Near-field bp imaging method based on antenna pattern gain compensation

Abstract

This invention belongs to the field of radar imaging technology, specifically relating to a near-field BP imaging method based on antenna pattern gain compensation. The specific process is as follows: Step 1, measure the actual antenna pattern under anechoic conditions; Step 2, calculate the pixel value of any point in the imaging area based on the BP imaging method; Step 3, calculate the angle between any pixel in the imaging area and the transmitting and receiving antennas; Step 4, based on the measured antenna pattern and the angle between the antenna and the pixel, calculate the actual gain obtained from radar echoes from different directions in each channel, i.e., the actual gain obtained by the transmitting and receiving antennas; Step 5: Construct a gain compensation matrix using the actual gains obtained by each transmitting and receiving antenna, and use the gain compensation matrix to compensate for each pixel in the imaging area.

Description

Technical Field

[0001] This invention belongs to the field of radar imaging technology, specifically relating to a near-field BP imaging method based on antenna pattern gain compensation. Background Technology

[0002] The integration of Multiple-Input Multiple-Output (MIMO) technology with radar systems has resulted in a novel type of MIMO radar system. This system offers greater design freedom and potentially superior performance, exhibiting significant advantages over traditional monostation radar systems, thus becoming a research hotspot in the radar field. Firstly, MIMO radar systems offer flexible and diverse array structure designs, enhancing the system's data acquisition capabilities in complex environments and improving multi-target detection capabilities and operational efficiency. Secondly, MIMO radar systems reduce the design requirements for antenna gain and directivity, thereby saving costs.

[0003] For MIMO radar systems, the transmitting antenna array synthesizes the transmitting antenna pattern, and the receiving antenna array synthesizes the receiving antenna pattern. When the radar system is operating, at the transmitting end, electromagnetic waves are concentrated and radiated by the transmitting antenna. The specific transmission gain can be obtained from the transmitting antenna pattern function. After being reflected by the target, the waves are received by the receiving antenna, and similarly, the receiving gain can be obtained from the receiving antenna pattern function. However, it is worth noting that when the detection scenario involves multiple targets, the azimuth of each target relative to the transmitting and receiving antenna arrays is not consistent. Consequently, the received transmission and receiving gains are also inconsistent. This results in varying echo signal energy for targets at the same range but different azimuths. Against the background of a target echo with strong energy, the echo of a weak target is masked and cannot be detected. This problem is caused by the directivity of the antenna pattern.

[0004] Traditional phased array radar technology controls the direction of the synthesized beam by controlling the phase of each array element. Given the prior knowledge of the target's location, the main lobe of the synthesized beam is directed towards that target. When multiple targets are present, phase shifters are used to change the beam's direction, achieving multi-target detection through beam scanning. MIMO radar, combined with phased array technology, leverages the principles of digital beamforming. Through complex signal processing algorithms, it assigns different phases to each array element multiple times, achieving directional control of the synthesized signal—the resulting "beam." This allows for the real-time formation of multiple beams with different directions, enabling multi-target detection without beam scanning. Both of these multi-target detection methods start from the phase of the array element signals, controlling the main lobe of one or more synthesized beams to point towards each target. However, neither of these methods can meet real-time requirements. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a near-field BP imaging method based on antenna pattern function gain compensation. This method can significantly enhance the energy of targets at large angles and effectively achieve real-time detection in multi-target scenarios.

[0006] The technical solution for implementing the present invention is as follows:

[0007] A near-field BP imaging method based on antenna pattern gain compensation, the specific process of which is as follows:

[0008] Step 1: Measure the actual radiation pattern of the antenna under anechoic conditions;

[0009] Step 2: Calculate the pixel value of any point in the imaging area based on the BP imaging method;

[0010] Step 3: Calculate the angle between any pixel within the imaging area and the transceiver antenna;

[0011] Step 4: Based on the measured antenna pattern and the angle between the antenna and the pixel, calculate the actual gain obtained by the radar echo from different directions in each channel, that is, the actual gain obtained by the transmitting and receiving antennas.

[0012] Step 5: Construct a gain compensation matrix using the actual gains obtained from each transceiver antenna, and use the gain compensation matrix to compensate for each pixel in the imaging area.

[0013] Furthermore, in step two of this invention, the pixel value of any point in the imaging region is calculated based on the BP imaging method:

[0014]

[0015]

[0016] Where M and N represent the number of transmitting and receiving antennas, respectively, s(t) represents the transmitted signal, and G... t(q，m) G r(q，n) α(x) represents the gain of the transmitting antenna and the receiving antenna at pixel q, respectively. q R represents the reflection coefficient. tq R rq τ represents the distance between any pixel q and both the transmitting and receiving antennas. mnq This indicates the echo delay.

[0017] Furthermore, the calculation of the third angle in step three of this invention is as follows:

[0018] Assume the coordinates of any point q within the imaging region are (x... q y qIf the angle θ1 between the point and the transmitting antenna and the angle θ2 between the point and the receiving antenna can be expressed as:

[0019]

[0020]

[0021] Among them, (x t，m y t，m (x) represents the coordinates of the transmitting antenna. r，n y r，n () represents the coordinates of the receiving antenna.

[0022] Furthermore, the compensation for each pixel q in the imaging region described in this invention is as follows:

[0023]

[0024]

[0025]

[0026] Where m = 1, 2, ..., M, n = 1, 2, ..., N.

[0027] Beneficial effects:

[0028] This invention is applied to real-time detection in multi-target scenarios. Due to the directionality of the antenna, for large-angle targets, the angle between the target and the transmitting and receiving antenna is outside the beamwidth, resulting in relatively small gain. In multi-target scenarios, the echo energy will be significantly weaker than that of small-angle targets, making it easy to be masked during imaging. This invention compensates for radar data from different directions, effectively enhancing the energy of large-angle targets in multi-target scenarios, thus significantly increasing the energy of large-angle targets and effectively achieving real-time detection in multi-target scenarios. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is the through-wall radar system used in the experimental verification of this invention;

[0031] Figure 2 This is the antenna pattern function measured during the experimental verification of this invention;

[0032] Figure 3This is a diagram illustrating the BP imaging algorithm considering the antenna pattern involved in this invention.

[0033] Figure 4 This is the static target experimental scenario used in the experimental verification of this invention;

[0034] Figure 5 This is the result of static target experiments during the experimental verification of this invention;

[0035] Figure 6 This is the experimental scenario of the moving target during the experimental verification of this invention;

[0036] Figure 7 This is the result of the moving target experiment during the experimental verification of this invention. Detailed Implementation

[0037] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0038] It should be noted that, in the absence of conflict, the following embodiments and features can be combined with each other; and, based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0039] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0040] The design concept of this invention is as follows: Addressing the issue of weak energy of large-angle targets in multi-target scenarios, firstly, after analyzing the antenna pattern configuration in the near-field condition, the antenna pattern function is measured under anechoic conditions; secondly, the gain obtained from radar echoes from different directions in each channel is determined, and then the gain to be compensated is determined based on the difference between the gain in the maximum direction and the gains in other directions; finally, a gain compensation matrix is ​​constructed using digital beamforming technology to compensate for radar data in different directions, thereby effectively enhancing the energy of large-angle targets in multi-target scenarios.

[0041] This application provides a near-field BP imaging method based on antenna pattern function gain compensation, which is implemented through the following steps:

[0042] Step 1: Measure the actual radiation pattern of the antenna under anechoic conditions;

[0043] Figure 1 The image shows the MIMO radar array used in this invention. Figure 2 The antenna radiation patterns at multiple frequencies were measured under anechoic conditions.

[0044] Step 2: Calculate the pixel value at any point q within the imaging region based on the BP imaging method;

[0045] like Figure 3 As shown, using the BP algorithm, the pixel value at any point q within the imaging region can be expressed as:

[0046]

[0047]

[0048] Where M and N represent the number of transmitting and receiving antennas, respectively, s(t) represents the transmitted signal, and G... t(q，m) G r(q，n) α(x) represents the gain of the transmitting antenna and the receiving antenna at pixel q, respectively. q R represents the reflection coefficient. tq R rq τ represents the distance between any pixel q and both the transmitting and receiving antennas. mnq This indicates the echo delay.

[0049] In this step, G t(q，m) With G r(q，n) Since these are unknown parameters, they need to be calculated based on the radiation pattern and the angle between the pixel and the transmitting / receiving antenna.

[0050] Step 3: Calculate the angle between any point within the imaging area and the transceiver antenna;

[0051] Assume the coordinates of any point q within the imaging region are (x... q y q If the angle θ1 between the point and the transmitting antenna and the angle θ2 between the point and the receiving antenna can be expressed as:

[0052]

[0053]

[0054] Among them, (x t，m y t，m (x) represents the coordinates of the transmitting antenna. r，n y r，n () represents the coordinates of the receiving antenna.

[0055] Step 4: Based on the measured antenna pattern and the angle between the antenna and the pixel, calculate the actual gain obtained by the radar echo from different directions in each channel, that is, the actual gain obtained by the transmitting and receiving antennas.

[0056] In this step, the antenna pattern function can be obtained from the antenna pattern. Then, the angle value calculated in step four can be substituted into the antenna pattern function. Therefore, the actual gain obtained by the transmitting and receiving antennas can be calculated for each pixel in the image.

[0057] Step 5: Construct a gain compensation matrix using the actual gains obtained from each transmitting and receiving antenna, and use the gain compensation matrix to compensate for each pixel in the imaging area, thereby achieving compensation of radar echo data.

[0058] Calculate the gain to be compensated for each pixel in each channel and compensate it to the actual pixel value I. q superior:

[0059]

[0060]

[0061]

[0062] This completes the near-field BP imaging algorithm based on antenna pattern function for gain compensation, achieving energy enhancement for large-angle targets in multi-target scenarios.

[0063] Example:

[0064] To verify the effectiveness of the near-field BP imaging algorithm based on antenna pattern function gain compensation proposed in this invention, static target experiments and moving target experiments were designed and analyzed. The static target experiment scenario is as follows: Figure 4 As shown, the same angular target was placed at positions of 0°, -30°, -45°, -60°, and -80°. To compare the imaging effects of multi-target scenes before and after compensation, the data from the five experiments were combined for imaging. The results before and after compensation are shown below. Figure 5 As shown.

[0065] analyze Figure 5The experimental results show that before compensation, small-angle targets are clearly visible, but the two large-angle targets at -60° and -80° are almost invisible. This indicates that the gain of the large-angle targets is relatively small, and their energy is significantly lower than that of the other three small-angle targets, thus they are masked in the imaging results. Analysis of the compensated imaging results shows that after compensation, the energy of the two large-angle targets at -60° and -80° is enhanced, comparable to the reflected echo energy of the other three targets, and all five targets are clearly visible. Therefore, this demonstrates that the proposed gain compensation algorithm based on antenna pattern function has a significant enhancement effect on the energy of large-angle targets in multi-target scenes.

[0066] conduct Figure 6 The moving target experiment shown depicts two targets undergoing uniform circular motion. Their trajectories relative to the antenna array are -90°→0°→-90° and 0°→90°→0°, respectively. As shown in the figure, when one moving target has a larger angle relative to the antenna main lobe beam and the other target has a smaller angle, a frame from the experimental data is selected for imaging. The imaging results before and after compensation are shown below. Figure 7 As shown in the figure. The analysis results show that the energy of targets at large angles is weak and easily confused with clutter. After compensation, the energy of targets at large angles is enhanced, and the energies of the two moving targets are similar. Therefore, this invention has a significant effect on the real-time detection of moving targets.

[0067] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A near-field BP imaging method based on antenna pattern gain compensation, characterized in that, The specific process is as follows: Step 1: Measure the actual radiation pattern of the antenna under anechoic conditions; Step 2: Calculate the pixel value of any point in the imaging area based on the BP imaging method; Step 3: Calculate the angle between any pixel within the imaging area and the transceiver antenna; Step 4: Based on the measured antenna pattern and the angle between the antenna and the pixel, calculate the actual gain obtained by the radar echo from different directions in each channel, that is, the actual gain obtained by the transmitting and receiving antennas. Step 5: Construct a gain compensation matrix using the actual gains obtained from each transceiver antenna, and use the gain compensation matrix to compensate for each pixel in the imaging area; The pixel value of any point in the imaging region is calculated based on the BP imaging method: in, and These represent the number of transmitting antennas and receiving antennas, respectively. Indicates the transmission of a signal. These represent the transmitting and receiving antennas at the pixel level, respectively. Gain at that point, Represents the reflection coefficient. , Represents any pixel The distance between the transmitting antenna and the receiving antenna. Indicates echo delay; Each pixel in the imaging region The compensation will be as follows: in, =1,2,…… , =1,2,…… .

2. The near-field BP imaging method based on antenna pattern gain compensation according to claim 1, characterized in that, The angle calculation in step three is as follows: Assuming any point within the imaging region The coordinates are Then the angle between that point and the transmitting antenna and the angle between that point and the receiving antenna. It can be represented as: in, Represents the coordinates of the transmitting antenna. Represents the coordinates of the receiving antenna.

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