CN110231616B - Sea surface moving target detection and positioning method based on Beidou satellite radiation source - Google Patents
Sea surface moving target detection and positioning method based on Beidou satellite radiation source Download PDFInfo
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Abstract
The invention discloses a sea surface moving target detection and positioning method based on a Beidou satellite radiation source, which is applied to the field of radar moving target detection and aims at solving the problem that the echo signal-to-noise ratio of a Beidou satellite serving as an external radiation source target in the prior art is low; firstly, symmetrical Keystone transformation is adopted for target echoes received from different Beidou satellites to obtain a range migration correction result; then, performing framing processing and deskew-FFT on the echo signals after the range migration correction to obtain an accumulation result of each echo signal; secondly, the accumulation results of all the echoes are back projected to a local coordinate system according to the difference bistatic distance to obtain the accumulation results of a plurality of echoes, so that the effective accumulation of the energy of target echo signals obtained by different Beidou satellites when the Beidou satellites are radiation sources is realized; and finally, detecting and positioning the target according to the accumulation result of the plurality of echoes in the step S3.
Description
Technical Field
The invention belongs to the field of radar moving target detection, and particularly relates to a passive radar moving target detection and positioning technology based on a satellite radiation source.
Background
Passive radar is a special type of dual (multi) base passive radar system. Unlike conventional radars, passive radars do not emit electromagnetic signals themselves, but rather utilize electromagnetic waves radiated by a target for target detection. The passive radar does not emit electromagnetic waves, so that the passive radar has strong concealment; meanwhile, the size can be reduced, and the cost is reduced. In recent years, with the increase of the kinds and the number of signals of passive radar illumination sources, the research on passive radars is increasing.
Most of the existing passive radars use ground signals as signal sources, but because they can only cover land areas, but cannot completely cover ocean areas, they are not suitable for large-scale sea surface monitoring. To this problem, can select big dipper satellite signal as the radiation source. The big dipper satellite signal has incomparable advantage as the radiation source to other space electromagnetic signal: the method comprises the steps that a satellite signal can cover a sea surface; the anti-interference performance is strong; the satellite signal characteristics are known, so that target detection is facilitated; the Beidou satellite is independently researched and developed in China, and the signal safety is high when the Beidou satellite is used. Therefore, the monitoring of the sea surface by using the Beidou satellite signals is a feasible development direction.
The power of the Beidou satellite transmitting signal is low and the Beidou satellite transmitting signal is far away from the ground, so that the power density of the Beidou satellite signal reaching the earth surface is low, the signal-to-noise ratio of the received sea surface moving target echo signal is extremely low, and the difficulty is brought to the detection of the sea surface moving target.
In order to improve the signal-to-noise ratio of a sea surface moving target echo signal, the document 'Multi-frame fractional Fourier transform technique for moving target detection with space-based passive Radar, Iet Radar Source & Navigation,2017,11 (5)' 822-828 proposes a method for carrying out energy accumulation on the target echo signal under a long observation time, and the method firstly carries out first-order Keystone transformation on the echo signal after distance compression, thereby realizing distance migration correction; dividing the data after the range migration correction into multiple frames, and performing FrFT on each frame of data to realize coherent accumulation of the energy of the moving target; and finally, frequency alignment and incoherent accumulation are carried out among the data of multiple frames, so that the signal energy is highly accumulated to a Doppler centroid-Doppler frequency modulation (DC-DFR) domain. However, the first-order Keystone transformation adopted by the method can only eliminate first-order distance walk, and second-order distance bending still exists, so that distance migration correction cannot be accurately realized. Meanwhile, the method has the defects of large calculation amount and complicated process. In addition, the method only studies the condition that a single satellite is used as a radiation source, and the positioning of the sea surface moving target cannot be realized.
Disclosure of Invention
In order to solve the technical problems, the invention provides a passive radar sea surface moving target detection and positioning method based on a Beidou satellite radiation source, which can effectively realize the detection and positioning of the sea surface moving target by taking a plurality of Beidou satellites as radiation sources.
The technical scheme adopted by the invention is as follows: a passive radar sea surface moving target detection and positioning method based on a Beidou satellite radiation source comprises the following steps:
s1, symmetrical Keystone transformation is adopted for the received target echoes from different Beidou satellites to obtain a range migration correction result;
s2, performing framing processing and deskew-FFT on the echo signals after the migration correction of each range to obtain an accumulation result of each echo signal;
s3, back projecting the accumulation result of each echo to a local coordinate system according to the difference bistatic distance, and performing incoherent accumulation on the accumulation result of each echo in the local coordinate system;
and S4, detecting and positioning the target according to the incoherent accumulation result of the plurality of echoes in the step S3.
Further, step S1 includes:
s11, initializing system parameters, wherein the initialized parameters comprise: distance direction sampling frequency, target observation time and equivalent signal pulse repetition time;
s12, adopting a plurality of Beidou satellites as radiation sources, and respectively recording and demodulating the direct wave and the target echo by two antennas;
s13, performing relevant processing on the direct waves and the target echoes corresponding to the obtained Beidou satellites as radiation sources to obtain the result of pulse compression of the distance direction of the target echoes corresponding to the Beidou satellites as radiation sources;
and S14, carrying out symmetrical Keystone conversion on the range of each target echo to the result after pulse compression to obtain a range migration correction result corresponding to each target echo.
Further, step S14 includes the following substeps:
a1, performing range-to-fast Fourier transform on the range migration correction result corresponding to each target echo to obtain a range frequency domain-azimuth time domain signal corresponding to each target echo;
a2, carrying out positive second-order Keystone transformation on the distance frequency domain-azimuth time domain signals corresponding to the target echoes;
a3, carrying out negative second-order Keystone transformation on the distance frequency domain-azimuth time domain signals corresponding to the target echoes;
a4, multiplying the result obtained in the step A2 corresponding to each target echo by the result obtained in the step A3;
and A5, performing inverse range-to-fast Fourier transform on the multiplication result obtained in the step A4 corresponding to each target echo to obtain a range migration correction result corresponding to each target echo.
Further, step S2 includes:
s21, taking the same range gate signal for the range migration correction result corresponding to a certain target echo to obtain a corresponding direction signal;
s22, carrying out uniform deskew processing on the azimuth signal and dividing the azimuth signal into a plurality of frames;
s23, carrying out coherent accumulation of intraframe signals and incoherent accumulation of interframe signals on the depolarised azimuth signals;
s24, executing steps S23-S24 to the residual range gate signal of the range migration correction result corresponding to the target echo to obtain the accumulation result of the single echo signal in the differential double-base range-Doppler frequency modulation domain.
Further, step S22 includes the following substeps:
b1, setting the range of Doppler frequency modulation and the frequency modulation interval value;
b2, forming a group of linear frequency modulation signals according to the frequency modulation interval value;
b3, multiplying the extracted azimuth signal by linear frequency modulation signals with different frequency modulation rates respectively to obtain a two-dimensional signal;
b4, dividing the two-dimensional signal obtained in the step B3 into a plurality of frames according to the determined time length of one frame.
Further, step S23 includes the following substeps:
c1, directly adding values corresponding to each azimuth time of each frame of signal to obtain a zero frequency value of each frame of signal under the condition of different frequency modulation values;
and C2, performing incoherent accumulation on the zero frequency value of each frame of signal under the condition of different frequency modulation values to obtain the zero frequency value of the signal under the condition of different frequency modulation values.
Further, step S3 includes:
s31, constructing a local coordinate system, wherein coordinate axes of the local coordinate system are respectively a position X, a position Y and a Doppler frequency modulation frequency;
s32, dividing the sea surface scene into grids to obtain the space coordinate of each grid;
s33, for each grid, obtaining differential double-base distances corresponding to different Beidou satellites according to the spatial positions of the Beidou satellites and the receiving station, and further obtaining distance direction time corresponding to the different satellites;
s34, substituting the distances corresponding to the different satellites obtained in the step S33 into the incoherent accumulation result obtained in the step S23 to obtain one-dimensional Doppler frequency modulation signals corresponding to each grid;
s35, directly performing incoherent accumulation on the one-dimensional Doppler frequency modulation signals corresponding to each Beidou satellite under the current grid;
s36, obtaining a three-dimensional signal in a local coordinate system according to the incoherent accumulation results of all Beidou satellites under all grids obtained in the step S35, and the method has the advantages that: firstly, symmetrical Keystone transformation is adopted for target echoes received from different Beidou satellites to obtain a range migration correction result; secondly, performing framing and deskew-FFT processing on the echo signals after the range migration correction to obtain an accumulation result of each echo signal; then, back projecting the accumulation result of each echo to a local coordinate system according to the difference bistatic distance to obtain the accumulation results of a plurality of echoes; finally, detecting and positioning the target according to the accumulation results of the multiple echoes; the problem that the signal to noise ratio of the echo of the Beidou satellite as an external radiation source target is low is effectively solved; the method of the invention has the following advantages:
1. the invention provides the detection and the positioning of a plurality of Beidou satellites as external radiation sources on a sea surface moving target for the first time;
2. by adopting symmetric Keystone transformation, the range walk and range bend can be removed at the same time under the condition of unknown Doppler parameters, the range migration correction is better realized, and the Doppler centroid is zero;
3. when single satellite echo energy accumulation processing is carried out, values corresponding to all azimuth time are directly added, and the calculated amount is greatly reduced;
4. according to the differential double-base distance, the accumulation results of the sea surface moving target echoes obtained by the Beidou satellites are reversely projected to a local coordinate system, and the accumulation results of the sea surface moving target echoes of the Beidou satellites are directly subjected to incoherent accumulation under the local coordinate system, so that the effective accumulation of different echo signal energies is better realized.
Drawings
FIG. 1 is a schematic flow chart provided by an embodiment of the present invention;
fig. 2 is a schematic diagram of a geometric configuration of a passive radar based on a Beidou satellite radiation source according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating an energy accumulation result of a target echo in a local coordinate system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an X-Y cross section at the peak of the accumulation provided by an embodiment of the present invention.
Detailed Description
The invention aims to solve the problem that the signal-to-noise ratio of the received moving target echo signal by taking the Beidou satellite as a radiation source is extremely low, and the observation time of the target is increased. Under the condition of long observation time, the range walk and the range bend cannot be ignored, and the method adopts symmetrical Keystone transformation, can simultaneously eliminate the range walk and the range bend under the condition of unknown Doppler parameters, and realizes accurate range migration correction. Because the change of the target scattering characteristic can not be directly subjected to coherent accumulation under a long observation time, the method adopts a framing processing method, and treats the intra-frame signals as coherent, performs coherent accumulation on the intra-frame signals, and performs incoherent accumulation on the inter-frame signals. The invention adopts uniform deskewing processing to the signals after the symmetrical Keystone transformation processing, and can accumulate all the energy of the completely deskewed signals to the Doppler centroid through Fourier transformation, and the Doppler centroid of the signals becomes zero through the symmetrical Keystone transformation. Therefore, for the intra-frame signals, signals with different azimuth time can be directly added, so that energy is gathered at zero frequency; meanwhile, different frames adopt uniform deskew processing, and the Doppler centroid is unchanged, so that Doppler centroid compensation processing is not needed in interframe non-coherent processing. The target echo energy accumulation effect taking a single Beidou satellite as a radiation source is poor, and the target cannot be detected in a noise background. The invention adopts a plurality of Beidou satellites as radiation sources to accumulate the target echo energy. When a plurality of Beidou satellites are used as radiation sources, the accumulation results of sea surface moving target echoes using different Beidou satellites as radiation sources can be obtained by processing according to the steps, and then the sea surface moving target echoes are reversely projected to a local coordinate system for incoherent accumulation. The invention has the outstanding advantages of good target echo energy accumulation effect and capability of simultaneously detecting and positioning the target.
In order to facilitate the understanding of the technical contents of the present invention by those skilled in the art, the present invention will be further explained with reference to the accompanying drawings.
The geometric configuration diagram of this embodiment is shown in fig. 2, the receiving station is fixed, the Beidou satellite serving as the radiation source is selected to be a medium-circle earth orbit (MEO) satellite, a B3I signal broadcast by the Beidou satellite is selected to be an external radiation source signal, and the carrier frequency f of the external radiation source signal isc1268.520MHz, and the signal bandwidth is 20.46 MHz. In this embodiment, 5 Beidou satellites are selected as radiation sources, and a position vector of a sea surface moving object at a reference time is represented as (1000,0,0) m.
The technical scheme adopted by the invention is as shown in figure 1, and comprises six parts which are sequentially as follows: 1. initializing system parameters; 2. recording the direct wave and the target echo, and performing range pulse compression; 3. symmetric Keystone transformation; 4. unified deskew processing and framing; 5. accumulating a single satellite; 6. and (4) reversely projecting the two-dimensional signal in the step (5) to a local coordinate system according to the difference double-base distance, and performing incoherent accumulation on the accumulation results of the sea surface moving object echoes obtained by different Beidou satellites.
The invention mainly adopts a simulation experiment method for verification, and all the steps and conclusions are verified to be correct on Matlab.
The specific implementation process of the invention is as follows:
1. initializing system parameters:
the specific initialized parameters include: range-wise sampling rate fsEquivalent signal pulse repetition frequency PRF, target observation time Ta(ii) a In this example fsThe value is 50MHz, the PRF value is 1000Hz in this embodiment, and T is T in this embodimentaThe value is 60 s.
2. Recording the direct wave and the target echo, and performing range pulse compression:
the number of Beidou satellites serving as radiation sources is M-5, the direct wave is recorded under the condition that the mth Beidou satellite is the radiation source, and a baseband direct wave signal s is obtained through demodulationd,m(tau, eta), recording the target echo, and demodulating to obtain a baseband target echo signal sr,m(τ, η), wherein τ is the range time, η is the azimuth time, η is the range of [ -30,30 [ -30 [ ]]s, M1, 2., M, subscript d denotes the direct wave and subscript r denotes the target scattered echo.
Secondly, the direct wave signal and the target echo signal are processed in a correlation mode, and the result obtained after the target echo signal is compressed in the range direction pulse is as follows:
where the subscript pc denotes pulse compression, σηThe complex scattering coefficient of the target, whose value varies with time, c is the speed of light, ρ (-) is the cross-correlation function of the echo signal and the direct wave reference signal, where ρ (-) is a triangular wave, and R (η) is the history of the differential bistatic distance, which can be expressed as:
R(η)＝Rt(η)+Rr(η)-Rb(η)
wherein R ist(η) and Rr(eta) represents the distance between the Beidou satellite and the receiving station to the target, Rb(η) represents the distance between the Beidou satellite and the receiving station, and R (η) can be expressed as a second-order Taylor expansion:
wherein R is0Denotes the value of R (η) at η ═ 0, and A, B denotes the values of the first and second derivatives of R (η) with respect to η at η ═ 0, respectively.
3. Symmetric Keystone transform:
firstly, performing distance-direction fast Fourier transform on a result obtained after the distance-direction pulse compression to obtain a distance frequency domain-azimuth time domain signal:
wherein P (-) is a Fourier transform of ρ (-) and has:
in the above formula, fτCoupling with eta causes distance walk, fτAnd η2Causes the distance to bend.
Secondly, the result in the first step is subjected to positive second-order Keystone conversion
While substituting eta for transformed result by etamObtaining:
wherein the content of the first and second substances,
from the above equation, the positive second order Keystone transform removes fτAnd η2I.e. the distance bending is removed.
Thirdly, the result in the first step is subjected to negative second-order Keystone transformation
While substituting eta for transformed result by etamObtaining:
wherein the content of the first and second substances,
from the above equation, the negative second order Keystone transform also removes the range warping.
Fourthly, multiplying the result in the fourth step by the result in the third step to obtain:
wherein the content of the first and second substances,
from the above equation, the symmetric Keystone transform can achieve simultaneous elimination of distance walk and distance warp.
Fifthly, performing inverse fast Fourier transform on the result obtained by the fourth step:
sSKT,m(τ,η)＝IFFTrg{SSKT,m(fτ,η)}
wherein the IFFTrgRepresenting the inverse fourier transform of the distance.
4. Unified deskew processing and framing:
taking out sSKT,mThe corresponding azimuth signal is obtained in the same distance to time in (tau, eta) and is marked as sm(η), s is obtained from step 3mThe Doppler centroid of (η) is zero, so only the true value of the Doppler modulation frequency needs to be considered
And is
The value of (a) is unknown. The setting comprises
The Doppler frequency modulation range of (1) in this embodiment is [ -1.25,1.25 [ ]]Hz/s, interval Δ fdrIs 0.005 Hz/s;
secondly, according to the Doppler frequency modulation value f in the first stepdrForm a set of LFM (linear frequency modulation) signals, i.e., sLFM(fdr,η)＝exp(-jπfdrη2) The set of LFM signals sLFM(fdrEta) and sm(eta) to obtain a two-dimensional signal sdechirp,m(fdr,η)；
③ 2s is selected as the time length T of each frame in the embodimentfraA1 is todechirp,m(fdrEta) is divided into 30 frames in azimuth time, taking into account the ith frame signal sm,i(fdrEta) corresponding to eta in the range of [ -32+2i, -30+2i]And s. The complex scattering coefficient sigma can be ignored due to the intra-frame signalηThe influence is that the ith frame can be transmitted without considering the amplitude and neglecting the constant phaseThe numbers are indicated as:
5. coherent accumulation is carried out on the signals in the frame, and incoherent accumulation is carried out on the signals between the frames:
(ii) dividing each frame signal sm,i(fdrEta) at different fdrAdding the corresponding values of the time in the lower directions to obtain different fdrAt zero frequency value of the signal of each frame, i.e.
When the selected Doppler modulation frequency fdrWith actual Doppler modulation
When equality is achieved, that is, complete deskew is performed, only the value range of η is considered, and the constant phase is ignored, so that each frame signal can be expressed as:
according to the formula, the energy of the signal can be accumulated to a zero frequency position through Fourier transform, and the required zero frequency value is obtained by directly adding values corresponding to different azimuth time, so that the intra-frame signal energy accumulation result is obtained.
Secondly, the results obtained in the first step are subjected to inter-frame incoherent accumulation to obtain different fdrZero frequency values corresponding to a 60s signal under conditions, i.e.
Because energy is accumulated to the zero frequency position by each frame signal when the inclination is completely removed, Doppler centroid compensation is not needed for the inter-frame signals, and the zero frequency value obtained by incoherent accumulation is directly carried out, so that the energy accumulation result of the 60s signal is obtained.
Since the distance of the existing target is unknown in time, it needs to be from sSKT,m(τ,η) Taking out signals of different distance direction time to obtain corresponding smAnd (eta), repeating the processing flow of 4-5 to obtain a two-dimensional accumulation result of the single echo. Accumulating different echoes to obtain two-dimensional accumulation results s of multiple echoesm(τ,fdr),m＝1,2,...,M；
6. Constructing a local coordinate system, reversely projecting the two-dimensional signals in the step 5 to the local coordinate system according to the differential double-base distance, and performing incoherent accumulation on the accumulation results of sea surface moving target echoes obtained by different Beidou satellites:
firstly, constructing a local coordinate system, wherein the coordinates of the local coordinate system are respectively position X, position Y and Doppler frequency modulation;
and secondly, dividing the sea surface scene into grids, and setting the space coordinate of each grid as (x, y, 0).
Thirdly, a grid is taken out from the second step, because the positions of the satellites are known, the positions of the receiving stations are fixed, the differential distances corresponding to different satellites can be obtained, and the fast time tau corresponding to different satellites can be obtained1,...,τm,...,τM。
Substituting the result in the third step into the two-dimensional signal s in the step 5m(τ,fdr) In the method, a one-dimensional signal s corresponding to the grid is obtainedm(τ＝τm,fdr) Directly performing incoherent accumulation on one-dimensional signals corresponding to different Beidou satellites, namely
Fifthly, processing all the grids in the step III according to the step III and the step IV to obtain a three-dimensional signal stotal(X,Y,fdr) According to the accumulation result, the detection of the target can be realized. According to the X and Y values corresponding to the peak value, the target positioning can be realized at the same time.
As can be seen from FIG. 3, the invention well realizes the effective accumulation of target echo signal energy obtained by different Beidou satellites when a plurality of Beidou satellites are used as radiation sources. As can be seen from the X-Y cross-sectional diagram of fig. 4, the position of the target in the background of the sea surface is (1000,0), which is consistent with the real position, and the positioning is well achieved. Therefore, the invention can effectively realize the detection and the positioning of the sea surface moving target which takes a plurality of Beidou satellites as radiation sources.
It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Various modifications and alterations to this invention will become apparent to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (7)
1. A sea surface moving target detection and positioning method based on a Beidou satellite radiation source is characterized by comprising the following steps:
s1, symmetrical Keystone transformation is adopted for the received target echoes from different Beidou satellites to obtain a range migration correction result; step S1 includes:
s11, initializing system parameters, wherein the initialized parameters comprise: distance direction sampling frequency, target observation time and equivalent signal pulse repetition time;
s12, adopting a plurality of Beidou satellites as radiation sources, and respectively recording and demodulating the direct wave and the target echo by two antennas;
s13, performing relevant processing on the direct waves and the target echoes corresponding to the obtained Beidou satellites as radiation sources to obtain the result of pulse compression of the distance direction of the target echoes corresponding to the Beidou satellites as radiation sources;
s14, carrying out symmetrical Keystone conversion on the range of each target echo to the result after pulse compression to obtain a range migration correction result corresponding to each target echo;
s2, performing framing processing and deskew-FFT on the echo signals after the migration correction of each range to obtain an accumulation result of each echo signal;
s3, back projecting the accumulation result of each echo to a local coordinate system according to the difference bistatic distance, and performing incoherent accumulation on the accumulation result of each echo in the local coordinate system;
and S4, detecting and positioning the target according to the incoherent accumulation result of the plurality of echoes in the step S3.
2. The method for detecting and positioning the sea surface moving object based on the Beidou satellite radiation source of claim 1, wherein the step S14 comprises the following substeps:
a1, performing range-to-fast Fourier transform on the range migration correction result corresponding to each target echo to obtain a range frequency domain-azimuth time domain signal corresponding to each target echo;
a2, carrying out positive second-order Keystone transformation on the distance frequency domain-azimuth time domain signals corresponding to the target echoes;
a3, carrying out negative second-order Keystone transformation on the distance frequency domain-azimuth time domain signals corresponding to the target echoes;
a4, multiplying the result obtained in the step A2 corresponding to each target echo by the result obtained in the step A3;
and A5, performing inverse range-to-fast Fourier transform on the multiplication result obtained in the step A4 corresponding to each target echo to obtain a range migration correction result corresponding to each target echo.
3. The method for detecting and positioning the sea surface moving object based on the Beidou satellite radiation source of claim 2, wherein the step S2 comprises:
s21, taking the same range gate signal for the range migration correction result corresponding to a certain target echo to obtain a corresponding direction signal;
s22, carrying out uniform deskew processing on the azimuth signal and dividing the azimuth signal into a plurality of frames;
s23, carrying out coherent accumulation of intraframe signals and incoherent accumulation of interframe signals on the depolarised azimuth signals;
s24, executing steps S23-S24 to the residual range gate signal of the range migration correction result corresponding to the target echo to obtain the accumulation result of the single echo signal in the differential double-base range-Doppler frequency modulation domain.
4. The method for detecting and positioning the sea surface moving object based on the Beidou satellite radiation source of claim 3, wherein the step S22 comprises the following substeps:
b1, setting the range of Doppler frequency modulation and the frequency modulation interval value;
b2, forming a group of linear frequency modulation signals according to the frequency modulation interval value;
b3, multiplying the extracted azimuth signal by linear frequency modulation signals with different frequency modulation rates respectively to obtain a two-dimensional signal;
b4, dividing the two-dimensional signal obtained in the step B3 into a plurality of frames according to the determined time length of one frame.
5. The method for detecting and positioning the moving object on the sea based on the Beidou satellite radiation source of claim 4, wherein the range of the Doppler modulation frequency in the step B1 comprises the true value of the Doppler modulation frequency.
6. The method for detecting and positioning the sea surface moving object based on the Beidou satellite radiation source of claim 5, wherein the step S23 comprises the following substeps:
c1, directly adding values corresponding to each azimuth time of each frame of signal to obtain a zero frequency value of each frame of signal under the condition of different frequency modulation values;
and C2, performing incoherent accumulation on the zero frequency value of each frame of signal under the condition of different frequency modulation values to obtain the zero frequency value of the signal under the condition of different frequency modulation values.
7. The method for detecting and positioning the sea surface moving object based on the Beidou satellite radiation source of claim 6, wherein the step S3 comprises:
s31, constructing a local coordinate system, wherein coordinate axes of the local coordinate system are respectively a position X, a position Y and a Doppler frequency modulation frequency;
s32, dividing the sea surface scene into grids to obtain the space coordinate of each grid;
s33, for each grid, obtaining differential double-base distances corresponding to different Beidou satellites according to the spatial positions of the Beidou satellites and the receiving station, and further obtaining distance direction time corresponding to the different satellites;
s34, substituting the distances corresponding to the different satellites obtained in the step S33 into the incoherent accumulation result obtained in the step S23 to obtain one-dimensional Doppler frequency modulation signals corresponding to each grid;
s35, directly performing incoherent accumulation on the one-dimensional Doppler frequency modulation signals corresponding to each Beidou satellite under the current grid;
and S36, obtaining a three-dimensional signal in the local coordinate system according to the incoherent accumulation results of all Beidou satellites under all grids obtained in the step S35.
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