CN102495408B - Method for automatically searching point of synthetic aperture radar dot-matrix target image data - Google Patents

Abstract

The invention discloses a method for automatically searching a point of synthetic aperture radar dot-matrix target image data. The method comprises the following steps of: 1, correcting an antenna directional diagram weighing factor; 2, correcting radar receiving power; 3, searching a bidimensional maximum value; 4, positioning a pixel position of a point target; 5, checking the position; and 6, performing bidimensional frequency domain interpolation, and positioning a precise position of the point target. Automatic point search for the synthetic aperture radar dot-matrix target image data is realized, so that the working quantity of manual point search operation is reduced; the non-uniformity of the amplitude of the point target caused by reasons, such as antenna weighing, is overcome; the point search accuracy is high; the precise position of a dot-matrix target in the synthetic aperture radar image data can be obtained, and is used for precisely positioning a calibrator; the positioning precision of the target position is adjusted by controlling the interpolation magnification; automatic estimation for the dot-matrix target in the synthetic aperture radar image data is realized; an average performance index of the image data is obtained; and an actual performance index of a system can be reflected.

Description

A kind of automatic seeking point methods of synthetic-aperture radar dot-matrix target image data

Technical field

The invention belongs to the signal processing technology field, be specifically related to a kind of automatic seeking point methods of synthetic-aperture radar dot-matrix target image data.

Background technology

Synthetic-aperture radar (Synthetic Aperture Radar, SAR) is a kind of round-the-clock, round-the-clock active Information Acquisition System.The SAR system transmits and receives mode by gating pulse, obtains SAR original echo data.These data along the carrier heading be the orientation to, perpendicular to the orientation to direction be distance to.Process by SAR original echo data being carried out data, obtain visual radar image.

Be different from optical imagery, in the SAR view data, typical point target is not simple impulse function.Point target shows as the main lobe with certain broadening, and is accompanied by a large amount of secondary lobes around it.The patent " for the synthesis of the self-adaption two-dimensional interpolation method of aperture radar point target imaging quality assessment " of the applications such as the article " double-base SAR point target image quality evaluation algorithm " that the patent of the applications such as Sun Bing " a kind of point target resolution appraisal procedure of Squint SAR ", Ceng Tao etc. deliver, Yu Ze utilizes this characteristics of point target to measure just.

Impact due to antenna gain, radar received power, to a single point target assess the image property index of gained can not complete reaction the actual performance of system, need to arrange the dot matrix target in a scene, and ask for the performance index of this each point target of scene, obtain the average image performance index.Existing method selected element target adopts the pattern of man-machine interaction, and only the dot matrix of 16 * 16 sizes just needs manually to select 256 times, complex operation.And existing method only can provide the Pixel-level position of point target in the SAR image.

But there are many difficult points in the Automatic-searching technology of point target.Secondary lobe has the character almost identical with the point target main lobe, and when point target quantity increases, the shape of secondary lobe will be more complicated.Antenna radiation pattern and radar received power make SAR view data mid point target strength skewness, can make large hot spot target side-lobe energy surpass weak intensity point target main lobe, further cause the difficulty of differentiating point target.

Summary of the invention

The present invention proposes a kind of automatic seeking point methods of synthetic-aperture radar dot-matrix target image data, the method is for dot matrix target synthetic-aperture radar complex pattern data, the weighting impact of compensation antenna radiation pattern and radar received power, point target Pixel-level position in these data of Automatic-searching utilizes interpolation to obtain the exact position of point target at last.The method is sought a little precision higher than pixel precision, helps the accurate geographic location of point target, can realize the automated quality assessment of synthetic-aperture radar dot matrix target complex pattern data, obtains the average behavior index of image.

A kind of automatic seeking point methods of synthetic-aperture radar dot-matrix target image data comprises following step:

Step 1: antenna radiation pattern weighted correction;

Initialization is also read SAR image complex data, calculates the corresponding antenna radiation pattern weighting factor of each range gate, obtains realizing the antenna radiation pattern weighted correction to SAR image complex data along distance to the antenna compensation vector that distributes.

Step 2: the radar received power is proofreaied and correct;

Obtain radar power equation corresponding to each range gate, to through image complex data S ' edge of antenna radiation pattern weighted correction apart to compensating, obtain the uniform SAR image of dot matrix target amplitude complex data S ".

Step 3: seek two-dimentional maximum point;

Ask for the uniform SAR image of dot matrix target amplitude complex data S " in two-dimentional maximum point, make the point target position of seeking all be contained in set K.Then remove set K middle distance to or the incomplete extreme point of azimuth accumulation.

Step 4: the point target location of pixels is located;

Utilize sensitive factor to judge, extract the position of dot matrix target among two-dimentional maximum value set K, form new dot matrix goal set E, the Pixel-level position of point target has been preserved in this set.

Step 5: location verification;

Whether the point target in checking dot matrix goal set E satisfies the typical characteristics of SAR system imaging target, if do not satisfy turn back to step 4, carries out location, point target exact position if meet enter step 6.

Step 6: two-dimensional frequency interpolation, location, point target exact position.

In dot matrix goal set E centered by the Pixel-level position of point target, get the evaluating matrix L that 32 * 32 matrix element on every side consists of this point target in original SAR image complex data.Evaluating matrix L is carried out the two-dimensional frequency interpolation, select the interpolation multiple for positioning accuracy request, obtain the exact position of point target.

The invention has the advantages that:

(1) realize the automatic seeking point of synthetic-aperture radar dot-matrix target image data, reduced the workload of manually seeking point operation;

(2) overcome the point target amplitude nonuniformity that causes due to reasons such as antenna weightings, sought an accuracy rate high;

(3) can obtain the exact position of dot matrix target in the diameter radar image data, can be used for scaler and accurately locate, by controlling interpolation multiple, the bearing accuracy of adjustable program cursor position;

(4) can be used for realizing diameter radar image data dot matrix target automatic evaluation, obtain the average behavior index of view data, more can reflect the actual performance index of system.

Description of drawings

Fig. 1 is the independent positioning method process flow diagram of seeking of the present invention;

Fig. 2 is bearing accuracy of the present invention and interpolation multiple graph of a relation.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

The present invention is a kind of automatic seeking point methods of synthetic-aperture radar dot-matrix target image data, processing to as if synthetic-aperture radar dot matrix target complex pattern data, the result that obtains is the exact position of each point target in data.Synthetic-aperture radar dot matrix target complex pattern data are two-dimentional complex matrixs Size is M * N.Wherein M represents the orientation to pulse number, and N represents that distance is to sampling number.At first the present invention has compensated non-homogeneousization of point target amplitude that the complex pattern data cause apart from the antenna radiation pattern weighted sum radar received power that makes progress, reconstruct two-dimentional maximum point object set, utilize the iteration adjustment sensitive factor to remove secondary lobe point in two-dimentional maximum point target tightening and form Pixel-level point target collection, at last two-dimensional interpolation is carried out in Pixel-level point target position, obtain the exact position of point target in the diameter radar image data.

The flow process of method comprises following step as shown in Figure 1:

Step 1: antenna radiation pattern weighted correction;

Initialization is also read SAR image complex data, calculates each range gate corresponding visual angle, obtains antenna compensating factor corresponding to this visual angle, forms constructing antennas directional diagram correction matrix, realizes the antenna radiation pattern weighted correction to SAR image complex data.

Be specially:

Obtain each range gate j (j=1,2,3...N) corresponding oblique distance distance R _j:

$R_j=R_1+\frac{(j-1)\·C}{2f_s}$

Wherein: R ₁Oblique distance distance corresponding to this point during for first sampled point (being j=1), C represents the light velocity, f _sExpression distance to sampling rate.

Obtain this oblique distance distance R _jCorresponding view angle theta _j:

θ _j＝arccos(R _ref/H)-arccos(R _j/H)

Wherein: R _refOblique distance corresponding to representative antennas sight line center irradiation, H is aircraft altitude.

Obtain this view angle theta _jCorresponding antenna compensating factor a _jFor:

$a_j=\frac{\mathrm{\π}{D}_r\sin \left({\mathrm{\θ}}_j\right)/\mathrm{\λ}}{\sin (\mathrm{\π}{D}_r\sin \left({\mathrm{\θ}}_j\right)/\mathrm{\λ})}$

Wherein: D _rTo antenna length, λ is the wavelength that transmits for distance.

Repeat above step, obtain each distance to the compensating factor a of antenna radiation pattern corresponding to sampled point _j(j=1,2,3...N).

Constructing antennas directional diagram correction matrix A, this matrix are the diagonal angle real number matrix of N * N, and this matrix diagonal element is antenna pattern compensation factor a _j, off-diagonal element is zero, namely

Complex pattern data matrix S and antenna radiation pattern correction matrix A carry out the diameter radar image complex data S ' after matrix multiple obtains the antenna radiation pattern correction, realize the antenna radiation pattern weighted correction to SAR image complex data.

Step 2: the radar received power is proofreaied and correct;

Obtain radar received power compensating factor corresponding to each range gate, to through image complex data S ' edge of antenna radiation pattern weighted correction apart to compensating, obtain the uniform SAR image of dot matrix target amplitude complex data S ".

Be specially:

Obtain j (j=1,2,3...N) the corresponding oblique distance of individual range gate is apart from radar received power compensating factor:

$p_j=\sqrt{4\mathrm{\π}{R_j}^4{\mathrm{\λ}}^2}$

Repeat above step, obtain each distance to antenna pattern compensation factor p corresponding to sampled point _j(j=1,2,3...N).Structure radar received power correction matrix P, this matrix is the diagonal angle real number matrix of N * N, this matrix diagonal element is antenna pattern compensation factor p _j, off-diagonal element is zero, namely

Make data matrix S ' carry out matrix multiple with radar received power correction matrix P, to through image complex data S ' edge the distance of antenna radiation pattern weighted correction to compensating, obtain the diameter radar image complex data S after the radar received power compensates ".

Step 3: seek two-dimentional maximum point;

Ask for the uniform SAR image of dot matrix target amplitude complex data S " in two-dimentional maximum point; make the point target position of seeking all be contained in two-dimentional maximum value set K, then remove two-dimentional maximum value set K middle distance to or the incomplete extreme point of azimuth accumulation.

Be specially:

The complex data matrix S " is asked mould to process, obtained new real number matrix

Get real number matrix R _SMiddle arbitrary element r _ij, judge whether this element satisfies r _{I, j}＞r _{I+1, j}, whether satisfy r _{I, j}＞r _{I, j+1}, whether satisfy r _{I, j}＞r _{I-1, j}, whether satisfy r _{I, j}＞r _{I, j-1}, whether satisfy r _{I, j}＞r _{I+1, j+1}, whether satisfy r _{I, j}＞r _{I-1, j-1}, whether satisfy r _{I, j}＞r _{I+1, j-1}, whether satisfy r _{I, j}＞r _{I-1, j+1}If above-mentioned condition all satisfies, with this element at real number matrix R _SIn position (i, j) be recorded in two-dimentional maximum value set K.

Repeat above step, to real number matrix R _SMiddle all elements r _ij(i=2,3,4...M-1, j=2,3,4...N-1) judge, form two-dimentional maximum value set K.

For the element (p, q) in two-dimentional maximum value set K, r _{P, q}Be R _SIn element, p, q are that this element is at R _SIn the position.

Get arbitrary element (p, q) in two-dimentional maximum value set K, judge whether p satisfies T _pf _s＜p＜N-T _pf _s, judge whether q satisfies T _aPrf＜q＜M-T _aPrf, wherein T _pBe pulse width, f _sBe sampling rate, T _aBe the synthetic aperture time, prf is pulse repetition rate.If above-mentioned condition has one not satisfy, this element (p, q) is removed in two-dimentional maximum value set K, remove two-dimentional maximum value set K middle distance to or the incomplete extreme point of azimuth accumulation.

If two-dimentional maximum value set K is empty set, judge not have the dot matrix target in the complex pattern data matrix S, withdraw from institute in steps.If only there is an element in two-dimentional maximum value set K, directly enter step 6.Two dimension maximum value set K interior element enters step 4 more than or equal to two.

Step 4: point target Pixel-level position;

Utilize sensitive factor to judge, extract the position of dot matrix target among two-dimentional maximum value set K, form new dot matrix goal set E, the Pixel-level position of point target has been preserved in this set.

Be specially:

Ask for real number matrix R _SThe element r of middle numerical value maximum _{X, y}=max (R _S).

Count represents the number of times of iteration, and during iteration, count is 0 for the first time, and iteration and later count will be provided by step 5 for the second time.

The definition sensitive factor is

$g_e=r_{x,y}\&CenterDot;{10}^{\frac{-13+(\mathrm{count}-1)\&CenterDot;\mathrm{<figure-callout\; id="20"\; label="d"\; filenames="HDA0000116858370000021.png"\; state="\{\{state\}\}">d</figure-callout>}}{20}}$

In formula, d has represented the fine degree that in each iteration, sensitive factor changes.The more a little bigger target localization of d value is more accurate, and locating speed is slower.

For element (p, q) in two-dimentional maximum value set K, if r _{P, q}＞g _e, this element position is recorded in dot matrix object set E.

Repeat above step, process all elements in two-dimentional maximum value set K, obtain dot matrix object set E.For the arbitrary element (x, y) in dot matrix object set E, r _{X, y}Be R _SIn element, x, y are e _{X, y}At R _SIn the position.

If dot matrix object set E is empty set, judge not have the dot matrix target in the complex pattern data matrix S, after withdrawing from, institute is in steps.If only there is an element in dot matrix object set E, enter step 6.If in dot matrix object set E, element number more than or equal to two, enters step 5.

Step 5: location verification;

Whether the point target in checking dot matrix goal set E satisfies the typical characteristics of SAR system imaging target, if do not satisfy turn back to step 4, carries out location, point target exact position if meet enter step 6.

Be specially:

For the arbitrary element (x, y) in dot matrix object set E:

Seeking in dot matrix object set E and make | t-x| is minimum, and distance is the element (t, y) of y to the position.If 20log10 is (r _{T, y}/ r _{X, y}) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6.

Seeking in dot matrix object set E and make | f-y| is minimum, and the orientation is the element (x, f) of x to the position.If 20log10 is (r _{X, f}/ r _{X, y}) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6.

Repeat above step, after each element in dot matrix object set E is verified, complete dot matrix target location checking.

Element in dot matrix object set E has recorded the location of pixels of point target in the complex pattern data matrix S.

Step 6: two-dimensional frequency interpolation, location, point target exact position.

In dot matrix goal set E centered by the Pixel-level position of point target, get the evaluating matrix L that 32 * 32 matrix element on every side consists of this point target in original SAR image complex data.Evaluating matrix L is carried out the two-dimensional frequency interpolation, select the interpolation multiple for positioning accuracy request, obtain the exact position of point target.

Be specially:

For the arbitrary element (x, y) in dot matrix object set E, the element of its correspondence in the complex pattern data matrix S is s _{X, y}, centered by this element position, get the evaluating matrix L that 32 * 32 bit matrix elements around this point consist of this point target.Namely get top-left position and be (x-15, y-15) in the complex pattern data matrix S, the position, bottom right is the square formation of (x+16, y+16), and assignment is to evaluating matrix L.

For the evaluating matrix L of this point target, at first the edge distance is to carrying out Fast Fourier Transform (FFT), namely

Then along the orientation to carrying out Fast Fourier Transform (FFT), namely

New two-dimensional matrix is carried out the edge distance carry out the zero padding operation to frequency spectrum shift and in the centre, the zero padding figure place is U=32 * (2 ^M-1) individual, 2 ^MTo the interpolation multiple, wherein M is positive integer for distance, and concrete mode is

$({l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}{l_{i3}}^{\&prime;\&prime;}...{l_{i32}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{i17}}^{\&prime;\&prime;}{l_{i18}}^{\&prime;\&prime;}...{l_{i32}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{1\&times;U}{l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}...{l_{i16}}^{\&prime;\&prime;})$

New two-dimensional matrix is carried out moving and carrying out the zero padding operation in the centre along azimuth spectrum, and the zero padding figure place is V=32 * (2 ^N-1) individual, 2 ^NTo the interpolation multiple, wherein N is positive integer for the orientation, and concrete mode is

$({l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}{l_{3j}}^{\&prime;\&prime;}...{l_{32j}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{17j}}^{\&prime;\&prime;}{l_{18j}}^{\&prime;\&prime;}...{l_{32j}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{V\&times;1}{l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}...{l_{16j}}^{\&prime;\&prime;})$

Carry out again two-dimentional inverse Fourier transform, obtain the evaluating matrix L ' after interpolation.

L ' asks mould to evaluating matrix, obtains new real number matrix R '.Ask for the middle maximal value of real number matrix R ' position (r _x', r _y').This point target corresponding exact position in the complex pattern data matrix S is

$(\frac{{r_x}^{\&prime;}+2^M-1}{2^M}+x-15,\frac{{r_y}^{\&prime;}+2^N-1}{2^N}+y-15).$

Repeat above step, each element in dot matrix object set E is carried out two-dimensional interpolation, obtain each point target corresponding exact position.

In the SAR system, the position of target by distance to the orientation to sampling rate determine, the position of target may be dropped in sampled point in the SAR image hardly just usually.Utilize the method for this patent, can obtain the exact position of target, the levels of precision of target location by the distance to interpolation multiple 2 ^MDetermine, the relation of target exact position and difference multiple as shown in Figure 2.In the calibration process of SAR system, the accurate location of target is significant to system calibration.

Embodiment:

Table 1 radar parameter

According to radar parameter that table 1 is given, original SAR image complex data size is 8192 * 16384 complex matrixs, and this matrix orientation is to totally 8192 sampled points, and distance remembers that to totally 16384 sampled points this complex matrix is

Step 1: antenna radiation pattern weighted correction;

Obtain each range gate j (j=1,2,3...16384) corresponding oblique distance distance R _j:

$R_j=7071.068+\frac{(j-1)\&CenterDot;3\&times;{10}^8}{2\&times;400\&times;{10}^6}$

Obtain this oblique distance distance R _jCorresponding view angle theta _j:

θ _j＝arccos(7071.068/10000)-arccos(7071.068/R _j)

Obtain this view angle theta _jCorresponding compensating factor a _jFor:

$a_j=\frac{\mathrm{\&pi;}\&times;1\&times;\sin \left({\mathrm{\&theta;}}_j\right)/0.05}{\sin (\mathrm{\&pi;}\&times;1\&times;\sin \left({\mathrm{\&theta;}}_j\right)/0.05)}$

Repeat above step, obtain each distance to antenna pattern compensation factor a corresponding to sampled point _j(j=1,2,3...16384).

Constructing antennas directional diagram correction matrix A, this matrix are 16384 * 16384 diagonal angle real number matrix,

Diameter radar image complex data after proofreading and correct through antenna radiation pattern is 8192 * 16384 complex matrix, i.e. S ' _{8192 * 16384}=S _{8192 * 16384}* A _{16384 * 16384}

Step 2: the radar received power is proofreaied and correct;

Obtain j (j=1,2,3...16384) the corresponding oblique distance of individual range gate is apart from radar received power compensating factor:

$p_j=\sqrt{4\mathrm{\&pi;}\&times;{R_j}^4\&times;{0.05}^2}$

Repeat above step, obtain antenna pattern compensation factor p corresponding to each range gate _j(j=1,2,3...16384).

Structure radar received power correction matrix P, this matrix is the diagonal angle real number matrix of N * N, this matrix diagonal element is antenna pattern compensation factor p _j, off-diagonal element is zero, namely

Make data matrix S ' carry out diameter radar image complex data S after matrix multiple obtains radar received power compensation with radar received power correction matrix P ".

Diameter radar image complex data after compensating through the radar received power is 8192 * 16384 complex matrix, i.e. S " _{8192 * 16384}=S ' _{8192 * 16384}* P _{16384 * 16384}

Step 3: seek two-dimentional maximum point;

The complex data matrix S " is asked mould to process, obtained new real number matrix

Get real number matrix R _SMiddle arbitrary element r _ij, judge whether this element satisfies r _{I, j}＞r _{I+1, j}, whether satisfy r _{I, j}＞r _{I, j+1}, whether satisfy r _{I, j}＞r _{I-1, j}, whether satisfy r _{I, j}＞r _{I, j-1}, whether satisfy r _{I, j}＞r _{I+1, j+1}, whether satisfy r _{I, j}＞r _{I-1, j-1}, whether satisfy r _{I, j}＞r _{I+1, j-1}, whether satisfy r _{I, j}＞r _{I-1, j+1}If above-mentioned condition all satisfies, with this element at real number matrix R _SIn position (i, j) be recorded in the set K in.

Repeat above step, to real number matrix R _SMiddle all elements r _ij(i=2,3,4...8191, j=2,3,4...16383) judge, form two-dimentional maximum value set K.

Get arbitrary element (p, q) in two-dimentional maximum value rendezvous value set K, judge whether p satisfies 0.00001 * 400000000＜p＜16384-0.00001 * 400000000, judge whether q satisfies 3.333 * 1000＜q＜8192-3.333 * 1000.If above-mentioned condition has one not satisfy, this element (p, q) is removed in two-dimentional maximum value set K.

If two-dimentional maximum value set K is empty set, judge not have the dot matrix target in the complex pattern data matrix S, withdraw from institute in steps.If only there is an element in two-dimentional maximum value set K, directly enter step 6.Two dimension maximum value set K interior element enters step 4 more than or equal to two.

Step 4: point target Pixel-level position;

Ask for real number matrix R _SThe element r of middle numerical value maximum _{X, y}=max (R _S).

Count represents the number of times of iteration, and during iteration, count is 0 for the first time, and iteration and later count will be provided by step 5 for the second time.

Sensitive factor is:

$g_e=r_{x,y}\&CenterDot;{10}^{\frac{-13+(\mathrm{count}-1)\&CenterDot;\mathrm{<figure-callout\; id="20"\; label="d"\; filenames="HDA0000116858370000021.png"\; state="\{\{state\}\}">d</figure-callout>}}{20}}$

To element (p, q) in two-dimentional maximum value set K, judge that this element is at matrix R _SIn whether satisfy r _{P, q}＞g _e, this element position is recorded in dot matrix object set E as satisfying.

Repeat above step, process all elements in two-dimentional maximum value set K, obtain dot matrix object set E.

If dot matrix object set E is empty set, judge not have the dot matrix target in the complex pattern data matrix S, after withdrawing from, institute is in steps.If only there is an element in dot matrix object set E, enter step 6.If in dot matrix object set E, element number more than or equal to two, enters step 5.

Step 5: location verification;

Arbitrary element (x, y) in dot matrix object set E is carried out location verification:

Seeking in dot matrix object set E and make | t-x| is minimum, and distance is the element (t, y) of y to the position.If 20log10 is (r _{T, y}/ r _{X, y}) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6.。

Seeking in dot matrix object set E and make | f-y| is minimum, and the orientation is the element (x, f) of x to the position.If 20log10 is (r _{X, f}/ r _{X, y}) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6.。

Repeat above step, after each element in dot matrix object set E is verified, complete dot matrix target location checking.

Element in dot matrix object set E has recorded the location of pixels of point target in the complex pattern data matrix S.

Step 6: two-dimensional frequency interpolation, location, point target exact position.

For the arbitrary element (x, y) in dot matrix object set E, the element of its correspondence in the complex pattern data matrix S is s _{X, y}, centered by this element position, get the evaluating matrix L that 32 * 32 bit matrix elements around this point consist of this point target.Namely get top-left position and be (x-15, y-15) in the complex pattern data matrix S, the position, bottom right is the square formation of (x+16, y+16), and assignment is to evaluating matrix L.

For the evaluating matrix L of this point target, at first the edge distance is to carrying out Fast Fourier Transform (FFT), namely

Then along the orientation to carrying out Fast Fourier Transform (FFT), namely

New two-dimensional matrix is carried out the edge distance carry out the zero padding operation to frequency spectrum shift and in the centre, example adopts 64 times of distances to sample interpolation, and zero padding figure place is U=32 * (2 ⁶-1)=2016.Concrete mode is

$({l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}{l_{i3}}^{\&prime;\&prime;}...{l_{i32}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{i17}}^{\&prime;\&prime;}{l_{i18}}^{\&prime;\&prime;}...{l_{i32}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{1\&times;U}{l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}...{l_{i16}}^{\&prime;\&prime;})$

New two-dimensional matrix is carried out moving and carrying out the zero padding operation in the centre along azimuth spectrum, and example adopts 64 times of orientation to sample interpolation, and the zero padding figure place is V=32 * (2 ⁶-1)=2016.Concrete mode is

$({l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}{l_{3j}}^{\&prime;\&prime;}...{l_{32j}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{17j}}^{\&prime;\&prime;}{l_{18j}}^{\&prime;\&prime;}...{l_{32j}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{V\&times;1}{l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}...{l_{16j}}^{\&prime;\&prime;})$

Carry out again two-dimentional inverse Fourier transform, obtain the evaluating matrix L ' after interpolation.

L ' asks mould to evaluating matrix, obtains new real number matrix R '.Ask for the middle maximal value of real number matrix R ' position (r _x', r _y').The Pixel-level position is that point target corresponding exact position in the complex pattern data matrix S of (x, y) is

$(\frac{{r_x}^{\&prime;}+63}{64}+x-15,\frac{{r_y}^{\&prime;}+63}{64}+y-15).$

Repeat above step, each element in dot matrix object set E is carried out two-dimensional interpolation, obtain each point target corresponding exact position.

Table 2 has provided and has utilized the present invention to seek point methods to seek a result in different SAR image complex datas.As can be seen from Table 2, it is good to the adaptability of target scene that the present invention seeks point methods, the extensive matrix of the small-scale dot matrix to 128 from 2 * 2 * 128, position that can all point targets of automatic search.

Table 2 utilizes a result of seeking of this patent method

	Point target number in the SAR image	The present invention seeks a number
			2 * 2 dot matrix SAR images	4	4
4 * 4 dot matrix SAR images	16	16
			8 * 8 dot matrix SAR images	64	64
16 * 16 dot matrix SAR images	256	256
			32 * 32 dot matrix SAR images	1024	1024
64 * 64 dot matrix SAR images	4096	4096
			128 * 128 dot matrix SAR images	16384	16384

Claims (7)

1. the automatic seeking point methods of a synthetic-aperture radar dot-matrix target image data, is characterized in that, processing to as if synthetic-aperture radar dot matrix target complex pattern data, the result that obtains is the exact position of each point target in data; Synthetic-aperture radar dot matrix target complex pattern data are

Size is M * N; Wherein M represents the orientation to pulse number, and N represents that distance to sampling number, comprises following step:

Step 1: antenna radiation pattern weighted correction;

Initialization is also read SAR image complex data, calculates the corresponding antenna radiation pattern weighting factor of each range gate, obtains realizing the antenna radiation pattern weighted correction to SAR image complex data along distance to the antenna compensation vector that distributes;

Step 2: the radar received power is proofreaied and correct;

Obtain radar power equation corresponding to each range gate, to through image complex data S ' edge of antenna radiation pattern weighted correction apart to compensating, obtain the uniform SAR image of dot matrix target amplitude complex data S ";

Step 3: seek two-dimentional maximum point;

Ask for the uniform SAR image of dot matrix target amplitude complex data S " in two-dimentional maximum point; make the point target position of seeking all be contained in set K; then remove set K middle distance to or the incomplete extreme point of azimuth accumulation; if two-dimentional maximum value set K is empty set; judge not have the dot matrix target in the complex pattern data matrix S; withdraw from institute in steps, if only there is an element in two-dimentional maximum value set K, directly enter step 6, two dimension maximum value set K interior element enters step 4 more than or equal to two;

Step 4: the point target location of pixels is located;

Utilize sensitive factor to judge, extract the position of dot matrix target among two-dimentional maximum value set K, form new dot matrix goal set E, the Pixel-level position of point target has been preserved in this set, if dot matrix object set E is empty set, judge and do not have the dot matrix target in the complex pattern data matrix S, after withdrawing from, institute in steps, if only there is an element in dot matrix object set E, enters step 6, if in dot matrix object set E, element number more than or equal to two, enters step 5;

Step 5: location verification;

Whether the point target in checking dot matrix goal set E satisfies the typical characteristics of SAR system imaging target, if do not satisfy turn back to step 4, carries out location, point target exact position if meet enter step 6;

Step 6: two-dimensional frequency interpolation, location, point target exact position;

In dot matrix goal set E centered by the Pixel-level position of point target, get the evaluating matrix L that 32 * 32 matrix element on every side consists of this point target in original SAR image complex data, evaluating matrix L is carried out the two-dimensional frequency interpolation, select the interpolation multiple for positioning accuracy request, obtain the exact position of point target.

2. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 1 is specially:

Obtain the corresponding oblique distance distance R of each range gate j _j, j=1,2,3...N:

$R_j=R_1+\frac{(j-1)\&CenterDot;C}{2f_s}$

Wherein: R ₁Oblique distance distance corresponding to this point during for first sampled point, C represents the light velocity, f _sExpression distance to sampling rate; Obtain this oblique distance distance R _jCorresponding view angle theta _j:

θ _j＝arccos(R _ref/H)-arccos(R _j/H)

Wherein: R _refOblique distance corresponding to representative antennas sight line center irradiation, H is aircraft altitude;

Obtain this view angle theta _jCorresponding antenna compensating factor a _jFor:

$a_j=\frac{\mathrm{\&pi;}{D}_r\sin \left({\mathrm{\&theta;}}_j\right)/\mathrm{\&lambda;}}{\sin (\mathrm{\&pi;}{D}_r\sin \left({\mathrm{\&theta;}}_j\right)/\mathrm{\&lambda;})}$

Wherein: D _rTo antenna length, λ is the wavelength that transmits for distance;

Repeat above step, obtain each distance to the compensating factor a of antenna radiation pattern corresponding to sampled point _j

Constructing antennas directional diagram correction matrix A, this matrix are the diagonal angle real number matrix of N * N, and this matrix diagonal element is antenna pattern compensation factor a _j, off-diagonal element is zero, namely

Complex pattern data matrix S and antenna radiation pattern correction matrix A carry out the diameter radar image complex data S ' after matrix multiple obtains the antenna radiation pattern correction, realize the antenna radiation pattern weighted correction to SAR image complex data.

3. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 2 is specially:

Obtain j the corresponding oblique distance of range gate apart from radar received power compensating factor:

$p_j=\sqrt{4\mathrm{\&pi;}{R_j}^4{\mathrm{\&lambda;}}^2}$

Repeat above step, obtain each distance to antenna pattern compensation factor p corresponding to sampled point _j

Structure radar received power correction matrix P, this matrix is the diagonal angle real number matrix of N * N, this matrix diagonal element is antenna pattern compensation factor p _j, off-diagonal element is zero, namely

Make data matrix S ' carry out matrix multiple with radar received power correction matrix P, to through image complex data S ' edge the distance of antenna radiation pattern weighted correction to compensating, obtain the diameter radar image complex data S after the radar received power compensates ".

4. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 3 is specially:

The complex data matrix S " is asked mould to process, obtained new real number matrix

Get real number matrix R _SMiddle arbitrary element r _ij, judge whether this element satisfies r _{I, j}＞r _{I+1, j}, whether satisfy r _{I, j}＞r _{I, j+1}, whether satisfy r _{I, j}＞r _{I-1, j}, whether satisfy r _i,j＞r _{I, j-1}, whether satisfy r _{I, j}＞r _{I+1, j+1}, whether satisfy r _{I, j}＞r _{I-1, j-1}, whether satisfy r _{I, j}＞r _{I+1, j-1}, whether satisfy r _{I, j}＞r _{I-1, j+1}If above-mentioned condition all satisfies, with this element at real number matrix R _SIn position (i, j) be recorded in two-dimentional maximum value set K, i=2 wherein, 3,4...M-1, j=2,3,4...N-1;

Repeat above step, to real number matrix R _SMiddle all elements r _ijJudge, form two-dimentional maximum value set K;

For the element (p, q) in two-dimentional maximum value set K, r _p,qBe R _SIn element, p, q are that this element is at R _SIn the position;

Get arbitrary element (p, q) in two-dimentional maximum value set K, judge whether p satisfies T _pf _s＜p＜N-T _pf _s, judge whether q satisfies T _aPrf＜q＜M-T _aPrf, wherein T _pBe pulse width, f _sBe sampling rate, T _aBe the synthetic aperture time, prf is pulse repetition rate; If above-mentioned condition has one not satisfy, this element (p, q) is removed in two-dimentional maximum value set K, remove two-dimentional maximum value set K middle distance to or the incomplete extreme point of azimuth accumulation;

If two-dimentional maximum value set K is empty set, judge not have the dot matrix target in the complex pattern data matrix S, withdraw from institute in steps; If only there is an element in two-dimentional maximum value set K, directly enter step 6; Two dimension maximum value set K interior element enters step 4 more than or equal to two.

5. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 4 is specially:

Ask for real number matrix R _SThe element r of middle numerical value maximum _x,y=max (R _S);

Count represents the number of times of iteration, and during iteration, count is 0 for the first time, and iteration and later count will be provided by step 5 for the second time;

The definition sensitive factor is

$g_e=r_{x,y}\&CenterDot;{10}^{\frac{-13+(\mathrm{count}-1)\&CenterDot;d}{20}}$

In formula, d has represented the fine degree that in each iteration, sensitive factor changes; The more a little bigger target localization of d value is more accurate, and locating speed is slower;

For element (p, q) in two-dimentional maximum value set K, if r _p,q＞g _e, this element position is recorded in dot matrix object set E;

Repeat above step, process all elements in two-dimentional maximum value set K, obtain dot matrix object set E; For the arbitrary element (x, y) in dot matrix object set E, r _x,yBe R _SIn element, x, y are r _x,yAt R _SIn the position;

If dot matrix object set E is empty set, judge not have the dot matrix target in the complex pattern data matrix S, after withdrawing from, institute is in steps; If only there is an element in dot matrix object set E, enter step 6; If in dot matrix object set E, element number more than or equal to two, enters step 5.

6. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 5 is specially:

For the arbitrary element (x, y) in dot matrix object set E:

Seeking in dot matrix object set E and make | t-x| is minimum, and apart from being the element (t, y) of y to the position, t, y are r _{T, y}At R _SIn the position; If 20log10 is (r _{T, y}/ r _x,y) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6;

Seeking in dot matrix object set E and make | f-y| is minimum, and the orientation is the element (x, f) of x to the position, and x, f are r _{X, f}At R _SIn the position; If 20log10 is (r _x,f/ r _x,y) 〉=-10 returns to step 4, and count=count+1, otherwise, enter step 6;

Repeat above step, after each element in dot matrix object set E is verified, complete dot matrix target location checking;

Element in dot matrix object set E has recorded the location of pixels of point target in the complex pattern data matrix S.

7. the automatic seeking point methods of a kind of synthetic-aperture radar dot-matrix target image data according to claim 1, is characterized in that, described step 6 is specially:

For the arbitrary element (x, y) in dot matrix object set E, the element of its correspondence in the complex pattern data matrix S is s _{X, y}, centered by this element position, get the evaluating matrix L that 32 * 32 bit matrix elements around this point consist of this point target; Namely get top-left position and be (x-15, y-15) in the complex pattern data matrix S, the position, bottom right is the square formation of (x+16, y+16), and assignment is to evaluating matrix L;

For the evaluating matrix L of this point target, at first the edge distance is to carrying out Fast Fourier Transform (FFT), namely

Then along the orientation to carrying out Fast Fourier Transform (FFT), namely

New two-dimensional matrix is carried out the edge distance carry out the zero padding operation to frequency spectrum shift and in the centre, the zero padding figure place is U=32 * (2 ^M-1) individual, 2 ^MTo the interpolation multiple, wherein M is positive integer for distance, and concrete mode is

$({l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}{l_{i3}}^{\&prime;\&prime;}...{l_{i32}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{i17}}^{\&prime;\&prime;}{l_{i18}}^{\&prime;\&prime;}...{i_{i32}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{1\&times;U}{l_{i1}}^{\&prime;\&prime;}{l_{i2}}^{\&prime;\&prime;}...{l_{i16}}^{\&prime;\&prime;})$

New two-dimensional matrix is carried out moving and carrying out the zero padding operation in the centre along azimuth spectrum, and the zero padding figure place is V=32 * (2 ^N-1) individual, 2 ^NTo the interpolation multiple, wherein N is positive integer for the orientation, and concrete mode is

$({l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}{l_{3j}}^{\&prime;\&prime;}...{l_{32j}}^{\&prime;\&prime;})\&DoubleRightArrow;({l_{17j}}^{\&prime;\&prime;}{l_{18j}}^{\&prime;\&prime;}...{i_{32j}}^{\&prime;\&prime;}{(\mathrm{0,0}...0)}_{V\&times;1}{l_{1j}}^{\&prime;\&prime;}{l_{2j}}^{\&prime;\&prime;}...{l_{16j}}^{\&prime;\&prime;})$

Carry out again two-dimentional inverse Fourier transform, obtain the evaluating matrix L ' after interpolation;

L ' asks mould to evaluating matrix, obtains new real number matrix R '; Ask for the middle maximal value of real number matrix R ' position (r _x', r _y'); This point target corresponding exact position in the complex pattern data matrix S is

$(\frac{{r_x}^{\&prime;}+2^M-1}{2^M}+x-15,\frac{{r_y}^{\&prime;}+2^N-1}{2^N}+y-15);$

Repeat above step, each element in dot matrix object set E is carried out two-dimensional interpolation, obtain each point target corresponding exact position.

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