CN115856883B - Bistatic radar collaborative imaging system based on complementary random waveforms - Google Patents
Bistatic radar collaborative imaging system based on complementary random waveforms Download PDFInfo
- Publication number
- CN115856883B CN115856883B CN202310108808.0A CN202310108808A CN115856883B CN 115856883 B CN115856883 B CN 115856883B CN 202310108808 A CN202310108808 A CN 202310108808A CN 115856883 B CN115856883 B CN 115856883B
- Authority
- CN
- China
- Prior art keywords
- radar
- echo
- module
- imaging
- frequency hopping
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000003384 imaging method Methods 0.000 title claims abstract description 88
- 230000000295 complement effect Effects 0.000 title claims abstract description 27
- 230000004927 fusion Effects 0.000 claims abstract description 43
- 230000033001 locomotion Effects 0.000 claims abstract description 39
- 238000001514 detection method Methods 0.000 claims abstract description 35
- 230000001427 coherent effect Effects 0.000 claims abstract description 16
- 238000012545 processing Methods 0.000 claims abstract description 15
- 238000002592 echocardiography Methods 0.000 claims description 23
- 238000000034 method Methods 0.000 claims description 21
- 238000012937 correction Methods 0.000 claims description 16
- 230000002950 deficient Effects 0.000 claims description 10
- 230000008707 rearrangement Effects 0.000 claims description 9
- 230000007547 defect Effects 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 6
- 230000005540 biological transmission Effects 0.000 claims description 5
- 238000006467 substitution reaction Methods 0.000 claims description 3
- 230000009466 transformation Effects 0.000 claims description 3
- 238000004422 calculation algorithm Methods 0.000 abstract description 9
- 238000013461 design Methods 0.000 abstract description 3
- 238000010586 diagram Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 230000006870 function Effects 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 230000001934 delay Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 101150114218 allB gene Proteins 0.000 description 1
- 238000013398 bayesian method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- CLOMYZFHNHFSIQ-UHFFFAOYSA-N clonixin Chemical compound CC1=C(Cl)C=CC=C1NC1=NC=CC=C1C(O)=O CLOMYZFHNHFSIQ-UHFFFAOYSA-N 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 238000005429 filling process Methods 0.000 description 1
- 238000007499 fusion processing Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 230000035485 pulse pressure Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
Images
Landscapes
- Radar Systems Or Details Thereof (AREA)
Abstract
The invention belongs to the technical field of radar imaging, and relates to a complementary random waveform-based bistatic radar collaborative imaging system, which comprises a radar I (1) and a radar II (2) which are respectively installed on two moving platforms accompanying flight, and a radar signal transmitting module (10), a radar signal receiving module (20), a distance difference correcting module (30), a target motion compensating module (40) and a frequency band fusion imaging module (50) which are deployed on a control platform, wherein the frequency band fusion imaging can be carried out, random frequency hopping of different frequency bands is rearranged, and the echo signals of the two radars are subjected to coherent fusion imaging through FFT (fast Fourier transform) by setting a tight constraint condition. The bistatic radar collaborative imaging system designs a new frequency hopping waveform aiming at a bistatic radar collaborative detection scene, realizes high-efficiency motion compensation, has a coherent processing algorithm of bistatic echo signals, realizes frequency band fusion, and improves the echo signal-to-noise ratio and the distance resolution capability of the radar.
Description
Technical Field
The invention belongs to the technical field of ISAR imaging, and particularly relates to a double-base radar collaborative imaging system based on complementary random waveforms.
Background
Inverse synthetic aperture radar (Inverse Synthetic Aperture Radar, ISAR) radar has all-weather, all-day and long-distance detection capability, is an important sensor for imaging detection of a missile-borne platform target, and plays a role in accurate guidance tasks. However, with the advancement of target stealth technology and the rapid development of interference cancellation technology, such as target radar cross-sectional area (Radar Cross Section, RCS) shrinking requires that the radar employ a large antenna aperture and a large bandwidth signal regime, presenting a significant challenge to Shan Bulei radar detection. Compared with single radar detection, multi-radar cooperative detection can not only obtain more observation times, but also obtain the characteristics of different dimensions of a target frequency domain, a polarization domain, a airspace and the like, and is an important development direction of the detection of a stealth target in a complex electromagnetic environment.
The existing multi-radar cooperative detection technology can be divided into space cooperation and frequency band cooperation according to different detection angles and radar working frequency bands, so that space diversity benefit and frequency diversity benefit are obtained. The method realizes target detection and identification by jointly processing a plurality of detection view angle information, thereby reducing the probability of single view angle detection misjudgment. The latter carries out coherent processing on the frequencies of different radars to obtain higher distance resolution and pulse pressure gain. For the application scene of the missile-borne radar, a plurality of missile-borne radars fly along with the missile-borne radar, the detection visual angle difference is small, and the target detection is generally carried out by adopting a frequency band fusion mode. Because different radars move at high speed and echo data are distributed on a plurality of discontinuous frequency bands, phase errors introduced by platform movement are firstly required to be eliminated, systematic errors among different radar echoes are compensated, effective fusion of data in different frequency bands is realized on the basis, and the processing process involves key technologies such as motion compensation, coherent registration, data fusion and the like. In terms of motion compensation, literature (see Liao Z K, hu J M, lu D W, et al Motion analysis and compensation method for random stepped frequency radar using the Pseudorandom code [ J ]. IEEE Access.2018, 6 (1): 57643-57654) uses adjacent range cross-correlation for velocity estimation, and compensation accuracy is determined by bandwidth and cannot be applied to motion-sensitive radar waveforms such as random frequency hopping. The search of the cost function extremum to determine the target speed is known from the literature (see Li X, li G S, et al Autofocusing of ISAR images based on entropy minimization [ J ]. IEEE Trans.on Aerospace and Electronic systems 1999, 35 (4): 1240-1252), and the algorithm performance is sensitive to the step size and range of the search. The literature (see Liao Z K, lu D W, hu J M, et al Waveform design for random stepped frequency radar to estimate object velocity J Electronics letters, 2018, 54 (14): 894-896) proposes a method of velocity estimation based on complementary code modulation, which achieves a high accuracy estimation of velocity by transmitting adjacent bursts with complementary relations, which has the disadvantage that two bursts are required to complete the velocity estimation, reducing radar data rate. In the coherent registration, literature (see TIAN Biao, CHEN Zengping, and XU Shiyou. Spark sub-band fusion imaging based on parameter estimation of geometrical theory of diffraction model [ J ]. IET Radar Sonar & Navigation, 2014, 8 (4): 318-326) divides the phase to be compensated between sub-bands into two parts of linear phase and fixed phase, and solves by using an all-pole model, the pole order is difficult to determine when the disadvantage is. Literature (see TIAN Jihua, SUN Jiping, WANG Guohua, et al Multiband radar signal coherent fusion processing with IAA and apFFT [ J ]. IEEE Signal Processing Letters, 2013, 20 (5): 463-466) uses a cross-correlation method to solve for linear phase terms, and uses FFT (Fast Fourier Transform) fast Fourier transform to solve for fixed phase terms, avoiding pole order problems. In terms of band data fusion, literature (see BAI Xueru, ZHOU Feng, WANG Qi, et al, spark sub-band imaging of space targets in high-speed motion [ J ]. IEEE Transactions on Geoscience and Remote Sensing, 2013, 51 (7): 4144-4154 and HU Pengjiang, XU Shiyou, WU Wenzhen, et al, spark sub-band ISAR imaging based on autoregressive model and smoothed ℓ 0 algorithm [ J ]. IEEE Sensors Journal, 2018, 18 (22): 9315-9323) fills the defect band into a wideband signal and images it, however, band estimation is performed based on existing band information without adding additional information. The literature (see ZHOU Feng and BAI Xueru, high-resolution sparse sub-band imaging based on Bayesian learning with hierarchical priors [ J ]. IEEE Transactions on Geoscience and Remote Sensing, 2018, 56 (8): 4568-4580) establishes a probability model for sparse frequency band echo signals, performs distance fusion imaging by using a Bayesian learning algorithm after performing azimuth dimension imaging on a target, and avoids errors introduced by a frequency band filling algorithm, however, the azimuth dimension imaging requires accurate target motion compensation, and the compensation accuracy of subband data needs further analysis.
The existing missile-borne ISAR radar system has the following main defects: 1) Performing data level fusion based on target point trace information obtained by each radar, and not considering gain caused by cooperative processing of radar target echo signals; 2) The frequency band fusion algorithm is mainly based on two ideas, one is to fill the defective frequency band by adopting a frequency band extrapolation mode and then image the defective frequency band, and the method is realized based on the existing frequency band information without adding extra information quantity. The other thinking is that a modern spectrum, sparse representation or Bayesian method is adopted to extract scattering center parameters for super-resolution distance imaging, and the original information of radar data is lost in the parameter extraction process, so that two-dimensional imaging is difficult to perform.
Disclosure of Invention
The invention aims to provide a bistatic radar collaborative imaging system based on complementary random waveforms, which designs a new frequency hopping waveform aiming at a bistatic radar collaborative detection scene, realizes efficient motion compensation, has a coherent processing algorithm of bistatic echo signals, realizes frequency band fusion and improves the echo signal-to-noise ratio and the distance resolution capability of a radar.
The specific technical scheme of the invention is a double-base radar collaborative imaging system based on complementary random waveforms, which is characterized by comprising a first radar and a second radar which are respectively arranged on two moving platforms accompanying flight, a radar signal transmitting module, a radar signal receiving module, a distance difference correcting module, a target motion compensating module and a frequency band fusion imaging module which are arranged on a control platform,
the radar signal transmitting module is used for controlling two radars to cooperatively transmit detection signals, and the first radar and the second radar adopt random frequency hopping waveforms, so that the transmitting signal models of the two radars are respectively expressed as the following formulas (I) and (II):
wherein the coherent processing pulse trains all compriseNThe sub-pulses have the same frequency hopping rule, and the pulse repetition period is thatT r Pulse = pulse width ofTRandom modulation frequency distribution over a given bandwidthBIn the method, the minimum frequency hopping step length is deltaf =B /NLet the frequency hopping coefficients of the first radar and the second radar be respectivelyc 1 (n) and c 2 (n) Satisfies the following conditionsc 2 (n)=-c 1 (n)，f 1 Andf 2 carrier frequencies of the first radar and the second radar respectively;
the radar signal receiving module is used for controlling the two radars to receive the reflected signals of the targets, and the first radar is used for transmitting and receiving the radarnThe sub-pulse echoes after mixing can be represented as the following formula (III):
wherein the target comprisesKA scattering center, an initial time, a firstkThe distance between each scattering center and the radar isr 1k The target radial movement speed isvFirst, thenThe distance between the scattering center and the radar one at the time of sub-pulse transmission can be expressed asr 1k (n)=r 1k +vnT r ，σ k Represent the firstkThe intensity of the individual scattering centers is such that,
second step of transmitting and receiving radarnThe sub-pulse echoes after mixing can be expressed as the following formula (V):
wherein ,Δr=r 2k -r 1k First, thekThe distance between each scattering center and the second radar isr 2k ，
Echo received by radar two-transmitting radars 21 (n) Echo received by radar I and radar IIs 12 (n) Represented by the following formulas (VI) and (VII), respectively:
the distance difference correction module is used for eliminating phase modulation items related to distance in the first radar echo and the second radar echo, realizing distance difference correction, and the echoes subjected to distance difference correction can be respectively expressed as the following formulas (IX) and (X):
the target motion compensation module is used for eliminating components related to speed in the radar first echo and the radar second echo, realizing target motion compensation, and the echoes subjected to echo motion compensation can be respectively expressed as the following formulas (XVI) and (XVII):
wherein ,f 0 =(f 1 +f 2 )/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf；
the frequency band fusion imaging module rearranges random frequency hopping echoes of different frequency bands, carries out zero padding processing on echo data on defective frequency points, and enables echo signals of two radars to carry out coherent fusion imaging through FFT (fast Fourier transform) transformation by setting tight constraint conditions.
Furthermore, the motion platform is a missile, and the control platform fighter, early warning machine or naval vessel.
Furthermore, the echo motion compensation of the target motion compensation module is to correlate the carrier frequencies and the frequency hopping coefficients of the first radar and the second radarf 0 =（f 1 +f 2 ）/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf，c 2 (n)=-c 1 (n) Substitution into formula (IX) and formula (X) can be achieved:
the echo components are multiplied to obtain the following result:
the post-FFT sequence peak position target velocity is given by:
wherein k 0 After obtaining the target velocity for the peak position, the velocity component-related component in the echo is eliminated, and echo motion compensation is performed on the formulas (XI) and (XII).
Furthermore, the specific method for performing band fusion imaging by the band fusion imaging module is to arrange the echo sequences of the formulas (XVI) and (XVII) from small to large according to the minimum frequency hopping step length, and the obtained echo sequence is expressed as:
wherein ,L=M+2Nfor the length of the echo sequence after zero padding,s all (n) Front of (2)NThe individual components ares 21 (n) As a result of rearrangement, postNThe individual components ares 11 (n) The result of rearrangement is effective observation, and the defect frequency band is [ [f 1 ，f 2 ]Defective bandwidthf 1 -f 2 For the frequency hopping step deltafIs an integer multiple of the corresponding zero-padding frequency point numberM=(f 1 -f 2 )/ Δf-1, pair ofs all (n) The high resolution range profile obtained by performing the FFT can be expressed as:
the complementary random waveform-based double-base radar collaborative imaging system provided by the invention has the beneficial effects that 1) the complementary random frequency hopping waveform is adopted to detect a target, and the complementary random frequency hopping waveform-based double-base radar collaborative imaging system consists of two moving platforms (missiles) accompanied with flight and processing modules respectively deployed on a control platform, so that phase items introduced by the distance difference of the platforms can be effectively eliminated; 2) The fused range profile provides richer target detail information, and the estimated speed precision can meet the focusing requirement of high-resolution range imaging; 3) The resolution is improved by adopting a fusion imaging mode, the distribution area of the target scattering center is larger, the provided target detail information is richer, an ISAR imaging result under ideal speed compensation is given, and the focusing performance of the image is measured by contrast. Actual use results show that the method can effectively realize double-base motion compensation and fusion detection of targets.
The complementary random waveform-based bistatic radar collaborative imaging system realizes the frequency band fusion in the bistatic radar collaborative imaging process, and improves the echo signal-to-noise ratio and the distance resolution capability of the radar.
Drawings
FIG. 1 is a schematic diagram of the composition of a complementary random waveform based dual-based radar collaborative imaging system of the present invention;
FIG. 2 is a schematic diagram of bistatic radar co-detection for a bistatic radar co-imaging system based on complementary random waveforms according to the present invention;
FIG. 3 is a schematic diagram of a bistatic radar random frequency hopping complementary modulation of the bistatic radar collaborative imaging system based on complementary random waveforms of the present invention;
FIG. 4 is a schematic diagram of random frequency hopping echo rearrangement zero padding of the complementary random waveform based dual-base radar collaborative imaging system of the present invention;
FIG. 5 is a schematic diagram of an established target point scattering model;
FIG. 6 is a schematic diagram of a dual-basis co-detection geometry employing a dual-basis radar co-imaging system based on complementary random waveforms of the present invention;
FIG. 7 (a) is a graph of phase estimation results introduced by distance differences employing a fused distance imaging effect comparison of the system of the present invention;
FIG. 7 (b) is a graph of the target velocity estimation results of the fusion distance imaging effect comparison using the system of the present inventionv tLOS =3m/s）；
FIG. 7 (c) is a graph of radar-1 range high resolution imaging results using the fused range imaging effect comparison of the system of the present invention;
FIG. 7 (d) is a graph of radar two 2 range high resolution imaging results using a fused range imaging effect comparison of the system of the present invention;
FIG. 7 (e) is a graph of the actual fusion probe distance high resolution imaging results of a fusion distance imaging effect comparison employing the system of the present invention;
FIG. 7 (f) is a graph of the results of ideal fusion detection distance high resolution imaging using the fusion distance imaging effect comparison of the system of the present invention;
FIG. 8 (a) is a diagram of radar-1-ISAR high-resolution imaging results compared with radar imaging results using the system of the present invention;
FIG. 8 (b) is a graph of radar two 2-ISAR high resolution imaging results compared with radar imaging results using the system of the present invention;
FIG. 8 (c) is a graph of actual fusion ISAR imaging results compared with radar imaging results using the system of the present invention;
FIG. 8 (d) is a graph of ideal fusion ISAR imaging results compared with radar imaging results using the system of the present invention.
Description of the embodiments
The technical scheme of the invention is further described below with reference to the attached drawings.
As shown in fig. 1, the dual-base radar collaborative imaging system based on complementary random waveforms of the present invention is a block diagram. The principle of the cooperative detection of the double-base radar is shown in figure 2, a 2-transmission and 2-reception cooperative detection system is adopted, and the separated echo set is recorded as {s 11 (t)，s 12 (t)，s 21 (t)，s 22 (t)}. wherein s pq Representation radarp(p=1, 2) transmit pulse, radarq(q=1, 2) echo representation in receive mode.
Firstly, two radar echo signals meeting the tight constraint condition of complementary characteristics are designed, a double-base random frequency hopping signal waveform pair with complementary characteristics is provided, and random frequency hopping signals with equal frequency hopping coefficients and opposite directions are simultaneously transmitted by the two radars. After the target echo is obtained, different band-pass filters are set according to the carrier frequency difference, and a separated target echo sequence is obtained. After the echo components of the 4 paths are obtained, the modulation phase items introduced by the distance delay differences under different paths are calculated and used for compensating additional phases introduced by the distance delay differences under different paths, so that the distance difference correction of the different paths is completed, and the 4-path echo signals with the same distance delay are obtained. On the basis, effective estimation of the target speed can be realized through simple multiplication processing and FFT conversion. And compensating the target echo based on the estimated speed to obtain random frequency hopping echo sequences of different frequency bands. And then realizing high-resolution distance imaging of random frequency hopping echoes of different frequency bands by adopting a rearrangement zero filling mode. Finally, combining the envelope alignment and initial phase correction methods in the ISAR imaging flow to finish the high-resolution two-dimensional imaging of the double-base collaborative detection.
The double-base radar collaborative imaging system is suitable for band fusion imaging of a double-missile motion platform along with a flight mode, and comprises the following steps: a first radar 1 and a second radar 2 respectively installed on two missiles, and a radar signal transmitting module 10, a radar signal receiving module 20, a distance difference correcting module 30, a target motion compensating module 40 and a frequency band fusion imaging module 50 which are deployed on a control platform. The control platform can be a fighter plane, an early warning plane or a naval vessel.
The radar signal transmitting module 10 is used for controlling the two radars to cooperatively transmit detection signals;
wherein, the radar signal receiving module 20 is used for performing down-conversion and band-pass filter separation on the radar echo signal;
the distance difference correction module 30 is configured to eliminate a phase modulation term related to a distance in the first radar 1 and the second radar 2 echoes, so as to implement distance difference correction;
the target motion compensation module 40 is used for eliminating components related to the speed in the first radar 1 and the second radar 2 echoes to realize target motion compensation;
the band fusion imaging module 50 rearranges random frequency hopping echoes of different frequency bands, performs zero padding processing on echo data on defective frequency points, and enables echo signals of two radars to perform coherent fusion imaging through FFT (fast Fourier transform) by setting tight constraint conditions.
The radar signal transmitting module 10 is used for controlling the radar one 1 and the radar two 2 to cooperatively transmit detection signals.
The radar I1 and the radar II 2 adopt random frequency hopping waveforms, and the coherent processing pulse trains compriseNThe sub-pulses have the same frequency hopping rule, and the pulse repetition period is thatT r Pulse width ofT. Random modulation frequency distribution over a given bandwidthBIn the method, the minimum frequency hopping step length is deltaf=B /NThe frequency hopping coefficient is the interval 0,N-1]one length of (a)NTo ensure full utilization of the frequency band, the frequency hopping coefficients typically traverse intervals and are not repeated. Let the frequency hopping coefficients of the first radar 1 and the second radar 2 be respectivelyc 1 (n) and c 2 (n) The transmitted signal models of the two radars are respectively expressed as follows:
wherein ,f 1 andf 2 carrier frequencies of radar one 1 and radar two 2, respectively.
The random frequency hopping modulation rule of the two radars is shown in figure 3, whereinf 0 =(f 1 +f 2 )/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf，c 2 (n)=-c 1 (n) As can be seen from the figure, the random frequency hopping signals transmitted by the two radars have the complementary frequency change rule, namely the frequency hopping coefficient of 1-transmission pulse of the radarc 1 (n) Frequency hopping coefficient with radar two 2 transmit pulsec 2 (n) Equal in size and opposite in direction.
The radar signal receiving module 20 is configured to control processing of the reflected signals of the radar one 1 and radar two 2 receiving targets, including down-conversion and band-pass filter separation of the received signals.
Taking the cooperative detection of double radars as an example, in order to separate out the signal components of different radars, carrier frequencies of two radarsf 1 Andf 2 the difference of (2) needs to be larger than the modulation bandwidth of the radar signal and then is achieved by a corresponding band-pass filter. The target comprisesKA scattering center, an initial time, a firstkThe distance between each scattering center and the radar 1 isr 1k . The target radial movement speed isvFirst, thenThe distance between the scattering center and radar-1 at the time of sub-pulse transmission can be expressed asr 1k (n)=r 1k +vnT r . First, 1 st, when 1 st is transmitted and 1 st is receivednThe sub-pulse echoes after mixing can be expressed as:
wherein KFor the number of scattering centers contained by the target,σ k represent the firstkThe intensity of the individual scattering centers. For a scene of collaborative detection of multiple missile-borne radars, an accompanying flight mode is generally adopted, the difference of radar detection visual angles is small, and the intensity of any scattering center on a target is basically consistent with that of two radars with opposite speeds. Setting the initial time, the firstkThe distance between each scattering center and the radar II 2 isr 2k The second radar 2 transmits the second radar 2 to receivenThe sub-pulse echoes after mixing can be expressed as:
let deltar=r 2k -r 1k The electromagnetic wave transmission time corresponding to the difference between the two radar distances is represented, and the above description can be rewritten as:
by the same token, the echo received by the radar I1 is transmitted by the radar II 2s 21 (n) Echo received by radar I1 and radar II 2s 12 (n) Expressed as:
the range difference correction module 30 is configured to eliminate phase modulation terms introduced by different range delays of echo signals received by different radars.
Comparing the formula (III) with the formula (VII) shows that the same radar transmits, the echo signals received by different radars have phase modulation items introduced by different distance delays, the phase difference of the two echoes is processed, and the phase modulation items are eliminated, so that the distance difference correction is realized.s 12 (n) Can be made bys 11 (n) The representation is:
wherein φ(n)=2πΔr(f 1 +c 1 (n)Δf)/c，φ(n)Can be obtained by calculation of echo signals received by radar and used fors 12 (n) Is provided with a correction of the distance difference of (a),s 22 (n) and s 21 (n) Similar to the compensation process of (c), the echo after the distance difference correction can be expressed as:
it can be seen that after the radar distance difference is corrected, echoes emitted by different radars have the same change rule, so that the following echo-based methods 11 (n) and s 21 (n) And performing cooperative detection.
The target motion compensation module 40 is used to cancel velocity-dependent components of the echo.
As can be seen from the echo model, the coupling term exists between the frequency variation and the distance variation of the random frequency hopping waveform, which leads to the introduction of a phase high-order term in the echo, and the high-resolution range profile obtained by direct FFT has serious defocusing, so that the target motion needs to be compensated. As can be seen by comparing formula (IX) with formula (X),s 11 (n) and s 21 (n) The method has the advantages that the method has the same distance time delay and different signal frequencies, and if the random frequency hopping modes of the two radars are reasonably designed, the influence of frequency modulation can be eliminated, so that the rapid estimation of the target motion parameters is realized.
Will bef 0 =(f 1 +f 2 )/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf，c 2 (n)=-c 1 (n) Substitution formula (IX) and formula (X) can be obtained:
the echo components are multiplied to obtain the following result:
in the formula ,
is free of andnthe relevant variable is therefore constant.
Contains variablec(n)，s’(n) Number of follower pulsesnAnd (3) a change. Thus (2)s(n) From a single frequency signal componentS 0 And a variation components’(n) Composition is prepared. After FFT conversion, the energy of the single frequency signal components are added together to form a peak values’(n) Still in a defocused state, so the target speed of the peak position of the sequence after FFT conversion can be expressed as follows: />
wherein k 0 Is the peak position. After the target velocity is obtained, the velocity component-related component in the echo is eliminated, and the echo motion compensation can be performed on the formulas (XI) and (XII). The compensated echo can be expressed as:
it can be seen that the formulas (XVI) and (XVII) describe the detection results of the target randomly hopping signals in different frequency bands. And carrying out high-resolution imaging on the coherent fusion of random frequency hopping echoes of different frequency bands.
The band fusion imaging module 50 is used for performing coherent fusion imaging based on echo data of the defect frequency points. And rearranging random frequency hopping of different frequency bands, carrying out zero padding treatment on echo data on the defective frequency points, and enabling echo signals of the two radars to carry out coherent fusion imaging through FFT (fast Fourier transform) transformation by setting a tight constraint condition. The defect bandwidth is integer times of the frequency hopping step length, namely the tight constraint. The rearrangement zero-filling process is shown in fig. 4, the echo sequences of the formula (XVI) and the formula (XVII) are arranged from small to large according to the minimum frequency hopping step length, and the obtained echo sequence is expressed as:
wherein L=M+2NFor the length of the echo sequence after zero padding,s all (n) Front of (2)NThe individual components ares 21 (n) As a result of rearrangement, postNThe individual components ares 11 (n) The result of rearrangement is effective observation, and the defect frequency band is [ [f 1 ，f 2 ]In order to ensure the relativity of two radar frequency hopping signals, a tight constraint condition is set: defective bandwidthf 1 -f 2 For the frequency hopping step deltafIs an integer multiple of the corresponding zero-padding frequency point numberM=(f 1 -f 2 )/ Δf-1。
It can be seen that the light source is,s all (n) The defective frequency band with the zero-filling position in the middle can be obtaineds all (n) Distance resolution and continuous bandwidth of 2BIs consistent in echo sequence performance. The specific deduction process is as follows:
is provided withs Δ (n) Is of the frequency band [f 1 -B，f 2 +B]Sampling step length is deltafIs used for the efficient observation of the sequence of (a),s H (n) Is of the frequency band [f 1 -B，f 1 +B]Sampling step length is deltafWhereinn=0,1,...,L-1. Then
s H (n)=h 1 (n)s Δ (n)
s all (n)=h 2 (n)s Δ (n)
wherein 
，
As a window function. The corresponding FFT results are respectively: />
s H (n) and s all (n) The FFT imaging results of (a) are respectively:
wherein ,
a circular convolution is represented and is shown,S Δ (k) Representing full-band effective observation sequencess Δ (n) Is a result of FFT imaging. Rectangular window function FFT transform result is sinc envelope with same shapeH 1 (k) and H 2 (k). Thus, the broadening modulation performance of the range profile peak after the cyclic convolution is consistent.
For a pair ofs all (n) The high resolution range profile obtained by performing the FFT can be expressed as:
therefore, a high-resolution distance imaging result under double-base cooperative detection can be obtained, and a two-dimensional high-resolution distance image of the target can be obtained by further combining an envelope alignment and initial phase correction algorithm.
The effect of the invention can be further illustrated by the following simulation results:
the simulated target ship point scattering model is shown in figure 5, and consists of 367 scattering points, wherein the ship length is as followsl=120m, widthb=30m. Radar-1 transmitting signal carrier frequencyf 1 =15 GHz, radar two 2 transmit signal carrier frequency asf 2 = 15.255GHz, the signal bandwidths are allB=128 MHz, minimum frequency hopping step deltaf=1MHz。
1-signal modulation rule of radarc 1 (n) For the interval of time [0 ],N-1]one length of (a)NIs not repeated by the pseudo-random integer sequence. Modulation rule of radar two 2 signalsc 2 (n)=-c 1 (n)。
The geometric scene of the double-base collaborative detection is shown in figure 6, the ship is positioned at the origin of the coordinate system OXYZ, and the double-detection platform is positioned at the heightHPositive flight along Y-axis =1.73 km, and with the same flight speedv r 225m/s, the distance between the first 1 radar and the center of the ship at the initial moment is 10km, the distance between the second 2 radar and the center of the ship is 10.017km, the target is in a maneuvering state, and the projection component of the moving speed on the radar line of sight isv tLOS =3m/s. The azimuth angle θ and the pitch angle β of the radar line of sight in the target coordinate system at the initial time are θ=80 degrees and β=10 degrees, respectively. The complementary random frequency hopping waveform of the system is adopted to detect the target, and the target echo sequence separated by the band-pass filter is expressed as {s 11 (t)，s 12 (t)，s 21 (t)，s 22 (t)}。
The phase introduced by calculating the radar range difference is shown in fig. 7 (a), and the theoretical calculation result of the phase is also shown in the figure. Therefore, the system can effectively eliminate the phase term introduced by the platform distance difference. Fig. 7 (b) shows the result of target speed estimation by FFT conversion, and the target speed obtained from the peak position estimation is 3.099m/s. Fig. 7 (c) and fig. 7 (d) show the distance imaging results of the two radars respectively, and due to the limited bandwidth, the scattering center is distributed in a small number of distance units, so that less target detail information can be obtained. The fused high-resolution range profile is shown in fig. 7 (e), and the ideal compensated high-resolution range profile of the target speed is also provided, so that the fused range profile provides more abundant target detail information, and the estimated speed precision can meet the focusing requirement of high-resolution range imaging.
The two-dimensional imaging results of the radar obtained by performing envelope alignment and initial phase correction by using an envelope cross-correlation method and a phase gradient self-focusing (Phase Gradient Autofocus, PGA) method are shown in fig. 8 (a) -8 (d), wherein the independent imaging results of the radar I1 and the radar II 2 are respectively shown in fig. 8 (a) and 8 (b), and due to the limitation of distance resolution, the target is distributed in about 15 distance units in the distance direction, the scattering center distribution is relatively fuzzy, and the target contour is unclear. The result obtained by using the fusion imaging mode is shown in fig. 8 (c), because of the improvement of resolution, the distribution area of the target scattering center is larger, and occupies about 50 distance units, the provided target detail information is more abundant, and the ISAR imaging result under ideal speed compensation is given, and the focusing performance of the image is measured by contrast (see m. martorella, b. haywood, f. berizi, and e. dale, performance Analysis of an ISAR Contrast-Based Autofocusing Algorithm Using Real Data [ J ], IEEE Radar reference, pp.30-35, 2003), wherein the contrast of the real fused ISAR image is 16.38, and the contrast of the ideal compensated ISAR image is 17.26. Experimental results show that the system can effectively realize double-base motion compensation and fusion detection of targets.
While the invention has been disclosed in terms of preferred embodiments, the embodiments are not intended to limit the invention. Any equivalent changes or modifications can be made without departing from the spirit and scope of the present invention, and are intended to be within the scope of the present invention. The scope of the invention should therefore be determined by the following claims.
Claims (4)
1. A double-base radar collaborative imaging system based on complementary random waveforms is characterized by comprising a first radar (1) and a second radar (2) which are respectively installed on two moving platforms accompanying flight, a radar signal transmitting module (10), a radar signal receiving module (20), a distance difference correcting module (30), a target motion compensating module (40) and a frequency band fusion imaging module (50) which are deployed on a control platform,
the radar signal transmitting module (10) is used for controlling two radars to cooperatively transmit detection signals, wherein a first radar (1) and a second radar (2) both adopt random frequency hopping waveforms, and the transmission signal models of the two radars are respectively represented by the following formulas (I) and (II):
wherein the coherent processing pulse trains all compriseNThe sub-pulses have the same frequency hopping rule, and the pulse repetition period is thatT r Pulse width ofTRandom modulation frequency distribution over a given bandwidthBIn the method, the minimum frequency hopping step length is deltaf =B / NLet the frequency hopping coefficients of the first radar (1) and the second radar (2) be respectivelyc 1 (n) and c 2 (n) Satisfies the following conditionsc 2 (n)=-c 1 (n)，f 1 Andf 2 carrier frequencies of radar one (1) and radar two (2) respectively;
the radar signal receiving module (20) is used for controlling the reflected signals of two radar receiving targets, and when the radar I (1) transmits the radar I (1) to receive, the firstnThe sub-pulse echoes after mixing can be represented as the following formula (III):
wherein the target comprisesKA scattering center, an initial time, a firstkThe distance between each scattering center and the radar one (1) isr 1k The target radial movement speed isvFirst, thenThe distance between the scattering center and radar one (1) at the time of sub-pulse transmission can be expressed asr 1k (n)=r 1k +vnT r ，σ k Represent the firstkThe intensity of the individual scattering centers is such that,
the second radar (2) transmits and receives the second radar (2)nThe sub-pulse echoes after mixing can be expressed as the following formula (V):
wherein ,Δr=r 2k -r 1k First, thekThe distance between the scattering centers and the radar II (2) isr 2k ，
Radar two (2) transmitting echoes received by radar one (1)s 21 (n) Echo received by radar one (1) and radar two (2)s 12 (n) Represented by the following formulas (VI) and (VII), respectively:
the distance difference correction module (30) is configured to eliminate a distance-related phase modulation term in the first radar (1) and the second radar (2) echoes, implement distance difference correction, and the echoes after the distance difference correction can be represented by the following formulas (IX) and (X):
the target motion compensation module (40) is used for eliminating the components related to the speed in the echoes of the radar I (1) and the radar II (2) to realize target motion compensation, the echoes after target motion compensation can be respectively expressed as the following formulas (XVI) and (XVII),
wherein ,f 0 =(f 1 +f 2 )/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf；
the frequency band fusion imaging module (50) rearranges random frequency hopping echoes of different frequency bands, carries out zero padding treatment on echo data on defective frequency points, and enables echo signals of two radars to carry out coherent fusion imaging through FFT (fast Fourier transform) transformation by setting tight constraint conditions.
2. The complementary random waveform based bistatic radar collaborative imaging system according to claim 1, wherein the motion platform is a missile and the control platform is a fighter plane, an early warning plane or a naval vessel.
3. A complementary random waveform based bistatic radar collaborative imaging system according to claim 1 wherein the echo motion compensation of the target motion compensation module (40) is based on the correlation of the carrier frequencies and frequency hopping coefficients of radar one (1) and radar two (2)Is tied up withf 0 =（f 1 +f 2 ）/2 ，c(n)=c 1 (n)+(f 1 -f 2 )/2Δf，c 2 (n)=-c 1 (n) Substitution into formula (IX) and formula (X) can be achieved:
the echo components are multiplied to obtain the following result:
the post-FFT sequence peak position target velocity is given by:
wherein k 0 After obtaining the target velocity for the peak position, the velocity component-related component in the echo is eliminated, and echo motion compensation is performed on the formulas (XI) and (XII).
4. The complementary random waveform based bistatic radar collaborative imaging system according to claim 1, wherein the specific method for performing band fusion imaging by the band fusion imaging module (50) is to arrange echo sequences of formulas (XVI) and (XVII) from small to large according to minimum frequency hopping step length, and the obtained echo sequences are expressed as:
wherein ,L=M+2Nfor the length of the echo sequence after zero padding,s all (n) Front of (2)NThe individual components ares 21 (n) As a result of rearrangement, postNThe individual components ares 11 (n) The result of rearrangement is effective observation, and the defect frequency band is [ [f 1 ，f 2 ]Defective bandwidthf 1 -f 2 For the frequency hopping step deltafIs an integer multiple of the corresponding zero-padding frequency point numberM=(f 1 -f 2 )/ Δf-1, pair ofs all (n) The high resolution range profile obtained by performing the FFT can be expressed as:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310108808.0A CN115856883B (en) | 2023-02-14 | 2023-02-14 | Bistatic radar collaborative imaging system based on complementary random waveforms |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310108808.0A CN115856883B (en) | 2023-02-14 | 2023-02-14 | Bistatic radar collaborative imaging system based on complementary random waveforms |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN115856883A CN115856883A (en) | 2023-03-28 |
| CN115856883B true CN115856883B (en) | 2023-05-16 |
Family
ID=85658020
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310108808.0A Active CN115856883B (en) | 2023-02-14 | 2023-02-14 | Bistatic radar collaborative imaging system based on complementary random waveforms |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115856883B (en) |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103630878B (en) * | 2013-01-31 | 2015-08-12 | 中国科学院电子学研究所 | A kind of frequency band fusion method based on iteration self-adapting method and device |
| CN107526074B (en) * | 2017-07-19 | 2020-12-22 | 上海无线电设备研究所 | Distance and speed two-dimensional high-resolution processing method for sparse frequency hopping signal |
| US11789142B2 (en) * | 2020-06-11 | 2023-10-17 | Mitsubishi Electric Research Laboratories Inc. | Graph-based array signal denoising for perturbed synthetic aperture radar |
| CN114325633B (en) * | 2022-03-16 | 2022-06-17 | 西安电子科技大学 | Coherent processing method and processing device for dual-band radar |
| CN114910906B (en) * | 2022-04-29 | 2024-10-01 | 中国人民解放军陆军工程大学 | A bistatic ISAR sparse aperture maneuvering target imaging method and system |
| CN115657018A (en) * | 2022-09-08 | 2023-01-31 | 湖南雷像电子科技有限公司 | Method, device, equipment and medium for improving random frequency hopping radar imaging |
-
2023
- 2023-02-14 CN CN202310108808.0A patent/CN115856883B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN115856883A (en) | 2023-03-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN101526614B (en) | SAR echo rapid simulation method based on sub-aperture and equivalent scatterer | |
| Wu et al. | Translational motion compensation in ISAR image processing | |
| CN104898119B (en) | A kind of moving target parameter estimation method based on correlation function | |
| CN106405552B (en) | SAR radar target focus method based on WVD-PGA algorithm | |
| CN107085213A (en) | The moving target ISAR imaging methods designed based on random Based on Modulated Step Frequency Waveform | |
| CN102608597A (en) | Method for imaging actual aperture foresight on basis of incomplete data deconvolution | |
| CN113238225B (en) | Radar for moving target detection | |
| CN107942327A (en) | Single channel HRWS SAR imaging methods based on impulse phase coding | |
| CN105487074A (en) | Bistatic synthetic aperture radar numerical range Doppler imaging method | |
| CN109031299A (en) | ISAR translational compensation method under Low SNR based on phase difference | |
| Baczyk et al. | 3-D high-resolution isar imaging for noncooperative air targets | |
| CN115877381A (en) | Bistatic radar collaborative imaging method based on complementary random waveform | |
| CN115856883B (en) | Bistatic radar collaborative imaging system based on complementary random waveforms | |
| CN112946650A (en) | One-station fixed double-station low-frequency ultra-wideband SAR moving target detection and imaging method | |
| Kapai et al. | SAR Focusing of Mobile ApRES Surveys | |
| Ji et al. | A fast false large-scene images generation method against SAR based on two-dimension CZT and multi-transmitter cooperation | |
| CN116359921A (en) | Fast Time-Domain Imaging Method Based on Accelerated Trajectory Bistatic Forward-Looking Synthetic Aperture Radar | |
| CN108710117A (en) | A kind of synthetic aperture radar clutter cancellation method | |
| Feng et al. | Inverse synthetic aperture radar imaging of maneuvering targets based on joint time-frequency analysis | |
| Azouz et al. | New SAR Algorithm for Sidelobe Reduction in Range direction | |
| Братченко et al. | Method for ISAR imaging objects with 3D rotational motion | |
| Li et al. | Low-Flying Moving Target Detection and Imaging Algorithm of Spaceborne SAR Based on Two-Dimensional Velocity Search | |
| Jiang et al. | Design and Experimental Verification of ISAR imaging System for Airborne Maritime Surveillance Radar | |
| CN115436939B (en) | A multi-level resolution fast imaging method for multi-channel high-resolution wide-swath SAR | |
| Zhao et al. | Single-Channel SAR Moving Target Detection Method Based on RPCA |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |