High-orbit high-resolution staring imaging method and system based on electromagnetic momentum information

Abstract

The present invention discloses a high-orbit high-resolution staring imaging method and system based on electromagnetic momentum information, wherein the method comprises the following steps: Step 1: The transmitter of the satellite radar generates an antenna pattern under the action of the array antenna element feeding amplitude and phase modulation, and transmits a pulse signal to the target imaging area with a preset period through the antenna pattern; Step 2: The receiver of the satellite radar receives the echo signal reflected by each scattering unit divided into the target imaging area through the array antenna, and performs pulse compression on the echo signal in the range direction to obtain a one-dimensional range image; Step 3: Obtain the echo signal after pulse compression under the condition of the pulse signal emitted in the i-th period; Step 4: Convert the expression of the echo signal after pulse compression into a matrix equation, perform matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on the equidistant line, and obtain a two-dimensional image. The present invention realizes azimuth high-resolution staring imaging observation.

Description

Technical Field

[0001] The present invention belongs to the field of microwave imaging technology and radar detection technology, and in particular to a high-orbit high-resolution staring imaging method and system based on electromagnetic momentum information. Background Art

[0002] At present, microwave high-resolution imaging satellites usually adopt the SAR system, which requires relative motion between the sensor and the ground object, and has certain limitations in use; the revisit time of low-orbit SAR is several days, and the revisit time of high-orbit SAR is hourly, which cannot meet the requirements of real-time high-quality imaging detection guarantee.

[0003] As the detection medium of radar systems, electromagnetic waves have long been the focus of attention for their wave properties such as energy, frequency, bandwidth and polarization, while the momentum properties of matter have hardly been used in fields such as radar imaging detection.

[0004] The azimuth resolution or angular resolution of traditional real aperture radar is inversely proportional to the aperture of the radar antenna, which will result in the need for spaceborne radar satellites to obtain better azimuth resolution or angular resolution. The synthetic aperture radar system solves the problem of improving azimuth resolution through the relative motion between the target and the radar. Although it can make up for the shortcomings of the traditional real aperture radar system, it requires relative motion between the radar and the ground object, and has certain limitations in use. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a high-orbit high-resolution staring imaging method and system based on electromagnetic momentum information, which changes the energy distribution, transmission characteristics and interaction relationship of radar electromagnetic waves in space through electromagnetic momentum control, thereby realizing azimuth high-resolution staring imaging observation.

[0006] The object of the present invention is achieved through the following technical scheme: a high-orbit high-resolution staring imaging method based on electromagnetic momentum information, the method comprising the following steps: step one: the transmitter of the satellite radar generates an antenna pattern under the action of the array antenna element feeding amplitude and phase modulation, and transmits a pulse signal to the target imaging area with a preset period through the antenna pattern; step two: the receiver of the satellite radar receives the echo signal reflected by each scattering unit divided into the target imaging area through the array antenna, and performs pulse compression on the echo signal in the distance direction to obtain a one-dimensional range image; step three: obtain the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th period; step four: convert the expression of the echo signal after pulse compression into a matrix equation, perform matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on the equidistant line, and obtain a two-dimensional image.

[0007] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step one, the antenna radiation pattern is a plurality of half-power beam widths that remain unchanged but the spatial electromagnetic momentum distribution is different.

[0008] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step 2, each distance resolution unit in the one-dimensional range image is formed by the superposition of echoes of scattering units on the equidistant line.

[0009] In the high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step 2, the target imaging area is divided into a plurality of grids, each grid being a scattering unit; wherein the size of each grid is equal to the resolution of the satellite radar;

[0010] In the high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step 3, the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th cycle is obtained by the following formula:

[0011]

[0012] Among them, C i (R) is the superposition of the scattering intensities of all scattering units on the equidistant line R of the i-th period, c j (R) is the scattering intensity of the jth scattering unit at the range gate R, w ij is the electromagnetic momentum information of the jth scattering unit projected onto the range gate R in the ith period, j is the serial number of the scattering unit, and N is the total number of scattering units.

[0013] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step 4, the matrix equation is:

[0014]

[0015] Among them, W is the observation matrix, the vector is the scattering intensity of the scattering unit on the equidistant line to be determined, and C is a vector.

[0016] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, in step one, each pulse signal corresponds to a kind of space electromagnetic momentum information, and each pulse emitted by the satellite radar transmitter has unique space electromagnetic momentum information.

[0017] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, the number of rows of the observation matrix is ​​equal to the number of periods, and the number of columns of the observation matrix is ​​equal to the number of scattering units to be resolved in azimuth.

[0018] In the above-mentioned high-orbit high-resolution staring imaging method based on electromagnetic momentum information, the observation matrix W is full rank, and the number of periods is equal to the number of scattering units.

[0019] A high-orbit high-resolution staring imaging system based on electromagnetic momentum information comprises: a first module for performing pulse compression on an echo signal in the range direction to obtain a one-dimensional range image; a second module for obtaining an echo signal after pulse compression under the condition of a pulse signal emitted in the ith cycle; and a third module for converting an expression of the echo signal after pulse compression into a matrix equation, performing matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on an equidistant line, and obtaining a two-dimensional image.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention changes the energy distribution, transmission characteristics and interaction relationship of electromagnetic waves in space with the target through momentum control, thereby solving the problem that the synthetic aperture radar satellite system requires relative motion imaging between the target and the satellite platform;

[0022] (2) The present invention can achieve high temporal resolution, high spatial resolution, all-weather and all-day imaging detection capabilities through high-orbit staring imaging based on electromagnetic momentum information;

[0023] (3) The present invention adopts a high-orbit geostationary orbit for staring imaging, which can realize efficient real-time observation of the area of ​​concern. Three to four microwave staring imaging satellites are deployed in the geostationary orbit, which has the ability to image any area in the world at any time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0025] Figure 1 is a schematic diagram of the satellite-ground geometric relationship provided by an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the geometric relationship of the inclined plane and the echo provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0027] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] The high-orbit high-resolution staring imaging method based on electromagnetic momentum information proposed in this embodiment still uses the traditional "broadband signal + pulse compression" mechanism in the range direction, and uses multiple unrelated or weakly related low-resolution observation results to synthesize a high-resolution imaging result in the azimuth direction. The main steps are:

[0029] Step 1: Under the high-orbit geostationary orbit staring condition, the satellite-ground geometric relationship is as follows: Figure 1 As shown, the satellite-borne radar transmitter generates multiple half-power beam widths that are basically unchanged through the amplitude and phase modulation of the array antenna element feed, but with different directional patterns of spatial electromagnetic momentum distribution, which are mainly reflected in the amplitude and phase of the radiation directional pattern. These directional patterns are then used to transmit pulse signals to the target imaging area at a certain period, so that each pulse radiates a different electric field distribution to the target, but does not change the form of the pulse signal incident on each scattering unit. In other words, each pulse of the radar system corresponds to a type of electromagnetic momentum information, and each pulse emitted by the radar system has "unique" electromagnetic momentum information. "Unique" here means that the electromagnetic momentum information of each pulse is unrelated or weakly correlated with each other;

[0030] Step 2: The satellite-borne radar switches the antenna transceiver switch to make the radar work in the receiving state. The radar receives the echo signal reflected by each scattering unit in the target imaging area. The echo signal is pulse compressed in the range direction to obtain a one-dimensional range image, such as Figure 2 As shown in the figure, each distance resolution unit is composed of the echoes of the scattering units on the equidistant line, and the echo intensity of each scattering unit is related to the scattering characteristics of the scattering unit itself on the one hand, and the electromagnetic momentum information of the transmitted signal on the other hand. When the power of the transmitted signal is constant, the power radiated by the radar to different scattering units is determined by the electromagnetic momentum information of the transmitted signal, so it can be described by the following expression.

[0031]

[0032] Among them, c j (R) is the scattering intensity of the scattering unit at the range gate R, w jis the electromagnetic momentum information of each scattering unit projected onto the range gate R, and C(R) is the superposition of the scattering intensities of all scattering units on the equidistant line R or can be understood as the result at the range gate R after pulse compression.

[0033] Step 3: From the above expression, we can know that when the scene is fixed, that is, the scattering characteristics of each scattering unit in the scene remain unchanged, when the incident electromagnetic momentum information of the pattern changes, the C(R) after pulse compression will also change. According to the physical process of staring imaging, the electromagnetic momentum information of the transmitted signal will continue to change with the emission of the pulse signal, so the echo signal after pulse compression obtained under the pulse signal condition of the i-th cycle can be written as:

[0034]

[0035] The scattering intensities of all scattering units on the equidistant line R of the i-th cycle are superimposed. In the above formula, the subscript i represents the cycle count. Since the scattering characteristics of the scattering unit will not change with the emission of the pulse under the staring condition, c j (R) has nothing to do with pulse emission and has no subscript i. Obviously, the above formula can be written in matrix form as follows:

[0036]

[0037] Where W is the electromagnetic momentum information w ij The number of rows in this matrix is ​​equal to the number of periods, and the number of columns is equal to the number of scattering units to be resolved in the azimuth direction. is the scattering unit on the equidistant line to be determined, and the vector C on the right side of the equation is given by C i (R) is the result at the range gate R obtained after the echo signal of each period is compressed.

[0038] Step 4: It can be seen from the expression that in order to solve the matrix equation, the observation matrix W should be full rank in theory, and the number of periods (that is, the number of rows of W) should be at least equal to the number of scattering units. Under this condition, the scattering intensity c of each scattering unit on the equidistant line can be obtained by matrix inversion. j (R), that is, the scattering units originally mixed together on the equidistant line are separated to obtain a two-dimensional image, so that the azimuth image is obtained on the basis of the one-dimensional range image, thereby realizing two-dimensional high-resolution microwave staring images in the range and azimuth directions.

[0039] The present embodiment also provides a high-orbit high-resolution staring imaging system based on electromagnetic momentum information, the system comprising: a first module, used to perform pulse compression on the echo signal in the range direction to obtain a one-dimensional range image; a second module, used to obtain the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th cycle; a third module, used to convert the expression of the echo signal after pulse compression into a matrix equation, perform matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on the equidistant line, and obtain a two-dimensional image.

[0040] This embodiment utilizes a high-orbit satellite platform in combination with electromagnetic momentum detection. By changing the energy distribution, transmission characteristics and interaction relationship of electromagnetic waves in space through momentum control, it can achieve high temporal resolution, high spatial resolution, all-weather and all-day imaging detection capabilities, effectively make up for the deficiencies of the existing SAR imaging system, and truly realize real-time observation of areas of concern. Three to four microwave staring imaging satellites are deployed in geostationary orbit, which have the ability to image any area in the world at any time; solve the contradictions of traditional radar detection mechanisms, realize high-resolution imaging of targets and video observation of moving targets; enrich and improve the physical principles of the interaction between electromagnetic waves and matter, and form a more generalized electromagnetic detection theoretical system.

[0041] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A high-orbit high-resolution staring imaging method based on electromagnetic momentum information, characterized in that: The method comprises the following steps: Step 1: The transmitter of the satellite radar generates an antenna pattern under the action of the array antenna element feeding amplitude and phase modulation, and transmits a pulse signal to the target imaging area with a preset period; Step 2: The receiver of the satellite radar receives the echo signals reflected by each scattering unit divided in the target imaging area through the array antenna, and performs range pulse compression on the echo signals to obtain a one-dimensional range image; Step 3: Obtain the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th cycle; Step 4: convert the expression of the echo signal after pulse compression into a matrix equation, perform matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on the equidistant line, and obtain a two-dimensional image; In step 1, the antenna pattern is a plurality of half-power beam widths with constant but different spatial electromagnetic momentum distributions; In step 2, each range resolution unit in the one-dimensional range image is formed by superposition of echoes of scattering units on the equidistant line; In step 3, the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th cycle is obtained by the following formula: Among them, C i (R) is the superposition of the scattering intensities of all scattering units on the equidistant line R of the i-th period, c j (R) is the scattering intensity of the jth scattering unit at the range gate R, w ij is the electromagnetic momentum information of the jth scattering unit projected to the range gate R in the i-th period, j is the serial number of the scattering unit, and N is the total number of scattering units; in step 4, the matrix equation is: Among them, W is the observation matrix, the vector is the scattering intensity of the scattering unit on the equidistant line to be determined, and C is a vector.

2. The high-orbit high-resolution staring imaging method based on electromagnetic momentum information according to claim 1 is characterized by: In step 2, the target imaging area is divided into a number of grids, each grid being a scattering unit; wherein the size of each grid is equal to the resolution of the satellite radar.

3. The high-orbit high-resolution staring imaging method based on electromagnetic momentum information according to claim 1 is characterized by: In step one, each pulse signal corresponds to a kind of space electromagnetic momentum information, and each pulse emitted by the transmitter of the satellite radar has unique space electromagnetic momentum information.

4. The high-orbit high-resolution staring imaging method based on electromagnetic momentum information according to claim 1 is characterized by: The number of rows of the measurement matrix is ​​equal to the number of periods, and the number of columns of the measurement matrix is ​​equal to the number of scattering elements to be resolved in azimuth.

5. The high-orbit high-resolution staring imaging method based on electromagnetic momentum information according to claim 1 is characterized by: The measurement matrix W is of full rank and the number of periods is equal to the number of scattering elements.

6. A system for high-orbit high-resolution staring imaging method based on the electromagnetic momentum information of claim 1, characterized in that include: The first module is used to perform range pulse compression on the echo signal to obtain a one-dimensional range image; The second module is used to obtain the echo signal after pulse compression under the condition of the pulse signal transmitted in the i-th cycle; The third module is used to convert the expression of the echo signal after pulse compression into a matrix equation, perform matrix inversion on the matrix equation to obtain the scattering intensity of each scattering unit on the equidistant line, and obtain a two-dimensional image.

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