identify the signal arrival angle of the object; finally, the three-dimensional deformation field of the slope landslide is calculated according to the design parameters of the ground-based radar and the deformation measurement results in the line of sight.

[0009] As a preferred method, the calculation formula for the three-dimensional deformation field of the slope landslide is:

[0010]

[0011] Among them, d S d U and d V are the three-dimensional deformations of the slope along the slope direction, the slope normal direction and the slope perpendicular direction respectively; α i (i=1,2,3) represents different radar sensor elevation angles; θ represents the slope angle; It represents the deformation monitoring results of different radar units in the line of sight. γ can be determined by the distance from the slope center to the radar body and from the observation target to the radar body.

[0012] Preferably, the corner reflector bracket of the intelligent corner reflection system is automatically adjusted within the range of 90° horizontally and 15° vertically.

[0013] Preferably, the intelligent corner reflection system uses a triangular pyramidal magnesium-aluminum plate as the cross section.

[0014] Preferably, the TDM-MIMO solid-state monitoring unit is configured with 27 transmitting channels and 36 receiving channels through a cascade design, and a time division multiplexing mechanism is used to effectively separate the receiving signals.

[0015] The present invention adopts a concave rotating shaft design TDM-MIMO solid-state monitoring unit. The elevation angle of the radar unit antenna can be determined according to the slope angle of the slope. At the same time, the radar body can adjust the elevation angle of the central antenna through the front and rear hydraulic supports, and adjust the optimal field of view through the rotating platform and the horizontal traditional axis. The design monitoring unit adopts the TDM method to achieve signal separation, which can ensure that the receiving and transmitting signals of the three sets of devices do not affect each other. The present invention designs an intelligent miniaturized corner reflector suitable for use in the slope of high-cold open-pit mines in conjunction with ground-based SAR, which can more conveniently receive radar signals from different angles. A triangular pyramidal magnesium-aluminum plate is used as the cross section, and the magnesium-aluminum plate is lighter and has better reflectivity. The present invention sets one of the chips inside the module as the main chip, and the other chips are slave chips. The main chip is responsible for generating a synchronization signal to control the transmission and stop of the FMCW signal, and uses a crystal oscillator to generate a clock signal and share it with each slave chip to ensure that the cascade radar runs under a single clock source. The number of virtual array elements can be effectively increased by chip cascading, and the influence of instrument size and side lobes can be avoided. At the same time, dual-frequency antenna array integration is adopted, which can increase the number of antenna units and the frequency band utilization efficiency without changing the antenna volume. This module design adopts dual-polarized microstrip antenna, which has the advantages of frequency reuse, polarization diversity, integrated transmission and reception, polarization agility, low profile and small size. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0017] Figure 1 This is a schematic diagram of the structure of a TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to an embodiment of the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of a TDM-MIMO solid-state monitoring unit;

[0019] Figure 3 Schematic diagram of the working principle of the TDM-MIMO solid-state monitoring unit. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1:

[0023] like Figure 1 , 2 As shown in FIG. 3 , an embodiment of the present invention provides a TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system, including: a TDM-MIMO solid-state monitoring unit and an intelligent corner reflection system.

[0024] The TDM-MIMO solid-state monitoring unit includes: three independent antenna arrays, hydraulic support, horizontal sliding base and control display unit; independent antenna arrays include: MIMO antenna array, dual-frequency antenna array, full polarization antenna array. The intelligent corner reflection system includes: three mutually perpendicular metal plates, a fixed bracket and a central control adjustment unit. It can be modulated into a non-linear signal transceiver through the transfer axis. The angle setting can help the three-dimensional high-precision solution of the one-dimensional line-of-sight displacement data of the slope; in addition, the MIMO antenna array transceiver integrated circuit board is used, and a total of 27 transmission channels and 36 receiving channels are configured through cascading to improve the imaging resolution; and the time division multiplexing mechanism is used to effectively separate the receiving signal, reduce interference, and ensure the imaging quality.

[0025] Furthermore, the TDM-MIMO solid-state monitoring unit adopts a concave shaft design, which is integrated by three sets of independent transmitting and receiving antenna array devices on the left, middle and right. However, the three sets of antennas share a set of main control units (i.e., a common transmitter, power amplifier, receiver and signal processor), and the theoretical setting range of the rotation angle of the connecting shafts at both ends is 0 to 180°. The elevation angle of the radar unit can be determined according to the slope angle of the slope, and the radar antennas at the left and right ends have different elevation angles from the center antenna to ensure the difference in radar geometric structure. The radar body can also adjust the elevation angle of the center antenna through the cooperation of the front and rear hydraulic supports, and adjust the optimal field of view through the rotating platform and the horizontal transmission shaft.

[0026] In order to upgrade the traditional one-dimensional slope line of sight solution to a three-dimensional high-precision slope direction solution, the module is designed as follows:

[0027] The TDM-MIMO solid-state monitoring unit uses the TDM method to achieve signal separation to ensure that the receiving and transmitting signals of the three sets of devices do not affect each other. TDM is the simplest and most widely used method to separate signals from multiple transmitting antennas. It performs a two-dimensional (range-Doppler) Fast Fourier Transform (Fast Fourier Transform, FFT) on each transmit-receive pair, and each two-dimensional FFT corresponds to a virtual antenna. Then, an incoherent summation is performed to create a pre-detection matrix and identify the peaks corresponding to valid targets in the matrix. For each valid object, an angular FFT is performed on the corresponding peaks of these multiple two-dimensional FFTs to identify the signal arrival angle of the object. Finally, the three-dimensional deformation field of the slope landslide can be solved according to the following formula based on the ground-based radar design parameters and the deformation measurement results in the line of sight.

[0028]

[0029] Among them, d S d U and d V are the three-dimensional deformations of the slope along the slope direction, the slope normal direction and the slope perpendicular direction respectively; α i (i=1,2,3) represents different radar sensor elevation angles; θ represents the slope angle; It represents the deformation monitoring results of different radar units in the line of sight. γ can be determined by the distance from the slope center to the radar body and from the observation target to the radar body.

[0030] ①MIMO antenna array: MIMO antenna array is about the number of transceiver channels and the chip cascade design, which directly affects the azimuth resolution of ground-based equipment. Radar azimuth resolution refers to the ability of radar to distinguish two adjacent targets in azimuth. For MIMO ground-based equipment, the azimuth resolution Δθ is directly reflected as the 3dB beam width of the main lobe of the array antenna pattern, which can be approximately expressed as:

[0031]

[0032] Among them, D V is the distance between adjacent virtual array elements, i.e., the receiving channel spacing; N V is the number of virtual array elements; N T 、N R Respectively represent the number of transmitting and receiving channels. Receiving channel spacing D V It is usually set to λ / 2, so the radar azimuth resolution Δθ is only related to the number of virtual array elements N. V Theoretically, the number of virtual array elements N V The greater the number, the higher the directional resolution of the ground-based SAR. However, setting more transmitting and receiving array elements will increase the size of the instrument to a certain extent. Although the size problem can be solved by reducing the spacing between the transmitting and receiving array elements, too small a spacing will produce strong crosstalk between the transmitting and receiving elements, making the crosstalk signal strength much greater than the echo signal strength, resulting in a sidelobe effect, thus reducing the imaging quality. Based on this, the project plans to use a single chip with 3 transmitting channels and 4 receiving channels as the basis, integrating a total of 27 transmitting channels and 36 receiving channels, with a theoretical azimuth resolution of 0.1045°, or 1.8 mrad (1 km).

[0033] In order to integrate the above-mentioned multiple transceiver channels, increase the virtual aperture, and ensure high azimuth resolution, it is necessary to reasonably design a cascade solution for single-chip with few transceiver channels. The project plans to set one of the chips inside the module as the master chip and the other chips as slave chips. The master chip is responsible for transmitting X and Ku band signals. Its internal signal synthesizer generates FMCW signals and transmits them to all slave chips. Each slave chip multiplies the transmit signal of the master chip and finally generates a multi-frequency FMCW signal. The band signal generated by the slave chip is separated into multiple signals by a splitter, and then fed to all master and slave chips themselves. By laying out feeders of the same length, the delay of all band signals during transmission is the same, so that the initial phase of the signal is consistent. In addition, the master chip is responsible for generating synchronization signals to control the transmission and stop of FMCW signals, using crystal oscillators to generate clock signals and share them with each slave chip to ensure that the cascade radar operates under a single clock source. Chip cascading can effectively increase the number of virtual array elements and avoid the influence of instrument size and side lobes.

[0034] ②Dual-frequency antenna array: The dual-frequency antenna array is a microstrip patch dual-frequency antenna design. The dual-band antenna can increase the number of antenna units and the frequency band utilization efficiency without changing the antenna volume. The range resolution is positively correlated with the signal bandwidth. The shortwave has a larger instantaneous bandwidth and is suitable for fine target imaging and high-precision deformation monitoring. Compared with shortwave, the longwave has a wider beam and stronger penetration than shortwave, which is more advantageous in soil water inversion.

[0035] The range resolution can be calculated by the following formula:

[0036]

[0037] Among them, C is the propagation speed of electromagnetic waves. From this equation, it can be concluded that the range resolution is only related to the signal bandwidth B, that is, the wider the signal bandwidth, the smaller the value of the range resolution, and the greater the resolution.

[0038] Theoretically, the basic feature of a dual-band microstrip antenna is that when the same antenna works in two different frequency bands, its impedance characteristics and radiation characteristics are consistent, but these characteristics are obtained in the same planar structure. This module design adopts a multi-layer structure method to stack dielectric plates to produce orthogonally polarized sub-elements, which can obtain higher isolation than dual-band polarization elements of the same polarization. Different sizes of antenna patches are printed on each layer of dielectric plates to form different resonators. The thickness of the dielectric plate has a great influence on the antenna, and has an impact on the antenna bandwidth, radiation power and mechanical strength. The thicker the dielectric substrate, the larger the antenna bandwidth, the higher the radiation power, and the greater the mechanical strength. However, the increase in thickness will also increase the dielectric loss and surface wave loss. For the selection of antenna patch size, from the perspective of dual polarization realization, the central symmetric patch can minimize the impact of asymmetry on the antenna radiation performance and has better cross-polarization performance. From the perspective of antenna bandwidth performance, under the same conditions, the larger the effective area of ​​the patch, the wider the bandwidth. Each patch is coupled and fed by a driving patch. This is a feeding method in which the microstrip feed line and the microstrip patch are in different planes or in the same plane but do not contact each other, which facilitates orthogonal polarization or co-polarization of two frequency bands and easily achieves a wider working bandwidth at two working frequencies.

[0039] ③Fully polarized antenna array: The fully polarized MIMO antenna array is to rationalize the antenna array configuration and polarization mode. The multi-input multi-output ground-based SAR obtains M×N non-overlapping array elements from M+N actual transmitting and receiving array elements during one equivalent transmission and reception period. In order to obtain the maximum sampling freedom, M and N should be as close or equal as possible. In addition, the required equivalent virtual array length is determined by the observation scene range. The radar operating frequency uses the X and Ku bands. The radar body is designed to adopt an alternating transmission mode. There is only one transmitting array element transmitting a signal in each pulse repetition period, and all receiving array elements receive the scene echo synchronously. After all transmitting array elements transmit signals in turn, a uniform equivalent virtual array with equal array element spacing can be obtained. The microwave band transmission and scattering characteristics are affected by the soil dielectric constant, and there is a significant correlation between soil water and dielectric constant. This module design uses a dual-polarized microstrip antenna, which has the advantages of frequency reuse, polarization diversity, integrated transmission and reception, polarization agility, low profile and small size. Theoretically, any centrosymmetric microstrip patch antenna can achieve dual-polarization operation, but in actual engineering applications, to simplify the design, the patch style is generally square or circular. Therefore, the array element uses a rectangular microstrip patch, and the adjacent vertical edges of the patch are fed to achieve dual polarization, that is, a microstrip coplanar fed patch antenna array, which can obtain better radiation performance, and each polarization feeding network realizes equal amplitude and in-phase feeding at the output port. Both H polarization and V polarization can achieve a wider impedance bandwidth.

[0040] As an implementation method of an embodiment of the present invention, the key to the integrated technology of intelligent adaptation of the direction of the corner reflector and atmospheric disturbance correction is the production of the corner reflector and the compensation of atmospheric disturbance. The corner reflector has strong directivity. In order to achieve the best reflection effect of the microwave signal emitted by the ground-based equipment, the antenna must be accurately aimed. When the radar electromagnetic wave scans the corner reflector, a strong echo signal will be generated on the radar screen, but most general reflectors are fixed in design and cannot adjust its position and angle. In this module, the process of high-precision three-dimensional deformation monitoring of the slope is adapted to the concave rotating shaft TDM-MIMO solid-state foundation device. At the same time, considering that the azimuth and elevation angles still need to be fine-tuned in the later stage, an intelligent miniaturized corner reflector suitable for the slope of the high-cold open-pit mine is specially developed for use with the ground-based SAR. The corner reflector bracket is designed to automatically adjust within the range of 90° horizontally and 15° vertically, which can more conveniently receive radar signals from different angles. This design uses a triangular pyramidal magnesium-aluminum plate as the cross-section, which is lighter and has better reflectivity. Corner reflectors can maintain a stable position for a long time and have high coherence. At present, conventional corner reflectors are mainly used for radiation calibration and geometric correction of space-borne SAR. Ground-based synthetic aperture radar can further improve its accuracy by matching corner reflectors on the basis of making up for the disadvantages of space-borne SAR. The biggest problem in this process is that the microwave signal emitted by the ground radar is easily affected by atmospheric factors such as humidity, temperature, and air pressure. Therefore, in this design, the corner reflector is equipped with a digital display monitor of atmospheric dry temperature, dry air pressure and relative humidity. The influence of atmospheric disturbance in the observation area is analyzed by the change of its interference phase, and then the disturbance error is compensated.

[0041] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system, characterized in that: include: TDM-MIMO solid-state monitoring unit and intelligent corner reflection system; TDM-MIMO solid-state monitoring unit includes: MIMO antenna array, dual-frequency antenna array, full-polarization antenna array; TDM-MIMO solid-state monitoring unit is used for high-precision three-dimensional solution of slope aspect, and the intelligent corner reflection system is used for fine-tuning the azimuth and elevation directions during high-precision three-dimensional deformation monitoring of the slope.

2. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 1, characterized in that: The TDM-MIMO solid-state monitoring unit adopts a concave shaft design and is integrated with three sets of independent transmitting and receiving antenna array devices on the left, middle and right. The three sets of antennas share one main control unit.

3. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 2, characterized in that: The TDM-MIMO solid-state monitoring unit uses the TDM method to achieve signal separation. First, a range-Doppler fast Fourier transform is performed on each transmit-receive pair. Each two-dimensional FFT corresponds to a virtual antenna. Then, a non-coherent summation is performed to create a pre-detection matrix, and the peaks corresponding to valid targets in the matrix are identified. For each valid object, angular FFT is performed on multiple 2D FFT corresponding peaks to identify the signal arrival angle of the object. Finally, the 3D deformation field of the slope landslide is calculated according to the design parameters of the ground-based radar and the deformation measurement results in the line of sight.

4. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 3, characterized in that: The calculation formula of the three-dimensional deformation field of the slope landslide is: Among them, d S ,d U and d V are the three-dimensional deformations of the slope along the slope direction, the slope normal direction and the slope perpendicular direction respectively; α i (i=1,2,3) represents different radar sensor elevation angles; θ represents the slope angle; It represents the deformation monitoring results of different radar units in the line of sight. γ can be determined by the distance from the slope center to the radar body and from the observation target to the radar body.

5. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 4, characterized in that: The corner reflector bracket of the intelligent corner reflection system is automatically adjusted within the range of 90° horizontally and 15° vertically.

6. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 5, characterized in that: The intelligent corner reflection system uses a triangular pyramidal magnesium-aluminum plate as the cross section.

7. The TDM-MIMO solid-state slope three-dimensional high-resolution foundation monitoring system according to claim 6, characterized in that: The TDM-MIMO solid-state monitoring unit is configured with 27 transmission channels and 36 receiving channels through a cascade design, and uses a time division multiplexing mechanism to effectively separate the receiving signals.

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