SAR (Synthetic Aperture Radar) system hyperspectral characteristic testing method based on narrowband calibration fitting

Abstract

The invention provides an SAR system hyper-spectrum characteristic testing method based on narrowband calibration fitting, and belongs to the technical field of hyper-spectrum testing. The method comprises the following steps: S1, configuring an SAR system; the SAR system comprises a transmitting link and a receiving link. S2, a signal is transmitted to a space through a transmitting link, the signal is captured by a receiving link after being reflected by a ground object, and a hyperspectral characteristic model is constructed based on the transmitted signal and the received signal; s3, based on the calibration link of the SAR system, executing a hyperspectral characteristic test by using the hyperspectral characteristic model; the calibration link comprises a transmitting calibration link, a receiving calibration link and a reference calibration link. According to the method, the efficiency and the precision of the hyperspectral characteristic test of the SAR system can be effectively improved, and the test application scene is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of hyperspectral testing, and particularly relates to a method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration fitting. Background Art

[0002] SAR can obtain two-dimensional high-resolution images of the range dimension and azimuth dimension of the irradiated area. Due to its characteristics such as all-weather, all-time, two-dimensional high-resolution, and strong penetration ability, it is widely used in fields such as environmental protection, topographic mapping, and disaster monitoring.

[0003] The hyperspectral characteristics of a SAR system refer to the response characteristic curve of the SAR system to signals of different frequencies within the band. As an important characteristic of the system, it affects the imaging efficiency and image interpretation efficiency of the SAR. The testing and extraction of the hyperspectral characteristics of the SAR system are important bases for SAR image analysis, and the stability of the hyperspectral characteristics of the SAR system directly affects the spectral quality of the SAR image. Summary of the Invention

[0004] The purpose of the present invention is to propose a testing scheme for the hyperspectral characteristics of a SAR system based on narrowband calibration fitting. This scheme is mainly aimed at broadband spaceborne SAR systems and involves the design of spaceborne SAR calibration systems and calibration methods. This scheme can also be applied to other satellite payloads.

[0005] The first aspect of the present invention proposes a method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration fitting, and the method includes:

[0006] Step S1, configure the SAR system; the SAR system includes a transmitting link and a receiving link;

[0007] Step S2, transmit a signal into space through the transmitting link, and after the signal is reflected by the ground object, it is captured by the receiving link, and a hyperspectral characteristic model is constructed based on the transmitted signal and the received signal;

[0008] Step S3, based on the calibration link of the SAR system, perform hyperspectral characteristic testing using the hyperspectral characteristic model; the calibration link includes a transmitting calibration link, a receiving calibration link, and a reference calibration link.

[0009] According to the method of the first aspect of the present invention, in step S1, the transmitting link of the configured SAR system includes a signal generator, a transmitter, a power divider, a duplexer, and an antenna; the receiving link of the configured SAR system includes an antenna, a duplexer, a power divider, a receiver, and an AD acquisition module.

[0010] According to the method of the first aspect of the present invention, in step S2, when the SAR system is in the working state, a signal waveform is generated by a signal generator, transmitted into space after being modulated by the transmitting link, reflected by the ground object and then returned to the SAR system, amplified and collected by the receiving link to form a digital signal, and processed to form a SAR image to obtain ground object information, so as to establish a hyper-spectrum characteristic model of the SAR system, and this model is used to test the frequency response characteristics of the transmitting link and the receiving link of the SAR system.

[0011] According to the method of the first aspect of the present invention, the transmitting calibration link means that the signal goes through the transmitting link to the front end of the antenna and the coupled signal flows back to the receiver through the internal calibrator. The transmitting calibration is used to test the hyper-spectrum characteristics of the transmitting link + internal calibrator of the SAR system; the receiving calibration link means that the signal goes through the internal calibrator to the coupling port at the front end of the antenna and flows back to the receiver through the receiving link. The receiving calibration is used to test the hyper-spectrum characteristics of the receiving link + internal calibrator of the SAR system; the reference calibration link means that the signal directly returns to the receiver through the internal calibrator. The reference calibration is used to test the hyper-spectrum characteristics of the internal calibrator of the SAR system.

[0012] According to the method of the first aspect of the present invention, in step S3, performing the hyper-spectrum characteristic test based on the calibration link of the SAR system specifically includes:

[0013] Segment the bandwidth of the SAR system;

[0014] Control the calibration parameters of the SAR system. For the first segment of narrowband signal, perform the transmitting calibration test, receiving calibration test, and reference calibration test respectively;

[0015] Extract the frequency response characteristics from the test results. Among them, the frequency response characteristic of the transmitting link is equal to the difference between the transmitting calibration signal characteristic and the reference calibration signal characteristic, and the frequency response characteristic of the receiving link is equal to the difference between the receiving calibration signal characteristic and the reference calibration signal characteristic;

[0016] Repeat the above tests, and perform tests on the second segment to the nth segment of narrowband signals respectively to obtain the frequency response characteristics of the transmitting link and the receiving link under each narrowband signal;

[0017] Perform the above tests using broadband signals to obtain the frequency response characteristics of the transmitting link and the receiving link of the SAR system under broadband signals;

[0018] Refer to the broadband frequency response characteristics, fit the narrowband characteristics, and obtain the hyper-spectrum characteristics of the transmitting link and the receiving link.

[0019] The second aspect of the present invention proposes a hyper-spectrum characteristic test device for a SAR system based on narrowband calibration fitting. The device includes a processing unit, and the processing unit is configured to execute:

[0020] Configure the SAR system; the SAR system includes a transmitting link and a receiving link;

[0021] Transmit a signal into space through the transmitting link. After being reflected by the ground object, the signal is captured by the receiving link, and a hyperspectral characteristic model is constructed based on the transmitted signal and the received signal;

[0022] Based on the calibration link of the SAR system, perform hyperspectral characteristic tests using the hyperspectral characteristic model; the calibration link includes a transmitting calibration link, a receiving calibration link, and a reference calibration link.

[0023] According to the device of the second aspect of the present invention, the transmitting link of the SAR system includes a signal generator, a transmitter, a power divider, a duplexer, and an antenna; the receiving link of the SAR system includes an antenna, a duplexer, a power divider, a receiver, and an AD acquisition module.

[0024] According to the device of the second aspect of the present invention, when the SAR system is in the working state, a signal waveform is generated by the signal generator, modulated by the transmitting link and then transmitted into space. After being reflected by the ground object, the signal returns to the SAR system, is amplified and acquired by the receiving link to form a digital signal, and after being processed, a SAR image is formed to obtain ground object information, so as to establish a hyperspectral characteristic model of the SAR system, and this model is used to test the frequency response characteristics of the transmitting link and the receiving link of the SAR system.

[0025] According to the device of the second aspect of the present invention, the transmitting calibration link means that the signal passes through the transmitting link to the front end of the antenna and the coupled signal flows back to the receiver through the internal calibrator. The transmitting calibration is used to test the hyperspectral characteristics of the transmitting link + internal calibrator of the SAR system; the receiving calibration link means that the signal passes through the internal calibrator to the coupling port at the front end of the antenna and flows back to the receiver through the receiving link. The receiving calibration is used to test the hyperspectral characteristics of the receiving link + internal calibrator of the SAR system; the reference calibration link means that the signal directly returns to the receiver through the internal calibrator. The reference calibration is used to test the hyperspectral characteristics of the internal calibrator of the SAR system.

[0026] According to the device of the second aspect of the present invention, performing the hyperspectral characteristic test based on the calibration link of the SAR system specifically includes:

[0027] Segment the bandwidth of the SAR system;

[0028] Control the calibration parameters of the SAR system, and for the first segment of narrowband signal, perform transmitting calibration test, receiving calibration test, and reference calibration test respectively;

[0029] Extract the frequency response characteristics from the test results, where the frequency response characteristic of the transmitting link is equal to the difference between the transmitting calibration signal characteristic and the reference calibration signal characteristic, and the frequency response characteristic of the receiving link is equal to the difference between the receiving calibration signal characteristic and the reference calibration signal characteristic;

[0030] Repeat the above tests on the narrowband signals from the second paragraph to the nth paragraph respectively to obtain the frequency response characteristics of the transmitting link and the receiving link under each narrowband signal;

[0031] Conduct the above tests using broadband signals to obtain the frequency response characteristics of the transmitting link and the receiving link of the SAR system under broadband signals;

[0032] Refer to the broadband frequency response characteristics to fit each narrowband characteristic to obtain the hyper-spectrum characteristics of the transmitting link and the receiving link.

[0033] The technical solution proposed by the present invention has the following advantages: (1) Testing is based on the original calibrator of the SAR system, without the need for additional testing equipment; (2) The testing method is consistent with the calibration of the SAR system, without the need for additional testing software; (3) The test data can be directly processed using the data processing program for SAR system calibration; (4) The high precision of the SAR calibrator itself and the method of narrowband segmentation fitting ensure the accuracy of the hyper-spectrum characteristic test of the SAR system; (5) It can be applied in orbit. Through out-of-orbit external calibration, the on-orbit test of the hyper-spectrum characteristics of the SAR system can be realized, and through in-orbit internal calibration, the on-orbit stability monitoring of the hyper-spectrum characteristics of the SAR system can be realized. Description of the Drawings

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 It is a schematic diagram of the composition of the SAR system according to an embodiment of the present invention.

[0036] Figure 2 It is a schematic diagram of the hyper-spectrum characteristic model of the SAR system according to an embodiment of the present invention.

[0037] Figure 3a It is a schematic diagram of the in-orbit calibration link (reference calibration link) of the SAR system according to an embodiment of the present invention.

[0038] Figure 3b It is a schematic diagram of the in-orbit calibration link (receiving calibration link) of the SAR system according to an embodiment of the present invention.

[0039] Figure 3c It is a schematic diagram of the in-orbit calibration link (transmitting calibration link) of the SAR system according to an embodiment of the present invention. Detailed Embodiments

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The test of the hyper-spectral characteristics of the SAR system needs to be realized through end-to-end tests of individual point-frequency signals on the ground. The test volume is large, the test process is complex, there is a large amount of test data, and the accuracy of the test process cannot be guaranteed. The spaceborne SAR system does not yet have the conditions for on-orbit testing. In response to this, the present invention proposes a test scheme for the hyper-spectral characteristics of the SAR system based on narrowband calibration fitting, which can effectively improve the efficiency and accuracy of the test of the hyper-spectral characteristics of the SAR system and broaden the test application scenarios.

[0042] As Figure 1 shown, a typical SAR system can be divided into two parts: a transmitting link and a receiving link. The transmitting link includes a signal generator, a transmitter, a power divider, a duplexer, an antenna, etc., and the receiving link includes an antenna, a duplexer, a power divider, a receiver, AD acquisition, etc.

[0043] As Figure 2 shown, when the SAR system works, a waveform is generated by the signal generator, modulated by the transmitting link and then transmitted into space. The signal returns to the SAR system after being reflected by the ground object, is amplified and collected by the receiving link to form a digital signal, and finally processed into a SAR image to obtain ground object information. According to the above process, a hyper-spectral characteristic model of the SAR system is established to test the frequency response characteristics of the transmitting link and the receiving link of the SAR system.

[0044] As Figures 3a - 3c shown, the internal calibration of the SAR system includes three types: transmitting calibration, receiving calibration, and reference calibration. Among them: the transmitting calibration link is that the signal passes through the transmitting link to the front end of the antenna, and the coupled signal flows back to the receiver through the internal calibrator. Transmitting calibration can test the hyper-spectral characteristics of the transmitting link + internal calibrator of the SAR system; the receiving calibration link is that the signal passes through the internal calibrator to the front-end coupling port of the antenna and flows back to the receiver through the receiving link. Receiving calibration can test the hyper-spectral characteristics of the receiving link + internal calibrator of the SAR system; the reference calibration link is that the signal directly returns to the receiver through the internal calibrator. Reference calibration can test the hyper-spectral characteristics of the internal calibrator of the SAR system.

[0045] Combining the above three calibration links, the hyper-spectral characteristics of the SAR system are tested according to the following steps:

[0046] (1) Reasonably segment the bandwidth of the SAR system;

[0047] (2) Control the calibration parameters of the SAR system, set it as the narrowband signal in the first segment, and conduct transmit calibration tests, receive calibration tests, and reference calibration tests respectively;

[0048] (3) Extract the frequency response characteristics from the test results, where the frequency response characteristic of the transmit link = transmit calibration signal characteristic - reference calibration signal characteristic, and the frequency response characteristic of the receive link = receive calibration signal characteristic - reference calibration signal characteristic;

[0049] (4) Repeat the above tests, conduct tests on the narrowband signals in the second segment to the nth segment respectively, and obtain the frequency response characteristics of the transmit link and the receive link under each narrowband signal;

[0050] (5) Conduct the above tests using broadband signals to obtain the frequency response characteristics of the transmit link and the receive link of the SAR system under broadband signals;

[0051] (6) Refer to the broadband frequency response characteristics, fit each narrowband characteristic, and obtain the hyper-spectrum characteristics of the transmit link and the receive link.

[0052] The advantages of the present invention are as follows:

[0053] (1) The present invention conducts tests based on the original calibrator of the SAR system. The test method, test process, and test data processing are all integrated into the original calibration test of the SAR system. Therefore, no additional test equipment or test software is required. Compared with traditional ground instrumentation tests, it has the advantages of simple method and high operability.

[0054] (2) The present invention conducts tests based on the original calibrator of the SAR system. Due to the characteristics of the SAR system itself, SAR system calibration is an important function of the SAR system itself. Therefore, the accuracy of the SAR calibrator is relatively high, and its own accuracy guarantees the test accuracy of this method.

[0055] (3) The present invention conducts tests based on narrowband signal calibration fitting. Under the guarantee of the SAR system's own capabilities, broadband signals can be subdivided into multiple narrowband signals for full coverage testing. Moreover, broadband testing itself is an inherent test of the SAR. Narrowband signals are fitted with reference, and their accuracy can be guaranteed.

[0056] (4) The present invention conducts tests based on the original calibrator of the basic SAR system. Therefore, it has the advantage of being applicable in orbit. After the spaceborne SAR system is launched into orbit, traditional test equipment and instruments can no longer test it. However, the calibration of the SAR system can be carried out in orbit. External calibration can achieve absolute calibration, and internal calibration can achieve stability monitoring, both of which can be applied in orbit.

[0057] In summary, the present invention solves the problems of low test efficiency, poor accuracy, and lack of on-orbit use conditions in the hyperspectral characteristic test of the SAR system. Through narrowband calibration testing, the hyperspectral characteristic test of the SAR system is directly integrated into the calibration test of the SAR itself, realizing the sharing of test equipment, test methods, and test software. At the same time, the accuracy of the test is ensured through hardware equipment and reference fitting, and it has the advantage of being applicable on orbit. The present invention is not limited to the hyperspectral test of the SAR system and has a reference and guiding role in the frequency response characteristic test of other payloads.

[0058] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification. The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting, characterized in that: The method comprises: Step S1, configuring a SAR system; the SAR system includes a transmitting link and a receiving link; Step S2: transmitting a signal into space through a transmitting link, the signal is captured by a receiving link after being reflected by a ground object, and a hyperspectral characteristic model is constructed based on the transmitting signal and the receiving signal; Step S3: Based on the calibration link of the SAR system, a hyperspectral characteristic test is performed using a hyperspectral characteristic model; the calibration link includes a transmitting calibration link, a receiving calibration link, and a reference calibration link.

2. The method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting according to claim 1, characterized in that: In step S1, the configured transmission link of the SAR system includes a signal generator, a transmitter, a power splitter, a duplexer, and an antenna; the configured reception link of the SAR system includes an antenna, a duplexer, a power splitter, a receiver, and an AD acquisition module.

3. The method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting according to claim 2, characterized in that: In step S2, the SAR system is in working state, the signal generator generates a signal waveform, which is transmitted into space after being modulated by the transmitting link, and the signal returns to the SAR system after being reflected by the ground object, and forms a digital signal after being amplified and collected by the receiving link, and forms a SAR image after being processed to obtain ground object information, so as to establish a hyperspectral characteristic model of the SAR system, which is used to test the frequency response characteristics of the transmitting link and the receiving link of the SAR system.

4. The method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting according to claim 3, characterized in that: The transmission calibration link refers to the signal passing through the transmission link to the antenna front end and the coupled signal flowing back to the receiver through the internal calibrator. The transmission calibration is used to test the hyper-spectral characteristics of the SAR system transmission link + internal calibrator; the reception calibration link refers to the signal passing through the internal calibrator to the antenna front end coupling port and flowing back to the receiver by the reception link. The reception calibration is used to test the hyper-spectral characteristics of the SAR system reception link + internal calibrator; the reference calibration link refers to the signal directly returning to the receiver through the internal calibrator. The reference calibration is used to test the hyper-spectral characteristics of the SAR system internal calibrator.

5. The method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting according to claim 4, characterized in that: In step S3, performing a hyperspectral characteristic test based on a calibration link of the SAR system specifically includes: Segment the bandwidth of the SAR system; Control the calibration parameters of the SAR system, and perform transmission calibration test, reception calibration test, and reference calibration test on the first segment narrowband signal; Extracting frequency response characteristics from the test results, wherein the frequency response characteristics of the transmitting link are equal to the difference between the transmitting calibration signal characteristics and the reference calibration signal characteristics, and the frequency response characteristics of the receiving link are equal to the difference between the receiving calibration signal characteristics and the reference calibration signal characteristics; Repeat the above test to test the narrowband signals from the 2nd segment to the nth segment respectively, and obtain the frequency response characteristics of the transmitting link and the receiving link under each narrowband signal; The above test is performed using a broadband signal to obtain the frequency response characteristics of the SAR system transmission link and receiving link under the broadband signal; With reference to the broadband frequency response characteristics, each narrowband characteristic is fitted to obtain the hyperspectral characteristics of the transmitting link and the receiving link.

6. A SAR system hyperspectral characteristics testing device based on narrowband calibration fitting, characterized in that: The apparatus comprises a processing unit configured to perform: Configure a SAR system; the SAR system includes a transmitting link and a receiving link; The signal is transmitted into space through the transmission link, and the signal is captured by the receiving link after being reflected by the ground object. A hyperspectral characteristic model is constructed based on the transmission signal and the reception signal. Based on the calibration link of the SAR system, a hyperspectral characteristic test is performed using a hyperspectral characteristic model; the calibration link includes a transmitting calibration link, a receiving calibration link, and a reference calibration link.

7. The SAR system hyperspectral characteristics testing device based on narrowband calibration and fitting according to claim 6, characterized in that: The transmitting link of the SAR system includes a signal generator, a transmitter, a power splitter, a duplexer, and an antenna; the receiving link of the SAR system includes an antenna, a duplexer, a power splitter, a receiver, and an AD acquisition module.

8. The SAR system hyperspectral characteristic testing device based on narrowband calibration and fitting according to claim 7, characterized in that: When the SAR system is in working state, the signal generator generates a signal waveform, which is modulated by the transmitting link and transmitted into space. The signal is reflected by the ground object and returns to the SAR system. It is amplified and collected by the receiving link to form a digital signal. After processing, it forms a SAR image to obtain ground object information, so as to establish a hyperspectral characteristic model of the SAR system. This model is used to test the frequency response characteristics of the transmitting link and receiving link of the SAR system.

9. The SAR system hyperspectral characteristic testing device based on narrowband calibration and fitting according to claim 8, characterized in that: The transmission calibration link refers to the signal passing through the transmission link to the antenna front end and the coupled signal flowing back to the receiver through the internal calibrator. The transmission calibration is used to test the hyper-spectral characteristics of the SAR system transmission link + internal calibrator; the reception calibration link refers to the signal passing through the internal calibrator to the antenna front end coupling port and flowing back to the receiver by the reception link. The reception calibration is used to test the hyper-spectral characteristics of the SAR system reception link + internal calibrator; the reference calibration link refers to the signal directly returning to the receiver through the internal calibrator. The reference calibration is used to test the hyper-spectral characteristics of the SAR system internal calibrator.

10. The method for testing the hyperspectral characteristics of a SAR system based on narrowband calibration and fitting according to claim 9, characterized in that: The hyperspectral characteristic test based on the calibration link of the SAR system includes: Segment the bandwidth of the SAR system; Control the calibration parameters of the SAR system, and perform transmission calibration test, reception calibration test, and reference calibration test on the first segment narrowband signal; Extracting frequency response characteristics from the test results, wherein the frequency response characteristics of the transmitting link are equal to the difference between the transmitting calibration signal characteristics and the reference calibration signal characteristics, and the frequency response characteristics of the receiving link are equal to the difference between the receiving calibration signal characteristics and the reference calibration signal characteristics; Repeat the above test to test the narrowband signals from the 2nd segment to the nth segment respectively, and obtain the frequency response characteristics of the transmitting link and the receiving link under each narrowband signal; The above test is performed using a broadband signal to obtain the frequency response characteristics of the SAR system transmission link and receiving link under the broadband signal; With reference to the broadband frequency response characteristics, each narrowband characteristic is fitted to obtain the hyperspectral characteristics of the transmitting link and the receiving link.

Images