CN101285884A - Inverse synthetic aperture radar image-forming time selection method - Google Patents

Abstract

The invention discloses a new method for selecting imaging time of an inverse synthetic aperture radar. The method comprises the main steps of: firstly, processing echo data by distance compression and movement compensation (envelope alignment and initial phase correction), selecting a stable reference distance unit based on a normalized amplitude variance criterion, and determining a corresponding weighted coefficient; secondly; carrying out phase history estimation on echo signals of each reference distance unit, and carrying out weighting processing on the phase history of the echo signals of each reference distance unit according to the weighted coefficient so as to obtain a weighted phase; thirdly, carrying out ISAR imaging time selection according to a weighted phase curve so as to select an optimal imaging data section. The method directly carries out optimal ISAR imaging time selection processing on the echo data which is processed by the distance compression and the movement compensation. Accordingly, the method is simple in arithmetic, small in calculation, simple in engineering realization, and strong in realizability.

Description

A kind of inverse synthetic aperture radar image-forming time selection method

Technical field

The present invention's design is that a kind of imaging time in the inverse synthetic aperture radar (ISAR) imaging signal process field is selected new method, is applicable to the imaging signal disposal system of ISAR system to aerial or sea-surface target.

Background technology

Over past ten years, very big progress has been arranged in the ISAR technology.Aspect algorithm, relatively effective I SAR imaging algorithm mainly comprises at present: FFT is apart from Doppler's method, polar format facture, instantaneous time-frequency formation method etc.; In engineering practice, obtained good application at the aspects such as space track target imaging of cooperation.

But for the ship of the aircraft of maneuvering flight or sea navigation, because the non-cooperative of target travel, the ISAR The Application of Technology also is faced with many difficulties, requires further improvement and develops.Concrete condition is, and is relatively easy for the ISAR imaging of the Aircraft Target of smooth flight, directly carries out RANGE-DOPPLER IMAGING under the enough situation of corner; And for maneuvering target (non-cooperation), non-linear (as the jolting of sea Ship Target, pitching, roll etc.) of its motion, imaging processing difficulty.

The thinking that addresses this problem at present is: at first according to optimum imaging time system of selection, choose optimum imaging time section from the echo data of observation, choose effective I SAR imaging algorithm then this data segment is carried out imaging.Aspect optimum imaging time system of selection, research relatively lags behind, present domestic external enwergy retrieves only following several method: estimate and based on the optimum imaging time system of selection of image dopplerbroadening, these methods all do not have to be applied in actual engineering at present based on picture quality, based target kinematic parameter.Wherein, the based target kinematic parameter is estimated and based on the optimum imaging time system of selection of image dopplerbroadening, the algorithm complexity, and operand is big, and effect is bad in measured data is handled, and the Project Realization difficulty is big; Based on the optimum imaging time system of selection of picture quality, algorithm is simple, but operand is big.

Purpose of the present invention proposes at the weak point in the above-mentioned background technology just.The present invention directly through motion compensation apart from the echo territory in, realize the automatic selection processing of ISAR imaging time according to the comprehensive phase history of a plurality of strong scattering point echoes of target.Advantage of the present invention is, algorithm is simple, and operand is little, and effective in real data is handled, and is easy to realize and characteristics such as popularization.

Summary of the invention

The object of the present invention is achieved like this, and method of the present invention comprises following technical measures:

(1) echo data is carried out distance compression and motion compensation (envelope alignment and first phase are proofreaied and correct) processing;

(2) choose stable reference distance unit based on normalization amplitude variance criterion, and definite weighting coefficient;

(3) echoed signal of each reference distance unit being carried out phase history estimates;

(4) according to weighting coefficient the phase history of each reference distance elementary echo signal is weighted processing, obtains weighted phases history;

(5) carry out the ISAR imaging time according to the weighted phases history curve and select, choose optimum imaging data segment.

Purpose of the present invention can also realize by following technical measures:

(1) utilize the echoed signal doppler phase history curve of single reference distance unit to carry out optimum ISAR imaging time selection.

(2), carry out Doppler frequency and extract and weighted, and carry out optimum ISAR imaging time according to weighting Doppler frequency curve and select to the echoed signal of each reference distance unit.

(3) utilize the echoed signal Doppler frequency curve of single reference distance unit to carry out optimum ISAR imaging time selection.

The present invention compares background technology and has following advantage:

(1) the present invention is directly carrying out optimum ISAR imaging time selection processing through the echo data after distance compression and the motion compensation, and algorithm is simple, and operand is little.

(2) the inventive method implementation complexity is low, and Project Realization is simple, and realizability is strong.

(3) the inventive method is good to the measured data treatment effect, has application value.

Description of drawings

Accompanying drawing is the block diagram of embodiments of the invention.

With reference to accompanying drawing, embodiments of the invention are by Range compress 1, motion compensation 2, and the reference distance unit selects 3, phase history Estimate and the optimum imaging time selection 5 of weighting processing 4, ISAR and imaging 6 compositions. Embodiment neutron Range compress wherein Processing 1 is used for finishing carries out distance to the compression processing to the echo data that receives; After motion compensation 2 is used for adjusting the distance and compresses Echo data carries out motion compensation (comprising the correction of envelope alignment and first phase); The reference distance unit selects 3 to be used for carrying out with reference to distance From the selection of unit, its Q selected reference distance unit is followed successively by 3-1 to 3-Q, and determines corresponding each reference distance unit Weight coefficient; Phase history is estimated and weighting processing 4 phase history that are used for finishing each reference distance elementary echo signal are estimated Meter and phase weighting are processed; The optimum imaging time selection 5 of ISAR is used for finishing the selection of optimum ISAR imaging time section; Imaging Processing 6 is used for the optimal data section of selecting is carried out imaging.

Embodiment

It is as follows to implement principle of the present invention: at first echo data is carried out distance compression and motion compensation process, choose stable range unit based on normalization amplitude variance criterion, and definite weighting coefficient; Then, the echoed signal of each range unit of choosing is carried out phase history estimate, and carry out weighted, obtain weighted phases history; At last, carrying out optimum ISAR imaging time according to the weighted phases curve selects.

If the echo data matrix size is M * N, M is a pulse number, and N is the distance samples unit number.After it is carried out distance compression and motion compensation process, because the caused envelope of radial motion moves with phase error to be fallen by compensation, therefore, the range unit amplitude scintillation of determining based on normalization amplitude variance criterion can be changed minimum range unit as the reference distance unit of choosing.In normalization amplitude variance criterion, normalization amplitude variance is defined as

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">n</figure-callout>}}^2=\frac{\stackrel{\&OverBar;}{{(u_n-{\stackrel{\&OverBar;}{u}}_n)}^2}}{\stackrel{\&OverBar;}{u_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}}=1-\frac{{\stackrel{\&OverBar;}{u}}_n^2}{\stackrel{\&OverBar;}{u_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}}---\left(1\right)$

N represents each range unit in the formula, and the horizontal expression on the symbol is averaged u to each element in this range unit _nBe the average of n range unit echo sequence amplitude, u _n ²It is its mean square value.

To normalization amplitude variance criterion, according to normalization amplitude variances sigma _n ²Standard Selection Q less than 0.12 stable range unit, in actual treatment, 0.12 standard can be adjusted a little according to real data.Utilize normalization amplitude scintillation variance to determine the weighting coefficient w of each range unit of choosing then _q, its computing method are

$w_q=1/[\stackrel{\&OverBar;}{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">q</figure-callout>}}^2}\&CenterDot;\underset{i=1}{\overset{\mathrm{<figure-callout\; id="1"\; label="Q"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">Q</figure-callout>}}{\mathrm{\&Sigma;}}}\frac{1}{\stackrel{\&OverBar;}{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="q"\; filenames="A20071005183500071.png"\; state="\{\{state\}\}">q</figure-callout>}}^2}}]---\left(2\right)$

Wherein q represents each reference distance unit.

When each reference distance unit being carried out the phase spectrum estimation,, twine processing so must separate to its phase place because phase place is to change in the cycle with 2 π.If

Be the winding phase place of certain pixel cell, Φ _q(m) for this pixel cell separate the winding phase place, m=1,2,3 ..., M.Then solutions of path integration winding algorithm is

Wherein

Utilize formula (4), according to its neighbouring relations, extrapolation can solve phase unwrapping around problem length by length, obtains the phase spectrum Φ of each reference distance unit correspondence _q(m).Because the path of one dimension integration is unique, also is unique so it is separated.

And then to the phase spectrum Φ of each reference distance unit _q(m), according to weighting coefficient, be weighted processing, obtain the phase spectrum after the weighting

For

The detailed step of whole invention once is described below in conjunction with example:

(1) size that radar is received is that the echo data matrix of M * N carries out distance compression by the unit among Fig. 11 and handles, and the systematic parameter of distance compression is determined by the radar system that installs the ISAR image-generating unit additional;

(2) echo data of adjusting the distance after compressing carries out motion compensation process by the unit among Fig. 12, wherein, at first carries out envelope alignment and handles, and carries out the first phase treatment for correcting then;

(3), calculate the normalization amplitude variances sigma of each range unit echoed signal successively by the unit among Fig. 13 to the data matrix after the motion compensation process _n ², according to normalization amplitude variances sigma _n ²Standard less than 0.12 selects Q stable range unit as the reference range unit; Simultaneously, according to the normalization amplitude variances sigma of each reference distance elementary echo signal _n ²(q=1,2,3 ..., Q), calculate the weighting coefficient w of corresponding each reference distance unit q _q

(4), undertaken along the orientation to carrying out phase unwrapping by the unit among Fig. 14, and then obtain the phase history Φ of each reference distance elementary echo signal around processing to each reference distance elementary echo signal _q(m); And according to weighting coefficient w _qTwine phase place Φ with separating of each reference distance elementary echo signal _q(m) be weighted processing, obtain weighted phases history

(5) according to the weighted phases of obtaining

Curve is finished optimum SAR imaging time by the unit among Fig. 15 and is selected.

To the selected echo data section in unit 5, be sent to image forming process unit 6, through direct display-object imaging results after the imaging processing.

Claims (1)

1 one kinds of inverse synthetic aperture radar image-forming time selection methods is characterized in that comprising following major technique measure:

(1) chooses the reference distance unit based on normalization amplitude variance criterion, determine weighting coefficient, and the echoed signal phase history of each reference distance unit is estimated;

(2) phase history according to weighting coefficient and each reference distance elementary echo signal is weighted processing; Obtain weighted phases history, and carry out the ISAR imaging time according to the weighted phases history curve and select.

It is characterized in that and can also realize by following technical measures:

(1) each range unit echoed signal to choosing is carried out Doppler frequency and is extracted and weighted, and carries out the ISAR imaging time according to weighting Doppler frequency curve and select.

(2) utilize the doppler phase history curve of single reference distance unit to carry out the selection of ISAR imaging time.

(3) utilize the doppler phase frequency curve of single reference distance unit to carry out the selection of ISAR imaging time.

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