KR101839041B1 - FMCW-SAR system using correction continuous motion effect and method for reconstructing SAR image using FMCW-SAR system - Google Patents

Abstract

The present invention relates to an FMCW-SAR system for restoring an SAR image from a received signal corrected for a continuous movement effect based on a matched filter mounted on a moving body moving on land, sea, . The system according to the present invention includes: an antenna position change amount calculating unit for calculating a position change amount of a radar antenna provided in an FMCW-SAR system while acquiring a reflected signal from a target in an FMCW-SAR system; An antenna position change amount reflector for reflecting a change amount of a position of a radar antenna in a time domain signal related to a received signal; A reception signal converting unit for converting a signal in a time domain reflecting the positional change amount of the radar antenna into a signal in the frequency domain; An antenna position change amount removing unit for removing a change amount of a position of a radar antenna from a signal in a frequency domain to pre-process a received signal; And a SAR image restoration unit for restoring the SAR image based on the reception signal from which the position change component of the radar antenna is removed.

Description

[0001] The present invention relates to an FMCW-SAR system using continuous motion compensation and a SAR image restoration method using the same,

The present invention relates to a SAR (Synthetic Aperture Radar) system. More particularly, to a Frequency Modulated Continuous Wave (FMCW) signal based SAR system.

The image radar field can be operated using platforms such as satellites, aircrafts, and vehicles. In this case, the conventional system is generally operated based on a relatively high-performance / high-cost chirp-pulse radar system. This is limited to meet various purposes that require low cost / high efficiency, and the level of technical completeness and required technology is very high in terms of image radar system.

The frequency modulated continuous wave (FMCW) signal based radar system has a simple system structure that can be relatively small / lightweight and can be developed at a low cost as compared with the conventional chirp pulse based system. However, compared with the conventional chirp pulse-based image radar, there is a problem in that it is technically difficult to implement the image radar system due to the difference in the modulation method of the radio wave transmitted and the technical level for implementing the system is low and the implementation of the high performance system is low.

Korean Laid-Open Patent No. 2015-0055812 (published on May 22, 2015).

SUMMARY OF THE INVENTION The present invention has been conceived to solve the problems described above. It is an object of the present invention to provide a FMCW (Frequency Modulated Continuous Wave) -SAR (Synthetic Aperture Radar) And to propose an apparatus and method for correcting a continuous movement effect of a SAR system.

The present invention also relates to an FMCW-SAR system for restoring an SAR image from a received signal corrected for a continuous movement effect based on a modified matched filter mounted on a moving body moving on land, sea, And to propose a method.

However, the objects of the present invention are not limited to those mentioned above, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

SUMMARY OF THE INVENTION The present invention has been conceived to achieve the above-mentioned object, and it is an object of the present invention to provide a radar antenna system for a FMCW-SAR system, An antenna position change amount calculating unit for calculating a position change amount of the antenna; An antenna position change amount reflector for reflecting a position change amount of the radar antenna in a time domain signal related to the received signal; A reception signal converting unit for converting the time domain signal into a frequency domain signal, the time domain signal reflecting the positional change amount of the radar antenna; And an antenna position change amount canceling unit for removing the change amount of the position of the radar antenna from the frequency domain signal to pre-process the received signal.

The present invention further provides a method for estimating a position of a radar antenna in a FMCW-SAR system, the method comprising: calculating a positional change amount of a radar antenna included in the FMCW-SAR system during acquisition of a reception signal reflected from a target; Reflecting a position change amount of the radar antenna in a time domain signal related to the received signal; Converting the signal in the time domain into a signal in the frequency domain, the signal indicating the change in position of the radar antenna; And removing the positional change amount of the radar antenna from the signal in the frequency domain to pre-process the received signal.

The present invention also provides an antenna position change amount calculation unit for calculating a position change amount of a radar antenna provided in the FMCW-SAR system while acquiring a reception signal reflected from a target in a Frequency Modulated Continuous Wave (FMCW) -SAR (Synthetic Aperture Radar) part; An antenna position change amount reflector for reflecting a position change amount of the radar antenna in a time domain signal related to the received signal; A reception signal converting unit for converting the time domain signal into a frequency domain signal, the time domain signal reflecting the positional change amount of the radar antenna; An antenna position change amount removing unit for removing a change amount of the position of the radar antenna from the frequency domain signal and pre-processing the received signal; And an SAR image reconstructing unit for reconstructing an SAR image based on the received signal from which the position-varying component of the radar antenna is removed. The present invention also provides an FMCW-SAR system using the continuous movement effect correction method.

The present invention also provides a method of calculating a positional change amount of a radar antenna provided in an FMCW-SAR system while acquiring a reception signal reflected from a target in a Frequency Modulated Continuous Wave (FMCW) -SAR (Synthetic Aperture Radar) system; Reflecting a position change amount of the radar antenna in a time domain signal related to the received signal; Converting the signal in the time domain into a signal in the frequency domain, the signal indicating the change in position of the radar antenna; Removing a variation in the position of the radar antenna from the signal in the frequency domain to pre-process the received signal; And reconstructing an SAR image based on the received signal from which the positional change component of the radar antenna is removed. The SAR image restoration method of the FMCW-SAR system using the continuous movement effect correction technique is proposed.

The present invention can achieve the following effects through the configurations for achieving the above object.

First, the present invention can improve the target blurring in the final radar reconstruction image by pre-processing the phase change component of the continuous movement effect, which can be confirmed from the signal model, from the radar source data.

Second, the present invention can accumulate relatively more power at the center of the target during image restoration by applying the modified matched filter, thereby contributing to improvement of the quality of the radar restored image as a whole.

1 is a conceptual diagram showing an FMCW-SAR geometry including a continuous movement effect.
FIG. 2 is a table diagram of FMCW-SAR system configuration for simulation.
3 is a reference diagram for explaining the characteristic of the target time delay (tau) by the continuous movement effect.
4 is a reference diagram for explaining the distance compression signal s (w, u) to which the continuous moving effect is applied.
5 is a reference diagram for explaining a process of processing a continuous movement effect correction signal.
6 is a reference diagram for explaining the modified SAR image restoration applied to the matched filter.
7 is a table diagram illustrating an aircraft-based FMCW-SAR system specification.
FIG. 8 is a graph showing a result of comparative analysis of the continuous moving effect correction performance of the FMCW-SAR system.
FIG. 9 is a table showing the results of continuous motion effect correction signal processing. FIG.
Fig. 10 is a reference diagram for explaining the improvement of the test target dispersion power characteristic.
FIG. 11 is a conceptual diagram schematically illustrating an internal structure of a continuous movement effect correction apparatus provided in an FMCW-SAR system according to a preferred embodiment of the present invention.
12 is a flowchart schematically showing a continuous moving effect correction method according to a preferred embodiment of the present invention.
FIG. 13 is a conceptual diagram schematically showing an internal configuration of an FMCW-SAR system according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the 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. In addition, the preferred embodiments of the present invention will be described below, but it is needless to say that the technical idea of the present invention is not limited thereto and can be variously modified by those skilled in the art.

The frequency modulated continuous wave (FMCW) signal-based radar system has been widely studied for various research / practical purposes in recent years due to its advantages in size and weight reduction compared to the existing chirp-pulse based radar system. In particular, various radar imaging signal processing techniques have been studied in consideration of the shortcoming / disadvantage of the system side in the application to a SAR (Synthetic Aperture Radar) system for acquiring radar images.

In the present invention, a continuous motion effect correction technique based on FMCW signal characteristics is proposed.

Unlike the conventional chirp-pulse system, when the FM modulation signal is transmitted and received in the CW mode, the signal transmission / reception period is relatively long and the transmission / reception is continuously performed in the same period. At this time, the transmission / reception signal process is physically performed simultaneously with the continuous movement of the image radar platform, and the relative movement speed of the image radar platform due to the FMCW signal characteristic affects the received signal. This is due to the limitation of the FMCW-SAR system, which is more prominent in the conventional chirp-pulse system, and it is an object of the present invention to improve this to obtain a high-quality radar image.

The present invention is a technique for eliminating the continuous moving effect that reflects the frequency-modulated continuous wave (FM-CW) signal characteristic and the physical movement of the radar platform in the FMCW-SAR image radar system. We propose a time-Doppler domain signal processing technique to model the continuous motion effect mathematically for continuous motion compensation and remove it. In addition, the quality of the final radar reconstruction image is improved by adding a modified matched filter process based on the signal model to the radar image reconstruction process based on the back-projection algorithm (BPA).

In other words, the continuous motion effect correction technique proposed in the present invention is a technique of correcting the phase change component during the data acquisition time (t) from the relative speed (v _r ) of the radar platform in the time- This is a technique to improve the radar image quality in two steps by applying a modified matched filter once more in the radar image reconstruction process based on the back-projection algorithm.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings.

The SAR system based on the FMCW signal is characterized in that the transmission and reception of radar signals are continuously performed in the same modulation period, and there is a problem that the continuous motion effect of the transmitting and receiving antennas is relatively prominent depending on the system configuration. It is necessary to analyze the continuous motion effect using the FMCW signal model and apply the optimized image restoration technique because it acts as a factor to degrade the image quality in the image restoration using the back-projection algorithm used for the SAR image restoration of the aircraft-based system. Do.

For this, in the present invention, the phase change of the radar received signal due to the continuous movement effect is analyzed through the FMCW-SAR signal model. The phase shift due to the continuous motion effect can be eliminated by the signal processing technique of the time-Doppler (t, k _u ) region and applied to the distance compression signal for image reconstruction. We applied a modified matched filter for continuous motion correction to the back-projection algorithm applied for SAR image reconstruction and applied the results to observation data of real aircraft-based SAR system to verify the results of continuous motion correction.

In the present invention, the FMCW-SAR signal model, the continuous motion effect and the correction result using the FMCW-SAR signal model are simulated, and the modified application example of the back-projection algorithm is applied to the FMCW-SAR signal model, , And experimental results.

1. FMCW-SAR signal model

The FMCW-SAR signal model can be used as a useful tool for analyzing system characteristics and simulating radar source signal generation and image reconstruction. In particular, the continuous antenna position change characteristic of the FMCW-SAR system can be expressed as shown in FIG. 1, and the antenna position and the target function can be represented by u and f (x, y), respectively.

(1) FMCW signal model

The FMCW signal model can be expressed as a sawtooth-shaped frequency modulated signal using an operating frequency (f ₀ ) and a frequency modulation rate (K _r = bandwidth / modulation period) (2) using Equation (2). At this time, the target delay time is calculated from the distance R between the target position (x _i , y _j ) and the antenna position (u) as shown in Equation (3).

Where R (u) is the distance between the target and the antenna. Also, c means luminous flux (3 x 10 ⁸ m / s).

The radar system based on the FMCW signal frequency downconverts the transmission and reception signals through a frequency mixer and samples a beat frequency component corresponding to a difference between the two signals and uses the same in an image reconstruction process. This process is summarized in Equation (4) and used as a reception signal of the FMCW-SAR system in the next process.

In Equations (1), (2) and (4), signal strength components are omitted for convenience of description, and antenna beam patterns, target distances and reflectivities must be considered for simulation.

(2) Continuous motion effect signal model

The continuous motion effect to be considered in the FMCW-SAR system is that the position of the antenna is continuously moved even during the transmission and reception of the radar signal, and the start-stop approximation method in which the antenna position is approximated to the stationary position, have.

In order to compensate for this, in the present invention, the antenna position change with time is modified as follows considering the moving speed of the aircraft (v _r ) and the sweep time.

u → u - v _r t

As shown in Equation (5), the existing distance function R (u) expressed by the stationary antenna position for each transmission signal is a distance function of the two-dimensional array added with the details of the antenna position change with time R (t, u).

Equation (6) is expressed as a signal of a spatial frequency (k _r = 2? /?) Region for a distance component using a modified distance function R (t, u) including a continuous movement effect. In this case, the received signal in the spatial frequency domain including the antenna position change is placed in the Fourier inverse relation of the distance information represented by the bit frequency spectrum, which is the signal in the same region as the time domain.

Therefore, the continuous motion effect can be added to the time domain signal for Equation (3) and can be summarized as Equation (6). The process of converting this into a signal of the time-Doppler S (t, k _u ) region is as shown in Equations (7) and (8).

K _u denotes a wave number of a Doppler frequency generated according to an antenna position change. Also,? Refers to the overall phase of the FMCW system.

Equation (7) shows a Fourier transform process to the Doppler (k _u ) region, which is a process of applying a variable permutation (u '= u - v _r t) and a stationary phase approximation, 8, the resultant expression of the expression (7) can be obtained as the following expression (9).

The final equation above is the continuous motion effect applied signal model, which is divided into the phase change part according to the aircraft moving speed (the first term on the right side of Equation 9) and the target phase function of the Doppler domain.

(3) Time-Doppler (t, k _u ) region signal processing technique

In Equation (9), the phase component representing the continuous movement effect according to the moving speed of the aircraft is exp {-jk _u (v _r t)}, and the process for eliminating the phase component is transforming the received signal into a time-Doppler region And multiplying the complex conjugate of the phase component of the continuous motion effect.

The process of converting the input signal of the back-projection algorithm for SAR image restoration into the distance compressed signal area is as shown in Equation (11). At this time, ω = 2πf, which represents a frequency-domain signal for indicating distance information.

2. Simulation of continuous movement effect

In order to analyze the characteristics of the continuous movement effect of the aircraft based FMCW-SAR system and to correct it, a simulation using the FMCW signal model and the time-Doppler s (t, k _u ) region signal processing technique was performed. A back-projection algorithm was used to reconstruct the image, and it was set to have a wider antenna radiation pattern to effectively represent the continuous movement effect in the reconstructed image (see FIG. 2). FIG. 2 is a table diagram of FMCW-SAR system configuration for simulation.

(1) continuous moving effect applied distance compressed signal

The continuous movement effect generated in the FMCW-SAR system can be confirmed from Equation (5) showing the distance change between the target and the antenna.

3 is a reference diagram for explaining the characteristic of the target time delay (tau) by the continuous movement effect. Fig. 3 (a) is a general view of the target time delay characteristic, and Fig. 3 (b) is a partial enlarged view of the target time delay characteristic.

Fig. 3 is a graph showing the change in the position of the antenna according to time (τ (t, u) = 2 / c × R (t, u) It can be confirmed that the center point moves in the azimuth direction by drawing the sampling time and the continuous position change (1024) of the antenna according to each sampling time.

4 is a reference diagram for explaining the distance compression signal s (w, u) to which the continuous moving effect is applied. 4 (a) and 4 (b) simulate the distance compressed signal s (w, u) of the radar source signal generated using the target delay time modeled as a function of the preceding measurement time and antenna position, .

(2) continuous motion effect correction signal processing

Simulation using equations (3) to (5) confirmed the continuous movement effect of the FMCW-SAR system in which the target trajectory moves in the azimuthal direction. In order to analyze the effect of the continuous motion on the reconstructed SAR image, we used the back-projection algorithm to reconstruct the radar source signal into a SAR image.

5 is a reference diagram for explaining a process of processing a continuous movement effect correction signal. 5 (a) shows a reference SAR image, and FIG. 5 (b) shows a continuous moving image SAR image. And FIG. 5 (c) shows a time-Doppler domain signal processing SAR image.

FIG. 5 illustrates a signal processing procedure for correcting the continuous movement effect of the FMCW-SAR system. The reference SAR image is obtained by restoring the radar source signal generated by the start-stop approximation technique a) reference), SAR images (restoring the radar raw signal applied to the continuous movement effects, see (b) of FIG. 5), and the continuous time for the movement effect correction-Doppler s (t, k _u) domain signal processing techniques The applied SAR image (see FIG. 5C) is shown in FIGS. 5A to 5C, respectively.

At this time, the image reconstructed with finer resolution than the simulation setting resolution of 30 cm was enlarged based on the target center point to accurately show the dispersion characteristics of the target.

The reconstructed image using the radar source signal (signal shown in (b) of FIG. 5) to which the continuous movement effect is applied exhibits a characteristic in which the dispersion power pattern of the target relative to the reference image spreads in the direction of the distance, Shows a characteristic in which the target distributed power pattern is distorted with a proportional distorted phase component.

In order to remove the phase change component of the continuous movement effect proportional to the aircraft moving speed and the sampling time, the time-Doppler domain signal processing technique of Equations 10 and 11 described above is applied to the back projection algorithm input signal, The results of continuous motion correction such as. The result of the continuous motion correction using the time-Doppler domain signal processing scheme can be confirmed that the target distributed power pattern in the distance direction is very similar to the pattern characteristic of the reference image as shown in the left and right patterns of FIG. 5 (c).

In the present invention, it is also possible to apply a modified matched filter to the back-projection algorithm used for image restoration in order to further enhance the image restoration improvement effect of the central point portion of the target.

(3) BPA restoration image using modified matched-filter

Equation (12) shows the matched filter process of the existing back-projection algorithm. The target delay time t _d of the reconstructed image can be calculated using the distance between the antenna position u and the target in the reconstructed image, that is, each pixel, u is treated as M stationary antenna positions.

On the other hand, the modified matched filter process for correcting the continuous motion effect can be transformed into a target delay time characteristic function with a change according to time t as shown in Equation (13) The input information u _m is subdivided by the number N of time samples t _n and the distributed power of the target is accumulated by the added antenna position information.

The modified matched filter process of Equation (13) has a disadvantage in that the computation amount of the existing back-projection algorithm is increased by N times in the image restoration process using the antenna detail position proportional to the number of time samples N. However, The correction accuracy can be maintained and the calculation efficiency can be compensated for.

In other words, the modified matched filter for the correction of the continuous motion effect is obtained by adding the detailed position input information (v _r t _n ) considering the aircraft moving speed and time change to the existing antenna position input information (u _m ) It is possible to obtain improved target dispersion power characteristics by adding input information about 5 ~ 10 times (ex. N / 10 ~ N / 100 ratio simulation)

FIG. 6 is a reference diagram for explaining reconstruction of a reconstructed SAR images applied to the continuous motion correction. FIG.

6 (a) is a result of image restoration of a back-projection algorithm in which the radar distance compression signal corrected for the continuous motion effect phase component in the time-Doppler s (t, k _u ) region is input. According to Fig. 6 (a), it is possible to confirm the result that the distributed power characteristic of the target is more concentrated at the center point by using the modified matched filter.

6 (b) and 6 (c) illustrate the modified SAR image using the matched filter in a range direction (see FIG. 6 (b)) and an azimuth direction (see FIG. 6 And compared with the reference SAR image before and after the continuous motion effect (CME) correction. As a result, when applying the phase change correction method (CMC) and the modified matched filter (MF) in the time-Doppler domain, the distance / azimuth direction resolution was 37.2 cm / 6.5 cm before correction and 30.1 cm / 8.9 cm after correction And it is confirmed that the improvement of the resolution in the direction of the distance and the improvement of the dispersion power characteristic near the center point of the target are obtained.

3. Experimental Results

FMCW-SAR system continuous moving effect correction method In order to compare / verify the performance, on-site observation data using the aircraft based FMCW-SAR system were utilized. The FMCW-SAR system applied to this experiment is optimized for low-altitude / near-field flight experiments and operates in a delayed-de-chirp mode to improve operation efficiency. This includes a range offset of about 480 m in a manner to more efficiently use a relatively low sampling frequency (f _s = 1.2 MHz) and a small number of samples (1024 points) as shown in Fig. 7 . 7 is a table diagram illustrating an aircraft-based FMCW-SAR system specification.

Observation data used for verification of continuous moving effect correction technique were measured in the vicinity of the landfill, and a test target (triangular passive reflector, size 50 cm) was installed on a wide flat ground and its characteristics were analyzed from the reconstructed image.

FIG. 8 is a graph showing a result of comparative analysis of the continuous moving effect correction performance of the FMCW-SAR system. 8 (a) shows the SAR reconstruction image of the test area, FIG. 8 (b) shows the enlarged image before the calibration for the test target installation area, and FIG. 8 (c) The enlarged image after correction is shown.

The results of the correction performance analysis using the test target are shown in FIG. 9, and the dispersion power characteristics of the test target in the restored image can be confirmed as shown in FIG. In this case, the theoretical slant-range resolution is about 31 cm, and the ground distance resolution is about 44 cm when the target propagation angle is considered. The result is lower than -20 dB of the general PSLR (Peak-Sidelobe Ratio) Respectively.

4. Conclusion

In the present invention, a modified matched filter technique of the time-Doppler s (t, k _u ) region signal processing technique and a back-projection algorithm for SAR image reconstruction is proposed to correct the continuous movement effect of the FMCW- Simulation using the FMCW signal model was performed to verify the motion effect correction. In addition, we used actual aircraft based FMCW-SAR primitive data to verify the performance of the proposed continuous motion compensation technique. The analysis result showed that the distance resolution improvement (measured value: 51cm, theoretical value: 44cm) and PSLR improvement of 2 ~ 3dB .

FMCW radar is used in RAR (Real Aperture Radar) system such as altimeter, scatterometer and so on. It can be used for distance measurement and backscattering coefficient measurement. Especially, application to SAR system for generating radar composite image in the field of microwave remote sensing is also actively underway, and the present invention is expected to be a high-quality image synthesis technology in the field of aircraft-based FMCW-SAR image radar.

The present invention described above can be applied to the SAR image signal processing field. For example, the present invention can be applied to the maritime SAR (SAR) image signal processing field in the sea.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention has been described with reference to Figs. Best Mode for Carrying Out the Invention Hereinafter, preferred forms of the present invention that can be inferred from the above embodiment will be described.

FIG. 11 is a conceptual diagram schematically illustrating an internal structure of a continuous movement effect correction apparatus provided in an FMCW-SAR system according to a preferred embodiment of the present invention.

11, an apparatus 100 for correcting a continuous movement effect of a frequency modulated continuous wave (FMCW) -SAR (Synthetic Aperture Radar) system according to a preferred embodiment of the present invention includes an antenna position change amount calculation unit 110, A reception signal converting unit 130, an antenna position change amount removing unit 140, a first power source unit 150, and a first main control unit 160. [

The first power supply unit 150 performs a function of supplying power to each configuration of the continuous movement effect correction apparatus 100 of the FMCW-SAR system.

The first main control unit 160 performs a function of controlling the overall operation of each configuration of the continuous movement effect correction apparatus 100 of the FMCW-SAR system.

The antenna position change amount calculation unit 110 calculates a position change amount of a radar antenna provided in the FMCW-SAR system while acquiring a reception signal reflected from a target in the FMCW-SAR system.

The antenna position change amount calculation unit 110 calculates the position change amount of the radar antenna based on the moving speed of the moving body equipped with the FMCW-SAR system, the data collection time required to obtain the reception signal after outputting the transmission signal as the target, Can be calculated.

The antenna position change amount reflection unit 120 reflects the position change amount of the radar antenna in the time domain signal related to the received signal.

The reception signal conversion unit 130 performs a function of converting a signal in the time domain in which the amount of change in the position of the radar antenna is reflected to a signal in the frequency domain.

The reception signal converting unit 130 may convert a time domain signal into a frequency domain signal using a Fourier transform. The reception signal converting unit 130 may convert a time domain signal into a frequency domain signal by applying a second distance function and a stationary phase approximation when using Fourier transform. The second distance function is obtained by reflecting the difference value between the first value and the second value in the first distance function. The first distance function means a function related to the distance between the target and the radar antenna. The first value means a multiplication value of the movement speed of the moving body and the data acquisition time. The second value means a distance value between the target and the radar antenna .

The antenna position change amount removing unit 140 performs a function of removing the positional change amount of the radar antenna from the frequency domain signal and pre-processing the received signal.

The antenna position change amount removing unit 140 may remove the position change amount of the radar antenna by multiplying the phase component related to the position change amount of the radar antenna with the complex conjugate of the phase component in the frequency domain signal.

The continuous movement effect correcting apparatus 100 of the FMCW-SAR system may further include a back projection algorithm executing unit 170. [

The back projection algorithm executing unit 170 performs a post-processing of a received signal from which the positional variation of the radar antenna is removed based on a back projection algorithm using a matched filter related to the delay time of the received signal .

The back projection algorithm executing unit 170 may modify the matched filter based on the moving speed of the moving body including the FMCW-SAR system, the number of time samples, and the position of the radar antenna associated with each time sample.

Next, an operation method of the continuous movement effect correcting apparatus 100 of the FMCW-SAR system will be described.

12 is a flowchart schematically showing a continuous moving effect correction method according to a preferred embodiment of the present invention. The following description refers to Fig. 11 and Fig.

First, the antenna position change amount calculation unit 110 calculates a position change amount of the radar antenna provided in the FMCW-SAR system while acquiring the reception signal reflected from the target in the FMCW-SAR system (S210).

Thereafter, the antenna position change amount reflection unit 120 reflects the position change amount of the radar antenna in the time domain signal related to the received signal (S220).

Thereafter, the reception signal converting unit 130 converts the time domain signal reflecting the position change amount of the radar antenna into the frequency domain signal (S230).

Then, the antenna position change amount removing unit 140 removes the positional change amount of the radar antenna from the frequency domain signal and preprocesses the received signal (S240).

On the other hand, the back projection algorithm executing unit 170 can post-process the received signal from which the positional change amount of the radar antenna is removed based on the back projection algorithm using the matched filter related to the delay time of the received signal. This step may be performed after step S240.

Next, the FMCW-SAR system will be described.

FIG. 13 is a conceptual diagram schematically showing an internal configuration of an FMCW-SAR system according to a preferred embodiment of the present invention.

Referring to FIG. 13, an FMCW-SAR system 300 according to a preferred embodiment of the present invention includes a continuous movement effect correction apparatus 100, an SAR image restoration unit 310, and a second main control unit 320.

The second main control unit 320 functions to control the overall operation of each configuration of the FMCW-SAR system 300.

The continuous movement effect correction apparatus 100 has been described above, and a detailed description thereof will be omitted here.

The SAR image reconstructing unit 310 performs a function of reconstructing an SAR image based on a received signal from which the position change component of the radar antenna is removed.

Next, an operation method of the FMCW-SAR system 300 will be described.

First, the continuous movement effect correction apparatus 100 calculates a position change amount of the radar antenna provided in the FMCW-SAR system 300 while acquiring the reception signal reflected from the target in the FMCW-SAR system 300 (STEP A) .

Thereafter, the continuous movement effect correction apparatus 100 reflects the positional change amount of the radar antenna in the time domain signal related to the received signal (STEP B).

Then, the continuous movement effect correcting apparatus 100 converts the signal in the time domain reflecting the position change amount of the radar antenna into the signal in the frequency domain (STEP C).

Then, the continuous movement effect correction apparatus 100 removes the positional variation of the radar antenna from the frequency domain signal and preprocesses the received signal (STEP D).

Thereafter, the SAR image restoring unit 310 restores the SAR image based on the received signal from which the position change component of the radar antenna is removed (STEP E).

On the other hand, the continuous movement effect correcting apparatus 100 can post-process the received signal from which the positional change amount of the radar antenna is removed based on the back projection algorithm using the matched filter related to the delay time of the received signal. This step can be performed between STEP D and STEP E.

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.

Furthermore, all terms including technical or scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined in the Detailed Description. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

It will be apparent to those skilled in the art that various modifications, changes, and substitutions are possible, without departing from the essential characteristics 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 (12)

An antenna position change amount calculating unit for calculating a position change amount of a radar antenna provided in the FMCW-SAR system while acquiring a reception signal reflected from a target in a Frequency Modulated Continuous Wave (FMCW) -SAR (Synthetic Aperture Radar) system;
An antenna position change amount reflector for reflecting a position change amount of the radar antenna in a time domain signal related to the received signal;
A reception signal converting unit for converting the time domain signal into a frequency domain signal, the time domain signal reflecting the positional change amount of the radar antenna;
Domain signal by multiplying the phase component related to the amount of change in the position of the radar antenna by the complex conjugate of the phase component in the signal in the frequency domain to remove the positional variation of the radar antenna from the signal in the frequency domain, An antenna position change amount removing unit that removes a position change amount of the antenna; And
An SAR image restoring unit for restoring an SAR image based on the received signal from which the position change component of the radar antenna is removed,
And the FMCW-SAR system using the continuous motion effect correction technique. The method according to claim 1,
The antenna position change amount calculation unit calculates a position change amount of the radar antenna based on the moving speed of the moving body including the FMCW-SAR system and the data collection time required to obtain the received signal after outputting the transmission signal to the target FMCW-SAR system using continuous motion effect correction technique. 3. The method of claim 2,
Wherein the reception signal converting unit converts the time domain signal into the frequency domain signal using a Fourier transform and a first distance function related to the distance between the target and the radar antenna when using the Fourier transform, A second distance function reflecting a difference value between a moving speed and a data acquisition time, and a distance value between the target and the radar antenna, and a stationary phase approximation, And a signal of the frequency domain is converted into a signal of the frequency domain. delete The method according to claim 1,
A back projection algorithm executing unit for post-processing the received signal from which a positional change amount of the radar antenna is removed based on a back projection algorithm using a matched filter related to a delay time of the received signal;
Wherein the FMCW-SAR system uses the continuous motion effect correction technique. 6. The method of claim 5,
Wherein the back projection algorithm performing unit modifies and uses the matched filter based on the moving speed of the moving body including the FMCW-SAR system, the number of time samples, and the position of the radar antenna associated with each time sample. FMCW-SAR system using effect correction techniques. Calculating a position change amount of a radar antenna provided in the FMCW-SAR system while acquiring a reception signal reflected from a target in a Frequency Modulated Continuous Wave (FMCW) -SAR (Synthetic Aperture Radar) system;
Reflecting a position change amount of the radar antenna in a time domain signal related to the received signal;
Converting the signal in the time domain into a signal in the frequency domain, the signal indicating the change in position of the radar antenna;
Domain signal by multiplying the phase component related to the amount of change in the position of the radar antenna by the complex conjugate of the phase component in the signal in the frequency domain to remove the positional variation of the radar antenna from the signal in the frequency domain, Removing the positional change amount of the received signal and preprocessing the received signal; And
And restoring an SAR image based on the received signal from which the positional change component of the radar antenna is removed
Wherein the SAR image is reconstructed by using the continuous motion effect correction technique. 8. The method of claim 7,
Wherein the calculating step calculates a position change amount of the radar antenna based on a moving speed of the moving body including the FMCW-SAR system and a data acquisition time required to acquire the reception signal after outputting the transmission signal to the target A SAR image reconstruction method using the continuous motion effect correction technique. 9. The method of claim 8,
Wherein the converting comprises converting the time domain signal into a frequency domain signal using a Fourier transform, and using a Fourier transform to determine a first distance function related to a distance between the target and the radar antenna, A second distance function reflecting a difference value between a moving speed and a data acquisition time, and a distance value between the target and the radar antenna, and a stationary phase approximation, And a signal of the frequency domain is transformed into a signal of the frequency domain. delete 8. The method of claim 7,
Post-processing the received signal from which the amount of positional change of the radar antenna is removed based on a back projection algorithm using a matched filter related to the delay time of the received signal
The SAR image restoration method of claim 1, further comprising: 12. The method of claim 11,
Wherein the post-processing step modifies and uses the matched filter based on a moving speed of the moving body including the FMCW-SAR system, a number of time samples, and a position of the radar antenna associated with each time sample. SAR image restoration method of FMCW-SAR system using effect correction technique.

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