Multi-channel error correction method and related device for spaceborne SAR system

Abstract

The present application provides a multi-channel error correction method and related device for a satellite-borne SAR system, including: according to the transit time and relative position of the SAR satellite when passing through the external calibration field, controlling the active calibrator deployed on the ground to continuously send LFM pulse signals to the passing SAR satellite; the SAR satellite is configured in a multi-channel receiving mode, and the multi-channel simultaneously receives the LFM pulse signal, and transmits the multi-channel echo data to the ground, performs range pulse compression processing on the echo data to obtain the Doppler center time point, and extracts the echo data of each channel near the Doppler center time point; performs multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient; performs multi-channel error correction according to the multi-channel compensation coefficient, and verifies the correction result. The present application can accurately correct the multi-channel consistency error according to the multi-channel compensation coefficient.

Description

Technical Field

[0001] The present application belongs to the technical field of spaceborne SAR systems, and in particular, relates to a multi-channel error correction method and related devices for spaceborne SAR systems. Background Art

[0002] With the development of spaceborne SAR technology, multi-channel SAR has become a hot topic in current research. Azimuth multi-channel SAR can achieve high-resolution wide-band imaging, that is, it can significantly increase the imaging width while maintaining high resolution. Range multi-channel SAR can achieve range digital multi-beam forming, provide greater gain and more flexible beam pointing, and broaden the range of beam position selection.

[0003] However, multi-channel SAR inevitably introduces inter-channel errors. The inter-channel errors of multi-channel spaceborne SAR refer to the inconsistency of the amplitude and phase characteristics of each receiving channel in the multi-channel SAR system due to the inconsistency of the characteristics of each channel hardware (such as amplifiers, filters, frequency converters, analog-to-digital converters, etc.), resulting in the amplitude and phase errors of the received echo signals, which affects the reconstruction of multi-channel SAR signals and the synthesis of DBF, resulting in imaging distortion and performance degradation. Therefore, multi-channel error correction is an unavoidable problem in the development of multi-channel SAR systems.

[0004] The existing multi-channel error correction methods for spaceborne SAR can be mainly divided into the method of using the internal calibration network for calibration and the method of estimating the phase difference through multi-channel echo data. Both methods have their limitations. The internal calibration network cannot guarantee that the internal calibration link is completely consistent with the echo receiving link and cannot cover all receiving links, which will inevitably introduce measurement errors. The algorithm for phase estimation using multi-channel echo data on the ground is relatively complex and has certain requirements for echo data. Summary of the invention

[0005] In view of this, the present application aims to propose a multi-channel error correction method and related devices for a spaceborne SAR system to solve the deficiencies of the above problems.

[0006] To achieve the above purpose, the technical solution of this application is implemented as follows:

[0007] In a first aspect, the present application provides a multi-channel error correction method for a spaceborne SAR system, comprising:

[0008] According to the transit time and relative position of the SAR satellite when passing through the calibration field, the active calibrator deployed on the ground is controlled to continuously send LFM pulse signals to the passing SAR satellite;

[0009] The SAR satellite is configured in a multi-channel receiving mode, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point;

[0010] Performing multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient;

[0011] Multi-channel error correction is performed according to the multi-channel compensation coefficients, and the correction result is verified.

[0012] In the second aspect, based on the same inventive concept, the present application also provides a multi-channel error correction device for a spaceborne SAR system, comprising:

[0013] The signal sending module is configured to control the active calibrator arranged on the ground to continuously send the LFM pulse signal to the passing SAR satellite according to the passing time and relative position of the SAR satellite when passing the outer calibration field;

[0014] The signal receiving module is configured to configure the SAR satellite to a multi-channel receiving mode, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point;

[0015] A data processing module is configured to perform multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient;

[0016] The error correction module is configured to perform multi-channel error correction according to the multi-channel compensation coefficients and verify the correction result.

[0017] In a third aspect, based on the same inventive concept, the present application also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in the first aspect is implemented.

[0018] In a fourth aspect, based on the same inventive concept, the present application also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the method described in the first aspect.

[0019] Compared with the prior art, the multi-channel error correction method and related device of the spaceborne SAR system described in this application have the following beneficial effects:

[0020] The multi-channel error correction method and related devices of the spaceborne SAR system described in the present application perform multi-channel data processing on the echo data through an error compensation algorithm to obtain a multi-channel compensation coefficient, and can accurately correct the multi-channel consistency error according to the multi-channel compensation coefficient, thereby laying a hardware foundation for the development of new system SAR, especially DBF-SAR, high-resolution wide-band SAR, etc., improving the multi-channel consistency index, and further improving the final SAR imaging quality and target detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 This is a flow chart of the multi-channel error correction method for a spaceborne SAR system described in an embodiment of the present application;

[0023] Figure 2 A schematic diagram of the real part of data in a pulse of three-channel raw data according to an embodiment of the present application;

[0024] Figure 3 This is a schematic diagram of the channel phase error described in an embodiment of the present application;

[0025] Figure 4 This is a schematic diagram of the three-channel error correction result described in the embodiment of the present application;

[0026] Figure 5 A schematic diagram showing the comparison between the single-channel pulse pressure and the pulse pressure after DBF described in the embodiment of the present application;

[0027] Figure 6 This is a schematic diagram of the structure of a multi-channel error correction device for a spaceborne SAR system according to an embodiment of the present application;

[0028] Figure 7 This is a schematic diagram of the structure of the active calibrator described in the embodiment of the present application;

[0029] Figure 8 This is a schematic diagram of the pulse signal described in the embodiment of the present application;

[0030] Fig. 9 This is a schematic diagram of the hardware structure of the electronic device described in the embodiment of the present application. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0032] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0034] See also Figure 1 As shown, this embodiment provides a multi-channel error correction method for a spaceborne SAR system, comprising:

[0035] Step S101, according to the transit time and relative position of the SAR satellite when it passes through the outer calibration field, control the active calibrator deployed on the ground to continuously send LFM pulse signals to the passing SAR satellite.

[0036] Specifically, in this embodiment, a controllable active calibrator that actively transmits signals is used. The active calibrator uses a direct wave method. When a SAR satellite passes through an outer calibration field, the active calibrator adjusts the antenna angle according to the satellite transit time and relative position, and continuously sends LFM pulse signals to the SAR satellite.

[0037] Step S102, the SAR satellite is configured in a multi-channel receiving mode, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point.

[0038] Specifically, in this embodiment, the SAR satellite in this embodiment only receives signals but does not radiate signals, and turns on the multi-channel receiving mode. In this way, when passing through the external calibration field, it does not radiate signals to the ground, which can effectively eliminate the interference of ground objects and obtain pure point target signals.

[0039] When the SAR satellite passes the ground station, it transmits echo data, obtains the received multi-channel echo data through the ground data transmission station, performs range pulse compression processing on the received echo data, extracts the pulse data with the largest peak value according to the change of each pulse peak point, and uses it as the Doppler center time point to extract the echo data of each channel near the Doppler center time point. It should be noted that the range pulse compression processing method is a conventional technology well known to those skilled in the art, and this embodiment does not improve it, so it will not be further described here.

[0040] Step S103: performing multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient.

[0041] Specifically, in this embodiment, after the ground station acquires the data, it performs error correction according to the following error compensation algorithm:

[0042] First, obtain multi-channel echo data with errors for:

[0043] (1)

[0044] Where k is the channel number; is the amplitude error coefficient of each channel; A is the amplitude; is the linear frequency modulation slope; The echo delay of each channel; is the phase of each channel; t is the time.

[0045] It is relatively easy to obtain. It can be obtained by taking the peak point after pulse compression. The following content is mainly for and The method of obtaining .

[0046] Expanding the exponential term of formula (1) yields:

[0047] (2)

[0048] Standard LFM signal for:

[0049] (3)

[0050] Using equation (3) to de-skew equation (2), we can get:

[0051] (4)

[0052] in, for The conjugate of . Finding the phase of equation (4), we can get its exponential term :

[0053] (5)

[0054] Taking the first-order derivative of formula (5) with respect to t, we can obtain:

[0055] (6)

[0056] Then the delay parameter of the channel can be obtained :

[0057] (7)

[0058] Generate the reference signal using the delay parameter obtained by equation (7) :

[0059] (8)

[0060] Using equation (8) to de-skew equation (1), we can obtain:

[0061] (9)

[0062] The phase error parameter for:

[0063] (10)

[0064] The relative difference of each channel delay can be aligned by FPGA with the sampling clock cycle. The amplitude and phase compensation uses the phase error calculation compensation coefficient of formula (9). The amplitude can be compensated with any channel as the reference, and the phase is compensated with 0° as the reference. Then the compensation coefficient is The calculation formula is:

[0065] (11)

[0066] Step S104: perform multi-channel error correction according to the multi-channel compensation coefficients, and verify the correction result.

[0067] Specifically, in this embodiment, equation (11) is multiplied by equation (1) to complete multi-channel error correction:

[0068] (12).

[0069] The error correction method described in this embodiment can accurately calculate the delay and amplitude-phase compensation coefficients of each channel. After the compensation coefficients are added, the SAR satellite can realize the error correction between channels on orbit; compared with the correction method using the internal calibration link, the present application directly uses the final receiving link, and the calibration error is the error of the real link, and no additional measurement error will be introduced due to the difference in the link; compared with estimating the channel error using the echo data of the surface target on the ground, the present application uses the pure point target signal of the active calibrator, shielding the interference generated by the surrounding objects, and the calculation of the phase error of each channel is simple and efficient, the result is accurate, and it is easy to implement.

[0070] The following is the processing result of a three-channel test data according to the above formula:

[0071] Step 1 Figure 2 is the real part of a pulse of the original data of the three channels. The data near the stationary point is enlarged, and it can be seen that there are obvious amplitude and phase errors in the three channels.

[0072] Step 2: According to formula (3) to formula (6), the phase is taken out and derived after being correlated with the standard LFM signal. Then, according to formula (7), the delay of each channel is calculated as:

[0073] a. Channel 1 delay : 4.289081us;

[0074] b. Channel 2 delay : 4.289063us;

[0075] c. Channel 3 delay :4.289169us.

[0076] Step 3: Substitute the delay of each channel into equation (8) to generate a reference signal. Correlate it with the original data to get equation (9). Take the phase error of each channel and plot it as follows: Figure 3 shown.

[0077] It can be seen from the above figure that the phase error change trend of each channel is consistent, so the phase at the middle point can be taken to represent the phase error of the channel, and the phase error of each channel is:

[0078] a. Channel 1 phase error : 39.639577°;

[0079] b. Channel 2 phase error : 56.237326°;

[0080] c. Channel 3 phase error :-4.251646°.

[0081] Perform pulse compression on the original data of each channel and take the amplitude of its peak point to represent the amplitude of the channel. The amplitude calculation results of each channel are:

[0082] a. Channel 1 amplitude :1989879;

[0083] b. Channel 2 amplitude :1840086;

[0084] c. Channel 3 amplitude :1862467.

[0085] In summary, the amplitude is compensated based on the 2 channels, and the phase is compensated based on 0°. Then the compensation coefficients of each channel in equation (11) are:

[0086] a. Channel 1 compensation coefficient : ;

[0087] b. Channel 2 compensation coefficient : ;

[0088] c. Channel 3 compensation coefficient : .

[0089] According to formula (12), the compensation coefficient is multiplied by the original data, and the compensation results of each channel are as follows: Figure 4 As shown, it can be seen that the waveforms near the stagnation point almost overlap after error correction.

[0090] Verification of multi-channel error correction effect: DBF operation is performed on the compensated 3-channel data, and the normal beam is selected. The weight of each channel is 1, that is, the 3 channels are directly summed, and pulse compression is performed after summing. Compare it with the single-channel pulse compression result. Figure 5 And as shown in Table 1.

[0091] Table 1 Comparison of indicators before and after DBF

[0092] Indicator comparison Peak amplitude Resolution PSLR ISLR Single channel pulse pressure index 123.26dB 0.3677m -13.29dB -14.90dB Pulse pressure index after DBF 132.89dB 0.3706m -13.27dB -14.90dB

[0093] As shown in Table 1, after DBF processing, the pulse pressure peak value becomes 3 times, and the resolution, PSLR, and ISLR indicators have almost no obvious deterioration, indicating that the method proposed in this patent can accurately correct the multi-channel consistency error.

[0094] It should be noted that the above describes some embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0095] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, an embodiment of the present application further provides a multi-channel error correction device for a space-borne SAR system.

[0096] like Figure 6 As shown, the multi-channel error correction device of the spaceborne SAR system comprises:

[0097] The signal sending module 11 is configured to control the active calibrator arranged on the ground to continuously send the LFM pulse signal to the passing SAR satellite according to the passing time and relative position of the SAR satellite when passing the outer calibration field;

[0098] The signal receiving module 12 is configured as a multi-channel receiving mode of the SAR satellite, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point;

[0099] The data processing module 13 is configured to perform multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient;

[0100] The error correction module 14 is configured to perform multi-channel error correction according to the multi-channel compensation coefficients and verify the correction result.

[0101] In some embodiments, the signal sending module 11 includes:

[0102] An active calibrator is arranged in the external calibration field, and the active calibrator includes a host computer, a radar transmitter and a servo system;

[0103] The host computer is equipped with a 10G optical fiber network port and two serial ports. The 10G optical fiber network port is used to receive multi-channel echo data transmitted by the data transmission system. One serial port is connected to the radar transmitter for sending RF parameters. The other serial port is connected to the servo system for sending the radar beam pointing angle.

[0104] The radar transmitter consists of a digital module, an intermediate frequency module, an RF module, and a frequency synthesis module. The digital module generates an LFM pulse digital signal according to the parameters configured by the host computer. The intermediate frequency module is used to convert the digital signal into an intermediate frequency analog signal, and filter and amplify it. The RF module is used to mix the intermediate frequency signal into the RF signal, and filter and amplify it, and output the signal to the radar antenna of the servo system. The frequency synthesis module is used to generate multi-channel stable phase clocks and provide them to the RF module and the intermediate frequency module.

[0105] The servo system consists of a pointing control module, an attitude measurement module, an equatorial mount turntable, and a radar antenna. The pointing control module receives the pointing parameters of the host computer and controls the turntable to point to the satellite transit area in advance; the attitude measurement module is used to measure the pointing of the turntable and feed back the real-time position to the pointing control module; the equatorial mount turntable drives the motor according to the signal of the pointing control module to realize the two-dimensional rotation of the turntable; the radar antenna feed receives the radio frequency signal of the radar transmitter to radiate electromagnetic waves, and beams the electromagnetic waves, and transmits the LFM pulse signal formed by the beaming to the SAR satellite.

[0106] Specifically, in this embodiment, Figure 7 As shown, the data transmission system uses the X-band ground station of the SAR satellite. After the ground station obtains the multi-channel echo data packet, it transmits it to the host computer through the optical fiber network;

[0107] The host computer consists of an industrial computer, a data processing module, and command and control software. The industrial computer is equipped with a 20TB large-capacity hard disk, a 10G optical fiber network port, and two serial ports. The large-capacity hard disk is used to store echo data; the optical fiber port is used to receive echo data from the data transmission system; serial port 1 is used to communicate with the radar transmitter to send parameters such as RCS, frequency band, pulse width, etc.; serial port 2 is used to communicate with the servo system to send parameters such as six track numbers and UTC time; the data processing module is used to input parameters and process and analyze data;

[0108] The radar transmitter consists of a digital module, an intermediate frequency module, a radio frequency module, and a frequency synthesis module. The digital module generates an LFM pulse digital signal according to the parameters configured by the host computer; the intermediate frequency module is used to convert the digital signal into an intermediate frequency analog signal, and filter and amplify it; the radio frequency module is used to mix the intermediate frequency signal into the radio frequency signal, and filter and amplify it, and output the signal to the radar antenna of the servo system; the frequency synthesis module is used to generate multiple high-quality stable phase clocks and provide them to the radio frequency module and the intermediate frequency module.

[0109] The servo system consists of a pointing control module, an attitude measurement module, an equatorial mount turntable, and a radar antenna. The pointing control module receives the pointing parameters of the host computer and controls the turntable to point to the satellite transit area in advance; the attitude measurement module is used to measure the turntable pointing and feed back the real-time position to the pointing control module to form a closed-loop control; the equatorial mount turntable consists of a fixed base and a two-dimensional mechanical rotation structure of a motor. The motor is driven according to the signal of the pointing control module to realize the two-dimensional rotation of the turntable; the radar antenna consists of a high-power feed source and a reflective surface. The feed source receives the radio frequency signal of the radar transmitter to radiate electromagnetic waves, and the reflective surface focuses the electromagnetic waves and transmits them to the SAR satellite.

[0110] In some embodiments, it further comprises:

[0111] The orbit information of the SAR satellite is input into the host computer. The host computer calculates the radar beam pointing angle according to the satellite orbit information, converts it into a two-dimensional angle in the equatorial coordinate system and sends it to the servo system. The servo system controls the equatorial mount turntable to aim at the SAR satellite according to the control angle command and its own angle measurement value.

[0112] The radar parameters of the SAR payload (SAR payload is part of the SAR satellite and is the main payload of the SAR satellite) are input on the host computer and sent to the radar transmitter. The radar transmitter calculates the transmission interval and generates the transmission waveform. The active calibrator automatically transmits the LFM pulse signal when the satellite passes by.

[0113] It should be noted that the radar transmitter calculates the transmission interval based on the PRT, pulse width, sampling window time and other parameters of the SAR payload to ensure that at least one pulse signal can be fully collected within the sampling window (the SAR payload sampling window time is required to be greater than 2.5 times the pulse width). The timing is as follows Figure 8 shown.

[0114] For the convenience of description, the above devices are described in terms of functions and are divided into various modules. Of course, when implementing the embodiments of the present application, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0115] The device of the above embodiment is used to implement the corresponding method in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be described in detail here.

[0116] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments and methods, an embodiment of the present application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in any of the above embodiments is implemented.

[0117] Fig. 9A more specific schematic diagram of the hardware structure of an electronic device provided in this embodiment is shown, and the device may include: a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, the memory 1020, the input / output interface 1030, and the communication interface 1040 are connected to each other through the bus 1050 in the device.

[0118] The processor 1010 can be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0119] The memory 1020 may be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 may store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program codes are stored in the memory 1020 and are called and executed by the processor 1010.

[0120] The input / output interface 1030 is used to connect the input / output module to realize information input and output. The input / output module can be configured in the device as a component (not shown in the figure), or it can be externally connected to the device to provide corresponding functions. The input device may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output device may include a display, a speaker, a vibrator, an indicator light, etc.

[0121] The communication interface 1040 is used to connect a communication module (not shown) to realize communication interaction between the device and other devices. The communication module can realize communication through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.).

[0122] The bus 1050 includes a path that transmits information between the various components of the device (eg, the processor 1010 , the memory 1020 , the input / output interface 1030 , and the communication interface 1040 ).

[0123] It should be noted that, although the above device only shows the processor 1010, the memory 1020, the input / output interface 1030, the communication interface 1040 and the bus 1050, in the specific implementation process, the device may also include other components necessary for normal operation. In addition, it can be understood by those skilled in the art that the above device may also only include the components necessary for implementing the embodiments of the present specification, and does not necessarily include all the components shown in the figure.

[0124] The electronic device of the above embodiment is used to implement the corresponding method in any of the above embodiments, and has the beneficial effects of the corresponding method embodiment, which will not be described in detail here.

[0125] Based on the same inventive concept, corresponding to any of the above-mentioned embodiments, the present application also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the method described in any of the above embodiments.

[0126] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device.

[0127] The computer instructions stored in the storage medium of the above embodiments are used to enable the computer to execute the method described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0128] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0129] In addition, to simplify the description and discussion, and in order not to make the embodiments of the present application difficult to understand, the known power / ground connections to the integrated circuit (IC) chip and other components may or may not be shown in the provided drawings. In addition, the device may be shown in the form of a block diagram to avoid making the embodiments of the present application difficult to understand, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the embodiments of the present application are to be implemented (that is, these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details or with changes in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0130] Although the present application has been described in conjunction with specific embodiments of the present application, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may use the discussed embodiments.

[0131] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A multi-channel error correction method for a spaceborne SAR system, characterized in that: include: According to the transit time and relative position of the SAR satellite when passing through the calibration field, the active calibrator deployed on the ground is controlled to continuously send LFM pulse signals to the passing SAR satellite; The SAR satellite is configured in a multi-channel receiving mode, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point; Performing multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient; Multi-channel error correction is performed according to the multi-channel compensation coefficients, and the correction result is verified.

2. The method according to claim 1, characterized in that The multi-channel echo data is transmitted to the ground, and the echo data is subjected to range pulse compression processing to obtain the Doppler center time point, and the echo data of each channel near the Doppler center time point is extracted, including: When the SAR satellite passes by the ground station, it transmits echo data downlink, and the ground station obtains the received multi-channel echo data; The received multi-channel echo data is subjected to range pulse compression processing, and the pulse data with the largest peak value is extracted according to the change of each pulse peak point as the Doppler center time point, and the echo data of each channel near the Doppler center time point is extracted.

3. The method according to claim 1, characterized in that The performing multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient includes: Multi-channel echo data with errors E k for: Formula E k Expand the exponential term of , and we get: The standard LFM signal E0 is: The LFM signal formula is used to de-skew the echo data after the exponential expansion. The formula is as follows: Formula E lk To find the phase, we get the exponential term formula: According to the exponential formula Φ, the first-order derivative of t is obtained to obtain the delay parameter τ of the channel. k : Generate a reference signal E according to the delay parameter formula I , as follows: By formula E I For Formula E k Doing the de-skewing operation, we get: The phase error parameter for: The relative difference of each channel delay can be aligned by FPGA with the sampling clock cycle, and the amplitude and phase compensation is calculated by formula E pk The compensation coefficient of the phase error is calculated. The amplitude is compensated based on any channel, and the phase is compensated based on 0°. The compensation coefficient c k The calculation formula is: Where k is the channel number; α is the amplitude error coefficient of each channel; A is the amplitude; K r is the linear frequency modulation slope; τ represents the echo delay of each channel; represents the phase of each channel, j is an imaginary number, t is time, is the conjugate of E0.

4. The method according to claim 3, characterized in that The compensation factor c k With echo data E k Perform point multiplication to obtain multi-channel error correction: AND ck =And k ·c k 。 5. A multi-channel error correction device for a spaceborne SAR system, characterized in that: include: The signal sending module is configured to control the active calibrator arranged on the ground to continuously send the LFM pulse signal to the passing SAR satellite according to the passing time and relative position of the SAR satellite when passing the outer calibration field; The signal receiving module is configured to configure the SAR satellite to a multi-channel receiving mode, and the multi-channels simultaneously receive the LFM pulse signal, and transmit the multi-channel echo data to the ground, perform range pulse compression processing on the echo data to obtain the Doppler center time point, and extract the echo data of each channel near the Doppler center time point; A data processing module is configured to perform multi-channel data processing on the echo data based on a preset error compensation algorithm to obtain a multi-channel compensation coefficient; The error correction module is configured to perform multi-channel error correction according to the multi-channel compensation coefficients and verify the correction result.

6. The device according to claim 5, characterized in that The signal sending module comprises: An active calibrator is arranged in the external calibration field, and the active calibrator includes a host computer, a radar transmitter and a servo system; The host computer is configured with a 10G optical fiber network port and two serial ports, wherein the 10G optical fiber network port is used to receive multi-channel echo data transmitted by the data transmission system, one serial port is connected to the radar transmitter for sending radio frequency parameters, and the other serial port is connected to the servo system for sending the radar beam pointing angle; The radar transmitter is composed of a digital module, an intermediate frequency module, a radio frequency module, and a frequency synthesis module. The digital module generates an LFM pulse digital signal according to the parameters configured by the host computer. The intermediate frequency module is used to convert the digital signal into an intermediate frequency analog signal, and filter and amplify it. The radio frequency module is used to mix the intermediate frequency signal into a radio frequency signal, and filter and amplify it, and output the signal to the radar antenna of the servo system; the frequency synthesis module is used to generate a multi-channel stable phase clock and provide it to the radio frequency module and the intermediate frequency module; The servo system consists of a pointing control module, an attitude measurement module, an equatorial mount turntable, and a radar antenna. The pointing control module receives the pointing parameters of the host computer and controls the turntable to point to the satellite transit area in advance; the attitude measurement module is used to measure the pointing of the turntable and feed back the real-time position to the pointing control module; the equatorial mount turntable drives the motor according to the signal of the pointing control module to realize the two-dimensional rotation of the turntable; the radar antenna feed receives the radio frequency signal of the radar transmitter to radiate electromagnetic waves, and beams the electromagnetic waves, and transmits the LFM pulse signal formed by the beaming to the SAR satellite.

7. The device according to claim 6, characterized in that Also includes: The orbit information of the SAR satellite is inputted into the host computer, and the host computer calculates the radar beam pointing angle according to the orbit information of the satellite, and converts it into a two-dimensional angle in the equatorial coordinate system and sends it to the servo system, and the servo system controls the equatorial mount turntable to aim at the SAR satellite according to the control angle instruction and its own angle measurement value; The radar parameters of the SAR payload are inputted into the host computer and sent to the radar transmitter. The radar transmitter calculates the transmission interval and generates the transmission waveform. The active calibrator automatically transmits the LFM pulse signal when the satellite passes by.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 4 is implemented.

9. A non-transitory computer-readable storage medium, characterized in that: in, The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions are used to cause a computer to execute the method according to any one of claims 1 to 4.

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