CN116466306A - Satellite-borne SAR accurate interference method based on environmental cognition - Google Patents

Abstract

The invention discloses a satellite-borne SAR accurate interference method based on environmental cognition, which comprises the following steps: s1: acquiring image intensity information of an enemy plane after imaging a protection scene according to the SAR image database; s2: introducing a super-pixel segmentation technology, and dividing a target scene into subareas according to image features; s3: calculating the position and intensity of the interference signal required to be applied to the region based on the position information and intensity information of the sub-region; s4: acquiring coverage range of an interference signal; s5: the distance direction modulation factor and the azimuth modulation factor are designed according to the coverage range of the interference signal, so that the interference signal has two-dimensional accurate controllable characteristics; s6: and generating interference signals with different characteristics according to different subareas, modulating the interference signals by an interference machine and forwarding the interference signals. According to the method, optimal interference power distribution can be realized according to the image intensity information of the protection scene, and the optimal interference effect can be achieved with the minimum cost. The method has wide application prospect in practical application.

Description

Satellite-borne SAR accurate interference method based on environmental cognition

Technical Field

The invention belongs to the technical field of SAR signal processing, and particularly relates to a satellite-borne SAR accurate interference method based on environmental cognition.

Background

SAR plays a vital role in information acquisition in severe weather and in complex environments where optical and infrared detection systems cannot be used due to the mapping capability over the whole day, around the clock, remotely and over a wide range, and is therefore widely used in various fields. However, in order to avoid malicious investigation of own important scene information by the enemy SAR, research on SAR interference techniques needs to be developed. Generally, SAR interference techniques can be classified into suppression interference and spoofing interference according to their modes of operation. Conventional suppression interference uses gaussian noise signals to cover the useful signal to prevent the SAR from acquiring accurate target information. The spoofing interference mainly modulates and forwards intercepted radar echoes, so that the enemy radar cannot accurately detect targets and estimate parameters. Since the suppression of interference is relatively easy to implement, it has become a common form of SAR interference.

In order to realize large-scale interference on SAR imaging scenes, the currently common interference suppression technology is mainly noise suppression interference. Since noise-like suppression interference cannot achieve two-dimensional processing gain during SAR imaging, this technique requires higher jammer transmit power, which will also greatly increase the risk of jammer exposure. At present, how to effectively reduce the transmitting power of an jammer under the condition of ensuring the interference performance is the key point of the current research.

Disclosure of Invention

In order to solve the problems, the invention provides a satellite-borne SAR accurate interference method based on environmental cognition. Compared with noise suppression interference technology, the method can obtain higher two-dimensional processing gain in the imaging process. In addition, the method can divide the scene environment so as to adaptively distribute interference energy, which greatly saves the transmitting power of the jammer and reduces the exposure probability of the jammer.

The invention discloses an environment cognition-based satellite-borne SAR accurate interference method, which comprises the following steps:

a satellite-borne SAR accurate interference method based on environmental cognition comprises the following steps:

s1: according to the SAR image database, acquiring the image intensity of the enemy plane after imaging the protection scene;

s2: to reduce the calculation complexity of the interference signal generation, carrying out subarea division on the protection scene;

s3: calculating the position and the intensity of the interference signals required to be applied to each sub-region based on the position and the intensity of each sub-region obtained after division;

s4: the extension degree of each sub-region in the distance direction and the azimuth direction is calculated, so that the coverage range of the interference signal is obtained;

s5: the distance direction modulation factor and the azimuth modulation factor are designed according to the coverage range of the interference signal, so that the interference signal has two-dimensional accurate controllable characteristics;

s6: and generating interference signals with different characteristics according to each subarea, modulating the interference signals by an interference machine and forwarding the interference signals.

Preferably, in step S1:

suppose that the protection scene contains n _r ×n _a The image intensity of the enemy machine after imaging the protection scene is expressed as:

σ＝{σ _p,q |1≤p≤n _r ,1≤q≤n _a }。

preferably, in step S2:

dividing the protection scene by adopting a simple linear iterative clustering SLIC technology to obtain a divided subarea D ₁ ,D ₂ ,…,D _M 。

Preferably, in step S3:

sub-region D _m The maximum value of the medium intensity is expressed asPreliminary generation of interference scene J _m M= (1, 2,3, … …, M), interference scenario J _m The intensity of (c) is expressed as:

in sigma _p,q Representing subregion D _m Is used as a material for the heat exchanger,representing the strength of false targets in the interference scenario, to reduce the complexity of signal modulation, the interference scenario J _m Equivalent as false point target J _m Will sub-region D _m The size of (2) is marked-> For distance (I)>Is the azimuth;

this false point target J _m Strength sigma of (2) _m Expressed as:

wherein f _s ，F _a C and v _a Respectively representing the distance sampling rate, the azimuth sampling rate, the light speed and the flying speed, wherein mean (·) represents a mean function;

this false point target J _m Position L of (2) _m ＝(x _m ,y _m ) Expressed as:

wherein min {.cndot } and max {.cndot }, respectively represent minimum and maximum functions, (x) _p,q ,y _p,q ) Representing subregion D _m Coordinates of the medium scatterer;

obtaining the interference signals required to be applied to each subareaPosition L _m And intensity sigma _m 。

Preferably, in step S4:

from step S3, the extent of the sub-region in the distance and azimuth directions is expressed asAnd->To fully protect the scene information of the subarea, a false target J _m The generated interference signal needs to cover completely the sub-area scene range +.>

Preferably, in step S5:

adopting a two-dimensional precise and controllable technology to ensure false target J _m The coverage of the generated interference signal is justThe distance modulation factor and the azimuth modulation factor are designed and respectively expressed as:

wherein K is _r ，And->Respectively representing the distance chirp rate, the distance chirp rate error and the azimuth chirp rate error when +.>The relationship between the chirp rate error and the defocus level is expressed as:

wherein T is _p ，λ，R _i And T _a Respectively, pulse width, wavelength, shortest skew between false target and SAR, and false target J _m Is a synthetic aperture time of (a).

Preferably, step S6:

according to the distance-direction modulation factor and the azimuth-direction modulation factor designed in step S5, the modulation function applied to the intercepted signal is expressed as:

wherein f _c ，f _r ，x _i T and eta represent carrier frequency, range frequency, false target azimuth position, fast and slow times, Δt, respectively _ij (eta) is the time delay difference between the echo of the jammer and the false target echo, omega _r (t) and ω _a (η) represents the distance-wise envelope and the azimuth-wise envelope, respectively.

The beneficial effects are that:

compared with the prior art, the satellite-borne SAR accurate interference method based on the environmental cognition has the beneficial effects that: on one hand, the method can obtain two-dimensional signal processing gain and accurately control the coverage range of the interference signal. On the other hand, the method can realize optimal interference energy distribution according to the protection scene, can greatly reduce the transmitting power of the jammer and reduce the exposure probability of the jammer.

Drawings

FIG. 1 is a flow chart of an implementation of the proposed interference technique;

FIG. 2 is a determined protection scene image;

fig. 3 (a) is an interference result obtained using a noise interference method at an interference-to-signal ratio of 0 dB;

fig. 3 (b) is an interference result obtained using a noise interference method at an interference-to-signal ratio of 5 dB;

fig. 3 (c) is an interference result obtained using a noise interference method at an interference-to-signal ratio of 10 dB;

fig. 4 (a) is the interference result obtained using the proposed method at a signal-to-interference ratio of 0 dB;

fig. 4 (b) is the interference result obtained using the proposed method at a signal-to-interference ratio of 5 dB;

fig. 4 (c) is the interference result obtained using the proposed method at a signal-to-interference ratio of 10 dB;

fig. 5 is a schematic overall flow diagram of the present invention.

Detailed Description

The invention provides a satellite-borne SAR accurate interference method based on environmental cognition, which is described in detail below with reference to the accompanying drawings.

Compared with the traditional interference method, the satellite-borne SAR accurate interference method based on the environmental cognition provided by the invention mainly explores how to utilize the environmental information to carry out self-adaptive interference energy distribution so as to further save the transmitting power of an interference machine. The method mainly comprises the following steps:

s1: acquiring image intensity information of an enemy plane after imaging a protection scene according to the SAR image database;

suppose that the protection scene contains n _r ×n _a The scattering points, and the corresponding image intensity information can be expressed as:

σ＝{σ _p,q |1≤p≤n _r ,1≤q≤n _a }

s2: in order to reduce the calculation complexity of the interference signal generation, a super-pixel segmentation technology is introduced, and the target scene is subjected to sub-region division according to the image characteristics;

the SAR image is segmented by adopting a Simple Linear Iterative Clustering (SLIC) technology, and the technology is simple to realize and only needs to set two parameters of the number of the segmented regions and the measurement distance. The distance measurement needs to be performed by comprehensively considering the space distance and the color distance. In general, the spatial distance and the color distance can be calculated as:

in the formula, [ l ] _i ,a _i ,b _i ,x _i ,y _i ]Representing the cluster center, [ l ] when image segmentation is performed _j ,a _j ,b _j ,x _j ,y _j ]Representing coordinates of the pixels involved in the search, where [ l, a, b]Represents color values, [ x, y ]]Representing the position coordinates.

Further, the distance metric may be expressed as:

where d and d represent the calculated color distance and spatial distance, respectively, m represents a set constant (normalizing the color distance),(N and k are the number of pixels of the image and the number of divided sub-regions, respectively). In actual processing, the above formula can be generally simplified as:

s3: calculating the position and intensity of the interference signal required to be applied to the region based on the position information and intensity information of the sub-region;

assume that the divided sub-regions are denoted as D ₁ ,D ₂ ,||,D _M Sub-region D _m The medium scatterer intensity maximum can be expressed asCan initially generate an interference scene J _m The corresponding amplitude information may be expressed as:

in sigma _p,q Representing subregion D _m Is used for the scattering body intensity. In order to reduce the complexity of the signal modulation,can interfere with scene J _m Equivalent as false point target J _m Will sub-region D _m The size of (2) is recorded asThis false point target J _m Strength sigma of (2) _m Can be expressed as:

wherein f _s ，F _a C and v _a The distance sampling rate, the azimuth sampling rate, the light velocity and the flying speed are respectively represented. mean (·) represents the averaging function. In addition, the location L of the false object _m ＝(x _m ,y _m ) Can be expressed as:

wherein min {.cndot } and max {.cndot }, respectively represent minimum and maximum functions, (x) _p,q ,y _p,q ) Representing subregion D _m Coordinates of the medium scatterer.

S4: the extension degree of each subarea in the distance direction and the azimuth direction is calculated, so that the coverage range of the interference signal is obtained;

from step S3, the extent of the sub-regions in the distance and azimuth directions can be expressed asAnd->To fully protect the scene information of the subarea, a false target J _m The resulting interfering signal needs to completely cover the sub-area scene. Therefore, it is necessary to determine +.> Specific values of (3).

S5: the distance and azimuth modulation factors are designed according to the coverage range of the interference signal, so that the interference signal has two-dimensional accurate controllable characteristics

By adopting a two-dimensional precise and controllable technology, two-dimensional mismatch of interference signals is caused by fast time and slow time modulation, and the coverage range of the interference signals generated by false targets is ensured to be exactlyTo realize two-dimensional precise controllable modulation, a distance-direction modulation factor and an azimuth-direction modulation factor need to be designed, which can be expressed as follows:

wherein K is _r ，And->The range slope, range slope error and azimuth slope error are represented, respectively. The range and azimuth chirp rate errors directly determine the degree of defocus in the range and azimuth directions. When->The relationship between the chirp rate error and the defocus level can be expressed as:

wherein T is _p ，λ，R _i And T _a Respectively representPulse width, wavelength, shortest skew between false target and SAR, and synthetic aperture time of false target.

S6: and generating interference signals with different characteristics according to different subareas, modulating the interference signals by an interference machine and forwarding the interference signals.

The modulation function applied to the intercepted signal according to the distance-wise and azimuth-wise modulation factors designed in step S5 can be expressed as:

wherein f _c ，f _r ，x _i T and eta represent carrier frequency, range frequency, false target azimuth position, fast and slow times, Δt, respectively _ij (eta) is the time delay difference between the echo of the jammer and the false target echo, omega _r (t) and ω _a (η) represents the distance-wise envelope and the azimuth-wise envelope, respectively. The modulation function described above can be divided into three parts, imaging position modulation, distance-wise mismatch modulation, and azimuth-wise mismatch modulation. By adjusting the distance modulation factor gamma _r And an azimuthal modulation factor gamma _a The coverage area of the interference signal can be changed, and the final interference effect is achieved. The whole technical flow is shown in figure 1.

The performance of the proposed method will be verified by a face target simulation experiment, the specific simulation experiment parameters being shown in table 1. The imaging result of the high-score No. 3 (GF-3) satellite on the combined urban area is selected to evaluate the large-range interference effect of the method, as shown in fig. 2. Fig. 3 and 4 show the comparison between the noise interference method and the proposed method, with the signal to interference ratio increasing from 0dB to 5dB to 10dB in sequence. As can be seen from fig. 3 and 4, the contrast information of the protection area is seriously deteriorated with the increase of the interference-signal ratio, and the detailed information of the object is not obvious. Furthermore, it is evident that current noise interference methods do not completely submerge the protection scenario in the interfering signal compared to the proposed method. Some important objects, such as buildings, are still clearly observable by enemy SAR. To quantitatively evaluate the interference performance of both methods, three regions in fig. 3 and 4 were selected to evaluate their structural similarity (StructureSimilarity, SSIM) values. In general, the smaller the SSIM value, the better the interference effect. Table 2 lists SSIM results for different regions and different interference to signal ratios. In this table, the SSIM difference between the above methods can reach 0.385 (in the case of a region 2 interference to signal ratio of 10 dB), significantly demonstrating the effectiveness and superiority of the proposed method.

TABLE 1 Main parameters to which the simulation data relate

Table 2 SSIM values for different methods at different interference to signal ratios

In practical situations, the jammer transmit power determines the jammer performance. A significant advantage of the proposed method is that the required interference power can be reduced while guaranteeing equivalent interference performance. To illustrate the extent to which the proposed method reduces interference power, the interference-to-signal ratio required by the above method to obtain the same SSIM value can be calculated. Referring to the processing results in fig. 3 and 4, table 3 lists the degree of interference power reduction using the proposed method. Note that the SSIM difference between the two methods is less than 0.01 in order to obtain equivalent processing performance. As shown in table 3, the interference power can be significantly reduced by about 90% using the proposed technique. Thus reducing the exposure probability of the disturbance.

TABLE 3 degree of interference power reduction for the proposed method while ensuring the same interference performance

The foregoing is only a preferred embodiment of the invention, it being noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.

Claims (7)

1. A satellite-borne SAR accurate interference method based on environmental cognition is characterized in that: the method comprises the following steps:

s1: according to the SAR image database, acquiring the image intensity of the enemy plane after imaging the protection scene;

s2: to reduce the calculation complexity of the interference signal generation, carrying out subarea division on the protection scene;

s3: calculating the position and the intensity of the interference signals required to be applied to each sub-region based on the position and the intensity of each sub-region obtained after division;

s4: the extension degree of each sub-region in the distance direction and the azimuth direction is calculated, so that the coverage range of the interference signal is obtained;

s5: the distance direction modulation factor and the azimuth modulation factor are designed according to the coverage range of the interference signal, so that the interference signal has two-dimensional accurate controllable characteristics;

s6: and generating interference signals with different characteristics according to each subarea, modulating the interference signals by an interference machine and forwarding the interference signals.

2. The environmental awareness-based satellite-borne SAR accurate interference method of claim 1, wherein the method comprises the following steps: in step S1:

suppose that the protection scene contains n _r ×n _a The image intensity of the enemy machine after imaging the protection scene is expressed as:

σ＝{σ _p,q 1≤p≤n _r ,1≤q≤n _a }。

3. the environmental awareness-based satellite-borne SAR accurate interference method of claim 1, wherein the method comprises the following steps: in step S2:

dividing the protection scene by adopting a simple linear iterative clustering SLIC technology to obtain a divided subarea D ₁ ,D ₂ ,…,D _M 。

4. The method for satellite-borne SAR accurate interference based on environmental awareness as set forth in claim 3, wherein: in step S3:

sub-region D _m The maximum value of the medium intensity is expressed asPreliminary generation of interference scene J _m M= (1, 2,3, … …, M), interference scenario J _m The intensity of (c) is expressed as:

in sigma _p,q Representing subregion D _m Is used as a material for the heat exchanger,representing the strength of false targets in the interference scenario, to reduce the complexity of signal modulation, the interference scenario J _m Equivalent as false point target J _m Will sub-region D _m The size of (2) is marked-> In order to be a distance from each other,is the azimuth;

this false point target J _m Strength sigma of (2) _m Expressed as:

wherein f _s ，F _a C and v _a Respectively represent the sampling rate and the azimuth of the distance directionTo the sampling rate, the speed of light and the flying speed, mean (·) represents the mean function;

this false point target J _m Position L of (2) _m ＝(x _m ,y _m ) Expressed as:

wherein min {.cndot } and max {.cndot }, respectively represent minimum and maximum functions, (x) _p,q ,y _p,q ) Representing subregion D _m Coordinates of the medium scatterer;

obtaining the position L of the interference signal required to be applied to each subarea _m And intensity sigma _m 。

5. The environmental awareness-based satellite-borne SAR accurate interference method as set forth in claim 4, wherein: in step S4:

from step S3, the extent of the sub-region in the distance and azimuth directions is expressed asAnd->To fully protect the scene information of the subarea, a false target J _m The generated interference signal needs to cover completely the sub-area scene range +.>

6. The environmental awareness-based satellite-borne SAR precision interference method of claim 4 or 5, wherein the method comprises the steps of: in step S5:

adopting a two-dimensional precise and controllable technology to ensure false target J _m The coverage of the generated interference signal is justThe distance modulation factor and the azimuth modulation factor are designed and respectively expressed as:

wherein K is _r ，And->Respectively represent a distance chirp rate, a distance chirp rate error and an azimuth chirp rate error whenThe relationship between the chirp rate error and the defocus level is expressed as:

wherein T is _p ，λ，R _i And T _a Respectively, pulse width, wavelength, shortest skew between false target and SAR, and false target J _m Is a synthetic aperture time of (a).

7. The environmental awareness-based satellite-borne SAR accurate interference method of claim 6, wherein the method comprises the following steps: in step S6:

according to the distance-direction modulation factor and the azimuth-direction modulation factor designed in step S5, the modulation function applied to the intercepted signal is expressed as:

wherein f _c ，f _r ，x _i T and eta represent carrier frequency, range frequency, false target azimuth position, fast and slow times, Δt, respectively _ij (eta) is the time delay difference between the echo of the jammer and the false target echo, omega _r (t) and ω _a (η) represents the distance-wise envelope and the azimuth-wise envelope, respectively.