Phased array radar differential interference measurement error phase compensation method

Abstract

The invention discloses a phased array radar differential interference measurement error phase compensation method, which is a differential interference measurement error phase compensation method, and comprises the following steps of: performing parametric modeling on errors introduced by atmosphere and vibration, grouping PS points according to a sliding window, and performing phase compensation on adjacent wave position constraint weighting. And phased array radar differential interference high-precision differential interference measurement is realized. According to the method, the problem that an existing global phase compensation scheme is not suitable for phased array radar differential interference measurement is solved, more accurate differential interference measurement error phase estimation and compensation caused by atmospheric disturbance and platform vibration under a phased array radar system are achieved, and the accuracy of differential interference measurement is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar differential interferometry, and in particular relates to a phase compensation method for phased array radar differential interferometry measurement errors. Background Art

[0002] Radar differential interferometry technology is a high-precision deformation measurement method based on differential interferometry processing. By analyzing the interference phase between radar images acquired at different times, it extracts surface deformation information. Based on the radar operating frequency band, it can achieve submillimeter deformation measurement and is widely used in the field of deformation monitoring.

[0003] Ground-based radar's differential interferometry measurement errors primarily stem from atmospheric effects. Radar signals are typically processed using the speed of light in a vacuum as a standard. However, electromagnetic waves propagate slower than the speed of light in the presence of atmospheric media. Temperature, pressure, and water vapor pressure in the atmosphere are all spatiotemporally variable, resulting in different delays for electromagnetic waves at different times and spatial locations. Phase compensation for atmospheric-induced errors is often performed using Permanent Scatterer (PS) technology. This utilizes the long-term stability of PS to establish a model linking atmospheric phase and spatial position, estimate the unknown parameters in the model, and compensate for atmospheric phase disturbances at the PS and nearby pixels in the scene.

[0004] Currently, there is little research on differential interferometry for phased array radars. Phased array radars achieve rapid azimuth scanning of the beam by controlling the phase and amplitude of each radiating element in the array antenna. Combined with broadband signal pulse compression technology, this enables high-resolution imaging of the target area. Based on differential interferometry, phased array radars are capable of measuring surface deformation.

[0005] Phased array radar differential interferometry measurement involves two primary sources of error: First, changes in atmospheric conditions can cause atmospheric disturbance phase errors; second, short-term, weak vibrations of the radar platform, caused by wind disturbances or the influence of passing vehicles, can lead to vibration phase errors. Typically, the atmosphere is evenly distributed across the monitoring scene, and the atmospheric disturbance phase error can be modeled using pixel slant range, elevation, and azimuth information, allowing for conventional global compensation schemes. However, due to the wave-by-wave imaging characteristics of phased array radars, the differential interferometry phase error introduced by radar vibration exhibits a characteristic variation with the wave-by-wave position. Conventional global compensation schemes based on PS technology cannot accurately compensate for this type of phase error.

[0006] In summary, when ground-based phased array radar performs differential interferometry, the atmospheric and radar vibrations cause nonlinear changes in the differential interferometry phase, which makes conventional methods ineffective. In order to ensure the accuracy of phased array radar deformation measurement, it is necessary to study a joint compensation method for the error phase introduced by atmospheric and radar vibrations. Summary of the Invention

[0007] In view of this, the present invention provides a phase compensation method for differential interferometry measurement errors of a phased array radar, which can effectively improve the deformation measurement accuracy of the phased array radar.

[0008] The specific technical solutions adopted in the present invention are as follows:

[0009] Step 1: Select a certain number of phased array radar images, obtain PS points in the images, and record the differential interferometry phase of the PS points in the current image;

[0010] Step 2: Parameterize the atmospheric disturbance error phase introduced by atmospheric condition changes to model the parameters;

[0011] Step 3: Parameterize the vibration error phase introduced by the short-term weak vibration of the radar platform;

[0012] Step 4: Select a certain number of adjacent wave positions to form a fan-shaped window, group the PS points by rotating the fan-shaped window in azimuth, and estimate the differential interferometry error phase of the PS points in each group;

[0013] Step 5: Perform differential interferometry phase compensation on the PS point with adjacent wave position constraints.

[0014] Furthermore, the parameterized modeling of the atmospheric disturbance error phase in step 2 uses the “slant range-elevation” model.

[0015] Furthermore, in step three, the parametric modeling of the vibration error phase of the phased array radar is first performed by establishing a Cartesian coordinate system with the geometric center of the radar as the origin. Based on the array orientation, the displacement of the geometric center caused by the vibration is analyzed, and the slant range change of the target point caused by the vibration is obtained using the Taylor series expansion to achieve parametric modeling.

[0016] Furthermore, the differential interference error phase estimation of the PS points within the group in step 4 is performed by jointly estimating the differential interference error phases in steps 2 and 3 using the least squares method.

[0017] Furthermore, the wave position constraint in step five refers to the PS point grouping result in step four. If a PS point is divided into multiple groups, each of these groups has an error phase estimation value. These estimation values are weighted and summed to achieve the constraint between adjacent wave positions.

[0018] Beneficial effects:

[0019] The present invention discloses a phase compensation method for differential interferometry measurement errors in phased array radars. First, the differential interferometry phase of PS points in the image is obtained. Then, the atmospheric disturbance error phase and the vibration error phase are parameterized and modeled separately. The PS points are grouped according to a fan-shaped window rotated in azimuth, and the error phases of the PS points within each group are jointly estimated. Finally, phase compensation is performed based on the adjacent wave position constraints, combining the characteristics of the phased array radar's wave position-by-wave position synthesis radar image.

[0020] Compared with conventional solutions, the present invention has the following advantages:

[0021] 1. Compared with conventional global atmospheric compensation schemes, the present invention combines the imaging characteristics of phased array radar to more accurately compensate for the phase error of phased array radar differential interferometry caused by atmospheric disturbances and platform vibration, which is conducive to ensuring the accuracy of phased array radar differential interferometry.

[0022] 2. The present invention sets a weighting parameter in the group compensation. By changing the weighting parameter, the weight of the central wave position in the fan-shaped window and the strictness of the adjacent wave position constraint can be adjusted, thereby adjusting the estimation accuracy, so that the present invention can be better applied to different scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the present invention;

[0024] Figure 2 Schematic diagram of phased array radar image and PS screening results;

[0025] Figure 3 Schematic diagram of radar vibration in the Cartesian coordinate system of the present invention;

[0026] Figure 4 This is a schematic diagram of a fan-shaped window of the present invention;

[0027] Figure 5 Schematic diagram of the original differential interference phase at point PS;

[0028] Figure 6 Schematic diagram of repeated estimation of PS points of the present invention;

[0029] Figure 7 Scatter plots before and after PS point compensation;

[0030] Figure 8 This is the differential interferometry phase image at point PS after compensation. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0032] In this embodiment, the number of fan-shaped window wave positions, radar and target position coordinates involved are all examples and are not limited to the parameters shown. During the specific implementation process, technicians in this field can adjust them according to actual conditions.

[0033] The present invention provides a phased array radar differential interferometry measurement error phase compensation method, the flow chart is as follows Figure 1 As shown, the following steps are included:

[0034] Step 1: Select a certain number of phased array radar images, obtain the PS points in the image, and record the differential interferometry phase of the PS points in the current image.

[0035] Phased array radar acquires a certain number of images and selects PS points using the amplitude deviation method. Then, differential interference is performed on the two radar images acquired at different times, and phase unwrapping is achieved using the minimum cost flow method to obtain the differential interference phase of the PS point. Figure 2 (a) shows a phased array radar image with 100 beam positions from 35° to -35° in azimuth. Figure 2 (b) is the PS point screening result.

[0036] Step 2: Parameterize the atmospheric disturbance error phase introduced by atmospheric condition changes

[0037] like Figure 3 As shown in the figure, in the Cartesian coordinate system, when the radar is stationary, the geometric center of the phased array radar is located at the coordinate point O1 (0,0,0), the antenna array is parallel to the yoz plane, and perpendicular to the xoy plane, facing the positive direction of the x-axis. p ,y p ,z p The slant distance R1 between the target point P and the geometric center of the phased array radar is

[0038] For ground-based systems, it can be assumed that the atmosphere within the monitoring range is uniformly distributed, and the atmospheric phase component can be constructed into a model that changes linearly with the slant distance. However, when there is terrain in the monitoring scene, the atmospheric refraction will change with the elevation, so the atmospheric disturbance error can be Constructed into a "slope distance-elevation" model:

[0039]

[0040] Where c represents the speed of light, f c represents the radar carrier frequency, and C1, C2, and C3 are model coefficients.

[0041] Step 3: Parametric modeling of the vibration error phase introduced by short-term weak vibration of the radar platform

[0042] like Figure 3 As shown in the figure, when the phased array radar is affected by wind disturbance or passing vehicles, the geometric center changes from the coordinate origin O1(0,0,0) to O2(ε x ,ε y ,ε z ), the distance R1′ from the changed radar geometric center position O2 to the target point P is Perform a multivariate Taylor series expansion on R1′ at the coordinate (0,0,0):

[0043]

[0044] The slant range change due to radar vibration is:

[0045]

[0046] Therefore, the interference phase error of the target point P due to vibration is Expressed as:

[0047]

[0048] Among them, A i (i=1,2,3) is the offset coefficient.

[0049] Step 4: Select a certain number of adjacent wave positions to form a fan-shaped window, group the PS points by rotating the fan-shaped window in azimuth, and estimate the differential interference error phase of the PS points in each group.

[0050] like Figure 4 As shown, select N beam (N beam (an odd number) of wave positions as fan-shaped windows. Assume that the entire phased array radar image has N t wave positions, the first fan-shaped window includes the 1st to the Nth beam wave positions, the central wave position is (N beam +1) / 2 wave position; move one wave position to get the second fan-shaped window, including the 2nd to Nth beam +1 wave position, the center wave position is (N beam +3) / 2 wave positions. With this sliding window type of movement, you can get N t -N beam +1 fan-shaped window. Record the PS points in each fan-shaped window and group them.

[0051] Combined with the atmospheric disturbance error phase in steps 2 and 3 Vibration error phase As well as the random error e caused by noise, when no deformation occurs, the differential interference phase of the target point P It can be expressed as:

[0052]

[0053] Figure 5 The figure shows the differential interference phase of PS points at different wave positions. When there is no invisible change between two adjacent radar images, the differential interference phase should be zero. However, the PS points selected in the figure are seriously interfered with, and the differential interference phase is It changes periodically with the wave position.

[0054] The following error parameter estimation is performed for each group of PS points. Assuming that there are N PS points in the nth group involved in the estimation, the following set of equations is established based on the phase information and coordinate information of the PS points:

[0055] ΔΦ=Xβ+Ε (6)

[0056]

[0057] Where ΔΦ is the N×1 dimensional vector composed of the differential interference phases of the N PS points in the nth group; in X, x i (i=1,2,…,N) corresponds to the x-axis coordinates of the N PS points in the group, R i (i=1,2,…,N) corresponds to the slope distance between the N PS points in the group and the origin, z i (i=1,2,…,N) corresponds to the z-axis coordinates of the N PS points in the group; β is a 6×1 dimensional vector composed of the parameters to be estimated; E is an N×1 dimensional vector composed of random errors.

[0058] According to the least squares estimation algorithm, the estimated parameter vector β is estimated, and we can get

[0059]

[0060] Therefore, the estimated value of the differential interferometric error phase of N PS points in group i is It can be expressed as

[0061]

[0062] Step 5: Perform differential interferometry phase compensation on the PS point with adjacent wave position constraints

[0063] In total N t In the phased array radar image of wave positions, taking the nth fan window as an example, when the number of wave positions in the fan window is N beam =5, such as Figure 6As shown, according to step 3, parameter estimation is performed on all PS points in the n-2th to n+2th wave positions, that is, fan-shaped window 1; the n+1th fan-shaped window, that is, fan-shaped window 2, includes the n-1th to n+3th wave positions, and parameter estimation is also performed on all PS points in this fan-shaped window according to step 3. Fan-shaped window 1 and fan-shaped window 2 both include the n-1th to n+2th wave positions, and the PS points of the overlapping wave positions will have two estimated values. Therefore, when repeated estimation is generated, taking a PS point as an example, the differential interference error phase of all repeated estimates of the PS point is recorded. And use the weighting factor ω j right Weighted. j The wave position N of the PS point ps The central wave position N of the fan window is estimated each time the PS point is estimated. cen The number of waves between them is determined, the fewer the number of waves, the greater the weight, ω j The definition is as follows

[0064]

[0065] Among them, λ is the weighting parameter. When λ is close to 0, N cen =N ps The fan-shaped window estimates Weight Close to 1, other estimators weight ω j (j≠(N beam +1) / 2) is close to 0; when λ is close to positive infinity, the weight ω of all differential interferometry phase estimates j same.

[0066] Finally, we get the error estimate as follows

[0067]

[0068] Thus, the interference phase estimation constraint between adjacent wave positions is realized to reduce the estimation error. Finally, the differential interference phase of the PS point obtained by actual measurement is used. minus Realize error phase compensation.

[0069] Figure 7 (a) shows a scatter plot of the original differential interferometry phase at the PS point and the error phase estimated by the patented method. The compensation method of this patent accurately estimates the error phase caused by the atmosphere and vibration. Figure 7 (b) shows the differential interference phase scatter diagram of the PS point at each wave position after compensation. Figure 8 The differential interferometry phase image of the PS point after compensation is shown. The differential interferometry phase at the PS point returns to near 0 rad, and the error phase is effectively compensated.

[0070] The above specific embodiments merely illustrate the design principles of the present invention. The names and threshold settings in this description may vary and are not limiting. Therefore, those skilled in the art may modify or replace the technical solutions described in the above embodiments with equivalents. Such modifications and replacements, without departing from the inventive spirit and technical solutions of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A phased array radar differential interferometry measurement error phase compensation method, characterized in that: include: Step 1: Select a certain number of phased array radar images, obtain the PS (Permanent Scatterer) points in the image, and record the differential interferometry phase of the PS points in the current image; Step 2: Parameterize the atmospheric disturbance error phase introduced by atmospheric condition changes to model the parameters; Step 3: Parameterize the vibration error phase introduced by the short-term weak vibration of the radar platform; Step 4: Select a certain number of adjacent wave positions to form a fan-shaped window, group the PS points by rotating the fan-shaped window in azimuth, and estimate the differential interferometry error phase of the PS points in each group; Step 5: Perform differential interferometry phase compensation on the PS point with adjacent wave position constraints.

2. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, characterized in that: In step 2, the parameterized modeling of the atmospheric disturbance error phase uses the "slant range-elevation" model.

3. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, characterized in that: In step 2, the "slope range-elevation" model is: Where c represents the speed of light, f c represents the radar carrier frequency, and C1, C2, and C3 are model coefficients.

4. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, wherein: In step three, the parametric modeling of the vibration error phase of the phased array radar is performed. First, a Cartesian coordinate system is established with the geometric center of the radar as the origin. Based on the array orientation, the displacement of the geometric center caused by vibration is analyzed. The Taylor series expansion is used to obtain the change in the slant range of the target point caused by vibration, thus realizing parametric modeling.

5. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, wherein: In step 3, the interference phase error of the target point P due to vibration is Expressed as: Among them, A i (i=1,2,3) is the offset coefficient.

6. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, characterized in that: In step 4, the differential interference error phase of the PS points in the group is estimated by jointly estimating the differential interference error phases in steps 2 and 3 using the least squares method.

7. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, wherein: In step 4, when the invisible deformation occurs, the differential interference phase of the target point P is It can be expressed as: in is the atmospheric disturbance error phase, is the vibration error phase, and e is the random error caused by noise.

8. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, wherein: In step 5, the wave position constraint refers to the PS point grouping result in step 4. If a PS point is divided into multiple groups, each of these groups has an error phase estimation value. These estimation values are weighted and summed to implement the constraint between adjacent wave positions.

9. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, wherein: In step five, ω j The definitions are as follows: Among them, λ is the weighting parameter. When λ is close to 0, N cen =N ps The fan-shaped window estimates Weight Close to 1, other estimators weight ω j (j≠(N beam +1) / 2) is close to 0; when λ is close to positive infinity, the weight ω of all differential interferometry phase estimates j same.

10. The phase compensation method for differential interferometry measurement error of a phased array radar according to claim 1, characterized in that: In step 5, the error estimate for:

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