Azimuth ambiguity calculation method and device for space-borne synthetic aperture radar

Abstract

The present application relates to the technical field of signal processing, in particular to a kind of azimuth ambiguity calculation method and device of space-borne synthetic aperture radar.Method comprising: obtaining the set parameter of space-borne radar;For each working mode, it is executed: based on set parameter, determine the position vector of target scene center point when space-borne radar irradiates target scene center point in current working mode, the latitude and longitude of target scene center point and the position vector of equivalent rotating point;Determine the position vector of each target position point in target scene;Determine the irradiation time of space-borne radar irradiating each target position point, and determine the off-axis angle of current target position point and radar beam pointing angle at each irradiation time in irradiation time;Determine the azimuth ambiguity of each target position point, to determine the azimuth ambiguity variation curve in current working mode.This scheme can improve the azimuth ambiguity calculation efficiency of space-borne synthetic aperture radar in different working modes by using general calculation method.

Description

Technical Field

[0001] This invention relates to the field of signal processing technology, and in particular to a method and apparatus for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar. Background Technology

[0002] Spaceborne synthetic aperture radar (SAR) is an active microwave imaging radar that transmits microwave signals and receives the scattered echo signals from ground targets through an antenna. The data is then processed to obtain a SAR image of the observed area. SAR has a wide observation range, is not limited by sunlight or weather conditions, and has all-weather, all-day operation capabilities. It also has a certain degree of penetration capability against certain ground features, and has become an important component of military and civilian Earth observation systems in various countries.

[0003] Azimuth ambiguity reflects the degree of interference between the azimuth sidelobe signal and the main lobe signal, and is an important indicator in spaceborne SAR. However, existing methods for calculating azimuth ambiguity in spaceborne synthetic aperture radar are only applicable to certain operating modes of spaceborne SAR, and there is no universal method for calculating azimuth ambiguity across different operating modes. This inevitably affects the efficiency of azimuth ambiguity calculation in different operating modes of spaceborne synthetic aperture radar.

[0004] Therefore, there is an urgent need for a new method for calculating the azimuth ambiguity of spaceborne synthetic aperture radar. Summary of the Invention

[0005] To address the issue that existing methods for calculating azimuth ambiguity in spaceborne synthetic aperture radar are not applicable to various operating modes, this invention provides a method and apparatus for calculating azimuth ambiguity in spaceborne synthetic aperture radar.

[0006] In a first aspect, embodiments of the present invention provide a method for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar, including:

[0007] Obtain the setting parameters of the spaceborne radar;

[0008] For each working mode, the following steps are performed: Based on the set parameters, determine the satellite's motion coordinate parameters, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point when the spaceborne radar illuminates the target scene center point in the current working mode; wherein, the spaceborne radar is located on the satellite;

[0009] Based on the set parameters, the pre-determined flight trajectory of the satellite, and the latitude and longitude of the center point of the target scene, the position vector of each target location point set in the target scene is determined;

[0010] Based on the set parameters, the position vector of the equivalent rotation point, and the position vector of each target position point, the illumination time of the spaceborne radar illuminating each target position point is determined, and the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time are determined.

[0011] Based on the set parameters and the off-axis angle and radar beam pointing angle of each target location at each illumination moment, the azimuth ambiguity of each target location is determined, so as to determine the azimuth ambiguity change curve under the current working mode.

[0012] Secondly, embodiments of the present invention also provide an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar, comprising:

[0013] The acquisition unit is used to acquire the setting parameters of the spaceborne radar;

[0014] The first determining unit is used to perform the following for each working mode: based on the set parameters, determine the motion coordinate parameters of the satellite when the spaceborne radar illuminates the center point of the target scene, the position vector of the center point of the target scene, the latitude and longitude of the center point of the target scene, and the position vector of the equivalent rotation point of the center point of the target scene; wherein, the spaceborne radar is located on the satellite;

[0015] The second determining unit is used to determine the position vector of each target location point set in the target scene based on the set parameters, the pre-determined flight trajectory of the satellite and the latitude and longitude of the center point of the target scene;

[0016] The third determining unit is used to determine the illumination time of each target position point by the spaceborne radar based on the set parameters, the position vector of the equivalent rotation point and the position vector of each target position point, and to determine the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time.

[0017] The fourth determining unit is used to determine the azimuth ambiguity of each target location point based on the set parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment, so as to determine the azimuth ambiguity change curve under the current working mode.

[0018] Thirdly, embodiments of the present invention also provide a computing device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the method described in any embodiment of this specification.

[0019] Fourthly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the methods described in any embodiment of this specification.

[0020] This invention provides a method and apparatus for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar. First, the setting parameters of the spaceborne radar are acquired. Then, for each operating mode, the following steps are performed: based on the setting parameters, the motion coordinate parameters of the satellite, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point are determined when the spaceborne radar illuminates the center point of the target scene in the current operating mode. Next, based on the setting parameters, the pre-determined satellite trajectory, and the latitude and longitude of the target scene center point, the position vectors of each target location point in the target scene are determined. Following this, based on the setting parameters, the position vector of the equivalent rotation point, and the position vectors of each target location point, the illumination time of the spaceborne radar illuminating each target location point is determined, and the off-axis angle and radar beam pointing angle of the current target location point at each illumination moment within the illumination time are determined. Finally, based on the setting parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment, the azimuth ambiguity of each target location point is determined to determine the azimuth ambiguity variation curve for the current operating mode, thereby obtaining the azimuth ambiguity variation curve for each operating mode. This scheme fully considers the spatial geometric characteristics of different operating modes and can use a general method to calculate the azimuth ambiguity variation curve for each operating mode, thereby improving the azimuth ambiguity calculation efficiency of spaceborne synthetic aperture radar in different operating modes. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of an azimuth ambiguity calculation method for a spaceborne synthetic aperture radar according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of a space-ground geometric relationship provided in an embodiment of the present invention;

[0024] Figure 3 This is a hardware architecture diagram of a computing device provided in an embodiment of the present invention;

[0025] Figure 4 This is a structural diagram of an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] As mentioned earlier, existing methods for calculating azimuth ambiguity in spaceborne synthetic aperture radar (SAR) are only applicable to certain operating modes of spaceborne SAR. There is no universal method for calculating azimuth ambiguity across different operating modes, which inevitably affects the efficiency of azimuth ambiguity calculation in different operating modes of spaceborne SAR.

[0028] To solve the above-mentioned technical problems, the inventors can fully consider the spatial geometric characteristics of different working modes and invent an azimuth ambiguity calculation method applicable to different working modes, thereby improving the azimuth ambiguity calculation efficiency of spaceborne synthetic aperture radar in different working modes.

[0029] The following describes the specific implementation of the above concept.

[0030] Please refer to Figure 1 This invention provides a method for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar, the method comprising:

[0031] Step 100: Obtain the setting parameters of the spaceborne radar;

[0032] Step 102: For each working mode, perform the following: Based on the set parameters, determine the satellite's motion coordinate parameters, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point when the spaceborne radar illuminates the target scene center point in the current working mode; wherein, the spaceborne radar is located on the satellite;

[0033] Step 104: Based on the set parameters, the pre-determined satellite trajectory, and the latitude and longitude of the target scene center point, determine the position vector of each target location point set in the target scene;

[0034] Step 106: Based on the set parameters, the position vector of the equivalent rotation point and the position vector of each target position point, determine the illumination time of the spaceborne radar illuminating each target position point, and determine the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time.

[0035] Step 108: Based on the set parameters and the off-axis angle and radar beam pointing angle of each target location at each illumination moment, determine the azimuth ambiguity of each target location to determine the azimuth ambiguity change curve under the current working mode.

[0036] In this embodiment of the invention, firstly, the setting parameters of the spaceborne radar are obtained; then, for each working mode, the following steps are performed: based on the setting parameters, the motion coordinate parameters of the satellite, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point are determined when the spaceborne radar illuminates the target scene center point in the current working mode; next, based on the setting parameters, the pre-determined satellite trajectory, and the latitude and longitude of the target scene center point, the position vectors of each target location point set in the target scene are determined; then, based on the setting parameters, the position vector of the equivalent rotation point, and the position vectors of each target location point, the illumination time of the spaceborne radar illuminating each target location point is determined, and the off-axis angle and radar beam pointing angle of the current target location point at each illumination moment within the illumination time are determined; finally, based on the setting parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment, the azimuth ambiguity of each target location point is determined, so as to determine the azimuth ambiguity change curve of the current working mode, thereby obtaining the azimuth ambiguity change curve of each working mode. This scheme fully considers the spatial geometric characteristics of different operating modes and can use a general method to calculate the azimuth ambiguity variation curve for each operating mode, thereby improving the azimuth ambiguity calculation efficiency of spaceborne synthetic aperture radar in different operating modes.

[0037] For step 100:

[0038] In this embodiment of the invention, the set parameters of the spaceborne radar may include the center time η0 when the spaceborne radar illuminates the center point of the target scene, the geocentric gravitational constant μ, the semi-major axis a of the satellite orbit, the eccentricity e of the satellite orbit, the right ascension of the ascending node Ω, the orbital inclination i, the argument of perigee ω, and the angular velocity of Earth's rotation ω. e Earth's semi-major axis R a That is, the equatorial radius, the Earth's minor semi-axis R. b That is, the polar radius, the antenna center viewing angle θ m The roll angle θ for satellite attitude adjustment r Pitch angle θ p yaw angle θ y azimuth resolution ρ a Azimuth resolution broadening factor K ρ Azimuth antenna size L a Azimuth antenna stretch factor K wAzimuth scene point count N_point_a, azimuth lattice spacing D_point_a, range scene point count N_point_r, range lattice spacing D_point_r, pulse repetition frequency PRF, azimuth sampling point count Ver_data, satellite equivalent velocity v sat Radar operating wavelength λ, azimuth time interval M, azimuth ambiguity zone N.

[0039] Regarding step 102:

[0040] In this embodiment of the invention, step 102 may include the following steps S1-S7:

[0041] Step S1: Using the Earth's center as the origin, establish the rotating geocentric coordinate system, the stationary geocentric coordinate system, the orbital plane coordinate system, the satellite platform coordinate system, the satellite body coordinate system, and the satellite antenna coordinate system in sequence.

[0042] like Figure 2 As shown, with the Earth's center as the origin, the following coordinate systems are established in sequence: rotating geocentric coordinate system X1Y1Z1, stationary geocentric coordinate system X2Y2Z2, orbital plane coordinate system X3Y3Z3, satellite platform coordinate system X4Y4Z4, satellite body coordinate system X5Y5Z5, and satellite antenna coordinate system X6Y6Z6.

[0043] Step S2: Based on the set parameters, calculate the motion coordinate parameters of the satellite in the rotating geocentric coordinate system when the satellite-borne radar illuminates the center point of the target scene; wherein, the motion coordinate parameters include the satellite position vector, the satellite velocity vector, and the satellite acceleration vector.

[0044] In this embodiment of the invention, the center time refers to the moment when the center beam of the radar illuminates the center point of the target scene. Based on set parameters, the motion coordinate parameters of the satellite in the rotating geocentric coordinate system are calculated at the center time η0 when the spaceborne radar illuminates the center point of the target scene; wherein, the motion coordinate parameters include the satellite position vector. Satellite velocity vector and satellite acceleration vector

[0045] Specifically, the satellite orbital eccentricity angle E corresponding to the center time η0 is solved according to the following Kepler equations:

[0046]

[0047] Where μ is the geocentric gravitational constant, a is the semi-major axis of the satellite orbit, and e is the eccentricity of the satellite orbit; the eccentricity angle E can be obtained through Taylor series expansion.

[0048] Then, using the relationship between the true pericentric angle θ and the eccentric angle E shown in the following formula (2), the true pericentric angle θ of the satellite orbit corresponding to the center time η0 is solved:

[0049]

[0050] In the formula, e is the satellite orbital eccentricity.

[0051] Next, the radius vector r is calculated according to the satellite orbit equation shown in formula (3):

[0052]

[0053] In the formula, a is the semi-major axis of the satellite orbit, e is the eccentricity of the satellite orbit, and θ is the true pericentric angle of the satellite orbit corresponding to the center time η0.

[0054] Next, the satellite position vector in the rotating geocentric coordinate system can be calculated using the following formulas (4a)-(4c).

[0055]

[0056]

[0057]

[0058] In the formula, (rcosθ,rsinθ,0) is the satellite position vector in the orbital plane coordinate system, θ is the true pericentric angle, and A ov Let A be the transformation matrix from the orbital plane coordinate system to the stationary geocentric coordinate system. go Let Ω be the transformation matrix from a stationary geocentric coordinate system to a rotating geocentric coordinate system, where Ω is the right ascension of the ascending node, i is the orbital inclination, ω is the argument of perigee, and H is the transformation matrix. G H is the Greenwich Mean Time angle from the satellite's position to the vernal equinox. G =ω e ·η0,ω e This represents the Earth's rotational angular velocity. In this embodiment, the satellite position vector is obtained by transforming from the orbital plane coordinate system to the rotating geocentric coordinate system.

[0059] Similarly, the satellite velocity vector in the rotating geocentric coordinate system can be solved using the following formulas (5) and (6). and acceleration vector

[0060]

[0061]

[0062] In the formula, μ is the geocentric gravitational constant, a is the semi-major axis of the satellite orbit, e is the eccentricity of the satellite orbit, θ is the true pericentric angle, and A ov Let A be the transformation matrix from the orbital plane coordinate system to the stationary geocentric coordinate system. go Let be the transformation matrix from a stationary geocentric coordinate system to a rotating geocentric coordinate system.

[0063] Step S3: Based on the set parameters, calculate the position vector of the center point of the target scene in the rotating geocentric coordinate system when the spaceborne radar illuminates the center point of the target scene.

[0064] Specifically, in a rotating geocentric coordinate system, the position vector (x) of the center point of the target scene. t ,y t ,z t The Earth's ellipsoid equation is satisfied by the following formula (7):

[0065]

[0066] Among them, R a R is the radius of the Earth's semi-major axis, i.e., the equatorial radius. b This is the Earth's minor axis, also known as the polar radius.

[0067] Let R be the distance between the satellite and the center point of the target scene. m In the satellite antenna coordinate system, the position vector of the center point of the target scene illuminated by the beam is (0, R). m According to the following formulas (8a)-(8d), by transforming from the satellite antenna coordinate system to the rotating geocentric coordinate system, the position vector of the center point of the target scene at the center time η0 when the target scene is illuminated by the spaceborne radar can be calculated.

[0068]

[0069]

[0070]

[0071]

[0072] In the formula, A ea Let A be the transformation matrix from the satellite antenna coordinate system to the satellite body coordinate system. re Let A be the transformation matrix from the satellite body coordinate system to the satellite platform coordinate system. vr Let A be the transformation matrix from the satellite platform coordinate system to the orbital plane coordinate system. ov Let A be the transformation matrix from the orbital plane coordinate system to the stationary geocentric coordinate system. go Let θ be the transformation matrix from a stationary geocentric coordinate system to a rotating geocentric coordinate system.m θ is the center viewpoint of the antenna. r θ is the roll angle used for satellite attitude adjustment. p Let θ be the pitch angle. y Let θ be the yaw angle, θ be the true pericentric angle of the satellite orbit, and γ be the satellite track angle, and γ = arctan(esinθ / (1+ecosθ)), where e is the satellite orbital eccentricity.

[0073] By combining the formula for calculating the satellite track angle γ with formulas (7) and (8a)-(8b), the distance R between the satellite and the center point of the target scene can be solved. m and the position vector of the center point of the target scene.

[0074] Similarly, using the following formulas (9) and (10), the velocity vector of the center point of the target scene at the center time η0 in the rotating geocentric coordinate system can be solved. and acceleration vector

[0075]

[0076]

[0077] In the formula, ω e This is the Earth's rotational angular velocity.

[0078] Step S4: Determine the latitude and longitude of the target scene center point based on the position vector of the target scene center point in the rotating geocentric coordinate system.

[0079] According to the following formulas (11) and (12), calculate the latitude and longitude (Λ0, Φ0) of the center point of the target scene at the center time η0:

[0080]

[0081]

[0082] In the formula, This is the position vector of the center point of the target scene.

[0083] Step S5: Determine the mixing factor of the spaceborne radar in the current operating mode.

[0084] ①If the operating mode of the spaceborne radar is strip mode, then the mixing factor H = 1;

[0085] ②If the operating mode of the spaceborne radar is spotlight mode, then the mixing factor H = 0;

[0086] ③ If the spaceborne radar operates in sliding beam-focusing mode, then the mixing factor is... Where ρa For azimuth resolution, L a K represents the azimuth antenna size. w This is the azimuth antenna stretch factor;

[0087] ④ If the spaceborne radar operates in TOPS mode, then the mixing factor is...

[0088] Therefore, this embodiment can calculate the mixing factor of the corresponding working mode according to different working modes, so as to calculate the azimuth ambiguity of different working modes.

[0089] Step S6: Based on the mixing factor, satellite position vector, and the position vector of the target scene center point, determine the position vector of the equivalent rotation point in the current working mode.

[0090] Specifically:

[0091] ① If the working mode is strip mode, the equivalent rotation point is at infinity, meaning that the satellite beam direction remains unchanged throughout the entire illumination process.

[0092] Therefore, the position vector (x) of the equivalent rotation point can be calculated according to the following formula (13). rot ,y rot ,z rot ):

[0093]

[0094] The distance ΔR from the equivalent rotation point to the center point of the target scene is infinite.

[0095] ② If the working mode is the cluster mode, the position vector (x) of the equivalent rotation point can be calculated according to the following formula (14). rot ,y rot ,z rot ):

[0096]

[0097] In the formula, This is the position vector of the center point of the target scene.

[0098] ③ If the working mode is sliding beamforming mode, the distance from the equivalent rotation point to the center point of the target scene is: The direction is along the central viewing angle of the radar beam center. The position vector (x) of the equivalent rotation point is solved by the following formula (15). rot ,y rot ,z rot ):

[0099]

[0100] In the formula, R m The distance between the satellite and the center point of the target scene. This is the satellite position vector.

[0101] ④ If the working mode is TOPS mode, the distance from the equivalent rotation point to the center point of the target scene is The position vector (x) of the equivalent rotation point is solved using the following formula (16). rot ,y rot ,z rot ):

[0102]

[0103] Regarding step 104:

[0104] In this embodiment of the invention, step 104 may include:

[0105] Centered on the center point of the target scene, set several target position points at equal intervals along the direction of the satellite's flight trajectory, and set several target position points at equal intervals along the direction perpendicular to the satellite's flight trajectory;

[0106] Based on the set parameters and the latitude and longitude of the center point of the target scene, determine the latitude and longitude of each target location point;

[0107] Based on the latitude and longitude of each target location point, determine the position vector of each target location point set in the target scene.

[0108] In this embodiment, with the center point of the target scene as the center, N_point_a target position points are set at equal intervals along the direction of the satellite's flight trajectory, and N_point_r target position points are set at equal intervals along the direction perpendicular to the satellite's flight trajectory; the coordinates of the position point in the i-th column of the azimuth direction and the j-th row of the range direction (i.e., perpendicular to the satellite's flight trajectory) within the scene are x. ij =i·D_point_a,y ij = j·D_point_r, where D_point_a is the azimuth lattice spacing and D_point_r is the range lattice spacing.

[0109] The latitude and longitude (Λ) of each target location point (i,j) can be determined according to the following formulas (17a)-(17c). ij ,Φ ij ):

[0110]

[0111] Φ ij =Φ0+x ij ·K(17b)

[0112]

[0113] In the formula, (Λ0,Φ0) represents the latitude and longitude of the center point of the target scene, and R a R is the radius of the Earth's semi-major axis, i.e., the equatorial radius. b This is the Earth's minor axis, also known as the polar radius.

[0114] Then, according to the following formulas (18a)-(18c), determine the position vector of the target location point (i,j) in the rotating geocentric coordinate system corresponding to its latitude and longitude.

[0115]

[0116]

[0117]

[0118] Regarding step 106:

[0119] In this embodiment of the invention, the step "determine the illumination time of each target position point by the spaceborne radar based on the set parameters, the position vector of the equivalent rotation point, and the position vector of each target position point" may include the following steps A1-A6:

[0120] Step A1: For each target location, perform the following: Determine the simulation time based on the set parameters and the center time of the target scene center point illuminated by the spaceborne radar.

[0121] In this step, the simulation time is determined according to the following formula (19):

[0122]

[0123] In the formula, η0 is the center time, PRF is the pulse repetition frequency, Ver_data is the number of azimuth sampling points, and n = 1, 2, ..., Ver_data. At the initial simulation time, n = 1.

[0124] Step A2: Determine the satellite position vector in the rotating geocentric coordinate system at the simulation moment.

[0125] By substituting the simulated time into formula (1) in step S2 of step 102, the satellite orbit eccentricity angle E corresponding to the simulated time can be determined. Then, by substituting the satellite orbit eccentricity angle E corresponding to the simulated time into formula (2), the true pericentric angle θ of the satellite orbit corresponding to the simulated time can be calculated. Finally, by using formulas (3)-(6), the satellite position vector in the rotating geocentric coordinate system at the simulated time can be calculated.

[0126] Step A3: Based on the satellite position vector at the simulation moment and the position vector of the current target position point, determine the off-axis angle between the satellite and the current target position point in the satellite antenna coordinate system.

[0127] In this step, the off-axis angle θ between the satellite and the current target position in the satellite antenna coordinate system can be determined using the following formula (20). st :

[0128]

[0129] In the formula, For the transformation from the rotating geocentric coordinate system to the antenna coordinate system, Let this be the satellite's position vector in the rotating geocentric coordinate system at this simulation moment. The position vector of the current target position point (i,j) calculated in step 104.

[0130] Step A4: Based on the satellite position vector and the position vector of the equivalent rotation point at the simulation moment, determine the radar beam pointing angle in the satellite antenna coordinate system.

[0131] In this step, the radar beam pointing angle θ in the satellite antenna coordinate system at this simulation moment can be determined by the following formula (21). sr :

[0132]

[0133] In the formula, For the transformation from the rotating geocentric coordinate system to the antenna coordinate system, Let this be the satellite's position vector in the rotating geocentric coordinate system at this simulation moment. The position vector of the equivalent rotation point.

[0134] Step A5: Determine whether the off-axis angle and the radar beam pointing angle are equal; if not, adjust the simulation time and use the adjusted simulation time as the new simulation time, then jump to determine the satellite position vector in the rotating geocentric coordinate system at the simulation time; if yes, then determine the simulation time as the center time of the current target position point illuminated by the spaceborne radar.

[0135] In this step, the off-axis angle θ is determined at this simulation moment. st and radar beam pointing angle θ sr Are they equal? ​​If θ st ≠θ sr If θ increases, then n is increased, and the process jumps to step A1; if θ st =θ sr The loop ends when the simulation time is reached, and the simulation time is determined as the center time η of the current target location illuminated by the spaceborne radar.ij .

[0136] Step A6: Based on the set parameters and the center time of the satellite radar illuminating the current target location, determine the illumination time of the satellite radar illuminating the current target location.

[0137] In this embodiment of the invention, step A6 may include the following steps B1-B6:

[0138] Step B1: Determine the azimuth bandwidth based on the set parameters.

[0139] In this step, the azimuth bandwidth B is calculated using the following formula (22). a :

[0140]

[0141] In the formula, v sat For the satellite's equivalent velocity, ρ a For azimuth resolution, K ρ This is the azimuth resolution broadening factor.

[0142] Step B2: Based on the center time of the current target location illuminated by the spaceborne radar, determine the start time and end time of the simulation.

[0143] In this step, the starting simulation time T1 and the ending simulation time T2 are determined according to the following formulas (23a) and (23b):

[0144]

[0145]

[0146] In the formula, η ij The center time of the current target location determined in step A5 is given by PRF, where PRF is the pulse repetition frequency, Δn = 1, 2, ..., Ver_data, and Ver_data is the number of azimuth sampling points. Initially, n = 1.

[0147] Step B3: Based on the start simulation time and the end simulation time, determine the Doppler frequencies corresponding to the start simulation time and the end simulation time, respectively.

[0148] First, by substituting the start simulation time and the end simulation time into steps A2-A3 of step 106, the off-axis angle θ corresponding to the start simulation time T1 and the end simulation time T2 can be calculated. st1 and θ st2 .

[0149] Then, the Doppler frequency fd1 corresponding to the start simulation time and the Doppler frequency fd2 corresponding to the end simulation time are calculated using the following formulas (24a) and (24b):

[0150]

[0151]

[0152] In the formula, v sat λ represents the satellite's equivalent velocity, and λ is the radar's operating wavelength.

[0153] Step B4: Based on the Doppler frequency corresponding to the start simulation time and the Doppler frequency corresponding to the end simulation time, determine the Doppler frequency offset from the start simulation time to the end simulation time.

[0154] The Doppler frequency offset Δf from the start simulation time to the end simulation time is calculated according to the following formula (25). d :

[0155]

[0156] In the formula, fd1 is the Doppler frequency corresponding to the start simulation time, fd2 is the Doppler frequency corresponding to the end simulation time, and θ st1 and θ st2 These are the off-axis angles corresponding to the start simulation time T1 and the end simulation time T2, respectively.

[0157] Step B5: Determine whether the Doppler frequency offset and azimuth bandwidth are equal; if not, adjust the start simulation time and the end simulation time, and use the adjusted start simulation time and end simulation time as the new start simulation time and end simulation time, and jump to execute the determination of the Doppler frequency corresponding to the start simulation time and the end simulation time based on the start simulation time and the end simulation time respectively; if yes, determine the start simulation time and the end simulation time as the target start time and target end time for the spaceborne radar to illuminate the current target position point respectively.

[0158] In this step, the Doppler frequency offset Δf is determined. d and azimuth bandwidth B a Are they equal? ​​If Δf d ≠B a If Δn increases, then proceed to step B2; if Δf d =B a When the loop ends, the start and end simulation times are determined as the target start and end times for the spaceborne radar to illuminate the current target location, respectively, i.e., T. l,ij =T1,T r,ij =T2.

[0159] Step B6: Based on the target start time and target end time, determine the illumination time of the current target location point illuminated by the spaceborne radar.

[0160] In this step, the irradiation time t at the current target location is calculated using the following formula (26). ij :

[0161] t ij =T r,ij -T l,ij (26)

[0162] In this embodiment of the invention, the step of "determining the off-axis angle and radar beam pointing angle of the current target position at each illumination moment within the illumination time" may include:

[0163] Based on the azimuth time interval M set in step 100, the illumination time t of the current target location point is... ij The illumination is divided into M equal illumination times. The off-axis angle θ of the current target position at each illumination time is calculated using formulas (20) and (21). st and radar beam pointing angle θ sr .

[0164] In summary, based on step 106, the illumination time for each target location point and the off-axis angle θ at each illumination moment within the illumination time can be calculated. st (m) and radar beam pointing angle θ sr (m).

[0165] In this embodiment of the invention, different mixing factors and equivalent rotation points are introduced for spaceborne radars in different operating modes, which can calculate the azimuth ambiguity in different operating modes, simplifying the cumbersome calculation process in different operating modes, thereby improving the azimuth ambiguity calculation efficiency of spaceborne synthetic aperture radar in different operating modes.

[0166] Regarding step 108:

[0167] In this embodiment of the invention, the step "determine the azimuth ambiguity of each target location point based on the set parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment" may include the following steps C1-C5:

[0168] Step C1, for each target location, performs the following: based on the set parameters and the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, determines the main lobe energy at each illumination moment.

[0169] Specifically, in this embodiment of the invention, step C1 may include:

[0170] Based on the radar beam pointing angle and off-axis angle of the current target location at each illumination moment, the first Doppler frequency and the second Doppler frequency at each illumination moment are determined respectively.

[0171] Based on the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, determine the antenna pattern function of the current target location at each illumination moment;

[0172] Based on the antenna pattern function at the current target location, the main lobe energy at each illumination moment is determined.

[0173] In this embodiment, firstly, the first Doppler frequency f at each irradiation moment is calculated according to the following formulas (27) and (28). sr (m) and the second Doppler frequency f st (m):

[0174]

[0175]

[0176] In the formula, θ sr (m) represents the radar beam pointing angle of the current target location at the m-th illumination moment, calculated in step 106, θ. st (m) is the off-axis angle of the current target position point at the mth irradiation moment, calculated in step 106.

[0177] Then, the antenna pattern function at the current target location point at each illumination time is calculated according to the following formula (29):

[0178]

[0179] In the formula, L a Where λ is the azimuth antenna size, λ is the radar operating wavelength, and Wa is the azimuth antenna size. m,0 This is the antenna pattern function.

[0180] Finally, the main lobe energy E at the current target location point at each irradiation time is calculated according to the following formula (30). m,0 :

[0181] E m,0 =Wa m,0 ·Wa m,0

[0182] Step C2: Based on the set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, determine the energy of each ambiguity region corresponding to the current target position at each illumination moment.

[0183] In this embodiment of the invention, step C2 may include:

[0184] Based on the preset number of blur regions in the set parameters and the second Doppler frequency at each irradiation time, the Doppler frequency of each blur region at each irradiation time is determined.

[0185] Based on the Doppler frequency of each blurred region at each illumination moment, the off-axis angle of each blurred region at each illumination moment is determined;

[0186] Based on the off-axis angle of each blurred region and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, the antenna pattern function of each blurred region at each illumination moment is determined respectively.

[0187] Based on the antenna pattern function of each ambiguity region, the energy of each ambiguity region corresponding to the current target location point is determined at each illumination time.

[0188] In this embodiment, the number of blurred regions N is predetermined in step 100. Then, the Doppler frequency f of each blurred region at each illumination time is calculated using the following formula (31). st (m,n):

[0189] f st (m,n)=f st (m)+(nN / 2)·PRF (31)

[0190] In the formula, f st (m) represents the second Doppler frequency, N represents the number of blurred regions, m represents the illumination time, n represents the blurred region number, and PRF represents the pulse repetition frequency.

[0191] Then, the off-axis angle θ of each blurred region at each illumination time is calculated according to the following formula (32). st (m,n):

[0192]

[0193] In the formula, f st (m,n) represents the Doppler frequency of each blurred region at each illumination moment, λ is the radar operating wavelength, and v sat This is the equivalent velocity of the satellite.

[0194] Next, the antenna pattern function Wa of each ambiguous region at each illumination time is calculated using the following formula (33). m,n :

[0195]

[0196] In the formula, θst (m,n) represents the off-axis angle of the nth blurred region at the mth illumination moment, θ sr (m) represents the radar beam pointing angle.

[0197] Finally, the energy E of each blurred region corresponding to the current target location point at each illumination time is calculated according to the following formula (34). m,n :

[0198] E m,n =Wa m,n ·Wa m,n (34)

[0199] In the formula, E m,n This represents the combined gain of the transmitting and receiving antennas for the nth ambiguity region.

[0200] Step C3: Determine the total energy of the main lobe region at the current target location point based on the main lobe region energy at each irradiation moment.

[0201] In this step, the total energy E of the main lobe region at the current target location is calculated according to the following formula (35). main :

[0202]

[0203] In the formula, E m,0 The main lobe energy E at the current target location at each irradiation moment. m,0 .

[0204] Step C4: Based on the energy of each blurred region at each illumination moment, determine the total energy of the blurred region corresponding to the current target location point.

[0205] In this step, the total energy E of the fuzzy region corresponding to the current target location is calculated according to the following formula (36). side :

[0206]

[0207] In the formula, E m,n Let be the energy of the nth blurred region at the mth illumination time.

[0208] Step C5: Determine the azimuth ambiguity of the current target location point based on the total energy of the main lobe region and the total energy of the ambiguity region.

[0209] In this step, the azimuth ambiguity AASR of the current target location can be calculated according to the following formula (37). ij :

[0210] AASR ij =10·lg(Eside / E main (37)

[0211] Therefore, according to step 108, the azimuth ambiguity of each target location point in each working mode can be calculated, and the azimuth ambiguity variation curve for each working mode can be plotted.

[0212] like Figure 3 , Figure 4 As shown, this embodiment of the invention provides an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar. The device embodiment can be implemented through software, hardware, or a combination of both. From a hardware perspective, such as... Figure 3 The diagram shown is a hardware architecture diagram of a computing device housing an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar according to an embodiment of the present invention. Except for... Figure 3 In addition to the processor, memory, network interface, and non-volatile memory shown, the computing device in the embodiment may also include other hardware, such as a forwarding chip responsible for processing packets. Taking software implementation as an example, such as... Figure 4 As shown, as a logical device, it is formed by the CPU of its computing device reading the corresponding computer program from the non-volatile memory into the main memory and running it. This embodiment provides an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar, comprising:

[0213] Acquisition unit 401 is used to acquire the setting parameters of the spaceborne radar;

[0214] The first determining unit 402 is used to perform the following for each working mode: based on the set parameters, determine the motion coordinate parameters of the satellite, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point when the spaceborne radar illuminates the center point of the target scene in the current working mode; wherein, the spaceborne radar is located on the satellite;

[0215] The second determining unit 403 is used to determine the position vector of each target location point set in the target scene based on the set parameters, the pre-determined satellite flight trajectory and the latitude and longitude of the target scene center point;

[0216] The third determining unit 404 is used to determine the illumination time of each target position point by the spaceborne radar based on the set parameters, the position vector of the equivalent rotation point and the position vector of each target position point, and to determine the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time.

[0217] The fourth determining unit 405 is used to determine the azimuth ambiguity of each target position point based on the set parameters and the off-axis angle and radar beam pointing angle of each target position point at each illumination moment, so as to determine the azimuth ambiguity change curve under the current working mode.

[0218] In one embodiment of the present invention, the first determining unit 402 is configured to perform:

[0219] With the Earth's center as the origin, establish the rotating geocentric coordinate system, the stationary geocentric coordinate system, the orbital plane coordinate system, the satellite platform coordinate system, the satellite body coordinate system, and the satellite antenna coordinate system in sequence;

[0220] Based on the set parameters, the motion coordinate parameters of the satellite in the rotating geocentric coordinate system are calculated when the satellite-borne radar illuminates the center point of the target scene; among them, the motion coordinate parameters include the satellite position vector, the satellite velocity vector, and the satellite acceleration vector;

[0221] Based on the set parameters, calculate the position vector of the center point of the target scene in the rotating geocentric coordinate system when the star-borne radar illuminates the center point of the target scene.

[0222] Determine the latitude and longitude of the target scene center point based on the position vector of the target scene center point in the rotating geocentric coordinate system;

[0223] Determine the hybridization factor of the spaceborne radar under the current operating mode;

[0224] Based on the mixing factor, satellite position vector, and the position vector of the target scene center point, determine the position vector of the equivalent rotation point in the current working mode.

[0225] In one embodiment of the present invention, the second determining unit 403 is used to perform:

[0226] Centered on the center point of the target scene, set several target position points at equal intervals along the direction of the satellite's flight trajectory, and set several target position points at equal intervals along the direction perpendicular to the satellite's flight trajectory;

[0227] Based on the set parameters and the latitude and longitude of the center point of the target scene, determine the latitude and longitude of each target location point;

[0228] Based on the latitude and longitude of each target location point, determine the position vector of each target location point set in the target scene.

[0229] In one embodiment of the present invention, the third determining unit 404, when determining the illumination time of each target position point by the spaceborne radar based on set parameters, the position vector of the equivalent rotation point, and the position vector of each target position point, is specifically used for:

[0230] For each target location, execute:

[0231] The simulation time is determined based on the set parameters and the center time of the center point of the target scene illuminated by the spaceborne radar.

[0232] Determine the satellite's position vector in the rotating geocentric coordinate system at this simulation moment;

[0233] Based on the satellite position vector at the simulation moment and the position vector of the current target position point, the off-axis angle between the satellite and the current target position point in the satellite antenna coordinate system is determined;

[0234] Based on the satellite position vector and the position vector of the equivalent rotation point at this simulation moment, the radar beam pointing angle in the satellite antenna coordinate system is determined;

[0235] Determine if the off-axis angle and the radar beam pointing angle are equal; if not, adjust the simulation time and use the adjusted simulation time as the new simulation time, then jump to determine the satellite position vector in the rotating geocentric coordinate system at this simulation time; if yes, then determine this simulation time as the center time of the current target position point illuminated by the spaceborne radar.

[0236] Based on the set parameters and the center time of the satellite-borne radar illuminating the current target location, the illumination time of the satellite-borne radar illuminating the current target location is determined.

[0237] In one embodiment of the present invention, the third determining unit 404, when determining the illumination time of the current target location point by the spaceborne radar based on set parameters and the center time of the spaceborne radar illuminating the current target location point, is specifically used for:

[0238] Based on the set parameters, the azimuth bandwidth is determined;

[0239] Based on the center time of the current target location illuminated by the spaceborne radar, the start and end times of the simulation are determined respectively.

[0240] Based on the start simulation time and the end simulation time, determine the Doppler frequencies corresponding to the start simulation time and the end simulation time, respectively;

[0241] Based on the Doppler frequency corresponding to the start simulation time and the Doppler frequency corresponding to the end simulation time, the Doppler frequency offset from the start simulation time to the end simulation time is determined.

[0242] Determine if the Doppler frequency offset and azimuth bandwidth are equal; if not, adjust the start and end simulation times, and use the adjusted start and end simulation times as the new start and end simulation times, then jump to execute the process based on the start and end simulation times to determine the corresponding Doppler frequencies; if yes, then determine the start and end simulation times as the target start and target end times for the spaceborne radar to illuminate the current target location point.

[0243] Based on the target's start and end times, determine the illumination time for the spaceborne radar to illuminate the current target's location.

[0244] In one embodiment of the present invention, the fourth determining unit 405, when determining the azimuth ambiguity of each target position point based on set parameters and the off-axis angle and radar beam pointing angle of each target position point at each illumination moment, is specifically used for:

[0245] For each target location, execute:

[0246] Based on the set parameters and the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, the main lobe energy at each illumination moment is determined.

[0247] Based on the set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, the energy of each ambiguity region corresponding to the current target position at each illumination moment is determined.

[0248] Based on the main lobe energy at each irradiation moment, determine the total main lobe energy at the current target location.

[0249] Based on the energy of each blurred region at each illumination moment, determine the total energy of the blurred region corresponding to the current target location point;

[0250] Based on the total energy of the main lobe region and the total energy of the ambiguity region of the current target location, the azimuth ambiguity of the current target location is determined.

[0251] In one embodiment of the present invention, the fourth determining unit 405, when determining the main lobe energy at each illumination moment based on set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, is specifically used for:

[0252] Based on the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, the first Doppler frequency and the second Doppler frequency at each illumination moment are determined respectively.

[0253] Based on the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, determine the antenna pattern function of the current target location at each illumination moment;

[0254] Based on the antenna pattern function at the current target location, the main lobe energy at each illumination moment is determined.

[0255] In one embodiment of the present invention, the fourth determining unit 405, when performing the task of determining the energy of each ambiguous region corresponding to the current target position at each illumination moment based on set parameters and the radar beam pointing angle and off-axis angle of the current target position at each illumination moment, is specifically used for:

[0256] Based on the preset number of blur regions in the set parameters and the second Doppler frequency at each irradiation time, the Doppler frequency of each blur region at each irradiation time is determined.

[0257] Based on the Doppler frequency of each blurred region at each illumination moment, the off-axis angle of each blurred region at each illumination moment is determined;

[0258] Based on the off-axis angle of each blurred region and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, the antenna pattern function of each blurred region at each illumination moment is determined respectively.

[0259] Based on the antenna pattern function of each ambiguity region, the energy of each ambiguity region corresponding to the current target location point is determined at each illumination time.

[0260] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar. In other embodiments of the present invention, an azimuth ambiguity calculation device for a spaceborne synthetic aperture radar may include more or fewer components than illustrated, or combine some components, or split some components, or arrange different components. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0261] The information interaction and execution process between the modules in the above-mentioned device are based on the same concept as the method embodiment of the present invention, and the specific details can be found in the description of the method embodiment of the present invention, and will not be repeated here.

[0262] This invention also provides a computing device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements a method for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar according to any embodiment of this invention.

[0263] This invention also provides a computer-readable storage medium storing a computer program. When executed by a processor, the computer program causes the processor to perform an azimuth ambiguity calculation method for a spaceborne synthetic aperture radar according to any embodiment of this invention.

[0264] Specifically, a system or apparatus equipped with a storage medium may be provided, on which software program code implementing the functions of any of the embodiments described above is stored, and the computer (or CPU or MPU) of the system or apparatus may read and execute the program code stored in the storage medium.

[0265] In this case, the program code read from the storage medium can itself implement the function of any of the above embodiments, and therefore the program code and the storage medium storing the program code constitute part of the present invention.

[0266] Examples of storage media used to provide program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer via a communication network.

[0267] Furthermore, it should be clear that not only can the program code read by the computer be executed, but also the operating system or other components operating on the computer can be instructed based on the program code to perform some or all of the actual operations, thereby realizing the function of any of the embodiments described above.

[0268] Furthermore, it is understood that the program code read from the storage medium is written to the memory set in the expansion board inserted into the computer or to the memory set in the expansion module connected to the computer. Then, based on the instructions of the program code, the CPU or other components installed on the expansion board or expansion module execute some and all of the actual operations, thereby realizing the function of any of the above embodiments.

[0269] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0270] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as ROM, RAM, magnetic disk, or optical disk.

[0271] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar, characterized in that, include: Obtain the setting parameters of the spaceborne radar; For each working mode, the following steps are performed: Based on the set parameters, determine the satellite's motion coordinate parameters, the position vector of the target scene center point, the latitude and longitude of the target scene center point, and the position vector of the equivalent rotation point when the spaceborne radar illuminates the target scene center point in the current working mode; wherein, the spaceborne radar is located on the satellite; Based on the set parameters, the pre-determined satellite trajectory, and the latitude and longitude of the center point of the target scene, the position vector of each target location point set in the target scene is determined; Based on the set parameters, the position vector of the equivalent rotation point, and the position vector of each target position point, the illumination time of the spaceborne radar illuminating each target position point is determined, and the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time are determined. Based on the set parameters and the off-axis angle and radar beam pointing angle of each target location at each illumination moment, the azimuth ambiguity of each target location is determined, so as to determine the azimuth ambiguity change curve under the current working mode.

2. The method according to claim 1, characterized in that, The step of determining the satellite's motion coordinate parameters, the position vector of the target scene's center point, the latitude and longitude of the target scene's center point, and the position vector of the equivalent rotation point when the satellite-borne radar illuminates the target scene's center point under the current operating mode, based on the set parameters, includes: With the Earth's center as the origin, establish the rotating geocentric coordinate system, the stationary geocentric coordinate system, the orbital plane coordinate system, the satellite platform coordinate system, the satellite body coordinate system, and the satellite antenna coordinate system in sequence; Based on the set parameters, the motion coordinate parameters of the satellite in the rotating geocentric coordinate system are calculated when the satellite-borne radar illuminates the center point of the target scene; wherein, the motion coordinate parameters include the satellite position vector, the satellite velocity vector, and the satellite acceleration vector; Based on the set parameters, calculate the position vector of the center point of the target scene in the rotating geocentric coordinate system when the spaceborne radar illuminates the center point of the target scene. Based on the position vector of the center point of the target scene in the rotating geocentric coordinate system, determine the latitude and longitude of the center point of the target scene. Determine the hybridization factor of the spaceborne radar under the current operating mode; Based on the mixing factor, the satellite position vector, and the position vector of the target scene center point, the position vector of the equivalent rotation point in the current working mode is determined.

3. The method according to claim 1, characterized in that, The determination of the position vectors of each target location point set in the target scene based on the set parameters, the pre-determined satellite trajectory, and the latitude and longitude of the target scene center point includes: Centered on the center point of the target scene, several target position points are set at equal intervals along the direction of the satellite's flight trajectory, and several target position points are set at equal intervals along the direction perpendicular to the direction of the satellite's flight trajectory. Based on the set parameters and the latitude and longitude of the center point of the target scene, the latitude and longitude of each target location point are determined; Based on the latitude and longitude of each target location point, determine the position vector of each target location point set in the target scene.

4. The method according to claim 2, characterized in that, The process of determining the illumination time for each target location point by the spaceborne radar based on the set parameters, the position vector of the equivalent rotation point, and the position vector of each target location point includes: For each target location, execute: Based on the set parameters and the center time of the center point of the target scene illuminated by the spaceborne radar, the simulation time is determined; Determine the satellite's position vector in the rotating geocentric coordinate system at this simulation moment; Based on the satellite position vector at the simulation moment and the position vector of the current target position point, the off-axis angle from the satellite to the current target position point in the satellite antenna coordinate system is determined; Based on the satellite position vector at the simulation moment and the position vector of the equivalent rotation point, the radar beam pointing angle in the satellite antenna coordinate system is determined; Determine whether the off-axis angle and the radar beam pointing angle are equal; if not, adjust the simulation time and use the adjusted simulation time as the new simulation time, and jump to execute the step of determining the satellite position vector in the rotating geocentric coordinate system at the simulation time; if yes, determine the simulation time as the center time of the current target position point illuminated by the spaceborne radar. Based on the set parameters and the center time of the satellite-borne radar illuminating the current target location, the illumination time of the satellite-borne radar illuminating the current target location is determined.

5. The method according to claim 4, characterized in that, The step of determining the illumination time of the current target location point by the spaceborne radar based on the set parameters and the center time of the illumination of the current target location point by the spaceborne radar includes: Based on the set parameters, the azimuth bandwidth is determined; Based on the center time of the current target location illuminated by the spaceborne radar, the start and end times of the simulation are determined respectively. Based on the start simulation time and the end simulation time, determine the Doppler frequencies corresponding to the start simulation time and the end simulation time, respectively; Based on the Doppler frequency corresponding to the start simulation time and the Doppler frequency corresponding to the end simulation time, the Doppler frequency offset from the start simulation time to the end simulation time is determined. Determine whether the Doppler frequency offset and the azimuth bandwidth are equal; if not, adjust the start simulation time and the end simulation time, and use the adjusted start simulation time and end simulation time as the new start simulation time and end simulation time, and jump to execute the step of determining the Doppler frequency corresponding to the start simulation time and the end simulation time based on the start simulation time and the end simulation time respectively; if yes, determine the start simulation time and the end simulation time as the target start time and target end time for the spaceborne radar to illuminate the current target position point respectively; Based on the target start time and the target end time, the illumination time of the spaceborne radar illuminating the current target location is determined.

6. The method according to claim 1, characterized in that, The determination of the azimuth ambiguity of each target location point based on the set parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment includes: For each target location, execute: Based on the set parameters and the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, the main lobe energy at each illumination moment is determined. Based on the set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, the energy of each ambiguity region corresponding to the current target position at each illumination moment is determined. Based on the main lobe energy at each irradiation moment, determine the total main lobe energy at the current target location. Based on the energy of each blurred region at each illumination moment, determine the total energy of the blurred region corresponding to the current target location point; Based on the total energy of the main lobe region and the total energy of the ambiguity region of the current target location, the azimuth ambiguity of the current target location is determined.

7. The method according to claim 6, characterized in that, The method of determining the main lobe energy at each illumination moment based on the set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment includes: Based on the radar beam pointing angle and off-axis angle of the current target location at each illumination moment, the first Doppler frequency and the second Doppler frequency at each illumination moment are determined respectively. Based on the off-axis angle and radar beam pointing angle of the current target location at each illumination moment, determine the antenna pattern function of the current target location at each illumination moment; Based on the antenna pattern function of the current target location, determine the main lobe energy at each illumination moment; The determination of the energy of each blurred region corresponding to the current target position at each illumination moment, based on the set parameters and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, includes: Based on the preset number of blur regions in the set parameters and the second Doppler frequency at each irradiation time, the Doppler frequency of each blur region at each irradiation time is determined. Based on the Doppler frequency of each blurred region at each illumination moment, the off-axis angle of each blurred region at each illumination moment is determined; Based on the off-axis angle of each blurred region and the off-axis angle and radar beam pointing angle of the current target position at each illumination moment, the antenna pattern function of each blurred region at each illumination moment is determined respectively. Based on the antenna pattern function of each ambiguity region, the energy of each ambiguity region corresponding to the current target location point is determined at each illumination time.

8. A device for calculating the azimuth ambiguity of a spaceborne synthetic aperture radar, characterized in that, include: The acquisition unit is used to acquire the setting parameters of the spaceborne radar; The first determining unit is configured to perform the following for each working mode: based on the set parameters, determine the motion coordinate parameters of the satellite when the spaceborne radar illuminates the center point of the target scene, the position vector of the center point of the target scene, the latitude and longitude of the center point of the target scene, and the position vector of the equivalent rotation point of the center point of the target scene; wherein, the spaceborne radar is located on the satellite; The second determining unit is used to determine the position vector of each target location point set in the target scene based on the set parameters, the pre-determined flight trajectory of the satellite and the latitude and longitude of the center point of the target scene; The third determining unit is used to determine the illumination time of the spaceborne radar illuminating each target position point based on the set parameters, the position vector of the equivalent rotation point and the position vector of each target position point, and to determine the off-axis angle and radar beam pointing angle of the current target position point at each illumination moment within the illumination time. The fourth determining unit is used to determine the azimuth ambiguity of each target location point based on the set parameters and the off-axis angle and radar beam pointing angle of each target location point at each illumination moment, so as to determine the azimuth ambiguity change curve under the current working mode.

9. A computing device comprising a memory and a processor, wherein the memory stores a computer program, and the processor, when executing the computer program, implements the method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the method of any one of claims 1-7.

Images