CN105589071B - Airborne radar high-resolution DBS imaging methods based on SPICE - Google Patents

Abstract

The invention discloses a kind of airborne radar high-resolution DBS imaging methods based on SPICE, comprise the following steps：(1) set the echo-signal that airborne radar receives and tie up progress process of pulse-compression in distance, obtain the echo-signal of all range gates after pulse pressure processing；Establish the land clutter echo-signal x of i-th of range gate_iSignal model；(2) the echo-signal y of i-th of range gate after pulse pressure is sought_iCovariance matrix R_i；(3) provide and solve the land clutter echo-signal x of i-th of range gate_iPerformance number Optimized model；(4) by the land clutter echo-signal x of i-th of range gate_iTop n performance number be arranged in order, form i-th of range gate land clutter echo-signal x_iPower vector；And then the power matrix of all range gates is obtained, as final airborne radar echo data matrix.(6) final airborne radar echo data matrix is changed to earth coordinates, obtains final DBS images.

Description

Airborne Radar High Resolution DBS Imaging Method Based on SPICE

technical field

The invention belongs to the field of radar technology, in particular to a high-resolution DBS imaging method for airborne radar based on Sparseiterative covariance-based estimation (SPICE), which can be used when the number of pulses transmitted by airborne radar is small , to obtain a higher image resolution.

Background technique

Doppler beam sharpening (DBS) imaging is a non-focused imaging technology that scans the radar beam in a large area, and generally images the observation area under the condition of frontal side view. Although DBS imaging technology does not have high lateral resolution like synthetic aperture radar imaging technology, the computational complexity of DBS imaging is low, and its lateral resolution ability has been substantially improved compared with real beams, which can be used in relatively Complete imaging of a wide range of scenes in a short period of time.

The traditional DBS imaging technology based on Fourier transform can obtain higher image resolution when the number of radar transmission pulses is sufficient. However, in actual situations, the number of radar transmission pulses is often limited by various factors, such as the range of radar beam scanning, the revisit time of radar scanning, and so on. When the number of pulses emitted by the radar is large, it will reduce the scope of the observation scene and prolong the revisit time of the radar scan, which affects the real-time monitoring of the observation scene by the radar to a certain extent; when the number of pulses emitted by the radar is reduced, although it can improve The radar revisited the observed scene, but the resolution of the DBS image was severely degraded due to insufficient coherent accumulation time. Therefore, under the premise of meeting the image resolution requirements, the revisit time of the radar observation scene should be increased as much as possible. Moreover, the traditional DBS imaging technology based on Fourier transform often leads to the leakage of signal energy, which reduces the definition of DBS images and overestimates the signal energy power.

Contents of the invention

For above-mentioned deficiencies in the prior art, the object of the present invention is to propose a kind of airborne radar high-resolution DBS imaging method based on SPICE, this method sets up the signal model of ground clutter echo signal according to the echo signal after pulse pressure processing, And the optimization model for solving the power value of the ground clutter echo signal is given, and the power matrix of all range gates is obtained, which is the final airborne radar echo data matrix, which is converted from the aircraft coordinate system to the earth coordinate system, Get the final DBS image.

In order to achieve the above-mentioned technical purpose, the present invention adopts the following technical solutions to achieve.

A kind of airborne radar high resolution DBS imaging method based on SPICE, is characterized in that, comprises the following steps:

Step 1, set the echo signal received by the airborne radar as is the echo signal of the i-th range gate; in the aircraft coordinate system where the aircraft is the reference origin, the echo signal received by the airborne radar Perform pulse compression processing in the distance dimension to obtain the echo signal y after pulse pressure processing, y=[y ₁ ,...,y _i ,...,y _M ], y _i is the ith echo signal after pulse pressure The echo signal of the range gate; according to the echo signal y _i of the i-th range gate after the pulse pressure, the signal model of the ground clutter echo signal x _i of the i-th range gate is established; wherein, the i-th range gate after the pulse pressure The dimensionality of the echo signal y _i of a range gate is N * 1, and N is the pulse number of airborne radar transmission, and i=1, 2,..., M, M is the number of range gates;

Step 2, obtain the covariance matrix R _i of the echo signal y _i of the i-th range gate after the pulse pressure;

Step 3, according to the covariance matrix R _i of the echo signal y _i of the i-th range gate after the pulse pressure, an optimization model for solving the power value of the ground clutter echo signal x _i of the i-th range gate is given: Solve the optimization model of the power value of the ground clutter echo signal x _i of the i-th range gate: Obtain the kth power value pi _{, k} of the ground clutter echo signal x _i of the i-th range gate; wherein, k=1, 2, ..., 2N, N is the number of Doppler channels, Indicates the square of the F norm, and the superscript H indicates the conjugate transpose;

Step 4: Arrange the first N power values of the ground clutter echo signal x _i of the i-th range gate in order to form the power vector p _i , p _i of the ground clutter echo signal x _i of the i-th range gate =[p _{i, 1} , p _{i, 2} ,..., p _{i, N} ] ^T ; and then get the power matrix P of all M range gates, P=[p ₁ , p ₂ ,..., p _M ], the power matrix P of all M range gates is the final airborne radar echo data matrix;

Step 5, convert the range gate corresponding to each element in the final airborne radar echo data matrix to the corresponding slant distance, and convert the Doppler frequency corresponding to each element in the final airborne radar echo data matrix to The corresponding azimuth angle, and the slant distance and azimuth angle are converted from the aircraft coordinate system to the earth coordinate system, and then each element in the final airborne radar echo data matrix is used as the pixel value of the corresponding position in the earth coordinate system, Get the final DBS image.

Compared with the prior art, the present invention has the following advantages:

1) Compared with the traditional DBS imaging method, the inventive method improves the revisit rate of the radar to the observation area, and improves the real-time performance of the DBS imaging of the observation area by the radar;

2) The method of the present invention can obtain a DBS image with a higher ground resolution when the number of pulses transmitted by the radar is small.

Description of drawings

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

Figure 2a is the range-Doppler map after FFT transformation;

Figure 2b is the range-Doppler map after SPICE transformation;

Figure 3a is a section view of the range dimension of the range-Doppler map after FFT transformation;

Figure 3b is a section view of the range dimension of the range-Doppler map after SPICE transformation;

Fig. 4a is the DBS imaging result diagram based on FFT transformation;

Fig. 4b is the image of DBS imaging results based on SPICE transformation.

detailed description:

With reference to Fig. 1, the airborne radar high-resolution DBS imaging method based on SPICE of the present invention, concrete realization steps are as follows:

Step 1, set the echo signal received by the airborne radar as is the echo signal of the i-th range gate; in the aircraft coordinate system where the aircraft is the reference origin, the echo signal received by the airborne radar Perform pulse compression processing in the distance dimension to obtain the echo signal y after pulse pressure processing, y=[y ₁ ,...,y _i ,...,y _M ], y _i is the ith echo signal after pulse pressure The echo signal of the range gate; according to the echo signal y _i of the i-th range gate after the pulse pressure, the signal model of the ground clutter echo signal x _i of the i-th range gate is established; wherein, the i-th range gate after the pulse pressure The dimension of the echo signal y _i of the range gates is N×1, N is the number of pulses emitted by the airborne radar, i=1, 2, . . . , M, and M is the number of range gates.

The signal model of the ground clutter echo signal x _i of the i-th range gate is:

y _i =B x _i +e

Among them, B is a time-domain steering vector matrix, and its N row vectors correspond to N different 1×N-dimensional time-domain steering vectors, e is a clutter signal or an interference signal, and its dimension is N×1.

Step 2, obtain the covariance matrix R _i of the echo signal y _i of the i-th range gate after the pulse pressure.

The covariance matrix R _i of the echo signal y _i of the i-th range gate after the pulse pressure is:

Among them, A=[BI _N ], B is the time-domain steering vector matrix, and its N row vectors correspond to N different 1×N-dimensional time-domain steering vectors, I _N is an N×N unit matrix, P _i is the power matrix of the ground clutter echo signal x _i of the i-th range gate, which is a diagonal matrix, and the k-th element p _{i on its diagonal, k} is the ground clutter echo signal of the i-th range gate The kth power value of the wave signal x _i , k=1, 2, . . . , 2N, the superscript H indicates conjugate transposition.

Step 3, according to the covariance matrix R _i of the echo signal y _i of the i-th range gate after the pulse pressure, an optimization model for solving the power value of the ground clutter echo signal x _i of the i-th range gate is given: An optimization model for solving the power value of the ground clutter echo signal x _i of the i-th range gate Obtain the kth power value pi _{, k} of the ground clutter echo signal x _i of the i-th range gate; wherein, k=1, 2, ..., 2N, N is the number of Doppler channels, Represents the square of the F norm, and the superscript H represents the conjugate transpose.

The optimization model of the power value of the ground clutter echo signal x _i of the described solution i range gate is:

Among them, tr(·) represents the trace of the matrix, and C is a constant.

Simplify the optimization problem of solving the power value of the ground clutter echo signal x _i of the i-th range gate, and obtain its simplified form as:

Among them, w _k is the kth power weight of the ground clutter echo signal x _i of the i-th range gate, and its expression is:

where b _kk is the kth element on the diagonal of the time-domain steering vector matrix B.

The optimization model for solving the power value of the ground clutter echo signal x _i of the i-th range gate Its specific sub-steps are:

3.1 Set l as the number of iterations, the initial value of the number of iterations l is 1, set the kth power value p i of the ground clutter echo signal x _i of the i-th range gate, the initial value _{of k}

3.2 Calculate the kth power value of the ground clutter echo signal x _i of the i-th range gate in the l-th iteration

Among them, a _k is the kth column of matrix A, A=[BI _N ], B is the time-domain steering vector matrix, w _k is the kth power weight of the ground clutter echo signal x _i of the i-th range gate value, whose expression is:

Wherein, b _kk is the kth element on the diagonal of the time domain steering vector matrix B;

3.3 If the k-th power value of the ground clutter echo signal x _i of the i-th range gate in the l-th iteration and the kth power value of the ground clutter echo signal x _i of the ith range gate of the l-1th iteration The absolute value of the difference is greater than the set value ε, and the value of the set value ε approaches 0, then increase the number of iterations l by 1, and return to step 4.2.

If the k-th power value of the ground clutter echo signal x _i of the i-th range gate in the l-th iteration and the kth power value of the ground clutter echo signal x _i of the ith range gate of the l-1th iteration The absolute value of the difference is less than or equal to the set value ε, then the kth power value of the ground clutter echo signal x _i of the i-th range gate in the l-th iteration As the kth power value p _i,k of the ground clutter echo signal x _i of the ith range gate.

Step 4: Arrange the first N power values of the ground clutter echo signal x _i of the i-th range gate in order to form the power vector p _i , p _i of the ground clutter echo signal x _i of the i-th range gate =[p _{i, 1} , p _{i, 2} ,..., p _{i, k} ] ^T ; and then get the power matrix P of all M range gates, P=[p ₁ , p ₂ ,..., p _M ], the power matrix P of all M range gates is the final airborne radar echo data matrix.

Step 5, convert the range gate corresponding to each element in the final airborne radar echo data matrix to the corresponding slant distance, and convert the Doppler frequency corresponding to each element in the final airborne radar echo data matrix to The corresponding azimuth angle, and the slant distance and azimuth angle are converted from the aircraft coordinate system to the earth coordinate system, and then each element in the final airborne radar echo data matrix is used as the pixel value of the corresponding position in the earth coordinate system, Get the final DBS image.

Effect of the present invention can be further illustrated by following simulation experiments:

1) Simulation conditions:

Obtain the measured data of the radar irradiation of the selected terrain, intercept the data of the first 128 pulses, and perform DBS imaging based on FFT transformation and DBS imaging based on SPICE transformation of the present invention respectively.

2) Simulation content and result analysis:

1. Draw the range-Doppler diagram after FFT transformation and SPICE transformation respectively, as shown in Fig. 2a and Fig. 2b.

It can be seen from Fig. 2a that the number of radar transmission pulses used in DBS imaging based on FFT transform is small, and the strong points in the figure appear to diffuse, resulting in a blurred overall effect of the range-Doppler map, especially when two When two strong points are relatively close to each other, they will be blurred together, which will affect the later processing.

It can be seen from Figure 2b that the requirements for the number of radar transmission pulses are not high when performing DBS imaging based on SPICE transformation, so a better DBS imaging effect has been achieved when the number of radar transmission pulses is small. The energy of the strong points is relatively concentrated, there is no serious diffusion phenomenon, and the strong points that are close to each other can be clearly separated.

2. Draw the section diagrams of the range dimension of the range-Doppler map after FFT transformation and SPICE transformation respectively, as shown in Fig. 3a and Fig. 3b.

It can be seen from Figure 3a and Figure 3b that the overall trend of the curves in the figure is completely consistent, but the amplitude of the main lobe and the side lobe area outside the target area in Figure 3b are both lower than those in Figure 3a. It is close to zero, and the amplitude peak value in Figure 3b is also relatively high, indicating that the data processed by SPICE transformation has low sidelobe energy, and there is no obvious leakage of mainlobe energy.

3. Draw the DBS imaging results based on FFT transformation and SPICE transformation respectively.

As can be seen from Fig. 4a and Fig. 4b, compared with the DBS imaging result based on FFT transformation, the DBS imaging result based on SPICE transformation is clearer, and the strong points are more obvious, which fully illustrates the DBS transformation based on SPICE transformation of the present invention Effectiveness of imaging methods.

Obviously, those skilled in the art can carry out various modifications and variations to the present invention without departing from the spirit and scope of the present invention; Like this, if these modifications and variations of the present invention belong to the scope of the claims of the present invention and equivalent technologies thereof, It is intended that the present invention also encompasses such changes and modifications.

Claims (5)

1. a kind of airborne radar high-resolution DBS imaging methods based on SPICE, it is characterised in that comprise the following steps：

Step 1, set airborne radar reception echo-signal as For time of i-th of range gate Ripple signal；In the carrier aircraft coordinate system that carrier aircraft is reference origin, to the echo-signal of airborne radar receptionCarried out in distance dimension Process of pulse-compression, obtain echo-signal y, the y=[y after pulse pressure processing₁..., y_i..., y_M], y_iFor i-th after pulse pressure The echo-signal of range gate；According to the echo-signal y of i-th of range gate after pulse pressure_iThe land clutter for establishing i-th of range gate returns Ripple signal x_iSignal model；Wherein, the echo-signal y of i-th of range gate after pulse pressure_iDimension be N × 1, N is airborne thunder Up to the umber of pulse of transmitting, i=1,2 ..., M, M be range gate number；

Step 2, the echo-signal y of i-th of range gate after pulse pressure is asked for_iCovariance matrix R_i；

Step 3, according to the echo-signal y of i-th of range gate after pulse pressure_iCovariance matrix R_i, provide and solve i-th of distance The land clutter echo-signal x of door_iPerformance number Optimized model：The ground for solving i-th of range gate is miscellaneous Ripple echo-signal x_iPerformance number Optimized modelObtain the land clutter echo-signal of i-th of range gate x_iK-th of performance number p_{I, k}；Wherein, k=1,2 ..., 2N, N be Doppler's port number,Square of F norms is sought in expression, on Mark H and represent conjugate transposition；

Step 4, by the land clutter echo-signal x of i-th of range gate_iTop n performance number be arranged in order, form i-th of range gate Land clutter echo-signal x_iPower vector p_i, p_i=[p_{I, 1}, p_{I, 2}..., p_{I, N}]^T；And then obtain the work(of all M range gates Rate matrix P, P=[p₁, p₂..., p_M], the power matrix P of all M range gates is final airborne radar echo data square Battle array；

Step 5, each range gate corresponding to element in final airborne radar echo data matrix is converted into corresponding oblique distance, Each Doppler frequency corresponding to element in final airborne radar echo data matrix is converted into corresponding azimuth, and will The oblique distance and azimuth are changed to earth coordinates by carrier aircraft coordinate system, then will be every in final airborne radar echo data matrix Pixel value of the individual element as correspondence position in earth coordinates, obtain final DBS images.

2. the airborne radar high-resolution DBS imaging methods based on SPICE as claimed in claim 1, it is characterised in that step 1 In, the land clutter echo-signal x of i-th of range gate_iSignal model be：

y_i=Bx_i+e

Wherein, B is time domain steering vector matrix, and its N number of row vector corresponds to the time domain steering vector of N number of 1 different × N-dimensional, e It is noise signal or interference signal, its dimension is N × 1.

3. the airborne radar high-resolution DBS imaging methods based on SPICE as claimed in claim 1, it is characterised in that step 2 In, the echo-signal y of i-th of range gate after the pulse pressure_iCovariance matrix R_iFor：

Wherein, A=[B I_N], B is time domain steering vector matrix, and its N number of row vector corresponds to the time domain of N number of 1 different × N-dimensional Steering vector, I_NFor N × N unit matrix, P_iIt is the land clutter echo-signal x of i-th of range gate_iPower matrix, be one Diagonal matrix, k-th of element p on its diagonal_{I, k}For the land clutter echo-signal x of i-th of range gate_iK-th of power Value, k=1,2 ..., 2N, subscript H represent conjugate transposition.

4. the airborne radar high-resolution DBS imaging methods based on SPICE as claimed in claim 1, it is characterised in that step 3 In, the land clutter echo-signal x for solving i-th of range gate_iThe Optimized model of performance number be：

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Wherein, the mark of tr () representing matrix, C are a constant；

By the land clutter echo-signal x of i-th of range gate of the solution_iThe Optimized model of performance number simplified, obtain its letter Change form is：

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Wherein, w_kFor the land clutter echo-signal x of i-th of range gate_iK-th of power weights, its expression formula is：

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Wherein, b_kkIt is k-th of element on the diagonal of time domain steering vector matrix B.

5. the airborne radar high-resolution DBS imaging methods based on SPICE as claimed in claim 1, it is characterised in that step 3 In, the land clutter echo-signal x for solving i-th of range gate_iPerformance number Optimized modelIts Specifically sub-step is：

3.1 set l as iterations, and iterations l initial value is 1, sets the land clutter echo-signal x of i-th of range gate_i K-th of performance number p_{I, k}Initial value

3.2 calculate the land clutter echo-signal x of i-th of range gate of the l times iteration_iK-th of performance number

<mrow> <msubsup> <mi>p</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>l</mi> </msubsup> <mo>=</mo> <msubsup> <mi>p</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>k</mi> </mrow> <mrow> <mi>l</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo>|</mo> <mrow> <msubsup> <mi>a</mi> <mi>k</mi> <mi>H</mi> </msubsup> <msubsup> <mi>R</mi> <mi>i</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <msub> <mi>y</mi> <mi>i</mi> </msub> </mrow> <mo>|</mo> </mrow> <mo>/</mo> <msqrt> <msub> <mi>w</mi> <mi>k</mi> </msub> </msqrt> </mrow>

Wherein, a_kArranged for the kth of matrix A, A=[B I_N], B is time domain steering vector matrix, w_kGround for i-th of range gate is miscellaneous Ripple echo-signal x_iK-th of power weights, its expression formula is：

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Wherein, b_kkIt is k-th of element on the diagonal of time domain steering vector matrix B；

If the land clutter echo-signal x of i-th of range gate of 3.3 the l times iteration_iK-th of performance numberWith the l-1 times repeatedly The land clutter echo-signal x of i-th of range gate in generation_iK-th of performance numberPoor absolute valueMore than setting Value ε, setting value ε value level off to 0, then make iterations l increase by 1, return to step 3.2,

If the land clutter echo-signal x of i-th of range gate of the l times iteration_iK-th of performance numberWith the l-1 times iteration I-th of range gate land clutter echo-signal x_iK-th of performance numberPoor absolute valueIt is less than or equal to Setting value ε, then by the land clutter echo-signal x of i-th of range gate of the l times iteration_iK-th of performance numberAs i-th The land clutter echo-signal x of range gate_iK-th of performance number p_{I, k}。