CN113030965A - Bistatic ISAR image skew correction method - Google Patents

Bistatic ISAR image skew correction method Download PDF

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CN113030965A
CN113030965A CN202110154591.8A CN202110154591A CN113030965A CN 113030965 A CN113030965 A CN 113030965A CN 202110154591 A CN202110154591 A CN 202110154591A CN 113030965 A CN113030965 A CN 113030965A
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bistatic
isar image
radar
time
representing
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史林
郭宝锋
刘利民
马俊涛
董健
薛东方
韩壮志
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Army Engineering University of PLA
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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
    • 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
    • G01S13/904—SAR modes
    • G01S13/9064—Inverse SAR [ISAR]
    • 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
    • G01S7/40—Means for monitoring or calibrating

Abstract

The invention is suitable for the technical field of radar signal processing, and provides a bistatic ISAR image skew correction method, which comprises the following steps: performing pulse compression and pretreatment on a received target echo signal of the bistatic radar to obtain corrected one-dimensional range profile echo data; calculating a bistatic earth angle during imaging of the bistatic ISAR image, and calculating a bistatic time-varying coefficient according to the bistatic earth angle; correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time-varying coefficient, and determining the skew phase of the bistatic ISAR image; and constructing a phase change compensation item, and compensating the skew phase of the bistatic ISAR image according to the phase change compensation item to obtain the bistatic ISAR image after skew correction, so that the image skew phenomenon caused by bistatic angular time variation can be effectively and robustly corrected, the imaging quality is improved, and the subsequent target identification is facilitated.

Description

Bistatic ISAR image skew correction method
Technical Field
The invention belongs to the technical field of radar signal processing, and particularly relates to a bistatic ISAR image skew correction method.
Background
The bistatic Inverse Synthetic Aperture Radar (ISAR) system is based on a bistatic Radar platform, has outstanding advantages in the aspects of anti-radiation missile, active interference, passive interference and the like of a common bistatic Radar, and can utilize received target non-backscatter echoes to perform imaging, so that target information richer than that of a monostatic Radar is obtained. Range-Doppler (RD) imaging is typically used in bistatic ISAR imaging systems. However, the remote configuration of the transmitting and receiving radar station introduces a double-base angle, the double-base angle is an included angle formed by the radar sight line direction of the transmitting station and the radar sight line direction of the receiving station during imaging, and in the actual RD imaging process, the double-base angle changes along with time, so that by adopting RD imaging, a two-dimensional image of a target obtained by the double-base ISAR can be skewed, and subsequent target identification is influenced.
In the prior art, a bistatic ISAR imaging plane is researched by respectively adopting a bistatic ISAR imaging plane analysis-based method and a rotation vector analysis-based method, so that the conclusion that the bistatic ISAR imaging distance axis and the azimuth axis are not orthogonal and the image is skewed is obtained, the analysis process is complicated, the engineering implementation is inconvenient, and the correction of the skewed image is not involved.
Disclosure of Invention
In view of this, an embodiment of the present invention provides a bistatic ISAR image skew correction method to solve the problem in the prior art that the process of analyzing image skew of bistatic ISAR imaging is complex and image skew is not corrected.
The first aspect of the embodiment of the invention provides a bistatic ISAR image skew correction method, which comprises the following steps:
performing pulse compression on a received target echo signal of the bistatic radar to obtain a one-dimensional range profile sequence;
preprocessing each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data;
according to the radar station position information of the bistatic radar and the track information of a target, calculating a bistatic angle during imaging of a bistatic ISAR image, and according to the bistatic angle, calculating a bistatic time-varying coefficient;
correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time-varying coefficient, and determining the skew phase of the bistatic ISAR image;
and constructing a phase change compensation item, and compensating the skew phase of the bistatic ISAR image according to the phase change compensation item to obtain the bistatic ISAR image after skew correction.
Optionally, the one-dimensional range profile in the one-dimensional range profile sequence is
Figure BDA0002934119890000021
Wherein the content of the first and second substances,
Figure BDA0002934119890000022
is shown at tmMoment scattering point PmOne-dimensional range profile of (a)PIs shown at t0The scattering coefficient of the scattering point P at the moment, mu, represents the frequency modulation rate of the bistatic radar, TpWhich represents the pulse width of the bistatic radar,
Figure BDA0002934119890000023
denotes fast time, RPmRepresents the scattering point PmThe sum of the distances to the transmitting station and the receiving station of the bistatic radar, c represents the propagation speed of the electromagnetic wave in free space, j represents an imaginary number, fcRepresenting the carrier frequency of the pulses transmitted by the bistatic radar.
Optionally, the preprocessing each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data includes:
is obtained at t0Position data of the centroid O of the object at time tmMoment scattering point PmThe location data of (a);
from the position data of the object centroid O and the scattering point PmCalculating said scattering point PmThe difference between the sum of the distances to the transmitting station and the receiving station of the bistatic radar and the sum of the distances to the transmitting station and the receiving station of the target centroid O bistatic radar;
and according to the difference, carrying out envelope alignment, phase self-focusing and over-range unit migration correction on each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data.
Optionally, calculating a bistatic angle during bistatic ISAR image imaging according to the radar station position information of the bistatic radar and the orbit information of the target, including:
according to
Figure BDA0002934119890000031
Calculating bistatic angles during bistatic ISAR image imaging; wherein, β (t)0) Is shown at t0Imaging the corresponding biprimary angle, beta (t), at a timem) Is shown at tmImaging the corresponding biprimary angle, R, at a timeTORepresenting the distance of the centroid O of the target from the transmitting station of the bistatic radar, RRORepresenting the distance of the target centroid O to the receiving station of the bistatic radar, L representing the length of the bistatic radar system baseline, RTOmRepresenting the center of mass O of the objectmDistance to transmitting station of bistatic radar, RROmRepresenting the center of mass O of the objectmDistance to the receiving station of the bistatic radar.
Optionally, calculating a bistatic time-varying coefficient according to the bistatic angle includes:
according to the bistatic angle and the first definition during the imaging of the bistatic ISAR image, calculating by using the minimum mean square error to obtain a bistatic time-varying coefficient; the first definition is beta (t)m)≈β0+ΔβtmWherein, β0Representing the beginning of imagingThe double-base angle at the initial moment, and delta beta represents the first derivative of the double-base angle imaging at the initial moment;
and determining the value of the bistatic time-varying coefficient according to the bistatic time-varying coefficient.
Optionally, the determining the value of the bistatic time-varying coefficient according to the bistatic time-varying coefficient includes:
according to
Figure BDA0002934119890000032
Determining a value of the bistatic time-varying coefficient;
wherein, K0、K1Respectively, representing the values of the bistatic time-varying coefficients.
Optionally, the correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time varying coefficient, and determining a phase of the bistatic ISAR image skew includes:
according to the target equivalent accumulated rotation angle and the bistatic time-varying coefficient pair Delta RPmSimplified treatment is carried out to obtain treated delta RPm'；
According to the treated delta RPm' and correcting the linear distance walking term by the corrected one-dimensional range profile echo data, and determining a corresponding phase polynomial signal of the nth range unit;
and determining the skew phase of the bistatic ISAR image according to the corresponding phase polynomial signal of the nth distance unit.
Optionally, Δ R after said treatmentPm' is
Figure BDA0002934119890000041
Wherein, ω is0Representing target equivalent rotational speed, xpRepresenting the abscissa value of the scattering point P in an xOy coordinate system, wherein the xOy coordinate system is a right-hand rectangular coordinate system established by taking the target centroid O as the origin and taking the bipartite ground angle bisector as the y axis, and ypRepresenting the ordinate value of the scattering point P in the xOy coordinate system;
the corresponding phase polynomial signal of the nth distance unit is
Figure BDA0002934119890000042
Wherein s isn(tm) Representing the corresponding phase polynomial signal of the nth range cell, AiIndicating the amplitude of the echo at the ith scattering point, i-1, 2 … Ln，LnDenotes the total number of scattering points, ynRepresenting a longitudinal distance coordinate value, xiAnd represents the lateral distance coordinate value of the ith scattering point.
Optionally, the phase change compensation term is
Figure BDA0002934119890000043
Wherein the content of the first and second substances,
Figure BDA0002934119890000044
representing a phase change compensation term.
Optionally, the skew-corrected bistatic ISAR image has an exponential term of
Figure BDA0002934119890000045
Where ψ' denotes an exponential term of the skew-corrected bistatic ISAR image.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: the method comprises the steps of starting from a bistatic ISAR image skew mechanism, estimating a bistatic earth angle time-varying coefficient, determining a bistatic ISAR image skew phase, constructing a phase change compensation item, performing phase compensation on the bistatic ISAR image skew phase to correct image skew, and performing azimuth compression to obtain a skew-corrected two-dimensional image, so that the image skew phenomenon caused by bistatic earth angle time-varying can be effectively and robustly corrected, the imaging quality is improved, and subsequent target identification is facilitated.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic flow chart illustrating an implementation of a bistatic ISAR image skew correction method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a bistatic radar system provided by an embodiment of the present invention;
FIG. 3(a) is a schematic view of a scattering point model of an image skew schematic view provided by an embodiment of the present invention;
FIG. 3(b) is an imaging schematic diagram of a bistatic ISAR image with an image skew schematic diagram provided by an embodiment of the invention;
fig. 4 is an exemplary diagram of the number of tracks TLE information of the international space station provided in the embodiment of the present invention;
FIG. 5 is a schematic diagram of a simulation scenario provided by an embodiment of the invention;
FIG. 6 is an exemplary diagram of simulated imaging parameter settings provided by embodiments of the present invention;
FIG. 7 is a schematic diagram of a projection of a scattering point model on an imaging plane along a line of sight direction of an equivalent monostatic radar according to an embodiment of the invention;
FIG. 8 is a schematic diagram of the variation of bistatic angles with the number of accumulated pulses provided by an embodiment of the present invention;
fig. 9(a) is a schematic diagram of a two-dimensional ISAR image obtained based on an RD algorithm according to an embodiment of the present invention;
fig. 9(b) is a schematic diagram of a two-dimensional ISAR image using a bistatic ISAR image skew correction method according to an embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
Fig. 1 is a schematic flow chart of an implementation of a bistatic ISAR image skew correction method according to an embodiment of the present invention, which is described in detail below.
Step 101, performing pulse compression on a received target echo signal of the bistatic radar to obtain a one-dimensional range profile sequence.
Optionally, as shown in fig. 2, the schematic diagram of the bistatic radar system is shown, where T is a transmitting station of the bistatic radar system, R is a receiving station of the bistatic radar system, L is a length of a baseline of the bistatic radar system, and point E is an equivalent monostatic radar position of the bistatic radar system. The target moves stably in the space, and the moving speed is V. Initial imaging time t0With the target centroid at O and the ground angle at t0Establishing a right-hand rectangular coordinate system xOy by taking the target centroid O as an origin and the biprimary ground angle bisector as a y axis, wherein the coordinate of the scattering point p in the coordinate system is (x)P,yP) OP length d and angle alpha with x-axis0. At tmAt that moment, the target centroid O shifts to OmPoint, coordinate system x' Omy' is translated from the coordinate system xOy by OmAs an origin, a right-hand rectangular coordinate system uO is established by taking the bipartite ground angular bisector as a v-axismv. scattering point p in the coordinate system uOmv is marked as Pm(xPm,yPm)，OmPmAt an angle alpha to the u axismThe angle of view of the equivalent monostatic radar is changed to thetam。PmThe distances to the transmitting station and the receiving station are RTPm、RRPm，OmThe distances to the transmitting station and the receiving station are RTOm、RROm。
Suppose a transmitting-receiving double station mineIdeal synchronization is achieved, the radar of the transmitting station repeats the period T in pulsesPRTTransmitting a chirp signal, which may be
Figure BDA0002934119890000071
Wherein the content of the first and second substances,
Figure BDA0002934119890000072
which is representative of a chirp signal that is,
Figure BDA0002934119890000073
indicating fast time, TpRepresenting the pulse width of the bistatic radar, j representing an imaginary number, fcThe carrier frequency of the pulse transmitted by the bistatic radar is indicated, and μ represents the tuning frequency of the bistatic radar. In addition, rect (u) is a rectangular window function, and when | u ≦ 0.5, rect (u) 1, when | u ≦ intangible>At 0.5, rect (u) is 0; t is tm＝mTPRT(m ═ 0,1, 2..) which is bistatic radar signal transmission time, called slow time, t is full time, and the relationship between the three is:
Figure BDA0002934119890000074
according to equation (1), the fundamental frequency signal of the chirp signal can be determined as
Figure BDA0002934119890000075
Assuming that the scattering coefficient of the scattering point P may be σPAt tmMoment scattering point PmThe sum of the distances to the transmitting and receiving stations of the bistatic radar is RPmI.e. RPm＝RTPm+RRPmThen the receiving station of the bistatic radar receives the echo signal as
Figure BDA0002934119890000076
Down-converting to zero intermediate frequency by coherent local oscillator, and performing pulse compression on target echo signal by using matched filter to obtain scattering point PmIs a one-dimensional range image of
Figure BDA0002934119890000077
Wherein the content of the first and second substances,
Figure BDA0002934119890000078
is shown at tmMoment scattering point PmOne-dimensional range profile of (a)PDenotes the scattering coefficient of the scattering point P at time T, mu denotes the frequency modulation of the bistatic radar, TpWhich represents the pulse width of the bistatic radar,
Figure BDA0002934119890000079
denotes fast time, RPmRepresents the scattering point PmThe sum of the distances to the transmitting station and the receiving station of the bistatic radar, c represents the propagation speed of the electromagnetic wave in free space, j represents an imaginary number, fcRepresenting the carrier frequency of the pulses transmitted by the bistatic radar.
And 102, preprocessing each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data.
Optionally, in this step, when preprocessing each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data, the method may include:
obtaining position data of a centroid O of an object at time t and at tmMoment scattering point PmThe location data of (a);
from the position data of the object centroid O and the scattering point PmCalculating said scattering point PmThe difference between the sum of the distances to the transmitting station and the receiving station of the bistatic radar and the sum of the distances to the transmitting station and the receiving station of the target centroid O bistatic radar;
and according to the difference, carrying out envelope alignment, phase self-focusing and over-range unit migration correction on each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data. The method comprises the steps of performing envelope alignment by adopting an accumulative cross-correlation method, completing phase self-focusing by utilizing a weighted least square self-focusing algorithm, and completing migration correction of the over-distance unit by utilizing keystone transformation.
Optionally, the above is based on the target centroid OmAnd the scattering point PmCalculating said scattering point PmDistance to transmitting and receiving stations of bistatic radar and centroid O of said targetmThe difference of the sum of the distances between the transmitting station and the receiving station of the bistatic radar may include:
according to the target centroid OmAnd the scattering point PmCalculating the scattering point PmThe sum of the distances to a transmitting station and a receiving station of the bistatic radar;
in the bistatic radar system, the distance between the center of mass O of the target and the scattering point P from the target is far less than the distance between the receiving and transmitting pairs in the bistatic radar, because the distance between the receiving and transmitting pairs is alpham＝θm+α0Then scattering point PmSum of distances to transmitting and receiving stations of bistatic radar
Figure BDA0002934119890000081
Then
Figure BDA0002934119890000082
Wherein R isPmRepresents the scattering point PmSum of distances, R, to transmitting and receiving stations of bistatic radarTPmRepresents the scattering point PmDistance to transmitting station of bistatic radar, RRPmRepresents the scattering point PmThe distance to the receiving station of the bistatic radar, d represents the distance from the centroid O of the target to the scattering point P at the moment t, betamIs shown at tmAngle of double ground, alpha, corresponding to time0Representing the structure of the object centroid O and scattering point PAngle of resultant ray with respect to axis of abscissa, thetamIndicating the view angle change of the bistatic radar equivalent monostatic radar.
According to said scattering point PmCalculating the sum of the distances from the transmitting station and the receiving station of the bistatic radar and the slow time function and the accumulated rotation angle in the coherent processing time, and calculating the scattering point PmDistance to transmitting and receiving stations of bistatic radar and centroid O of said targetmThe difference of the sum of the distances to the transmitting station and the receiving station of the bistatic radar;
let R in formula (6)Om＝RTOm+RROmI.e. the target centroid OmThe sum of the distances to the transmitting and receiving stations of the bistatic radar, the scattering point PmDistance to transmitting station and receiving station of bistatic radar and centroid O of targetmThe difference between the sum of the distances to the transmitting and receiving stations of the bistatic radar is DeltaRPmThe bistatic angle beta is given a far-field position of the target within a short coherent processing time CPImCan be regarded as a function of the slow time, denoted as beta (t)m) And the cumulative rotational angle is represented by θ (t)m) Then, then
Figure BDA0002934119890000091
Wherein, Δ RPmRepresents the scattering point PmDistance to transmitting and receiving stations of bistatic radar and centroid O of said targetmDifference of sum of distances, theta (t), between a transmitting station and a receiving station of a bistatic radarm) Representing the cumulative rotation angle, x, over the coherent processing timepRepresenting the abscissa value of the scattering point P in an xOy coordinate system, wherein the xOy coordinate system is a right-hand rectangular coordinate system established by taking the target centroid O as the origin and taking the bipartite ground angle bisector as the y axis, and ypRepresents the ordinate value, β (t), of the scattering point P in the xOy coordinate systemm) Representing a function of slow time within the coherent processing time.
Optionally, the above-mentioned performing envelope alignment, phase self-focusing and over-range unit migration correction on each one-dimensional range profile in the one-dimensional range profile sequence according to the difference to obtain corrected one-dimensional range profile echo data may be
Figure BDA0002934119890000101
That is, the formula (7) is introduced into the formula (4), and the corrected one-dimensional range profile echo data is obtained.
And 103, calculating a bistatic angle during imaging of the bistatic ISAR image according to the radar station position information of the bistatic radar and the track information of the target, and calculating a bistatic time-varying coefficient according to the bistatic angle.
Optionally, referring to fig. 2, in this step, calculating a bistatic angle during imaging of the bistatic ISAR image according to the radar station position information of the bistatic radar and the orbit information of the target, and calculating a bistatic time-varying coefficient according to the bistatic angle may include:
according to
Figure BDA0002934119890000102
Calculating bistatic angles during bistatic ISAR image imaging; wherein, β (t)0) Representing the corresponding dihedral angle, β (t), imaged at time tm) Is shown at tmImaging the corresponding biprimary angle, R, at a timeTORepresenting the distance of the centroid O of the target from the transmitting station of the bistatic radar, RRORepresenting the distance of the target centroid O to the receiving station of the bistatic radar, L representing the length of the bistatic radar system baseline, RTOmRepresenting the center of mass O of the objectmDistance to transmitting station of bistatic radar, RROmRepresenting the center of mass O of the objectmDistance to a receiving station of the bistatic radar;
according to the bistatic angle and the first definition during the imaging of the bistatic ISAR image, calculating by using the minimum mean square error to obtain a bistatic time-varying coefficient; the first definition is beta (t)m)≈β0+ΔβtmWherein, β0Representing a double-base angle at the initial imaging moment, and delta beta representing a first derivative of the double-base angle at the initial imaging moment; beta is a0And delta beta is a bistatic time-varying coefficient；
And determining the value of the bistatic time-varying coefficient according to the bistatic time-varying coefficient.
Optionally, in a short coherent processing time CPI, the bistatic angle is approximately linearly changed with slow time under the condition that the target is at a far-field position, so that a first-order taylor polynomial can be used for approximation
β(tm)≈β0+Δβtm； (9)
Under short-time imaging conditions, cos (beta (t) by the minimum mean square error estimation methodm) /2) can be approximated by a Taylor polynomial
Figure BDA0002934119890000111
In the formula (10), the first and second groups,
Figure BDA0002934119890000112
the value of the bistatic time-varying coefficient may be determined.
Wherein, K0、K1Respectively, representing the values of the bistatic time-varying coefficients.
And 104, correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time varying coefficient, and determining the skew phase of the bistatic ISAR image.
Optionally, in this step, the correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time varying coefficient, and determining the phase of the bistatic ISAR image skew may include:
according to the target equivalent accumulated rotation angle and the bistatic time-varying coefficient pair Delta RPmSimplified treatment is carried out to obtain treated delta RPm'；
According to the treated delta RPm' and correcting the linear distance walking term by the corrected one-dimensional range profile echo data, and determining a corresponding phase polynomial signal of the nth range unit;
and determining the skew phase of the bistatic ISAR image according to the corresponding phase polynomial signal of the nth distance unit.
Alternatively, in a short CPI time, the target equivalent cumulative rotation angle is rotated by a slight angle due to the inertia of the target, which may be expressed as θ (t)m)＝ω0tm，θ(tm) For a target equivalent cumulative angle of rotation, ω0Is the target equivalent rotational speed. In this case, sin θ (t) in formula (7)m) And cos θ (t)m) Can be approximated as sin θ (t)m)≈ω0tm，cosθ(tm) 1. Neglecting higher-order terms with more than two orders, simplifying the rotation term of the scattering point to obtain the processed delta RPm'；
Figure BDA0002934119890000113
If the envelope motion caused by the rotation term exceeds half of the distance resolution unit and the Keystone method is used for correcting the linear distance motion term, the corresponding phase polynomial signal of the nth distance unit can be expressed as
Figure BDA0002934119890000121
Wherein A isiIndicating the amplitude of the echo at the ith scattering point, i-1, 2 … Ln，LnDenotes the total number of scattering points, ynRepresenting a longitudinal distance coordinate value, xiAnd represents the lateral distance coordinate value of the ith scattering point.
As can be seen from equation (12), the first part of the phase expression is associated with the longitudinal distance coordinate ynThe relevant distance space-variant phase terms, i.e. the first order term exp (-j4 π f) in relation to slow timecynK1tmAnd/c) causes all scattering points of the nth range unit to translate, and the translation amount is in direct proportion to the range coordinate, thereby causing the bistatic ISAR image to be skewed. Thus, the determined bistatic ISAR image skew has a phase exp (-j4 π fcynK1tm/c)。
A schematic diagram of a scattering point model of an image skew diagram shown in fig. 3(a), and a schematic diagram of imaging a bistatic ISAR image of an image skew diagram shown in fig. 3 (b). Distance coordinate y of scattering point and Doppler information due to bistatic ISARPThe values are related, so that scattering points deviate in the azimuth direction, the bistatic ISAR imaging result obtained by directly adopting the RD algorithm cannot effectively reflect the real shape of the target, and the subsequent target identification is influenced
And 105, constructing a phase change compensation item, and compensating the skew phase of the bistatic ISAR image according to the phase change compensation item to obtain the bistatic ISAR image after skew correction.
Optionally, the phase change compensation term is
Figure BDA0002934119890000122
Where Φ represents the phase change compensation term, ynIndicating a longitudinal distance coordinate value.
The formula (12) is compensated by adopting the formula (13), and a compensated exponential term is obtained
Figure BDA0002934119890000123
In the formula (14), doppler is only a function of the orientation coordinate of the scattering point, the image skew correction is eliminated, and the orientation coordinate value of the scattering point can be obtained according to the doppler information corresponding to the formula (14).
According to the bistatic ISAR image skew correction method, simulation verification is carried out, a transmitting station of a bistatic radar is arranged in Beijing city (116 degrees to 24'17 degrees to east longitude, 39 degrees to 54'27 degrees to north latitude, and 0m of altitude), a receiving station is arranged in Shanghai city (121 degrees to 4'20 degrees to east longitude, 39 degrees to north latitude, 02'37 degrees to north latitude, and 0m of altitude), a track of an international space station is used as a simulation verification track, the number of tracks TLE information of the international space station is shown in figure 4, and the initial epoch time of the track is 28 minutes 20 seconds at 20 days 00 of 8 months and 20 days of 2018 years.
According to the satellite orbit information, the visible time window of the international space station to the bistatic ISAR radar system can be calculated as follows: and 8, 2018, 20, 01:36: 51-01: 45:03, and selecting a specific CPI with a stable imaging plane as an imaging arc segment from a visible time window. The simulation scenario is shown in fig. 5. The simulated imaging parameter settings are shown in figure 6. When a scattering point model is adopted for simulation, a space shuttle model based on ideal scattering points is adopted, and the reflection coefficients of the scattering points are all 1. Wherein, fig. 7 is the projection of the scattering point model on the imaging plane along the view direction of the equivalent monostatic radar.
The change of the bistatic angle along with the number of accumulated pulses is shown in fig. 8, the accumulation time of fig. 8 is 5.12s, the bistatic angle and the slow time are in a linear relationship in the observation time, the change of the bistatic angle is about 3.46 degrees in the observation time, and the corresponding K is0＝0.6618，K1＝0.0044。
The method comprises the steps of performing envelope alignment by using an accumulative cross-correlation method, completing phase self-focusing by using a weighted least square self-focusing algorithm, completing migration correction of a distance-crossing unit by using keystone transformation, directly performing azimuth compression based on an RD algorithm, and calibrating to obtain a two-dimensional ISAR image as shown in fig. 9 (a). Due to the influence of bistatic time-varying angles, the two-dimensional ISAR image obtained based on the RD algorithm is skewed with respect to the scattering point model projection on the imaging plane along the equivalent single-base ground line of sight of 'gaze' in FIG. 7.
And (3) performing distance space-variant phase compensation on the echo data after the migration correction of the distance-crossing unit, and completing azimuth compression by distance-by-distance units to obtain a bistatic ISAR two-dimensional image as shown in fig. 9 (b). The ISAR image in the image (b) is consistent with the scattering point model projection on the imaging plane along the equivalent single-base ground sight line of the staring of the image (7), and a two-dimensional ISAR image which is consistent with the target projection shape can be obtained by using the algorithm, so that the effectiveness of the algorithm is verified, and the later-stage correct target identification is facilitated. And based on fig. 9(b), it can be seen that the bistatic ISAR image skew correction method of the present invention can effectively image to obtain the correct image shape and characteristics of the target, and based on the spatial target orbit and bistatic imaging geometric prior information, the proposed algorithm estimates the linear function coefficient of the bistatic angle and the corresponding coefficient by the least mean square error method. Under the condition that each double-base angle has a small random error, the corresponding coefficient can be accurately estimated based on the constraint of minimum mean square error, and the algorithm is more robust and is more suitable for an actual system.
According to the bistatic ISAR image skew correction method, the obtained one-dimensional range profile sequence is corrected to obtain corrected one-dimensional range profile echo data, a bistatic angle during imaging of the bistatic ISAR image is calculated according to radar station position information of the bistatic radar and track information of a target, and a bistatic time-varying coefficient is calculated according to the bistatic angle; correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time-varying coefficient, and determining the skew phase of the bistatic ISAR image; and then, setting a phase change compensation item to compensate the skew phase of the bistatic ISAR image, and performing azimuth compression to obtain a skew-corrected bistatic ISAR image two-dimensional image. The bistatic ISAR image skew correction method provided by the invention can effectively and robustly correct the image skew phenomenon caused by bistatic angular time variation, improves the imaging quality and is beneficial to subsequent target identification.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.

Claims (10)

1. A bistatic ISAR image skew correction method is characterized by comprising the following steps:
performing pulse compression on a received target echo signal of the bistatic radar to obtain a one-dimensional range profile sequence;
preprocessing each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data;
according to the radar station position information of the bistatic radar and the track information of a target, calculating a bistatic angle during imaging of a bistatic ISAR image, and according to the bistatic angle, calculating a bistatic time-varying coefficient;
correcting a linear distance walking term according to the corrected one-dimensional range profile echo data and the bistatic time-varying coefficient, and determining the skew phase of the bistatic ISAR image;
and constructing a phase change compensation item, and compensating the skew phase of the bistatic ISAR image according to the phase change compensation item to obtain the bistatic ISAR image after skew correction.
2. The bistatic ISAR image skew correction method of claim 1, wherein the one-dimensional range profile in the one-dimensional range profile sequence is
Figure FDA0002934119880000011
Wherein the content of the first and second substances,
Figure FDA0002934119880000012
is shown at tmMoment scattering point PmOne-dimensional range profile of (a)PIs shown at t0The scattering coefficient of the scattering point P at the moment, mu, represents the frequency modulation rate of the bistatic radar, TpWhich represents the pulse width of the bistatic radar,
Figure FDA0002934119880000013
denotes fast time, RPmRepresents the scattering point PmThe sum of the distances to the transmitting station and the receiving station of the bistatic radar, c represents the electromagnetic wave in free spaceInter propagation velocity, j denotes an imaginary number, fcRepresenting the carrier frequency of the pulses transmitted by the bistatic radar.
3. The bistatic ISAR image skew correction method of claim 1, wherein said pre-processing each one-dimensional range profile in said sequence of one-dimensional range profiles to obtain corrected one-dimensional range profile echo data comprises:
is obtained at t0Position data of the centroid O of the object at time tmMoment scattering point PmThe location data of (a);
from the position data of the object centroid O and the scattering point PmCalculating said scattering point PmThe difference between the sum of the distances to the transmitting station and the receiving station of the bistatic radar and the sum of the distances to the transmitting station and the receiving station of the target centroid O bistatic radar;
and according to the difference, carrying out envelope alignment, phase self-focusing and over-range unit migration correction on each one-dimensional range profile in the one-dimensional range profile sequence to obtain corrected one-dimensional range profile echo data.
4. The bistatic ISAR image skew correction method according to any one of claims 1-3, wherein calculating bistatic angles during imaging of bistatic ISAR images from radar station position information of the bistatic radar and orbit information of a target comprises:
according to
Figure FDA0002934119880000021
Calculating bistatic angles during bistatic ISAR image imaging; wherein, β (t)0) Is shown at t0Imaging the corresponding biprimary angle, beta (t), at a timem) Is shown at tmImaging the corresponding biprimary angle, R, at a timeTORepresenting the distance of the centroid O of the target from the transmitting station of the bistatic radar, RRORepresenting the distance of the target centroid O to the receiving station of the bistatic radar, L representing the length of the bistatic radar system baseline, RTOmRepresenting a target substanceHeart OmDistance to transmitting station of bistatic radar, RROmRepresenting the center of mass O of the objectmDistance to the receiving station of the bistatic radar.
5. A bistatic ISAR image skew correction method according to any one of claims 1-3, wherein calculating a bistatic time-varying coefficient from the bistatic angle comprises:
according to the bistatic angle and the first definition during the imaging of the bistatic ISAR image, calculating by using the minimum mean square error to obtain a bistatic time-varying coefficient; the first definition is beta (t)m)≈β0+ΔβtmWherein, β0Representing a double-base angle at the initial imaging moment, and delta beta representing a first derivative of the double-base angle at the initial imaging moment;
and determining the value of the bistatic time-varying coefficient according to the bistatic time-varying coefficient.
6. The bistatic ISAR image skew correction method of claim 5, wherein said determining a value of said bistatic time-varying coefficient from said bistatic time-varying coefficient comprises:
according to
Figure FDA0002934119880000031
Determining a value of the bistatic time-varying coefficient;
wherein, K0、K1Respectively, representing the values of the bistatic time-varying coefficients.
7. The bistatic ISAR image skew correction method of any of claims 1-3, wherein said correcting a linear range walk term from said corrected one-dimensional range image echo data and said bistatic time varying coefficients, determining a phase of bistatic ISAR image skew, comprises:
according to the target equivalent accumulated rotation angle and the bistatic time-varying coefficient pair Delta RPmSimplified treatment is carried out to obtain treated delta RPm'；
According to the treated delta RPm' and correcting the linear distance walking term by the corrected one-dimensional range profile echo data, and determining a corresponding phase polynomial signal of the nth range unit;
and determining the skew phase of the bistatic ISAR image according to the corresponding phase polynomial signal of the nth distance unit.
8. The bistatic ISAR image skew correction method of claim 7, wherein the processed Δ RPm' is
Figure FDA0002934119880000032
Wherein, ω is0Representing target equivalent rotational speed, xpRepresenting the abscissa value of the scattering point P in an xOy coordinate system, wherein the xOy coordinate system is a right-hand rectangular coordinate system established by taking the target centroid O as the origin and taking the bipartite ground angle bisector as the y axis, and ypRepresenting the ordinate value of the scattering point P in the xOy coordinate system;
the corresponding phase polynomial signal of the nth distance unit is
Figure FDA0002934119880000033
Wherein s isn(tm) Representing the corresponding phase polynomial signal of the nth range cell, AiIndicating the amplitude of the echo at the ith scattering point, i-1, 2 … Ln，LnDenotes the total number of scattering points, ynRepresenting a longitudinal distance coordinate value, xiAnd represents the lateral distance coordinate value of the ith scattering point.
9. The bistatic ISAR image skew correction method of claim 8, wherein the phase change compensation term is
Figure FDA0002934119880000041
Wherein the content of the first and second substances,
Figure FDA0002934119880000042
representing a phase change compensation term.
10. The bistatic ISAR image skew correction method of claim 9, wherein the exponent term of the skew-corrected bistatic ISAR image is
Figure FDA0002934119880000043
Where ψ' denotes an exponential term of the skew-corrected bistatic ISAR image.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116482687A (en) * 2023-06-25 2023-07-25 中国科学院空天信息创新研究院 Amplitude-variable target ISAR imaging translational compensation method based on minimum mean square error

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014149095A2 (en) * 2013-03-20 2014-09-25 Raytheon Company Bistatic inverse synthetic aperture radar imaging
CN108845301A (en) * 2018-08-17 2018-11-20 中国人民解放军陆军工程大学 A kind of target Equivalent rotation center estimation method for bistatic ISAR
CN109633644A (en) * 2018-12-27 2019-04-16 中国人民解放军陆军工程大学 A kind of ISAR Imaging of Maneuvering Targets method
CN109655829A (en) * 2018-12-27 2019-04-19 北京冠群桦成信息技术有限公司 Bistatic ISAR image distortion correction method
CN109782279A (en) * 2019-01-21 2019-05-21 中国人民解放军陆军工程大学 A kind of compressed sensing based bistatic ISAR imaging method

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014149095A2 (en) * 2013-03-20 2014-09-25 Raytheon Company Bistatic inverse synthetic aperture radar imaging
CN108845301A (en) * 2018-08-17 2018-11-20 中国人民解放军陆军工程大学 A kind of target Equivalent rotation center estimation method for bistatic ISAR
CN109633644A (en) * 2018-12-27 2019-04-16 中国人民解放军陆军工程大学 A kind of ISAR Imaging of Maneuvering Targets method
CN109655829A (en) * 2018-12-27 2019-04-19 北京冠群桦成信息技术有限公司 Bistatic ISAR image distortion correction method
CN109782279A (en) * 2019-01-21 2019-05-21 中国人民解放军陆军工程大学 A kind of compressed sensing based bistatic ISAR imaging method

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
LIN SHI,ET AL: "Bistatic-ISAR Linear Geometry Distortion Alleviation of Space Targets", 《ELECTRONICS》 *
史林等: "基于虚拟慢时间的双基地ISAR成像算法", 《航空学报》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116482687A (en) * 2023-06-25 2023-07-25 中国科学院空天信息创新研究院 Amplitude-variable target ISAR imaging translational compensation method based on minimum mean square error
CN116482687B (en) * 2023-06-25 2023-08-15 中国科学院空天信息创新研究院 Amplitude-variable target ISAR imaging translational compensation method based on minimum mean square error

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