CN102135612B - Bistatic forward-looking synthetic aperture radar swath range calculation method - Google Patents

Abstract

The invention discloses a bistatic forward-looking synthetic aperture radar swath range calculation method, which comprises the following steps: determining an imageable and non-imageable boundary in a bistatic forward-looking SAR (synthetic aperture radar) forward-looking region according to the bistatic forward-looking SAR resolution theory, simultaneously calculating the range of an imaging swath of a system under non-fuzzy conditions by adopting the fuzzy theory and combining with the specificity of bistatic forward-looking SAR beam irradiation, comparing swath range calculation results obtained by the resolution theory and the fuzzy theory, taking an intersection set of the two, and finally getting the bistatic forward-looking SAR swath range. In the method, not only the fuzzy limitation of SAR imaging to swath width is considered, but also the specificity of receiving beam forward-looking of bistatic forward-looking SAR is considered. The method can be applied in high-resolution earth observation, autonomous navigation and other fields, and used for design of the bistatic forward-looking SAR system and configuration of a geometric structure.

Description

A kind of bistatic forward sight synthetic-aperture radar mapping band range computation method

Technical field

The invention belongs to the Radar Signal Processing processing technology field, relate in particular to the mapping band range computation method of bistatic forward sight synthetic-aperture radar (SAR, Synthetic Aperture Radar).

Background technology

Compare with optical sensor, it is strong that synthetic-aperture radar has penetrability, and the distinct advantages of ability round-the-clock, all weather operations is widely used at present.Double-base SAR is a kind of new radar system; System cell site and receiving station are placed on the different platform; The characteristics of bistatic make it possess many outstanding advantages and characteristics, as obtain that target information is abundant, operating distance is far away, security good, antijamming capability is strong etc.

Bistatic Forward-looking SAR is meant that the transmitting-receiving wave beam points to the double-base SAR system on motion ground, receiving station the place ahead jointly.Because bistatic, the cell site can be receiving station provides the orientation to synthetic aperture, forms the orientation to high-resolution, forms distance to high-resolution through launching big bandwidth signal, and therefore bistatic Forward-looking SAR can realize receiving station's forward sight high-resolution imaging.Bistatic Forward-looking SAR can overcome the defective that traditional SAR technology can not realize the high resolution radar imaging of aircraft dead ahead; Make the aircraft of formation flight possess the ability of forward sight imaging, thereby can be applied to fields such as the earth observation of aircraft forward sight, independent navigation, independent landing, cargo assault.

Mapping band scope is important notion of radar imagery and earth observation field and system index, also is called as irradiation width and sweep length, and its decision systems is in the imageable areas scope on ground.At present to single base SAR and bistatic side-looking SAR, mapping band scope adopts system ambiguous theory to confirm usually, and visible document " is protected polished; Xing Mengdao, Wang Tong, " radar imagery is technological "; Electronic Industry Press, 2006 ", " John C.Curlander, Robert N.Mcdonough; " synthetic-aperture radar-system and signal Processing ", Electronic Industry Press, 2006 "; Signal in promptly mapping is with does not exist fuzzy on the distance and bearing both direction, thereby can obtain system's mapping band scope by system's pulse repetition rate restriction.But in bistatic Forward-looking SAR, received beam points to the dead ahead of receiving station's motion, and the target in this zone also not all has imaging capability.So can not only confirm the mapping band scope of bistatic Forward-looking SAR by fuzzy theory.

Summary of the invention

The objective of the invention is in order to solve the problem that existing method exists when confirming the mapping band scope of bistatic Forward-looking SAR, proposed a kind of bistatic forward sight synthetic-aperture radar mapping band range computation method.

Describe content of the present invention for ease, at first following term made an explanation:

Term 1: synthetic aperture radar (SAR)

Synthetic-aperture radar is installed in the space on the motion platform usually; In distance to the long-pending signal of wide bandwidth obtains high resolution when big through launching; In the orientation to travelling forward through radar; Produce the long array antenna of an equivalence, reach the purpose of wave beam sharpening, thus the raising orientation to angular resolution.

Term 2: double-base SAR (Bistatic SAR)

Double-base SAR is meant the SAR system on the different platform that is placed in of system cell site and receiving station, and wherein having a platform at least is motion platform, at the conceptive bistatic radar that belongs to.

Term 3: bistatic Forward-looking SAR (Forward-looking bistatic SAR)

Bistatic Forward-looking SAR is meant that the transmitting-receiving wave beam points to the double-base SAR system on motion ground, receiving station the place ahead jointly.Because bistatic; Traditional SAR technology that can overcome double-base SAR can not realize the defective of aircraft dead ahead high resolution radar imaging; Make the aircraft of formation flight possess the ability of forward sight imaging, thereby can be applied to fields such as the earth observation of aircraft forward sight, independent navigation, independent landing, cargo assault.

Term 4: double-base SAR gradient resolution is theoretical

Gradient resolution theory is used for researching and analysing the resolution characteristic of synthetic-aperture radar, the gradient decision range resolution of system's time delay, the gradient decision azimuthal resolution of Doppler frequency.

Term 5:SAR fuzzy theory

In the SAR imaging technique, lower pulse repetition rate (PRF, Pulse Repetition Frequency) can cause the aliasing of orientation to frequency spectrum, produces azimuth ambiguity, make the orientation to ambiguity levels improve.Higher PRF will reduce the interpulse duration, make in time to produce between received pulse to overlap, and produce range ambiguity.So PRF need consider the restriction that azimuth-range is fuzzy simultaneously.

Term 6: mapping band

The mapping band is to cover parallel with the platform motion direction on the ground ribbon zone, and decision systems is in the imageable areas scope on ground.Among the single base SAR of tradition, mapping band and distance be to vertical, and mapping band scope is determined on the ground distribution width by the antenna beam distance.When system design, for fear of range ambiguity, the mapping band is limited by the size of PRF.

A kind of bistatic forward sight synthetic-aperture radar mapping band range computation method of the present invention specifically comprises the steps:

S1. initialization system parameter, system coordinate system is a true origin with the imaging center impact point, and platform moves along the y axle, and the x axle is for cutting the flight path direction, and the z axle is the vertical ground direction, the initialization system parameter comprises: cell site zero is the position constantly, is designated as (x _0T, y _0T, z _0T); Receiving station zero is the position constantly, be designated as (0, y _0R, z _0R); System's carrier frequency is designated as f ₀Wavelength is designated as λ; Transmitted signal bandwidth is designated as B _rPlatform motion speed is designated as V; Fast time variable is designated as τ; Slow time variable is designated as s; Antenna angle of squint, cell site is designated as θ _STReceiving station's antenna downwards angle of visibility is designated as θ _DRCell site's antenna elevation angle is φ _TCenter, cell site oblique distance is designated as r _0TReceiving station's center oblique distance is designated as r _0RPulse repetition rate is designated as PRF; Pulsewidth is designated as T _rRange resolution is designated as ρ _rAzimuthal resolution is designated as ρ _aThe synthetic aperture time, be designated as T _sThen cell site's distance does $R_T\left(s\right)=\sqrt{r_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2s"\; label="V"\; filenames="HDA0000041384320000022.png"\; state="\{\{state\}\}">V</figure-callout>}}^2{s}^2-2r_{0T}\mathrm{Vs}\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}};$ Receiving station's distance does $R_R\left(s\right)=\sqrt{r_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2s"\; label="V"\; filenames="HDA0000041384320000022.png"\; state="\{\{state\}\}">V</figure-callout>}}^2{s}^2-2r_{0R}\mathrm{Vs}\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}};$ Bistatic Forward-looking SAR System distance is R _Bi(s)=R _T(s)+R _R(s);

S2. adopt gradient theory to calculate the resolution direction of each point on the imaging region x axle, weigh the resolution direction with the tangent value of the angle of resolution and x axle, obtain the resolution direction of any impact point P (x, 0) on the x axle, the result is following:

The range resolution direction does $\mathrm{Dir}\left({\mathrm{\&rho;}}_r\right)=\frac{\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)+\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}\left(x\right)}{x/r_{0R}\left(x\right)+\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)\mathrm{Sin}{\mathrm{\&phi;}}_T\left(x\right)}$

The azimuthal resolution direction is:

$\mathrm{dir}\left({\mathrm{\&rho;}}_a\right)=\frac{r_{0T}\left(x\right){\sin }^2{\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)+r_{0R}\left(x\right){\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}{r_{0T}\left(x\right)x\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)/r_{0R}\left(x\right)+r_{0R}\left(x\right)\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right)\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}$

Wherein $r_{0R}\left(x\right)=\sqrt{r_{0R}^2\left(0\right)+x^2},$ $r_{0T}\left(x\right)=\sqrt{r_{0T}^2\left(0\right)+x^2-2r_{0T}\left(0\right)x\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(0\right)\mathrm{Sin}{\mathrm{\&phi;}}_T},$ ${\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)=a\mathrm{Sin}\left(\frac{r_{0T}\left(0\right)\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(0\right)}{r_{0T}\left(x\right)}\right),$ ${\mathrm{\&theta;}}_{\mathrm{DR}}\left(x\right)=a\mathrm{Cos}\left(\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}\frac{r_{0R}\left(0\right)}{r_{0R}\left(x\right)}\right),$ X representes the coordinate of impact point on the x axle; r _0R(x) receiving station's center oblique distance at expression P (x, 0) some place; r _0T(x) center, the cell site oblique distance at expression P (x, 0) some place; θ _DR(x) receiving station's antenna downwards angle of visibility at expression P (x, 0) some place; θ _ST(x) the antenna angle of squint, cell site at expression P (x, 0) some place, φ _T(x) cell site's antenna elevation angle at expression P (x, 0) some place;

S3. set the accessible resolution corner dimension of bistatic Forward-looking SAR; And find the solution by the definite mapping band scope of this angle; Because the angle between manageable range resolution of SAR imaging algorithm and the azimuthal resolution is limited, establishing this angle is Δ θ, and atan{dir (ρ is then arranged _r)=atan{dir (ρ _a)-Δ θ, the range resolution direction and the azimuthal resolution direction that adopt step S2 to calculate are found the solution this equation, can obtain separating of this equation, are designated as x _Reso, then be: x>=x by the theoretical bistatic Forward-looking SAR mapping band scope of confirming of resolution _Reso

S4. the echo extreme spread width that is allowed by the fuzzy theory computing system is designated as Δ τ=1/PRF-T _r

S5. calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory, specific as follows:

S51. the maximum double base distance that allows of solving system and, minimum bistatic distance and and transmitting-receiving station in relation between the less beam angle.If maximum double base distance and be R _Bix, minor increment and be R _Bin, then echo extreme spread width is: (R _Bix-R _Bin)/c, wherein c is the light velocity, so the minimum and maximum transmitting-receiving station distance that the system of can trying to achieve allows with difference be L=R _Bix-R _Bin=c Δ τ simultaneously, supposes at the forward sight imaging region; Wave beam less in the transmitting-receiving station is covered by bigger wave beam always; And less wave beam footprint is shaped as ellipse, and two semiaxis of this ellipse are parallel with the y axle with the x axle respectively, and semiaxis length is respectively a and b; Because on minimum and maximum bistatic distance and the ellipse that necessarily occurs in than minor beam footprint formation, can calculate minimum transmitting-receiving station distance and be: $R_{\mathrm{Bin}}=\mathrm{Min}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\};$ Maximum transmitting-receiving station distance and be: $R_{\mathrm{Bix}}=\mathrm{Max}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\},$ X wherein, y satisfies

Obtain R _BinAnd R _BixFunction for a and b;

S52. utilize minimum and maximum transmitting-receiving station distance that the system that obtains among the step S51 allows with difference L, calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory, solving equation R _Bix(a; B)-R _Bin(a; B)=L, can obtain confirm under the b condition than the distribution width of minor beam along the x axle, be designated as a (T _r, PRF b), then confirms that by fuzzy theory bistatic Forward-looking SAR mapping band scope is :-a (T _r, PRF, b)≤x≤a (T _r, PRF, b);

S6. calculate bistatic Forward-looking SAR mapping band scope, the mapping band range boundary condition of utilizing step S3 and S52 to calculate can obtain bistatic Forward-looking SAR and survey and draw the band scope and be: max{-a (T _r, PRF, b), x _Reso}≤x≤a (T _r, PRF, b).

Beneficial effect of the present invention: the present invention is theoretical according to bistatic Forward-looking SAR resolution; The boundary of confirming can form images in the bistatic Forward-looking SAR forward vision areas and can not forming images adopts fuzzy theory simultaneously, in conjunction with the singularity of bistatic Forward-looking SAR wave beam irradiation; Computing system is the mapping of the imaging under hazy condition band scope not; The mapping band range computation result that relatively resolution is theoretical and fuzzy theory obtains gets the common factor of the two, can obtain the mapping band scope of bistatic Forward-looking SAR.Method of the present invention has not only been considered in the SAR imaging singularity of bistatic Forward-looking SAR received beam forward sight has also been considered in the fuzzy restriction of mapping band scope.Method of the present invention can be applied to fields such as high resolving power earth observation, independent navigation, is used for the design of bistatic Forward-looking SAR System and the configuration of geometry.

Description of drawings

Fig. 1 is a bistatic forward sight synthetic-aperture radar mapping band range computation method flow synoptic diagram of the present invention.

Fig. 2 is the imaging geometry mode chart that the present invention adopts.

Fig. 3 is the systematic parameter figure that adopts in the specific embodiment of the invention.

Fig. 4 is the Doppler's line such as grade and the line of equidistance synoptic diagram of bistatic Forward-looking SAR.

Fig. 5 is the range resolution that obtains in the specific embodiment of the invention and the azimuthal resolution direction change curve with x.

Fig. 6 is the wave beam coverage diagram that adopts in the specific embodiment of the invention.

Fig. 7 is the mapping band scope of being confirmed by fuzzy theory that obtains in the specific embodiment of the invention.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the present invention is done further description.

The schematic flow sheet of bistatic forward sight synthetic-aperture radar mapping band range computation method of the present invention is as shown in Figure 1, and detailed process is following:

S1. initialization system parameter, the imaging geometry mode chart that present embodiment adopts is as shown in Figure 2, and system coordinate system is a true origin with imaging center impact point O, and platform moves along the y axle, and the x axle is for cutting the flight path direction, and the z axle is the vertical ground direction.The initialization system parameter comprises position constantly, cell site zero, is designated as (x _0T, y _0T, z _0T); Receiving station zero is the position constantly, be designated as (0, y _0R, z _0R); System's carrier frequency is designated as f ₀Wavelength is designated as λ; Transmitted signal bandwidth is designated as B _rPlatform motion speed is designated as V; Fast time variable is designated as τ; Slow time variable is designated as s; Antenna angle of squint, cell site is designated as θ _STReceiving station's antenna downwards angle of visibility is designated as θ _DRCell site's antenna elevation angle is φ _TCenter, cell site oblique distance is designated as r _0TReceiving station's center oblique distance is designated as r _0RPulse repetition rate is designated as PRF; Pulsewidth is designated as T _rRange resolution is designated as ρ _rAzimuthal resolution is designated as ρ _aThe synthetic aperture time, be designated as T _sCell site's distance then $R_T\left(s\right)=\sqrt{r_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+V^2{s}^2-2r_{0T}\mathrm{Vs}\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}};$ Receiving station's distance $R_R\left(s\right)=\sqrt{r_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2s"\; label="V"\; filenames="HDA0000041384320000022.png"\; state="\{\{state\}\}">V</figure-callout>}}^2{s}^2-2r_{0R}\mathrm{Vs}\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}};$ Bistatic Forward-looking SAR System distance R _Bi(s)=R _T(s)+R _R(s); The initial value of partial parameters is as shown in Figure 3.

S2. adopt gradient theory to calculate the resolution direction of each point on the imaging region x axle, comprise range resolution and azimuthal resolution, set forth respectively below.

Range resolution: the time-delay of the echo of certain point is on the ground:

${\mathrm{\&tau;}}_d(x,y)=\frac{1}{c}[\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}]$

Line of equidistance is τ _d(x y) is the curve that constant forms on ground.According to gradient theory, can be worth the Grad of line in the hope of these, as follows $\&dtri;{\mathrm{\&tau;}}_d(x,y)=[\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;x}i+\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;y}j+\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;z}k](s/m)$

Wherein

$\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;x}=\frac{x-x_{0T}}{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}}+\frac{x}{\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}}$

$\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;y}=\frac{y-y_{0T}}{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}}+\frac{y-y_{0R}}{\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}}$

$\frac{\&PartialD;{\mathrm{\&tau;}}_d(x,y)}{\&PartialD;z}=\frac{z-z_{0T}}{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}+\frac{z-z_{0R}}{\sqrt{x^2+{(y-y_{0R})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}}$

Make y=0, and remove the z component, obtain

${\mathrm{\&rho;}}_r\left(x\right)=\frac{1/B_r}{\sqrt{{(\frac{x-x_{0T}}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}+\frac{x-x_{0R}}{\sqrt{{(x-x_{0R})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0R}^2}})}^2+{(\frac{y_{0T}}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}+\frac{y_{0R}}{\sqrt{x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0R}^2}})}^2}}$

And have $\frac{x-x_{0T}}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}=\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)\mathrm{Sin}{\mathrm{\&phi;}}_T\left(x\right),$ $\frac{x}{\sqrt{x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}}=x/r_{0R}\left(x\right),$ $\frac{y_{0T}}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}=\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right),$ $\frac{y_{0R}}{\sqrt{x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}}=\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}\left(x\right).$

So the range resolution size does

${\mathrm{\&rho;}}_r\left(x\right)=\frac{c/B_r}{\sqrt{{(x/r_{0R}\left(x\right)+\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right))}^2+{(\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)+\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right))}^2}}$

With resolution and x axle clamp angular impulse ρ _rDirection do

$\mathrm{dir}\left({\mathrm{\&rho;}}_r\right)=\frac{\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)+\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)}{x/r_{0R}\left(x\right)+\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right)}$

Azimuthal resolution: the Doppler frequency of certain point is on the ground:

$f_d(x,y)=\frac{V}{\mathrm{\&lambda;}}\frac{y-y_{0R}}{\sqrt{x^2+{(y-y_{0R})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}}+\frac{V}{\mathrm{\&lambda;}}\frac{y-y_{0T}}{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}$

These Doppler's lines arbitrfary point (x, 0,0) gradient expression formula of locating on the ground do

$\&dtri;f_d=\frac{\&PartialD;f_d}{\&PartialD;x}i+\frac{\&PartialD;f_d}{\&PartialD;y}j$

Wherein

$\frac{\&PartialD;f_d}{\&PartialD;x}=\frac{V}{\mathrm{\&lambda;}}\frac{{\mathrm{xy}}_{0R}}{{[x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0R}^2]}^{3/2}}+\frac{V}{\mathrm{\&lambda;}}\frac{(x-x_{0T})y_{0T}}{{[{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0T}^2]}^{3/2}}$

$\frac{\&PartialD;f_d}{\&PartialD;y}=\frac{V}{\mathrm{\&lambda;}}\frac{1}{\sqrt{x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0R}^2}}-\frac{V}{\mathrm{\&lambda;}}\frac{y_{0R}^2}{{[x^2+y_{0\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">R</figure-callout>}}^2+z_{0R}^2]}^{3/2}}$

$+\frac{V}{\mathrm{\&lambda;}}\frac{1}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0T}^2}}-\frac{V}{\mathrm{\&lambda;}}\frac{y_{0T}^2}{{[{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0T}^2]}^{3/2}}$

And $\frac{x-x_{0T}}{\sqrt{{(x-x_{0T})}^2+y_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2+z_{0\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">T</figure-callout>}}^2}}=\mathrm{Sin}{\mathrm{\&phi;}}_T\left(x\right)\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right),$ So azimuthal resolution does

${\mathrm{\&rho;}}_a\left(x\right)=\frac{\mathrm{\&lambda;}/\left({\mathrm{VT}}_s\right)}{\sqrt{{(\frac{x}{r_{0R}^2\left(x\right)}\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)+\frac{1}{r_{0T}\left(x\right)}\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right)\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right))}^2+{(\frac{1}{r_{0R}\left(x\right)}{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)+\frac{1}{r_{0T}\left(x\right)}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right))}^2}}$

With resolution and x axle clamp angular impulse ρ _aDirection do

$\mathrm{dir}\left({\mathrm{\&rho;}}_a\right)=\frac{r_{0T}\left(x\right){\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2{\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)+r_{0R}\left(x\right){\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000041384320000032.png,HDA0000041384320000042.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2{\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}{r_{0T}\left(x\right)x\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)/r_{0R}\left(x\right)+r_{0R}\left(x\right)\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right)\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}$

S3. set the accessible resolution corner dimension of bistatic Forward-looking SAR, and find the solution the mapping band scope of confirming by this angle.

In the present embodiment, setting the accessible resolution corner dimension of bistatic Forward-looking SAR is Δ θ=π/6.Thereby have

Atan{dir (ρ wherein _r) and atan{dir (ρ _a) all be the function of x, through asking curve atan{dir (ρ _r) and atan{dir (ρ _a)-intersection point of π/6, can try to achieve x _ResoCan know that by Fig. 4 along with the increase of x, the direction of range resolution and azimuthal resolution levels off to quadrature, so be: x>=x by the theoretical bistatic Forward-looking SAR mapping band scope of confirming of resolution _Reso

In the present embodiment; Range resolution direction and azimuthal resolution direction are as shown in Figure 5 with the variation of x; Solid line is that each point range resolution direction is with the variation relation of x on the x axle among the figure, and dotted line is that the azimuthal resolution direction of each point on the x axle deducts the variation relation of π/6 backs with x.Article two, the crossing point of line is x _Reso, as can be seen from Figure 5 x _ResoBe-1600m, then by the theoretical mapping band scope of confirming of resolution be x>=-1600m.

S4. the echo extreme spread width that is allowed by the fuzzy theory computing system is designated as Δ τ=1/PRF-T _rIn the present embodiment, Δ τ=80 μ s.

S5. calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory, specific as follows:

S51. the maximum double base distance that allows of solving system and, minimum bistatic distance and and transmitting-receiving station in relation between the less beam angle.In the specific embodiment of the invention, the minimum and maximum transmitting-receiving station distance that the system of can trying to achieve allows with difference be L=R _Bix-R _Bin=c Δ τ=24000m.Simultaneously, suppose at the forward sight imaging region that less wave beam is covered by bigger wave beam always in the transmitting-receiving station, and less wave beam footprint is shaped as ellipse, two semiaxis of this ellipse are parallel with the y axle with the x axle respectively, and semiaxis length is respectively a and b, and is as shown in Figure 6.Because on minimum and maximum bistatic distance and the ellipse that necessarily occurs in than minor beam footprint formation, can calculate minimum transmitting-receiving station distance and be: $R_{\mathrm{Bin}}=\mathrm{Min}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\};$ Maximum transmitting-receiving station distance and be: $R_{\mathrm{Bix}}=\mathrm{Max}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\},$ X wherein, y satisfies

Obtain R _BinAnd R _BixFunction for a and b.

S52. utilize minimum and maximum transmitting-receiving station distance that the system that obtains among the step S51 allows with difference L, calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory.In the present embodiment, through asking curve R _Bix(a) and R _Bin(a)+intersection point of L, can try to achieve confirm under the b condition than the distribution width of minor beam along the x axle, promptly wave beam is cut the flight path width.In the present embodiment, b=15000m can be 19050m in the hope of a from Fig. 7.The mapping band scope of then being confirmed by fuzzy theory is :-19050m≤x≤19050m;

S6. calculate the mapping band scope of bistatic Forward-looking SAR, the mapping band scope of trying to achieve among comparison step S3 and the S52 can be tried to achieve bistatic in the present embodiment Forward-looking SAR and effectively survey and draw the maximum magnitude of band and be :-1600m≤x≤19050m.

Those of ordinary skill in the art will appreciate that embodiment described here is in order to help reader understanding's principle of the present invention, should to be understood that the protection domain of inventing is not limited to such special statement and embodiment.Every making according to foregoing description variously possible be equal to replacement or change, and all is considered to belong to the protection domain of claim of the present invention.

Claims (1)

1. a bistatic forward sight synthetic-aperture radar mapping band range computation method is characterized in that, specifically comprises the steps:

S1. initialization system parameter, system coordinate system is a true origin with the imaging center impact point, and platform moves along the y axle, and the x axle is for cutting the flight path direction, and the z axle is the vertical ground direction, the initialization system parameter comprises: cell site zero is the position constantly, is designated as (x _0T, y _0T, z _0T); Receiving station zero is the position constantly, be designated as (0, y _0R, z _0R); System's carrier frequency is designated as f ₀Wavelength is designated as λ; Transmitted signal bandwidth is designated as B _rPlatform motion speed is designated as V; Fast time variable is designated as τ; Slow time variable is designated as s; Antenna angle of squint, cell site is designated as θ _STReceiving station's antenna downwards angle of visibility is designated as θ _DRCell site's antenna elevation angle is φ _TCenter, cell site oblique distance is designated as r _0TReceiving station's center oblique distance is designated as r _0RPulse repetition rate is designated as PRF; Pulsewidth is designated as T _rRange resolution is designated as ρ _rAzimuthal resolution is designated as ρ _aThe synthetic aperture time, be designated as T _sThen cell site's distance does $R_T\left(s\right)=\sqrt{r_{0T}^2+V^2{s}^2-2r_{0T}\mathrm{Vs}\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}};$ Receiving station's distance does $R_R\left(s\right)=\sqrt{r_{0R}^2+V^2{s}^2-2r_{0R}\mathrm{Vs}\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}};$ Bistatic Forward-looking SAR System distance is R _Bi(s)=R _T(s)+R _R(s);

S2. adopt gradient theory to calculate the resolution direction of each point on the imaging region x axle, weigh the resolution direction with the tangent value of the angle of resolution and x axle, obtain the resolution direction of any impact point P (x, 0) on the x axle, the result is following:

The range resolution direction does $\mathrm{Dir}\left({\mathrm{\&rho;}}_r\right)=\frac{\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)+\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}\left(x\right)}{x/r_{0R}\left(x\right)+\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)\mathrm{Sin}{\mathrm{\&phi;}}_T\left(x\right)}$

The azimuthal resolution direction is:

$\mathrm{dir}\left({\mathrm{\&rho;}}_a\right)=\frac{r_{0T}\left(x\right){\sin }^2{\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)+r_{0R}\left(x\right){\cos }^2{\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}{r_{0T}\left(x\right)x\cos {\mathrm{\&theta;}}_{\mathrm{dR}}\left(x\right)/r_{0R}\left(x\right)+r_{0R}\left(x\right)\sin {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)\sin {\mathrm{\&phi;}}_T\left(x\right)\cos {\mathrm{\&theta;}}_{\mathrm{sT}}\left(x\right)}$

Wherein $r_{0R}\left(x\right)=\sqrt{r_{0R}^2\left(0\right)+x^2},$ $r_{0T}\left(x\right)=\sqrt{r_{0T}^2\left(0\right)+x^2-2r_{0T}\left(0\right)x\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(0\right)\mathrm{Sin}{\mathrm{\&phi;}}_T},$ ${\mathrm{\&theta;}}_{\mathrm{ST}}\left(x\right)=a\mathrm{Sin}\left(\frac{r_{0T}\left(0\right)\mathrm{Sin}{\mathrm{\&theta;}}_{\mathrm{ST}}\left(0\right)}{r_{0T}\left(x\right)}\right),$ ${\mathrm{\&theta;}}_{\mathrm{DR}}\left(x\right)=a\mathrm{Cos}\left(\mathrm{Cos}{\mathrm{\&theta;}}_{\mathrm{DR}}\frac{r_{0R}\left(0\right)}{r_{0R}\left(x\right)}\right),$ X representes the coordinate of impact point on the x axle; r _0R(x) receiving station's center oblique distance at expression P (x, 0) some place; r _0T(x) center, the cell site oblique distance at expression P (x, 0) some place; θ _DR(x) receiving station's antenna downwards angle of visibility at expression P (x, 0) some place; θ _ST(x) the antenna angle of squint, cell site at expression P (x, 0) some place, φ _T(x) cell site's antenna elevation angle at expression P (x, 0) some place;

S3. set the accessible resolution corner dimension of bistatic Forward-looking SAR; And find the solution by the definite mapping band scope of this angle; Because the angle between manageable range resolution of SAR imaging algorithm and the azimuthal resolution is limited, establishing this angle is Δ θ, and atan{dir (ρ is then arranged _r)=atan{dir (ρ _a)-Δ θ, the range resolution direction and the azimuthal resolution direction that adopt step S2 to calculate are found the solution this equation, can obtain separating of this equation, are designated as x _Reso, then be: x>=x by the theoretical bistatic Forward-looking SAR mapping band scope of confirming of resolution _Reso

S4. the echo extreme spread width that is allowed by the fuzzy theory computing system is designated as Δ τ=1/PRF-T _r

S5. calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory, specific as follows:

S51. the maximum double base distance that allows of solving system and, minimum bistatic distance and and transmitting-receiving station in relation between the less beam angle, establish maximum double base distance and be R _Bix, minor increment and be R _Bin, then echo extreme spread width is: (R _Bix-R _Bin)/c, wherein c is the light velocity, so the minimum and maximum transmitting-receiving station distance that the system of can trying to achieve allows with difference be L=R _Bix-R _Bin=c Δ τ simultaneously, supposes at the forward sight imaging region; Wave beam less in the transmitting-receiving station is covered by bigger wave beam always; And less wave beam footprint is shaped as ellipse, and two semiaxis of this ellipse are parallel with the y axle with the x axle respectively, and semiaxis length is respectively a and b; Because on minimum and maximum bistatic distance and the ellipse that necessarily occurs in than minor beam footprint formation, can calculate minimum transmitting-receiving station distance and be: $R_{\mathrm{Bin}}=\mathrm{Min}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\};$ Maximum transmitting-receiving station distance and be: $R_{\mathrm{Bix}}=\mathrm{Max}\{\sqrt{{(x-x_{0T})}^2+{(y-y_{0T})}^2+z_{0T}^2}+\sqrt{x^2+{(y-y_{0R})}^2+z_{0R}^2}\},$ X wherein, y satisfies

Obtain R _BinAnd R _BixFunction for a and b;

S52. utilize minimum and maximum transmitting-receiving station distance that the system that obtains among the step S51 allows with difference L, calculate the bistatic Forward-looking SAR mapping band scope of confirming by fuzzy theory, solving equation R _Bix(a; B)-R _Bin(a; B)=L, can obtain confirm under the b condition than the distribution width of minor beam along the x axle, be designated as a (T _r, PRF b), then confirms that by fuzzy theory bistatic Forward-looking SAR mapping band scope is :-a (T _r, PRF, b)≤x≤a (T _r, PRF, b);

S6. calculate bistatic Forward-looking SAR mapping band scope, the mapping band range boundary condition of utilizing step S3 and S52 to calculate can obtain bistatic Forward-looking SAR and survey and draw the band scope and be: max{-a (T _r, PRF, b), x _Reso}≤x≤a (T _r, PRF, b).

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