KR101920379B1 - Bistatic synthetic aperture radar system based on global navigation satellite system - Google Patents

Abstract

The present invention relates to a bistatic SAR system using a GNSS which can precisely track a target. The bistatic SAR system using a GNSS comprises: a GNSS satellite transmitting a first signal for tracking a target; and a receiver receiving a first signal directly transmitted from a GNSS satellite and a second signal generated when the first signal is a reflected signal reflected by the target.

Description

TECHNICAL FIELD [0001] The present invention relates to a bi-static synthetic aperture radar system based on a satellite navigation system,

The present invention relates to a bistatic synthetic aperture radar system, and more particularly, to a bistatic synthetic aperture radar system capable of receiving a transmitted signal of a global satellite navigation system satellite and a reflected signal reflected by a target, To a bistatic synthetic aperture radar system.

Generally, the navigator for guidance vehicle can be configured to track the target on the ground according to the purpose of the guidance vehicle. Currently, most navigation systems for guided vehicles are designed to detect a target by emitting and receiving a very high frequency signal within a predetermined angle range in the direction of guided flight movement, but the angle resolution is not good because of wide beam width.

Especially, the navigator of the guided vehicle to intercept the target such as the ship in the sea near the coast can not accurately detect the target due to the influence of the ground clutter reflected on the land when the land exists at the same distance within the beam width And the like. On the other hand, the image searcher that acquires and analyzes the infrared or visible light image frequently receives the influence of the atmosphere such as rain, snow, clouds, and mist, and often fails to detect the target.

In addition, an electromagnetic wave searcher that radiates a high frequency signal and analyzes the signal reflected from the target to detect the target can determine the position of the target without being influenced by the atmosphere. However, Speed, and so on, but can not acquire the accurate shape of the target.

To overcome this limitation, Synthetic Aperture Radar (SAR) has been developed. SAR is typically loaded on airplanes or satellites and can be used to acquire a high-resolution, high-resolution image of the surface of the Earth's surface by radiating beams to the surface several times and using the relative changes in the Doppler frequency Means a radar. Since SAR utilizes microwave frequencies in the microwave range, it is able to observe land terrain and sea without being affected by the climatic conditions such as haze, snow, rain, snow, clouds and smoke, Because it is a system, images can be obtained regardless of night or day.

SAR is a technique for obtaining an image of a non-moving indicator. The SAR is used to steer the beam in the vertical direction in the traveling direction of the flying object, which is the direction in which the change of the indicator is detected the greatest so that the relative change characteristic of the Doppler frequency is well- . However, if the image is obtained by steer- ing the beam in the vertical direction from the traveling direction of the flying object, since the position of the flying object has already passed the target at the time of detecting the target, it is difficult to apply it to the guided vehicle in which the target must be traced. If the beam is steered toward the traveling direction of the flying object, there is a problem that the angle resolution decreases as the traveling direction of the flying object and the angle between the beam are reduced.

Thus, conventional radar and SAR systems have located targets by the way the transmitter transmits high-power signals and the receiver receives signals reflected by the target. However, since the radar signal is easily exposed to the other party, a jamming device has been introduced in which a wrong reflection signal is transmitted by using it to cause an error. Also, there is a problem that the system is large and the cost is very high for transmitting a high output signal.

Therefore, there is a need to develop a SAR system that can be mounted on a small drones compared to existing SAR systems, and can image the target or surrounding terrain in a covert manner without exposing its own position.

1 is a diagram for explaining a general SAR system.

1, the SAR system mounted on the air vehicle 100 is configured such that the air vehicle 100 travels in the traveling direction 120 while a predetermined distance is maintained between the ground surface and the target 150 using a short moving antenna It can radiate a radar signal and receive the reflected signals reflected on the target 150 to obtain a higher azimuthal resolution than the beam width of the actual antenna provides by using Doppler transitions between the received signals. A radar system including such a SAR system may be implemented as a monostatic SAR radar system or a Bistatic SAR radar system. A monostatic SAR radar system is a system in which a transmitter and a receiver are in the same position, and a bistatic SAR radar system is a system in which a transmitter and a receiver are located at different distances from each other by a great distance. A bistatic SAR radar system can provide more information than a mono static SAR system, but it is very difficult to synchronize the transmitter and receiver because of their very physical separation.

As described above, a bistatic SAR system that transmits a high-power signal and receives a reflected signal at present is the most commonly used although the time synchronization is difficult due to the physical distance between the transmitter and the reception period. Passive Coherent Location (PCL) technology using FM base station signals such as commercial radio and DMB as reference signals and using reflected waves is being studied. This PCL technique can image or redirect target targets without exposure of the location.

Korean Patent No. 10-1733035 discloses a prior art patent related to this conventional bistatic SAR system, but the signal source used for tracking the target differs from the present invention.

However, in this target extraction method, the part that has the greatest effect on the performance is the high resolution of the pixel to image the object and the ability to accurately distinguish the peripheral object from the specific object.

Conventionally, since a reference signal is transmitted on the ground and a signal reflected from a receiver on the ground is received, the function of distinguishing a specific object from the surrounding environment has been very difficult. Therefore, it is not possible to obtain reliable statistical information when realistic bistatic SAR system is implemented, and the reliability of the tracking of the target in the imaged image is degraded.

In addition, in order to increase the resolution of the pixels, the bandwidth of the reference signal should be very wide, but the FM / DMB signals on the ground are only a few hundred kHz, so that only objects measuring tens of meters can be recognized. Due to such a problem, it is a reality that a bistatic radar which uses a high output rather than a PCL has been used up to now.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned needs, and it is an object of the present invention to provide an apparatus and method for acquiring an SAR image using a reference signal transmitted directly from a GNSS satellite and a reflected signal, And to provide a system that can do this.

According to an aspect of the present invention, there is provided a Bistatic Synthetic Aperture Radar (SAR) system using a Global Navigation Satellite System (GNSS) according to an embodiment of the present invention, A GNSS satellite for transmitting a first signal in an extraterrestrial orbit; And a receiver for receiving a first signal directly transmitted from the GNSS satellite and a second signal mounted on a ground, a vehicle or a ship, the second signal being a reflection signal that is reflected by the target, A window processing unit for performing window processing on the frequency-converted signal of the auto-correlated signal; a frequency-transformed signal of the second signal and a frequency- A second multiplier for multiplying the masked masking signal by the window-processed autocorrelation signal to synchronize the masked signal with the windowed autocorrelation signal, and a second multiplier for converting the synchronized frequency domain signal into a time domain An inverse fast Fourier transform unit and an SAR image generating unit for generating an SAR image from the signal converted into the time domain All.

According to the embodiment of the present invention described above, it is possible to provide an electronic support function without existing electronic support equipment, monitor movement of surrounding targets, and detect directions according to movement of a target.

Also, according to the embodiment of the present invention, it is possible to replace the existing SAR and passive coherent location (PCL) radar.

In addition, according to the embodiment of the present invention, since a GNSS-based navigation signal is used, a separate reference signal is not needed, and the location of the receiver is not exposed, so that target monitoring can be performed secretly.

In addition, satellite signals of 50MHz or more, which are broadband in the GNSS signal, can be used to identify SAR image pixels with a maximum resolution of 3x3m.

Also, since the signal received from the earth's orbit is used, it is possible to image all the terrain and the target object on the ground, and it is very easy to synchronize the different types of vision.

1 is a diagram for explaining a general SAR system.
FIG. 2 is a view for explaining a difference in operation principle between a bistatic SAR system according to an embodiment of the present invention and an existing bistatic SAR system.
3 is a block diagram of a receiver of a GNSS-based bistatic SAR system according to an embodiment of the present invention.
4 is a flowchart of a receiver operation of a bistatic SAR system using a GNSS according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating extraction of a target from a SAR image according to an embodiment of the present invention.
6 is a diagram for comparing SAR resolutions of a bistatic SAR system using a GNSS and a bistatic SAR system using a DMB signal according to an embodiment of the present invention.
FIG. 7 is a view showing an example of forming an SAR image for a surrounding terrain according to an embodiment of the present invention.
FIG. 8 is a conceptual diagram for explaining an operation example of a GNSS-based bistatic SAR system according to an embodiment of the present invention.
9 is a diagram for explaining a process of acquiring Doppler shift information generated according to movement of a target in an FFT according to an embodiment of the present invention.
FIG. 10 is a diagram for explaining applicable examples of a GNSS-based bistatic SAR system according to an embodiment of the present invention.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. However, the present invention can be implemented in various different forms, and is not limited to the embodiments described. In order to clearly describe the present invention, parts that are not related to the description are omitted, and the same reference numerals in the drawings denote the same members.

Throughout the specification, when an element is referred to as " including " an element, it does not exclude other elements unless specifically stated to the contrary. The terms "part", "unit", "module", "block", and the like described in the specification mean units for processing at least one function or operation, And a combination of software.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Should be understood. Various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a view for explaining a difference in operation principle between a bistatic SAR system according to an embodiment of the present invention and an existing bistatic SAR system.

Reference numeral 200 denotes an operation method of a conventional bistatic SAR system, reference numeral 210 denotes an operation method of a conventional PCL bistatic SAR system, reference numeral 220 denotes a GNSS-based It shows how the bistatic SAR system works.

First, in a conventional bistatic SAR system, when a transmitter physically separated from a receiver in step 200a transmits a high-output direct signal (reference signal), in step 200b, the receiver detects that the reference signal is reflected Signal. In step 200c, the receiver extracts an image of a region scanned from the reference signal and the reflected signal, and extracts a target from the image in step 200d.

In operation 210a, the receiver receives a signal (reference signal) directly transmitted from a ground station such as FM (Frequency Modulation) or DMB (Digital Mobile Broadcasting) In step 210b, the reference signal receives the reflected signal reflected from the target. In step 210c, the receiver extracts an image of the scanned area using the reference signal and the reflection signal, and extracts a target from the image in step 210d.

In operation 220a of the GNSS-based bistatic SAR system according to the embodiment of the present invention, the receiver receives a signal (reference signal) directly transmitted from the GNSS satellite outside the earth, and in step 220b, Receives a reflected signal reflected from the target. In step 220c, the receiver extracts an image of the scanned area using the reference signal and the reflection signal, and extracts the target from the image in step 220d.

Reference numeral 220 denotes a GNSS satellite signal having a unique code (PRN code) characteristic of the GNSS satellite, as a reference signal of the bistatic SAR system, unlike the system described in reference numerals 200 and 210, Can be used.

In addition, reference numeral 200a in FIG. 2 is a method used in a conventional radar system. After transmitting a high-power signal to a specific target, a target is tracked using a Doppler difference and a signal intensity of a signal reflected from the specific target. And forms an image. However, the embodiment of the present invention does not require the process of the reference numeral 200a. This is because, in the embodiment of the present invention, the transmitter in the bistatic SAR system uses the signal transmitted by the GNSS satellite located outside the earth as a reference signal transmitted to the receiver.

Such a scheme may be viewed as a concept similar to the bistatic SAR radar system receiving a signal of an FM or DMB local station as a reference signal at 210, but the signal transmitted by an FM or DMB station may be up to tens The image resolution of tens of meters (m) can not be obtained due to the bandwidth of the narrow band as compared with the signal of the GNSS satellite having the bandwidth of MHz. However, according to the embodiment of the present invention, since a GNSS signal having a broader band than the FM / DMB signal is used, an image resolution of several meters (m) can be obtained, and the image resolution can be processed several tens of times or more.

In addition, although the conventional bi-static SAR system requires a separate device for time synchronization of the reference signal, in the embodiment of the present invention, since time synchronization is performed using UTC (Coordinated Universal Time) information transmitted from the GNSS, There is no need for a device for time synchronization. Thus, using the GNSS-based bistatic SAR system according to the embodiment of the present invention, such as reference numeral 220, it is possible to easily perform time synchronization with any receiver mounted on the platform of the bistatic SAR system located on the ground, And the same reference signal is used for image processing.

Table 1 below is a comparison table for each SAR system described in reference numerals 210, 220, and 230 in FIG.

division Original Bistatic SAR PCL system GNSS-based Bistatic SAR Maintenance cost Very high at least at least System Size Giant littleness littleness Operational performance High resolution Low resolution Medium resolution Operational radius System installation area Reference signal nearby
(FM broadcast base station) No limit / sensitivity range
(Navigation signal receiving area) Whether it is concealed Impossible possible possible Synchronization system Time Synchronization System Required Time Synchronization System Required Using navigation signals

3 is a block diagram of a receiver 300 of a GNSS-based bistatic SAR system according to an embodiment of the present invention. The receiver 300 according to the present invention may be mounted on a platform of a bistatic SAR system such as a flight vehicle or a ship to receive a second signal, which is a reflection signal in which the first signal is reflected by the target.

3, a receiver 300 according to an embodiment of the present invention receives a first signal 306 and a second signal 301 transmitted from a GNSS satellite, which is a transmitter, Is a direct signal transmitted from a GNSS satellite, which is a transmitter located on an outer orbit, and the second signal 301 means a reflection signal in which the first signal 306 is reflected by the target.

In this specification, a direct signal transmitted from a GNSS satellite, which is a transmitter, to a receiver will be used in the same sense as a reference signal used in a bistatic SAR system.

The RF receiver 307 of the receiver 300 receives the first signal 306 from the GNSS satellite on the extrasolar extras via the antenna ANT and the demodulator 308 demodulates the signal received by the RF receiver 307 Demodulates it into a baseband and outputs it to the autocorrelation unit 310 and the second Fast Fourier Transform (FFT) 309.

The autocorrelation unit 310 performs autocorrelation using the autocorrelation function of the demodulated first signal, and the third fast Fourier transform unit (FFT) 311 performs autocorrelation using the autocorrelation function And the window processing unit 312 processes the frequency-converted signal by the third fast Fourier transform unit 311 and outputs the window processed signal 313) to the second multiplier (315).

Specifically, the autocorrelation unit 310 performs autocorrelation using a PRN (Pseudo Random Noise) code of the received first signal 306 and a PRN code of the GNSS satellite among previously stored PRN codes.

The synchronization detector 330 calculates a power spectral density of the first signal 306 using the autocorrelated signal transformed into the frequency domain and outputs the power spectral density of the first signal 306 to the time synchronization (Time Synchronization).

Meanwhile, the second signal 301 is received by the RF receiver 302, demodulated by the demodulator 303 in a baseband, and output to the first fast Fourier transformer (FFT) 304 And a first fast Fourier transformer (FFT) 304 converts the demodulated signal into a frequency domain and outputs the result to the first multiplier 305.

The first multiplier 305 masks the signal converted into the frequency domain by the first FFT 304 and the first FFT 309 and outputs the masked signal 314 to the second multiplier 315 ).

The second multiplier 315 multiplies the masked signal 314 by the window processed autocorrelation signal 313 and outputs the multiplied signal 316 to an Inverse Fast Fourier Transform (IFFT) 317, as shown in FIG.

The signal converted into the time domain again by the IFFT 317 is input to the SAR image generation unit 318. The SAR image generation unit 318 generates a SAR image using the signal converted into the time domain in the IFFT 317, Image 350 is generated. Generally, the SAR image generating unit 318 generates an image for the target using the Doppler difference and the signal intensity of the signal reflected from the target. Since this uses a general SAR image processing process, It will be omitted.

When the SAR image 350 is generated by the SAR image generation unit 318, the target identification unit 319 generates target identification information that identifies a target area transformed by the image characteristic from the generated SAR image, The distance measuring unit 320 measures the distance of the target using the Doppler shift characteristic of the generated SAR image 350.

Specifically, the target identifying unit 319 performs a function of extracting a region in the direction of the target using the input signal. Here, the extracted region data is a portion including meaningful information. For example, a building, a tree, a target, and so on, all of which are more reflective than the surrounding environment. However, the surrounding environment such as the earth corresponds to an object having a low reflectance because it reflects by scattering or attenuating a radio wave. The target identifying unit 319 also performs a target identifying function. The target identifying unit 319 performs target identification based on an estimated position for an area in which an image characteristic is changed except a fixed or motionless image using a predetermined algorithm.

The communication link unit 320 establishes a communication link with a communication link unit mounted on another ground station, a vehicle, or a ship equipped with the receiver 300 to synchronize the time synchronization (Time Synchronization).

Therefore, the target distance measuring unit 320 according to the embodiment of the present invention may measure the distance between the target 301 and the first signal 306 received by the receiver 300, The location of the target may be calculated using the identification information of the target received through the communication link of the receiver installed in the devices. Other devices can be installed on the ground, air, or sea, and the area identification and the target identification are different depending on the direction of each reflected wave direction.

In case of an object having a fast moving speed, accuracy may be different. However, all devices to which the GNSS-based SAR system platform according to the embodiment of the present invention is applied are not problematic because they perform time synchronization using the same navigation signal.

Also, the receiver 300 according to the embodiment of the present invention may be a broadband SDR (Software Defined Radio) based GNSS receiver having two or more channels.

4 is a flowchart illustrating an operation of a receiver 300 of a bistatic SAR system using a GNSS according to an embodiment of the present invention. In particular, an SDR-based GNSS-based receiver according to an embodiment of the present invention receives satellite signals of various GNSS systems, such as US GPS, GLONASS of Russia, BeiDou of China, Galileo system of Europe, The signal can be processed by bonding the signal.

Table 2 below compares the SAR image resolutions that can be identified by the bandwidth of the current GNSS system and DMB signals.

In the embodiment of the present invention, since a wideband signal of several tens of MHz or more is used, image resolution can be distinguished at high resolution in terms of correlation and frequency distribution. Although it is currently commercialized, the Galileo system, which is a European GNSS system, uses the broadest bandwidth, and satellite tracking is a reality. Being capable of satellite tracking means that it is possible to receive PRN codes and navigation messages.

GNSS band Bandwidth Identification resolution Remarks Terrestrial DMB 6 MHz <27m LOS not available GPS C / A-code 1MHz <150m Not used GLONASS P-Code 5MHz <30m Galileo E5a / E5b 10MHz <15m Galileo full E5 50MHz <3m

As shown in <Table 2>, when the Galileo system of Europe, which is the broadest of the existing GNSS systems, is used, the resolution can be less than 3 m.

In step 401, the receiver 300 determines whether the second signal 301 is received. If received, the receiver 300 demodulates the received signal in step 403. In step 405, the demodulated signal is frequency- Conversion.

The receiver 300 checks whether the first signal 306 is received in step 409. If received, the receiver 300 demodulates the signal received in step 411, and transmits the demodulated signal to the frequency domain through FFT In step 415, auto correlation is performed.

After the autocorrelation processing in step 415, the receiver 300 detects the synchronization of the first signal in step 417, converts the signal to the frequency domain through the FFT in step 419, and then performs window processing in step 421. [

In step 407, the receiver 300 masks the second signal FFTed in step 405 and the first signal FFTed in step 413, and then, in step 423, Time synchronization is performed on the masked signal, and IFFT is performed in step 425 to convert the signal into a time-domain signal, and then an SAR image is generated.

In step 427, the receiver 300 identifies the target from the SAR image generated in step 425, and in step 429, the SAR system using the GNSS according to an embodiment of the present invention installed in another ground station, The time synchronization may be performed by connecting the receiver and the communication link, and in step 431, the target distance measured using the first signal received by each receiver with respect to the target may be obtained and calculated. At this time, the receivers of the SAR system using the GNSS according to the embodiment of the present invention, when communication is established with each other via the communication link unit 321, use the target identification information for the same target and the first signal received from the GNSS The calculated target distance can be measured more precisely. Because the receivers mounted on different carriers are installed on the ground, the air, and the sea, the target identification may be different from that of the scanning target region depending on the direction of the second signal, which is the reflection signal of the first signal reflected by the target Because.

However, the receiver 300 according to the embodiment of the present invention uses only the first signal directly received from the GNSS satellite and the second signal, which is the reflected signal, without the communication link with other receivers through the communication link unit 321 You can identify the target and calculate the distance from the target.

FIG. 5 illustrates extracting a target from an SAR image according to an embodiment of the present invention, and with reference to FIG. 5, there is shown an identified target 510 in an SAR image generated in accordance with an embodiment of the present invention.

6 is a diagram for comparing SAR resolutions of a bistatic SAR system using a GNSS and a bistatic SAR system using a DMB signal according to an embodiment of the present invention.

As shown in FIG. 6, the SAR resolution (a) of the bistatic SAR system using the DMB signal of the SAR image (b) in the bistatic SAR system using the GNSS according to the embodiment of the present invention, Is higher.

FIG. 7 is a view showing an example of forming an SAR image for a surrounding terrain according to an embodiment of the present invention.

FIG. 8 is a conceptual diagram for explaining an operation example of a GNSS-based bistatic SAR system according to an embodiment of the present invention.

8, the transmitter 805 of the GNSS satellite transmits the first to fourth direct signals 801 to 804 as a reference signal to the first target 830 on the ground and the second target 840 on the air, The receiver 810 of the terrestrial bistatic SAR system platform according to an embodiment of the present invention includes a receiver 810 for receiving a third direct signal 803 and a fourth direct signal 804 in response to a third reflected signal reflected by the first target 830 ) 811 and the second direct signal 802 receives the second reflected signal 812 reflected from the second target 840 to generate the SAR image and identify the target according to the method described above.

On the other hand, the receiver 820 of the platform of the bistatic SAR system according to the embodiment of the present invention located in the air is configured such that the first direct signal 801 and the second direct signal 802 are reflected from the second target 830 1 reflection signal 813 to generate a SAR image according to the method described above and identify the target.

Also, in accordance with an embodiment of the present invention, a receiver 820 of a platform of a bistatic SAR system located in the air and a receiver 810 of a platform of a bistatic SAR system located on the ground are connected to each other via a communication link 850 from different receivers The position of the target 840 can be calculated using the identification information of the target 840 received.

As described above, the GNSS-based bistatic SAR system according to the embodiment of the present invention can be synchronized with each other over a communication link even if it is mounted on a platform located on the air, ground, or sea using GNSS signals synchronized everywhere in the world, It is also possible to operate it as an integrated site.

9 is a diagram for explaining a process of acquiring Doppler shift information generated according to movement of a target in an FFT according to an embodiment of the present invention.

Referring to FIG. 9, it can be seen that different phases can be discriminated at the same frequency by the Doppler effect according to the movement of the targets 910 and 920, and the phase change at the time of changing by the Doppler frequency can also be obtained.

FIG. 10 is a diagram for explaining applicable examples of a GNSS-based bistatic SAR system according to an embodiment of the present invention.

The GNSS-based bistatic SAR system according to the embodiment of the present invention can image and shape the sensed surrounding environment like the LiDAR equipment of the autonomous vehicle, which is currently the largest issue, such as reference numerals 1010 and 1020 .

In addition, since the GNSS-based bistatic SAR system according to the embodiment of the present invention can be mounted on a small unmanned aerial vehicle such as a drone since it can be miniaturized because there is no transmitter, It can also be used as a radar.

It is to be understood that the present invention is not limited to these embodiments, and all elements constituting the embodiment of the present invention described above are described as being combined or operated in one operation. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. In addition, although all of the components may be implemented as one independent hardware, some or all of the components may be selectively combined to perform a part or all of the functions in one or a plurality of hardware. As shown in FIG. In addition, such a computer program may be stored in a computer readable medium such as a USB memory, a CD disk, a flash memory, etc., and read and executed by a computer to implement an embodiment of the present invention. As the recording medium of the computer program, a magnetic recording medium, an optical recording medium, or the like can be included.

It will be apparent to those skilled in the art that various modifications, substitutions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. will be. Therefore, the embodiments disclosed in the present invention and the accompanying drawings are intended to illustrate and not to limit the technical spirit of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments and the accompanying drawings . The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (8)

A Bistatic Synthetic Aperture Radar (SAR) system using a Global Navigation Satellite System (GNSS)
A GNSS satellite transmitting a first signal for tracking a target; And
And a receiver for receiving a first signal transmitted directly from the GNSS satellite and a second signal, the first signal being a reflected signal reflected by the target,
The receiver includes:
An autocorrelation unit for performing autocorrelation using the autocorrelation function of the received first signal;
A window processing unit for processing a frequency-converted signal of the autocorrelated signal;
A first multiplier for masking the frequency-converted signal of the second signal and the frequency-converted signal of the first signal;
A second multiplier for multiplying the masked masking signal by the windowed autocorrelation signal and synchronizing the multiplied signal;
An inverse fast Fourier transformer for converting the synchronized frequency domain signal into a time domain; And
And a SAR image generating unit for generating an SAR image from the signal converted into the time domain by using a satellite navigation system (GNSS). The method according to claim 1,
Wherein the first signal comprises a Pseudo Random Noise (PRN) code for identifying the GNSS satellite. &Lt; Desc / Clms Page number 20 &gt; The method according to claim 1,
The receiver includes:
Further comprising a target identifying unit for generating, from the generated SAR image, target identifying information that identifies, as the target, an area converted by the image characteristic from the generated SAR image. Radar (SAR) system. The method according to claim 1,
Wherein the SAR image generator comprises:
Wherein the image of the target is generated using a Doppler difference and a signal intensity of a signal reflected from the target, and a satellite navigation system (GNSS) using the satellite navigation system (GNSS). The method according to claim 1,
The receiver includes:
Further comprising a target distance measuring unit for measuring a distance of a target using the Doppler shift characteristic of the generated SAR image. (SAR) system. The method according to claim 1,
The receiver includes:
And a synchronization detector for detecting a time synchronization of the first signal by calculating a power spectral density of the first signal using the autocorrelated signal. System (GNSS) using a bistatic synthetic aperture radar (SAR) system. 6. The method of claim 5,
The receiver includes:
Further comprising a communication link portion forming a communication link for time synchronization with another receiver mounted on a platform of the GNSS-based SAR system,
Wherein the target distance measuring unit calculates a position of the target using the identification information of the target received from the other receiver through the communication link unit. Aperture radar (SAR) system. The method according to claim 1,
The receiver includes:
A Bistatic Synthetic Aperture Radar (SAR) system using a Global Navigation Satellite System (GNSS) that is a broadband SDR (Software Defined Radio) based GNSS receiver with more than two channels.

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