CN109459752B - Resource self-adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging - Google Patents
Resource self-adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging Download PDFInfo
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Abstract
The invention discloses a resource self-adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging, which relates to the technical field of phased array radar inverse synthetic aperture radar imaging, and solves the technical problem of how to reasonably allocate resources of a multi-target imaging task in a single radar from the aspects of target azimuth and distance direction so as to improve the overall performance of a system. The invention can realize the resource allocation of the single-step radar facing to multiple targets from the aspects of the azimuth direction and the distance direction of the targets, save radar resources and improve the overall performance of the system.
Description
Technical Field
The invention relates to the technical field of phased array radar inverse synthetic aperture radar imaging, in particular to a resource self-adaptive scheduling method for two-dimensional sparse imaging of a synthetic aperture radar.
Background
Due to the beam agility and the beam self-adaption capability of the array antenna of the multifunctional phased array radar, the multifunctional phased array radar can execute a task of alternately observing a plurality of targets, and how to distribute the task under the resource constraint has a decisive influence on the radar performance. In the prior art, most researches on a phased array radar resource optimization scheduling strategy only consider how to realize optimization of multi-target searching and tracking performance under the condition of limited time, frequency spectrum, space, power and other resources, and the influence of imaging requirements on the scheduling strategy is rarely considered. Therefore, in the phased array radar resource optimization scheduling, if observation imaging of a plurality of targets can be realized in limited resources, the radar resources can be saved, and the overall performance of a radar system is greatly improved.
Under the random sparse observation imaging mode, the traditional inverse synthetic aperture radar imaging method cannot be used. In recent years, the Compressive Sensing (CS) theory, proposed by d.donoho, e.cand, and chef.tao et al, provides a new technical route for random sparse observation inverse synthetic aperture radar imaging. Researchers at home and abroad carry out more researches on the radar imaging technology based on the CS, a series of sparse aperture inverse synthetic aperture radar imaging methods based on the CS are provided, and effective technical support is provided for bringing imaging task requirements into a resource optimization scheduling model.
For example, chenyijun et al introduces the cognitive imaging idea into radar resource adaptive scheduling, proposes a radar resource adaptive scheduling algorithm based on sparse aperture cognitive inverse synthetic aperture radar imaging, and provides specific performance evaluation indexes, and the algorithm is mainly a method for allocating time resources of one-dimensional sparse inverse synthetic aperture radar imaging based on chirp signals. Mengdi et al propose an imaging radar resource scheduling algorithm based on pulse interleaving and a resource scheduling algorithm for digital array radar search, tracking and imaging tasks, and an optimized scheduling algorithm for Digital Array Radar (DAR) tasks, for the scheduling problem of multi-functional phased array radar imaging tasks.
The prior arts do not have the problem of reasonable resource allocation in a single radar by considering multi-target imaging tasks from the aspects of target azimuth and distance direction, so that the radar resource utilization is insufficient, and the overall performance of the system is deficient.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problem solved by the invention is how to reasonably allocate resources of a multi-target imaging task in a single radar from the perspective of the target direction and the distance direction so as to improve the overall performance of the system.
In order to solve the technical problems, the technical scheme adopted by the invention is a resource self-adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging, on the basis that radar performs feature cognition on each target, the pulse resource demand of each target is calculated, the sub-pulse transmitting position required to be allocated to each target is further determined according to the constraint condition selected by the radar, and echoes are obtained through alternate observation of the targets, so that the inverse synthetic aperture imaging task of a plurality of targets is completed, and the method comprises the following steps:
the radar transmits a small amount of pulses to each target and estimates the flight parameters of the target, and the specific process is as follows:
the waveform parameters for estimating the target parameters of a small number of pulses transmitted by each target are set as follows: carrier frequency frcPulse width T of sub-pulserpFrequency step length Δ frSub-pulse repetition frequency FPRFBandwidth Br. After the radar echo signal is obtained, the distance of the jth target from the radar can be measured by a radar conventional algorithmTarget speedTarget courseTarget height
(II) estimating the two-dimensional size of the target, wherein the specific process is as follows:
for radar echo signals, an inverse synthetic aperture radar imaging method in the prior art is adopted to obtain a j-th target coarse resolution inverse synthetic aperture radar image Srj(k, l) normalizing the inverse synthetic aperture radar image using the following equation:
wherein k and l respectively represent the position of the target distance direction and the position direction envelope, and a proper threshold T is setsCalculating distance to envelope position minimumAnd maximum distance to envelope positionAccording to the relation between the target distance and the envelope position, the distance dimension of the jth target can be obtainedWhere ρ isrr=c/(2Br) Is the distance resolution; the minimum and maximum values of the position envelope position in the azimuth direction are calculated by the same method respectivelyThe azimuth dimension of the jth target can be obtainedWhereinIs the azimuth resolution.
(III) determining the number of target transmission pulse trains and the number of sub-pulse transmissions under the pulse trains by the radar, and the specific process is as follows:
setting a target distance to a reference dimensionReference dimension of azimuthAnd the distance-to-reference resolution ρ required for imagingrefrAzimuthal reference resolution ρrefaThen imaging of jth targetDirection-distance resolution ρjrAnd azimuthal resolution ρjaComprises the following steps:
whereinIs the jth target range dimension,Is the jth target azimuth dimension. Setting the minimum value of the azimuth resolution as rhomina. The maximum frequency step length Δ f required to allow the radar to show the size profile of all targets without ambiguity at alljComprises the following steps:
where c is the speed of light, the number of transmitted minimum sub-pulses N in the pulse train of the jth targetjComprises the following steps:
in order to meet the requirement of the required azimuth resolution for imaging the jth target, the number M of the required transmission pulse trainsjComprises the following steps:
wherein u is1A constant greater than 1 for adjusting the number of transmit bursts, λ being the signal wavelength, FPRFThe sub-pulse repetition frequency.
And (IV) estimating the target azimuth sparsity and the distance sparsity, wherein the specific process is as follows:
coarse resolution inverse synthetic aperture for jth targetRadial radar image SrjThe row with the largest element sum value in (k, l) was normalized to S 'as follows'rj(l) The element sum maximum column is normalized as S ″, as followsrj(k):
Setting a suitable threshold value to TMIs prepared from S'rj(l) Discretized representation is vector S'rjWill be S ″)rj(k) The discretization is represented as vector S ″rjThen the azimuth sparsity of the jth targetAnd distance to sparsityComprises the following steps:
(V) determining the number L of target azimuth sparse transmission pulse trains by the radarjNumber Z of sub-pulses emitted to sparse by sum distancejThe specific process is as follows:
according to the compressed sensing theory, the number of pulse trains and the number of sub-pulses which are sparsely transmitted in the azimuth direction and the distance direction required by the jth target are respectively as follows:
wherein c is1Is a constant related to the recovery accuracy, and usually takes a value between 0.5 and 2.
And (VI) calculating the threat degree of the target by the following specific process:
calculation of the threat degree mainly considers the distance of the targetSpeed of rotationCourse of courseHeightFour parameters, assuming that the radar needs to be on NtotallImaging an object, NtotallThese four factors affecting the threat for each target are written in the form of a matrix:
A=(aij)4×Ntotall (10)
in the formula, aij(i=1,2…,4;j=1,2…,Ntotall) A threat coefficient representing an ith factor of a jth target, i ═ 1,2 …,4 represent the distance of the target from the radar, the speed of the target, the heading of the target, and the altitude of the target, respectively, and j ═ 1,2 …, Ntotall;
Normalizing each factor to Y according to formula (11)ijThe weight of each factor is calculated as beta by the equation (12)i:
Calculating the threat degree of the jth target according to the following formula:
wherein beta is1、β2、β3、β4And respectively obtaining weight coefficients for the distance from the target to the radar, the speed of the target, the course of the target and the height of the target.
(VII) under the condition of meeting the resource constraint, establishing a resource scheduling model and carrying out resource allocation, wherein the concrete process is as follows:
suppose the scheduling interval is T and the sub-pulse repetition frequency is FPRFThen the total number of sub-pulses within the scheduling interval: ptotall=T×FPRF;
Based on the basis, the following performance indexes are defined for the radar imaging resource scheduling algorithm:
(1) the sum of the target threat degrees of the radar completing the imaging task is as follows:
wherein N issRepresenting a target sequence number sequence for completing the imaging task in a scheduling interval T, wherein Nu is the number of targets for completing the imaging task in the scheduling interval;
(2) the scheduling success rate is as follows: the ratio of the number of targets actually and successfully executing the imaging tasks to the number of targets applying for executing the imaging tasks in the scheduling interval T is as follows:
wherein N istotallThe total number of targets for applying for executing the imaging tasks in the scheduling interval;
(3) the utilization rate of pulse resources is as follows: in the scheduling interval T, the ratio of the number of the sub-pulses occupied by the imaging task to the total number of the sub-pulses in the scheduling interval is completed:
(4) sum of performance indexes:
SPI=w1.STC+w2.SSR+w3.PRU (17)
wherein w1、w2、w3A weight coefficient.
Based on the performance indexes, a resource scheduling model is established as follows:
any pulse train of I'jiThe sum of the number of the sub-pulses in the pulse train is less than or equal to Nj
The resource scheduling model according to equation (18) can be described as:
step 1: setting the initial time j as 1, using the most front sub-pulse in the current rest idle pulse as the start position start for observing the j th target emission sub-pulsej;
Step 2: according to the number M of the sub-pulses required during the full-aperture observationj×NjDetermining the position of a terminator pulse of the task;
step 3: from the starting position to the end position by NjFor spacing, uniformly dividing MjA pulse train;
step 4: randomly picking out L from the currentjEach pulse train being randomly inserted Z within each selected pulse trainjAnd observing the sub-pulses.
Step 5: if j < NtotallAnd j equals j +1 and returns to the first step.
Step 6: obtaining a target sequence number sequence N for completing the imaging task within the scheduling interval T under the priority ordering modesThe number Nu of targets for completing the imaging task;
step 7: and calculating the sum of target threat degrees, scheduling success rate, pulse resource utilization rate and performance indexes of the radar for completing the imaging task in the priority sorting mode.
Adding the above-mentioned NtotallAnd (3) according to the principle that each combination in the priority sorting mode is substituted into the model to perform resource allocation according to the target priority, calculating the SPI of each combination through the allocation processes from Step1 to Step7, and selecting a pulse resource allocation sequence with the maximum Sum of Performance Indexes (SPI) and meeting the conditions of 3 constraints in the model as a final resource scheduling sequence result.
(VIII) obtaining a target two-dimensional image by using the existing two-dimensional sparse imaging technology, wherein the specific process is as follows:
and reasonably distributing radar pulse resources according to the resource scheduling model, alternately observing targets, and after receiving target echo signals, realizing inverse synthetic aperture radar two-dimensional imaging on each target by using the conventional two-dimensional sparse imaging technology.
By adopting the technical scheme of the invention, the resource allocation of the single-step radar facing to multiple targets can be realized from the aspects of the target azimuth direction and the distance direction, the radar resources are saved, and the overall performance of a radar system is improved.
Drawings
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a diagram of the corresponding SPI in each priority ranking mode;
FIG. 3 is a diagram illustrating a radar resource scheduling result according to the present invention.
Detailed Description
The following description will be made with reference to the accompanying drawings and examples, but the present invention is not limited thereto.
Example (b):
let T be 1s for scheduling interval and F for sub-pulse repetition frequencyPRF10kHz, the total number of sub-pulses within the scheduling interval: ptotall=T×F PRF10000, N in the scheduling interval TtotallThe individual target applies for an imaging task.
Fig. 1 shows a resource adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging, which is implemented by calculating the pulse resource demand of each target on the basis of feature cognition of each target by a radar, determining the sub-pulse transmitting position required to be allocated to each target according to the constraint condition selected by the radar, and acquiring echoes through alternate observation of the targets, thereby completing the inverse synthetic aperture imaging task of multiple targets, and comprises the following steps:
the radar transmits a small amount of pulses to each target and estimates the flight parameters of the target, and the specific process is as follows:
the waveform parameters for estimating the target parameters of a small number of pulses transmitted by each target are set as follows: carrier frequency frcSub-pulse width T of 10GHzrp0.3 mus, frequency step length Δ fr3M, bandwidth Br300 MHz. Randomly selecting 300 sub-pulses to transmit to each target, and measuring the distance between the jth target and the radar by using a radar conventional algorithm after radar echo signals are obtainedTarget speedTarget courseTarget heightThe respective target parameters are shown in table 1.
TABLE 1 target parameter tables
(II) estimating the two-dimensional size of the target, wherein the specific process is as follows:
reconstruction F for filling zero in missing part of received echo dataPRFThe data of each observation point is used as the echo signal of the target coarse resolution inverse synthetic aperture radar image, and the echo signal of each target is processedThe wave signals are processed by inverse synthetic aperture radar imaging to obtain a rough image of each target, which is recorded as Srj(k, l). And normalizing the image to obtain a normalized image, which is recorded as S'rj(k,l):
Where k and l represent the target distance and azimuth envelope positions, respectively, according to the formula ρrr=c/(2Br) Calculating the distance resolution according toAnd calculating the azimuth resolution. Selecting a threshold value Ts0.38, the calculated distance is minimal towards the envelope positionAnd maximum distance to envelope positionAccording to the relation between the target distance and the envelope position, the distance dimension of the jth target can be obtainedWhere ρ isrr=c/(2Br) Is the distance resolution; the minimum and maximum values of the position envelope position in the azimuth direction are calculated by the same method respectivelyThe azimuth dimension of the jth target can be obtainedWhereinFor azimuthal resolution, the two-dimensional recognition results for each target were calculated as shown in table 2 below.
TABLE 2 target feature recognition results
(III) determining the number of target transmission pulse trains and the number of sub-pulse transmissions under the pulse trains by the radar, and the specific process is as follows:
setting a target distance to a reference dimensionReference dimension of azimuthAnd the distance-to-reference resolution ρ required for imagingrefrAzimuthal reference resolution ρrefaThe distance direction rho of the j th target required for imagingjrAnd azimuthal resolution ρjaComprises the following steps:
whereinIs the jth target range dimension,Is the jth target azimuth dimension. Setting the minimum value of the azimuth resolution as rhomina. The target distance is set to the reference dimensionAn azimuth reference dimension ofDistance direction reference resolution is rhorefr0.5m and an azimuth reference resolution ρrefa0.5m, the maximum frequency step length Δ f required to allow the radar to show the size profile of all targets completely unambiguousjComprises the following steps:
where c is the speed of light, the number of transmitted minimum sub-pulses N in the pulse train of the jth targetjComprises the following steps:
in order to meet the requirement of the required azimuth resolution for imaging the jth target, the number M of the required transmission pulse trainsjComprises the following steps:
wherein u is1In order to adjust a constant greater than 1 for the number of the transmitted bursts, the value is 1.1, λ is the signal wavelength, and the results of calculating the number of the bursts to be transmitted for each target and the number of the sub-pulses transmitted under the bursts are shown in table 2 above.
And (IV) estimating the target azimuth sparsity and the distance sparsity, wherein the specific process is as follows:
coarse resolution inverse synthetic aperture radar image S for jth targetrjThe line normalization process for which the element sum value in (k, l) is the maximum is S'rj(l) The column normalization process with the largest sum of elements is S ″rj(k):
Setting the threshold value to TM0.3, mixing S'rj(l) Discretized representation is vector S'rjThen the azimuth sparsity of the jth targetIs vector S'rjIs greater than TMThe number of elements (c). S ″)rj(k) The discretization is represented as vector S ″rjThen the distance of the jth target is sparseIs vector S ″)rjIs greater than TMThe number of elements (c):
the results of estimation of the azimuth sparsity and the range sparsity of each target are shown in table 2 above.
And (V) determining the number of the target azimuth sparse transmission pulse trains and the number of the distance sparse transmission sub-pulses, wherein the specific process is as follows:
according to the compressed sensing theory, the number L of the pulse trains which are sparsely transmitted in the azimuth direction and the distance direction and are required by the jth targetjNumber of and subpulses ZjRespectively as follows:
wherein c is1The value of the constant is 0.51, and the estimation results of the number of the pulse trains emitted sparsely in each target direction and the number of the sub-pulses emitted sparsely in each target direction are shown in the table 2.
And (VI) calculating the threat degree of the target by the following specific process:
calculation of the threat degree mainly considers the distance of the targetSpeed of rotationCourse of courseHeightFour parameters, assuming that the radar needs to be on NtotallImaging an object, NtotallThese four factors affecting the threat for each target are written in the form of a matrix:
A=(aij)4×Ntotall (10)
in the formula, aij(i=1,2…,4;j=1,2…,Ntotall) A threat coefficient representing an ith factor of a jth target, i ═ 1,2 …,4 represent the distance of the target from the radar, the speed of the target, the heading of the target, and the altitude of the target, respectively, and j ═ 1,2 …, Ntotall;
Normalizing each factor to Y according to formula (11)ijThe weight of each factor is calculated as beta by the equation (12)i:
Calculating the threat degree of the jth target according to the following formula:
wherein beta is1、β2、β3、β4Weight coefficients are obtained for the distance from the target to the radar, the speed of the target, the heading of the target and the height of the target, respectively, and estimation results of the threat degrees of the targets are shown in table 2 above.
And (seventhly), under the condition of meeting the resource constraint, carrying out the specific process of resource allocation according to the resource scheduling model as follows:
setting 4 different priorities from high to low is: 0.4, 0.3, 0.2, 0.1, N for which there is a task application in the scheduling intervaltotallThe free ranking of 4 targets with 4 different priorities results in 24 prioritization as shown in table 3 below.
TABLE 3 target priority ranking list
Calculating the SPI of each combination in the 24 priority sorting modes according to the principle that each combination is firstly substituted into the following model for resource allocation according to the target priority:
pulse train I'jiThe sum of the number of the sub-pulses in the pulse train is less than or equal to Nj
The impulse resource allocation procedure according to equation (18) can be described as:
step 1: setting the initial time j as 1, using the most front sub-pulse in the current rest idle pulse as the start position start for observing the j th target emission sub-pulsej;
Step 2: according to the number M of the sub-pulses required during the full-aperture observationj×NjDetermining the position of a terminator pulse of the task;
step 3: from the starting position to the end position by NjFor spacing, uniformly dividing MjA pulse train;
step 4: randomly picking out L from the currentjEach pulse train being randomly inserted Z within each selected pulse trainjAnd observing the sub-pulses.
Step 5: if j < NtotallAnd j equals j +1 and returns to the first step.
Step 6: obtaining a target sequence number sequence N for completing the imaging task within the scheduling interval T under the priority ordering modesThe number Nu of targets for completing the imaging task;
step 7: the sum of the target threat degrees, the scheduling success rate, the pulse resource utilization rate and the performance index of the radar completing the imaging task under the priority ranking mode is calculated as follows:
(1) the sum of the target threat degrees of the radar completing the imaging task is as follows:
wherein N issRepresenting a target sequence number sequence for completing the imaging task in a scheduling interval T, wherein Nu is the number of targets for completing the imaging task in the scheduling interval;
(2) the scheduling success rate is as follows: the ratio of the number of targets actually and successfully executing the imaging tasks to the number of targets applying for executing the imaging tasks in the scheduling interval T is as follows:
wherein N istotallAnd applying the total number of targets for executing the imaging tasks in the scheduling interval.
(3) The utilization rate of pulse resources is as follows: in the scheduling interval T, the ratio of the number of the sub-pulses occupied by the imaging task to the total number of the sub-pulses in the scheduling interval is completed:
(4) sum of performance indexes:
SPI=w1·STC+w2·SSR+w3·PRU (17)
wherein the weight coefficient is w1=0.3、w2=0.5、w3=0.2;
The ith pulse train transmitted by the radar to the jth target is I'ji。
And (3) according to the principle that each combination in the 24 priority ordering modes is substituted into the model to perform resource allocation according to the target priority, calculating the SPI of each combination through the allocation processes from Step1 to Step7, and selecting a pulse resource allocation sequence with the largest sum of the performance indexes and the SPI meeting the conditions of 3 constraints in the model as a final resource scheduling sequence result as shown in fig. 3 as shown in fig. 2.
(eighth) finally, obtaining a target two-dimensional image by using the existing two-dimensional sparse imaging technology, wherein the specific process is as follows:
and reasonably distributing radar pulse resources according to the resource scheduling model, alternately observing targets, and after receiving target echo signals, realizing inverse synthetic aperture radar two-dimensional imaging on each target by using the conventional two-dimensional sparse imaging technology.
By adopting the technical scheme of the invention, the resource allocation of the single-step radar facing to multiple targets can be realized from the aspects of the target azimuth direction and the distance direction, the radar resources are saved, and the overall performance of a radar system is improved.
The embodiments of the present invention have been described in detail with reference to the drawings and examples, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention.
Claims (1)
1. A resource self-adaptive scheduling method for inverse synthetic aperture radar two-dimensional sparse imaging is characterized by comprising the following steps of calculating the pulse resource demand of each target on the basis that the radar performs feature cognition on each target, further determining the sub-pulse transmitting position required to be distributed by each target according to the constraint condition selected by the radar, and finishing inverse synthetic aperture imaging tasks of a plurality of targets by alternately observing the targets and acquiring target echo signals, wherein the resource self-adaptive scheduling method comprises the following steps:
the radar transmits a small amount of pulses to each target, and target flight parameters are estimated;
(II) estimating the two-dimensional size of the target;
thirdly, determining the number of target transmission pulse trains of the radar and the number of sub-pulse transmissions under the pulse trains;
fourthly, estimating the azimuth sparsity and the distance sparsity of the target;
fifthly, determining the number of the radar to the target azimuth sparse transmission pulse trains and the number of the distance sparse transmission sub-pulses;
sixthly, calculating the threat degree of the target;
establishing a resource scheduling model and performing pulse resource allocation under the condition of meeting resource constraint;
(VIII) obtaining a target two-dimensional image by using a two-dimensional sparse imaging technology;
the specific process of the step (I) is as follows:
the waveform parameters for estimating the target parameters of a small number of pulses transmitted by each target are set as follows: carrier frequency frcPulse width T of sub-pulserpFrequency step length Δ frSub-pulse repetition frequency FPRFBandwidth Br(ii) a After the radar echo signal is obtained, the distance of the jth target from the radar can be measured by a radar conventional algorithmTarget speedTarget courseTarget height
The specific process of the step (II) is as follows:
for radar echo signals, an inverse synthetic aperture radar imaging method in the prior art is adopted to obtain a j-th target coarse resolution inverse synthetic aperture radar image Srj(k, l) normalizing the inverse synthetic aperture radar image using the following equation:
wherein k and l respectively represent the position of the target distance direction and the position direction envelope, and a proper threshold T is setsCalculating distance to envelope position minimumAnd maximum distance to envelope positionAccording to the relation between the target distance and the envelope position, the distance dimension of the jth target can be obtainedWhere ρ isrr=c/(2Br) Is the distance resolution; the minimum and maximum values of the position envelope position in the azimuth direction are calculated by the same method respectivelyThe azimuth dimension of the jth target can be obtainedWhereinThe azimuth resolution is;
the specific process of the step (III) is as follows:
setting a target distance to a reference dimensionReference dimension of azimuthAnd the distance-to-reference resolution ρ required for imagingrefrAzimuthal reference resolution ρrefaThen the distance resolution ρ required for imaging the jth targetjrAnd azimuthal resolution ρjaComprises the following steps:
whereinIs the jth target range dimension,Is the jth target azimuth dimension; setting the minimum value of the azimuth resolution as rhomina(ii) a The maximum frequency step length Δ f required to allow the radar to show the size profile of all targets without ambiguity at alljComprises the following steps:
where c is the speed of light, the number of transmitted minimum sub-pulses N in the pulse train of the jth targetjComprises the following steps:
in order to meet the requirement of the required azimuth resolution for imaging the jth target, the number M of the required transmission pulse trainsjComprises the following steps:
wherein u is1A constant greater than 1 for adjusting the number of transmit bursts, λ being the signal wavelength, FPRFA sub-pulse repetition frequency;
the specific process of the step (IV) is as follows:
coarse resolution inverse synthetic aperture radar image S for jth targetrjThe row with the largest element sum value in (k, l) was normalized to S 'as follows'rj(l) The element sum maximum column is normalized as S ″, as followsrj(k):
Setting a suitable threshold value to TMIs prepared from S'rj(l) Discretized representation is vector S'rjWill be S ″)rj(k) The discretization is represented as vector S ″rjThen the azimuth sparsity of the jth targetAnd distance to sparsityComprises the following steps:
the concrete process of the step (V) is as follows:
according to the compressed sensing theory, the number of pulse trains and the number of sub-pulses which are sparsely transmitted in the azimuth direction and the distance direction required by the jth target are respectively as follows:
wherein c is1The value is a constant related to the recovery precision and is between 0.5 and 2;
the specific process of the step (six) is as follows:
calculation of the threat degree mainly considers the distance of the targetSpeed of rotationCourse of courseHeightFour parameters, assuming that the radar needs to be on NtotallImaging an object, NtotallThese four factors affecting the threat for each target are written in the form of a matrix:
in the formula, aijA threat coefficient representing an ith factor of a jth target, i ═ 1,2 …,4 represent the distance of the target from the radar, the speed of the target, the heading of the target, and the altitude of the target, respectively, and j ═ 1,2 …, Ntotall;
Normalizing the factors according to equation (11)Converted into YijThe weight of each factor is calculated as beta by the equation (12)i:
Calculating the threat degree of the jth target according to the following formula:
wherein beta is1、β2、β3、β4Obtaining weight coefficients for the distance from the target to the radar, the speed of the target, the course of the target and the height of the target respectively;
the specific process of the step (VII) is as follows:
suppose the scheduling interval is T and the sub-pulse repetition frequency is FPRFThen the total number of sub-pulses within the scheduling interval: ptotall=T×FPRF;
Based on the basis, the following performance indexes are defined for the radar imaging resource scheduling algorithm:
(1) the sum of the target threat degrees of the radar completing the imaging task is as follows:
wherein N issRepresenting a target sequence number sequence for completing the imaging task in a scheduling interval T, wherein Nu is the number of targets for completing the imaging task in the scheduling interval;
(2) the scheduling success rate is as follows: the ratio of the number of targets actually and successfully executing the imaging tasks to the number of targets applying for executing the imaging tasks in the scheduling interval T is as follows:
wherein N istotallThe total number of targets for applying for executing the imaging tasks in the scheduling interval;
(3) the pulse resource utilization ratio is the ratio of the number of sub-pulses occupied by completing the imaging task to the total number of sub-pulses in the scheduling interval within the scheduling interval T:
(4) sum of performance indexes:
SPI=w1·STC+w2·SSR+w3·PRU (17)
wherein w1、w2、w3A weight coefficient;
based on the performance indexes, a resource scheduling model is established as follows:
any pulse train of I'jiThe sum of the number of the sub-pulses in the pulse train is less than or equal to Nj
The resource scheduling model according to equation (18) can be described as:
step 1: setting the initial time j as 1, using the most front sub-pulse in the current rest idle pulse as the start position start for observing the j th target emission sub-pulsej;
Step 2: according to the number M of the sub-pulses required during the full-aperture observationj×NjDetermining the position of a terminator pulse of the task;
step 3: from the starting position to the end position by NjFor spacing, uniformly dividing MjA pulse train;
step 4: randomly picking out L from the currentjEach pulse train being randomly inserted Z within each selected pulse trainjAn observation sub-pulse;
step 5: if j < NtotallIf j is j +1, returning to the first step;
step 6: obtaining a target sequence number sequence N for completing the imaging task within the scheduling interval T under the priority ordering modesThe number Nu of targets for completing the imaging task;
step 7: calculating the sum of target threat degrees, scheduling success rate, pulse resource utilization rate and performance index of the radar completing imaging tasks in the priority ranking mode;
adding the above-mentioned NtotallEach combination in the priority sorting mode is substituted into the model for resource allocation according to the principle that the target priority is high and high, through the allocation process from Step1 to Step7, the SPI of each combination is calculated, and a pulse resource allocation sequence with the largest Sum of Performance Indexes (SPI) and meeting the conditions of 3 constraints in the model is selected as a final resource scheduling sequence result;
the specific process of the step (eight) is as follows:
and reasonably distributing radar pulse resources according to the resource scheduling model, alternately observing targets, and after receiving target echo signals, realizing inverse synthetic aperture radar two-dimensional imaging on each target by using a two-dimensional sparse imaging technology.
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