KR102121474B1 - Sar and sar signal processor for squinted spotlight mode under nonlinear flight path and method thereof - Google Patents

Abstract

According to an embodiment of the present invention, when generating a SAR image to which FBPA is applied in an environment in which there is a distance due to a nonlinear flight trajectory and an altitude direction deviation, a local polar coordinate on a slope plane for each partial aperture is a distance direction of each slope plane, an aircraft flight It is possible to generate accurate SAR image for the target by applying BPA by converting the normal direction of the direction and inclined plane to the local Cartesian coordinate system.

Description

SAR signal processor and aircraft-mounted composite caliber radar and method for squint spotlight mode on nonlinear flight trajectories{SAR AND SAR SIGNAL PROCESSOR FOR SQUINTED SPOTLIGHT MODE UNDER NONLINEAR FLIGHT PATH AND METHOD THEREOF}

The present invention relates to a Synthetic Aperture Radar (SAR) on an aircraft, and more particularly, to an SAR signal processor for a squinted spotlight mode in a nonlinear flight trajectory and an aircraft-mounted synthetic caliber radar and method.

Generally, a Synthetic Aperture Radar (SAR) is a device that emits radio waves to the ground to create an image of the earth's surface, and sequentially radiates electromagnetic waves from the air to the ground or the ocean, and then the electromagnetic waves radiate to the curved surface of the ground or ocean. It refers to a radar system that creates a topographic map of the ground by first-come-first-served synthesis of the minute time difference that is reflected and returned.

In addition, a composite-diameter radar can use a back-projection algorithm (BPA) to generate SAR images.

BPA is a time-domain SAR (Synthetic Aperture Radar) image forming algorithm, which has the advantage that resolution and side lobe performance do not deteriorate even in a nonlinear flight trajectory where there is a large amount of fluctuation. It is well known that there is a disadvantage that it is very difficult to apply to the treatment.

개의 부분 구경(Sub- Aperture, SA)으로 나누고 각 부분 구경 동안에 지역 극좌표(local polar coordinate) 개념을 도입하여 표적 영역을 탐지함으로써 연산량 부담을 상당히 경감시키는 고속 역투영 알고리즘(Fast BPA : FBPA)이 제안되었다. In order to improve these shortcomings, the entire SAR image acquisition section (d) in the SAR mounted on the aircraft

It is proposed by Fast BPA (FBPA), which divides into four sub-apertures (SAs) and introduces the concept of local polar coordinates during each sub-aperture to significantly reduce the computational burden by detecting the target area. Became.

However, the existing FBPA can be implemented with a small amount of computation while satisfying the same performance as the BPA under the linear flight trajectory of an SAR-equipped aircraft, but the performance is improved when the aircraft's flight trajectory is not linear and fluctuations exist, resulting in nonlinear trajectories. There was a problem of deterioration. In addition, unlike the BPA, where the final image plane satisfies the same performance without any constraints on slope/ground, there is a restriction that the final image plane is a land plane rather than a ground plane.

To overcome this, an improvement technique for projecting onto a ground plane rather than an inclined plane has also been proposed, but it is a technique applicable only to linear flight trajectories, and in environments where fluctuations caused by nonlinear flight trajectories exist, the performance is only at the center point of the plane of the ground plane image formation. There was a problem that the performance deteriorated only as it was maintained and moved away from the center point.

(Patent literature)

Republic of Korea Registered Patent No. 10-1009967 (Registration Date January 14, 2011)

Accordingly, an embodiment of the present invention is to provide an SAR signal processor and a synthetic caliber radar and method mounted on an aircraft for a squint spotlight mode in a nonlinear flight trajectory.

A SAR signal processor according to an embodiment of the present invention as described above, using a radar signal that is reflected and received against a target region, a first coordinate calculator for calculating local polar coordinates for an inclined plane of each partial aperture, and the region A second coordinate calculator for converting the polar coordinates into all orthogonal coordinates on the entire orthogonal coordinate system using the distance direction, flight direction, and altitude direction of the aircraft that transmitted the radar signal, and the inclined distance on the inclined plane A third coordinate calculation unit for converting a direction, a flight direction of the aircraft and a normal direction of the inclined plane into a local orthogonal coordinate system on a local orthogonal coordinate system, and based on the regional orthogonal coordinates of the inclined plane of each partial aperture. It includes a SAR image generator for generating a SAR (Synthetic Aperture Radar) image for the target area.

In addition, the SAR image generation unit converts the transmission/reception position of the radar signal within each partial aperture into the local orthogonal coordinates, and the distance between the local orthogonal coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture. It is characterized by forming SAR images corresponding to local polar coordinates of the inclined plane of each partial aperture using.

In addition, the SAR image generating unit applies the SAR image by applying a back-projection algorithm (BPA) method to a local orthogonal coordinate with a point indicating an actual ground plane position of the inclined plane of each partial aperture based on the distance. It is characterized by forming.

In addition, the SAR image generating unit defines a reference position for forming a ground image for the target area on the entire Cartesian coordinate system, and the defined position is a local polar coordinate on an inclined plane based on the center position of each partial aperture. It is characterized in that it is converted to a system position, and all SAR images corresponding to the respective partial apertures are synthesized at a position in the local polar coordinate system to form a SAR image for the target area projected on the ground plane.

In addition, the SAR image generating unit is characterized by synthesizing all the SAR images by applying a two-dimensional interpolation (interpolation) method.

In addition, the position of transmission and reception of the radar signal is characterized in that it is distributed in non-linear trajectories within the respective partial apertures.

In addition, as an aircraft-mounted synthetic caliber radar according to an embodiment of the present invention, an antenna, a chirp signal generator that generates a wideband baseband chirp signal, and converts the baseband chirp signal to a radar signal to detect through the antenna A transmitter for transmitting to a target target region, a receiver for receiving a received signal reflected by the radar signal through the antenna, and converting the chirp signal into a baseband received signal, and using the baseband received signal An inclined plane for each partial aperture for the target area is generated, local polar coordinates for the inclined plane are calculated, and the local polar coordinates are taken as the axis of the distance direction, flight direction, and altitude direction of the aircraft that transmitted the radar signal. After converting the total orthogonal coordinates on the orthogonal coordinate system, the entire orthogonal coordinates are converted to the local orthogonal coordinate system on the local orthogonal coordinate system with axes inclined distance directions on the inclined plane, the flight direction of the aircraft and the normal direction of the inclined plane as axes And an SAR signal processor that generates an SAR image for the target area based on the regional orthogonal coordinates for each partial aperture.

Further, the SAR signal processor converts the transmission/reception position of the radar signal into the local orthogonal coordinates within each partial aperture, and the distance between the local orthogonal coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture. It is characterized by forming SAR images corresponding to local polar coordinates of the inclined plane of each partial aperture using.

In addition, the SAR signal processor is characterized by forming the SAR image by applying a BPA method to a local orthogonal coordinate with a point indicating the actual ground plane position of the inclined plane of each partial aperture based on the distance. .

In addition, the SAR signal processor defines a reference position for forming a ground image for the target area on the entire Cartesian coordinate system, and the defined position is a local polar coordinate on an inclined plane based on the center position of each partial aperture. It is characterized in that it is converted to a system position, and all SAR images corresponding to the respective partial apertures are synthesized at a position in the local polar coordinate system to form a SAR image for the target area projected on the ground plane.

In addition, as a method of processing an SAR signal according to an embodiment of the present invention, using the radar signal received reflected from each partial aperture with respect to a target region, calculating local polar coordinates for an inclined plane of each partial aperture, Converting the local polar coordinates into full Cartesian coordinates that take the radar signal as the axis of the distance direction, flight direction and altitude direction of the aircraft, and convert the entire Cartesian coordinates to the inclined distance direction on the inclined plane, the flight of the aircraft Converting to local Cartesian coordinates on a local Cartesian coordinate system with a direction and a normal direction of the inclined plane as an axis, and the target based on local Cartesian coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture. And generating an SAR image for the region.

In addition, the step of generating the SAR image may include converting a transmission/reception position of the radar signal into the local orthogonal coordinates within each partial aperture, and a point indicating an actual ground plane location of an inclined plane of each partial aperture. And forming a SAR image corresponding to the local polar coordinates of the inclined plane of each partial aperture using a distance between local Cartesian coordinates.

In addition, after the step of forming the SAR image corresponding to the local polar coordinates, defining a reference position for forming the ground image for the target region on the entire Cartesian coordinate system, and the defined position is the center of each partial aperture Converting to a position on a local polar coordinate system on an inclined plane based on a position, and synthesizing all SAR images corresponding to the respective partial apertures at a position on the local polar coordinate system to form a SAR image for the target area projected on the ground plane It characterized in that it further comprises the step of forming.

In addition, the SAR image is characterized by being formed by applying a BPA method to local orthogonal coordinates with a point indicating an actual ground plane position of an inclined plane of each partial aperture based on the distance.

According to an embodiment of the present invention, when generating a SAR image to which FBPA is applied in an environment in which a distance due to a non-linear flight trajectory and an altitude direction deviation exist, the local polar coordinates on the inclined plane for each partial aperture, the inclined distance direction of each inclined plane, the aircraft By converting the flight direction and the normal direction of the inclined plane to the local Cartesian coordinate system, the BPA is applied to enable accurate SAR image generation for the target.

1 is a functional block configuration diagram of an aircraft-mounted synthetic caliber radar for a squint spotlight mode in a nonlinear flight trajectory according to an embodiment of the present invention.
2 is a detailed block diagram of a SAR signal processor according to an embodiment of the present invention.
FIG. 3 is a schematic illustration of a local coordinate system at full aperture in an SAR signal processor to which FBPA is applied according to an embodiment of the present invention.
Figure 4 is an exemplary illustration of the local coordinate system at the l-th partial aperture in the SAR signal processor to which FBPA is applied according to an embodiment of the present invention.
5 is an operation control flow diagram of an SAR signal processor according to an embodiment of the present invention.
6 is an exemplary SAR image according to an embodiment of the present invention.

Hereinafter, the operating principle of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, when it is determined that a detailed description of known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted. In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification.

1 illustrates a functional block configuration of an aircraft-mounted synthetic caliber radar for a squint spotlight mode in a nonlinear flight trajectory according to an embodiment of the present invention.

Hereinafter, the operation of each component of the Synthetic Aperture Radar (SAR) 100 according to an embodiment of the present invention will be described in detail with reference to FIG. 1.

The chirp signal generator 110 generates a wideband baseband chirp signal necessary for the operation of the aircraft-mounted synthetic caliber radar 100.

The transmitter 130 converts the baseband chirp signal generated from the chirp signal generator 110 into a radar signal and transmits it to the surface of the ground or the ocean through the antenna 120.

When the radar signal reflected from the ground or the surface of the ocean is received through the antenna 120, the receiver 140 synthesizes the received signal and the chirp signal and converts the received signal into a baseband received signal.

The SAR signal processor 150 generates an SAR image signal by generating an SAR image signal by image processing a baseband received signal applied from the receiver 140 to generate an SAR image for a target region to be detected.

In this case, when the SAR image generation operation in the SAR signal processor 150 is described in more detail, first, the SAR signal processor 150 uses a baseband received signal to incline each sub aperture (SA) of the target area. Create a plane and calculate the local polar coordinates for the SAR slope plane.

Subsequently, the SAR signal processor 150 converts the local polar coordinates into full orthogonal coordinates using the flight direction, altitude direction, and distance direction of the aircraft to the target area as axes. In addition, the SAR signal processor 150 converts the entire orthogonal coordinates into local orthogonal coordinates using the distance direction vector of the inclined plane, the flight direction vector of the aircraft, and the normal direction vector of the inclined plane as an axis to convert the local orthogonal coordinates for each partial aperture. Based on the SAR image for the target area is generated.

Figure 2 shows a detailed block configuration of the SAR signal processor according to an embodiment of the present invention.

Figure 3 shows the geometry of the local coordinate system in the overall aperture of the SAR image formation process for the target region in the SAR signal processor FBPA is applied according to an embodiment of the present invention.

FIG. 4 is a diagram showing the geometry of a local coordinate system at an l-th partial aperture among all apertures according to an embodiment of the present invention.

Hereinafter, the operation of each component of the SAR signal processor 150 according to an embodiment of the present invention will be described in more detail with reference to FIGS. 2 to 4.

The first coordinate calculator 200 calculates local polar coordinates for the inclined plane 400 of each partial aperture by using a radar signal reflected and received at each partial aperture with respect to the target region 206. As shown in FIG. 4, the inclined plane 400 may mean a plane formed at a certain angle from the ground plane 404 where the target is actually located, and the ground plane 404 and the inclined plane 400 form The angle may be an angle formed by a straight line 402 connecting the center point of each partial aperture and the center point of the target area 406 and the altitude direction Z of the aircraft.

)의 중심점(408)을 기준으로 경사 평면(400)상에 형성되는 표적 영역(406)의 각 위치에 대한 거리(R)와 각도(θ)로 정의되는 좌표를 말할 수 있다.At this time, the local polar coordinates, as shown in Figure 4, for example, the l-th partial aperture (

) May refer to coordinates defined by a distance R and an angle θ for each position of the target area 406 formed on the inclined plane 400 based on the center point 408 of.

The second coordinate calculating unit 202 is the total orthogonal coordinates on the entire orthogonal coordinate system based on the distance direction (X), the flight direction (Y), and the altitude direction (Z) of the aircraft that transmitted the radar signal to the local polar coordinates ( Global Cartesian Coordinate).

That is, as illustrated in FIG. 4, the second coordinate calculator 202 determines the center of the l-th partial aperture among all partial apertures, and displays the local polar coordinates on the inclined plane 400 including the squint angle. By using Equation 1 below, the aircraft is converted into the entire orthogonal coordinate system on the entire orthogonal coordinate system using the distance direction (X), the flight direction (Y), and the altitude direction (Z) of the aircraft as axes. This is to indicate which position of the local polar coordinate on the inclined plane 406 corresponds to the actual ground plane 404.

는 극좌표 상의 거리,

는 극좌표 상의 경사 평면(400)의 스퀸트 각도,

는 지상 평면(404)의 스퀸트 각도,

는

번째 부분 구경의 기준 높이,

,

는 지역 극좌표의 인덱스(index)이다. In [Equation 1] above

Is the distance in polar coordinates,

Is the squint angle of the inclined plane 400 on the polar coordinates,

Is the squint angle of the ground plane 404,

The

Reference height of the second part aperture,

,

Is the index of local polar coordinates.

), 항공기의 비행 방향(Y') 벡터(

)및 경사 평면(200)의 법선 방향(Z') 벡터(

)를 축으로 하는 지역 직교 좌표계상의 지역 직교 좌표계(

)로 변환한다. The third coordinate calculating unit 204 uses the total orthogonal coordinates calculated by the second coordinate calculating unit 202 using the following [Equation 2], the inclined distance direction (X') vector on the inclined plane 400 (

), the flight direction (Y') vector of the aircraft (

) And the normal direction (Z') vector of the inclined plane 200 (

Local Cartesian Coordinate System on the Local Cartesian Coordinate System ()

).

At this time, when the entire Cartesian coordinates are transformed to the local Cartesian coordinates of the inclined plane 400 by axis conversion using [Equation 2] as described above, the position of the inclined plane 400 expressed in polar coordinates in the l-th partial aperture is local. It can be expressed as a reference position on a Cartesian coordinate system. In addition, here, the distance direction X'on the inclined plane may mean the direction of the vector in which the vector of the distance direction X is projected onto the inclined plane.

The SAR image generation unit 206 generates an SAR image for the target area 406 based on local orthogonal coordinates of the inclined plane 400 of each partial aperture.

In the generation of the SAR image as described above, the SAR image generation unit 206 converts the transmission/reception position of the radar signal within each partial aperture to local orthogonal coordinates, and determines the actual ground plane position of the inclined plane 400 of each partial aperture. SAR images corresponding to local polar coordinates of the inclined plane 400 of each partial aperture may be generated by using a distance between local orthogonal coordinates with a point indicated.

Hereinafter, the operation of the SAR image generation unit 206 will be described in more detail.

First, the SAR image generating unit 206 converts all radar signal transmission/reception positions within each partial aperture into a local orthogonal coordinate system in the same way as the coordinate conversion process for the inclined plane 400, and the actual ground of the inclined plane 400 obtained above. The partial aperture BPA is performed in consideration of the distance between the reference positions representing the planar positions. In this case, since it is possible to form an image based on the exact distance between the position of the aircraft having the nonlinear trajectory due to the fluctuation and the target existing on the ground, the SAR image generation unit 206 is capable of forming all ground within the data acquired during partial aperture. It is possible to generate an SAR image on the local polar coordinate system of the inclined plane 400 where the shaking motion compensation reflecting the target position is made.

Subsequently, the SAR image generating unit 206 defines a reference position for forming the final high-resolution terrestrial image on the entire orthogonal coordinate system, and converts the defined position to a local polar coordinate position on an inclined plane based on the center position of each partial aperture. . Then, in order to project SAR images of each partial aperture, SAR images are formed by applying a two-dimensional interpolation method on the polar coordinates of the inclined plane area. Subsequently, if SAR images are sequentially synthesized for all sub-diameters, finally, high-resolution SAR images projected directly on the ground plane are generated.

FIG. 5 is a flowchart illustrating an operation control flow of an SAR signal processor for forming a ground plane SAR image of a reliable high-speed backprojection algorithm in a nonlinear flight trajectory according to an embodiment of the present invention. Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 5.

First, the SAR signal processor 150 receives a radar signal that is received by being reflected at each partial aperture with respect to the target area 400.

At this time, such a radar signal means a radio frequency (RF) signal transmitted to the surface of the ground or the ocean to detect the target from the synthetic caliber radar 100 mounted on the aircraft, and this radar signal is a spotlight mode (spotlight mode) In can be transmitted to a target area of a predetermined area, it is reflected by the target located in the target area 406 can be received by the SAR signal processor 150 in the synthetic caliber radar 100. In addition, the radar signal reflected and received at each of the partial apertures may mean distance-compressed SAR data including distance information between an aircraft and a target, but is not limited thereto.

Subsequently, the SAR signal processor 150 calculates local polar coordinates for the inclined plane 400 of each partial aperture using a radar signal reflected and received at each partial aperture with respect to the target region 406.

)의 중심점(408)을 기준으로 경사 평면(400)상에 형성되는 표적 영역(406)의 각 위치에 대한 거리(R)와 각도(θ)로 정의되는 좌표를 말할 수 있다.At this time, the local polar coordinates, as shown in Figure 4, the l-th partial aperture (

) May refer to coordinates defined by a distance R and an angle θ for each position of the target area 406 formed on the inclined plane 400 based on the center point 408 of.

Subsequently, the SAR signal processor 150 converts the local polar coordinates into full orthogonal coordinates on the entire orthogonal coordinate system based on the distance direction (X), the flight direction (Y), and the altitude direction (Z) of the aircraft that transmitted the radar signal. To convert. This is to indicate which position of the local polar coordinate on the inclined plane 406 corresponds to the actual ground plane 404.

Subsequently, the SAR signal processor 150 displays the entire Cartesian coordinates in the distance direction (X') vector on the inclined plane 400, the flight direction (Y') vector of the aircraft, and the normal direction (Z') vector of the inclined plane 400. Converts to local rectangular coordinates on the local rectangular coordinate system with an axis of. At this time, when the axis is transformed using the entire Cartesian coordinates as described above to convert to the local Cartesian coordinates of the inclined plane 400, the position of the inclined plane 400 expressed in polar coordinates in the l-th partial aperture is the actual ground on the local Cartesian coordinate system. It may be expressed as a reference position of a point indicating a flat position.

Then, the SAR signal processor 150 generates an SAR image for the target region 406 based on the local orthogonal coordinates of the SAR inclined plane of each partial aperture.

In the generation of the SAR image as above, the SAR signal processor 150 converts the transmission/reception position of the radar signal within each partial aperture into Cartesian coordinates, and indicates the actual ground plane position of the inclined plane 400 of each partial aperture. SAR images corresponding to local polar coordinates of the inclined plane 400 of each partial aperture may be generated using a distance between local orthogonal coordinates with a point.

In addition, the SAR signal processor 150 converts all radar signal transmission/reception positions within the partial aperture into a local orthogonal coordinate system, similar to the coordinate conversion process for the inclined plane 400, and the actual ground plane position of the inclined plane 400 obtained above. The partial aperture BPA is performed in consideration of the distance between the reference positions of the points representing. In this case, since it is possible to generate an image based on an accurate distance between an aircraft position having a nonlinear trajectory due to fluctuations and a target existing on the ground, the SAR signal processor 150 positions all ground targets in the data acquired during partial aperture. It is possible to generate an SAR image on the local polar coordinate system of the inclined plane 400 where the shaking motion compensation is reflected.

Subsequently, the SAR signal processor 150 defines a reference position for forming the final high-resolution terrestrial image on the entire orthogonal coordinate system, and defines the defined position as a local polar coordinate position on the inclined plane 400 based on the center position of each partial aperture. To convert. Then, in order to project SAR images of each partial aperture, SAR images are generated by applying a two-dimensional interpolation method on the polar coordinates of the inclined plane 400, and SAR images are sequentially synthesized for all partial apertures to generate a ground plane 404. ) Generates a high-resolution SAR image projected directly on top.

6 illustrates an SAR image according to an embodiment of the present invention.

Figure 6 (a) is a conventional nonlinear flight distance, altitude direction deviation (oscillation) shows the existing SB image by the existing FBPA in an environment, Figure 6 (b) is an embodiment of the present invention The SAR image is shown.

Referring to FIG. 6 as described above, in the SAR image according to the related art, the performance of the four point targets excluding the center point of the image is significantly deteriorated in the direction of the cross range, so that the cross shape is not visible at all. On the other hand, in the SAR image to which the technology according to an embodiment of the present invention is applied, it can be seen that all five dot targets are accurately formed as cross-shaped dot targets.

As described above, according to an embodiment of the present invention, when generating a SAR image to which FBPA is applied in an environment in which a distance and an altitude direction deviation due to a nonlinear flight trajectory exist, the local polar coordinates on the inclined plane for each partial aperture are inclined in each inclined plane. By converting the distance direction, the flight direction of the aircraft, and the normal direction of the inclined plane to the local Cartesian coordinate system, the BPA is applied to enable accurate SAR image generation for the target.

Combinations of each step of each flowchart attached to the present invention may be performed by computer program instructions. Since these computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, those instructions performed through a processor of a computer or other programmable data processing equipment are described in each step of the flowchart. It creates a means to do them. These computer program instructions can also be stored in computer readable or computer readable memory that can be oriented to a computer or other programmable data processing equipment to implement a function in a particular way, so that computer readable or computer readable memory It is also possible for the instructions stored in to produce an article of manufacture containing instructions means for performing the functions described in each step of the flowchart. Computer program instructions can also be mounted on a computer or other programmable data processing equipment, so a series of operational steps are performed on a computer or other programmable data processing equipment to create a process that is executed by the computer to generate a computer or other programmable data. It is also possible for instructions to perform processing equipment to provide steps for performing the functions described in each step of the flowchart.

Further, each step may represent a module, segment, or portion of code that includes one or more executable instructions for executing the specified logical function(s). It should also be noted that in some alternative embodiments it is also possible that the functions mentioned in the steps occur out of order. For example, the two steps shown in succession may in fact be performed substantially simultaneously, or it is also possible that the steps are sometimes performed in reverse order depending on the corresponding function.

Meanwhile, in the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the invention should not be determined by the described embodiments, but should be determined by the claims.

150: SAR signal processor 200: first coordinate calculation unit
202: second coordinate calculator 204: third coordinate calculator
206: SAR image generating unit

Claims (14)

A first coordinate calculator configured to calculate local polar coordinates for an inclined plane of each partial aperture using a radar signal reflected and received with respect to a target area;
A second coordinate calculator for converting the local polar coordinates into all Cartesian coordinates on the entire Cartesian coordinate system with axes of the distance direction, flight direction and altitude of the aircraft transmitting the radar signal;
A third coordinate calculator for converting the entire Cartesian coordinates into local Cartesian coordinates on a local Cartesian coordinate system with axes inclined distance directions on the inclined plane, flight directions of the aircraft and normal directions of the inclined planes;
And an SAR image generator for generating a Synthetic Aperture Radar (SAR) image for the target region based on the regional orthogonal coordinates of the inclined plane of each partial aperture.
The SAR image generating unit,
The transmission/reception position of the radar signal in each partial aperture is converted to the local Cartesian coordinates, and the distance between the local orthogonal coordinates is used by using the distance between the local orthogonal coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture. SAR image corresponding to the local polar coordinate of the inclined plane is formed,
The SAR image is formed by applying a BPA (Back-Projection Algorithm) method to a local orthogonal coordinate with a point indicating an actual ground plane position of the inclined plane of each partial aperture based on the distance.
SAR signal processor. delete delete A first coordinate calculator configured to calculate local polar coordinates for an inclined plane of each partial aperture using a radar signal reflected and received with respect to a target area;
A second coordinate calculator for converting the local polar coordinates into all Cartesian coordinates on the entire Cartesian coordinate system with axes of the distance direction, flight direction and altitude of the aircraft transmitting the radar signal;
A third coordinate calculator for converting the entire Cartesian coordinates into local Cartesian coordinates on a local Cartesian coordinate system with axes inclined distance directions on the inclined plane, flight directions of the aircraft and normal directions of the inclined planes;
And an SAR image generator for generating a Synthetic Aperture Radar (SAR) image for the target region based on the regional orthogonal coordinates of the inclined plane of each partial aperture.
The SAR image generating unit,
The transmission/reception position of the radar signal in each partial aperture is converted to the local Cartesian coordinates, and the distance between the local orthogonal coordinates is used by using the distance between the local orthogonal coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture. SAR image corresponding to the local polar coordinate of the inclined plane is formed,
The SAR image generating unit,
A reference position for forming a ground image for the target area is defined on the entire Cartesian coordinate system, and the defined position is converted into a local polar coordinate position on an inclined plane based on the central position of each partial aperture, and the area All SAR images corresponding to the respective partial apertures are synthesized at positions on the polar coordinate system to form SAR images for the target area projected on the ground plane.
SAR signal processor. The method of claim 4,
The SAR image generating unit,
Synthesizing all the SAR images by applying a 2D interpolation method
SAR signal processor. According to claim 1,
The location of transmission and reception of the radar signal,
Distributed within each of the partial apertures as a nonlinear trajectory
SAR signal processor. With an antenna,
A chirp signal generator that generates a wideband baseband chirp signal,
A transmitter that converts the baseband chirp signal to a radar signal and transmits it to a target area to be detected through the antenna;
A receiver which receives the received signal reflected by the radar signal through the antenna, synthesizes the chirp signal and converts it into a baseband received signal;
Using the received signal of the baseband, an inclined plane for each partial aperture is generated for the target area, local polar coordinates are calculated for the inclined plane, and the local polar coordinates are in a distance direction and flight of the aircraft that has transmitted the radar signal. After converting the total Cartesian coordinates on the entire Cartesian coordinate system using the direction and altitude directions as axes, the entire Cartesian coordinates are inclined distance directions on the inclined plane, the flight direction of the aircraft, and the normal direction of the inclined plane as an axis. And an SAR signal processor that converts to a local rectangular coordinate system on a rectangular coordinate system and generates an SAR image for the target region based on the local rectangular coordinates for each partial aperture.
The SAR signal processor,
The transmission/reception position of the radar signal in each partial aperture is converted to the local Cartesian coordinates, and the distance between the local orthogonal coordinates and the point representing the actual ground plane position of the inclined plane of each partial aperture is used. SAR image corresponding to the local polar coordinate of the inclined plane is formed,
Based on the distance, the SAR image is formed by applying a BPA method to a local orthogonal coordinate with a point indicating the actual ground plane position of the inclined plane of each partial aperture.
Synthetic caliber radar mounted on aircraft. delete delete With an antenna,
A chirp signal generator that generates a wideband baseband chirp signal,
A transmitter that converts the baseband chirp signal to a radar signal and transmits it to a target area to be detected through the antenna;
A receiver which receives the received signal reflected by the radar signal through the antenna, synthesizes the chirp signal and converts it into a baseband received signal;
Using the received signal of the baseband, an inclined plane for each partial aperture is generated for the target area, local polar coordinates are calculated for the inclined plane, and the local polar coordinates are in a distance direction and flight of the aircraft that has transmitted the radar signal. After converting the total Cartesian coordinates on the entire Cartesian coordinate system using the direction and altitude directions as axes, the entire Cartesian coordinates are inclined distance directions on the inclined plane, the flight direction of the aircraft, and the normal direction of the inclined plane as an axis. And an SAR signal processor that converts to a local rectangular coordinate system on a rectangular coordinate system and generates an SAR image for the target region based on the local rectangular coordinates for each partial aperture.
The SAR signal processor,
The transmission/reception position of the radar signal in each partial aperture is converted to the local Cartesian coordinates, and the distance between the local orthogonal coordinates and the point representing the actual ground plane position of the inclined plane of each partial aperture is used. SAR image corresponding to the local polar coordinate of the inclined plane is formed,
The SAR signal processor,
A reference position for forming a ground image for the target area is defined on the entire Cartesian coordinate system, and the defined position is converted into a local polar coordinate position on an inclined plane based on the central position of each partial aperture, and the area All SAR images corresponding to the partial apertures are synthesized at positions on the polar coordinate system to form SAR images for the target area projected on the ground plane.
Synthetic caliber radar mounted on aircraft. Calculating local polar coordinates for an inclined plane of each partial aperture using a radar signal reflected and received at each partial aperture with respect to a target area;
Converting the local polar coordinates into full Cartesian coordinates with an axis as a distance direction, a flight direction, and an altitude direction of the aircraft transmitting the radar signal;
Converting the entire Cartesian coordinates into local Cartesian coordinates on a local Cartesian coordinate system with axes inclined distance direction on the inclined plane, flight direction of the aircraft and normal direction of the inclined plane;
And generating an SAR image for the target area based on regional orthogonal coordinates of the inclined plane of each partial aperture.
The step of generating the SAR image,
Converting the transmission/reception position of the radar signal within each partial aperture into the local Cartesian coordinates;
And forming a SAR image corresponding to local polar coordinates of the inclined plane of each partial aperture by using a distance between local orthogonal coordinates with a point representing an actual ground plane position of the inclined plane of each partial aperture,
The SAR image,
Based on the distance is formed by applying the BPA method to the local orthogonal coordinates with a point indicating the actual ground plane position of the inclined plane of each partial aperture
SAR signal processing method. delete Calculating local polar coordinates for an inclined plane of each partial aperture using a radar signal reflected and received at each partial aperture with respect to a target area;
Converting the local polar coordinates into full Cartesian coordinates with an axis as a distance direction, a flight direction, and an altitude direction of the aircraft transmitting the radar signal;
Converting the entire Cartesian coordinates into local Cartesian coordinates on a local Cartesian coordinate system with axes oriented in the oblique distance direction on the inclined plane, the flight direction of the aircraft and the normal direction of the inclined plane;
And generating an SAR image for the target area based on regional orthogonal coordinates of the inclined plane of each partial aperture.
The step of generating the SAR image,
Converting the transmission/reception position of the radar signal within each partial aperture into the local Cartesian coordinates;
And forming a SAR image corresponding to local polar coordinates of the inclined plane of each partial aperture by using a distance between local orthogonal coordinates with a point representing an actual ground plane position of the inclined plane of each partial aperture,
After the step of forming the SAR image corresponding to the local polar coordinates,
Defining a reference position for forming a ground image for the target area on the entire Cartesian coordinate system;
Converting the defined position to a position on a local polar coordinate system on an inclined plane based on the central position of each partial aperture;
The method further includes synthesizing all SAR images corresponding to the respective partial apertures at locations on the local polar coordinate system to form SAR images for the target area projected on the ground plane.
SAR signal processing method. delete

Images