Multi-channel sea clutter modeling method and system for spaceborne dual-base radar

Abstract

This invention provides a method and system for modeling sea clutter in a multi-channel spaceborne bistatic radar, including: solving the spaceborne-sea geometric relationship; calculating the two-way radiation pattern of the spaceborne bistatic radar antenna; modeling the time-varying motion of the sea surface; calculating the bistatic scattering coefficient of sea clutter; and synthesizing the multi-channel sea clutter echo of the spaceborne bistatic radar. This invention can achieve high-precision modeling of multi-channel sea clutter for spaceborne bistatic radar under different bistatic configurations and system parameters, overcoming the problems of existing models that do not consider the internal motion of multi-channel sea clutter in spaceborne bistatic radar, and do not consider the influence of different polarization modes and azimuth bistatic angles on the bistatic sea clutter scattering coefficient.

Description

Technical Field

[0001] This invention relates to the field of radar clutter modeling technology, specifically to a method and system for multi-channel sea clutter modeling of a spaceborne dual-base radar. Background Technology

[0002] With the development of aerospace science and technology, the application of absorbing materials and novel structural designs have significantly reduced the radar cross-section (RCS) of aircraft targets, severely impacting the target detection capabilities of traditional spaceborne monostatic early warning radars. To address this issue, based on the fluctuating characteristics of the target's RCS under bistatic viewing angles, a bistatic detection system that effectively increases the RCS by using a large observation angle will become an important development direction for detecting weak targets in the air. When spaceborne bistatic radars operate in a look-down mode, the high-speed movement of the transceiver platform causes broadening of the clutter Doppler spectrum, easily submerging the target echo in the expanded clutter echo, severely affecting the target's output signal-to-clutter-to-noise ratio (SNR). Therefore, effective clutter suppression is crucial for reliable detection of moving targets. Compared to spaceborne monostatic radars, spaceborne bistatic radar clutter is affected by the separate transceiver configuration, with clutter intensity lines, Doppler lines, and spatial cone angle lines not coinciding, leading to severe clutter Doppler frequency-spatial frequency dual range dependence, thus worsening the bistatic clutter suppression effect. Therefore, in order to effectively realize the clutter characteristic analysis of spaceborne bistatic radar, it is first necessary to accurately model the clutter of spaceborne bistatic radar.

[0003] To address this problem, scholars both domestically and internationally have proposed various bistatic radar clutter modeling techniques. For example, some scholars have analyzed the space-ground geometry under a spaceborne bistatic radar system, obtaining an analytical solution for the equidistant loop of spaceborne bistatic clutter based on the Earth's spherical parametric equations, and establishing a space-time model of spaceborne bistatic radar clutter. Other scholars have proposed a method for solving the equidistant loop of spaceborne bistatic clutter based on the bistatic equidistant ellipsoidal parametric equations, reducing the computational complexity of the model. Still others have established a space-aircraft bistatic clutter model and analyzed its suppression performance under different configurations. However, the above studies do not consider the internal motion of the clutter, and therefore are only applicable to land clutter. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for multi-channel sea clutter modeling in spaceborne bistatic radar.

[0005] A method for modeling sea clutter in a spaceborne bistatic radar according to the present invention includes the following steps:

[0006] Step S1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system.

[0007] Step S2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, and the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward angle and azimuth of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna.

[0008] Step S3: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system, and calculate the motion state of the clutter scattering point;

[0009] Step S4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, and the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode.

[0010] Step S5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna, the motion state of the clutter scattering point, and the bistatic scattering coefficient of the sea clutter, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point to obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

[0011] Preferably, the coordinates of the clutter scattering point in the Earth's inertial coordinate system in step S1 are obtained by the following method:

[0012] x C-i =Λ1z C-i +Λ2

[0013] y C-i =Λ3z C-i +Λ4

[0014]

[0015] Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method:

[0016]

[0017]

[0018]

[0019]

[0020] Where, x T-i yT-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. T The slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

[0021] Preferably, the two-way radiation pattern of the spaceborne bistatic radar antenna in step S2 is obtained by the following method:

[0022]

[0023] in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

[0024] Preferably, the motion state of the sea clutter scattering point in step S3 is obtained by the following method:

[0025] The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively

[0026]

[0027]

[0028]

[0029] Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let i be the wave number of the i-th wave. A i,j Let i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, and Δδ represents the wave direction spectrum. wave To divide the direction of wave movement into intervals, φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction.

[0030] Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively

[0031]

[0032]

[0033] Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

[0034] Preferably, the sea clutter biradial scattering coefficients in step S4 are obtained by the following method:

[0035]

[0036] Where α and β can be H and V, respectively, representing horizontal polarization and vertical polarization, and k radar Let θ be the radar wave number. in For the incident ray to rub against the ground angle, θ sc Let η be the scattering angle, γ be the azimuth bibase angle, η be the local surface dip angle, ξ be the local tilt direction angle, and P(η) and P(ξ) be the probability density functions of the surface dip angle η and the tilt direction angle ξ, respectively. It is obtained by the following method:

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044] Where ε is the dielectric constant of the scattering surface, and These are the empirical backscattering coefficients for HH and VV polarization, respectively.

[0045] The local incident ray grazing angle θ at the clutter scattering point in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) is obtained by the following method:

[0046] The coordinates of the transmitter and receiver in the tilted local coordinate system are respectively

[0047]

[0048]

[0049]

[0050] Among them, M i-l and These are the transformation matrix and coordinate axis translation vector from the Earth's inertial coordinate system to the local East-North-Sky coordinate system, respectively. These are the coordinates of the transmitter in the Earth's inertial coordinate system. Let x be the coordinates of the receiver in the Earth's inertial coordinate system. T-inl (η,ξ), y T-inl (η,ξ) and z T-inl (η,ξ) are respectively The three-axis coordinates, x R-inl (η,ξ), y R-inl (η,ξ) and z R-inl (η,ξ) are respectively By using the three-axis coordinates, the local incident ray grazing angle θ at the clutter scattering point can be obtained. in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) are respectively

[0051]

[0052]

[0053]

[0054] Preferably, the spaceborne bistatic radar multichannel sea clutter echo signal in step S5 is obtained by the following method:

[0055] Assume that the i-th clutter scattering point in the equidistant ring corresponding to the p-th range ambiguity in the r-th range cell is C. r,p,i The downward viewing angles of this clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively and The azimuth angles are θ az-v-T,r,p,i and θ az-v-R,r,p,i The instantaneous velocity vectors are respectively and The lower viewing angles in the transmit / receive antenna panel coordinate system are respectively and The azimuth angles are θ az-a-T,r,p,i and θ az-a-R,r,p,i Then, in the nth receiving channel and under the kth pulse, the clutter scattering point C r,p,i The corresponding instantaneous two-way slant range for transmission and reception is

[0056]

[0057] Among them, R T0,r,p,i and R R0,r,p,i These are clutter scattering points C r,p,iThe corresponding initial transmit slant range and initial receive slant range, v s-T and v s-R T represents the speeds of the transmitter and receiver, respectively. PRT d is the pulse repetition time. n Let be the distance between the position of the nth azimuth receiving channel and the origin of the coordinate system of the receiving antenna panel. For the receiving antenna panel coordinate system The axis and the velocity coordinate system of the receiving satellite The included angle of the axis.

[0058] After range pulse compression processing, the clutter echo signal received by the nth azimuth receiving channel from the rth range cell is:

[0059]

[0060]

[0061] Where P1 and P2 are the lower and upper bounds of the distance ambiguity number, respectively, and N C Let B be the number of blocks for each clutter equidistant ring, B be the radar bandwidth, c be the speed of light, and A be the number of blocks. r,p,i C is the distance to the clutter scattering point after compression. r,p,i The corresponding signal amplitude is calculated using radar equations, ω r,p,i C is the clutter scattering point. r,p,i The corresponding directional pattern weighting coefficients.

[0062] A spaceborne bistatic radar multi-channel sea clutter modeling system according to the present invention includes the following modules:

[0063] Module M1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system.

[0064] Module M2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna.

[0065] Module M3: Based on the coordinates of the clutter scattering points in the Earth's inertial coordinate system obtained in Module M1, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system to calculate the motion state of the clutter scattering points.

[0066] Module M4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode.

[0067] Module M5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna obtained in Module M2, the motion state of the clutter scattering point obtained in Module M3, and the sea clutter bistatic scattering coefficient obtained in Module M4, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point, and obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

[0068] Preferably, the coordinates of the clutter scattering point in module M1 in the Earth's inertial coordinate system are obtained by the following method:

[0069] x C-i =Λ1z C-i +Λ2

[0070] y C-i =Λ3z C-i +Λ4

[0071]

[0072] Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method:

[0073]

[0074]

[0075]

[0076]

[0077] Where, x T-i y T-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. TThe slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

[0078] Preferably, the two-way radiation pattern of the spaceborne bistatic radar antenna in module M2 is obtained by the following method:

[0079]

[0080] in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

[0081] Preferably, the motion state of the sea clutter scattering point in module M3 is obtained by the following method:

[0082] The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively

[0083]

[0084]

[0085]

[0086] Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let i be the wave number of the i-th wave. A i,jLet i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, Δδwave represents the wave motion direction division interval, and φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction.

[0087] Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively

[0088]

[0089]

[0090] Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

[0091] Compared with the prior art, the present invention has the following beneficial effects:

[0092] 1. This invention can model the internal motion of sea clutter in multi-channel spaceborne bistatic radar, overcoming the problem that existing models do not consider the internal motion of sea clutter in multi-channel spaceborne bistatic radar.

[0093] 2. This invention can calculate the scattering coefficient of bistatic clutter under different polarization modes, incident angles, scattering angles, and azimuth bistatic angles, overcoming the problem that existing models do not consider the influence of different polarization modes and azimuth bistatic angles on the scattering coefficient of bistatic clutter. Attached Figure Description

[0094] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0095] Figure 1 This is a schematic diagram of the multi-channel sea clutter modeling method for spaceborne bistatic radar disclosed in this invention;

[0096] Figure 2 The simulated spaceborne bistatic radar sea clutter range-Doppler spectrum obtained in Example 1;

[0097] Figure 3 The simulated spaceborne bistatic radar sea clutter interferometric phase diagram obtained in Example 1;

[0098] Figure 4 The simulated spaceborne bistatic radar sea clutter range-Doppler spectrum obtained in Example 2;

[0099] Figure 5 The image shows the simulated sea clutter interferometric phase diagram of a spaceborne bistatic radar obtained in Example 2. Detailed Implementation

[0100] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0101] This invention discloses a multi-channel sea clutter modeling method for spaceborne bistatic radar, the flowchart of which is shown below. Figure 1 As shown, the method includes the following steps:

[0102] Step S1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system.

[0103] Step S2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Step S1, and the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna.

[0104] Step S3: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Step S1, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system and calculate the motion state of the clutter scattering point.

[0105] Step S4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Step S1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode.

[0106] Step S5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna obtained in step S2, the motion state of the clutter scattering point obtained in step S3, and the sea clutter bistatic scattering coefficient obtained in step S4, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point to obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

[0107] The coordinates of the clutter scattering point in step S1 in the Earth's inertial coordinate system are obtained by the following method:

[0108] x C-i =Λ1z C-i +Λ2

[0109] y C-i =Λ3z C-i +Λ4

[0110]

[0111] Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method:

[0112]

[0113]

[0114]

[0115]

[0116] Where, x T-i y T-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. TThe slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

[0117] The two-way radiation pattern of the spaceborne bistatic radar antenna in step S2 is obtained by the following method:

[0118]

[0119] in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

[0120] The motion state of the sea clutter scattering point in step S3 is obtained by the following method:

[0121] The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively

[0122]

[0123]

[0124]

[0125] Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let i be the wave number of the i-th wave. A i,jLet i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, and Δδ represents the wave direction spectrum. wave To divide the direction of wave movement into intervals, φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction.

[0126] Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively

[0127]

[0128]

[0129] Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

[0130] The sea clutter biradial scattering coefficients in step S4 are obtained by the following method:

[0131]

[0132] Where α and β can be H and V, respectively, representing horizontal polarization and vertical polarization, and k radar Let θ be the radar wave number. in For the incident ray to rub against the ground angle, θ scLet η be the scattering angle, γ be the azimuth bibase angle, η be the local surface dip angle, ξ be the local tilt direction angle, and P(η) and P(ξ) be the probability density functions of the surface dip angle η and the tilt direction angle ξ, respectively. It is obtained by the following method:

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] Where ε is the dielectric constant of the scattering surface, and These are the empirical backscattering coefficients for HH and VV polarization, respectively.

[0141] The local incident ray grazing angle θ at the clutter scattering point in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) is obtained by the following method:

[0142] The coordinates of the transmitter and receiver in the tilted local coordinate system are respectively

[0143]

[0144]

[0145]

[0146] Among them, M i-l and These are the transformation matrix and coordinate axis translation vector from the Earth's inertial coordinate system to the local East-North-Sky coordinate system, respectively. These are the coordinates of the transmitter in the Earth's inertial coordinate system. Let x be the coordinates of the receiver in the Earth's inertial coordinate system. T-inl (η,ξ), y T-inl (η,ξ) and z T-inl (η,ξ) are respectively The three-axis coordinates, x R-inl (η,ξ), yR-inl (η,ξ) and z R-inl (η,ξ) are respectively By using the three-axis coordinates, the local incident ray grazing angle θ at the clutter scattering point can be obtained. in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) are respectively

[0147]

[0148]

[0149]

[0150] The multi-channel sea clutter echo signal of the spaceborne bistatic radar in step S5 is obtained by the following method:

[0151] Assume that the i-th clutter scattering point in the equidistant ring corresponding to the p-th range ambiguity in the r-th range cell is C. r,p,i The downward viewing angles of this clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively and The azimuth angles are θ az-v-T,r,p,i and θ az-v-R,r,p,i The instantaneous velocity vectors are respectively and The lower viewing angles in the transmit / receive antenna panel coordinate system are respectively and The azimuth angles are θ az-a-T,r,p,i and θ az-a-R,r,p,i Then, in the nth receiving channel and under the kth pulse, the clutter scattering point C r,p,i The corresponding instantaneous two-way slant range for transmission and reception is

[0152]

[0153] Among them, R T0,r,p,i and R R0,r,p,i These are clutter scattering points C r,p,i The corresponding initial transmit slant range and initial receive slant range, v s-T and v s-R T represents the speeds of the transmitter and receiver, respectively. PRT d is the pulse repetition time. n Let be the distance between the position of the nth azimuth receiving channel and the origin of the coordinate system of the receiving antenna panel. For the receiving antenna panel coordinate system The axis and the velocity coordinate system of the receiving satellite The included angle of the axis.

[0154] After range pulse compression processing, the clutter echo signal received by the nth azimuth receiving channel from the rth range cell is:

[0155]

[0156]

[0157] Where P1 and P2 are the lower and upper bounds of the distance ambiguity number, respectively, and N C Let B be the number of blocks for each clutter equidistant ring, B be the radar bandwidth, c be the speed of light, and A be the number of blocks. r,p,i C is the distance to the clutter scattering point after compression. r,p,i The corresponding signal amplitude is calculated using radar equations, ω r,p,i C is the clutter scattering point. r,p,i The corresponding directional pattern weighting coefficients.

[0158] Furthermore, the multi-channel sea clutter modeling method for spaceborne bistatic radar provided in this invention was simulated using the MATLAB R2019b simulation platform.

[0159] The simulation system parameters used in Example 1 are as follows: The launching satellite orbital altitude is 508 km, orbital inclination is 45°, perigee argument is 0°, right ascension of the ascending node is 0°, true anomaly is 2°, beam center downward angle is 45°, azimuth is 90°; the receiving satellite orbital altitude is 508 km, orbital inclination is 0°, perigee argument is 0°, right ascension of the ascending node is 0°, anomaly is -2°, beam center downward angle is 45.1°, azimuth is 89.6°, carrier frequency is 1.26 GHz, bandwidth is 3 MHz, and sampling frequency... The frequency is 3.6MHz, the average transmit power is 4kW, the number of receive channels is 16, the transmit antenna elevation dimension is 2m, the azimuth dimension is 50m, the receive antenna elevation dimension is 2m, the azimuth dimension is 50m, the installation tilt angle of both transmit and receive antennas is 45°, the system noise figure is 2dB, the system loss is 8dB, the transmit is unweighted, the receive is weighted at 20dB in the elevation dimension and 40dB in the azimuth dimension, the PRF is 3000Hz, the accumulation time is 40ms, the polarization is HH polarization, and the sea state is 6.

[0160] The simulation system parameters used in Example 2 are as follows: The launching satellite's orbital altitude is 508 km, orbital inclination is 135°, perigee argument is 0°, right ascension of the ascending node is 0°, true anomaly is 11.7°, beam center downward angle is 45°, and azimuth is 90°. The receiving satellite's orbital altitude is 508 km, orbital inclination is 0°, perigee argument is 0°, right ascension of the ascending node is 0°, anomaly is -11.7°, beam center downward angle is 45.3°, azimuth is 89.8°, carrier frequency is 1.26 GHz, and bandwidth is 3 MHz. The sampling frequency is 3.6MHz, the average transmit power is 4kW, the number of receive channels is 16, the transmit antenna elevation dimension is 2m and the azimuth dimension is 50m, the receive antenna elevation dimension is 2m and the azimuth dimension is 50m, the installation tilt angle of both the transmit and receive antennas is 45°, the system noise figure is 2dB, the system loss is 8dB, the transmit signal is unweighted, the receive signal is weighted at 20dB in the elevation dimension and 40dB in the azimuth dimension, the PRF is 3000Hz, the accumulation time is 40ms, the polarization is HH polarization, and the sea state is 6.

[0161] The simulated spaceborne bistatic radar sea clutter range-Doppler spectrum obtained according to Example 1 is as follows: Figure 2 As shown, the interferometric phase diagram between the echo data from the first azimuth receiving channel and the fourth azimuth receiving channel is as follows: Figure 3 As shown. The simulated spaceborne bistatic radar sea clutter range-Doppler spectrum obtained according to Example 2 is as follows. Figure 4 As shown, the interferometric phase diagram between the echo data from the first azimuth receiving channel and the fourth azimuth receiving channel is as follows: Figure 5 As shown in the figure, the results demonstrate that this invention can achieve high-precision modeling of multi-channel sea clutter for spaceborne bistatic radar under different bistatic configurations and system parameters.

[0162] The present invention also provides a spaceborne bistatic radar multi-channel sea clutter modeling system. Those skilled in the art can implement the spaceborne bistatic radar multi-channel sea clutter modeling system by executing the steps of the spaceborne bistatic radar multi-channel sea clutter modeling method. That is, the spaceborne bistatic radar multi-channel sea clutter modeling method can be understood as a preferred embodiment of the spaceborne bistatic radar multi-channel sea clutter modeling system.

[0163] The spaceborne dual-base radar multi-channel sea clutter modeling system includes the following modules:

[0164] Module M1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system.

[0165] Module M2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna.

[0166] Module M3: Based on the coordinates of the clutter scattering points in the Earth's inertial coordinate system obtained in Module M1, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system to calculate the motion state of the clutter scattering points.

[0167] Module M4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode.

[0168] Module M5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna obtained in Module M2, the motion state of the clutter scattering point obtained in Module M3, and the sea clutter bistatic scattering coefficient obtained in Module M4, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point, and obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

[0169] The coordinates of the clutter scattering point in module M1 in the Earth's inertial coordinate system are obtained by the following method:

[0170] x C-i =Λ1z C-i +Λ2

[0171] y C-i =Λ3z C-i +Λ4

[0172]

[0173] Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method:

[0174]

[0175]

[0176]

[0177]

[0178] Where, x T-iy T-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. T The slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

[0179] The two-way radiation pattern of the spaceborne bistatic radar antenna in module M2 is obtained by the following method:

[0180]

[0181] in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

[0182] The motion state of the sea clutter scattering point in module M3 is obtained by the following method:

[0183] The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively

[0184]

[0185]

[0186]

[0187] Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let i be the wave number of the i-th wave. A i,j Let i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, and Δδ represents the wave direction spectrum. wave To divide the direction of wave movement into intervals, φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction.

[0188] Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively

[0189]

[0190]

[0191] Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

[0192] The sea clutter biradial scattering coefficients in module M4 are obtained by the following method:

[0193]

[0194] Where α and β can be H and V, respectively, representing horizontal polarization and vertical polarization, and k radar Let θ be the radar wave number. in For the incident ray to rub against the ground angle, θ sc Let η be the scattering angle, γ be the azimuth bibase angle, η be the local surface dip angle, ξ be the local tilt direction angle, and P(η) and P(ξ) be the probability density functions of the surface dip angle η and the tilt direction angle ξ, respectively. It is obtained by the following method:

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202] Where ε is the dielectric constant of the scattering surface, and These are the empirical backscattering coefficients for HH and VV polarization, respectively.

[0203] The local incident ray grazing angle θ at the clutter scattering point in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) is obtained by the following method:

[0204] The coordinates of the transmitter and receiver in the tilted local coordinate system are respectively

[0205]

[0206]

[0207]

[0208] Among them, M i-l and These are the transformation matrix and coordinate axis translation vector from the Earth's inertial coordinate system to the local East-North-Sky coordinate system, respectively. These are the coordinates of the transmitter in the Earth's inertial coordinate system. Let x be the coordinates of the receiver in the Earth's inertial coordinate system. T-inl (η,ξ), y T-inl (η,ξ) and z T-inl (η,ξ) are respectively The three-axis coordinates, x R-inl (η,ξ), y R-inl (η,ξ) and z R-inl (η,ξ) are respectively By using the three-axis coordinates, the local incident ray grazing angle θ at the clutter scattering point can be obtained. in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) are respectively

[0209]

[0210]

[0211]

[0212] The multi-channel sea clutter echo signal of the spaceborne bistatic radar in module M5 is obtained by the following method:

[0213] Assume that the i-th clutter scattering point in the equidistant ring corresponding to the p-th range ambiguity in the r-th range cell is C. r,p,i The downward viewing angles of this clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively and The azimuth angles are θ az-v-T,r,p,i and θ az-v-R,r,p,i The instantaneous velocity vectors are respectively and The lower viewing angles in the transmit / receive antenna panel coordinate system are respectively and The azimuth angles are θ az-a-T,r,p,i and θ az-a-R,r,p,i Then, in the nth receiving channel and under the kth pulse, the clutter scattering point C r,p,i The corresponding instantaneous two-way slant range for transmission and reception is

[0214]

[0215] Among them, R T0,r,p,i and R R0,r,p,i These are clutter scattering points C r,p,iThe corresponding initial transmit slant range and initial receive slant range, v s-T and v s-R T represents the speeds of the transmitter and receiver, respectively. PRT d is the pulse repetition time. n Let be the distance between the position of the nth azimuth receiving channel and the origin of the coordinate system of the receiving antenna panel. For the receiving antenna panel coordinate system The axis and the velocity coordinate system of the receiving satellite The included angle of the axis.

[0216] After range pulse compression processing, the clutter echo signal received by the nth azimuth receiving channel from the rth range cell is:

[0217]

[0218]

[0219] Where P1 and P2 are the lower and upper bounds of the distance ambiguity number, respectively, and N C Let B be the number of blocks for each clutter equidistant ring, B be the radar bandwidth, c be the speed of light, and A be the number of blocks. r,p,i C is the distance to the clutter scattering point after compression. r,p,i The corresponding signal amplitude is calculated using radar equations, ω r,p,i C is the clutter scattering point. r,p,i The corresponding directional pattern weighting coefficients.

[0220] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0221] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for modeling sea clutter in a spaceborne bistatic radar using multiple channels, characterized in that, Includes the following steps: Step S1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system. Step S2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, and the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward angle and azimuth of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna. Step S3: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system, and calculate the motion state of the clutter scattering point; Step S4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system, and the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode. Step S5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna, the motion state of the clutter scattering point, and the bistatic scattering coefficient of the sea clutter, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point to obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

2. The method for multi-channel sea clutter modeling of spaceborne bistatic radar according to claim 1, characterized in that, The coordinates of the clutter scattering point in the Earth's inertial coordinate system are obtained by the following method: x C-i =Λ1z C-i +Λ2 y C-i =Λ3z C-i +Λ4 Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method: Where, x T-i y T-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. T The slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

3. The method for multi-channel sea clutter modeling of spaceborne bistatic radar according to claim 1, characterized in that, The two-way radiation pattern of the spaceborne bistatic radar antenna is obtained by the following method: in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

4. The method for multi-channel sea clutter modeling of spaceborne bistatic radar according to claim 1, characterized in that, The motion state of the sea clutter scattering point is obtained by the following method: The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let k be the wave number of the i-th wave. i =ω i 2 / g, A i,j Let i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, Δδwave represents the wave motion direction division interval, and φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction; Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

5. The method for multi-channel sea clutter modeling of a spaceborne bistatic radar according to claim 1, characterized in that, The sea clutter biradial scattering coefficients are obtained by the following method: Where α and β can be H and V, respectively, representing horizontal polarization and vertical polarization, and k radar Let θ be the radar wave number. in For the incident ray to rub the ground angle, θ sc Let η be the scattering angle, γ be the azimuth bibase angle, η be the local surface dip angle, ξ be the local tilt direction angle, and P(η) and P(ξ) be the probability density functions of the surface dip angle η and the tilt direction angle ξ, respectively. It is obtained by the following method: Where ε is the dielectric constant of the scattering surface, and These are the empirical backscattering coefficients for HH polarization and VV polarization, respectively; The local incident ray grazing angle θ at the clutter scattering point in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) is obtained by the following method: The coordinates of the transmitter and receiver in the tilted local coordinate system are respectively Among them, M i-l and These are the transformation matrix and coordinate axis translation vector from the Earth's inertial coordinate system to the local East-North-Sky coordinate system, respectively. These are the coordinates of the transmitter in the Earth's inertial coordinate system. Let x be the coordinates of the receiver in the Earth's inertial coordinate system; T-inl (η,ξ), y T-inl (η,ξ) and z T-inl (η,ξ) are respectively The three-axis coordinates, x R-inl (η,ξ), y R-inl (η,ξ) and z R-inl (η,ξ) are respectively By using the three-axis coordinates, the local incident ray grazing angle θ at the clutter scattering point can be obtained. in,local (η,ξ), local scattered line grazing angle θ sc,local (η,ξ) and local bistatic observation angle γ local (η,ξ) are respectively 6. The method for multi-channel sea clutter modeling of a spaceborne bistatic radar according to claim 1, characterized in that, The multi-channel sea clutter echo signal of the spaceborne bistatic radar is obtained by the following method: Assume that the i-th clutter scattering point in the equidistant ring corresponding to the p-th range ambiguity in the r-th range cell is C. r,p,i The downward viewing angles of this clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively and The azimuth angles are θ az-v-T,r,p,i and θ az-v-R,r,p,i The instantaneous velocity vectors are respectively and The lower viewing angles in the transmit / receive antenna panel coordinate system are respectively and The azimuth angles are θ az-a-T,r,p,i and θ az-a-R,r,p,i Then, in the nth receiving channel and under the kth pulse, the clutter scattering point C r,p,i The corresponding instantaneous two-way slant range for transmission and reception is Among them, R T0,r,p,i and R R0,r,p,i These are clutter scattering points C r,p,i The corresponding initial transmit slant range and initial receive slant range, v s-T and v s-R T represents the speeds of the transmitter and receiver, respectively. PRT d is the pulse repetition time. n Let be the distance between the position of the nth azimuth receiving channel and the origin of the coordinate system of the receiving antenna panel. For the receiving antenna panel coordinate system The axis and the receiving satellite velocity coordinate system The included angle of the axis; After range pulse compression processing, the clutter echo signal received by the nth azimuth receiving channel from the rth range cell is: Where P1 and P2 are the lower and upper bounds of the distance ambiguity number, respectively, and N C Let B be the number of blocks for each clutter equidistant ring, B be the radar bandwidth, c be the speed of light, and A be the number of blocks. r,p,i C is the distance to the clutter scattering point after compression. r,p,i The corresponding signal amplitude is calculated using radar equations, ω r,p,i C is the clutter scattering point. r,p,i The corresponding directional pattern weighting coefficients.

7. A spaceborne bistatic radar multi-channel sea clutter modeling system, characterized in that, Includes the following modules: Module M1: Based on the coordinates of the transmitter and receiver in the Earth inertial coordinate system and the two-way slant range corresponding to the distance cell to be calculated, the star-sea geometric relationship is solved to obtain the coordinates of the clutter scattering point in the Earth inertial coordinate system. Module M2: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the downward angle and azimuth of the clutter scattering point relative to the transmitter and receiver, and obtain the two-way radiation pattern of the spaceborne bistatic radar antenna. Module M3: Based on the coordinates of the clutter scattering points in the Earth's inertial coordinate system obtained in Module M1, establish a time-varying motion model of the sea surface in the local East-North-Sky coordinate system to calculate the motion state of the clutter scattering points; Module M4: Based on the coordinates of the clutter scattering point in the Earth's inertial coordinate system obtained in Module M1, as well as the coordinates of the transmitter and receiver in the Earth's inertial coordinate system, calculate the incident angle, scattering angle, and azimuth bistatic angle corresponding to the clutter scattering point, and calculate the sea clutter bistatic scattering coefficient according to the sea state level and polarization mode. Module M5: Based on the two-way radiation pattern of the spaceborne bistatic radar antenna obtained in Module M2, the motion state of the clutter scattering point obtained in Module M3, and the sea clutter bistatic scattering coefficient obtained in Module M4, calculate the spatial frequency and Doppler frequency corresponding to the clutter scattering point, and obtain the synthesized multi-channel sea clutter echo signal of the spaceborne bistatic radar.

8. A spaceborne bistatic radar multi-channel sea clutter modeling system according to claim 7, characterized in that, The coordinates of the clutter scattering point in the Earth's inertial coordinate system are obtained by the following method: x C-i =Λ1z C-i +Λ2 y C-i =Λ3z C-i +Λ4 Where, x C-i y C-i z C-i Let Λ1, Λ2, Λ3, and Λ4 be the coordinates of the clutter scattering points on the x, y, and z axes in the Earth's inertial coordinate system, respectively. Λ1, Λ2, Λ3, and Λ4 are obtained using the following method: Where, x T-i y T-i z T-i These are the x, y, and z coordinates of the transmitter in the Earth's inertial coordinate system, respectively. R-i y R-i z R-i These represent the receiver's coordinates on the x, y, and z axes in the Earth's inertial coordinate system, respectively. R e R is the Earth's radius. 0,r R represents the two-way slant distance corresponding to the distance cell to be solved. T The slant range of the clutter scattering point relative to the transmitter is obtained through traversal.

9. A spaceborne bistatic radar multi-channel sea clutter modeling system according to claim 7, characterized in that, The two-way radiation pattern of the spaceborne bistatic radar antenna is obtained by the following method: in, and θ az-a-T These represent the downward viewing angle and azimuth angle of the clutter scattering point relative to the transmitter in the coordinate system of the transmitting antenna panel. and θ az-a-R Here, represents the downward viewing angle and azimuth angle of the clutter scattering point relative to the receiver in the coordinate system of the receiving antenna panel, where j is the imaginary unit and N is the horizontal angle. row N represents the number of rows in the antenna array. col d represents the number of antenna array columns. row d is the row spacing of the antenna array. col λ is the antenna array spacing, N is the number of azimuth receiving channels, λ is the radar wavelength, and ω is the azimuth receiving channel. el-T,u and ω az-T,w These are the elevation and azimuth weighting coefficients for the u-th row and w-th column array element in the transmitting antenna, respectively. and θ az-a-T,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the transmit antenna panel coordinate system, ω. el-R,u and ω az-R,w These are the elevation and azimuth weighting coefficients corresponding to the u-th row and w-th column array element in the receiving antenna, respectively. and θ az-a-R,center These represent the downward viewing angle and azimuth angle corresponding to the beam center in the receiving antenna panel coordinate system.

10. A spaceborne bistatic radar multi-channel sea clutter modeling system according to claim 7, characterized in that, The motion state of the sea clutter scattering point is obtained by the following method: The instantaneous velocities of the sea clutter scattering point on the three axes of the local east-north-sky coordinate system are respectively Where t is time, N ω The number of wave frequencies is N. δ Divide the direction of ocean wave motion into numbers, ω i Let k be the frequency of the i-th wave. i Let k be the wave number of the i-th wave. i =ω i 2 / g, A i,j Let i be the wave frequency and j be the wave amplitude corresponding to the j-th wave direction. Φ(ω i ) represents the wave spectrum, D(ω) i ,δ wave,j ) represents the wave direction spectrum, Δω represents the wave frequency division interval, Δδwave represents the wave motion direction division interval, and φ i,j Let θ be the random phase of the wave corresponding to the i-th wave frequency and the j-th wave direction of motion. wind δ is the angle by which the wind direction turns counterclockwise from due east. wave,j Let l be the angle between the j-th wave's direction of motion and the wind direction. j Let be the projection of the distance from the reference point to the clutter scattering point in the j-th wave motion direction; Based on the instantaneous velocity vector of the sea clutter scattering point in the local east-north-sky coordinate system Where T is the matrix transpose, the instantaneous velocity vectors of the sea clutter scattering point in the transmit / receive satellite velocity coordinate system are respectively Among them, M i-o-T and M i-o-R These are the transformation matrices from the Earth inertial coordinate system to the coordinate system of the transmitting / receiving satellite orbital plane, M and M, respectively. o-v-T M is the transformation matrix from the launch satellite orbital plane coordinate system to the launch satellite velocity coordinate system. o-v-R M is the transformation matrix from the receiving satellite orbital plane coordinate system to the receiving satellite velocity coordinate system. l-i This is the transformation matrix from the local East-North-Sky coordinate system to the Earth's inertial coordinate system. This is the linear velocity vector of Earth's rotation. v E Let be the linear velocity of Earth's rotation at the location of this clutter scattering point.

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