CN104181529A - Ka-waveband synthetic aperture radar (SAR) signal processing method and device - Google Patents

Abstract

The embodiment of the invention discloses a Ka-waveband SAR signal processing method and device, which can improve accuracy of beam reception directing so that gain loss of signal reception is reduced. The method includes the following steps: in a pitching direction, a plurality of paths of reception antennae receive echo signals respectively and original echo data of the reception antennae are generated; down conversion and distance-direction compression processing are carried out on the original echo data of the reception antennae and then first equivalent echo data of the reception antennae are obtained; the first equivalent data of the reception antennae are moved to the same range gate at a target compression peak value so that second equivalent echo data of the reception antennae are obtained; according to the second equivalent echo data of the reception antennae, a steering vector of the pitching direction is obtained and according to the steering vector of the pitching direction, a target direction of arrival is estimated through a preset DOA estimation algorithm; and according to the target direction of arrival, an echo reception direction is corrected.

Description

A kind of Ka wave band synthetic-aperture radar SAR signal processing method and equipment

Technical field

The present invention relates to Radar Signal Processing Technology, relate in particular to a kind of Ka wave band synthetic-aperture radar (SAR, Synthetic Aperture Radar) signal processing method and equipment.

Background technology

In the available band of radar emission signal, Ka wave band has short wavelength's feature, and this feature makes the SAR antenna of Ka wave band have the plurality of advantages such as volume is little, lightweight; In addition, due to the high feature of short wavelength, frequency of Ka wave band, make radar signal can have very high absolute bandwidth, this just makes the SAR of Ka wave band can reach very high range resolution.

But, due to short wavelength's feature of Ka band signal, it is being rained under environment, attenuation ratio is more serious, thereby has caused Ka wave band receiving gain to reduce, and this has just inevitably determined that Ka wave band need to improve receiving gain by DBF technology.

At present, on the range direction of radar, conventionally utilize hyperchannel scanning to receive (SCORE, Scan-On-Receive) mode, form one and swept to far-end by radar near-end, and the high-gain pencil beam of real-time tracing pulse, make up the loss of gain with this.

But, utilize the mode of SCORE to carry out Radar Signal Processing, be taking the earth as a desirable smooth sphere as supposed premise.But in actual conditions, the earth is a spheroid with Plain, mountain region, hills and basin, and there is the Mountainous Regions of a lot of big rise and falls at earth's surface place.If now still carry out calculating beamforming weight vectors with desirable sphere model, can cause the serious deviation of beam position, cause receiving the gain loss of signal.

As shown in Figure 1, a kind of Ka wave band that it shows the embodiment of the present invention provides utilizes the mode of SCORE to carry out the processing scene of SAR signal, in Fig. 1, on the hillside 4 that real goal 1 is h at the height apart from earth's surface 3, real goal 1 is R with the distance of array antenna 5, array antenna 5 apart from the distance on earth's surface as described in dotted arrow, aperture in array antenna 5 puts in order as shown in dash-dot arrows, and at the foot of the hill there is equally a non-real goal 2 on hillside 4, distance between distance between non-real goal 2 and array antenna 5 and real goal 1 and array antenna 5 is identical, also be R, so, if by SCORE mode, regard the earth as desirable sphere model, and the height relief of not considering earth's surface is carried out signal processing, so, in the time that array antenna 5 receives the echoed signal of real goal 1, can make array antenna 5 is non-real goal 2 according to the beam position forming of echoed signal, thereby real goal 1 is weakened greatly to the echo gain of wave beam.

Summary of the invention

For solving the problems of the technologies described above, the embodiment of the present invention is expected to provide a kind of Ka wave band SAR signal processing method and equipment, can improve the accuracy that received beam points to, thereby reduces the gain loss that receives signal.

Technical scheme of the present invention is achieved in that

First aspect, the embodiment of the present invention provides a kind of Ka wave band SAR signal processing method, and the method can comprise:

Pitching receives respectively echoed signal to multipath reception antenna, and generates the original echo data of each receiving antenna;

The original echo data of described each receiving antenna, by down coversion and apart from after compression is processed, are obtained to the first equivalent echo data of each receiving antenna;

The first equivalent data of described each receiving antenna, in the compression peaks of target is moved same range gate, is obtained to the second equivalent echo data of each receiving antenna;

According to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector, and according to described pitching to steering vector by default direction of arrival DOA algorithm for estimating, the direction of arrival of described target is estimated;

According to the direction of arrival of described target, echo receive direction is revised, made the echo receive direction of described each receiving antenna point to described target.

The implementation possible according to the first, in conjunction with first aspect, described each receiving antenna receives echoed signal, and the original echo data that generate each receiving antenna are as shown in the formula expression:

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent the distance of emitting antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents white Gaussian noise.

The implementation possible according to the second, in conjunction with the possible implementation of the first, described the first equivalent echo data are as shown in the formula expression:

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c, wherein, d is the distance between adjacent receiving antenna, θ is direction and the angle of receiving antenna between the projecting direction on ground transmitting, β _tfor direction and the angle of receiving antenna between the projecting direction on ground of the echoed signal returned by target.

The implementation possible according to the third, in conjunction with the possible implementation of the second, described the second equivalent echo data are shown below:

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e。

According to the 4th kind of possible implementation, in conjunction with the third possible implementation, according to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector, comprising:

To calculate s " _i(τ) be set to τ=τ ₀, obtain the pitching of described each receiving antenna corresponding to described target to signal, the pitching of described each receiving antenna to signal as shown in the formula expression:

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e

Wherein, λ represents that pitching is to the constant component in signal;

Form by from the pitching of all receiving antennas to signal composition vector model, described pitching to the vector model of signal as shown in the formula expression:

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ represent the steering vector of described pitching to signal; for the noise vector of white Gaussian noise.

According to the 5th kind of possible implementation, in conjunction with the 4th kind of possible implementation, according to described pitching to steering vector by default DOA algorithm for estimating, target is carried out to direction of arrival estimation, comprising:

According to described pitching to steering vector by Capon algorithm to described target carry out direction of arrival DOA estimate;

Particularly, according to described pitching to steering vector by Capon algorithm to target carry out direction of arrival DOA estimate comprise:

According to the first calculating formula obtain the covariance matrix R of pitching to the vector model of signal _s; Wherein, E represents expectation computing symbol; H represents conjugate transpose;

According to described pitching to steering vector and described covariance matrix R _sobtain the spatial spectrum function of described pitching to the vector model of signal, wherein, described pitching is shown below to the spatial spectrum function of the vector model of signal:

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

Search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.

Second aspect, the embodiment of the present invention provides a kind of Ka wave band SAR signal handling equipment, it is characterized in that, and described equipment comprises: pitching is to multipath reception unit, multiple signals processing unit, direction of arrival estimation unit and amending unit, wherein,

Described pitching, to multipath reception unit, comprises multipath reception antenna, receives respectively echoed signal for described multipath reception antenna, and generates the original echo data of each receiving antenna;

Multiple signals processing unit, for passing through described pitching down coversion and apart from after compression is processed, can obtain the first equivalent echo data of described each receiving antenna to the original echo data of each receiving antenna of multipath reception unit;

And by the first equivalent data of described each receiving antenna in the compression peaks of target is moved same range gate, can obtain the second equivalent echo data of each receiving antenna;

Direction of arrival estimation unit, for according to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector;

And by pitching to steering vector by default direction of arrival DOA algorithm for estimating, described target is carried out to direction of arrival estimation;

Amending unit, for estimating that according to described direction of arrival estimation unit the direction of arrival of the described target obtaining revises to the echo receive direction of each receiving antenna of multipath reception unit described pitching, make described pitching point to described target to the echo receive direction of each receiving antenna of multipath reception unit.

The implementation possible according to the first, in conjunction with second aspect, described multiple signals processing unit comprises the processing branch road corresponding with described each receiving antenna difference, each processing branch road is followed successively by low noise amplifier LNA, low-converter, A-D converter ADC, Range compress unit, peak value according to the processing sequence of signal and moves unit, wherein

Described LNA is connected to each receiving antenna of multipath reception unit with described pitching, and described peak value is moved unit and is connected with described direction of arrival estimation unit.

The implementation possible according to the second, in conjunction with second aspect or the possible implementation of the first, the original echo data of described each receiving antenna are as shown in the formula expression:

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent the distance of emitting antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents white Gaussian noise.

The implementation possible according to the third, in conjunction with the possible implementation of the second, described the first equivalent echo data are as shown in the formula expression:

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c, wherein, d is the distance between adjacent receiving antenna, θ is direction and the angle of receiving antenna between the projecting direction on ground transmitting, β _tfor direction and the angle of receiving antenna between the projecting direction on ground of the echoed signal returned by target;

Described the second equivalent echo data are shown below:

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e。

According to the 4th kind of possible implementation, in conjunction with the third possible implementation, described direction of arrival estimation unit specifically for:

To calculate s " _i(τ) be set to τ=τ ₀, obtain the pitching of the corresponding each receiving antenna of target to signal, the pitching of described each receiving antenna to signal as shown in the formula expression;

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e

Wherein, λ represents that pitching is to the constant component in signal;

And, the form by the pitching of all receiving antennas to signal composition vector model, described pitching to the vector model of signal as shown in the formula expression:

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ represent the steering vector of described pitching to signal; for the noise vector of white Gaussian noise.

According to the 5th kind of possible implementation, in conjunction with the 4th kind of possible implementation, described direction of arrival estimation unit specifically for:

According to the second calculating formula obtain the covariance matrix R of pitching to the vector model of signal _s; Wherein, E represents expectation computing symbol; H represents conjugate transpose;

And, according to pitching to steering vector and described covariance matrix R _sobtain the spatial spectrum function of pitching to the vector model of signal, wherein, described pitching is to shown in the spatial spectrum function following formula of the vector model of signal:

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

And, search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.

The embodiment of the present invention provides a kind of Ka wave band SAR signal processing method and equipment, target direction of arrival in echoed signal is estimated, and carry out received beam sensing according to the direction of arrival of target, can improve the accuracy that received beam points to, thereby reduce the gain loss that receives signal.

Brief description of the drawings

A kind of Ka wave band that Fig. 1 provides for the embodiment of the present invention utilizes SCORE mode to carry out the processing scene schematic diagram of SAR signal;

The schematic flow sheet of a kind of Ka wave band SAR signal processing method that Fig. 2 provides for the embodiment of the present invention;

The multipath reception antenna alignment structural representation of a kind of Ka wave band SAR that Fig. 3 provides for the embodiment of the present invention;

The structural representation of a kind of Ka wave band SAR signal handling equipment that Fig. 4 provides for the embodiment of the present invention;

The structural representation of a kind of multiple signals processing unit that Fig. 5 provides for the embodiment of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described.

Referring to Fig. 2, it shows the flow process of a kind of Ka wave band SAR signal processing method that the embodiment of the present invention provides, and the method can comprise:

S201: pitching receives respectively echoed signal to multipath reception antenna, and generate the original echo data of each receiving antenna;

For the technical scheme of the embodiment of the present invention is clearly described, referring to Fig. 3, it shows the multipath reception antenna alignment structure of a kind of Ka wave band SAR that the embodiment of the present invention provides, understandably, except the arrangement architecture of the multipath reception antenna shown in Fig. 3, the arrangement architecture of the multipath reception antenna of other Ka wave bands SAR also can be applied the technical scheme of the embodiment of the present invention, and the embodiment of the present invention is not done concrete restriction to this.

In Fig. 3, the pitching of Ka wave band SAR is N evenly distributed receiving antenna to multipath reception antenna, distance between adjacent receiving antenna is d, emitting antenna can be positioned over any one receiving antenna place, and using the receiving antenna at this place as with reference to receiving antenna, in the present embodiment, using first receiving antenna as with reference to receiving antenna, emitting antenna and first receiving antenna are positioned over same position, H so _orbitrepresent the projecting direction of receiving antenna on ground, the direction transmitting is as the R in Fig. 3 _v, R _vvertical with the orientation of receiving antenna, and R _vwith H _orbitbetween angle be θ; R ₁to R _nrepresent that respectively N receiving antenna of first receiving antenna to the receives the direction of the echoed signal of being returned by target, because target is to the distance of each receiving antenna much larger than the distance between receiving antenna, therefore, target can be far field target, according to far-field effect, and R ₁to R _nbetween parallel to each other, and R ₁to R _nwith H _orbitbetween angle be β _t;

So as shown in Figure 3, each receiving antenna receives echoed signal, and the original echo data that generate each receiving antenna can represent suc as formula (1):

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}---\left(1\right)$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent that emitting antenna is apart from the distance of target, because emitting antenna and first receiving antenna are positioned over same position, therefore, R ₁also can represent the distance of first receiving antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents noise, in the present embodiment, is preferably white Gaussian noise.

S202: the original echo data of each receiving antenna, by down coversion and apart from after compression is processed, can be obtained to the first equivalent echo data of each receiving antenna;

It should be noted that, due to far-field effect, R _ican represent suc as formula (2):

R _i＝R ₁+(i-1)d·sin(θ-β _t) (2)

By the R in formula (1) _iwith formula (2) replace, and carry out down coversion and distance to compression process after, the first equivalent echo data of each receiving antenna can represent suc as formula (3):

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e (3)

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c.

S203: the first equivalent data of each receiving antenna, in the compression peaks of target is moved same range gate, can be obtained to the second equivalent echo data of each receiving antenna;

It should be noted that, by s ' _i(τ), in the compression peaks of target is moved same range gate, the second equivalent echo data that obtain can be suc as formula shown in (4):

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e (4)

S204: according to the second equivalent echo data acquisition pitching of each receiving antenna to steering vector, and according to described pitching to steering vector target is carried out to direction of arrival estimation by default direction of arrival (DOA, Direction OfArrival) algorithm for estimating.

Exemplary, according to the second equivalent echo data acquisition pitching of each receiving antenna to steering vector specifically can comprise:

First, will calculate s " _i(τ) be set to τ=τ ₀, can obtain the pitching of the corresponding each receiving antenna of target to signal, can represent suc as formula (5):

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e (5)

Wherein, λ represents that pitching is to the constant component in signal;

Then, the form by the pitching of all receiving antennas to signal composition vector model, described pitching can represent suc as formula (6) to the vector model of signal:

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}---\left(6\right)$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ Can be expressed as the steering vector of pitching to signal; for the noise vector of white Gaussian noise.

Further, from formula (6), can find out, pitching in the vector model of signal, steering vector comprise the directional information β of target _t, therefore, it is right to come by DOA algorithm for estimating in β _testimate, can be according to the pitching shown in formula (6) vector model to signal, by card Peng Capon algorithm, multiple signal classification (MUSIC, Multiple Signal Classification) algorithm, by ESPRIT estimated signal parameter (ESPRIT, Estimating Signal Parameters via Rotational Invariance Techniques) the DOA algorithm such as algorithm realizes, in the present embodiment, preferably, according to described pitching to steering vector by Capon algorithm to target carry out direction of arrival DOA estimate, making the object reaching is to make the echo output power of other interference radiating way reach minimum, and reach maximum in the output power of direction of arrival, so, detailed process can be:

First, obtain the covariance matrix of pitching to the vector model of signal according to formula (7):

$R_s=E\left(\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right){\stackrel{\→}{s}}^H\left({\mathrm{\τ}}_0\right)\right)---\left(7\right)$

Wherein, E represents expectation computing symbol; H represents conjugate transpose;

Then, according to pitching to steering vector and formula (7) obtain the spatial spectrum function of pitching to the vector model of signal, wherein, described pitching to the spatial spectrum function of the vector model of signal suc as formula shown in (8):

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}---\left(8\right)$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

Finally, search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.

S205: according to the direction of arrival of described target, echo receive direction is revised, thereby made the echo receive direction of each receiving antenna point to described target.

Exemplary, in the present embodiment, getting β _tafterwards, each receiving antenna can be modified to β by θ by echo receive direction _t, thereby the echo receive direction of each receiving antenna can be pointed to described target.

Understandable, getting β _tafterwards, Ka wave band SAR can be according to θ and β _tbetween differ to close and tie up to revising in the imaging process of described target, can avoid occurring the beam position deviation that causes in SCORE mode, thereby can improve the accuracy that received beam points to, and reduce the gain loss that receives signal.

The Ka wave band SAR signal processing method that the embodiment of the present invention provides, target direction of arrival in echoed signal is estimated, and carry out received beam sensing according to the direction of arrival of target, can improve the accuracy that received beam points to, thereby reduce the gain loss that receives signal.

Based on the identical technical conceive of above-described embodiment, referring to Fig. 4, it shows the structure of a kind of Ka wave band SAR signal handling equipment 40 that the embodiment of the present invention provides, this equipment 40 can comprise: pitching is to multipath reception unit 401, multiple signals processing unit 402, direction of arrival estimation unit 403 and amending unit 404, wherein

Pitching, to multipath reception unit 401, comprises multipath reception antenna, receives respectively echoed signal for multipath reception antenna, and generates the original echo data of each receiving antenna;

Multiple signals processing unit 402, for passing through pitching down coversion and apart from after compression is processed, can obtain the first equivalent echo data of each receiving antenna to the original echo data of each receiving antenna of multipath reception unit 401;

And by the first equivalent data of each receiving antenna in the compression peaks of target is moved same range gate, can obtain the second equivalent echo data of each receiving antenna;

Direction of arrival estimation unit 403, for according to the second equivalent echo data acquisition pitching of each receiving antenna to steering vector;

And by pitching to steering vector target is carried out to direction of arrival estimation by default direction of arrival (DOA, Direction OfArrival) algorithm for estimating;

Amending unit 404, for estimating that according to direction of arrival estimation unit 403 direction of arrival of the described target obtaining revises to the echo receive direction of each receiving antenna of multipath reception unit 401 pitching, thereby make pitching point to described target to the echo receive direction of each receiving antenna of multipath reception unit 401.

Exemplary, pitching can mode as shown in Figure 3 be arranged to each receiving antenna of multipath reception unit 401, and the original echo data of each receiving antenna can represent suc as formula (9):

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}---\left(9\right)$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent that emitting antenna is apart from the distance of target, because emitting antenna and first receiving antenna are positioned over same position, therefore, R ₁also can represent the distance of first receiving antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents noise, in the present embodiment, is preferably white Gaussian noise.

It should be noted that, due to far-field effect, R _ican represent suc as formula (10):

R _i＝R ₁+(i-1)d·sin(θ-β _t) (10)

Exemplarily, multiple signals processing unit 402 can be processed respectively the original echo data of each receiving antenna, concrete structure as shown in Figure 5,

First, multiple signals processing unit 402 comprises the processing branch road corresponding with each receiving antenna difference, each processing branch road is followed successively by low noise amplifier (LNA according to the processing sequence of signal, Low Noise Amplifier), low-converter, A-D converter (ADC, Analog-to-Digital Converter), Range compress unit, peak value move unit

Low noise amplifier is connected to each receiving antenna of multipath reception unit 401 with pitching, peak value is moved unit and is connected with direction of arrival estimation unit 403, according to the structure of the multiple signals processing unit 402 shown in Fig. 5, can learn, after the original echo data of each receiving antenna are passed through the processing of LNA, low-converter, ADC and Range compress unit successively, the first equivalent echo data of each receiving antenna can represent suc as formula (11);

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e (11)

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c.

The first equivalent echo data of each receiving antenna are moved unit by s ' by peak value _i(τ), after in the compression peaks of target is moved same range gate, the second equivalent echo data that obtain can be suc as formula shown in (12);

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e (12)

Exemplarily, direction of arrival estimation unit 403 specifically can be for:

To calculate s " _i(τ) be set to τ=τ ₀, can obtain the pitching of the corresponding each receiving antenna of target to signal, can represent suc as formula (13);

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e (13)

Wherein, λ represents that pitching is to the constant component in signal;

Form by from the pitching of all receiving antennas to signal composition vector model, described pitching can represent suc as formula (14) to the vector model of signal.

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}---\left(14\right)$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ Can be expressed as the steering vector of pitching to signal; for the noise vector of white Gaussian noise.

Further, direction of arrival estimation unit 403 specifically can be for:

Obtain the covariance matrix of pitching to the vector model of signal according to formula (15):

$R_s=E\left(\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right){\stackrel{\→}{s}}^H\left({\mathrm{\τ}}_0\right)\right)---\left(15\right)$

Wherein, E represents expectation computing symbol; H represents conjugate transpose;

And, according to pitching to steering vector and formula (15) obtain the spatial spectrum function of pitching to the vector model of signal, wherein, described pitching to the spatial spectrum function of the vector model of signal suc as formula shown in (16):

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}---\left(16\right)$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

And, search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.

Exemplary, in the present embodiment, direction of arrival estimation unit 403 is getting β _tafterwards, amending unit 404 is for being modified to β by the echo receive direction of each receiving antenna by θ _t, thereby the echo receive direction of each receiving antenna can be pointed to described target.

The Ka wave band SAR signal handling equipment 40 that the embodiment of the present invention provides, target direction of arrival in echoed signal is estimated, and carry out received beam sensing according to the direction of arrival of target, can improve the accuracy that received beam points to, thereby reduce the gain loss that receives signal.

Those skilled in the art should understand, embodiments of the invention can be provided as method, system or computer program.Therefore, the present invention can adopt hardware implementation example, implement software example or the form in conjunction with the embodiment of software and hardware aspect.And the present invention can adopt the form at one or more upper computer programs of implementing of computer-usable storage medium (including but not limited to magnetic disk memory and optical memory etc.) that wherein include computer usable program code.

The present invention is with reference to describing according to process flow diagram and/or the block scheme of the method for the embodiment of the present invention, equipment (system) and computer program.Should understand can be by the flow process in each flow process in computer program instructions realization flow figure and/or block scheme and/or square frame and process flow diagram and/or block scheme and/or the combination of square frame.Can provide these computer program instructions to the processor of multi-purpose computer, special purpose computer, Embedded Processor or other programmable data processing device to produce a machine, the instruction that makes to carry out by the processor of computing machine or other programmable data processing device produces the device for realizing the function of specifying at flow process of process flow diagram or multiple flow process and/or square frame of block scheme or multiple square frame.

These computer program instructions also can be stored in energy vectoring computer or the computer-readable memory of other programmable data processing device with ad hoc fashion work, the instruction that makes to be stored in this computer-readable memory produces the manufacture that comprises command device, and this command device is realized the function of specifying in flow process of process flow diagram or multiple flow process and/or square frame of block scheme or multiple square frame.

These computer program instructions also can be loaded in computing machine or other programmable data processing device, make to carry out sequence of operations step to produce computer implemented processing on computing machine or other programmable devices, thereby the instruction of carrying out is provided for realizing the step of the function of specifying in flow process of process flow diagram or multiple flow process and/or square frame of block scheme or multiple square frame on computing machine or other programmable devices.

The above, be only preferred embodiment of the present invention, is not intended to limit protection scope of the present invention.

Claims (12)

1. a Ka wave band SAR signal processing method, is characterized in that, described method comprises:

Pitching receives respectively echoed signal to multipath reception antenna, and generates the original echo data of each receiving antenna;

The original echo data of described each receiving antenna, by down coversion and apart from after compression is processed, are obtained to the first equivalent echo data of each receiving antenna;

The first equivalent data of described each receiving antenna, in the compression peaks of target is moved same range gate, is obtained to the second equivalent echo data of each receiving antenna;

According to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector, and according to described pitching to steering vector by default direction of arrival DOA algorithm for estimating, the direction of arrival of described target is estimated;

According to the direction of arrival of described target, echo receive direction is revised, made the echo receive direction of described each receiving antenna point to described target.

2. method according to claim 1, is characterized in that, described each receiving antenna receives echoed signal, and the original echo data that generate each receiving antenna are as shown in the formula expression:

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent the distance of emitting antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents white Gaussian noise.

3. method according to claim 2, is characterized in that, described the first equivalent echo data are as shown in the formula expression:

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c, wherein, d is the distance between adjacent receiving antenna, θ is direction and the angle of receiving antenna between the projecting direction on ground transmitting, β _tfor direction and the angle of receiving antenna between the projecting direction on ground of the echoed signal returned by target.

4. method according to claim 3, is characterized in that, described the second equivalent echo data are shown below:

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e。

5. method according to claim 4, is characterized in that, according to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector, comprising:

To calculate s " _i(τ) be set to τ=τ ₀, obtain the pitching of described each receiving antenna corresponding to described target to signal, the pitching of described each receiving antenna to signal as shown in the formula expression:

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e

Wherein, λ represents that pitching is to the constant component in signal;

Form by from the pitching of all receiving antennas to signal composition vector model, described pitching to the vector model of signal as shown in the formula expression:

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ represent the steering vector of described pitching to signal; for the noise vector of white Gaussian noise.

6. method according to claim 5, is characterized in that, according to described pitching to steering vector by default DOA algorithm for estimating, target is carried out to direction of arrival estimation, comprising:

According to described pitching to steering vector by Capon algorithm to described target carry out direction of arrival DOA estimate;

Particularly, according to described pitching to steering vector by Capon algorithm to target carry out direction of arrival DOA estimate comprise:

According to the first calculating formula obtain the covariance matrix R of pitching to the vector model of signal _s; Wherein, E represents expectation computing symbol; H represents conjugate transpose;

According to described pitching to steering vector and described covariance matrix R _sobtain the spatial spectrum function of described pitching to the vector model of signal, wherein, described pitching is shown below to the spatial spectrum function of the vector model of signal:

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

Search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.

7. a Ka wave band SAR signal handling equipment, is characterized in that, described equipment comprises: pitching is to multipath reception unit, multiple signals processing unit, and direction of arrival estimation unit and amending unit, wherein,

Described pitching, to multipath reception unit, comprises multipath reception antenna, receives respectively echoed signal for described multipath reception antenna, and generates the original echo data of each receiving antenna;

Multiple signals processing unit, for passing through described pitching down coversion and apart from after compression is processed, obtain the first equivalent echo data of described each receiving antenna to the original echo data of each receiving antenna of multipath reception unit;

And by the first equivalent data of described each receiving antenna in the compression peaks of target is moved same range gate, obtain the second equivalent echo data of each receiving antenna;

Direction of arrival estimation unit, for according to the second equivalent echo data acquisition pitching of described each receiving antenna to steering vector;

And by pitching to steering vector by default direction of arrival DOA algorithm for estimating, described target is carried out to direction of arrival estimation;

Amending unit, for estimating that according to described direction of arrival estimation unit the direction of arrival of the described target obtaining revises to the echo receive direction of each receiving antenna of multipath reception unit described pitching, make described pitching point to described target to the echo receive direction of each receiving antenna of multipath reception unit.

8. equipment according to claim 7, it is characterized in that, described multiple signals processing unit comprises the processing branch road corresponding with described each receiving antenna difference, each processing branch road is followed successively by low noise amplifier LNA, low-converter, A-D converter ADC, Range compress unit, peak value according to the processing sequence of signal and moves unit, wherein

Described LNA is connected to each receiving antenna of multipath reception unit with described pitching, and described peak value is moved unit and is connected with described direction of arrival estimation unit.

9. according to the equipment described in claim 7 or 8, it is characterized in that, the original echo data of described each receiving antenna are as shown in the formula expression:

$\begin{array}{c}{s}_i\left(\mathrm{\τ}\right)=\mathrm{rect}\left[\frac{\mathrm{\τ}-(R_1+R_i)/c}{T}\right]\·\exp (j2\mathrm{\π}{f}_c(R_1+R_i)/c)\\ \·\exp \left(\mathrm{j\π}{K}_r{[\mathrm{\τ}-(R_1+R_i)/c]}^2\right)+e\end{array}$

Wherein, i represents i receiving antenna, and i=1,2 ..., N; Rect[] expression rectangular pulse signal; C is the light velocity; R ₁represent the distance of emitting antenna apart from target; R _irepresent the distance of i receiving antenna apart from target; T is expressed as pulsewidth; J is imaginary unit; K _rfor frequency modulation rate; f _cfor the carrier frequency of signal; E represents white Gaussian noise.

10. equipment according to claim 9, is characterized in that, described the first equivalent echo data are as shown in the formula expression:

s′ _i(τ)＝γ·sinc(K _rT(τ-(τ ₀+Δτ _i)))·exp(-j2πf _c·Δτ _i)+e

Wherein, γ be down coversion and distance to compression constant component after treatment, τ ₀=2R ₁/ c, Δ τ _i=(i-1) dsin (θ-β _t)/c, wherein, d is the distance between adjacent receiving antenna, θ is direction and the angle of receiving antenna between the projecting direction on ground transmitting, β _tfor direction and the angle of receiving antenna between the projecting direction on ground of the echoed signal returned by target;

Described the second equivalent echo data are shown below:

s″ _i(τ)＝γ·sinc((τ-τ ₀)/T)·exp(-j2πf _c·Δτ _i)+e。

11. equipment according to claim 10, is characterized in that, described direction of arrival estimation unit specifically for:

To calculate s " _i(τ) be set to τ=τ ₀, obtain the pitching of the corresponding each receiving antenna of target to signal, the pitching of described each receiving antenna to signal as shown in the formula expression;

s″ _i(τ ₀)＝λ·exp(-j2πf _c·Δτ _i)+e

Wherein, λ represents that pitching is to the constant component in signal;

And, the form by the pitching of all receiving antennas to signal composition vector model, described pitching to the vector model of signal as shown in the formula expression:

$\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)=\mathrm{\λ}\·\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)+\stackrel{\→}{e}$

Wherein, $\stackrel{\→}{s}\left({\mathrm{\τ}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\τ}}_0\right)& s_2\left({\mathrm{\τ}}_0\right)& ...& s_i\left({\mathrm{\τ}}_0\right)& ...& s_N\left({\mathrm{\τ}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\→}{a}\left({\mathrm{\β}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_2)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_i)& \·\·\·& \exp (-j2\mathrm{\π}{f}_c\·\mathrm{\Δ}{\mathrm{\τ}}_N)\end{array}\right]}^T,$ represent the steering vector of described pitching to signal; for the noise vector of white Gaussian noise.

12. equipment according to claim 11, is characterized in that, described direction of arrival estimation unit specifically for:

According to the second calculating formula obtain the covariance matrix R of pitching to the vector model of signal _s; Wherein, E represents expectation computing symbol; H represents conjugate transpose;

And, according to pitching to steering vector and described covariance matrix R _sobtain the spatial spectrum function of pitching to the vector model of signal, wherein, described pitching is to shown in the spatial spectrum function following formula of the vector model of signal:

$P_{\mathrm{out}}\left(\mathrm{\β}\right)=\frac{1}{{\stackrel{\→}{\mathrm{\α}}}^H\left(\mathrm{\β}\right)R_s^{-1}\stackrel{\→}{\mathrm{\α}}\left(\mathrm{\β}\right)}$

Wherein, β represents to receive the direction of arrival of signal, P _out(β) represent to receive the output power of signal to each direction of arrival;

And, search for direction of arrival β all in described spatial spectrum function, and will make P _out(β) maximum direction of arrival β _tas the direction of arrival of target.