CN104569970B - A kind of self-focusing method being imaged for airborne radar forward sight pulse - Google Patents
A kind of self-focusing method being imaged for airborne radar forward sight pulse Download PDFInfo
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- CN104569970B CN104569970B CN201410816984.0A CN201410816984A CN104569970B CN 104569970 B CN104569970 B CN 104569970B CN 201410816984 A CN201410816984 A CN 201410816984A CN 104569970 B CN104569970 B CN 104569970B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/42—Simultaneous measurement of distance and other co-ordinates
- G01S13/44—Monopulse radar, i.e. simultaneous lobing
- G01S13/4418—Monopulse radar, i.e. simultaneous lobing with means for eliminating radar-dependent errors in angle measurements, e.g. multipath effects
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/42—Simultaneous measurement of distance and other co-ordinates
- G01S13/44—Monopulse radar, i.e. simultaneous lobing
- G01S13/4472—Monopulse radar, i.e. simultaneous lobing with means specially adapted to airborne monopulse systems
Abstract
A kind of self-focusing method being imaged for airborne radar forward sight pulse disclosed by the invention, comprises the following steps：1）Sample data is extracted one by one to all range gates；2）Mirror angular curve is estimated；3）To step 1）The sample data of acquisition carries out pulse imaging；4）To step 1）The sample data of acquisition is screened；5）Obtain new sample data；6）To step 5）The new sample data repeat step 2 obtained）To step 5）Form iterative process；7）Pulse imaging is carried out to initial data using the mirror angular curve obtained by final estimation, image needed for obtaining.This method can be under conditions of mirror angular curve be unknown, automatically it is accurate from echo data to estimate mirror angular curve, so that influence of the angle error to imaging effect is reduced, and it is effective to a variety of relief datas, robustness is a kind of practical airborne radar forword-looking imaging self-focusing technology preferably.
Description
Technical field
It is particularly a kind of to be used for before airborne radar the present invention relates to airbome monopulse radar forword-looking imaging signal processing technology
The self-focusing method being imaged depending on pulse.
Background technology
In order to break through limitation of the antenna aperature length to radar imagery azimuth resolution, two-dimentional high-definition picture is obtained,
Current motion platform radar is often implemented as using synthetic aperture radar (SAR) technology or Doppler beam sharpening (DBS) technology
Picture.However, existing SAR and DBS imagings can not be covered immediately ahead of flight path, do not possess forward sight high resolution capability, formed
So-called imaging " blind area ".And forward vision areas is for motion platform, an exactly extremely sensitive region, such region can
The reduction of visual range degree, the undoubtedly important shortcoming of radar imaging technology.
For such case, correlative study unit in various countries' has carried out the research being imaged for motion platform radar foresight successively
Work.Such as (G.Krieger, J.Mittermayer, S.Buckreuss, et al..Sector the imaging radar of document 1
for enhanced visionfür erweitertes Blickfeld[J].Aerospace
What comes into a driver's enhancing sector imaging radar disclosed in Science and Technology, 7 (2003), pp 147~158.)
(SIREV) technology；(Hee-Sub Shin, the Jong-Tae Lim.Omega-k algorithm for airborne of document 2
forward-looking bistatic spotlight SAR imaging[J].IEEE Geoscience and Remote
Sensing Letters,2009,6(2):312~316.), document 3 (T.Espeter, I.Walterscheid, J.Klare,
et al.Bistatic Forward-Looking SAR:Results of a Spaceborne-Airborne[C].IEEE
Geoscience and Remote Sensing Letters 2011,8(4):765~768.) disclosed in double-base SAR before
Depending on imaging technique；(the Derek Iverson.Beam sharpening via multikerneldeconvolution of document 4
[J] .The Boeing Company, Phantom Works, 2000,693~697.) disclosed in based on deconvolution method
Real aperture forword-looking imaging technology；Document 5 is (in Wu Di, Zhu Daiyin, Zhu Zhaoda airborne radars pulse forword-looking imaging algorithm [J]
State's image graphics journal, 2010,15 (3):462~469.), document 6 (Wu Di, Zhu Daiyin, Tian Bin, Zhu Zhaoda pulses be imaged
Algorithm performance analyzes [J] aviation journals, 2012,33 (10):1893~1902.) disclosed in pulse imaging technique etc..
In scheme disclosed above, pulse imaging technique introduces Monopulse estimation during radar imagery, passes through
The raising of image resolution ratio is realized in the estimation of scene moderately and strongly inverse scattering point exact position, possesses that system architecture complexity is low, real-time
By force, the advantages of to carrier aircraft flight track without particular/special requirement, it is a kind of practicable forword-looking imaging scheme, can be directly used for China
The upgrading (can be directly used for and, the active service radar system such as difference beam fire control radar) of existing air force equipment, armament systems.
From the point of view of the signal processing flow of the program, Monopulse estimation is one of key link, angle measurement accuracy
Height directly affects orientation definition improvement.However, as a kind of typical multi-channel system, monopulse radar is in reality
In processing, error between different receiving channels is inevitable, and the error directly results in actual mirror angular curve and design load
Deviation, and then influence the improvement of imaging effect.Effective correction has been carried out to system constant error in floor treatment, flown
The factor such as platform flight attitude also results in the deviation of actual mirror angular curve and design load during row.Further, since radar
Forward-looking mode is worked in, compared with working in positive side view, the radar system of strabismus mode, ground echo signal Doppler's gradient-pole
It is small, therefore mirror angular curve can not be estimated using classical Multichannel radar channel error blind estimating method is automatic from echo data,
Such as (the J.H.G.Ender.The Airborne Experimental Multi-Channel SAR-System AER- II of document 7
[C],In Proceedings of 1996EUSAR Conference(EUSAR’96),Germany,May
1996,49-52.) disclosed in channel error estimation and alignment technique etc..Therefore, how angle measurement is overcome to miss under the conditions of forward sight
Influence of the difference to imaging, realizes image self-focusing, is the key that pulse imaging technique must be solved in actual treatment
Problem.
The content of the invention
The problem to be solved in the present invention is to overcome the pulse image resolution ratio caused by angle error to decline problem.In order to
Above-mentioned purpose is realized, the present invention provides a kind of self-focusing method being imaged for airborne radar forward sight pulse.
A kind of self-focusing method being imaged for airborne radar forward sight pulse disclosed by the invention, comprises the following steps：
1) all range gates of radar return data after pulse compression of adjusting the distance extract sample data one by one；
2) mirror angular curve is estimated；
3) to step 1) obtain sample data carry out pulse imaging；
4) to step 1) obtain sample data screen；
5) new sample data is obtained；
6) to step 5) the new sample data repeat step 2 that obtains) to step 5) form iterative process；
7) pulse imaging is carried out to initial data using the mirror angular curve obtained by final estimation, image needed for obtaining.
Be used as the further improvement of above-mentioned technical proposal, the step 1) extract sample data process be：Will it is each away from
It is considered as isolated strong scattering point echo-signal from energy maximum in door, and to extract the number in a beam angle centered on it
According to.
As an alternative to the above-described technical solution, the step 2) in estimation procedure be by the average side of range gate
Method is estimated mirror angular curve by sample data.
As an alternative to the above-described technical solution, the step 3) in imaging process using step 2) processing after
Reflect angular curve, carries out imaging to each range gate sample data with pulse imaging algorithm, obtains imaging results.
As an alternative to the above-described technical solution, the step 4) in screening process to step 3) processing obtain
Imaging results are screened, and retain the data for being similar to isolated strong scattering point.From pulse imaging algorithm feature, if certain away from
If the sample data chosen from door is similar to isolated strong scattering point, and pulse mirror angular curve is accurate, imaging results are in orientation
To impulse function should be similar to, i.e., there is peak value in position of orientation residing for target, and energy height is concentrated near peak value.Cause
This, each range gate imaging results peak value near zone (we term it peak region) and the Energy distribution situation in other regions can be made
For foundation, for being screened to all samples, obtain being similar to the data of isolated strong scattering point.
As an alternative to the above-described technical solution, the step 5) process that obtains new sample data is according to step
Rapid 4) the selection result and target peak position use step 1) method extract sample data again, that is, obtain new sample number
According to.
As an alternative to the above-described technical solution, the step 6) in the sample data repeat step 2 newly extracted)
To step 5) iterative process is formed, each iteration need to reduce peak region time width in step (4), and when peak region, time width is small
When predetermined value, iteration terminates.
Compared with prior art, the self-focusing method beneficial effect being imaged for airborne radar forward sight pulse of the invention
It is：
This method can be automatically accurate from echo data to estimate mirror angular curve under conditions of mirror angular curve is unknown, from
And influence of the angle error to imaging effect is reduced, and to a variety of relief datas effectively, robustness is a kind of practical machine preferably
Carry radar foresight imaging self-focusing technology.
Brief description of the drawings
Fig. 1 be under scan pattern and, difference beam antenna data collection space geometry graph of a relation；
Fig. 2 is flow chart of data processing figure of the present invention；
Fig. 3 is the SAR image and carrier aircraft course schematic diagram of generation radar return data in emulation experiment；
Fig. 4 is pulse mirror angular curve (emulation data)；
Fig. 5 is different iterative process sample data pulse imaging results range averaging figures (emulation data)；
Fig. 6 is pulse imaging results overall diagram (emulation data)；
Fig. 7 is using the partial enlarged drawing (emulation data) during estimation mirror angular curve processing；
Fig. 8 is using the partial enlarged drawing (emulation data) existed when error mirror angular curve is handled；
Fig. 9 is the pulse mirror angular curve of measured data one；
Figure 10 is the pulse imaging results of measured data one；
Figure 11 be measured data one subregion self-focusing before imaging results (upper area)；
Figure 12 be measured data one subregion self-focusing after imaging results (upper area)；
Figure 13 be measured data one subregion self-focusing before imaging results (lower zone)；
Figure 14 be measured data one subregion self-focusing after imaging results (lower zone)；
Figure 15 is the pulse mirror angular curve of measured data two；
Figure 16 is the pulse imaging results of measured data two；
Figure 17 be measured data two subregion self-focusing before imaging results；
Figure 18 be measured data two subregion self-focusing after imaging results.
Embodiment
Below in conjunction with the accompanying drawings, to a kind of self-focusing method being imaged for airborne radar forward sight pulse proposed by the present invention
It is described in detail.
During antenna scanning, the admission process of radar data is in orientation equivalent to antenna radiation pattern and ground scatter
The convolution process of coefficient.For an ideal point target in wave beam, itself and, difference beam echo data slow time-domain by with, poor day
Line directional diagram is modulated, and antenna radiation pattern can be accurately calculated by echo data and mirror angular curve is thus obtained.
Exemplified by than facies model monopulse antenna, make ∑ (θ), Δ (θ) represent respectively and, difference beam antenna radiation pattern,
Ideally, the relationship of the two is represented by：
Δ (θ)=∑ (θ) jtan (k π θ) (1)
Wherein, j is imaginary unit's variable, and tan () is represented to take arctangent operation, and θ is represented relative to antenna beam center
Azimuth (orientation off-axis angle), k is a constant, relevant with the factor such as monopulse antenna systematic parameter and antenna elevation angle.
Order
Wherein, Im { } is to take imaginary-part operation.Then the relation between (1) formula, M (θ) and relative bearing θ can table
It is shown as：
M (θ)=tan (k π θ) (3)
Above formula discloses the angle measuring principle of monopulse antenna, that is, give pulse and, difference than and target off-axis in wave beam
The relation at angle, therefore often it is also referred to as the mirror angular curve of monopulse antenna.
It is as shown in Figure 1 with poor, beam antenna data recording two-dimensional space geometrical relationship schematic diagram under azimuth scan pattern.If
During data recording, by with beam transmission signal and by being received respectively with, difference beam, wave beam is with angular speed vsAt the uniform velocity inswept point
Target, makes t represent slow time (orientation time) variable, and overlap the moment with point target as time zero (t=using beam central line
0), then continually scanning for wave beam, point target transient bearing off-axis angle is represented by：
θ (t)=- vst (4)
If radar by with beam transmission signal, and by being received respectively with, difference beam, for ease of discussing, put aside echo
Signal distance ties up information, then point target and, difference beam orientation echo-signal S (t), D (t) be represented by：
Wherein, A is point target scattering coefficient.From above formula, accurately antenna direction is contained in point target echo data
Figure modulation intelligence, directly can calculate mirror angular curve, i.e., by it
Inspired by this point, for the monopulse antenna of scan pattern, an angular curve method of estimation of directly reflecting is
From the echo data after pulse compression find similar to point target isolated strong scattering point, orientation extract respectively itself and,
Poor echo-signal, actual mirror angular curve is calculated by the two ratio.However, really there is some problem in this method actual treatment, such as：
Due in practice and in the absence of ideal point target, therefore the selection of isolated strong scattering point is difficult to be automatically performed, and generally requires from real ripple
Artificial judgment in beam images；Choose isolated strong scattering point and extract after data, inevitably there is it due to receiving in data
His target side-lobe signal and receiver noise, the accurate estimation of mirror angular curve need multiple averaging to realize.
For such case, the present invention proposes the side that a kind of realization mirror angular curve automatic from echo data is accurately estimated
Method, because its final purpose is, in order to overcome caused by angle error pulse image resolution ratio to decline problem, therefore to be claimed
Self-focusing method is imaged for pulse, this method is realized the accurate estimation for the angular curve that reflects by some iterative process, is used in combination
Imaging process after, realizes image self-focusing.Its handling process is as shown in Fig. 2 its key step is as follows：
1) sample data is extracted by range gate
If it is after range pulse compression and, poor two-way echo-signal be respectively S (r, t), D (r, t), wherein r represents distance
Door, t represents slow time variable.Position t shown in Energy maximum value in search and each range gate of beam datamax(r), and with tmax
(r) centered on, the range gate is extracted in slow time intervalIt is interior and, difference beam echo data.
Wherein, TβThe time of the inswept beam main lobe width of antenna is represented, i.e.,
Wherein, β represents beam main lobe width.OrderRepresent respectively and, difference beam carried in range gate r
The data taken, whereinFor the corresponding slow time variable of sample data, then
Because the data are subsequently by the estimation for the angular curve that reflects, therefore it is called sample data.The step is substantially
Energy maximum in each range gate is considered as isolated strong scattering point echo-signal, and to extract a beam angle centered on it
Interior data.
2) mirror angular curve is estimated
The process, which is represented by, to be estimated to mirror angular curve by sample data by the average method of range gate：
Wherein,Represent to sum to all range gates, subscript " * " represents conjugate operation,Represent estimation gained
Reflect angular curve.
3) pulse imaging is carried out to sample data
WillAs mirror angular curve, using pulse imaging algorithm to each range gate sample data
Imaging is carried out, imaging results are designated asFrom pulse imaging algorithm feature, if the sample that certain range gate is chosen
If data are similar to isolated strong scattering point, and mirror angular curve is accurate, imaging results should be similar to impulse function in orientation, i.e.,
There is peak value in position of orientation residing for target, and energy height is concentrated near peak value.Therefore, each range gate imaging results peak value
The Energy distribution situation near zone (we term it peak region) and other regions can be as foundation, for entering to all samples
Row screening, retains the data for being similar to isolated strong scattering point.
4) sample data is screened
In each range gate imaging results, search peak positionSet the corresponding time model in peak region
Width is enclosed for TP(initial value can be set to the half or a quarter of sample data time span, i.e., (Or),
Then peak region isIt is calculated as respectively as result peak region energy P1And other area's energy (r)
Measure P2(r) the two ratio, is calculatedAnd with the thresholding η that is previously setT(typically in 0.1~0.3 value) ratio
Compared with so as to judge this apart from the whether similar isolated strong scattering point target of gated data, if retained.The process be represented by as
Lower Hypothesis Testing Problem：
Wherein, H1、H0Assuming that representing the data " comprising isolated strong scattering point " and " not including isolated strong scattering point " respectively.
5) new sample data is obtained
It is H that judged result is rejected from sample data0Range gate, to judged result be H1Range gate, using step 1)
Method extract sample data again.Because the maximum in pulse imaging results also reflects the true position of scattering point simultaneously
Put, therefore need to be according to step 4) the corresponding time location of peak value in imaging resultsThe center t of data is extracted in amendmentmax
(r), i.e.,
Wherein, t 'max(r) represent to extract the stylish center of data.
6) the sample data repeat step 2 to filtering out)~5) form iterative process
To the sample data repeat step 2 newly extracted)~5) form iterative process, each iteration need to reduce step 4) in peak
It is worth area time width TP, work as TPDuring less than preset value (the pulse imaging results of selected data can well focussed), repeatedly
In generation, terminates, and obtains final mirror angular curve estimate.
7) pulse imaging is carried out to initial data with the mirror angular curve finally estimated
With step 6) obtained mirror angular curve carries out pulse imaging to whole data, so as to improve by angle error
Caused image quality decrease.
Using emulate data and measured data processing to pulse proposed by the present invention imaging self-focusing method tested
Card, experimental result fully demonstrates the validity of the method for the present invention.
Emulation data in experiment employ it is airborne and, difference beam monopulse radar forword-looking imaging model, emulation experiment system
System parameter be：Radar wavelength is located at X-band (wavelength 0.03m), and system bandwidth is 500MHz, sample frequency 600MHz, pulse weight
Complex frequency 15kHz, beam positional to 150 °/s of sweep speed, carrier aircraft flying speed 100m/s, imaging area centre distance 2000m,
With beam positional to 2.4 ° of main lobe width, -20 ° of beam positional scanning range~20 °.
The emulation ground scene that experiment is selected is airfield runway region, its High Resolution SAR Images as shown in figure 3, experiment
By scene simulation generation than facies model monopulse radar and, poor echo-signal and carry out respective handling.Dotted line gives in Fig. 4
Emulate the actual pulse mirror angular curve that data are used.The estimation of mirror angular curve and autohemagglutination are carried out using the inventive method to the data
Jiao's processing, in processing, thresholding ηTIt is set to 0.2, peak region time range width TPInitial value be set to sample data time span
A quarter, each iteration reduces half, T during last time iterationPIt is worth for a pulse repetition period (PRI).Fig. 5 gives
During each iterative processing, the azimuthal section figure of sample data pulse imaging results, the figure has all sample data imaging results
Average gained.It can be seen that with the progress of iterative process, the sample data azimuth characteristic of selection is progressively close to " point
Target ", mirror angular curve is progressively close to actual value, therefore the pulse imaging resolution of sample is improved constantly.Final mirror angular curve
Shown in solid in estimated result such as Fig. 4, it can be seen that estimated result is very small with real curve gap, estimation progress is higher.Most
Eventually, Fig. 6 gives the overall imaging results of pulse of Autofocus processing, and Fig. 7, Fig. 8 sets forth using estimation gained mirror angle
Curve and using exist error reflect angular curve imaging results partial enlarged drawing, magnification region be Fig. 6 in boxed area, from into
This it appears that improvement of the present invention to imaging effect in picture result.
Two groups of airbome monopulse radar measured datas are handled, when the common feature of two groups of data is data recording,
There is certain error in actual mirror angular curve, the result side of pulse imaging is directly carried out by theoretical mirror angular curve with design load
Position need to be improved to definition, so as to be verified to the inventive method.
First group of measured data is enrolled by certain type X-band airbome monopulse radar, and image scene is sea area.System band
A width of 2MHz, pulse recurrence frequency 400Hz, beam positional to 15 °/s of sweep speed, carrier aircraft ground velocity 90m/s, into and beam positional
To 3.8 ° of main lobe width, -30 ° of beam positional scanning range~30 °, imaging area central point is apart from 50km.Dotted line gives in Fig. 9
Mirror angular curve according to obtained by being calculated systematic parameter, due to the curve and physical presence error, therefore as the simple venation obtained by the curve
Rush image orientation exist it is a certain degree of defocus, Autofocus processing need to be carried out.Solid line gives autohemagglutination of the present invention in Fig. 9
Mirror angular curve obtained by burnt method estimation, it can be seen that the curve has certain difference with ideal curve.Figure 10 give through
The pulse imaging results crossed after Autofocus processing, in order to (calculate curve obtained using systematic parameter to carry out with before self-focusing
Imaging) image contrasted, and we have chosen two pieces of regions in figure and have carried out partial enlargement, and be provided in Figure 11~Figure 14
Contrast before and after self-focusing, from these figures, it is apparent that after the processing of self-focusing method, due to can from data
The middle accurate mirror angular curve of acquisition, therefore can further improve image quality.
Second group of measured data is enrolled by certain type X-band airbome monopulse radar, and image scene is Mountainous Regions.System band
A width of 4MHz, pulse recurrence frequency 1560Hz, beam positional to 46 °/s of sweep speed, carrier aircraft ground velocity 101m/s, into wave beam side
Position is to 3.6 ° of main lobe width, -40 ° of beam positional scanning range~40 °, and imaging area central point is apart from 40km.In Figure 15 solid line and
Dotted line sets forth estimation gained and as the mirror angular curve obtained by systematic parameter is calculated, it can be seen that both exist certain
Difference.Figure 16~Figure 18 gives the imaging results calculated using self-focusing, and by being carried out before partial enlarged drawing and self-focusing
Contrast, from result this it appears that the validity of algorithm.
Claims (2)
1. a kind of self-focusing method being imaged for airborne radar forward sight pulse, it is characterised in that：Comprise the following steps：
1) all range gates of radar return data after pulse compression of adjusting the distance extract sample data one by one：Using with, difference beam
Signal is received, if being S (r, t) with data of the passage after pulse compression, data of the poor passage after pulse compression are D
(r, t), wherein, r represents range gate, and t represents slow time variable, Energy maximum value institute in search and each range gate of beam data
In position tmax(r), and with tmax(r) centered on, the range gate is extracted in slow time interval
It is interior and, difference beam echo data, wherein, TβRepresent the time of the inswept beam main lobe width of antenna；OrderRepresent respectively and, the sample data extracted in range gate r of difference beam,It is corresponding slow for sample data
Time variable, thenIt is represented by：
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<mo>)</mo>
</mrow>
</mrow>
</mfrac>
<mo>-</mo>
<mo>-</mo>
<mo>-</mo>
<mrow>
<mo>(</mo>
<mn>2</mn>
<mo>)</mo>
</mrow>
</mrow>
Wherein,Represent to sum to all range gates, subscript " * " represents conjugate operation,Represent the mirror obtained by estimation
Angular curve；
3) willAs mirror angular curve, to step 1) obtain sample data Carry out at pulse imaging
Reason, imaging results are designated as
4) to step 3) obtain sample data screen：In each range gate imaging results, search peak positionThe corresponding time range width in peak region is set as TP, then peak region beRespectively
It is calculated as result peak region energy P1And other areas energy P (r)2(r) the two ratio, is calculatedAnd with it is prior
The thresholding η of settingTCompare, judge whether this is retained apart from gated data；
5) new sample data is obtained：According to step 4) the corresponding time location of peak value in imaging resultsNumber is extracted in amendment
According to center tmax(r), the process is represented by：
<mrow>
<msubsup>
<mi>t</mi>
<mrow>
<mi>m</mi>
<mi>a</mi>
<mi>x</mi>
</mrow>
<mo>&prime;</mo>
</msubsup>
<mrow>
<mo>(</mo>
<mi>r</mi>
<mo>)</mo>
</mrow>
<mo>=</mo>
<msub>
<mi>t</mi>
<mrow>
<mi>m</mi>
<mi>a</mi>
<mi>x</mi>
</mrow>
</msub>
<mrow>
<mo>(</mo>
<mi>r</mi>
<mo>)</mo>
</mrow>
<mo>+</mo>
<msub>
<mover>
<mi>t</mi>
<mo>&OverBar;</mo>
</mover>
<mrow>
<mi>m</mi>
<mi>a</mi>
<mi>x</mi>
</mrow>
</msub>
<mrow>
<mo>(</mo>
<mi>r</mi>
<mo>)</mo>
</mrow>
<mo>-</mo>
<mo>-</mo>
<mo>-</mo>
<mrow>
<mo>(</mo>
<mn>11</mn>
<mo>)</mo>
</mrow>
</mrow>
Wherein, t 'max(r) represent to extract the stylish center of data；To step 4) in range gate where retention data use
Step 1) method extract sample data again, during extraction, data center position is set to t 'max(r)；
6) to step 5) the new sample data repeat step 2 that obtains) to step 5) form iterative process；Each iteration needs reduction
Step 4) in peak region time width TP, work as TPDuring less than preset value, iteration ends obtain final mirror angular curve estimation
Value；
7) pulse imaging is carried out to initial data using the mirror angular curve obtained by final estimation, image needed for obtaining.
2. the self-focusing method according to claim 1 being imaged for airborne radar forward sight pulse, it is characterised in that：Institute
State step 4) in screening process be to step 3) the obtained imaging results of processing screen, retain to be similar to and isolate strong scattering point
Data；Judge described be expressed as apart from whether gated data gives reservation：
Wherein, H1、H0Assuming that representing the data " comprising isolated strong scattering point " and " not including isolated strong scattering point " respectively.
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