Space grid based distributed coherent radar beam characterization method

Abstract

The application provides a kind of distributed phase correlation radar beam characterization method based on space grid, comprising: according to the array configuration of distributed phase correlation radar, the gradient of the change of beam shape with spatial position is calculated;Wherein, distributed phase correlation radar is composed of multiple unit radars deployed in space dispersion, and array configuration is used to describe the layout of multiple unit radars deployed in dispersion;Based on the change gradient, the adaptive grid is divided in the detection space;In each space grid after division, the energy gain of the synthetic beam formed by each unit radar is calculated respectively;The energy gain of the synthetic beam is mapped to the corresponding space grid to realize the characterization of the beam shape of distributed phase correlation radar.The application divides the detection area by introducing adaptive space grid, realizes the efficient characterization of beam shape, significantly reduces the calculation complexity, and improves the processing efficiency.

Description

Technical Field

[0001] This application relates to the field of radar technology. Specifically, this application relates to a distributed coherent radar beam characterization method based on spatial grids and a distributed coherent radar using this method. Background Technology

[0002] In recent years, aerial moving targets have exhibited various characteristics such as being "low, slow, small, stealthy, mobile, and fast," posing new challenges to radar detection capabilities, modes, and functions. The most direct method to meet target detection requirements is to increase the aperture and power of individual radars, but this leads to problems such as poor maneuverability, high manufacturing costs, and difficulties in later maintenance. To overcome the increasingly apparent performance bottlenecks of single radars, Distributed Coherent Aperture Radar (DCAR) has emerged. This technology coherently synthesizes transmitted and received signals, effectively combining several dispersed radar units into a single, higher-power, and higher-gain virtual radar. It offers advantages such as increased information, wider coverage, enhanced damage resistance, and reduced costs, making it an important direction for future radar development.

[0003] Currently, the academic community has conducted extensive and in-depth research on the factors affecting the coherent performance of distributed coherent radar systems, covering performance gain boundaries, coherent parameter estimation methods, and spatial deployment constraints. Regarding the study of the spatial distribution of the synthetic beam in distributed coherent radar, existing literature has defined coherent depth of field to describe the spatial distribution of the synthetic energy in distributed coherent radar.

[0004] However, existing technologies still face some challenges in characterizing the spatial beam geometry of distributed coherent radar, especially the point coordinate-based calculation method, which suffers from high computational complexity and low processing efficiency. Summary of the Invention

[0005] Therefore, it is necessary to provide a distributed coherent radar beam characterization method based on spatial grids to address the aforementioned technical problems.

[0006] In a first aspect, this application provides a distributed coherent radar beam characterization method based on spatial grids, including: Based on the array configuration of the distributed coherent radar, the gradient of beam shape variation with spatial location is calculated; wherein, the distributed coherent radar consists of multiple spatially dispersed unit radars, and the array configuration is used to describe the layout of the multiple spatially dispersed unit radars. Based on the changing gradient, the probe space is adaptively meshed; Within each of the partitioned spatial grids, the energy gain of the synthetic beam formed by the coordinated action of each unit radar is calculated. The energy gain of the synthesized beam is mapped to the corresponding spatial grid to characterize the distributed coherent radar beam pattern.

[0007] In one embodiment, the array configuration includes the number of unit radars; the variation gradient is the variation gradient of the synthetic beam energy gain; The calculation of the beamform variation gradient with spatial location based on the array configuration of the distributed coherent radar specifically includes: When the number of unit radars in the distributed coherent radar is 2, the energy gain of the synthetic beam is calculated according to expression (13); (13) in, Indicates the synthesized beam energy gain. This represents the difference between the distance from a point in space to the first radar cell and the distance to the second radar cell. , Indicates wavelength; Differentiating the expression formula (13) yields the gradient of the change in the energy gain of the synthesized beam; (14) in, This represents the gradient of the change in the energy gain of the synthesized beam.

[0008] In one embodiment, the adaptive mesh partitioning of the probe space based on the changing gradient specifically includes: When the gradient of change is less than a preset threshold, a single spatial grid is used to divide the corresponding region.

[0009] In one embodiment, calculating the gradient of beamform variation with spatial location based on the array configuration of the distributed coherent radar further includes: When the number of unit radars of the distributed coherent radar exceeds 2, the gradient of the change in the synthetic beam energy gain is calculated by numerical simulation.

[0010] In one embodiment, the synthesized beam energy gain is the transmit coherent efficiency; the expression (13) is obtained as follows: The ratio of the actual synthesized beam energy to the ideal synthesized beam energy is calculated, and the expression for the transmission coherent efficiency is obtained (8): (8) in, Indicates taking the conjugate; Indicates the signal duration, and the transmit coherent efficiency satisfies And under ideal correction conditions, The value is 1; Approximate expression (8) to expression (9): (9) in, Indicates the first Individual radar units Indicates the first Individual radar units Indicates the number of radar units. , ; If the distributed coherent radar transmits a narrowband signal, then expression (9) is further simplified to expression (10): (10) in, Represents the distance from a point in space to the nth The distance of the first radar unit and the distance to the second radar unit The difference in distance between individual radar units; The number of unit radars in a distributed coherent radar N Substitute 2 into expression (10) to obtain expression (13).

[0011] In one embodiment, the expression (8) is obtained as follows: Get the The expression for the transmitted signal of a single-unit radar (1): (1) in, Indicates the first Each unit radar in time The transmitted signal, , , and They represent the first The amplitude error, carrier frequency error, time error, and phase error of each radar unit. Indicates baseband signal, This represents the ideal carrier frequency for the transmitted signal; Set a space to synthesize a point The coordinates are Based on expression (1), the transmitted signals of each unit radar are in The synthesized signal at that point is: (2) in, This represents the complex gain resulting from different transmission paths. Indicates the first The transmitted signals from each radar unit reach the target point. Time delay at the location; In a distributed coherent radar system, a reference radar is selected, and the remaining element radars are corrected based on the reference radar. The expression for the transmission coherent parameters is as follows: (3) After obtaining the estimated values ​​of the transmission coherence parameters, each radar unit corrects the transmission parameters based on these estimated values. The corrected synthesized signal at point is represented as: (4) in, This represents the estimated value of the launch time coherent parameter. This represents the estimated value of the transmit phase coherent parameters; When the coherent parameters are perfectly estimated The ideal synthesized signal at point is represented as: (5) Ignoring the initial phase and time delay, expression (5) is further expressed as: (6) At any point in space At the location, according to expression (7), calculate The actual synthesized signal at that location: (7) in, express The actual synthesized signal at the location; Based on expressions (6) and (7), the ratio of the actual synthesized beam energy to the ideal synthesized beam energy is calculated, and the expression (8) for the transmission coherent efficiency is obtained.

[0012] In one embodiment, the mesh partitioning rules include: Based on the existing GeoSOT 32-level mesh, the mesh is further subdivided into 3 levels according to the principle of quad-branch partitioning, adding three finer-grained mesh levels, bringing the total number of levels to 35. The mesh accuracies corresponding to the three finer-grained mesh levels are (1 / 8192)″ (0.375cm), (1 / 32768)″ (0.094cm), and (1 / 131072)″ (0.023cm), respectively.

[0013] In one embodiment, it further includes: The corrected Manhattan distance between two spatial grids is expressed as follows: (11) in, This indicates a correction for the Manhattan distance. This represents the distance between two points in this dimension. It represents the angle between two points with the equator as the reference.

[0014] In one embodiment, .

[0015] Secondly, this application provides a distributed coherent radar that uses a spatial grid-based distributed coherent radar beam characterization method as described in any of the above embodiments.

[0016] The aforementioned distributed coherent radar beam characterization method based on spatial grids, and the distributed coherent radar applying this method, achieves efficient beam morphology characterization by introducing an adaptive spatial grid to divide the detection area. Compared to traditional point-by-point calculation and rendering methods, this method performs synthetic beam gain calculation only once within each grid cell and performs unified characterization on a grid-by-grid basis, significantly reducing computational complexity and improving processing efficiency. Simultaneously, since the beam morphology is presented in a discretized grid format, it effectively reduces the amount of data required for graphics rendering, saving display resources. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating a distributed coherent radar beam characterization method based on spatial grids in one embodiment. Figure 2 This is a schematic diagram of the distributed radar coherent synthesis principle in one embodiment; Figure 3 This is a graph showing the relationship between the maximum change gradient of the synthesized beam energy and the phase difference in one embodiment of a distributed radar system. Figure 4 This is a schematic diagram of adaptive grid level selection in one embodiment; Figure 5 This is a schematic diagram illustrating the correction of the Manhattan distance in one embodiment; Figure 6 This is a spatial partition diagram of one embodiment; Figure 7 This represents the distance error between unit radars 1 and 2 in one embodiment; Figure 8 This represents the distance error between unit radars 1 and 3 in one embodiment; Figure 9 This is a comparison of distance calculation times in one embodiment; Figure 10 This is the overall appearance of the spatial beamform of a distributed coherent radar in one embodiment; Figure 11 This is a local detail of the spatial beamform of a distributed coherent radar in one embodiment. Detailed Implementation

[0018] 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.

[0019] In one embodiment, such as Figure 1 As shown, a distributed coherent radar beam characterization method based on spatial grids is provided. This method specifically includes the following steps: Step S10: Calculate the gradient of beam shape change with spatial position based on the array configuration of the distributed coherent radar.

[0020] Among them, the distributed coherent radar consists of multiple spatially dispersed unit radars, and the array configuration is used to describe the layout of the multiple dispersed unit radars.

[0021] Step S20: Based on the changing gradient, adaptively divide the probe space into grids.

[0022] Step S30: Calculate the energy gain of the composite beam formed by the coordinated action of each unit radar within each of the partitioned spatial grids.

[0023] Step S40: Map the synthetic beam energy gain to the corresponding spatial grid to characterize the distributed coherent radar beam morphology.

[0024] Specifically, without loss of generality, assume that the distributed coherent radar consists of... N The radar consists of several unit radars with simultaneous transmission and reception. n The transmitted signal of a single radar unit can be represented as: (1); In the formula, , , and They represent the first The amplitude, carrier frequency, timing, and phase errors in the transmitted signals of individual radar units are caused by inconsistencies in their internal hardware. Indicates baseband signal, Indicates the ideal carrier frequency for the transmitted signal. Indicates the signal transmission time. It represents the imaginary unit.

[0025] First, consider the case of the traditional Cartesian coordinate system. Establish a two-dimensional rectangular coordinate system with the location of the first unit radar as the origin, such as... Figure 2 As shown. Figure 2 middle Indicates the first Each unit radar reaches the point. The distance. Synthesizing a point in a given space. Coordinates are Then the radar signals transmitted by each unit are in The synthesized signal at that point is: (2) In the formula, The complex gain is due to the different transmission paths. Indicates the first The time delay of the transmitted signal from each unit radar to the target. As can be seen from equation (2), due to the internal synchronization error and external transmission path difference between different unit radars, the transmitted signals of multiple unit radars cannot be simultaneously superimposed in phase at the point of interest, resulting in a decrease in the synthesized gain of the radio frequency electric field illuminating the target. This phenomenon can also be called decoherentization of the transmitted signal. In order to achieve coherent synthesis of the transmitted signal, it is necessary to adjust the transmission parameters of each unit radar to achieve ideal signal superposition. Ideally, the amplitude, carrier frequency, time and phase need to be adjusted simultaneously. However, the amplitude and frequency of the transmitted signal are often determined by the hardware parameters of a single radar itself, and are usually not adjusted in real time. Corresponding measures should be taken in advance for calibration, while time and phase can be adjusted in real time in most existing radar systems. Therefore, this application focuses on the correction parameters of time and phase and defines them as transmission coherent parameters. Without loss of generality, it is assumed that the first unit radar is the reference radar, and the remaining unit radars are corrected based on this. The specific expression of the transmission coherent parameters is as follows: (3) After obtaining the estimated values ​​of the transmission coherent parameters, each radar unit corrects the transmission parameters based on the estimation results. The synthesized signal at point can be represented as: (4) in, These are estimated values ​​for the launch time coherent parameters. These are the estimated values ​​of the transmit phase coherent parameters. When the coherent parameters are perfectly estimated, i.e., there is no estimation error, and the transmission path difference is ignored, the ideal synthesized signal can be expressed as: (5) Ignoring the initial phase and time delay, equation (5) can be further expressed as: (6) At this moment, any point in space The synthesized signal at point can be represented as: (7) This application uses the concept of transmit coherent efficiency to quantitatively characterize the strength of the synthesized beam energy gain, thereby representing the spatial beam distribution pattern. The concept is the ratio of the actual synthesized beam energy to the ideal synthesized beam energy, and the specific expression is as follows: (8) In the formula Indicates taking the conjugate; This represents the signal duration. Clearly, the transmit coherent efficiency satisfies... And under ideal correction conditions, The value is 1.

[0026] According to the literature "Wang Yuanhao, Wang Hongqiang, Liu Xinghua, et al. Research on coherent efficiency and coherent depth of field of distributed coherent radar [J]. Systems Engineering and Electronics Technology, 2024, 46(05): 1573-1582", Equation (8) can be approximately expressed as: (9) in, , .

[0027] As shown in Equation (9), the spatial beamform is directly related to the time difference between the arrival of different unit radars at the synthesis position. If latitude and longitude coordinates or Cartesian coordinates are used to calculate the beamform of the region of interest, a point-by-point calculation method is required. In particular, when the region of interest includes the near-field region of the DCAR, the traditional method of characterizing the beamform based on angle is no longer applicable. It should be emphasized here that the DCAR can perform transmit coherent synthesis in the near field. The main reason for the decoherence of the echo is that there are significant differences in the observation angles of different unit radars towards the target. Preliminary research has been conducted on this issue at home and abroad. This application focuses on the transmit beamform and therefore will no longer distinguish between near-field and far-field cases.

[0028] Point-by-point computation is time-consuming and inefficient, and the trend of beamform variation differs across spatial regions, making it unsuitable for dynamic platform DCAR systems. Regional gridding is suitable for beamform description, and spatiotemporal grids already have well-established partitioning and encoding rules. By recording location data within the grid, the signal strength of the current grid can be directly calculated, thus improving representation efficiency by trading space for time.

[0029] The following section will introduce specific methods for spatial grid partitioning size design and beamform characterization.

[0030] Earth surface subdivision involves infinitely subdividing the Earth's surface, discretizing it into a geographic grid system composed of regular or irregular geometric units of different scales using a specific subdivision model. This results in multi-layered grids with similar shapes, seamless spatial non-overlapping surfaces, and continuous scale. When the grid is subdivided to a certain degree, it can simulate the Earth. The Earth surface grid model assigns an ordered location code to each subdivided grid, ensuring that each grid, from the Earth as large as it is on Earth to the centimeter level, has a unique code, serving as a unique identifier for a spatial region.

[0031] Building upon this foundation, three-dimensional partitioned meshes extend the Earth's surface into Earth's space, dividing the Earth's surface, interior, and outer space into a series of discretized three-dimensional volumes, forming a multi-layered, seamless, and non-overlapping set of three-dimensional space elements. Each partitioned volume element has a unique code. Temporal partitioning discretizes time into time segments of varying lengths, assigning each segment a unique code, resulting in seamless and non-overlapping time intervals. Current academic research on global partitioned meshes has made significant progress, including spherical cube meshes, yin-yang meshes, adaptive subdivision meshes, degenerate octree meshes, and... Geographical coordinate global subdivision grid with one-dimensional integer on two to n-th power (GeoSOT), etc.

[0032] The following section introduces the method for designing mesh partitioning dimensions: Based on the definition of spatial reference grids and their practical application requirements, this application designs the following three specific requirements for radar beam shape reference grid systems: (1) Uniqueness. For a given spatial region, the radar beam shape reference grid should have a unique representation, with no other identical or completely equivalent representation.

[0033] (2) Uniformity. The grid partitioning size rules should be applicable to distributed radars of different configurations within a given carrier frequency range, and should degenerate into a monostation radar when the number of unit radars is 1. The carrier frequency range is considered here because the spectrum range is quite wide, but some frequency bands, especially at higher frequencies, have exceeded the synchronization capability and are not suitable for long-range detection.

[0034] (3) Inclusivity. The radar beam shape reference grid should be inclusive of the traditional latitude and longitude standard grids at home and abroad, so that it can be easily applied to existing identification systems.

[0035] GeoSOT has been proven to meet the requirements of uniqueness and inclusivity. Therefore, this application adopts the subdivision basis of GeoSOT and combines it with the characteristics of radar beam morphology to carry out subsequent analysis of beam morphology characterization for the uniform design.

[0036] To ensure uniformity, the expression for the emission coherent efficiency is first revised. Further analysis is needed. Distributed coherent radars typically transmit narrowband signals, therefore the expression in equation (9) can be ignored. B The effect can be further simplified to the following equation (9): (10) In the formula, , Represents the distance from a point in space to the nth The distance of the first radar unit and the distance to the second radar unit The difference in distance between individual radar units.

[0037] As shown in Equation (10), the magnitude of the synthesized beam energy at a point in space is closely related to the relative position of the unit radar and that point, and the grid can conveniently and efficiently represent the position information. It should be noted that if the grid size is selected based on the wavelength of the transmitted signal, such as half a wavelength, one wavelength, two wavelengths, etc., the influence of the transmitted signal carrier frequency can be ignored. It is recommended to use a unified division method based on wavelength. However, at this time, it is difficult to meet the requirement of inclusiveness, that is, there is no correspondence with the existing latitude and longitude standard grid, which will increase the application difficulty. Therefore, this application still considers to prioritize the use of grids of existing sizes for matching, rather than redefining the grid subdivision size. To this end, this application designs a minimum subdivision level comparison table based on the wavelength range, as shown in Table 1. The selection basis of the minimum grid level is that the maximum gradient of the synthesized beam energy change does not exceed 10%. The simulation results show the relationship between the maximum gradient of the synthesized beam energy change and the phase difference of the distributed coherent radar as follows. Figure 3 As shown. From Figure 3 It can be seen that, under the proposed constraints, the phase difference change should not exceed 8.8°, and the corresponding mesh partitioning size should not be greater than approximately 1 / 16 of the wavelength of the corresponding frequency band. Based on this, Table 1 lists the wavelength range corresponding to typical radar operating frequency bands and the required minimum partitioning size, as well as the existing mesh adaptation situation.

[0038] Table 1. Mesh Subdivision Level Comparison Table As shown in Table 1, the minimum grid size of the existing GeoSOT is 32 levels, corresponding to a size of 1.5 cm, which is only suitable for scenarios with frequency bands below 1 GHz. As the frequency band increases, it is necessary to further refine the existing subdivision size. Combining the range of commonly used radar frequency bands, this application proposes an extended rule for radar beam morphology characterization based on the subdivision rules of GeoSOT to adapt to the subdivision requirements at the 10 mm level. The specific supplementary rule is as follows: based on the 32-level grid, it is further subdivided downwards by 3 levels according to the principle of quadrilateral division, bringing the total number of levels to 35, that is, adding three levels: (1 / 8192)″ (0.375 cm), (1 / 32768)″ (0.094 cm), and (1 / 131072)″ (0.023 cm). This extended subdivision rule is also applicable to the height level, but the subdivision of the height dimension is easily derived from the subdivision of the latitude and longitude dimensions, so this application focuses on the latitude and longitude dimensions.

[0039] In addition, it should be noted that due to the different areas of space, The changing trends are different, which means that it is not necessary to adopt a uniform grid size in the global space. Instead, an appropriate grid size should be selected according to the different slopes of the distance difference changes in the current region, thereby saving computational and storage resources and improving the representation effect. Figure 4 This is a schematic diagram of a grid-level adaptive selection.

[0040] As shown in equation (10), the spatial beam distribution pattern of distributed coherent radar is directly determined by the range difference. This application first analyzes the range calculation method based on spatial grids. Grid systems have a natural advantage in calculating Manhattan distances, but the spatial beam calculation of distributed coherent radar is concerned with the straight-line length. To utilize the advantage of spatial grids in efficiently calculating Manhattan distances, this application proposes a modified Manhattan distance to approximate the straight-line length. Given grid codes A and B respectively... and ,in, Indicates longitude. If latitude is used, then the corrected Manhattan distance between two grids can be expressed as follows: (11) in, This indicates a correction for the Manhattan distance. This represents the distance between two points in this dimension. It represents the angle between two points with the equator as the reference. (12) In this method, calculating the distance between two points requires only two addition steps, one division step, and two table lookup steps, avoiding square root calculations. Furthermore, the maximum calculation error in this method comes from the minimum grid edge length, such as... Figure 5 As shown in the figure and Let A and B represent the horizontal and vertical distances, respectively. It's easy to see that the maximum error is the diagonal length of the current grid. Based on the refined mesh size mentioned earlier, this error will not exceed the wavelength corresponding to the current transmit carrier frequency. .

[0041] Next, we consider the relationship between the gradient of beam shape change and spatial position, continuing with the transmit coherent efficiency. The gradient variation characterizes the beam shape change. Because The change is closely related to the distance difference, which in turn is closely related to the array configuration. Therefore, the gradient of change varies for different array configurations. Thus, to consider... The gradient variation should first determine the array configuration. First, consider the number of unit radars. N In the case where =2, at this time for (13) Taking its derivative, we get: (14) Given a gradient change threshold It is stipulated that when the gradient change range is less than a certain value, it can be represented by a grid. Let achievable (15) Given that points in space whose distance difference from two points is a certain value lie on a specific hyperbola, and the set of points whose distance difference is less than this certain value lies exactly on one side of the hyperbola. Furthermore, it should be noted that the solutions to the arcsine function have multiple values; that is, the intervals in which its values ​​satisfy the following formula all meet the condition. (16) in, This indicates the distance between the first and second radar units.

[0042] When the number of unit radars exceeds 2, the direct differentiation of equation (10) is difficult due to the presence of multiple variables, and the hyperbola overlap and intersection patterns are also more complex. In this case, the gradient change pattern should be pre-calculated using numerical simulation.

[0043] This application selects a two-dimensional scene for simulation experiments to analyze the advantages of using a spatial grid to characterize the spatial distribution of the synthetic beam of a distributed coherent radar. For ease of description, this application establishes a Cartesian coordinate system, using Cartesian coordinates as the traditional method for calculation and characterization. First, the derived corrected Manhattan distance approximation error is obtained through simulation to demonstrate its correctness. Then, by comparing the time required for spatial beam characterization under different methods, the advantages of the proposed spatial grid-based approach are illustrated. Finally, by directly providing distributed radar spatial beamform distribution diagrams under some typical radar configurations, the effectiveness of the proposed method can be intuitively observed.

[0044] First, the simulation parameters are set as shown in Table 2. Here, the second element radar is used as the origin for coordinate calculation. The radar and its corresponding partitioned space are then given as follows: Figure 6 As shown, displaying the data at a 6cm subdivision scale would be too close together. Figure 6 By merging 25 grids into one grid for display, the subdivision scale can be considered to be 3m.

[0045] Table 2 Simulation Parameters The calculated corrected Manhattan distance and the true distance are compared as follows: Figure 7 and 8 As shown.

[0046] Statistical analysis shows that the maximum error of the proposed corrected Manhattan distance is 0.138m, and the average error is 0.004m, which meets the accuracy requirements for calculating the spatial morphology distribution of the synthetic beam of distributed coherent radar.

[0047] With simulation parameters unchanged, the calculation time for the corrected Manhattan distance based on the spatial grid is about 0.19s, while the calculation time based on Euclidean distance is about 0.26s. Compared with the calculation method based on Euclidean distance, the calculation time can be reduced by 18.2%.

[0048] Furthermore, the number of radar units and the spatial segmentation range can be changed. Figure 9 It shows the pattern of change in the distance calculation time.

[0049] Figure 10 and 11This paper presents a typical spatial beamform subdivision example for distributed coherent radar. It shows that, in addition to saving computation time, when representing the synthetic beam, it is not necessary to consider whether a point in space is in the near or far field of the distributed coherent radar, achieving a unified description of near and far fields. Furthermore, since the spatial grid method is used to represent the beamform of the distributed coherent radar, it also saves graphics display resources because it eliminates the need for point-by-point calculation and depiction. Under the current simulation parameters, a total of 23,529 grids are used. If the same minimum scale grid is used for subdivision, 2,250,000 grids would be required.

[0050] This application proposes a spatial beamform characterization method for distributed coherent radar based on spatially partitioned grids. By analyzing the main influencing factors of spatial beamform, it points out that the multi-level spatial partitioning characteristics of the spatial grid meet the requirements of spatial beam calculation for distributed coherent radar. Through adaptive grid scale selection, graphic display resources can be effectively saved without affecting the synthetic beam display.

[0051] The above description is merely a specific implementation of the embodiments of the present invention, but the protection scope of the embodiments 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 embodiments of the present invention should be included within the protection scope of the embodiments of the present invention. Therefore, the protection scope of the embodiments of the present invention should be determined by the protection scope of the claims.

Claims

1. A distributed coherent radar beam characterization method based on spatial grids, characterized in that, include: Based on the array configuration of the distributed coherent radar, the gradient of beam shape variation with spatial location is calculated; wherein, the distributed coherent radar consists of multiple spatially dispersed unit radars, and the array configuration is used to describe the layout of the multiple spatially dispersed unit radars. Based on the changing gradient, the probe space is adaptively meshed; Within each of the partitioned spatial grids, the energy gain of the synthetic beam formed by the coordinated action of each unit radar is calculated. The energy gain of the synthesized beam is mapped to the corresponding spatial grid to characterize the distributed coherent radar beam pattern.

2. The distributed coherent radar beam characterization method based on spatial grids according to claim 1, characterized in that, The array configuration includes the number of unit radars; the variation gradient is the variation gradient of the synthetic beam energy gain. The calculation of the beamform variation gradient with spatial location based on the array configuration of the distributed coherent radar specifically includes: When the number of unit radars in the distributed coherent radar is 2, the energy gain of the synthetic beam is calculated according to expression (13); (13) in, Indicates the synthesized beam energy gain. This represents the difference between the distance from a point in space to the first radar cell and the distance to the second radar cell. , Indicates wavelength; Differentiating the expression formula (13) yields the gradient of the change in the energy gain of the synthesized beam; (14) in, This represents the gradient of the change in the energy gain of the synthesized beam.

3. The distributed coherent radar beam characterization method based on spatial grids according to claim 2, characterized in that, The adaptive mesh partitioning of the probe space based on the changing gradient specifically includes: When the gradient of change is less than a preset threshold, a single spatial grid is used to divide the corresponding region.

4. The distributed coherent radar beam characterization method based on spatial grids according to claim 2, characterized in that, The step of calculating the gradient of beamform variation with spatial location based on the array configuration of the distributed coherent radar also includes: When the number of unit radars of the distributed coherent radar exceeds 2, the gradient of the change in the synthetic beam energy gain is calculated by numerical simulation.

5. The distributed coherent radar beam characterization method based on spatial grids according to claim 2, characterized in that, The synthesized beam energy gain is the transmit coherent efficiency; the expression (13) is obtained as follows: The ratio of the actual synthesized beam energy to the ideal synthesized beam energy is calculated, and the expression for the transmission coherent efficiency is obtained (8): (8) in, Indicates taking the conjugate; Indicates the signal duration, and the transmit coherent efficiency satisfies And under ideal correction conditions, The value is 1; Approximate expression (8) to expression (9): （9） in, Indicates the first Individual radar units Indicates the first Individual radar units Indicates the number of radar units. , ; If the distributed coherent radar transmits a narrowband signal, then expression (9) is further simplified to expression (10): （10） in, Represents the distance from a point in space to the nth The distance of the first radar unit and the distance to the second radar unit The difference in distance between individual radar units; The number of unit radars in a distributed coherent radar Substitute 2 into expression (10) to obtain expression (13).

6. The distributed coherent radar beam characterization method based on spatial grids according to claim 5, characterized in that, The expression (8) is obtained as follows: Get the The expression for the transmitted signal of a single-unit radar (1): （1） in, Indicates the first Each unit radar in time The transmitted signal, , , and They represent the first The amplitude error, carrier frequency error, time error, and phase error of each radar unit. Indicates baseband signal, This represents the ideal carrier frequency for the transmitted signal; Set a space to synthesize a point The coordinates are Based on expression (1), the transmitted signals of each unit radar are in The synthesized signal at that point is: （2） in, This represents the complex gain resulting from different transmission paths. Indicates the first The transmitted signals from each radar unit reach the target point. Time delay at the location; In a distributed coherent radar system, a reference radar is selected, and the remaining element radars are corrected based on the reference radar. The expression for the transmission coherent parameters is as follows: （3） After obtaining the estimated values ​​of the transmission coherence parameters, each radar unit corrects the transmission parameters based on these estimated values. The corrected synthesized signal at point is represented as: （4） in, This represents the estimated value of the launch time coherent parameter. This represents the estimated value of the transmit phase coherent parameters; When the coherent parameters are perfectly estimated The ideal synthesized signal at point is represented as: （5） Ignoring the initial phase and time delay, expression (5) is further expressed as: （6） At any point in space At the location, according to expression (7), calculate The actual synthesized signal at that location: （7） in, express The actual synthesized signal at the location; Based on expressions (6) and (7), the ratio of the actual synthesized beam energy to the ideal synthesized beam energy is calculated, and the expression (8) for the transmission coherent efficiency is obtained.

7. The distributed coherent radar beam characterization method based on spatial grids according to claim 1, characterized in that, The mesh partitioning rules include: Based on the existing GeoSOT 32-level mesh, the mesh is further subdivided into 3 levels according to the principle of quad-branch partitioning, adding three finer-grained mesh levels, bringing the total number of levels to 35. The mesh accuracies corresponding to the three finer-grained mesh levels are (1 / 8192)″ (0.375cm), (1 / 32768)″ (0.094cm), and (1 / 131072)″ (0.023cm), respectively.

8. The distributed coherent radar beam characterization method based on spatial grids according to claim 1, characterized in that, Also includes: The corrected Manhattan distance between two spatial grids is expressed as follows: （11） in, This indicates a correction for the Manhattan distance. This represents the distance between two points in this dimension. It represents the angle between two points with the equator as the reference.

9. The distributed coherent radar beam characterization method based on spatial grids according to claim 8, characterized in that, （12）。 10. A distributed coherent radar, characterized in that, The distributed coherent radar beam characterization method based on spatial grids as described in any one of claims 1 to 9 is applied.

Images