CN111679258B - Radar echo data processing method, device and equipment - Google Patents

Radar echo data processing method, device and equipment Download PDF

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CN111679258B
CN111679258B CN202010421677.8A CN202010421677A CN111679258B CN 111679258 B CN111679258 B CN 111679258B CN 202010421677 A CN202010421677 A CN 202010421677A CN 111679258 B CN111679258 B CN 111679258B
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data
radar
faraday rotation
echo
matrix
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CN111679258A (en
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刘秀清
邓云凯
禹卫东
王宇
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Aerospace Information Research Institute of CAS
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
    • G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The embodiment of the application discloses a radar data processing method, a device and equipment, wherein the method comprises the steps of acquiring total electron quantity TEC in an ionosphere according to radar original echo data; determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; faraday rotation angle data varies nonlinearly with frequency; determining an influence quantization value of the PD according to Faraday rotation angle data; and if the influence quantization value is greater than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data. According to the radar data processing method, the radar data processing device and the radar data processing equipment provided by the embodiment of the application, PD influence in the original radar echo data can be corrected; the correction effect and the correction accuracy are improved.

Description

Radar echo data processing method, device and equipment
Technical Field
The embodiment of the application relates to the technical field of radar signal processing, in particular to a radar echo data method, a radar echo data device and radar echo data equipment.
Background
The spaceborne P-band synthetic aperture radar (SAR, synthetic Aperture Radar) has unique advantages and huge requirements in military and civil aspects such as hidden target reconnaissance, vegetation resource survey and the like due to the advantages of all-day, all-weather and large-scale mapping of the spaceborne SAR and the characteristic of strong P-band penetrability and sensitivity to forest biomass.
For the satellite-borne SAR, propagation effects such as ionospheric dispersion, scintillation, faraday Rotation (FR), polarization dispersion (PD, polarimetric Dispersion) and the like can introduce errors in the aspects of amplitude, phase, polarization and the like of electromagnetic waves, seriously influence the performance (image resolution, peak sidelobe ratio, integral sidelobe ratio and the like) of the satellite-borne P-band SAR, and restrict the development of a satellite-borne P-band broadband SAR system.
In the traditional technology, the correction of ionosphere Faraday rotation influence in radar echo data is also concentrated on the estimation and correction of FR rotation matrix after SAR imaging, the correction of polarization dispersion influence is not involved, and the polarization dispersion is still a technical bottleneck affecting the image performance of the satellite-borne P-band SAR.
Disclosure of Invention
The embodiment of the invention provides a radar echo data processing method, a radar echo data processing device and radar echo data processing equipment, which can correct polarization dispersion influence in radar echo data.
The technical scheme of the invention is realized as follows:
a radar echo data processing method, comprising: acquiring the total electron quantity TEC in the ionosphere according to the radar original echo data; determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; the Faraday rotation angle data varies nonlinearly with frequency; determining an influence quantization value of PD according to the Faraday rotation angle data; and if the influence quantification value is larger than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data.
A radar echo data processing device, the device comprising: the first acquisition module is used for acquiring the total electron quantity TEC in the ionosphere according to the radar original echo data and determining Faraday rotation angle data corresponding to the radar original echo data according to the total electron quantity; a first determining module for determining an impact quantization value according to the faraday rotation angle data; and the correction module is used for correcting the radar original echo data according to the Faraday rotation angle data if the influence quantization value is larger than or equal to a preset threshold value.
A radar echo data processing device, comprising: a memory for storing executable data instructions; and the processor is used for realizing the radar echo data processing method when executing the executable instructions stored in the memory.
A computer readable storage medium storing executable instructions for causing a processor to perform the radar echo data processing method described above.
In the radar data processing method provided by the embodiment of the application, the total electron quantity TEC in the ionosphere is obtained according to the radar original echo data; determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; faraday rotation angle data varies nonlinearly with frequency; determining an influence quantization value of the PD according to Faraday rotation angle data; and if the influence quantization value is greater than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data. According to the radar data processing method provided by the embodiment of the application, the influence of PD on the radar original echo data is considered when the Faraday rotation angle data is estimated, the Faraday rotation angle data is defined as data which changes along with the nonlinearity of frequency and is not a fixed value, and the PD influence in the radar original echo data can be corrected according to the Faraday rotation angle data when the subsequent correction is carried out; before correcting the radar original echo data, the influence quantized value of the PD is judged according to the preset threshold value, so that the radar original echo data can be corrected only when the PD influence is large, and the problem of reversely correcting the radar original echo data when the PD influence is small is avoided.
Drawings
FIG. 1 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 3 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 6 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 7 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 8 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
fig. 9a to 9k are schematic diagrams of SAR point target images according to the radar echo data processing method provided by the embodiment of the present invention;
FIG. 10 is a schematic flow chart of an alternative method for processing radar echo data according to an embodiment of the present invention;
FIG. 11 is a schematic diagram of a part of a radar echo data processing device according to an embodiment of the present application;
fig. 12 is a schematic diagram of a part of a radar echo data processing device according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application.
FIG. 1 is a schematic flow chart of an alternative method provided by an embodiment of the present application, and will be described with reference to the steps shown in FIG. 1.
In S102, the total amount of electrons TEC in the ionosphere is obtained from the radar raw echo data.
The spaceborne synthetic aperture radar (Synthetic Aperture Radar, SAR) can acquire large-scale and high-resolution images all the time and all the weather, and has important application value in military reconnaissance and economic construction. Ionospheric dispersion, scintillation, and Faraday Rotation (FR) effects introduce errors in electromagnetic wave signal amplitude, phase, polarization, etc., causing degradation in imaging, positioning, polarization measurements, etc. of the spaceborne SAR system. The radar original echo data acquired in the application is unprocessed radar echo data, and is required to be corrected due to the influence of ionospheric dispersion, flicker and FR effect in the transmission process.
The TEC is the total content of the concentration of the ionized layer electrons, also called as the concentration column content, the integral content and the like of the ionized layer, is a very important ionized layer parameter, and has very important significance for theoretical research of ionized layer physics and application research of ionized layer electric wave propagation. In theory, the spatial distribution and time variation of TEC reflect the main characteristics of the ionized layer, so that the distribution and variation characteristics of the ionized layer with different time-space dimensions, such as the ionized layer disturbance, the day-to-day variation of the ionized layer, the annual variation of the ionized layer, the long-term variation of the ionized layer and the like, can be studied by detecting and analyzing the TEC parameters of the ionized layer.
In one embodiment, the total TEC content of electrons in the ionosphere can be directly measured by special instrument equipment during radar imaging, and the method has higher measurement accuracy but poorer timeliness, has measurement delay and can not reflect the influence of the ionosphere on electromagnetic waves at the moment of passing through the ionosphere in real time by using the special instrument equipment.
In another embodiment, TEC can be estimated from radar raw echo data, and in practice, can be estimated by the Bickel and Bates method, freeman method, qi and Jin method, chen and queue method. The method can estimate the average FRA generated by the ionosphere TEC on the electromagnetic waves emitted by the radar from the original echo data of the radar, and then the ionosphere TEC is obtained by back-pushing the FRA value. The method has lower measurement precision than an instrument measurement method, but can reflect the influence of an ionosphere on electromagnetic waves when a radar echo signal passes through the ionosphere in real time.
In another embodiment, the method can improve the TEC estimation precision by dividing the radar original echo data into N sub-band data according to frequency, then using each sub-band data to estimate the sub-band TEC respectively, and using the obtained statistical average value of the N sub-band TECs as the estimation result of the total electron amount TEC in the ionosphere during radar imaging.
In S104, determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; faraday rotation angle data varies nonlinearly with frequency.
In this embodiment, the ionosphere TEC estimated from the radar raw echo data may determine the faraday rotation angle corresponding to the radar raw echo data, and because the influence of PD on the radar raw echo data is considered in the present application, the faraday rotation angle data varies nonlinearly with frequency.
In one embodiment, the magnetic letter clip angle, the lower viewing angle and the magnetic induction intensity of the geomagnetic field during the imaging of the SAR system are required to be obtained, and the Faraday rotation angle data is determined according to the TEC of the radar original echo data, the magnetic letter clip angle, the lower viewing angle and the magnetic induction intensity of the geomagnetic field during the imaging of the SAR system. The magnetic signal included angle is an included angle between the magnetic field and the radar echo signal.
In practice, an expression (1-1) of the faraday rotation angle data can be established, the expression of the faraday rotation angle data being related to TEC, magnetic induction of geomagnetic field, magnetic letter clip angle, lower viewing angle:
wherein Ω (f) is Faraday rotation angle data, f is signal frequency, B 0 The magnetic induction intensity of the geomagnetic field is that alpha is the lower visual angle, and theta is the magnetic information included angle.
In S106, an influence quantization value of PD is determined from faraday rotation angle data.
When the method is implemented, a transmitting signal in an ideal state can be acquired firstly, an echo signal in the ideal state is obtained according to the transmitting signal in the ideal state, a corresponding Faraday rotation angle is added into each frequency point of the echo signal in the ideal state, predicted radar echo data influenced by PD is obtained, and then a corresponding point target image influenced by PD can be obtained; obtaining an ideal point target image according to the echo signals in the ideal state; and comparing the point target image affected by the PD with the ideal point target image to obtain the influence quantized value of the PD.
In S108, if the impact quantization value is greater than or equal to the preset threshold, the radar original echo data is corrected according to the faraday rotation angle data.
The applicant researches find that when certain magnetic letter angles, lower visual angles and different TECs are combined, the PD and the FRA have little influence on radar original echo data, namely, the SAR imaging is little influenced, and the FRA influence does not need to be corrected. According to the design requirement of the SAR system, when the influence quantification value is smaller than the preset threshold value, the influence of PD in the radar original echo data is smaller, and the radar original echo data can not be corrected. And when the influence quantization value is greater than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data.
In the radar data processing method provided by the embodiment of the application, the total electron quantity TEC in the ionosphere is obtained according to the radar original echo data; determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; faraday rotation angle data varies nonlinearly with frequency; determining an influence quantization value of the PD according to Faraday rotation angle data; and if the influence quantization value is greater than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data. According to the radar data processing method provided by the embodiment of the application, the influence of PD on the radar original echo data is considered when the Faraday rotation angle data is estimated, the Faraday rotation angle data is defined as data which changes along with the nonlinearity of frequency and is not a fixed value, and the PD influence in the radar original echo data can be corrected according to the Faraday rotation angle data when the subsequent correction is carried out; before correcting the radar original echo data, the influence quantized value of the PD is judged according to the preset threshold value, so that the radar original echo data can be corrected only when the PD influence is large, and the problem of reversely correcting the radar original echo data when the PD influence is small is avoided.
In some embodiments, referring to fig. 2, fig. 2 is a schematic flow chart of an alternative method provided in the embodiment of the present invention, S102 shown in fig. 1 may be implemented by S1022 to S1028, and the steps will be described in connection with the description.
In S1022, the radar raw echo data is divided into a plurality of sub-band data according to the total bandwidth and the number of sub-bands N of the radar raw echo data.
In this embodiment, the total bandwidth of the radar original echo data is first determined, and the number N of sub-bands to be divided is obtained. The number N of subbands may be preset in the system, or may receive real-time input of an operator through an interaction device. The number of subbands N is generally an integer greater than 1, and as the number of subbands N increases, the subsequent calculation amount increases, but the estimation accuracy of TEC is improved.
In S1024, FRA corresponding to each sub-band data is determined.
In this embodiment, in order to improve the accuracy of TEC estimation, the original radar data is imaged to obtain original image data, and an area in which the targets are uniformly distributed is determined in the original image data, and in the subsequent calculation, only the image data in the area is calculated. The method comprises the steps of acquiring a target uniformly distributed area in original image data through an existing image recognition algorithm, and receiving a frame selection instruction of an operator on the original image data to determine the target uniformly distributed area.
In one embodiment, the FRA corresponding to each sub-band data may be determined by the following equation (1-2):
wherein Ω i FRA, (. Cndot.) for the ith subband data represents conjugate, Z 12 、Z 21 Equation (1-3) can be obtained by:
wherein j isFor the image data in hh polarization mode corresponding to the ith subband data, +.>For the image data in hv polarization mode corresponding to the ith sub-band data, +.>Vh polarization corresponding to ith subband dataImage data in the form->Is the image data in the v polarization mode corresponding to the ith sub-band data.
In S1026, the sub-band TEC corresponding to each sub-band data is obtained by inversion according to the FRA corresponding to each sub-band data.
In this embodiment, the sub-band TEC corresponding to each sub-band data is related to the FRA corresponding to each sub-band data, the center frequency of each sub-band data pair, the lower viewing angle, and the magnetic induction intensity of the geomagnetic field, and in one embodiment, the sub-band TEC corresponding to each sub-band data may be determined by the following formula (1-4):
wherein, TEC i A subband TEC corresponding to the ith subband data, alpha is a lower view angle, B 0 Is the magnetic induction intensity of geomagnetic field, f i And the center frequency corresponding to the ith sub-band data is represented by theta, which is the magnetic information included angle. Wherein B is 0 = (4 e-5) to (5 e-5), units tesla.
In S1028, the average value of the TEC of each subband is used as TEC.
In this embodiment, TEC can be determined by the following formula (1-5):
wherein U is TEC The total quantity of electrons TEC in the ionosphere during radar imaging is calculated, and N is the number of sub-bands.
In the radar data processing method provided by the embodiment of the application, the radar original echo data is divided into a plurality of sub-band data according to the total bandwidth and the number N of sub-bands of the radar original echo data; respectively determining FRA corresponding to each sub-band data; inverting to obtain a subband TEC corresponding to each subband data according to the FRA corresponding to each subband data; the average value of each subband TEC is taken as the total electron quantity TEC in the ionosphere during radar imaging. According to the radar data processing method provided by the embodiment of the application, the radar original echo data is divided into N pieces of sub-band data, and FRA corresponding to each piece of sub-band data is calculated respectively, so that the FRA under each frequency can be accurately subjected to the FRA, and the obtained FRA corresponding to a plurality of pieces of sub-band data can accurately reflect the nonlinear change condition of the FRA under the influence of PD; because TEC corresponding to each sub-band data is calculated, the accuracy of TEC prediction in the radar original echo data is further improved.
In some embodiments, based on fig. 1, the impact quantization value includes a resolution spread ratio corresponding to each of the plurality of polarizations. S108 in fig. 1 is specifically: and if at least one resolution broadening ratio in the resolution broadening ratios corresponding to each polarization mode in the multiple polarization modes is larger than or equal to a preset threshold, correcting the radar original echo data according to Faraday rotation angle data.
In this embodiment, the multiple polarizations may include four polarizations: HH. VV, HV, VH. The electric field vector of the energy pulse emitted by the radar may be polarized in the vertical or horizontal plane. Regardless of the wavelength, the radar signal may transmit a horizontal (H) or vertical (V) electric field vector, receive an echo signal of either horizontal (H) or vertical (V), or both. Wherein HH and VV are co-polarized, and HV and VH are cross-polarized.
Since the radar echo signals corresponding to each polarization mode are affected by the PD differently, there is a difference in resolution spread ratio corresponding to each polarization mode. That is, for the same radar raw echo data, the resolution spread ratios corresponding to the radar echo data under the same polarization may be both greater than the preset threshold, or may be both less than or equal to the preset threshold, or may be greater than the preset threshold, and the resolution spread ratios corresponding to the radar echo data under the same polarization may be less than or equal to the preset threshold, or may be greater than the preset threshold. Therefore, the radar echo data in each polarization mode needs to be calculated separately to obtain the corresponding resolution widening ratio in each polarization mode. In practice, the preset threshold may be set to 1.03.
In the present embodiment, as long as there is a resolution spread ratio in one polarization mode that is greater than or equal to the preset threshold, the radar raw echo data is corrected based on the faraday rotation angle data.
In some embodiments, referring to fig. 3, fig. 3 is a schematic flow chart of an alternative method provided in the embodiment of the present invention, based on fig. 1 and the foregoing embodiments, S106 shown in fig. 1 may be implemented through S1062 to S1068, and the description will be made in connection with each step.
In S1062, a faraday rotation matrix is determined from faraday rotation angle data.
In the present embodiment, faraday rotation angle data has been determined as expression (1-6) relating to TEC, magnetic induction of geomagnetic field, magnetic manifold angle, lower viewing angle, and frequency:
determining the Faraday rotation matrix according to the following formulas (1-7):
wherein F is f Is a faraday rotation matrix.
In S1064, point target image data affected by PD is generated from the specific ideal echo signal and the faraday rotation matrix.
In this embodiment, a preset ideal transmission signal needs to be acquired, and this ideal transmission signal can be determined by the following formula (8):
wherein f 0 For the center frequency, k is the chirp rate, T is the pulse repetition period, rect (&) is a rectangular window function of width and amplitude of 1.
The signal frequency at any time t is determined by the following formulas (1-9):
after the ideal transmitting signal is obtained, the specific ideal echo signal can be obtained according to the specific time delay tau and the specific ideal transmitting signal.
In this embodiment, according to the faraday rotation matrix, a faraday rotation angle of a corresponding frequency point may be added to each frequency point in the ideal echo signal, at this time, the ideal echo signal affected by PD may be estimated, and after imaging processing is performed on the ideal echo signal, point target image data affected by PD may be obtained.
In S1066, ideal point target image data is generated from the ideal echo signal.
In this embodiment, the ideal echo signal is directly subjected to imaging processing, and ideal point target image data is generated as a control image.
In S1068, the point target image data affected by the PD and the target image data of the ideal point are compared to obtain an influence quantized value.
In this embodiment, by comparing the point target image data affected by the PD with the target image data of the ideal point, an influence quantization value of the PD on the point target image data may be obtained, wherein if the influence quantization value is larger, the larger the difference between the point target image data affected by the PD and the target image data of the ideal point is, that is, the higher the influence of the PD on the point target image data is; the smaller the impact quantization value, the smaller the difference between the point target image data affected by the PD and the target image data of the ideal point, that is, the smaller the impact of the PD on the point target image data.
In the radar data processing method provided by the embodiment of the application, a Faraday rotation matrix is determined according to Faraday rotation angle data; generating point target image data affected by the PD according to a specific ideal echo signal and a Faraday rotation matrix; generating ideal point target image data according to the ideal echo signals; and comparing the point target image data affected by the PD with the target image data of the ideal point to obtain an influence quantized value. Because the ideal point target image data generated according to the ideal echo signals is used as a basic judgment image, the difference between the PD-affected point target image data generated according to the specific ideal echo signals and the Faraday rotation matrix and the point target image data is measured to obtain an influence quantization value, the influence of the Faraday rotation matrix on the point target image generation can be accurately reflected, namely the PD influence is judged, judgment basis is provided for the subsequent steps, and the accuracy is indirectly improved.
In some embodiments, referring to fig. 4, fig. 4 is a schematic flow chart of an alternative method provided in the embodiment of the present application, based on fig. 3 and the foregoing embodiments, S1064 shown in fig. 3 may be implemented by S10642 to S10646, and the description will be made in connection with the steps.
In S10642, an ideal echo scattering matrix is established from a specific ideal echo signal; the ideal echo signals include ideal echo signals corresponding to each polarization mode.
In this embodiment, the ideal echo signal includes ideal echo signals corresponding to multiple polarization modes, where the ideal echo signals may include ideal echo signals in four polarization modes HH, VV, HV, VH, and according to the ideal echo signals in each polarization mode, a corresponding ideal echo scattering matrix may be established, as shown in the following formulas (1-10).
Wherein S is s For an ideal echo scattering matrix,ideal echo signal corresponding to HH polarization mode, < >>Ideal echo signal corresponding to HV polarization mode, < ->Ideal echo signal corresponding to VH polarization mode, < ->Is an ideal echo signal corresponding to the VV polarization mode.
In S10644, a scattering matrix affected by PD is determined from the ideal echo scattering matrix and the faraday rotation matrix.
In the present embodiment, since the PD is affected in both the radar transmitting process and the radar receiving process, the influence on the calculation of the faraday rotation matrix twice is required. Thus, the scattering matrix affected by PD can be determined by the following formulas (1-11):
S f ＝F f S s F f (1-11)；
wherein S is f F for a PD-affected scattering matrix f Is Faraday rotation matrix, S s Is an ideal echo scattering matrix.
In S10646, a distance-wise fast fourier transform is performed on the scatter matrix affected by PD, to obtain point target image data affected by PD.
In the radar data processing method provided by the embodiment of the application, an ideal echo scattering matrix is established according to specific ideal echo signals; the ideal echo signals comprise ideal echo signals corresponding to all polarization modes; determining a scattering matrix affected by the PD according to the ideal echo scattering matrix and the Faraday rotation matrix; and performing distance fast Fourier transform on the scattering matrix affected by the PD to obtain point target image data affected by the PD. Because an ideal echo scattering matrix is established according to ideal echo signals corresponding to each polarization mode, and the corresponding scattering matrix influenced by PD can be obtained rapidly according to the Faraday rotation matrix, the point target image data influenced by PD is obtained, and a data basis is provided for comparing the subsequent point target image data with the ideal point target image data.
In some embodiments, referring to fig. 5, fig. 5 is a schematic flow chart of an alternative method provided in the embodiment of the present application, based on fig. 3 and the foregoing embodiments, S1068 shown in fig. 3 may be implemented by S10682 to S10686, and the description will be made in connection with the steps.
In S10682, a first 3dB width corresponding to the PD-affected point target image data is acquired; the first 3dB widths include first 3dB widths corresponding to respective polarizations.
In practice, the comparison may be performed by acquiring the image features in the PD-affected point target image data and the ideal point target image data, in this embodiment by acquiring the 3dB width in the point target image data as the image features.
The obtained point target image data affected by the PD also has a difference in corresponding 3dB widths in different polarization modes, so that it is necessary to obtain the point target image data corresponding to each polarization mode first, and further obtain the first 3dB widths corresponding to each polarization mode.
In S10684, a second 3dB width corresponding to the ideal point target image data is acquired; the second 3dB widths include second 3dB widths corresponding to respective polarizations.
In this embodiment, as described above, the ideal dot target image data also includes dot target image data corresponding to different polarization modes, and the second 3dB widths corresponding to the respective polarization modes are acquired, respectively.
In S10686, the resolution widening ratio corresponding to each polarization is determined according to the first 3dB width and the second 3dB width corresponding to each polarization.
In an embodiment, after obtaining the first 3dB width and the second 3dB width corresponding to each polarization mode, the resolution stretching ratio corresponding to each polarization mode may be determined, where, for each polarization mode, the resolution stretching ratio corresponding to each polarization mode is a ratio of the first 3dB width to the second 3dB width. In implementation, the resolution spread ratio corresponding to each polarization mode is used as the impact quantization value.
In the radar data processing method provided by the embodiment of the application, a first 3dB width corresponding to the point target image data affected by PD is acquired; the first 3dB width comprises a first 3dB width corresponding to each polarization mode; acquiring a second 3dB width corresponding to ideal point target image data; the second 3dB width comprises a second 3dB width corresponding to each polarization mode; and respectively determining the resolution widening ratio corresponding to each polarization mode according to the first 3dB width and the second 3dB width corresponding to each polarization mode. The 3dB width is obtained as the image characteristic of each point target image data, and the ratio between the point target image data affected by PD and the 3dB width in the ideal point target image data is obtained as the influence quantization value, so that the difference between the two point target image data can be accurately quantized, the influence of the Faraday rotation matrix on the point target image generation can be accurately reflected, namely, the PD influence is judged, further, a judgment basis is provided for the subsequent steps, and the correction accuracy is indirectly improved.
In some embodiments, referring to fig. 6, fig. 6 is a schematic flow chart of an alternative method provided in the embodiment of the present invention, based on fig. 1 and the above embodiment, the steps of correcting the radar raw echo data according to the faraday rotation angle data in fig. 1 may be implemented through S1082 to S10810, and will be described with reference to the steps.
In S1082, a transmission distortion matrix and a reception distortion matrix are acquired.
In this embodiment, since there is a certain degree of distortion during the transmission and reception of the SAR system, it is necessary to acquire the transmission distortion matrix R at the time of transmission and the reception distortion matrix T at the time of reception. In practice, the distortion matrix may be obtained by SAR system scaling. Wherein, if R, T is unknown, R, T can be preset as
In S1084, a frequency domain transmit correction matrix is determined from the transmit distortion matrix and the faraday rotation matrix.
In this embodiment, the time-domain transmit correction matrix C may be acquired first R Expression (1-12) of (2).
Wherein F is f The Faraday rotation matrix is adopted, and R is the emission distortion matrix.
Then, the time domain transmission correction matrix C is corrected R Performing time-frequency conversion to obtain a frequency domain emission correction matrix
In S1086, a frequency domain reception correction matrix is determined from the reception distortion matrix and the faraday rotation matrix.
In this embodiment, the time domain receiving correction matrix C may be acquired first T Expression (1-13) of (2).
Wherein F is f Is the faraday rotation matrix, and T is the reception distortion matrix.
Then, the time domain transmission correction matrix C is corrected R Performing time-frequency transformation to obtain a frequency domain receiving correction matrix
In S1088, the radar original echo data in the frequency domain is corrected according to the frequency domain transmission correction matrix and the frequency domain reception correction matrix, so as to obtain distance-to-frequency domain data.
In this embodiment, the radar original echo data is subjected to time-frequency variation, so as to obtain the radar original echo data of the corresponding frequency domain, wherein the radar original echo data is subjected to distance fast fourier transformation, so as to obtain the radar original echo data of the frequency domain.
According to the principle of frequency domain convolution corresponding to time domain multiplication, the radar original echo data of the frequency domain can be corrected to obtain distance-to-frequency domain data, namely, the distance-to-frequency domain data is determined through the following formulas (1-14).
Wherein, the liquid crystal display device comprises a liquid crystal display device,for transmitting correction matrix in frequency domain, M FFT Radar raw echo data for the frequency domain, +.>For the frequency domain reception correction matrix, < > for >Is a convolution.
In S10810, performing a distance inverse fast fourier transform on the distance-to-frequency domain data to obtain a time domain scattering matrix; the time domain scattering matrix comprises corrected echo data corresponding to each polarization mode.
In this embodiment, the distance-to-frequency domain data is already corrected echo data, but it needs to be transformed from frequency domain to time domain, and when implementing, the distance-to-frequency domain data may be transformed by using a distance-to-inverse fast fourier transform to obtain a time domain scattering matrix.
The time domain scattering matrix also includes the correction echo data corresponding to the above-mentioned various polarizations, that is, the time domain scattering matrix includes the correction echo data corresponding to the HH polarization mode, the correction echo data corresponding to the HV polarization mode, the correction echo data corresponding to the VH polarization mode, and the correction echo data corresponding to the VV polarization mode.
In the radar data processing method provided by the embodiment of the application, the transmitting distortion matrix and the receiving distortion matrix are obtained, and the corresponding frequency domain transmitting correction matrix and frequency domain receiving correction matrix are established according to the Faraday rotation matrix, so that the correction process in the embodiment is more accurate due to the consideration of the distortion condition of the SAR system during transmitting and receiving, the obtained time domain scattering matrix is more similar to an ideal echo signal, and the correction effect is improved.
In some embodiments, referring to fig. 7, fig. 7 is a schematic flow chart of an alternative method provided in the embodiment of the present invention, based on fig. 6 and the above embodiment, after step S10810, S10812 to S10816 may also be performed.
In S10812, at least one polarization mode in which the resolution stretching ratio is smaller than the preset threshold is determined as the PD-free polarization mode.
In this embodiment, according to the description in the foregoing embodiment, the magnitude of the influence of PD on the radar echo signal corresponding to each polarization mode is different, so that there is a difference in the resolution stretching ratio corresponding to each polarization mode, and after the correction process is completed to obtain the corrected echo data corresponding to each polarization mode, it is further required to determine whether there is a polarization mode with a resolution stretching ratio smaller than the preset threshold value in each polarization mode, and determine at least one polarization mode with a resolution stretching ratio smaller than the preset threshold value as a PD-free polarization mode. The PD-free polarization mode means that the PD has little influence on radar echo data in the polarization mode, and correction processing is not needed.
In S10814, original echo data corresponding to each PD-free polarization mode is determined from the radar original echo data.
In this embodiment, if at least one PD-free polarization mode exists, the original echo data corresponding to each PD-free polarization mode in the radar original echo data is extracted according to the radar original echo data.
In S10816, the corrected echo data corresponding to each PD-free polarization mode in the time domain scatter matrix is replaced with the original echo data corresponding to each PD-free polarization mode.
In this embodiment, since the influence of PD on radar echo data in the PD-free polarization mode is small, and a phenomenon of inverse correction occurs when the radar echo data is corrected, the corrected echo data corresponding to the PD-free polarization mode may have a large phase difference from ideal echo data, and the corrected echo data corresponding to each PD-free polarization mode in the time domain scattering matrix needs to be replaced with original echo data corresponding to each PD-free polarization mode, so that the obtained time domain scattering matrix is closer to the ideal echo data.
In the radar data processing method provided by the embodiment of the application, the corrected echo data corresponding to each PD-free polarization mode in the time domain scattering matrix is replaced by the original echo data corresponding to each PD-free polarization mode, so that the backward correction of the echo data of the PD-free polarization mode with less influence on PD in each polarization mode can be avoided, and the correction accuracy and correction effect are further improved.
In the following, an exemplary application of the embodiment of the present application in a practical application scenario will be described.
In the embodiment of the invention, the FAR influence correction is performed by using the full-polarization image data acquired by the polarization synthetic aperture radar. Ionosphere TEC content is estimated using polarized SAR data. An ionosphere is evaluated for negligible resolution spread ratio for SAR imaging. When the influence of the FRA and the PD on the SAR imaging quality is not negligible, the correction processing of the FRA influence is performed on the SAR measurement data.
Fig. 8 is a schematic flow chart of an alternative method provided in an embodiment of the present invention, in this embodiment, a method for correcting an effect of faraday rotational polarization dispersion on satellite-borne low-frequency full-polarization SAR imaging is provided, where the method mainly includes:
in S801, TEC content at the time of imaging is calculated from the PolSAR echo data;
in S802, calculating the included angle of magnetic signal and the FRA (the FRA is the FRA affected by PD) under the TEC content and the lower viewing angle;
in S803, the SAR point target image under the FRA and PD is simulated;
in S804, evaluating the influence degree of the FRA and PD on SAR imaging;
in S805, when the influence of FRA and PD on SAR imaging quality is not negligible, correction processing of the FRA influence is performed on the SAR measurement data.
The following steps are described in detail:
for S801 described above: TEC content in imaging is calculated through the PolSAR echo data.
At present, ionosphere TEC measurement methods mainly comprise direct measurement by using special instrument equipment and estimation from SAR echo data. The special instrument and equipment has high measurement precision, but has poor timeliness and measurement delay, and cannot reflect the influence of an ionosphere on electromagnetic waves when a radar signal passes through the ionosphere in real time. The main method for estimating the ionosphere TEC from SAR echo data comprises the following steps: the Bickel and Bates method, the Freeman method, the Qi and Jin method, the Chen and Quegan method. The method can estimate the average FRA generated by the ionosphere TEC on the electromagnetic waves emitted by the radar from the polarized SAR data, and then the ionosphere TEC is obtained by utilizing the FRA value to reversely calculate. The method has lower measurement accuracy than an instrument measurement method, but can reflect the influence of an ionosphere on electromagnetic waves when a radar signal passes through the ionosphere in real time. The method for estimating the ionized layer TEC from SAR echo data can obtain average FAR generated by the ionized layer TEC on radar transmitted electromagnetic waves, and the early research result shows that when the ionized layer TEC is 50TECU, the center frequency of a P wave band is 550MHz, and when the ionized layer TEC is broadband 250MHz, the FRA change range can reach 90 degrees, so that the error of estimating the ionized layer TEC from SAR echo data is large in a conventional way.
Therefore, the method considers that SAR echo data is divided into N sub-bands according to frequency, then each sub-band is utilized to estimate the ionized layer TEC, and the statistical average value of the obtained N ionized layer TEC values is used as the ionized layer TEC estimation result.
In some embodiments, the step S801 may include:
and (11) dividing SAR original echo data into N (N is larger than 1) sub-bands according to frequencies. The frequency bandwidth of each sub-band is the total bandwidth/N. The larger N is, the larger the subsequent calculated amount is, and the higher the TEC content estimation precision is.
Step (1)2) Selecting a uniform scene area of a distribution target in the image, and calculating FRA value omega of corresponding frequency points of each sub-band i 。
Wherein, the step (12) can be calculated by the following formula (2-1):
wherein Z is 12 、Z 21 Calculated from the following formula (2-2).
Here the number of the elements is the number,is image data in HH, HV, VH, VV four polarizations.
After FRA is obtained in step (13), the TEC value for each subband may be inverted by the following equation (2-3).
Where f is the frequency and α is the radar down view angle. B (B) 0 Is the magnetic induction intensity of the geomagnetic field,units tesla.
Step (14) averaging TEC of all frequency points to obtain an estimated value U of TEC content of an imaging area TEC 。
Let TEC value estimated from each sub-band be TEC i U is then TEC The expression (2-4) of (2) is:
in some embodiments, for S802 described above: the included angle of the magnetostriction and the FRA at the lower viewing angle (the FRA is the FRA affected by PD) were calculated for the TEC content. The S802 may include:
and (21) determining a magnetic letter angle theta and a lower visual angle alpha during system imaging.
And (22) calculating FRA under the TEC content, the magnetic information included angle theta and the lower visual angle alpha according to a formula, wherein the FRA is nonlinear change along with the frequency.
Ω (f) is a FRA related to frequency f.
/>
Faraday rotation angle, content of path TEC, signal frequency f and magnetic induction intensity B of geomagnetic field 0 And the magnetic field is related to the radar signal angle theta and the radar lower view angle alpha.
TEC represents the total amount of electrons on the propagation path.
In some embodiments, for S803 above: the SAR point target images under the FRA and PD are simulated. The S803 may include:
step (31) simulates an ideal SAR point target distance chirped echo signal. s (t) is the transmitted chirp signal,
wherein f 0 The signal frequency at any time t is:
and (32) adding FRA of the corresponding frequency point to each frequency point in the SAR echo signal. For a fully polarized SAR system, the echo signal contains echoes of four polarizations as HH, HV, VH, VV in matrix S.
Wherein, the liquid crystal display device comprises a liquid crystal display device,
S f ＝F f S s F f (2-9)；
step (33) performs distance pulse compression (FFT) to obtain point target image data affected by PD.
Referring to fig. 9a to 9k, the schematic diagrams of the SAR point target image under the FRA and PD are shown when the viewing angle is 30 degrees and the magnetic angle is 60 degrees, wherein fig. 9a is the schematic diagram of the SAR point target image under the homopolar, 0TECU, fig. 9b is the schematic diagram of the SAR point target image under the homopolar, 10TECU, fig. 9c is the schematic diagram of the SAR point target image under the homopolar, 20TECU, fig. 9d is the schematic diagram of the SAR point target image under the homopolar, 30TECU, fig. 9e is the schematic diagram of the SAR point target image under the homopolar, 40TECU, fig. 9f is the schematic diagram of the SAR point target image under the homopolar, 50TECU, fig. 9g is the schematic diagram of the SAR point target image under the cross polar, 10TECU, fig. 9h is the schematic diagram of the SAR point target image under the cross polar, 30TECU, fig. 9j is the schematic diagram of the point target image under the cross polar, 40TECU, and fig. 9k is the schematic diagram of the SAR point target image under the cross polar, 50 TECU.
In some embodiments, for S804 above: and evaluating the influence degree of the FRA and the PD on SAR imaging. The S804 may include:
Step (41) calculates the 3dB width of the point target for the four polarizations in S803.
Step (42) simulates an ideal SAR point target distance-wise chirp echo signal, and performs distance-wise pulse compression (FFT) to obtain an ideal point target image.
Step (43) calculates the 3dB width of the ideal point target.
Step (44) calculates a resolution spread ratio of the point target affected by the FRA.
In some embodiments, for S805 described above: when the influence of the FRA and the PD on the SAR imaging quality is not negligible, the correction processing of the FRA influence is performed on the SAR measurement data. The S805 may include:
step (51) studies have found that when certain angles of magnetic signature, radar signal down view, combined with TECU, the effect of FRA on SAR imaging is small, and no correction for FRA effect is needed. In general, the effect of FRA may not be corrected when the resolution spread ratio is better than a certain value (empirically, the present invention is designed to be 1.03) depending on SAR system design requirements.
Table 1 shows that the magnetic signal included angles corresponding to different TECUs and resolution broadening ratios are better than 1.03 at a center frequency of 550MHz and a system signal bandwidth of 300M and an incident angle of 30 degrees. That is, when the incident angle is 30 °, the influence of FRA is not corrected when the TEC content and the magnetic signal clamping angle are in the ranges in the table.
TABLE 1 Linear polarization mode, resolution spread ratio better than the corresponding magnetic letter clamping angle of 1.03
And (52) correcting the influence of FRA on SAR measurement data when the resolution broadening ratio of the point target image is larger than 1.03.
The backscattering matrix of the target when the full polarization SAR system is present at transmit and receive distortions is as follows:
wherein R, T are the transmit and receive distortion matrices, respectively, that can be derived from off-system scaling. When R, T is unknown, it can be assumed that
The transmit and receive correction matrices are set respectively as follows:
fourier Transform (FFT) processing is performed on the transmit and receive correction matrices, transforming to the frequency domain.
And obtaining a distance-to-frequency domain scattering matrix after FRA influence correction according to the principle of frequency domain convolution corresponding to time domain multiplication.
And performing distance IFFT on the corrected distance-to-frequency domain data to obtain a time domain scattering matrix after FRA influence correction.
S＝IFFT(S FFT ) (2-17)；
Equation (2-17) is the time domain back scattering echo data of the full polarization four channels (HH, HV, VH, VV) after FRA influence correction.
Fig. 10 is a schematic flow chart of an alternative method provided in an embodiment of the present invention, where the flow of the effect of the available correction FRA on SAR imaging includes:
in S1001, FRA values corresponding to all the frequency bins are calculated from the TEC values obtained by the above equation (2-5).
In S1002, FR matrices corresponding to all the frequency points are calculated by the above formulas (2-10).
In S1003, the transmission correction matrix and the reception correction matrix are obtained from the above formulas (2-12) and (2-13). Since the faraday rotation angle by the TEC is different for each frequency point, the FRA needs to be compensated for each frequency point in the frequency domain.
In S1004, the transmission correction matrix and the reception correction matrix are transformed to the frequency domain as in the above formulas (2-14) and (2-15).
In S1005, the SAR original echo data is subjected to distance FFT, and the data is transformed into a distance frequency domain.
In S1006, the transmit correction matrix, the FR matrix, and the receive correction matrix are convolved according to equation (2-16) to obtain a range-to-frequency domain scattering matrix after FRA effect correction.
In S1007, the corrected distance-to-frequency domain data is subjected to distance-to-IFFT to obtain a time domain scatter matrix after FRA effect correction, that is, the above expression (2-17).
The embodiment of the invention also provides a radar echo data processing device which is used for implementing the radar echo data processing method. Fig. 11 is a schematic diagram of a part of a radar echo data processing device according to an embodiment of the present invention. As shown in fig. 11, the radar echo data processing device includes: a first acquisition module 11, a first determination module 12, a second determination module 13, and a correction module 14; wherein:
The first acquisition module 11 is used for acquiring the total electron quantity TEC in the ionosphere according to the radar original echo data; the first determining module 12 is configured to determine faraday rotation angle data corresponding to the radar original echo data according to the TEC; the Faraday rotation angle data varies nonlinearly with frequency; a second determining module 13 for determining an influence quantization value of PD according to the faraday rotation angle data; and the correction module 14 is configured to correct the radar original echo data according to the faraday rotation angle data if the impact quantization value is greater than or equal to a preset threshold.
In some embodiments, the first obtaining module 11 is further configured to divide the radar raw echo data into a plurality of sub-band data according to a total bandwidth and a sub-band number N of the radar raw echo data; respectively determining FRA corresponding to each sub-band data; inverting to obtain a subband TEC corresponding to each subband data according to the FRA corresponding to each subband data; the average value of TEC of each subband is used as TEC.
In some embodiments, the first determining module 12 is further configured to obtain a magnetic letter clip angle, a lower viewing angle, and a geomagnetic induction intensity; and determining Faraday rotation angle data according to the TEC, the magnetic signal included angle, the lower visual angle and the geomagnetic induction intensity.
In some embodiments, the influencing quantization value includes a resolution stretching ratio corresponding to each of the multiple polarizations, and the correction module 14 is further configured to correct the radar raw echo data according to the faraday rotation angle data if at least one resolution stretching ratio in the resolution stretching ratios corresponding to each of the multiple polarizations is greater than or equal to a preset threshold.
In some embodiments, the second determining module 13 is further configured to determine a faraday rotation matrix according to faraday rotation angle data; generating point target image data affected by the PD according to a specific ideal echo signal and a Faraday rotation matrix; generating ideal point target image data according to the ideal echo signals; and comparing the point target image data affected by the PD with the target image data of the ideal point to obtain an influence quantized value.
In some embodiments, the second determining module 13 is further configured to establish an ideal echo scattering matrix according to a specific ideal echo signal; the ideal echo signals comprise ideal echo signals corresponding to all polarization modes; determining a scattering matrix affected by the PD according to the ideal echo scattering matrix and the Faraday rotation matrix; and performing distance fast Fourier transform on the scattering matrix affected by the PD to obtain point target image data affected by the PD.
In some embodiments, the second determining module 13 is further configured to obtain a first 3dB width corresponding to the point target image data affected by PD; the first 3dB width comprises a first 3dB width corresponding to each polarization mode; acquiring a second 3dB width corresponding to ideal point target image data; the second 3dB width comprises a second 3dB width corresponding to each polarization mode; and respectively determining the resolution widening ratio corresponding to each polarization mode according to the first 3dB width and the second 3dB width corresponding to each polarization mode.
In some embodiments, the correction module 14 is further configured to obtain a transmit distortion matrix and a receive distortion matrix; determining a frequency domain emission correction matrix according to the emission distortion matrix and the Faraday rotation matrix; determining a frequency domain receiving correction matrix according to the receiving distortion matrix and the Faraday rotation matrix; correcting the radar original echo data of the frequency domain according to the frequency domain transmitting correction matrix and the frequency domain receiving correction matrix to obtain distance-direction frequency domain data; performing distance inverse fast Fourier transform on the distance frequency domain data to obtain a time domain scattering matrix; the time domain scattering matrix comprises corrected echo data corresponding to each polarization mode.
In some embodiments, the correction module 14 is further configured to determine at least one polarization mode with a resolution stretching ratio smaller than a preset threshold as a PD-free polarization mode; according to the radar original echo data, determining original echo data corresponding to each PD-free polarization mode; and replacing the corrected echo data corresponding to each PD-free polarization mode in the time domain scattering matrix with the original echo data corresponding to each PD-free polarization mode.
The description of the apparatus embodiments above is similar to that of the method embodiments above, with similar advantageous effects as the method embodiments. For technical details not disclosed in the embodiments of the apparatus of the present application, please refer to the description of the embodiments of the method of the present application.
It should be noted that, in the embodiment of the present application, if the above-mentioned radar echo data processing method is implemented in the form of a software functional module, and sold or used as a separate product, the radar echo data processing method may also be stored in a computer readable storage medium. Based on such understanding, the technical solution of the embodiments of the present application may be embodied essentially or in a part contributing to the related art in the form of a software product stored in a storage medium, including several instructions for causing a radar echo data processing device (for example, a computer device or the like) to execute all or part of the methods according to the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read Only Memory (ROM), a magnetic disk, an optical disk, or other various media capable of storing program codes. Thus, embodiments of the application are not limited to any specific combination of hardware and software.
Fig. 12 is a schematic diagram of a part of a radar echo data processing device according to an embodiment of the present invention. As shown in fig. 12, the radar echo data processing device 2 includes: a memory 21 and a processor 22, the memory 21 and the processor 22 being connected by a bus 23; a memory 21 for storing executable data instructions; the processor 22 is configured to implement the radar echo data processing method when executing the executable instructions stored in the memory.
The embodiment of the invention also provides a computer readable storage medium which stores executable instructions for causing a processor to execute the method for processing radar echo data in the embodiment of the method.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, magnetic disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention.

Claims (9)

1. A radar echo data processing method, comprising:
acquiring the total electron quantity TEC in the ionosphere according to the radar original echo data;
determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; the Faraday rotation angle data varies nonlinearly with frequency;
determining a Faraday rotation matrix according to the Faraday rotation angle data;
an ideal echo scattering matrix is established according to specific ideal echo signals; the ideal echo signals comprise ideal echo signals corresponding to all polarization modes;
determining a scattering matrix affected by PD according to the ideal echo scattering matrix and the Faraday rotation matrix;
Performing distance fast Fourier transform on the scattering matrix affected by the PD to obtain point target image data affected by the PD;
generating ideal point target image data according to the ideal echo signals; comparing the point target image data affected by the PD with the target image data of the ideal point to obtain an influence quantized value;
and if the influence quantification value is larger than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data.
2. The method of claim 1, wherein the acquiring the total amount of electrons TEC in the ionosphere from the radar raw echo data comprises:
dividing the radar original echo data into a plurality of sub-band data according to the total bandwidth and the sub-band number N of the radar original echo data;
respectively determining Faraday rotation angles FRA corresponding to the sub-band data;
inverting to obtain a subband TEC corresponding to each subband data according to the FRA corresponding to each subband data;
and taking the average value of each subband TEC as the TEC.
3. The method of claim 1, wherein the determining faraday rotation angle data corresponding to the radar raw echo data from the TEC comprises:
Acquiring a magnetic letter clip angle, a lower visual angle and geomagnetic induction intensity;
and determining the Faraday rotation angle data according to the TEC, the magnetic signal included angle, the lower visual angle and the geomagnetic induction intensity.
4. The method of claim 1, wherein the influencing quantization value comprises a resolution spread ratio corresponding to each of a plurality of polarizations;
and if the influence quantization value is greater than or equal to a preset threshold value, correcting the radar original echo data according to the Faraday rotation angle data, including:
and if at least one resolution broadening ratio in the resolution broadening ratios corresponding to each polarization mode in the multiple polarization modes is larger than or equal to the preset threshold, correcting the radar original echo data according to the Faraday rotation angle data.
5. The method of claim 1, wherein comparing the PD-affected point target image data with the ideal point target image data to obtain target image data affecting quantized value ideal points, comprises:
acquiring a first 3dB width corresponding to the PD-affected point target image data; the first 3dB width comprises a first 3dB width corresponding to each polarization mode;
Acquiring a second 3dB width corresponding to the ideal point target image data; the second 3dB width comprises a second 3dB width corresponding to each polarization mode;
and respectively determining the resolution widening ratio corresponding to each polarization mode according to the first 3dB width and the second 3dB width corresponding to each polarization mode.
6. The method of claim 1, wherein said correcting said radar raw echo data based on said faraday rotation angle data comprises:
acquiring a transmitting distortion matrix and a receiving distortion matrix;
determining a frequency domain emission correction matrix according to the emission distortion matrix and the Faraday rotation matrix;
determining a frequency domain receiving correction matrix according to the receiving distortion matrix and the Faraday rotation matrix;
correcting the radar original echo data of the frequency domain according to the frequency domain transmitting correction matrix and the frequency domain receiving correction matrix to obtain distance-to-frequency domain data;
performing distance inverse fast Fourier transform on the distance frequency domain data to obtain a time domain scattering matrix; the time domain scattering matrix comprises corrected echo data corresponding to each polarization mode.
7. The method of claim 6, wherein the method further comprises:
Determining at least one polarization mode with the resolution broadening ratio smaller than the preset threshold value as a PD-free polarization mode;
according to the radar original echo data, determining original echo data corresponding to each PD-free polarization mode;
and replacing the corrected echo data corresponding to each PD-free polarization mode in the time domain scattering matrix with the original echo data corresponding to each PD-free polarization mode.
8. A radar echo data processing device, the device comprising:
the first acquisition module is used for acquiring the total electron quantity TEC in the ionosphere according to the radar original echo data;
the first determining module is used for determining Faraday rotation angle data corresponding to the radar original echo data according to the TEC; the Faraday rotation angle data varies nonlinearly with frequency;
the second determining module is used for determining a Faraday rotation matrix according to the Faraday rotation angle data;
an ideal echo scattering matrix is established according to specific ideal echo signals; the ideal echo signals comprise ideal echo signals corresponding to all polarization modes;
determining a scattering matrix affected by PD according to the ideal echo scattering matrix and the Faraday rotation matrix;
Performing distance fast Fourier transform on the scattering matrix affected by the PD to obtain point target image data affected by the PD;
generating ideal point target image data according to the ideal echo signals;
comparing the point target image data affected by the PD with the target image data of the ideal point to obtain an influence quantized value;
and the correction module is used for correcting the radar original echo data according to the Faraday rotation angle data if the influence quantification value is larger than or equal to a preset threshold value.
9. A radar echo data processing device, comprising:
a memory for storing executable data instructions;
a processor for implementing the radar echo data processing method of any one of claims 1 to 7 when executing executable instructions stored in the memory.
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Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5313210A (en) * 1993-02-23 1994-05-17 Ball Corporation Polarimetric radar signal mapping process
US6163295A (en) * 1999-04-09 2000-12-19 Vsis, Inc. Ionospheric correction for single frequency GPS receivers using two satellites
US6914553B1 (en) * 2004-11-09 2005-07-05 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the Faraday rotation, and associated methods
US6919839B1 (en) * 2004-11-09 2005-07-19 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the group delay, and associated methods
CN101551450A (en) * 2009-05-06 2009-10-07 北京航空航天大学 A building approach for space-borne polarization SAR Faraday rotation effect correction platform
CN103792521A (en) * 2014-01-17 2014-05-14 西安空间无线电技术研究所 Radar target back scattering simulation method influenced by Faraday rotation changes
CA2957541A1 (en) * 2014-08-08 2016-02-11 Urthecast Corp. Apparatus and methods for quad-polarized synthetic aperture radar
CN106154268A (en) * 2016-09-06 2016-11-23 合肥工业大学 A kind of low band ISAR ionosphere corrections method based on subband segmentation
CN107526079A (en) * 2016-06-22 2017-12-29 中国解放军空军工程大学 A kind of spatial spin target wideband radar three-D imaging method based on L-type triantennary interference treatment
CN107544068A (en) * 2017-07-14 2018-01-05 电子科技大学 A kind of image area synthetic wideband method based on frequency domain BP

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5313210A (en) * 1993-02-23 1994-05-17 Ball Corporation Polarimetric radar signal mapping process
US6163295A (en) * 1999-04-09 2000-12-19 Vsis, Inc. Ionospheric correction for single frequency GPS receivers using two satellites
US6914553B1 (en) * 2004-11-09 2005-07-05 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the Faraday rotation, and associated methods
US6919839B1 (en) * 2004-11-09 2005-07-19 Harris Corporation Synthetic aperture radar (SAR) compensating for ionospheric distortion based upon measurement of the group delay, and associated methods
CN101551450A (en) * 2009-05-06 2009-10-07 北京航空航天大学 A building approach for space-borne polarization SAR Faraday rotation effect correction platform
CN103792521A (en) * 2014-01-17 2014-05-14 西安空间无线电技术研究所 Radar target back scattering simulation method influenced by Faraday rotation changes
CA2957541A1 (en) * 2014-08-08 2016-02-11 Urthecast Corp. Apparatus and methods for quad-polarized synthetic aperture radar
CN107526079A (en) * 2016-06-22 2017-12-29 中国解放军空军工程大学 A kind of spatial spin target wideband radar three-D imaging method based on L-type triantennary interference treatment
CN106154268A (en) * 2016-09-06 2016-11-23 合肥工业大学 A kind of low band ISAR ionosphere corrections method based on subband segmentation
CN107544068A (en) * 2017-07-14 2018-01-05 电子科技大学 A kind of image area synthetic wideband method based on frequency domain BP

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