CN-122017766-A - Vector double-beam strabismus synthetic aperture radar inversion ocean current antenna pointing correction method

CN122017766ACN 122017766 ACN122017766 ACN 122017766ACN-122017766-A

Abstract

The invention discloses a vector dual-beam squint synthetic aperture radar inversion ocean current antenna pointing correction method, which comprises the steps of matching POS data with SAR echo signals, taking SAR echo signals corresponding to a plurality of continuous pulses as a data block, simultaneously storing the corresponding POS data, screening out data blocks for vector dual-beam squint SAR radar antenna pointing correction, calculating components of total Doppler center frequency of the data blocks for correction in the radial direction of dual beams, calculating components of Doppler center frequency in the radial direction of dual beams caused by carrier platform motion and posture change, calculating components of each data block for correction, which are used for removing the components of the carrier platform motion and the Doppler center frequency in the radial direction of dual beams after the posture change, converting the components into speed, then carrying out vector synthesis, constructing a cost function, and solving the cost function.

Inventors

GU JINGWEI
QIAO SIQI
LIU BAOCHANG
HE YIJUN
LIN WENMING
WANG XUEGANG
ZOU LIN
LI XIUZHONG
CHEN ZIHAO
LAN SHENGHUI

Assignees

南京信息工程大学

Dates

Publication Date: 20260512
Application Date: 20260415

Claims (10)

1. The carrier double-beam strabismus synthetic aperture radar inversion ocean current antenna pointing correction method is characterized by comprising the following steps of: matching the POS data with the SAR echo signals based on time; Based on carrier motion and attitude parameters in POS data, SAR echo signals with stable carrier motion attitude are screened out, SAR echo signals corresponding to a plurality of continuous pulses are used as a data block, and POS data corresponding to the SAR echo signals are stored in the data block; screening out a data block for correcting the pointing direction of the carrier dual-beam squint SAR radar antenna, namely a data block for correcting according to the observation scene, the position and the time; calculating the component of the total Doppler center frequency of the data block for correction in the radial direction of the dual beam And , And Representing the components of the total doppler center frequency of the data block for correction in the forward and backward beam radial directions, respectively; determining squint angle and off-line angle of carrier dual-beam squint SAR radar antenna pointing, and simultaneously calculating component of Doppler center frequency in dual-beam radial direction caused by carrier motion and attitude change based on data block for correction And ; And The components of the Doppler center frequency in the radial direction of the forward and backward beams caused by carrier movement and attitude change are respectively represented; Based on 、、 And Obtaining components of Doppler center frequency in the radial direction of the dual-wave beam after carrier movement and posture change removal of each data block for correction, converting the components into speed, and then carrying out vector synthesis; Constructing a cost function by taking the squint angle and the off-line angle as variable parameters based on the synthesized vector; And solving a cost function to obtain a squint angle and an off-line angle pointed by the final carrier dual-beam squint SAR radar antenna.
2. The method for correcting the directivity of the inverted ocean current antenna of the carrier double-beam squint synthetic aperture radar according to claim 1 is characterized by arranging SAR original echo data according to a real part and an imaginary part to obtain a complex SAR echo signal, extracting time information contained in a frame head part of the SAR echo signal, enabling the time information to be accurate to be in a millisecond, setting a signal of the frame head part to be zero, and then interpolating POS data until the time resolution is consistent with that of the echo signal, so that the POS data is matched with the SAR echo signal based on time.
3. The method for correcting the directivity of the inverted ocean current antenna of the carrier double-beam squint synthetic aperture radar according to claim 1, wherein the following screening conditions are set, and SAR echo signals with stable carrier motion postures are screened out: ; ; ; ; ; Wherein, the Representing the carrier velocity in the POS data, Representing the carrier height in the POS data, Indicating the maximum carrier velocity in the POS data, Representing the maximum carrier height in the POS data, Representing the component of the POS data where the vector of carrier velocity is perpendicular to the ground; Indicating the roll angle in the POS data, Representing pitch angle in POS data; And selecting SAR echo signals corresponding to POS data conforming to the screening conditions according to the set screening conditions.
4. The method for correcting the directivity of the inverted ocean current antenna of the carrier double-beam squint synthetic aperture radar according to claim 1, wherein all data blocks used for correction are formed into a data block set used for correction, the content of echo signals in all the data blocks used for correction in the set is sea surface uniform scenes, the set at least comprises 4 observation directions, scenes corresponding to all the data blocks used for correction are consistent, the difference between positions corresponding to all the data blocks used for correction is smaller than a preset position threshold, and the difference between times corresponding to all the data blocks used for correction is smaller than a preset time threshold.
5. The method for correcting the directivity of the inverted ocean current antenna of the carrier double-beam squint synthetic aperture radar according to claim 1, And The expression of (2) is: ; ; Wherein, the The phase of the complex number is represented, Representing the sampling interval of the SAR echo signal in the azimuth, , Representing the pulse repetition frequency, i representing the ith pulse, And Respectively represent the sampling interval as SAR echo signals of forward and backward beams of (c), Represents the complex conjugate of the two, And Representing the average cross correlation coefficients of the SAR echo signals of the forward and backward beams, respectively.
6. The method for correcting the directivity of the inverted ocean current antenna of the carrier double-beam squint synthetic aperture radar according to claim 1, wherein the calculation of the component of the doppler center frequency in the radial direction of the double-beam caused by the carrier motion and the attitude change is specifically: Taking the direction of the axis of the carrier as the X axis, taking the left direction perpendicular to the axis of the carrier as the Y axis, taking the upward direction perpendicular to the plane of the carrier as the Z axis, constructing a carrier center reference coordinate system, and calculating the direction of the carrier dual-beam squint SAR radar antenna in the carrier center reference coordinate system: ; ; ; Wherein, the As an off-line angle of the line, In order to achieve a squint angle, As an intermediate parameter, a parameter which is a function of the parameter, And Respectively representing the directions of a forward beam antenna and a backward beam antenna of the carrier double-beam squint SAR radar antenna in a carrier center reference system, wherein T represents transposition; Rotating the carrier center reference coordinate system and the direction of the dual-beam squint SAR radar antenna defined in the carrier center reference coordinate system to a carrier track reference coordinate system taking the carrier as an origin, taking the north direction as an X axis and the west direction as a Y axis, and taking the Z axis as a downward direction perpendicular to the ground: ; ; ; ; ; Wherein, the 、 And Each representing a transformation matrix of the corresponding coordinate axis, The roll angle is indicated as the angle of roll, Representing the pitch angle of the light, The yaw angle is indicated as such, And Respectively representing the directions of a forward beam antenna and a backward beam antenna of the carrier double-beam squint SAR radar antenna in a carrier track reference system; calculating the component of Doppler center frequency in the radial direction of the dual-wave beam caused by carrier movement and attitude change: ; ; ; ; Wherein, the Representing the wavelength of the radar, And Representing the radial components of the forward and backward beams of carrier motion and attitude change, respectively; representing the carrier velocity vector.
7. The method for correcting the directivity of the inverted ocean current antenna of the carrier dual-beam squint synthetic aperture radar according to claim 6, wherein the components of the Doppler center frequency in the dual-beam radial direction after removing the carrier motion and the posture change of each data block for correction are obtained are specifically: ; ; Wherein, the And Removing components of Doppler center frequency in the radial directions of forward and backward beams after the motion and posture change of the carrier platform for the data blocks used for correction respectively; The following formula is adopted And Conversion to speed: ; ; Wherein, the Representing the wavelength of the radar, And The components of the ocean current vector after the carrier motion and the posture change are removed in the radial direction of the forward beam and the backward beam respectively; vector synthesis is performed using the following formula: ; ; Wherein, the Representing the ocean current vector after removal of the carrier motion and attitude change, , And Respectively is Components in the Y-axis and Z-axis in the carrier track reference frame, Representation of Is arranged in the first dimension of the (c), Representation of Is arranged in the first dimension of the (c), Representation of In the second dimension of (a), Representation of Is a second dimension of (c).
8. The method for correcting the directivity of the inverted ocean current antenna of the carrier dual-beam squint synthetic aperture radar according to claim 7, wherein the expression of the cost function J is as follows: ; where m represents an mth data block for correction, Indicating the total number of data blocks to be used for correction, Indicating the off-line angle as Oblique viewing angle The j-th block of data for correction removes the vector of sea current after the carrier motion and attitude change.
9. The method for correcting the directivity of the inverted ocean current antenna of the carrier dual-beam squint synthetic aperture radar according to claim 1, wherein the squint angle and the off-line angle of the directivity of the carrier dual-beam squint SAR radar antenna are used as initial conditions, adjustment thresholds of the squint angle and the off-line angle are set, the adjustment thresholds are used as limiting conditions, the minimum value of a cost function is solved, and the squint angle and the off-line angle corresponding to the minimum value of the cost function value are the squint angle and the off-line angle of the final carrier dual-beam squint SAR.
10. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the steps of a carrier dual beam squint synthetic aperture radar inversion ocean current antenna pointing correction method as claimed in any one of claims 1 to 9.

Description

Vector double-beam strabismus synthetic aperture radar inversion ocean current antenna pointing correction method Technical Field The invention belongs to the technical field of ocean remote sensing, and particularly relates to a vector dual-beam strabismus synthetic aperture radar inversion ocean current antenna pointing correction method. Background SAR (SYNTHETIC APERTURE RADAR ) is used as an active microwave remote sensing system, has the unique advantages of all-day and all-weather earth observation, and has great application potential in the field of ocean dynamic environment parameter inversion. For the measurement of the key ocean power element of the sea surface flow field, the traditional single-beam SAR system can only acquire the component of the ocean current vector in the radar sight direction (namely radial direction), and can not directly acquire the complete two-dimensional speed vector information, so that the value of the ocean current vector in ocean scientific research and business application is greatly limited. To solve this problem, dual beam SAR techniques have been developed. According to the technology, two radar beams with different azimuth directions (namely different squint angles) are formed simultaneously, and the same sea surface area is observed successively, so that two independent radial flow velocity components are obtained respectively. By solving the two components simultaneously, the complete two-dimensional vector of the ocean current can be inverted. In the process of inverting the ocean current vector by the radar echo signal, the Doppler center shift-based method becomes a very promising technical path because the radar system on which the method depends is relatively simple and does not need a complex interference baseline. When the Doppler center shift method is used for inverting ocean currents, the Doppler frequency shift caused by the motion and the posture change of the radar platform is required to be calculated and removed by the platform posture correction method, so that the Doppler frequency shift caused by the ocean current motion is separated. If the antenna pointing parameters used in the model are inaccurate, systematic errors can occur in the calculation of the platform motion Doppler, so that the final ocean current inversion result is seriously polluted, and even the final ocean current inversion result is completely disabled. However, in a practical on-board application environment, there are difficulties in obtaining accurate antenna pointing parameters. Before a flight test, although the pointing direction (including the oblique angle and the off-line angle) of the radar antenna can be set manually, in the actual flight process, the actual antenna pointing direction often deviates from a preset ideal value due to the following factors that 1) a platform support deforms, an airborne platform (such as an aircraft) can be affected by air flow disturbance, acceleration change and the like in flight, so that the support connecting the radar, a POS (Position and Orientation System, a positioning and attitude determination system) and a fuselage deforms, and the deformation can be directly transmitted to the antenna to change the spatial pointing direction of the antenna. 2) The installation deviation is that the POS for measuring the motion gesture of the platform and the radar cannot be physically installed at the same point, and a certain lever arm exists between the POS and the radar. The motion pose measured by the POS is its own pose, and its direct use in calculating doppler center offset introduces geometric errors. The actual antenna pointing bias due to these factors, while seemingly small, is not negligible for SAR systems that rely on doppler shift for accurate speed measurement. Therefore, in order to ensure that the on-board dual-beam squint SAR system can invert ocean current vectors with high accuracy, an effective antenna pointing correction method must be developed. Disclosure of Invention The invention aims to solve the problems in the prior art, and provides a vector double-beam squint synthetic aperture radar inversion ocean current antenna pointing correction method. The invention discloses a method for correcting the orientation of an inverted ocean current antenna of a dual-beam strabismus synthetic aperture radar, which comprises the following steps: matching the POS data with the SAR echo signals based on time; Based on carrier motion and attitude parameters in POS data, SAR echo signals with stable carrier motion attitude are screened out, SAR echo signals corresponding to a plurality of continuous pulses are used as a data block, and POS data corresponding to the SAR echo signals are stored in the data block; screening out a data block for correcting the pointing direction of the carrier dual-beam squint SAR radar antenna, namely a data block for correcting according to the observation scene, the position and the time; ca