Multi-source GNSS-R / S integrated imaging method, electronic equipment and storage medium

Abstract

The invention relates to a multi-source GNSS-R / S integrated imaging method, which comprises the following steps of: acquiring a GNSS signal reflected by a target area according to a geometrical relationship among the target area, a GNSS satellite and a radar receiver; the GNSS signals comprise m GNSS-R signals and n GNSS-S signals, the GNSS-R signals are signals which are received by a radar receiver and are reflected by a mirror surface of a target area after being emitted by a GNSS satellite, and the GNSS-S signals are signals which are received by the radar receiver and are backwards scattered by the target area after being emitted by the GNSS satellite; and the radar receiver moves along the target area, receives and processes all GNSS-R signals and GNSS-S signals reflected by the target area at the same time, and forms a target area image by using a synthetic aperture method. According to the invention, integrated imaging is carried out by using the reflected signal and the scattered signal of the target area after the global navigation satellite signal arrives at the ground, and high-quality imaging based on the GNSS signal is realized by combining the characteristics of high power of the GNSS-R reflected signal and multiple dimensions of the GNSS-S signal.

Description

Technical Field

[0001] The present invention relates to the field of radar technology in the electronic information industry, and in particular to a multi-source GNSS-R / S integrated imaging method, electronic equipment and storage medium. Background Art

[0002] The GNSS-R / S receiving system uses the GNSS satellite signals reflected / scattered by ground targets to perform microwave imaging of the ground area, which can obtain multi-dimensional feature information of the ground and realize the detection and identification of ground targets. GNSS signals have the advantages of rich signal sources and all-day and all-weather detection. This technology can complement radar, optical remote sensing and other means to improve the perception of ground targets, and is an important means of ground object detection. In recent years, target detection and identification based on GNSS-R / S signals has become a hot topic in scientific research.

[0003] GNSS-R is the signal reflected by the mirror of the ground target after the navigation satellite is launched. The signal power is strong, but the imaging geometry is poor. Due to the limitation of the mirror reflection geometry, the number of GNSS-R signals that can be observed in the same area is small (≤4). GNSS-S signal is the scattered signal of GNSS signal by the ground target. The number of signals is large and the imaging geometry is good, but the scattered signal power is very weak. If the advantages of both GNSS-R and GNSS-S signals are fully combined to image the target area, it will be of great significance for the detection and feature recognition of ground targets.

[0004] Synthetic aperture radar (SAR) technology is an effective means to achieve microwave detection and imaging in the radar field. However, GNSS signals are mainly used for navigation and positioning and are not designed for radar detection. When used for detection and imaging, they face problems such as low signal power, narrow signal bandwidth, and poor imaging resolution. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a multi-source GNSS-R / S integrated imaging method, electronic device and storage medium, which have the characteristics of high reliability, high stability and high precision.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a multi-source GNSS-R / S integrated imaging method, comprising the following steps:

[0007] Step S1, according to the geometric relationship between the target area, the GNSS satellite and the radar receiver, obtaining the GNSS signal reflected by the target area; the GNSS signal includes m GNSS-R signals and n GNSS-S signals, the GNSS-R signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and reflected by the mirror surface of the target area, and the GNSS-S signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and backscattered by the target area;

[0008] Step S2: The radar receiver moves along the target area, simultaneously receives and processes all GNSS-R signals and GNSS-S signals reflected by the target area, and forms an image of the target area using a synthetic aperture method.

[0009] According to a technical solution of the present invention, in the step S2, it specifically includes:

[0010] Step S21, performing two-dimensional demodulation on the GNSS-R signal and the GNSS-S signal to obtain a three-dimensional echo signal of "fast time-slow time-Doppler frequency" with the carrier frequency and code phase of the direct signal as the origin;

[0011] Step S22, obtaining the signal delay and Doppler frequency of the target area;

[0012] Step S23, performing two-dimensional back-projection on the three-dimensional echo signal, searching for a signal energy value from the three-dimensional echo signal according to the signal delay and Doppler frequency of each grid point of the target area, and projecting the signal energy value to the corresponding grid point of the target area to form a single-star image of the target area;

[0013] Step S24, executing steps S21 to S23 for all visible GNSS satellites to obtain a single-star image of the target area corresponding to each GNSS satellite, and fusing the obtained multiple single-star images according to grid points.

[0014] According to a technical solution of the present invention, in the step S21, two-dimensional demodulation is performed on the GNSS-R signal and the GNSS-S signal, specifically including:

[0015] Step S211: for any of the GNSS-R signals or the GNSS-S signals, the code phase C of the corresponding direct signal is taken as the starting point, and a PRN code period T is set. code As a unit, intercept a section of signal;

[0016] Step S212: The intercepted signal is subjected to the carrier frequency f of the corresponding direct signal. c is the center frequency, within ±f MCarrier demodulation is performed at intervals of Δf within the frequency range of M The value of the interval Δf is determined according to the radial velocity of the relative motion between the target area being measured and the radar receiver;

[0017] Step S213: Perform PRN code correlation on the demodulated signal to obtain a frequency range of -f M :+f M 、Time range is 0~T code The "time-frequency" two-dimensional signal;

[0018] Step S214: When the radar receiver moves along the target area, steps S211 to S213 are sequentially executed for each segment of GNSS-R signal or GNSS-S signal received sequentially to obtain multiple segments of "time-frequency" two-dimensional signals, and the time in each segment of the "time-frequency" two-dimensional signal is defined as fast time τ, and the time of movement of the radar receiver is defined as slow time t, to form the three-dimensional echo signal of "fast time-slow time-Doppler frequency", and the three-dimensional echo signal is in the form of a complex number.

[0019] According to a technical solution of the present invention, in the step S22, it specifically includes:

[0020] Step S221: Calculate the position and velocity of the GNSS satellite corresponding to the direct signal according to the direct signal, and record the position of the i-th GNSS satellite as The speed of the i-th GNSS satellite is

[0021] Step S222: Calculate the position of the radar receiver corresponding to the direct signal according to the direct signal: x ,R y ,R z ), the speed of the radar receiver corresponding to the direct signal is (V x ,V y ,V z );

[0022] Step S223: Divide the target area into grids, and record the position coordinates of the kth grid center as

[0023] Step S224: Calculate the signal delay value of the target area based on the geometric relationship and Doppler frequency calculation value Among them, the signal delay calculation value of the kth grid is and Doppler frequency calculation value The calculation formulas are:

[0024]

[0025] in,

[0026]

[0027]

[0028] Where c is the speed of light;

[0029] Step S225: real-time tracking of GNSS-R signals to obtain pseudo-ranges ρ1, ρ2, ..., ρ of reflected signals of m GNSS satellites corresponding to the GNSS-R signals. m , reflected signal pseudorange rate Calculate the delay difference and Doppler deviation of the m GNSS-R signals, and take the average value as the delay correction value Δτ e and Doppler correction Δf d , and its calculation formula is:

[0030]

[0031] Step S226: The delay correction value Δτ calculated in step S225 e and Doppler correction Δf d , the signal delay calculation value and Doppler frequency calculation value of GNSS-R signal and GNSS-S signal are corrected to obtain the final signal delay Δτ and Doppler frequency f d , and its calculation formula is:

[0032]

[0033] According to a technical solution of the present invention, in step S23, performing two-dimensional back projection on the echo signal specifically includes:

[0034] Step S231: According to the signal delay and Doppler frequency of each grid point in the target area, the corresponding echo energy data is searched along the fast time τ and Doppler frequency dimensions from the three-dimensional echo signal of "fast time-slow time-Doppler frequency", and its amplitude A is taken. E , and take the fast time as Δτ and the Doppler frequency f d =0 signal phase θ E , forming the back projection signal s(A E ,θ E );

[0035] Step S232: the back projection signal s(A E ,θ E ) multiplied by the phase compensation factor exp(-j·2π·fcarrier ·Δτ), and then projected to each grid point, where j is the imaginary unit and f carrier is the carrier center frequency of the GNSS signal;

[0036] Step S233: for multiple groups of data of slow time dimension t generated when the radar receiver moves along the target area, a synthetic aperture time T is taken according to the slow time t dimension in the three-dimensional echo signal. SAR seconds of data, T SAR Each set of data within a second is projected onto the grid of the target area in the manner of step S231 to step S232, and complex accumulation is performed to obtain a single star image of the target area.

[0037] According to a technical solution of the present invention, in the step S24, it specifically includes:

[0038] The single-star images of the GNSS satellites corresponding to the m GNSS-R signals and the single-star images of the GNSS satellites corresponding to the n GNSS-S signals are non-coherently accumulated and fused according to the corresponding positions of the grid points of the target area to obtain a final target area image.

[0039] According to one aspect of the present invention, an electronic device is provided, comprising: one or more processors, one or more memories, and one or more computer programs; wherein the processor is connected to the memory, and the one or more computer programs are stored in the memory, and when the electronic device is running, the processor executes the one or more computer programs stored in the memory, so that the electronic device performs a multi-source GNSS-R / S integrated imaging method as described in any one of the above technical solutions.

[0040] According to one aspect of the present invention, a computer-readable storage medium is provided for storing computer instructions. When the computer instructions are executed by a processor, a multi-source GNSS-R / S integrated imaging method as described in any one of the above technical solutions is implemented.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention proposes a multi-source GNSS-R / S integrated imaging method that uses two parameters, time delay and Doppler frequency, to perform two-dimensional back projection, improve the grid resolution of the detection area, and overcome the shortcomings of the narrow bandwidth and low imaging resolution of the GNSS signal; when accurately calculating the echo delay and Doppler frequency of the GNSS-R / S signal, the pseudorange and pseudorange rate of the satellite are obtained by real-time tracking of the strong GNSS-R signal, and the calculated values ​​of the echo delay and Doppler frequency of all GNSS-R / S signals are corrected. At the same time, the present invention makes full use of the signals of all visible satellites, performs non-coherent fusion of the GNSS-R image and the GNSS-S image according to the grid points of the target area, and improves the signal-to-noise ratio of the image.

[0043] The present invention makes full use of the characteristics of navigation satellite signals having both carrier modulation and PRN code modulation, performs two-dimensional back-projection on the target area, and the target area can be divided into finer grids with high imaging resolution; makes full use of the characteristics of strong GNSS-R signal power and multi-dimensional GNSS-S signal, corrects the imaging geometric relationship by tracking the GNSS-R signal, and makes the calculation of the geometric relationship of the back-projection more accurate; utilizes the L-band electromagnetic signals emitted by all GNSS satellites to detect and image the target, improves the imaging signal-to-noise ratio, and can realize target detection and recognition based on GNSS signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 is a flow chart of a multi-source GNSS-R / S signal integrated imaging method in one embodiment of the present invention;

[0046] Figure 2 is a schematic diagram of a multi-source GNSS-R / S signal integrated imaging method in one embodiment of the present invention;

[0047] Figure 3 is a flow chart of a multi-source GNSS-R / S signal integrated imaging method in one embodiment of the present invention;

[0048] Figure 4 is a schematic diagram of a two-dimensional demodulation method for a signal in one embodiment of the present invention;

[0049] Figure 5 is a method for obtaining the signal delay Δτ and Doppler frequency f of the target area in one embodiment of the present invention.d Schematic diagram;

[0050] Figure 6 is the signal delay Δτ and Doppler frequency f of the target area in one embodiment of the present invention d Flowchart of the calculation;

[0051] Figure 7 is a schematic diagram of two-dimensional back projection of an echo signal in one embodiment of the present invention;

[0052] Figure 8 It is a schematic diagram of the multi-satellite image fusion principle in one embodiment of the present invention. DETAILED DESCRIPTION

[0053] The description of the embodiments of this specification should be combined with the corresponding drawings, which should be considered as part of the complete specification. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated for simplification or convenience. Furthermore, the parts of each structure in the drawings will be described separately. It is worth noting that the elements not shown in the drawings or not described in words are in a form known to ordinary technicians in the relevant technical field.

[0054] The description of the embodiments herein and any reference to directions and orientations are only for the convenience of description and are not to be construed as any limitation on the scope of protection of the present invention. The following description of the preferred embodiments may involve combinations of features, which may exist independently or in combination, and the present invention is not particularly limited to the preferred embodiments. The scope of the present invention is defined by the claims.

[0055] like Figure 1 and Figure 2 As shown, a multi-source GNSS-R / S integrated imaging method of the present invention uses a radar receiver to move near the detected target area and uses the Doppler frequency formed by the relative movement of the radar receiver and the target to perform synthetic aperture imaging. The present invention combines the characteristics of strong GNSS-R reflected signal power and multi-dimensional GNSS-S signal, integrates the reflected signal and scattered signal of the target area after the GNSS signal reaches the ground, and fully utilizes all currently visible GNSS satellite signals for regional fusion imaging to improve the signal-to-noise ratio, thereby obtaining high-quality images based on GNSS signals.

[0056] A multi-source GNSS-R / S integrated imaging method of the present invention comprises the following steps:

[0057] Step S1, according to the geometric relationship between the target area, the GNSS satellite and the radar receiver, the GNSS signal reflected by the target area is obtained; the GNSS signal includes m GNSS-R signals and n GNSS-S signals, the GNSS-R signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and reflected by the mirror surface of the target area, and the GNSS-S signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and backscattered by the target area.

[0058] The GNSS satellite signals reflected by ground targets are divided into GNSS-R signals and GNSS-S signals according to the geometric relationship. The signals that form a mirror reflection with the target area are GNSS-R signals, and other non-mirror reflection signals are GNSS-S signals. GNSS-R signals are mirror reflections with strong signal power but small numbers, while GNSS-S signals are diffuse reflection signals with weak signal power but large numbers and good imaging geometry. Therefore, the electromagnetic signals emitted by all visible GNSS satellites can be fully utilized to perform microwave imaging of the target area.

[0059] Step S2: The radar receiver moves along the target area, simultaneously receives and processes all GNSS-R signals and GNSS-S signals reflected by the target area, and forms an image of the target area using a synthetic aperture method.

[0060] like Figure 3 As shown, the two-dimensional demodulation of the signal in the present invention may include two-dimensional signal demodulation 10, time delay and Doppler frequency calculation 20 of the target area grid points, two-dimensional back projection of the echo signal 30, and multi-satellite image fusion 40.

[0061] Specifically, step S2 includes:

[0062] Step S21, perform two-dimensional demodulation on the GNSS-R signal and the GNSS-S signal to obtain a three-dimensional echo signal of "fast time-slow time-Doppler frequency" with the carrier frequency and code phase of the direct signal as the origin.

[0063] In step S21, two-dimensional demodulation is performed on the GNSS-R signal and the GNSS-S signal, specifically including:

[0064] Step S211: For any GNSS-R signal or GNSS-S signal, the code phase C of the corresponding direct signal is taken as the starting point, and a PRN code period T is set. code As a unit, intercept a section of signal.

[0065] Step S212: The intercepted signal is subjected to the carrier frequency f of the corresponding direct signal. c is the center frequency, within ±f M Carrier demodulation is performed at intervals of Δf within the frequency range ofM The value of the interval Δf is determined according to the radial velocity of the relative motion between the target area being measured and the radar receiver.

[0066] Step S213: Perform PRN code correlation on the demodulated signal to obtain a frequency range of -f M :+f M 、Time range is 0~T code The "time-frequency" two-dimensional signal.

[0067] Step S214: When the radar receiver moves along the target area, steps S211 to S213 are sequentially executed for each segment of GNSS-R signal or GNSS-S signal received sequentially to obtain multiple segments of "time-frequency" two-dimensional signals. The time in each segment of the "time-frequency" two-dimensional signal is defined as fast time τ, and the time of the radar receiver movement is defined as slow time t, to form a three-dimensional echo signal of "fast time-slow time-Doppler frequency", and the three-dimensional echo signal is in the form of a complex number.

[0068] Step S22: Obtain the signal delay and Doppler frequency of the target area.

[0069] like Figures 4 to 6 As shown, Figure 6 is the signal delay Δτ and Doppler frequency f in the target area d Calculation flow chart. The position and velocity of the currently visible satellite and the position and velocity of the radar receiver are calculated based on the direct GNSS signal, and the signal delay and Doppler frequency of each grid point in the target area are calculated. and This is only a geometric value, without considering the influencing factors such as ionospheric delay and tropospheric refraction during signal transmission, and the error is large. Therefore, the time delay correction Δτ of the reflected signal of the m satellites constituting GNSS-R can be obtained by real-time tracking of the GNSS-R strong signal e and Doppler correction Δf d , calculated for all GNSS-R / S signals and Correction is performed to obtain accurate time delay Δτ and Doppler frequency f d .

[0070] In step S22, it specifically includes:

[0071] Step S221: Calculate the position and velocity of the GNSS satellite corresponding to the direct signal according to the direct signal, and record the position of the i-th GNSS satellite as The speed of the i-th GNSS satellite is

[0072] By receiving direct signals transmitted by GNSS satellites, the information in the signals can be used to calculate the position and speed of the satellites, providing the GNSS receiver with the necessary satellite information to achieve high-precision positioning and navigation. This is very important for various civil and professional applications, including traffic management, geographic mapping, environmental monitoring, etc.

[0073] Step S222: Calculate the position of the radar receiver corresponding to the direct signal according to the direct signal (R x ,R y ,R z ), the speed of the radar receiver corresponding to the direct signal is (V x ,V y ,V z ).

[0074] Step S223: Divide the target area into grids, and record the position coordinates of the kth grid center as

[0075] Step S224: Calculate the signal delay value of the target area based on the geometric relationship and Doppler frequency calculation value Among them, the signal delay calculation value of the kth grid is and Doppler frequency calculation value The calculation formulas are:

[0076]

[0077] in,

[0078]

[0079] Where c is the speed of light.

[0080] Through the above calculations, the estimated values ​​of signal delay and Doppler frequency for each grid point in the target area can be obtained, which are very important for further processing and analysis of the signal. For example, in synthetic aperture radar (SAR) imaging or global navigation satellite system reflected signal (GNSS-R) analysis, they can be used to correct the signal and improve the accuracy of imaging or measurement.

[0081] Step S225: real-time tracking of GNSS-R signals to obtain pseudo-ranges ρ1, ρ2, ..., ρ of the reflected signals of m GNSS-R signals corresponding to the GNSS satellites. m , reflected signal pseudorange rate Calculate the delay difference and Doppler deviation of the m GNSS-R signals, and take the average value as the delay correction value Δτ e and Doppler correction Δf d, and its calculation formula is:

[0082]

[0083] Among them, r is the loop variable.

[0084] like Figure 4 As shown in the figure, due to the refraction of the ionosphere and troposphere when the GNSS satellite signal reaches the earth's surface, the signal propagation path is no longer a straight line. It is necessary to correct the time delay and Doppler frequency calculated based on the geometric relationship according to the pseudorange and pseudorange rate measured by the GNSS-R strong signal time.

[0085] Step S226: The delay correction value Δτ calculated in step S225 e and Doppler correction Δf d , the signal delay calculation value and Doppler frequency calculation value of GNSS-R signal and GNSS-S signal are corrected to obtain the final signal delay Δτ and Doppler frequency f d , and its calculation formula is:

[0086]

[0087] GNSS-R signal power is strong, and the pseudo-ranges ρ1, ρ2, ..., ρ of the transmitted signal can be directly obtained m Pseudorange rate Based on this, the deviation values ​​of m GNSS-R signals can be calculated, and their average value can be taken as the correction value of pseudorange and Doppler to obtain the delay correction value Δτ e and Doppler correction Δf d , and then use the calculated delay correction Δτ e and Doppler correction Δf d All GNSS-R and GNSS-S signals are corrected for the common deviation.

[0088] Step S23, perform two-dimensional back projection on the three-dimensional echo signal, find the signal energy value from the three-dimensional echo signal according to the signal delay and Doppler frequency of each grid point in the target area, and project it to the corresponding grid point in the target area to form a single star image of the target area.

[0089] According to the signal delay Δτ and Doppler frequency f at each grid point in the target area d Parameters, from the three-dimensional echo signal of "fast time-slow time-Doppler frequency", find the corresponding echo energy data along the fast time τ and Doppler frequency dimensions, back-project to each grid point, and take the synthetic aperture time as T SAR seconds, T SAREach set of data within a second is projected onto the target grid area and coherently accumulated to obtain an image of a single satellite.

[0090] Step S23 specifically includes:

[0091] Step S231: According to the signal delay and Doppler frequency of each grid point in the target area, the corresponding echo energy data is searched along the fast time τ and Doppler frequency dimensions from the three-dimensional echo signal of "fast time-slow time-Doppler frequency", and its amplitude A is taken. E , and take the fast time as Δτ and the Doppler frequency f d =0 signal phase θ E , forming the back projection signal s(A E ,θ E ).

[0092] The three-dimensional structure can fully capture the changes of radar signals in different dimensions, including the time domain characteristics of the signal (fast time) and the motion trajectory of the radar platform (slow time). The small time changes in the fast time dimension help to extract the fine features of the signal, thereby improving the imaging resolution; the slow time dimension reflects the movement of the radar platform along the trajectory, which helps to capture and analyze dynamic targets or changing environments.

[0093] Step S232: the back projection signal s(A E ,θ E ) multiplied by the phase compensation factor exp(-j·2π·f carrier ·Δτ), and then projected to each grid point, where j is the imaginary unit and f carrier is the carrier center frequency of the GNSS signal.

[0094] Step S233: for multiple sets of data in the slow time dimension t generated when the radar receiver moves along the target area, a synthetic aperture time T is taken according to the slow time t dimension in the three-dimensional echo signal. SAR seconds of data, T SAR Each set of data within a second is projected onto the grid of the target area in the manner of step S231 to step S232, and complex accumulation is performed to obtain a single star image of the target area.

[0095] Step S24, executing steps S21 to S23 for all visible GNSS satellites to obtain a single-star image of the target area corresponding to each GNSS satellite, and fusing the obtained multiple single-star images according to grid points.

[0096] like Figure 7 As shown, in step S24, it specifically includes:

[0097] The single-star images of GNSS satellites corresponding to m GNSS-R signals and the single-star images of GNSS satellites corresponding to n GNSS-S signals are non-coherently accumulated and fused according to the corresponding positions of the grid points in the target area to obtain the final target area image. The calculation formula is as follows:

[0098]

[0099] Among them, I all represents the multi-star image obtained after non-coherent accumulation fusion, I i Represents the single-star image of the i-th GNSS satellite.

[0100] In summary, the invention proposes a multi-source GNSS-R / S integrated imaging method, which uses the reflected signal and scattered signal of the target area after the global navigation satellite signal reaches the ground for integrated imaging, and combines the characteristics of the strong power of the GNSS-R reflected signal and the multi-dimensionality of the GNSS-S signal to achieve high-quality imaging based on the GNSS signal. The movement of the target area is imaged synthetically by the GNSS-R / S radar, and the GNSS-R / S signal is demodulated two-dimensionally according to the characteristics of the navigation signal to obtain a three-dimensional signal of "fast time-slow time-Doppler frequency". The high-power GNSS-R signal is used for real-time tracking to obtain the pseudorange and pseudorange rate of the satellite, and the signal delay and Doppler frequency of the target area calculated by the geometric relationship are corrected to obtain the accurate delay and Doppler frequency values ​​of the target area. Finally, the target area is back-projected two-dimensionally to obtain a single-star image of the area, and the single-star images of all visible satellites are non-coherently accumulated to further improve the signal-to-noise ratio of the imaging. Compared with the traditional SAR imaging method of external radiation source radar, it makes full use of the characteristics of GNSS signals for two-dimensional demodulation, and uses the strong GNSS-R signal to correct the imaging geometry. In the process of back-projection of echo signals, a Doppler frequency dimension is added to the back-projection to achieve high-quality imaging of GNSS signals and lay the foundation for feature recognition of the target.

[0101] According to one aspect of the present invention, there is provided an electronic device, comprising: one or more processors, one or more memories, and one or more computer programs; wherein the processor is connected to the memory, and the one or more computer programs are stored in the memory, and when the electronic device is running, the processor executes the one or more computer programs stored in the memory, so that the electronic device performs a multi-source GNSS-R / S integrated imaging method as any one of the above technical solutions.

[0102] The processor may be a central processing unit (CPU), or other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0103] According to one aspect of the present invention, a computer-readable storage medium is provided for storing computer instructions. When the computer instructions are executed by a processor, a multi-source GNSS-R / S integrated imaging method as described in any one of the above technical solutions is implemented.

[0104] Computer-readable storage media may include any medium capable of storing or transmitting information. Examples of computer-readable storage media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, optical fiber media, radio frequency (RF) links, etc. Code segments may be downloaded via computer networks such as the Internet, intranets, etc.

[0105] In addition, it should be noted that the present invention can be provided as a method, an apparatus or a computer program product. Therefore, the embodiments of the present invention can take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the embodiments of the present invention can take the form of a computer program product implemented on one or more computer-usable storage media containing computer-usable program code.

[0106] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0107] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device, so that a series of operation steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable terminal device provide for implementing the process in the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0108] It should also be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0109] Finally, it should be noted that the above is a preferred embodiment of the present invention. It should be pointed out that although the preferred embodiment of the present invention has been described, for those skilled in the art, once the basic creative concept of the present invention is known, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention. Therefore, the attached claims are intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the embodiments of the present invention.

Claims

1. A multi-source GNSS-R / S integrated imaging method, characterized in that: The following steps are involved: Step S1, according to the geometric relationship between the target area, the GNSS satellite and the radar receiver, obtaining the GNSS signal reflected by the target area; the GNSS signal includes m GNSS-R signals and n GNSS-S signals, the GNSS-R signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and reflected by the mirror surface of the target area, and the GNSS-S signal is a signal received by the radar receiver after being transmitted by the GNSS satellite and backscattered by the target area; Step S2: The radar receiver moves along the target area, simultaneously receives and processes all GNSS-R signals and GNSS-S signals reflected by the target area, and forms an image of the target area using a synthetic aperture method.

2. The multi-source GNSS-R / S integrated imaging method according to claim 1, characterized in that: In the step S2, it specifically includes: Step S21, performing two-dimensional demodulation on the GNSS-R signal and the GNSS-S signal to obtain a three-dimensional echo signal of "fast time-slow time-Doppler frequency" with the carrier frequency and code phase of the direct signal as the origin; Step S22, obtaining the signal delay and Doppler frequency of the target area; Step S23, performing two-dimensional back-projection on the three-dimensional echo signal, searching for a signal energy value from the three-dimensional echo signal according to the signal delay and Doppler frequency of each grid point of the target area, and projecting the signal energy value to the corresponding grid point of the target area to form a single-star image of the target area; Step S24, executing steps S21 to S23 for all visible GNSS satellites to obtain a single-star image of the target area corresponding to each GNSS satellite, and fusing the obtained multiple single-star images according to grid points.

3. The multi-source GNSS-R / S integrated imaging method according to claim 2, characterized in that: In the step S21, two-dimensional demodulation is performed on the GNSS-R signal and the GNSS-S signal, specifically including: Step S211: for any of the GNSS-R signals or the GNSS-S signals, the code phase C of the corresponding direct signal is taken as the starting point, and a PRN code period T is set. code As a unit, intercept a section of signal; Step S212: The intercepted signal is subjected to the carrier frequency f of the corresponding direct signal. c is the center frequency, within ±f M Carrier demodulation is performed at intervals of Δf within the frequency range of M The value of the interval Δf is determined according to the radial velocity of the relative motion between the target area being measured and the radar receiver; Step S213: Perform PRN code correlation on the demodulated signal to obtain a frequency range of -f M :+f M 、Time range is 0~T code "Time-frequency" two-dimensional signal; Step S214: When the radar receiver moves along the target area, the steps S211 to S213 are sequentially executed for each segment of the GNSS-R signal or the GNSS-S signal received sequentially to obtain multiple segments of "time-frequency" two-dimensional signals, and the time in each segment of the "time-frequency" two-dimensional signal is defined as the fast time τ, and the time of movement of the radar receiver is defined as the slow time t, so as to form the three-dimensional echo signal of "fast time-slow time-Doppler frequency", and the three-dimensional echo signal is in the form of a complex number.

4. The multi-source GNSS-R / S integrated imaging method according to claim 3, characterized in that: In the step S22, it specifically includes: Step S221: Calculate the position and velocity of the GNSS satellite corresponding to the direct signal according to the direct signal, and record the position of the i-th GNSS satellite as The speed of the i-th GNSS satellite is Step S222: Calculate the position of the radar receiver corresponding to the direct signal according to the direct signal: x ,R y ,R z ), the speed of the radar receiver corresponding to the direct signal is (V x ,V y ,V z ); Step S223: Divide the target area into grids, and record the position coordinates of the kth grid center as Step S224: Calculate the signal delay value of the target area based on the geometric relationship and Doppler frequency calculation value Among them, the signal delay calculation value of the kth grid is and Doppler frequency calculation value The calculation formulas are: in, Where c is the speed of light; Step S225: real-time tracking of GNSS-R signals to obtain pseudo-ranges ρ1, ρ2, ..., ρ of reflected signals of m GNSS satellites corresponding to the GNSS-R signals. m , reflected signal pseudorange rate Calculate the delay difference and Doppler deviation of the m GNSS-R signals, and take the average value as the delay correction value Δτ e and Doppler correction Δf d , and its calculation formula is: Step S226: The delay correction value Δτ calculated in step S225 e and Doppler correction Δf d , the signal delay calculation value and Doppler frequency calculation value of GNSS-R signal and GNSS-S signal are corrected to obtain the final signal delay Δτ and Doppler frequency f d , and its calculation formula is:

5. The multi-source GNSS-R / S integrated imaging method according to claim 3, characterized in that: In the step S23, performing two-dimensional back projection on the echo signal specifically includes: Step S231: According to the signal delay and Doppler frequency of each grid point in the target area, the corresponding echo energy data is searched along the fast time τ and Doppler frequency dimensions from the three-dimensional echo signal of "fast time-slow time-Doppler frequency", and its amplitude A is taken. E , and take the fast time as Δτ and the Doppler frequency f d =0 signal phase θ E , forming the back projection signal s(A E ,θ E ); Step S232: the back projection signal s(A E ,θ E ) multiplied by the phase compensation factor exp(-j·2π·f carrier ·Δτ), and then projected to each grid point, where j is the imaginary unit and f carrier is the carrier center frequency of the GNSS signal; Step S233: for multiple groups of data of slow time dimension t generated when the radar receiver moves along the target area, a synthetic aperture time T is taken according to the slow time t dimension in the three-dimensional echo signal. SAR seconds of data, T SAR Each set of data within a second is projected onto the grid of the target area in the manner of step S231 to step S232, and complex accumulation is performed to obtain a single star image of the target area.

6. The multi-source GNSS-R / S integrated imaging method according to claim 4, characterized in that: In the step S24, specifically including: The single-star images of the GNSS satellites corresponding to the m GNSS-R signals and the single-star images of the GNSS satellites corresponding to the n GNSS-S signals are non-coherently accumulated and fused according to the corresponding positions of the grid points of the target area to obtain a final target area image.

7. An electronic device, characterized in that: include: One or more processors, one or more memories, and one or more computer programs; wherein the processor is connected to the memory, and the one or more computer programs are stored in the memory. When the electronic device is running, the processor executes the one or more computer programs stored in the memory, so that the electronic device performs the multi-source GNSS-R / S integrated imaging method as described in any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, implement the multi-source GNSS-R / S integrated imaging method as described in any one of claims 1 to 6.

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