CN102608594A - Method for suppressing frequency modulation stepping signal from synthesizing high resolution image grating lobe - Google Patents

Abstract

The invention discloses a method for suppressing a frequency modulation stepping signal from synthesizing a high resolution image grating lobe, wherein a return signal of a frequency modulation stepping signal being subjected to sampling and discretization is firstly undergone weighting mismatch filter processing in a quick time dimension, a weighting function satisfies the condition that: delta f is the stepping interval of the frequency modulation stepping signal, B1 is the sub pulse bandwidth of the frequency modulation stepping signal, and K is the main lobe expansion coefficient of the weighting function relative to a rectangular window; and the result which is obtained after weighting mismatch filter processing is undergone synthesis sub distance image processing in a slow time dimension, and a sub distance image is subjected to the whole synthetic one-dimensional distance image processing. Under the condition of no strict requirement on a system parameter design, the method can be used to effectively suppress the time grating lobe of a frequency modulation stepping signal from synthesizing the high resolution image, and the imaging and detecting performances of a frequency stepping radar are improved.

Description

A kind of frequency modulation stairstep signal synthesizes high resolution picture graing lobe inhibition method

Technical field

The present invention relates to the synthetic high resolution picture graing lobe inhibition method of a kind of frequency step signal, more particularly, relate to the synthetic high resolution picture graing lobe inhibition method of a kind of frequency modulation stairstep signal.

Background technology

The frequency modulation stairstep signal is a kind of radar signal with high resolution capacity; It launches the radar pulse of the linear saltus step of carrier frequency between one group of arteries and veins, arteries and veins internal linear frequency modulation, through each sub-pulse echo is carried out in the arteries and veins inverse Fourier transform (IDFT) between pulse compression and arteries and veins handle obtain target apart from high resolution picture.The frequency modulation stairstep signal has replaced the simple pulse in the frequency step signal with the linear frequency modulation subpulse; Therefore overcome the contradiction between radar horizon and the monopulse range resolution; Can under the constant condition of the resolving power of keeping at a distance, reduce umber of pulse again; Improve data transfer rate, reduce requirement system handles bandwidth and sampling rate.

The synthetic bandwidth that need increase the frequency step signal for the raising systemic resolution promptly increases stepped intervals Δ f.But when wide T and stepped intervals product were greater than 1 (T Δ f＞1) when subpulse, uniformly-spaced there was serious time graing lobe problem in frequency hopping frequency step signal.Therefore the false-alarm probability that the periodicity time graing lobe of frequency step signal can cause range ambiguity, target occlusion and increase system must effectively suppress the time graing lobe of frequency step signal imaging and detection deleterious impact.

At present, the graing lobe inhibition method of frequency step signal is a lot.Roll up in Nullifying ACF grating lobes in stepped-frequency train of LFM pulses (the eliminating frequency modulation step-by-step impulse string auto-correlation graing lobe) literary composition on the second phase 694-703 page or leaf at IEEE Transactions on Aerospace and Electronic Systems the 39th in 2003; Introduced, stepped intervals wide during subpulse, subpulse bandwidth triadic relation with the zero setting of graing lobe position through adjustment, thus all or part of elimination frequency modulation stairstep signal graing lobe.But there is bigger overlapping in the frequency band when wide bandwidth amasss greatly when subpulse between the subpulse, and this method is also impracticable.In Suppression of grating lobes in stepped-frequency train (inhibition of the frequency step train of impulses graing lobe) literary composition on the IEEE International Radar Conference 371-376 page or leaf in 2005; Said method has been made improvement; Its thought is 0 for not making the graing lobe position, but less than a less numerical value.This method has been relaxed the requirement that frequency spectrum is overlapped to a certain extent.But above-mentioned two kinds of methods all require to guarantee strict position relation, all need higher sampling rate (being generally more than 10 times of subpulse bandwidth) to suppress effect with the graing lobe that reaches expectation in the time of therefore in applying to imaging.At Proceedings of SPIE in 2008; In Low sidelobe nonlinear stepped-freuency waveforms (the Low Sidelobe frequency step waveform) literary composition on the International Society for Optical Engineering the 6947th volume 1-9 page or leaf; Certain non-linear rule of giving chapter and verse changes different interpulse number of frequency steps to break stepping item time cycle property; Thereby the graing lobe of realizing the frequency step signal suppresses, and this method realizes that too complicacy is difficult to practical application.The present invention is used for the synthetic high resolution picture algorithm of frequency modulation stairstep signal with weighting mismatch filter technology; The time graing lobe that has effectively suppressed the frequency step signal; Improve the imaging of frequency step radar system and detected performance, be particularly useful for the low time graing lobe one-dimensional image of frequency modulation stairstep signal.

Summary of the invention

In view of this; The object of the present invention is to provide a kind of frequency modulation stairstep signal to synthesize high resolution picture graing lobe inhibition method; Systematic parameter design proposition harshness is not being required under the situation; The time graing lobe that effectively suppresses the synthetic high resolution picture of frequency modulation stairstep signal improves the imaging of frequency step radar and detects performance.

In order to achieve the above object, the present invention provides a kind of frequency modulation stairstep signal based on the weighting mismatch filter synthetic high resolution picture graing lobe inhibition method, and said method comprises:

1) echoed signal of the frequency modulation stairstep signal after the sample varianceization being carried out the weighting mismatch filter at fast time dimension (sampling dimension) handles; Wherein, weighting mismatch filter is handled the weighting function that is adopted need satisfy following condition:

$\frac{1}{\mathrm{\Δf}}\≥\frac{1}{B_1}(K+1)$

Wherein, Δ f is the stepped intervals of frequency modulation stairstep signal, B ₁Be the subpulse bandwidth of frequency modulation stairstep signal, the weighting function that K chooses when being the weighting mismatch filter is with respect to the main lobe ceofficient of spread of rectangular window;

2) signal after the step 1) processing being carried out the synthon distance images at slow time dimension (PRT dimension) handles;

3) the antithetical phrase distance images is synthesized omnidistance one-dimensional range profile processing.

Preferably, said step 2) specifically comprise:

Step S301: result after the weighting mismatch filter is carried out zero interpolation processing at slow time dimension; Points N after the assurance interpolation when parameter designing _ZpWith the two product of stepped intervals Δ f of frequency modulation stairstep signal be the integral multiple of systematic sampling rate;

Step S302 is IFFT to the signal after zero interpolation and handles on slow time dimension, obtain the sub-distance images on the different mining sampling point.Preferably, to carry out obtaining M after IFFT handles be δ R apart from length to this step S302 _cThe sub-distance images of=c/2 Δ f, sub-distance images is centered close to R _kSatisfy δ R during parameter designing _c＞δ R _gCondition;

Wherein, δ R _g=cT _g/ 2 for carrying out the fast time dimension coarse resolution unit when handling, T _gBe the SI of frequency modulation stairstep signal, c is the light velocity; M is the sampling number of frequency modulation stairstep signal; R _k=R _m+ k δ R _gBe k distance that sampled point is corresponding in the image-forming range window, R _mBe image-forming range window reference position.

Said step 3) specifically comprises:

Step S401: give up sub-distance images middle distance section [δ R _g/ 2+R _k, δ R _g/ 2+R _k] with exterior portions, only extract in the sub-distance images high-resolution spectral line with R _kFor the center

Individual, wherein

Be the high-resolution spectral line number of single sampled point representative apart from correspondence;

Step S402: the extraction result of different sub distance images is spliced in order and carried out modulo operation, obtain omnidistance one-dimensional range profile.

The present invention compares with existing synthetic high resolution picture graing lobe inhibition method, has following beneficial effect:

(1) the present invention is used for the synthetic high resolution picture algorithm of frequency modulation stairstep signal with weighting mismatch filter technology; And the design weighting function main lobe ceofficient of spread K satisfies condition

makes stepping item graing lobe not fall into frequency modulation item main lobe; The time graing lobe that has effectively suppressed the frequency step signal; Improve the imaging of frequency step radar system and detected performance, be particularly useful for the low time graing lobe one-dimensional image of frequency modulation stairstep signal.Relation between wide when the present invention does not need accurate design subpulse, stepped intervals, the subpulse bandwidth; Wide bandwidth is long-pending when big when the subpulse of frequency modulation stairstep signal, thereby the spectrum overlapping and the systematic sampling rate that still can effectively reduce between subpulse are relaxed the restriction to parameter designing;

(2) the present invention is in the Interpolation Process of synthon distance images, points N after the design interpolation _ZpWith the two product of stepped intervals Δ f of frequency modulation stairstep signal be the integral multiple of systematic sampling rate, thereby guarantee the final result's of extraction correctness

(3) the present invention is when the synthon distance images, through design (the δ R of parameter _c＞δ R _g) guarantee not occur apart from the space between adjacent sub-distance images; When extracting, carry out the extraction of set point number as the center with the target physical location; The extraction result who guarantees the different sub distance images can be not overlapping the basis on; Make and do not destroy the signal inner structure relation that frequency modulation stairstep signal ambiguity function is limited when synthesizing high resolution picture; Thereby guarantee final synthetic result's correctness, can effectively reduce frequency modulation stairstep signal one-dimensional image result's time graing lobe;

(4) realize simply, have stronger practicality.

Description of drawings

Fig. 1 frequency modulation stairstep signal ambiguity function main peak zero Doppler's sectional drawing.

Fig. 2 suppresses the fuzzy graing lobe exemplary plot of frequency modulation stairstep signal through parameter designing.

Fig. 3 weighting mismatch filter suppresses the fuzzy graing lobe exemplary plot of frequency modulation stairstep signal.

Fig. 4 is based on the synthetic high resolution processing theory diagram of weighting mismatch filter.

The fast time dimension weighting of Fig. 5 mismatch filter is handled block diagram.

The slow time dimension synthon of Fig. 6 distance images is handled block diagram.

The synthetic omnidistance one-dimensional range profile of Fig. 7 is handled block diagram.

The synthetic high resolution picture graing lobe inhibition of measured data result (left side is conventional synthetic high resolution picture arithmetic result, and the right side is that the high resolution picture result is synthesized in graing lobe inhibition of the present invention back) under the systematic parameter among Fig. 8 embodiment

Embodiment

At first, illustrate basic ideas of the present invention in conjunction with accompanying drawing 1 to accompanying drawing 3.

Accompanying drawing 1, accompanying drawing 2, accompanying drawing 3 all are frequency modulation stairstep signal ambiguity function main peak zero Doppler's sectional drawings; Accompanying drawing 1 is the frequency modulation stairstep signal ambiguity function main peak zero Doppler's sectional drawing under the general parameters design; Accompanying drawing 2 is to suppress the fuzzy graing lobe exemplary plot of frequency modulation stairstep signal through Parameters design, and accompanying drawing 3 is that the weighting mismatch filter suppresses the fuzzy graing lobe exemplary plot of frequency modulation stairstep signal.Describe below in conjunction with accompanying drawing 1, accompanying drawing 2,3 pairs of basic ideas of the present invention of accompanying drawing.

Suppose that the initial carrier frequency of frequency step signal is f ₀, the stepping ladder is Δ f, stepping is counted and is that N, pulse repetition time are T _R, pulse repetition rate is PRF, and the subpulse pulsewidth is T, and the subpulse bandwidth is B ₁, the subpulse chirp rate is k=B ₁/ T, the carrier frequency of n sub-pulse are f _n=f ₀+ n Δ f, n=0,1 ..., N-1; The target initial distance is R ₀, target radial speed V _RSI T _g, sampling number is M, imaging window starting point τ _m, the stepping after the interpolation is counted and is N _Zp, every group of IFFT result's extraction count into

The frequency modulation stepping model that transmits:

$S_T\left(t\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{x}_{\mathrm{LFM}}(t-{\mathrm{nT}}_R)\exp \left[\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(f_0+\mathrm{n\&Delta;f})(t-{\mathrm{nT}}_R)\right]---\left(1\right)$

Wherein,

x _LFM(t)＝exp(jπkt ²)rect(t/T) (2)

$\mathrm{rect}\left(\frac{t}{T}\right)=\left\{\begin{array}{c}1,\left|t\right|\&le;T/2\\ 0,\mathrm{others}\end{array}\right.----\left(3\right)$

The expression formula of frequency modulation stairstep signal ambiguity function main peak zero Doppler's tangent plane is following:

$\left|R\left(\mathrm{\&tau;}\right)\right|=|1-\frac{\left|\mathrm{\&tau;}\right|}{T}|\left|\sin c\right[{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">B</figure-callout>}}_1\mathrm{\&tau;}(1-\frac{\left|\mathrm{\&tau;}\right|}{T})\left]\right|\left|\frac{\sin \left(\mathrm{N\&pi;\&tau;\&Delta;f}\right)}{N\sin \left(\mathrm{\&pi;\&tau;\&Delta;f}\right)}\right|---\left(4\right)$

Wherein, τ is the relative time delay between two targets.First is produced by the rectangle envelope in the formula (4), and second is produced by the linear frequency modulation item, and the 3rd produced by the frequency steps income.Preceding two produce envelope modulation to final ambiguity function result, and the 3rd cause graing lobe, and the graing lobe position appears at:

${\mathrm{\&tau;}}_n=\frac{n}{\mathrm{\&Delta;f}},n=\&PlusMinus;1,\&PlusMinus;2,K,\mathrm{int}\left[\mathrm{T\&Delta;f}\right]---\left(5\right)$

General parameters design frequency modulation stairstep signal ambiguity function main peak down zero Doppler's sectional drawing is shown in accompanying drawing 1, and its left figure is three a exploded view (promptly respectively three being drawn among the figure) in the formula (4), and right figure solid line has provided final fuzzy graph result.

A kind of basic ideas that existing method suppresses the fuzzy graing lobe of frequency modulation stairstep signal are: wide T, stepped intervals Δ f, subpulse bandwidth B during through the adjustment subpulse ₁The triadic relation is with the zero setting of graing lobe position or make it less than a less numerical value, shown in accompanying drawing 2.But this requires three in the formula (4) to guarantee strict position relation; Therefore need higher sampling rate (being generally more than 10 times of subpulse bandwidth) to suppress effect in the time of in applying to imaging with the graing lobe that reaches expectation; This makes the Project Realization cost too big, and impracticable.Another kind of existing method certain non-linear rule of giving chapter and verse changes different interpulse number of frequency steps breaking stepping item time cycle property in the formula (4), thereby the graing lobe of realizing the frequency step signal suppresses, but this method realizes that too complicacy is difficult to practical application.

Can find out very intuitively that by accompanying drawing 1 it (is B that the stepping item graing lobe in assurance formula (4) does not fall into frequency modulation item main lobe ₁＞Δ f) under the prerequisite, as long as just can force down the graing lobe that the secondary lobe of frequency modulation item can effectively suppress the one-dimensional image result, and need not guarantee strict position relation (not needing high sampling rate).Based on above-mentioned thought, the basic ideas that the present invention suppresses the fuzzy graing lobe of frequency modulation stairstep signal are: force down the middle frequency modulation subpulse pulse pressure of formula (4) secondary lobe as a result through the weighting mismatch filter, and then final blanketing frequency stairstep signal synthesizes high-resolution imaging graing lobe as a result.Be the above-mentioned thought of intuitivism apprehension more, accompanying drawing 3 provides one group of simulation result under the parameter.

Secondly, illustrate practical implementation step of the present invention in conjunction with accompanying drawing 4 to accompanying drawing 8.

Accompanying drawing 4 is the present invention's actual signal Processing general diagrams of implementing on engineering, and accompanying drawing 5, accompanying drawing 6, accompanying drawing 7 are the concrete realization refinement block diagram of accompanying drawing 4, and accompanying drawing 8 is that the measured data high resolution picture graing lobe under the systematic parameter suppresses figure as a result in the present embodiment.With reference to accompanying drawing, the present invention is carried out detailed description.

As shown in Figure 4; Algorithm of the present invention is input with frequency modulation stairstep signal video echo; Successively pass through: fast time dimension weighting mismatch filter processing, slow time dimension synthon distance images are handled, are synthesized omnidistance one-dimensional range profile and handle 3 big steps, finally obtain low graing lobe whole process one-dimensional range profile.Step by step principle of the present invention and implementation method are described below below:

Step S101, slow time dimension carry out the weighting mismatch filter to the video echo to be handled.

Radar transmitter is launched one group of frequency modulation step-by-step impulse string signal, and this signal is behind target reflection, and being transmitted relatively postpones to be the echoed signal of τ (t), and this echoed signal and coherent local oscillation signal are carried out down-converted, obtains the video echo.

Suppose that the image-forming range window is [R _m, R _m+ Δ R], the imaging time window corresponding with it is [τ _m, τ _m+ Δ τ], R wherein _mBe initial distance, Δ R is imaging window size, τ _m=2R _m/ c, Δ τ=2 Δ R/c; The coarse resolution unit is δ R _g=cT _g/ 2.

Each PRT the imaging window in SI T _gEchoed signal is sampled, and the distance corresponding apart from the different mining sampling point in the window is R _k=R _m+ k δ R _g, wherein, k=0,1 ..., M-1 and M=int (Δ R/ δ R _g), int () representative rounds operation.The every frame rate stairstep signal in sampling back forms N * M dimension echo matrix.Respectively the echoed signal of N different PRT being done the weighting mismatch filter in (on the sampling dimension) on the fast time dimension handles.

Below in conjunction with Fig. 5 the concrete realization flow of this step is described.

Step S201, the video echo expression formula that after down-converted, can be got the frequency modulation stairstep signal by formula (1) is following:

$S_R(t,{\mathrm{nT}}_R)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{x}_{\mathrm{LFM}}(t-\mathrm{\&tau;}\left(t\right)-{\mathrm{nT}}_R)\exp \left[\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;n\&Delta;f}(t-\mathrm{\&tau;}\left(t\right)-{\mathrm{nT}}_R)\right]\exp [-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="HDA0000145061120000011.png,HDA0000145061120000012.png"\; state="\{\{state\}\}">f</figure-callout>}}_0\mathrm{\&tau;}\left(t\right)]\exp \left[\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{dn}}t\right]---\left(6\right)$

Wherein, τ (t) and corresponding f _nDoppler frequency f _DnBe respectively:

$\mathrm{\&tau;}\left(t\right)=\frac{2R\left(t\right)}{c}\&ap;\frac{2R_0}{c}+\frac{2V_{R}t}{c}={\mathrm{\&tau;}}_0+\frac{2V_{R}t}{c}---\left(7\right)$

$f_{\mathrm{dn}}=-\frac{2V_R}{c}(f_0+\mathrm{n\&Delta;f})---\left(8\right)$

Work as V _RDuring＜＜c, formula (8) but abbreviation be:

$f_{\mathrm{dn}}\&ap;f_d=-\frac{2V_R}{c}{f}_0---\left(9\right)$

f _dBe corresponding f ₀Doppler frequency.

Step S202 does Fast Fourier Transform (FFT) (FFT) to the echoed signal of N different PRT respectively in arteries and veins.

Step S203, it is following that the reference signal of n PRT weighting mismatch filter processing is expressed formula:

$S_{\mathrm{Ref}}^0(t,n{T}_R)=x_{\mathrm{LFM}}\left(t\right)\exp \left[\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;n\&Delta;ft}\right]---\left(10\right)$

Step S204, do weighted to the reference signal that the weighting mismatch filter is handled:

S _Ref(t，nT _R)＝x _WLFM(t)exp[j2πnΔft] (11)

Wherein,

x _WLFM(t)=x _LFM(t) * and W (t), W (t) is a weighting function.(12)

The weighting mismatch filter is handled forcing down pulse pressure can make its main lobe broadening and certain peak amplitude loss in the secondary lobe as a result, but can not reduce final auto-correlation result's resolution characteristic.Here emphasis consider after the mismatch filter subpulse pulse pressure as a result the main lobe broadening to the influence of frequency step signal graing lobe.When the main lobe behind the broadening exceeded 1/ Δ f, first graing lobe of stepping item fell in the main lobe of frequency modulation item, and not only can not effectively force down graing lobe this moment, can cause graing lobe to raise sometimes on the contrary.Graing lobe suppresses effect in order to obtain preferably; The graing lobe that should guarantee the stepping item during parameter designing does not fall in first secondary lobe of frequency modulation item after the weighting mismatch filter; Here also reserved the allowance of a graing lobe position, therefore, chosen and parameter Δ f, B at weighting function W (t) ₁The design consideration of should compromising abides by the principle it:

$\frac{1}{\mathrm{\&Delta;f}}\&GreaterEqual;\frac{1}{B_1}(K+1)---\left(13\right)$

Wherein, the weighting function that K chooses when being the weighting mismatch filter is with respect to the main lobe ceofficient of spread of rectangular window, i.e. K=τ ₂/ τ ₁(τ ₁Be rectangular window main lobe width, τ ₂Main lobe width for selected weighting function).Weighting function can use window function usually, and weighting function confirms that back K value is definite.In reality, the weighting function that formula (13) is limited is chosen and the parameter designing principle is to guarantee a finally very important criterion of the graing lobe inhibition effect of synthetic high resolution picture of the present invention.

Step S205 is FFT to the reference signal after the weighted in arteries and veins.

Step S206, S205 result gets conjugation to step.

Step S207, with step S206 result respectively with the arteries and veins of each PRT echoed signal of step S202 in FFT result multiply each other.

Step S208 does Fast Fourier Transform Inverse (FFTI) (IFFT) respectively with each PRT result of step S207 in arteries and veins, expression formula is following behind the IFFT:

(14)

Wherein,

$x_{\mathrm{UMF}}(t-{\mathrm{\&tau;}}_0-{\mathrm{nT}}_R,f_{\mathrm{dn}})=\left[x_{\mathrm{LFM}}(t-{\mathrm{\&tau;}}_0-n{T}_R)\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA0000145061120000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{dn}}(t-{\mathrm{\&tau;}}_0-{\mathrm{nT}}_R)\right)\right]\&CircleTimes;{x^{*}}_{\mathrm{WLFM}}(-t)---\left(15\right)$

x _UMF(t-τ ₀-nT _R, f _Dn) be the linear frequency modulation subpulse weighting mismatch filter result of frequency modulation stairstep signal.

The existing formula that formula (14) is provided becomes discrete form.Note t=t _k=kT _g+ nT _R+ τ _mSubstitution formula (14) is also put in order:

(16)

k＝0，1，2，...，M-1；n＝0，1，2，...，N-1；

Wherein, A=exp [j2 π f ₀τ ₀] exp [j2 π f _dτ ₀].Work as V _RN/ (PRF δ _R)＜2 o'clock, formula (14) is reduced to:

Through above eight steps, just accomplished the weighting mismatch filter of frequency modulation stairstep signal video echo and handled.

Step S102 carries out slow time dimension synthon distance images to weighting mismatch filter result and handles.

Below in conjunction with Fig. 6 the concrete realization flow of this step is described.

Step S301, the vector that is N to M length forming after the weighting mismatch filter zero is interpolated into N respectively _ZpThe point.When parameter designing, must guarantee N _ZpΔ f is f _s=1/T _gIntegral multiple, otherwise can cause final extraction result incorrect, thereby can not destroy the signal inner structure relation that frequency modulation stairstep signal ambiguity function is limited when guaranteeing synthetic high resolution picture.

Step S302 is N to M length after zero interpolation _ZpVector on slow time dimension, be IFFT respectively and handling, obtaining M is δ R apart from length _cThe sub-distance images of=c/2 Δ f, sub-distance images is centered close to R _kAnd its minimum resolution element is δ r=c/ (2N _ZpΔ f).In order to guarantee not occur between adjacent sub-distance images must guaranteeing δ R during parameter designing apart from the space _c＞δ R _g, i.e. T _g＜1/ Δ f.Expression formula after IFFT handles is:

(18)

Through above two steps, just accomplished the slow time dimension synthon of frequency modulation stairstep signal distance images and handled.

Step S103, the antithetical phrase distance images is synthesized omnidistance one-dimensional range profile and is handled.

Below in conjunction with Fig. 7 the concrete realization flow of this step is described.

Step S401 gives up sub-distance images middle distance section [δ R _g/ 2+R _k, δ R _g/ 2+R _k] with exterior portions, in the promptly only sub-distance images high-resolution spectral line with R _kFor the center

Individual, thus realize extracting as the center with the target physical location, wherein

Be the high-resolution spectral line number of single sampled point representative apart from correspondence.Finally, the high-resolution spectral line that is extracted in each sub-distance images is positioned at R _k+ p δ r place,

Make that the extraction result of different sub distance images can be not overlapping, thereby guarantee that the present invention can not destroy the signal inner structure relation that frequency modulation stairstep signal ambiguity function is limited when synthesizing high resolution picture.

Extracting the back expression formula does

${N^{\left(c\right)}}_{\mathrm{zp}}=T_g{N}_{\mathrm{zp}}\mathrm{\&Delta;f}$

Step S402 splices the extraction result of different sub distance images in order, and carries out modulo operation and just obtained final omnidistance one-dimensional range profile, and its expression formula is following:

$p_r\left(\frac{l}{\mathrm{\&Delta;f}{N}_{\mathrm{zp}}}\right)=\underset{k=0}{\overset{M-1}{\mathrm{\&Sigma;}}}\left|x_{\mathrm{UMF}}({\mathrm{kT}}_g-{\mathrm{\&tau;}}_0+{\mathrm{\&tau;}}_m,f_d)\right|$

$\&times;\left|\frac{\sin \left(\mathrm{\&pi;N\&Delta;f}(\frac{l-{\mathrm{kN}}_{\mathrm{zp}}^{\left(c\right)}}{\mathrm{\&Delta;}{\mathrm{fN}}_{\mathrm{zp}}}+({\mathrm{kT}}_g+{\mathrm{\&tau;}}_m-{\mathrm{\&tau;}}_0)+\frac{f_d{T}_R}{\mathrm{\&Delta;f}})\right)}{\sin \left(\mathrm{\&pi;\&Delta;f}(\frac{l-N_{\mathrm{zp}}^{\left(c\right)}}{\mathrm{\&Delta;f}{N}_{\mathrm{zp}}}+({\mathrm{kT}}_g+{\mathrm{\&tau;}}_m-{\mathrm{\&tau;}}_0)+\frac{f_d{T}_R}{\mathrm{\&Delta;f}})\right)}\right|\&times;{W^{\left(c\right)}}_{N_{\mathrm{zp}}}(l-{\mathrm{kN}}_{\mathrm{zp}}^{\left(c\right)})---\left(20\right)$

$\frac{N_{\mathrm{zp}}^{\left(c\right)}}{2}\&le;l\&le;\frac{N_{\mathrm{zp}}^{\left(c\right)}}{2}-1+(M-1)N_{\mathrm{zp}}^{\left(c\right)}$ $N_{\mathrm{zp}}^{\left(c\right)}=T_g{N}_{\mathrm{zp}}\mathrm{\&Delta;f}$

Through above two steps, just accomplished the synthetic omnidistance one-dimensional range profile of frequency modulation stairstep signal and handled, thereby entire process flow process of the present invention finishes.

Just can obtain the synthetic high resolution picture of ultralow time graing lobe through above three big steps to the synthetic high resolution processing of linear frequency modulation stairstep signal video echo, this moment, time graing lobe the influence that follow-up signal is handled of frequency step signal can be ignored basically.This just can effectively eliminate range ambiguity, the target occlusion that frequency step signal time graing lobe brings, and promotes the imaging of frequency step signal greatly and detects performance, and then promote succeeding target tracking performance and recognition effect.

Accompanying drawing 8 is that a rest point target measured data high resolution picture graing lobe of the foregoing description suppresses figure as a result, and left side figure is conventional synthetic high resolution algorithm imaging results, and right figure is the synthetic high resolution algorithm imaging results of the present invention, and its systematic parameter is following: 20120320

Table 1 system emulation parameter

Above-described specific descriptions; Purpose, technical scheme and beneficial effect to invention have carried out further explain, and institute it should be understood that the above is merely specific embodiment of the present invention; And be not used in qualification protection scope of the present invention; All within spirit of the present invention and principle, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (4)

1. the synthetic high resolution picture graing lobe inhibition method of frequency modulation stairstep signal is characterized in that it specifically comprises the steps:

1) echoed signal of the frequency modulation stairstep signal after the sample varianceization being carried out the weighting mismatch filter at fast time dimension handles; Said weighting mismatch filter is handled the weighting function that is adopted and is satisfied following condition:

$\frac{1}{\mathrm{\&Delta;f}}\&GreaterEqual;\frac{1}{B_1}(K+1)$

Wherein, Δ f is the stepped intervals of frequency modulation stairstep signal, B ₁Be the subpulse bandwidth of frequency modulation stairstep signal, K is the main lobe ceofficient of spread of said weighting function with respect to rectangular window;

2) the weighting mismatch filter is handled the back result and carry out the processing of synthon distance images at slow time dimension;

3) the antithetical phrase distance images is synthesized omnidistance one-dimensional range profile processing.

2. the method for claim 1 is characterized in that, said step 2) specifically comprise:

Step S301: result after the weighting mismatch filter is carried out zero interpolation processing at slow time dimension; Points N after the assurance interpolation when parameter designing _ZpWith the two product of stepped intervals Δ f of frequency modulation stairstep signal be the integral multiple of systematic sampling rate;

Step S302 is IFFT to the signal after zero interpolation and handles on slow time dimension, obtain the sub-distance images on the different mining sampling point.

3. method as claimed in claim 2 is characterized in that, it is δ R apart from length that step S302 carries out obtaining M after IFFT handles _cThe sub-distance images of=c/2 Δ f, sub-distance images is centered close to R _kSatisfy δ R during parameter designing _c＞δ R _gCondition;

Wherein, δ R _g=cT _g/ 2 for carrying out the fast time dimension coarse resolution unit when handling, T _gBe the SI of frequency modulation stairstep signal, c is the light velocity; M is the sampling number of frequency modulation stairstep signal; R _k=R _m+ k δ R _gBe k distance that sampled point is corresponding in the image-forming range window, R _mBe image-forming range window reference position.

4. method as claimed in claim 3 is characterized in that, said step 3) specifically comprises:

Step S401: give up sub-distance images middle distance section [δ R _g/ 2+R _k, δ R _g/ 2+R _k] with exterior portions, only extract in the sub-distance images high-resolution spectral line with R _kFor the center

Individual, wherein

Be the high-resolution spectral line number of single sampled point representative apart from correspondence;

Step S402: the extraction result of different sub distance images is spliced in order and carried out modulo operation, obtain omnidistance one-dimensional range profile.

Images