CN101907704A - Method for evaluating simulation imaging of multi-mode synthetic aperture radar - Google Patents

Abstract

The invention discloses a method for evaluating the simulation imaging of a multi-mode SAR (Synthetic Aperture Radar), which mainly solves the problems of poor adaptability to different operating modes, complex experiment process and long experiment time in the prior art. The method comprises the following steps of: firstly, selecting an operating mode, inputting the parameters of a radar and the motion parameters of a carrier, loading a simulation scene and setting coordinates; secondly, setting a simulation radar echo signal according to a system environment; thirdly, imaging the radar echo signal to obtain a slant-range image; fourthly, geometrically correcting the slant-range image by using a three-dimensional geometric correction method to obtain a ground-range image; and finally, evaluating the quality of the ground-range image, and feeding back and correcting system parameters according the evaluation results so as to provide a feasible basis for a latter semi-physical simulation experiment. The method is applicable to three operating modes including a side looking mode, a slant looking mode and a scanning mode; only a plurality of parameters need to be input during operation, so that the experiment process can be simplified, the experiment time is saved, and the method can be used in a ground simulation experiment of SAR system design.

Description

Method for evaluating simulation imaging of multi-mode synthetic aperture radar

Technical field:

The invention belongs to the Radar Technology field, relate to imaging simulation, specifically a kind of radar data emulation and image processing method based on the VC6.0 platform.

Background technology:

Synthetic-aperture radar SAR is a kind of technology of utilizing radar echo signal target to be carried out imaging.The distance to, utilize big signal bandwidth to obtain high resolution, in the orientation to, utilize virtual synthetic aperture to obtain high resolution.Through the development of decades, the SAR imaging technique progressively improves, and has been widely applied among the actual system.

The carrier of SAR has forms such as satellite, aircraft and guided missile usually.For the exploitation of SAR system, at the experiment of any carrier all be one expensive high, the heavy construction of complicated operation, especially for some carrier such as guided missile and satellite, its use is disposable, expense is very expensive, is difficult to carry out the full-scale investigation of repeated multiple times, therefore must carry out a large amount of strict ground simulation experiments to guarantee the validity of systemic-function at system design stage.

The experiment of SAR ground simulation comprises computer simulation experiment and two kinds of forms of hardware-in-the-loop simulation experiment.Computer simulation experiment utilizes computer software that the SAR system is carried out emulation, mainly finishes the validation verification to systematic parameter, mode of operation and imaging algorithm.The hardware-in-the-loop simulation experiment utilizes computing machine and the true radar of part to carry out combined experiments, the software emulation radar echo signal uses a computer, adopt true transmitter to give the radar receiving end by cable or in microwave dark room again with this echoed signal playback, receiving end passes to signal processor after with signal sampling, data is carried out imaging handle.

In two kinds of ground simulation experiments, the hardware-in-the-loop simulation experiment be the steps necessary before the full-scale investigation, and computer simulation experiment is the basis of hardware-in-the-loop simulation experiment relatively near true radar working method, is the essential step of verification system design.

In traditional computer simulation experiment, at first in programming process, carry out the setting of systematic parameter, carrier movement track and simulating scenes and the modeling of radar and object space geometric relationship according to the SAR mode of operation by operating personnel, be provided with more than the basis then radar echo signal is carried out emulation, then formulate the imaging algorithm that adapts radar echo signal is carried out imaging processing according to the SAR mode of operation, and imaging results carried out quality assessment, reach the purpose of verification system parameter.The advantage of traditional computer emulation experiment is: emulation mode is comparatively flexible, can be made amendment to program at any time as required by operating personnel; Shortcoming is: the program specific aim is stronger, do not have general applicability to different SAR mode of operations, debug process after the modification of program is comparatively loaded down with trivial details, need devote considerable time and manpower, and the professional of operating personnel had relatively high expectations, need operating personnel that SAR system and used simulated program are very familiar to.

Summary of the invention:

The objective of the invention is to overcome the deficiency of aforementioned calculation machine emulation experiment, proposed a kind of method for evaluating simulation imaging of multi-mode synthetic aperture radar,, simplified experimentation to improve the applicability of computer simulation experiment to different SAR mode of operations, save experimental period, reduce operation easier.

For realizing above purpose, the present invention includes following steps:

(1) select mode of operation, input radar parameter and carrier movement parameter load simulating scenes, the simulating scenes coordinate are set;

(2) determine the simulating scenes scope that each cycle radar beam shines according to the radar mode of operation, point target in this scope is divided into concentric circles by the oblique distance of itself and radar, with the retroreflection coefficient addition of the point target in each concentric circles, construct the signal of all range units:

$s_1=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}\underset{i=1}{\overset{P}{\mathrm{\Σ}}}{\mathrm{\σ}}_i\exp (-j\frac{4\mathrm{\π}}{\mathrm{\λ}}R\left(t_m\right))$

Wherein n is the range unit sequence number, and N is the range unit number, and i is the point target sequence number, and P is the point target number, and σ is the retroreflection coefficient of point target, and λ is the wavelength that transmits, and R represents the oblique distance of point target, t _mBe the slow time,, just can obtain radar echo signal this signal and the convolution that transmits:

$s(\hat{t},t_m)=a_r(\hat{t}-\frac{2R\left(t_m\right)}{c})a_a\left(t_m\right)\exp \left[\mathrm{j\π\γ}{(\hat{t}-\frac{2R\left(t_m\right)}{c})}^2\right]\exp [-j\frac{4\mathrm{\π}}{\mathrm{\λ}}R\left(t_m\right)]$

Wherein

Represent the fast time, c represents the light velocity, a _rBe apart from window function, a _aBe the orientation window function, γ is the frequency modulation rate that transmits;

(3) with radar echo signal

Transform to earlier apart from the frequency domain compensation linear range and walk about, change back to the Doppler center of two-dimensional time-domain compensation space-variant again, then transform to two-dimensional frequency, compensate phase factor, the secondary range pulse pressure factor and the range curvature factor three times, change back to two-dimensional time-domain at last, handle to carrying out Dechirp in the orientation, obtain slant-range image

B wherein _sBe transmitted signal bandwidth, f _aBe signal Doppler frequency, R ₀Be the oblique distance of point target and radar aperture center, sinc is final signal envelope;

(4) pass through

Carry out coordinate transform, with slant-range image

Be expressed as S (R, f _a) form, and to S (R, f _a) use the three-dimensional geometry bearing calibration to carry out geometry correction, obtain distance image G (x, y), wherein x is the coordinate of image in X-axis, y is the coordinate of image in Y-axis;

(5) distance image coordinate and simulating scenes coordinate are compared, make (x to distance image G, y) quality assessment, if the absolute value of the error of distance image coordinate and simulating scenes coordinate surpasses a resolution element, then quality assessment is defective, need carry out feedback modifiers to systematic parameter, and carry out emulation experiment once more, till error is less than a resolution element; Otherwise execution in step (6);

(6) quality assessment is qualified systematic parameter is applied in the hardware-in-the-loop simulation experiment of next stage.

The present invention compared with prior art has the following advantages:

The present invention is because the radar echo signal that has three kinds of different working modes carries out the function that emulation, imaging and three-dimensional geometry are proofreaied and correct, modification and debugging have been avoided in the computer simulation experiment at different working modes, reached the purpose of simplifying experimentation, reduction operation easier, saving experimental period, simultaneously owing to can carry out quality assessment to the distance image, according to quality evaluation result systematic parameter is carried out feedback modifiers, for next step hardware-in-the-loop simulation experiment provides the feasibility foundation.

Description of drawings

Fig. 1 is a general flow chart of the present invention;

Fig. 2 is the sub-process figure of system environments of the present invention when being provided with;

Sub-process figure when Fig. 3 is an emulation radar echo signal of the present invention;

Fig. 4 is that the point target of the present invention when the emulation radar echo signal divided the concentric circles synoptic diagram;

Fig. 5 is the sub-process figure of the present invention to the radar echo signal imaging processing;

Fig. 6 is that the present invention is to slant-range image S (R, f _a) carry out the geometric relationship synoptic diagram of three-dimensional geometry timing;

Fig. 7 is that the present invention is to slant-range image S (R, f _a) carry out the rotation of coordinate synoptic diagram of three-dimensional geometry timing;

Fig. 8 is a simulating scenes synoptic diagram under the positive side-looking pattern in the emulation 1;

Fig. 9 is the distance image that emulation produces under the positive side-looking pattern in the emulation 1;

Figure 10 is a simulating scenes synoptic diagram under the strabismus mode in the emulation 2;

Figure 11 is the distance image that emulation produces under the strabismus mode in the emulation 2;

Figure 12 is a simulating scenes synoptic diagram under the scan pattern in the emulation 3;

Figure 13 is the distance image that emulation produces under the scan pattern in the emulation 3.

Embodiment

With reference to Fig. 1, performing step of the present invention is as follows:

Step 1: system environments setting.

With reference to Fig. 2, being implemented as follows of this step:

(1a) in positive side-looking pattern, strabismus mode and three kinds of operation modes of scan pattern, choose one wantonly as mode of operation according to the system design demand;

(1b) input radar parameter, this parameter comprises: pulse width T _p, wavelength X, transmitted signal bandwidth B, sample frequency F _s, pulse repetition time PRF, angle of squint θ, wave beam azimuth angle theta _a, the wave beam pitching angle theta _r, scanning initial angle β ₁With end of scan angle β ₂, imaging time t;

(1c) input carrier kinematic parameter, it comprises: carrier reference position coordinate and along speed, the acceleration of three of X, Y, Z;

(1d) load simulating scenes;

(1e) the simulating scenes coordinate is set;

Step 2: emulation radar echo signal.

With reference to Fig. 3, being implemented as follows of this step:

(2a) from first recurrence interval, at first determine the range of exposures of this cycle radar beam in simulating scenes;

(2b) oblique distance R (t of all point targets and radar in the calculating range of exposures _m), be shown below

$R\left(t_m\right)\sqrt{x_p^2+y_p^2+H^2-2(x_{x0}{x}_p+v_{y0}{y}_p-v_{z0}H)t_m+(v_{x0}^2+{\mathrm{<figure-callout\; id="0"\; label="v\; y"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">v</figure-callout>}}_y^0+{\mathrm{<figure-callout\; id="0"\; label="v\; z"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">v</figure-callout>}}_z^0-a_x{x}_p-a_x{x}_p-a_y{y}_p+a_{z}H)t_m^2}---1)$

Wherein, t _mBe slow time, ν _X0, ν _Y0, ν _Z0Be respectively carrier speed along three of X, Y, Z when being positioned at the imaging time mid point, α _x, α _y, α _zBe respectively the acceleration of carrier along three of X, Y, Z, H is the height of carrier when being positioned at the imaging time mid point, x _pWith y _pX-axis coordinate and Y-axis coordinate for the point target correspondence;

(2c) calculate oblique distance R (t _m) corresponding distance samples unit number

Wherein,

Be the distance samples element length, c is the light velocity;

(2d) the distance samples unit number n of point target according to its oblique distance correspondence divided by concentric circles, as shown in Figure 4;

(2e) with the retroreflection coefficient addition of the point target in each concentric circles, construct the signal of all range units:

$s_1=\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{i=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_i\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right))---2)$

Wherein, N is the range unit number, and i is the point target sequence number, and P is the point target number, and σ is the retroreflection coefficient of point target, and λ is the wavelength that transmits;

(2f), obtain radar echo signal with this signal and the convolution that transmits:

$s(\hat{t},t_m)=a_r(\hat{t}-\frac{2R\left(t_m\right)}{c})a_a\left(t_m\right)\exp \left[\mathrm{j\&pi;\&gamma;}{(\hat{t}-\frac{2R\left(t_m\right)}{c})}^2\right]\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]---3)$

Wherein

Represent the fast time, c represents the light velocity, a _rBe apart from window function, a _aBe the orientation window function, γ is the frequency modulation rate that transmits;

(2g) with formula 3) described radar echo signal is preserved, and repeating step (2a)～(2f), up to the signals of all recurrence intervals all emulation finish.

Step 3: read radar echo signal

It is carried out imaging processing.

With reference to Fig. 5, being implemented as follows of this step:

(3a) right

Do distance to Fourier transform, obtain the signal after the Fourier transform:

$S(f_r,t_m)=a_r(f_r/\mathrm{\&gamma;})a_a\left(t_m\right)\exp [-\mathrm{j\&pi;}\frac{f_r^2}{\mathrm{\&gamma;}}]\exp [-j\frac{4\mathrm{\&pi;}}{c}R\left(t_m\right)f_r]\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]---4)$

F wherein _rBe frequency of distance;

(3b) with following phase factor and formula 4) shown in signal multiplication, finish linearity walk normal moveout correction and the distance to pulse pressure,

$H_1(f_r,t_m;R_s)=\exp \left[j4\mathrm{\&pi;}\frac{A_s{t}_m}{c}{f}_r\right]\exp \left(\mathrm{j\&pi;}\frac{f_r^2}{\mathrm{\&gamma;}}\right)---5)$

A wherein _sBe the linearity of the scene center rate of walking about,

R _sWhen being positioned at the imaging time mid point and the oblique distance of scene center for carrier,

ν _yBe the component of carrier average velocity ν in Y direction, ν _xBe the component of carrier average velocity ν in X-direction;

Signal after obtaining multiplying each other:

$S_2(f_r,t_m)=a_r(f_r/\mathrm{\&gamma;})a_a\left(t_m\right)\exp [-j\frac{4\mathrm{\&pi;}}{c}(R\left(t_m\right)-A_s{t}_m)f_r]\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]---6)$

(3c) to formula 6) shown in signal do distance to inverse Fourier transform, obtain the signal after the inverse Fourier transform:

$s_1(\hat{t},t_m)=\sin c[\hat{t}-\frac{2(R\left(t_m\right)-A_s{t}_m)}{c}]a_a\left(t_m\right)\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]---7)$

With the oblique distance R (t in the following formula _m) be rewritten as the identical expression formula of precision

Wherein

$A=\frac{-2(v_{x0}-\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}\sin {\mathrm{\&theta;}}_x+v_{y0}\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}\cos {\mathrm{\&theta;}}_x-v_{z0}H)}{2R_0}---8)$

$B=\frac{v_{x0}^2+{\mathrm{<figure-callout\; id="0"\; label="v\; y"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">v</figure-callout>}}_y^0+{\mathrm{<figure-callout\; id="0"\; label="v\; z"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">v</figure-callout>}}_z^0-{\mathrm{\&alpha;}}_x\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}\sin {\mathrm{\&theta;}}_x-{\mathrm{\&alpha;}}_{\mathrm{<figure-callout\; id="0"\; label="y\; R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">y</figure-callout>}}\sqrt{R_{}^{}}\sqrt{{}_0^2-H^2}\cos {\mathrm{\&theta;}}_x+{\mathrm{\&alpha;}}_{z}H}{2{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}$

$-\frac{{(v_{x0}\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}\sin {\mathrm{\&theta;}}_x+v_{y0}\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}{\cos \mathrm{\&theta;}}_x-v_{z0}H)}^2}{2{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^3}$

So, formula 7) in

(A-A wherein _s) t _mMuch smaller than distance samples element length δ _r,, can think it to not influence of signal envelope, so

Then formula 7) can be written as

$s_2(\hat{t},t_m)=\sin c[\hat{t}-\frac{2\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2+2R_{0}B{t}_m^2}}{c}]a_a\left(t_m\right)\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]---10)$

(3d) with formula 10) shown in signal times with minor function:

$H_2(t_m,R_0)=\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}(-v_{x0}\frac{\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}}{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}\sin \mathrm{\&theta;}+v_{y0}\frac{\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2-H^2}}{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}\cos \mathrm{\&theta;}-v_{z0}\frac{H}{R_0})t_m]---11)$

With the Doppler center of compensation space-variant, the signal expression after being compensated is as follows:

$s_3(\hat{t},t_m)=\sin c(\hat{t}-\frac{2\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2+2R_{0}B{t}_m^2}}{c})a_a\left(t_m\right)\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0^2+2R_{0}B{t}_m^2}]---12)$

(3e) to formula 12) shown in signal do two-dimensional Fourier transform, obtain the signal after the conversion:

$S(f_r,f_a)=a_r\left(f_r\right)a_a\left(f_a\right)\exp [-j4\mathrm{\&pi;}{R}_0\sqrt{\frac{{(f_r+f_c)}^2}{c^2}-{\left(\frac{f_a}{2\sqrt{2R_{0}B}}\right)}^2}]---13)$

F wherein _aBe the orientation frequency,

With formula 13) in phase term launch the signal after obtaining launching:

$\begin{array}{c}{S}_1(f_r,f_a)=a_r\left(f_r\right)a_a\left(f_a\right)\exp \left[j{\mathrm{\&phi;}}_0(f_a;R_0)\right]\exp \left[j{\mathrm{\&phi;}}_1(f_a;R_0)f_r\right]\\ \exp \left[j{\mathrm{\&phi;}}_2(f_a;R_0)f_r^2\right]\exp \left[j{\mathrm{\&phi;}}_3(f_a;R_0)f_r^3\right]\end{array}---14)$

Wherein

${\mathrm{\&phi;}}_0(f_a;R_0)=-\frac{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}{\sqrt{2R_{0}B}}\sqrt{{\left(f_{\mathrm{aM}}\right)}^2-f_a^2}$

${\mathrm{\&phi;}}_1(f_a;R_0)=-\frac{4\mathrm{\&pi;}}{\mathrm{<figure-callout\; id="0"\; label="c\; R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">c</figure-callout>}}\frac{R_{}}{}\frac{{}_0}{\sqrt{1-{(f_a/f_{\mathrm{aM}})}^2}}\&ap;-\frac{4\mathrm{\&pi;}}{c}[{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0+\frac{1}{2}{R}_s{(f_a/f_{\mathrm{aM}})}^2]$

${\mathrm{\&phi;}}_2(f_a;R_0)=\mathrm{\&pi;}{R}_B\frac{2\mathrm{\&lambda;}{(f_a/f_{\mathrm{aM}})}^2}{c^2{(1-{(f_a/f_{\mathrm{aM}})}^2)}^{\frac{3}{2}}};---15)$

${\mathrm{\&phi;}}_3(f_a;R_0)=-\frac{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0{\mathrm{\&lambda;}}^2{(f_a/f_{\mathrm{aM}})}^2}{c^3{(1-{(f_a/f_{\mathrm{aM}})}^2)}^{\frac{5}{2}}}$

$f_{\mathrm{aM}}=\frac{2\sqrt{2R_{0}B}}{\mathrm{\&lambda;}}$

(3f) to formula 14) multiply by formula 16 successively) shown in three phase factors, formula 17) shown in the secondary range pulse pressure factor and formula 18) shown in the range curvature factor:

$H_3(t_m;R_0)=\exp [-j{\mathrm{\&phi;}}_3(f_a;R_0)f_r^3]---16)$

$H_4(t_m;R_0)=\exp [-j{\mathrm{\&phi;}}_2(f_a;R_0)f_r^2]\exp \left[\frac{2\mathrm{\&pi;}}{c}{R}_s{(f_a/f_{\mathrm{aM}})}^2{f}_r\right]---17)$

$H_5(t_m;R_0)=\exp \left[\frac{2\mathrm{\&pi;}}{c}{R}_s{(f_a/f_{\mathrm{aM}})}^2{f}_r\right]---18)$

Signal after obtaining multiplying each other:

S ₂(f _r，f _a)＝a _r(f _r)a _a(f _a)exp[jφ ₀(f _a；R ₀)]；19)

(3g) to formula 19) signal do two-dimentional inverse Fourier transform, obtain the signal after the two-dimentional inverse Fourier transform:

$s_4(\hat{t},t_m)=\sin c\left[B_s(\hat{t}-\frac{2R_0}{c})\right]a_a\left(t_m\right)\exp [-j\frac{4\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}{\mathrm{\&lambda;}}]\exp [-j\frac{\mathrm{\&pi;}{f}_{\mathrm{aM}}\sqrt{2R_{0}B}}{R_0}{t_m}^2]---20)$

(3h) to formula 20) signal times with the orientation Dechirp factor shown in the following formula:

$H_6\left(t_m\right)=\exp \left[j\frac{\mathrm{\&pi;}{f}_{\mathrm{aM}}\sqrt{2R_{0}B}}{R_0}{t_m}^2\right]\exp \left[j\frac{4\mathrm{\&pi;}{\mathrm{<figure-callout\; id="0"\; label="R"\; filenames="HSA00000159042300051.png"\; state="\{\{state\}\}">R</figure-callout>}}_0}{\mathrm{\&lambda;}}\right]---21)$

Obtain the signal after Dechirp handles:

$s_5(\hat{t},t_m)=\sin c\left[B_s(\hat{t}-\frac{2R_0}{c})\right]a_a\left(t_m\right)---22)$

(3i) right

Do the orientation to Fourier transform, obtain slant-range image:

$s(\hat{t},f_a)=\sin c\left[B_s(\hat{t}-\frac{2R_0}{c})\right]\sin c\left(f_a\right)---23)$

Step 4: with slant-range image

In every bit be corrected to correct coordinate.

Because slant-range image

Compare with simulating scenes and to have geometric deformation, therefore need proofread and correct slant-range image by three-dimensional geometry

In every bit be corrected to correct coordinate, being implemented as follows of this step:

(4a) pass through

Carry out coordinate transform, with slant-range image

Be expressed as S (R, f _a) form;

(4b) with reference to Fig. 6, to slant-range image S (R, f _a), with its coordinate (R, f _a) obtain corresponding distance rotational coordinates (x ', y ') by following formula:

$\left\{\begin{array}{c}{x}^{\&prime;}=\frac{\mathrm{\&lambda;}{f}_{a}R}{2v\sin }-\mathrm{Hctg\&alpha;}\\ y^{\&prime;}=\sqrt{R^2-H^2-{(\frac{\mathrm{\&lambda;}{f}_{a}R}{2v\sin \mathrm{\&alpha;}}-\mathrm{Hctg\&alpha;})}^2}\end{array}\right.---24)$

Wherein, ν is the average velocity of carrier movement in the imaging disposing time,

ν _XyBe the component of ν in XOY plane, ν _zBe the component of ν in Z-direction;

(4c) with reference to Fig. 7, by following formula with distance rotational coordinates (x ', y ') be converted to the distance coordinate (x, y):

$\left\{\begin{array}{c}x=\mathrm{\&rho;}\cos ({\mathrm{\&epsiv;}}^{\&prime;}+{\mathrm{\&theta;}}_x)\\ y=\mathrm{\&rho;}\sin ({\mathrm{\&epsiv;}}^{\&prime;}+{\mathrm{\&theta;}}_x)\end{array}---25)\right.$

Wherein, $\mathrm{\&rho;}=\sqrt{x^{\&prime;2}+y^{\&prime;2}},$ ${\mathrm{\&epsiv;}}^{\&prime;}={\mathrm{tg}}^{-1}\left(\frac{y^{\&prime;}}{x^{\&prime;}}\right);$

(4d) set up a distance coordinate plane, with slant-range image S (R, f according to the resolution element of system design demand _a) in every bit according to its corresponding distance coordinate (x y) inserts correspondence position on the distance coordinate plane, just obtained distance image G (x, y).

Step 5: to distance image G (x, y) carry out quality assessment, if the absolute value of distance image coordinate and simulating scenes error of coordinate surpasses a resolution element, then quality assessment is defective, need carry out feedback modifiers to systematic parameter, and carry out emulation experiment once more, till error is less than a resolution element; Otherwise execution in step 6.

Step 6: the systematic parameter that quality assessment is qualified is applied in the hardware-in-the-loop simulation experiment of next stage.

Effect of the present invention can further specify by following emulation:

Emulation 1: select positive side-looking pattern to carry out emulation.

Input radar parameter: pulse width T _p=2 μ s, wavelength X=0.0175m, transmitted signal bandwidth B _s=80MHz, sample frequency F _s=100MHz, pulse repetition time PRF=1000Hz, angle of squint θ=0, wave beam azimuth angle theta _a=3 °, wave beam pitching angle theta _r=3 °, scanning initial angle β ₁=30 ° and end of scan angle β ₂=30 °, imaging time t=1.024s.

The input carrier kinematic parameter: carrier reference position coordinate is (0,0,8000), is respectively 120m/s, 5m/s, 3m/s along the speed of three of X, Y, Z, and acceleration is respectively 2m/s ², 0.5n/s ², 1m/s ²

Load simulating scenes.Simulating scenes is the square formation of being made up of nine point targets, as shown in Figure 8.The spacing of point target and point target is 50m, and the simulating scenes coordinate as shown in Table 1.

The distance image that Fig. 9 produces for emulation, its resolution element size is 5m.

Calculate the error of distance image coordinate shown in Figure 9 and simulating scenes coordinate shown in Figure 8 and take absolute value, obtain quality evaluation result as shown in Table 1.As can be seen, the Error Absolute Value of all point targets does not all surpass a resolution element from table one, and quality assessment is qualified.Therefore, prove that the used systematic parameter of this emulation has feasibility, can be applied in the hardware-in-the-loop simulation experiment of next stage.

Simultaneously, in simulation process, because the present invention has the adaptability that aligns the side-looking pattern, operating personnel only need select mode of operation, input parameters and load the operation of simulating scenes, do not need program is made amendment, therefore reached the purpose of simplifying experimentation, reduction operation easier, saving experimental period.

Table one emulation 1 quality evaluation result (unit: m)

Emulation 2: select strabismus mode to carry out emulation.

Input radar parameter: pulse width T _p=5 μ s, wavelength X=0.0175m, transmitted signal bandwidth B _s=100MHz, sample frequency F _s=150MHz, pulse repetition time PRF=1000Hz, angle of squint θ=10 °, wave beam azimuth angle theta _a=5 °, wave beam pitching angle theta _r=5 °, scanning initial angle β ₁=35 ° and end of scan angle β ₂=35 °, imaging time t=1.024s.

The input carrier kinematic parameter: carrier reference position coordinate is (0,0,9000), is respectively 110m/s, 10m/s, 1m/s along the speed of three of X, Y, Z, and acceleration is respectively 0.5m/s ², 1m/s ², 0.5m/s ²

Load simulating scenes.Simulating scenes is the square formation of being made up of nine point targets, as shown in figure 10.The spacing of point target and point target is 50m, and the simulating scenes coordinate as shown in Table 2.

The distance image that Figure 11 produces for emulation, its resolution element size is 5m.

Calculate the error of distance image coordinate shown in Figure 11 and simulating scenes coordinate shown in Figure 10 and take absolute value, obtain quality evaluation result as shown in Table 1.As can be seen, the Error Absolute Value of all point targets does not all surpass a resolution element from table two, and quality assessment is qualified.Therefore, prove that the used systematic parameter of this emulation has feasibility, can be applied in the hardware-in-the-loop simulation experiment of next stage.

Simultaneously, in simulation process, because the present invention has the adaptability to strabismus mode, operating personnel only need select mode of operation, input parameters and load the operation of simulating scenes, do not need program is made amendment, therefore reached the purpose of simplifying experimentation, reduction operation easier, saving experimental period.

Table two emulation 2 quality evaluation result (units: m)

Emulation 3: select the scanning pattern of looking to carry out emulation.

Input radar parameter: pulse width T _p=3 μ s, wavelength X=0.02m, transmitted signal bandwidth B _s=80MHz, sample frequency F _s=100MHz, pulse repetition time PRF=1000Hz, angle of squint θ=0, wave beam azimuth angle theta _a=3 °, wave beam pitching angle theta _r=3 °, scanning initial angle β ₁=20 ° and end of scan angle β ₂=40 °, imaging time t=1.024s.

The input carrier kinematic parameter: carrier reference position coordinate is (0,0,8500), is respectively 120m/s, 5m/s, 3m/s along the speed of three of X, Y, Z, and acceleration is respectively 2m/s ², 1m/s ², 1m/s ²

Load simulating scenes.Simulating scenes is the rectangle battle array of being made up of ten point targets, as shown in figure 12.The spacing of point target and point target is 100m, and simulating scenes as shown in Table 3.

The distance image that Figure 13 produces for emulation, its resolution element size is 5m.

Calculate the error of distance image coordinate shown in Figure 13 and simulating scenes coordinate shown in Figure 12 and take absolute value, obtain quality evaluation result as shown in Table 1.As can be seen, the Error Absolute Value of all point targets does not all surpass a resolution element from table three, and quality assessment is qualified.Therefore, prove that the used systematic parameter of this emulation has feasibility, can be applied in the hardware-in-the-loop simulation experiment of next stage.

Simultaneously, in simulation process, because the present invention has the adaptability to scan pattern, operating personnel only need select mode of operation, input parameters and load the operation of simulating scenes, do not need program is made amendment, therefore reached the purpose of simplifying experimentation, reduction operation easier, saving experimental period.

Table three emulation 3 quality evaluation result (units: m)

Claims (3)

1. synthetic-aperture radar method for evaluating simulation imaging may further comprise the steps:

(1) select mode of operation, input radar parameter and carrier movement parameter load simulating scenes, the simulating scenes coordinate are set;

(2) determine the simulating scenes scope that each cycle radar beam shines according to the radar mode of operation, point target in this scope is divided into concentric circles by the oblique distance of itself and radar, with the retroreflection coefficient addition of the point target in each concentric circles, construct the signal of all range units:

$s_1=\underset{n=1}{\overset{N}{\mathrm{\&Sigma;}}}\underset{i=1}{\overset{P}{\mathrm{\&Sigma;}}}{\mathrm{\&sigma;}}_i\exp (-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right))$

Wherein n is the range unit sequence number, and N is the range unit number, and i is the point target sequence number, and P is the point target number, and σ is the retroreflection coefficient of point target, and λ is the wavelength that transmits, and R represents the oblique distance of point target, t _mBe the slow time,, just can obtain radar echo signal this signal and the convolution that transmits:

$s(\hat{t},t_m)=a_r(\hat{t}-\frac{2R\left(t_m\right)}{c})a_a\left(t_m\right)\exp \left[\mathrm{j\&pi;\&gamma;}{(\hat{t}-\frac{2R\left(t_m\right)}{c})}^2\right]\exp [-j\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}R\left(t_m\right)]$

Wherein

Represent the fast time, c represents the light velocity, a _rBe apart from window function, a _aBe the orientation window function, γ is the frequency modulation rate that transmits;

(3) with radar echo signal

Transform to earlier apart from the frequency domain compensation linear range and walk about, change back to the Doppler center of two-dimensional time-domain compensation space-variant again, then transform to two-dimensional frequency, compensate phase factor, the secondary range pulse pressure factor and the range curvature factor three times, change back to two-dimensional time-domain at last, handle to carrying out Dechirp in the orientation, obtain slant-range image

B wherein _sBe transmitted signal bandwidth, f _aBe signal Doppler frequency, R ₀Be the oblique distance of point target and radar aperture center, sinc is final signal envelope;

(4) pass through

Carry out coordinate transform, with slant-range image

Be expressed as S (R, f _a) form, and to S (R, f _a) use the three-dimensional geometry bearing calibration to carry out geometry correction, obtain distance image G (x, y), wherein x is the coordinate of image in X-axis, y is the coordinate of image in Y-axis;

(5) distance image coordinate and simulating scenes coordinate are compared, make (x to distance image G, y) quality assessment, if the absolute value of distance image coordinate and simulating scenes error of coordinate surpasses a resolution element, then quality assessment is defective, need carry out feedback modifiers to systematic parameter, and carry out emulation experiment once more, till error is less than a resolution element; Otherwise execution in step (6);

(6) quality assessment is qualified systematic parameter is applied in the hardware-in-the-loop simulation experiment of next stage.

2. method for evaluating simulation imaging of multi-mode synthetic aperture radar according to claim 1, wherein in the described selection mode of operation of step (1), be in positive side-looking pattern, strabismus mode and three kinds of mode of operations of scan pattern, according to the optional one of system design demand.

3. method for evaluating simulation imaging of multi-mode synthetic aperture radar according to claim 1, wherein step (4) is described to slant-range image S (R, f _a) use the three-dimensional geometry bearing calibration to carry out geometry correction, carry out as follows:

(3a) to slant-range image S (R, f _a), with its coordinate (R, f _a) obtain corresponding distance rotational coordinates (x ', y ') by following formula:

$\left\{\begin{array}{c}{x}^{\&prime;}=\frac{\mathrm{\&lambda;}{f}_{a}R}{2v\sin \mathrm{\&alpha;}}-\mathrm{Hctg\&alpha;}\\ y^{\&prime;}=\sqrt{R^2-H^2-{(\frac{\mathrm{\&lambda;}{f}_{a}R}{2v\sin \mathrm{\&alpha;}}-\mathrm{Hctg\&alpha;})}^2}\end{array}\right.$

Wherein, ν is the average velocity of carrier movement in the imaging disposing time,

ν _XyBe the component of ν in XOY plane, ν _zBe the component of ν in Z-direction, H is the height of carrier when the imaging time mid point;

(3b) by following formula with distance rotational coordinates (x ', y ') be converted to the distance coordinate (x, y):

$\left\{\begin{array}{c}x=\mathrm{\&rho;}\cos ({\mathrm{\&epsiv;}}^{\&prime;}+{\mathrm{\&theta;}}_x)\\ y=\mathrm{\&rho;}\sin ({\mathrm{\&epsiv;}}^{\&prime;}+{\mathrm{\&theta;}}_x)\end{array}\right.$

Wherein,

ν _yBe the component of ν in Y direction, ν _xBe the component of ν in X-direction;

(3c) set up a distance coordinate plane, with slant-range image S (R, f according to the resolution element of system design demand _a) in every bit (x y) inserts correspondence position on the distance coordinate plane according to its corresponding distance coordinate.

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