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 Ka-band synthetic aperture radar SAR signal processing method and device

technical field

The invention relates to radar signal processing technology, in particular to a Ka-band synthetic aperture radar (SAR, Synthetic Aperture Radar) signal processing method and equipment.

Background technique

Among the available bands for radar transmission signals, the Ka band has the characteristics of short wavelength, which makes the Ka band SAR antenna have many advantages such as small size and light weight; in addition, due to the short wavelength and high frequency of the Ka band, the Radar signals can have a high absolute bandwidth, which enables Ka-band SAR to achieve high range resolution.

However, due to the short-wavelength characteristics of the Ka-band signal, the attenuation is serious in rainy environments, resulting in a decrease in the receiving gain of the Ka-band. This inevitably determines that the Ka-band needs to use DBF technology to improve the receiving gain.

At present, in the distance direction of the radar, a multi-channel scan-on-receive (SCORE, Scan-On-Receive) method is usually used to form a high-gain pencil beam that scans from the near end of the radar to the far end and tracks the pulse in real time. to compensate for the loss of gain.

However, using SCORE to process radar signals is based on the assumption that the earth is an ideal smooth sphere. However, in reality, the earth is an ellipsoid with plains, mountains, hills, and basins, and there are many mountainous areas with large ups and downs on the surface. If the ideal sphere model is still used to calculate the beamforming weight vector at this time, it will cause a serious deviation of the beam pointing, resulting in a loss of the gain of the received signal.

As shown in FIG. 1 , it shows a Ka-band SAR signal processing scenario using SCORE in an embodiment of the present invention. In FIG. 1 , the real target 1 is on a hillside 4 at a height h from the surface 3 Above, the distance between the real target 1 and the array antenna 5 is R, the distance between the array antenna 5 and the ground surface is shown by the dotted arrow, the arrangement order of the apertures in the array antenna 5 is shown by the dotted arrow, and at the foot of the hillside 4 There is also a non-real target 2, the distance between the non-real target 2 and the array antenna 5 is the same as the distance between the real target 1 and the array antenna 5, which is also R, so, if the SCORE method is used, the earth is regarded as an ideal sphere model, without considering the height fluctuation of the ground surface for signal processing, then, when the array antenna 5 receives the echo signal of the real target 1, the beam direction formed by the array antenna 5 according to the echo signal will be non-directional. Real target 2; so that the echo gain of real target 1 to the beam is greatly weakened.

Contents of the invention

In order to solve the above technical problems, the embodiments of the present invention expect to provide a Ka-band SAR signal processing method and device, which can improve the accuracy of receiving beam pointing, thereby reducing the gain loss of receiving signals.

Technical scheme of the present invention is realized like this:

In a first aspect, an embodiment of the present invention provides a Ka-band SAR signal processing method, the method may include:

The multiple receiving antennas in the elevation direction receive the echo signals respectively, and generate the original echo data of each receiving antenna;

The first equivalent echo data of each receiving antenna is obtained after the original echo data of each receiving antenna is subjected to down-conversion and range compression processing;

Moving the first equivalent data of each receiving antenna to the same range gate at the compressed peak value of the target to obtain the second equivalent echo data of each receiving antenna;

Acquiring the steering vector in the pitch direction according to the second equivalent echo data of each receiving antenna, and estimating the direction of arrival of the target through a preset direction of arrival DOA estimation algorithm according to the steering vector in the pitch direction ;

The echo receiving direction is corrected according to the direction of arrival of the target, so that the echo receiving directions of the receiving antennas point to the target.

According to the first possible implementation manner, in combination with the first aspect, each receiving antenna receives the echo signal, and generates the original echo data of each receiving antenna as follows:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; rect</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; e</span>}\end{array}$

Among them, i represents the i-th receiving antenna, and i=1, 2, ..., N; rect[] represents a rectangular pulse signal; c is the speed of light; R ₁ represents the distance between the transmitting antenna and the target; R _i represents the i-th The distance between each receiving antenna and the target; T is the pulse width; j is the imaginary number unit; K _r is the modulation frequency; f _c is the carrier frequency of the signal; e is Gaussian white noise.

According to the second possible implementation, combined with the first possible implementation, the first equivalent echo data is represented by the following formula:

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

Among them, γ is the constant part after down-conversion and range compression, τ ₀ =2R ₁ /c, Δτ _i =(i-1)d·sin(θ-β _t )/c, where d is the adjacent The distance between the receiving antennas, θ is the angle between the direction of the transmitting signal and the projection direction of the receiving antenna on the ground, β _t is the distance between the direction of the echo signal returned by the target and the projection direction of the receiving antenna on the ground angle.

According to the third possible implementation, combined with the second possible implementation, the second equivalent echo data is shown in the following formula:

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

According to the fourth possible implementation, combined with the third possible implementation, obtaining the steering vector in the pitch direction according to the second equivalent echo data of each receiving antenna includes:

Set the calculation s″ _i (τ) to τ=τ ₀ to obtain the pitch direction signals of the receiving antennas corresponding to the target, and the pitch direction signals of the receiving antennas are expressed as follows:

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

Among them, λ represents the constant part of the pitch signal;

The elevation signals of all receiving antennas are formed into a vector model, and the vector model of the elevation signals is expressed as follows:

$\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}$

in, $\stackrel{\&Right\; Arrow;}{\mathrm{the\; s}}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{\mathrm{the\; s}}_1\left({\mathrm{\&tau;}}_0\right)& {\mathrm{the\; s}}_2\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_i\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transpose symbol of the vector; $\stackrel{\&Right\; Arrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&Center\; Dot;\&CenterDot;\&Center\; Dot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ represents the steering vector of the pitch signal; is the noise vector of white Gaussian noise.

According to the fifth possible implementation, combined with the fourth possible implementation, the direction of arrival estimation is performed on the target through a preset DOA estimation algorithm according to the steering vector in the pitch direction, including:

Carrying out DOA estimation of the direction of arrival to the target through the Capon algorithm according to the steering vector in the pitch direction;

Specifically, performing the DOA estimation of the direction of arrival on the target through the Capon algorithm according to the steering vector of the pitch direction includes:

According to the first formula Obtain the covariance matrix R _s of the vector model of the pitch signal; where, E represents the expectation operator; H represents the conjugate transpose;

Obtain the spatial spectral function of the vector model of the pitch signal according to the steering vector of the pitch direction and the covariance matrix R _s , wherein the spatial spectral function of the vector model of the pitch signal is as follows:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

Among them, β represents the direction of arrival of the received signal, and P _out (β) represents the output power of the received signal to each direction of arrival;

Search all DOA β in the spatial spectrum function, and use the DOA β _t that maximizes P _out (β) as the DOA of the target.

In the second aspect, the embodiment of the present invention provides a Ka-band SAR signal processing device, which is characterized in that the device includes: an elevation multi-channel receiving unit, a multi-channel signal processing unit, a direction of arrival estimation unit and a correction unit, in,

The elevation multi-channel receiving unit includes a multi-channel receiving antenna, which is used for the multiple receiving antennas to respectively receive echo signals and generate original echo data of each receiving antenna;

The multi-channel signal processing unit is used to obtain the first equivalent echo of each receiving antenna by down-converting and compressing the original echo data of each receiving antenna of the multi-channel receiving unit in the elevation direction data;

and moving the first equivalent data of each receiving antenna to the same range gate at the compressed peak value of the target, so as to obtain the second equivalent echo data of each receiving antenna;

A DOA estimating unit, configured to obtain a steering vector in the elevation direction according to the second equivalent echo data of each receiving antenna;

and performing direction of arrival estimation on the target with the steering vector in the pitch direction through a preset direction of arrival DOA estimation algorithm;

a correcting unit, configured to correct the echo receiving direction of each receiving antenna of the multi-path receiving unit according to the direction-of-arrival of the target estimated by the direction-of-arrival estimating unit, so that the multi-path The echo receiving direction of each receiving antenna of the receiving unit points to the target.

According to the first possible implementation, in combination with the second aspect, the multi-channel signal processing unit includes processing branches respectively corresponding to the receiving antennas, and each processing branch is a low-noise amplifier in sequence according to the signal processing order LNA, down-converter, analog-to-digital converter ADC, distance compression unit, peak shift unit, wherein,

The LNA is connected to each receiving antenna of the elevation multi-channel receiving unit, and the peak shifting unit is connected to the direction-of-arrival estimating unit.

According to the second possible implementation, combined with the second aspect or the first possible implementation, the original echo data of each receiving antenna is represented by the following formula:

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; rect</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; e</span>}\end{array}$

Among them, i represents the i-th receiving antenna, and i=1, 2, ..., N; rect[] represents a rectangular pulse signal; c is the speed of light; R ₁ represents the distance between the transmitting antenna and the target; R _i represents the i-th The distance between each receiving antenna and the target; T is the pulse width; j is the imaginary number unit; K _r is the modulation frequency; f _c is the carrier frequency of the signal; e is Gaussian white noise.

According to the third possible implementation, combined with the second possible implementation, the first equivalent echo data is represented by the following formula:

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

Among them, γ is the constant part after down-conversion and range compression, τ ₀ =2R ₁ /c, Δτ _i =(i-1)d·sin(θ-β _t )/c, where d is the adjacent The distance between the receiving antennas, θ is the angle between the direction of the transmitting signal and the projection direction of the receiving antenna on the ground, β _t is the distance between the direction of the echo signal returned by the target and the projection direction of the receiving antenna on the ground the included angle;

The second equivalent echo data is shown in the following formula:

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

According to the fourth possible implementation manner, in combination with the third possible implementation manner, the DOA estimating unit is specifically configured to:

The calculation s″ _i (τ) is set to τ=τ ₀ to obtain the pitch direction signals of each receiving antenna corresponding to the target, and the pitch direction signals of each receiving antenna are represented by the following formula;

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

Among them, λ represents the constant part of the pitch signal;

And, the pitch direction signals of all receiving antennas are formed into the form of a vector model, and the vector model of the pitch direction signals is expressed as follows:

$\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}$

in, $\stackrel{\&Right\; Arrow;}{\mathrm{the\; s}}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{\mathrm{the\; s}}_1\left({\mathrm{\&tau;}}_0\right)& {\mathrm{the\; s}}_2\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_i\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transpose symbol of the vector; $\stackrel{\&Right\; Arrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&Center\; Dot;\&Center\; Dot;\&Center\; Dot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ represents the steering vector of the pitch signal; is the noise vector of white Gaussian noise.

According to the fifth possible implementation manner, in combination with the fourth possible implementation manner, the DOA estimating unit is specifically configured to:

According to the second formula Obtain the covariance matrix R _s of the vector model of the pitch signal; where, E represents the expectation operator; H represents the conjugate transpose;

And, obtain the spatial spectrum function of the vector model of the pitch signal according to the steering vector of the pitch direction and the covariance matrix R _s , wherein the spatial spectrum function of the vector model of the pitch signal is shown in the following formula:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}$

Among them, β represents the direction of arrival of the received signal, and P _out (β) represents the output power of the received signal to each direction of arrival;

And, search for all directions of arrival β in the spatial spectral function, and use the direction of arrival β _t that maximizes P _out (β) as the direction of arrival of the target.

The embodiment of the present invention provides a Ka-band SAR signal processing method and equipment, which estimates the direction of arrival of the target in the echo signal, and performs receiving beam pointing according to the direction of arrival of the target, which can improve the accuracy of the receiving beam pointing , thereby reducing the gain loss of the received signal.

Description of drawings

FIG. 1 is a schematic diagram of a Ka-band SAR signal processing scenario using SCORE mode provided by an embodiment of the present invention;

Fig. 2 is a schematic flow chart of a Ka-band SAR signal processing method provided by an embodiment of the present invention;

FIG. 3 is a schematic diagram of a Ka-band SAR multi-channel receiving antenna arrangement structure provided by an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a Ka-band SAR signal processing device provided by an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a multi-channel signal processing unit provided by an embodiment of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

Referring to FIG. 2 , it shows the flow of a Ka-band SAR signal processing method provided by an embodiment of the present invention, the method may include:

S201: receiving the echo signals respectively by multiple receiving antennas in the elevation direction, and generating the original echo data of each receiving antenna;

In order to clearly illustrate the technical solution of the embodiment of the present invention, refer to FIG. 3 , which shows a Ka-band SAR multi-channel receiving antenna arrangement structure provided by the embodiment of the present invention. In addition to the arrangement structure of multi-channel receiving antennas, the arrangement structure of multi-channel receiving antennas of other Ka-band SARs can also apply the technical solution of the embodiment of the present invention, which is not specifically limited in the embodiment of the present invention.

In Fig. 3, the pitching multi-channel receiving antennas of Ka-band SAR are uniformly arranged N receiving antennas, the distance between adjacent receiving antennas is d, and the transmitting antenna can be placed at any receiving antenna, and the The receiving antenna at is used as the reference receiving antenna. In this embodiment, the first receiving antenna is used as the reference receiving antenna, then the transmitting antenna and the first receiving antenna are placed at the same position, and H _orbit represents the projection of the receiving antenna on the ground Direction, the direction of the transmitting signal is R _v in Figure 3, R _v is perpendicular to the arrangement direction of the receiving antenna, and the angle between R _v and H _orbit is θ; R ₁ to _RN represent the first receiving antenna To the direction where the Nth receiving antenna receives the echo signal returned by the target, since the distance from the target to each receiving antenna is far greater than the distance between the receiving antennas, the target can be a far-field target. According to the far-field effect, R ₁ to R _N are parallel to each other, and the included angle between R ₁ to R _N and H _orbit is β _t ;

Therefore, it can be seen from Fig. 3 that each receiving antenna receives the echo signal and generates the original echo data of each receiving antenna, which can be expressed as formula (1):

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; rect</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; e</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them, i represents the i-th receiving antenna, and i=1, 2, ..., N; rect[] represents a rectangular pulse signal; c is the speed of light; R ₁ represents the distance between the transmitting antenna and the target, because the transmitting antenna and the first A receiving antenna is placed at the same position, therefore, R ₁ can also represent the distance from the first receiving antenna to the target; R _i represents the distance from the i-th receiving antenna to the target; T represents the pulse width; j is the imaginary unit ; K _r is the modulation frequency; f _c is the carrier frequency of the signal; e represents noise, and in this embodiment, it is preferably Gaussian white noise.

S202: After the original echo data of each receiving antenna is processed by down-conversion and range compression, the first equivalent echo data of each receiving antenna can be obtained;

It should be noted that due to the far-field effect, R _i can be expressed as formula (2):

R _i ＝R ₁ +(i-1)d·sin(θ-β _t ) (2)

Replace R _i in formula (1) with formula (2), and after down-conversion and range compression processing, the first equivalent echo data of each receiving antenna can be expressed as formula (3):

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

Wherein, γ is the constant part after down-conversion and range compression processing, τ ₀ =2R ₁ /c, Δτ _i =(i-1)d·sin(θ-β _t )/c.

S203: moving the first equivalent data of each receiving antenna at the compressed peak value of the target to the same range gate, so as to obtain the second equivalent echo data of each receiving antenna;

It should be noted that the second equivalent echo data obtained by moving the compressed peak value of s′ _i (τ) in the target to the same range gate can be shown in formula (4):

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

S204: Obtain the steering vector in the pitch direction according to the second equivalent echo data of each receiving antenna, and perform wave arrival on the target through a preset direction of arrival (DOA, Direction Of Arrival) estimation algorithm according to the steering vector in the pitch direction direction estimate.

Exemplarily, obtaining the steering vector in the elevation direction according to the second equivalent echo data of each receiving antenna may specifically include:

First, the calculation of s″ _i (τ) is set as τ=τ ₀ , and the elevation signals of each receiving antenna corresponding to the target can be obtained, which can be expressed as formula (5):

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

Among them, λ represents the constant part of the pitch signal;

Then, the pitch direction signals of all receiving antennas are formed into the form of a vector model, and the vector model of the pitch direction signals can be expressed as formula (6):

$\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

in, $\stackrel{\&Right\; Arrow;}{\mathrm{the\; s}}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{\mathrm{the\; s}}_1\left({\mathrm{\&tau;}}_0\right)& {\mathrm{the\; s}}_2\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_i\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transpose symbol of the vector; $\stackrel{\&Right\; Arrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&Center\; Dot;\&Center\; Dot;\&Center\; Dot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ can be expressed as the steering vector of the pitch signal; is the noise vector of white Gaussian noise.

Furthermore, it can be seen from formula (6) that in the vector model of the pitch signal, the steering vector includes the direction information β _t of the target, therefore, the DOA estimation algorithm can be used to β _t in , can be estimated according to the vector model of the pitch signal shown in formula (6), through the Capon algorithm, the multiple signal classification (MUSIC, Multiple Signal Classification) algorithm, and the rotation invariant technique to estimate the signal parameters ( ESPRIT, Estimating Signal Parameters via RotationalInvariance Techniques) algorithms and other DOA algorithms to achieve, in this embodiment, preferably, according to the steering vector of the pitch direction, the DOA estimation of the direction of arrival is carried out to the target through the Capon algorithm, so that the purpose of It is to minimize the echo output power in other interference directions and maximize the output power in the direction of arrival. Therefore, the specific process can be as follows:

First, the covariance matrix of the vector model of the pitch signal is obtained according to formula (7):

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Among them, E represents the expectation operator; H represents the conjugate transpose;

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

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Among them, β represents the direction of arrival of the received signal, and P _out (β) represents the output power of the received signal to each direction of arrival;

Finally, all DOA β in the spatial spectrum function are searched, and the DOA β _t that maximizes P _out (β) is used as the DOA of the target.

S205: Correct the echo receiving direction according to the direction of arrival of the target, so that the echo receiving direction of each receiving antenna points to the target.

Exemplarily, in this embodiment, after obtaining β _t , each receiving antenna can correct the echo receiving direction from θ to β _t , so that the echo receiving direction of each receiving antenna can be directed to the target.

It can be understood that after obtaining β _t , the Ka-band SAR can correct the target during the imaging process according to the phase difference relationship between θ and β _t , which can avoid the beam pointing deviation caused by the SCORE method, Therefore, the accuracy of receiving beam pointing can be improved, and the gain loss of receiving signals can be reduced.

The Ka-band SAR signal processing method provided by the embodiment of the present invention estimates the direction of arrival of the target in the echo signal, and directs the receiving beam according to the direction of arrival of the target, which can improve the accuracy of the receiving beam pointing, thereby reducing the Signal gain loss.

Based on the same technical idea of the above-mentioned embodiments, see FIG. 4 , which shows the structure of a Ka-band SAR signal processing device 40 provided by an embodiment of the present invention. The device 40 may include: an elevation multi-channel receiving unit 401, a multiple Road signal processing unit 402, direction of arrival estimation unit 403 and correction unit 404, wherein,

Elevation multi-channel receiving unit 401, including multiple receiving antennas, used for multiple receiving antennas to receive echo signals respectively, and generate original echo data of each receiving antenna;

The multi-channel signal processing unit 402 is configured to obtain the first equivalent echo data of each receiving antenna after the original echo data of each receiving antenna of the multi-channel receiving unit 401 in the elevation direction is down-converted and compressed in the range direction;

And moving the first equivalent data of each receiving antenna to the same range gate at the compressed peak value of the target, the second equivalent echo data of each receiving antenna can be obtained;

A DOA estimating unit 403, configured to obtain a steering vector in the elevation direction according to the second equivalent echo data of each receiving antenna;

And the direction of arrival (DOA, Direction Of Arrival) estimation algorithm is used to estimate the direction of arrival of the target by the steering vector of the pitch direction;

The correction unit 404 is configured to correct the echo receiving direction of each receiving antenna of the multi-path receiving unit 401 according to the direction of arrival of the target estimated by the direction-of-arrival estimating unit 403, so that the multi-path receiving direction of the pitch direction The echo receiving direction of each receiving antenna of unit 401 points to the target.

Exemplarily, the receiving antennas of the pitching multi-channel receiving unit 401 can be arranged as shown in FIG. 3 , and the original echo data of each receiving antenna can be expressed as formula (9):

$\begin{array}{c}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; rect</span>}<span\; class="notranslate">\; [</span>\frac{\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; )</span>\\ <span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; \&tau;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; e</span>}\end{array}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Among them, i represents the i-th receiving antenna, and i=1, 2, ..., N; rect[] represents a rectangular pulse signal; c is the speed of light; R ₁ represents the distance between the transmitting antenna and the target, because the transmitting antenna and the first A receiving antenna is placed at the same position, therefore, R ₁ can also represent the distance from the first receiving antenna to the target; R _i represents the distance from the i-th receiving antenna to the target; T represents the pulse width; j is the imaginary unit ; K _r is the modulation frequency; f _c is the carrier frequency of the signal; e represents noise, and in this embodiment, it is preferably Gaussian white noise.

It should be noted that due to the far-field effect, R _i can be expressed as formula (10):

R _i ＝R ₁ +(i-1)d·sin(θ-β _t ) (10)

Exemplarily, the multi-channel signal processing unit 402 can separately process the original echo data of each receiving antenna, and the specific structure is shown in FIG. 5 ,

First, the multi-channel signal processing unit 402 includes processing branches respectively corresponding to each receiving antenna, and each processing branch is successively a low noise amplifier (LNA, Low Noise Amplifier), a down-converter, and an analog-to-digital converter according to the signal processing order. (ADC, Analog-to-Digital Converter), distance compression unit, peak shift unit,

The low-noise amplifier is connected to each receiving antenna of the multi-channel receiving unit 401 in elevation, and the peak shifting unit is connected to the direction-of-arrival estimation unit 403. According to the structure of the multi-channel signal processing unit 402 shown in FIG. 5, it can be known that, After the original echo data of each receiving antenna is sequentially processed by the LNA, down-converter, ADC and distance compression unit, the first equivalent echo data of each receiving antenna can be expressed as formula (11);

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

Wherein, γ is the constant part after down-conversion and range compression processing, τ ₀ =2R ₁ /c, Δτ _i =(i-1)d·sin(θ-β _t )/c.

After the first equivalent echo data of each receiving antenna is moved to the same range gate by the peak value transfer unit, the second equivalent echo data can _be obtained as formula (12) shown;

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

Exemplarily, the direction of arrival estimating unit 403 may be specifically configured to:

Set the calculation s″ _i (τ) as τ=τ ₀ , and the elevation signals of the receiving antennas corresponding to the target can be obtained, which can be expressed as formula (13);

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

Among them, λ represents the constant part of the pitch signal;

The elevation signals of all the receiving antennas are formed into a vector model, and the vector model of the elevation signal can be expressed as formula (14).

$\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

in, $\stackrel{\&Right\; Arrow;}{\mathrm{the\; s}}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{\mathrm{the\; s}}_1\left({\mathrm{\&tau;}}_0\right)& {\mathrm{the\; s}}_2\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_i\left({\mathrm{\&tau;}}_0\right)& ...& {\mathrm{the\; s}}_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transpose symbol of the vector; $\stackrel{\&Right\; Arrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&CenterDot;\&Center\; Dot;\&Center\; Dot;& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&Center\; Dot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ can be expressed as the steering vector of the pitch signal; is the noise vector of white Gaussian noise.

Further, the direction of arrival estimating unit 403 may specifically be used for:

According to formula (15), the covariance matrix of the vector model of the pitch signal is obtained:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 15</span>}<span\; class="notranslate">\; )</span>$

Among them, E represents the expectation operator; H represents the conjugate transpose;

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

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

Among them, β represents the direction of arrival of the received signal, and P _out (β) represents the output power of the received signal to each direction of arrival;

And, search for all directions of arrival β in the spatial spectral function, and use the direction of arrival β _t that maximizes P _out (β) as the direction of arrival of the target.

Exemplarily, in this embodiment, after the direction of arrival estimating unit 403 acquires β _t , the modifying unit 404 is used to modify the echo receiving direction of each receiving antenna from θ to β _t , so that each receiving antenna The echo receiving direction points to the target.

The Ka-band SAR signal processing device 40 provided by the embodiment of the present invention estimates the direction of arrival of the target in the echo signal, and directs the receiving beam according to the direction of arrival of the target, which can improve the accuracy of the receiving beam pointing, thereby reducing The gain loss of the received signal.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the 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:

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

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:

$\stackrel{\&RightArrow;}{s}\left({\mathrm{\&tau;}}_0\right)=\mathrm{\&lambda;}\&CenterDot;\stackrel{\&RightArrow;}{a}\left({\mathrm{\&beta;}}_t\right)+\stackrel{\&RightArrow;}{e}$

Wherein, $\stackrel{\&RightArrow;}{s}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\&tau;}}_0\right)& s_2\left({\mathrm{\&tau;}}_0\right)& ...& s_i\left({\mathrm{\&tau;}}_0\right)& ...& s_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\&RightArrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ 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:

$P_{\mathrm{out}}\left(\mathrm{\&beta;}\right)=\frac{1}{{\stackrel{\&RightArrow;}{\mathrm{\&alpha;}}}^H\left(\mathrm{\&beta;}\right)R_s^{-1}\stackrel{\&RightArrow;}{\mathrm{\&alpha;}}\left(\mathrm{\&beta;}\right)}$

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:

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

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:

$\stackrel{\&RightArrow;}{s}\left({\mathrm{\&tau;}}_0\right)=\mathrm{\&lambda;}\&CenterDot;\stackrel{\&RightArrow;}{a}\left({\mathrm{\&beta;}}_t\right)+\stackrel{\&RightArrow;}{e}$

Wherein, $\stackrel{\&RightArrow;}{s}\left({\mathrm{\&tau;}}_0\right)={\left[\begin{array}{cccccc}{s}_1\left({\mathrm{\&tau;}}_0\right)& s_2\left({\mathrm{\&tau;}}_0\right)& ...& s_i\left({\mathrm{\&tau;}}_0\right)& ...& s_N\left({\mathrm{\&tau;}}_0\right)\end{array}\right]}^T,$ T represents the transposition symbol of vector; $\stackrel{\&RightArrow;}{a}\left({\mathrm{\&beta;}}_t\right)={\left[\begin{array}{cccccc}1& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_2)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_i)& \&CenterDot;\&CenterDot;\&CenterDot;& \exp (-j2\mathrm{\&pi;}{f}_c\&CenterDot;\mathrm{\&Delta;}{\mathrm{\&tau;}}_N)\end{array}\right]}^T,$ 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:

$P_{\mathrm{out}}\left(\mathrm{\&beta;}\right)=\frac{1}{{\stackrel{\&RightArrow;}{\mathrm{\&alpha;}}}^H\left(\mathrm{\&beta;}\right)R_s^{-1}\stackrel{\&RightArrow;}{\mathrm{\&alpha;}}\left(\mathrm{\&beta;}\right)}$

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.