Ionospheric imaging method and device based on space-frequency two-dimensional spectrum estimation technology

Abstract

The present application relates to an ionospheric imaging method and device based on space-frequency two-dimensional spectrum estimation technology, wherein the method includes: using a preset spread spectrum modulation mode and a preset echo sampling frequency to perform ionospheric detection, and obtaining an echo signal for each detection; transforming the echo signal for each detection into the frequency domain, and arranging the transformed echo signal according to the number of detections to generate an echo matrix, and intercepting and reconstructing the echo matrix using the diagonal of the echo matrix to obtain a reconstructed echo matrix; constructing a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and performing two-dimensional spectrum estimation using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result; arranging the spectrum estimation results according to the direction and order of the steering vector construction to obtain an ionospheric super-resolution imaging result. The embodiment of the present application can simultaneously utilize the coherence between the frequencies of the detection echo and the coherence of the echo signal between multiple detections of the same frequency component, and simultaneously realize high-resolution spectrum estimation in the distance dimension and the Doppler dimension.

Description

Technical Field

[0001] The present application relates to the field of ionospheric detection technology, and in particular to an ionospheric imaging method and device based on space-frequency two-dimensional spectrum estimation technology. Background Art

[0002] The ionosphere is a mid-to-high atmospheric structure in the Earth's atmosphere that is partially ionized by solar radiation. It has a distinct layered structure and is modulated by magnetic fields, atmospheric disturbances, solar radiation changes, and even geological and meteorological changes. It has a complex structure and evolution process. Since the ionosphere wraps around the Earth and is indestructible, and its electron density is sufficient to reflect radio signals, research on its structure and evolution process plays an important role in understanding the propagation process of radio signals, especially shortwave signals, and thus has important practical guiding significance in civil and military fields such as communications and reconnaissance.

[0003] In the related technologies for ionospheric observation and research, ground-based ionospheric detection systems often use experiments to transmit shortwave signals to the ionosphere and measure the return signals to analyze the electron density distribution of the ionosphere and the motion state of its internal fine structure through Doppler analysis. However, due to the limited coherent bandwidth of the ionosphere, the pulse width of the detection system is not easy to reduce, resulting in a distance resolution of several kilometers. In addition, due to the high altitude of the ionosphere, the detection system is a comprehensive ionospheric state, which will result in a long detection cycle. Therefore, if you want to obtain accurate Doppler information of the ionosphere, it means that you need to conduct multiple and long-term coherent detections, which seriously affects the detection efficiency of the ionosphere.

[0004] At present, although the relevant technology can use spectrum estimation technology to significantly improve the distance resolution and Doppler resolution of ionospheric detection respectively, and can combine the aggregation of each frequency component of the signal along the distance dimension and the frequency domain spectrum estimation technology to simultaneously improve the distance and Doppler resolution, it can significantly improve the detection accuracy with fewer detection times and without changing the pulse width of the detection signal.

[0005] However, the relevant technology cannot simultaneously and equally improve the distance and Doppler resolution of ionospheric detection. The single-dimensional spectral estimation method can only act on one of the range domain or the Doppler domain. In the method of frequency domain energy aggregation combined with spectral estimation, the imaging capability of the distance dimension is weaker than that of the Doppler dimension, and it is difficult to achieve a balance between the detection distance dimension and the detection accuracy, which needs to be improved. Summary of the invention

[0006] The present application provides an ionospheric imaging method and device based on space-frequency two-dimensional spectrum estimation technology to solve the technical problem in the related technology that the single-dimensional spectrum estimation method can only act on one of the range domain or the Doppler domain, while the frequency domain energy aggregation combined with the spectrum estimation method has weak imaging capability in the range dimension, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy.

[0007] The first aspect of the present application provides an ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology, comprising the following steps: performing ionospheric detection using a preset spread spectrum modulation method and a preset echo sampling frequency to obtain an echo signal for each detection; transforming the echo signal for each detection into the frequency domain, and arranging the transformed echo signals according to the number of detections to generate an echo matrix, and intercepting and reconstructing the echo matrix using the diagonal of the echo matrix to obtain a reconstructed echo matrix; constructing a two-dimensional steering vector according to a spatial domain sampling rate and a frequency domain sampling rate, and performing two-dimensional spectrum estimation using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result; arranging the spectrum estimation results according to the construction direction and order of the steering vector to obtain an ionospheric super-resolution imaging result.

[0008] Optionally, in one embodiment of the present application, the preset echo sampling frequency is greater than or equal to the spread spectrum modulation bandwidth of the preset spread spectrum modulation mode.

[0009] Optionally, in one embodiment of the present application, the echo signal is transformed into the frequency domain and the transformed echo signal is arranged according to the number of detections to obtain an echo matrix, including: transforming the echo signal into the frequency domain to obtain a corresponding output sequence, wherein the adjacent frequency interval of the output sequence is less than or equal to the spread spectrum modulation bandwidth; and obtaining the echo matrix based on the output sequence.

[0010] Optionally, in one embodiment of the present application, the echo matrix is ​​truncated and reconstructed using the diagonal of the echo matrix to obtain a reconstructed echo matrix, including: truncating the echo matrix using the diagonal and a preset interval to obtain a plurality of sub-matrices that meet preset estimation accuracy conditions; expanding the sub-matrices into vectors, and arranging and reconstructing the vectors to obtain the reconstructed echo matrix.

[0011] Optionally, in one embodiment of the present application, the step of truncating and reconstructing the echo matrix using the diagonal of the echo matrix to obtain a reconstructed echo matrix includes: adjusting the size of the submatrix so that the submatrix satisfies preset imaging and operation conditions.

[0012] Optionally, in one embodiment of the present application, constructing a two-dimensional steering vector based on a spatial domain sampling rate and a frequency domain sampling rate includes: constructing a distance steering vector for distance using the spatial domain sampling rate; constructing a frequency steering vector for frequency using the frequency domain sampling rate; and obtaining the two-dimensional steering vector based on the distance steering vector and the frequency steering vector.

[0013] Optionally, in one embodiment of the present application, the two-dimensional spectrum estimation is performed using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result, including: obtaining a first covariance matrix of the reconstructed echo matrix based on the two-dimensional steering vector; regularizing the first covariance matrix to obtain a second covariance matrix that satisfies a preset numerical stability condition; performing two-dimensional spectrum estimation on the second covariance matrix to obtain the spectrum estimation result; wherein the expression of the spectrum estimation result is:

[0014]

[0015]

[0016] Among them, F row (k,v) represents the row spectrum estimation result, c row (k,v) represents the row-direction two-dimensional steering vector form, R row represents the first covariance matrix, * H represents the conjugate transpose, N h Indicates the number of range gates after improving the range resolution, M h Indicates the number of Doppler frequency points after improving the Doppler resolution, F col (k,v) represents the column spectrum estimation result, c col (k,v) represents the row-direction two-dimensional steering vector form, R col Denotes the second covariance matrix.

[0017] The second aspect of the present application provides an ionospheric imaging device based on space-frequency two-dimensional spectrum estimation technology, including: a detection module, which is used to perform ionospheric detection using a preset spread spectrum modulation method and a preset echo sampling frequency to obtain an echo signal for each detection; a reconstruction module, which is used to transform the echo signal for each detection into the frequency domain, and arrange the transformed echo signals according to the number of detections to generate an echo matrix, and use the diagonal of the echo matrix to intercept and reconstruct the echo matrix to obtain a reconstructed echo matrix; an estimation module, which is used to construct a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and use the reconstructed echo matrix and the two-dimensional steering vector to perform two-dimensional spectrum estimation to obtain a spectrum estimation result; an imaging module, which is used to arrange the spectrum estimation results according to the construction direction and order of the steering vector to obtain an ionospheric super-resolution imaging result.

[0018] Optionally, in one embodiment of the present application, the preset echo sampling frequency is greater than or equal to the spread spectrum modulation bandwidth of the preset spread spectrum modulation mode.

[0019] Optionally, in one embodiment of the present application, the reconstruction module includes: a transformation unit, used to transform the echo signal into the frequency domain to obtain a corresponding output sequence, wherein the adjacent frequency interval of the output sequence is less than or equal to the spread spectrum modulation bandwidth; and a first calculation unit, used to obtain the echo matrix based on the output sequence.

[0020] Optionally, in one embodiment of the present application, the reconstruction module includes: a truncation unit, used to truncate the echo matrix using the diagonal line and a preset interval to obtain multiple sub-matrices that meet preset estimation accuracy conditions; a reconstruction unit, used to expand the sub-matrix into a vector, and arrange and reconstruct the vector to obtain the reconstructed echo matrix.

[0021] Optionally, in one embodiment of the present application, the reconstruction module includes: an adjustment unit, configured to adjust the size of the sub-matrix so that the sub-matrix satisfies preset imaging and operation conditions.

[0022] Optionally, in one embodiment of the present application, the estimation module includes: a first construction unit, used to construct a distance-oriented vector for distance using the spatial domain sampling rate; a second construction unit, used to construct a frequency-oriented vector for frequency using the frequency domain sampling rate; and a second calculation unit, used to obtain the two-dimensional steering vector based on the distance-oriented vector and the frequency-oriented vector.

[0023] Optionally, in one embodiment of the present application, the estimation module includes: a third calculation unit, used to obtain a first covariance matrix of the reconstructed echo matrix based on the two-dimensional steering vector; a fourth calculation unit, used to perform regularization processing on the first covariance matrix to obtain a second covariance matrix that satisfies a preset numerical stability condition; an estimation unit, used to perform two-dimensional spectrum estimation on the second covariance matrix to obtain the spectrum estimation result;

[0024] Wherein, the expression of the spectrum estimation result is:

[0025]

[0026] Among them, F row (k,v) represents the row spectrum estimation result, c row (k,v) represents the row-direction two-dimensional steering vector form, R row represents the first covariance matrix, * H represents the conjugate transpose, N hIndicates the number of range gates after improving the range resolution, M h Indicates the number of Doppler frequency points after improving the Doppler resolution, F col (k,v) represents the column spectrum estimation result, c col (k,v) represents the row-direction two-dimensional steering vector form, R col Denotes the second covariance matrix.

[0027] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology as described in the above embodiment.

[0028] The fourth aspect of the present application provides a computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable the computer to execute the ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology as described in the above embodiment.

[0029] The fifth aspect of the present application provides a computer program product, including a computer program, which, when executed, is used to implement the above-mentioned ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology.

[0030] The embodiment of the present application can use a preset spread spectrum modulation method and a preset echo sampling frequency to perform ionospheric detection, obtain an echo signal for each detection, and transform the echo signal for each detection into the frequency domain, arrange the transformed echo signals according to the number of detections, generate an echo matrix, and then perform interception and reconstruction of the echo matrix to obtain a reconstructed echo matrix, and then construct a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and use the reconstructed echo matrix and the two-dimensional steering vector to perform two-dimensional spectrum estimation to obtain a spectrum estimation result; arrange the spectrum estimation results according to the construction direction and order of the steering vector to obtain an ionospheric super-resolution imaging result, and simultaneously realize high-resolution spectrum estimation of the distance dimension and the Doppler dimension by simultaneously utilizing the coherence between the frequencies of the detection echo and the coherence of the echo signals between multiple detections of the same frequency component, and at the same time equally improve the distance dimension and the Doppler dimension resolution of the ionospheric detection, thereby improving the detection accuracy of the two dimensions equally. Thereby, the technical problem in the related art that the single-dimensional spectral estimation method can only act on one of the distance domain or the Doppler domain, and the imaging capability of the distance dimension of the frequency domain energy aggregation combined with the spectral estimation method is weak, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy is solved.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0033] Figure 1 A flowchart of an ionospheric imaging method based on a space-frequency two-dimensional spectrum estimation technology provided according to an embodiment of the present application;

[0034] Figure 2 Schematic diagram of the principle of an ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology according to an embodiment of the present application;

[0035] Figure 3 It is a flowchart of an ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology according to one embodiment of the present application;

[0036] Figure 4a This is a time domain schematic diagram of an ionospheric detection echo with a distance resolution of 3.84 km according to an embodiment of the present application;

[0037] Figure 4b This is a schematic diagram of range-Doppler imaging results with a range resolution of 3.84 km and a Doppler resolution of 0.24 Hz according to an embodiment of the present application;

[0038] Figure 4c This is a schematic diagram of range-Doppler high-resolution imaging results with a range resolution of 0.384 km and a Doppler resolution of 0.024 Hz according to an embodiment of the present application;

[0039] Figure 5 This is a schematic diagram of range-Doppler high-resolution imaging results with a range resolution of 0.384 km and a Doppler resolution of 0.024 Hz according to another embodiment of the present application;

[0040] Figure 6a A schematic diagram of ionospheric high-resolution imaging results according to an embodiment of the present application;

[0041] Figure 6b A schematic diagram of ionospheric high-resolution imaging results according to another embodiment of the present application;

[0042] Figure 7 A schematic diagram of the structure of an ionospheric imaging device based on a space-frequency two-dimensional spectrum estimation technology provided according to an embodiment of the present application;

[0043] Figure 8 It is a schematic diagram of the structure of an electronic device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0044] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0045] The following describes the ionospheric imaging method and device based on the space-frequency two-dimensional spectrum estimation technology of the embodiment of the present application with reference to the accompanying drawings. In view of the technical problem that the single-dimensional spectrum estimation method in the related technologies mentioned in the above background technology can only act on one of the distance domain or the Doppler domain, and the imaging capability of the distance dimension of the frequency domain energy aggregation combined with the spectrum estimation method is weak, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy, the present application provides an ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology, in which a preset spread spectrum modulation method and a preset echo sampling frequency can be used to perform ionospheric detection, and the echo signal of each detection is obtained, and the echo signal of each detection is transformed into the frequency domain, and the transformed echo signals are arranged according to the number of detections to generate an echo matrix, Thus, the echo matrix is ​​intercepted and reconstructed to obtain a reconstructed echo matrix, and then a two-dimensional steering vector is constructed according to the spatial domain sampling rate and the frequency domain sampling rate, and the reconstructed echo matrix and the two-dimensional steering vector are used to perform two-dimensional spectrum estimation to obtain a spectrum estimation result; the spectrum estimation results are arranged according to the construction direction and order of the steering vector to obtain the ionosphere super-resolution imaging result, and by simultaneously utilizing the coherence between the frequencies of the detection echoes and the coherence of the echo signals between multiple detections of the same frequency component, high-resolution spectrum estimation of the distance dimension and the Doppler dimension is achieved at the same time, and the resolution of the distance dimension and the Doppler dimension of the ionosphere detection is equally improved, thereby improving the detection accuracy of the two dimensions equally. Thus, the technical problem that the single-dimensional spectrum estimation method in the related art can only act on one of the distance domain or the Doppler domain, and the imaging capability of the distance dimension of the frequency domain energy aggregation combined with the spectrum estimation method is weak, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy is solved.

[0046] Specifically, Figure 1 A schematic flow chart of an ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology provided in an embodiment of the present application.

[0047] like Figure 1 As shown, the ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology includes the following steps:

[0048] In step S101, ionosphere detection is performed using a preset spread spectrum modulation method and a preset echo sampling frequency to obtain an echo signal for each detection.

[0049] During the actual implementation process, the embodiment of the present application can determine the spread spectrum modulation method and echo sampling rate of ionosphere detection, and use the preset spread spectrum modulation method and the preset echo sampling frequency to perform ionosphere detection, obtain the echo signal of each detection, so as to perform ionosphere detection and perform echo demodulation based on the spread spectrum modulation method.

[0050] The preset spread spectrum modulation mode and the preset echo sampling frequency may be set accordingly by those skilled in the art according to actual conditions, and are not specifically limited here.

[0051] Optionally, in one embodiment of the present application, the preset echo sampling frequency is greater than or equal to a spread spectrum modulation bandwidth of a preset spread spectrum modulation method.

[0052] Among them, the echo sampling rate f s It should not be less than the spread spectrum modulation bandwidth B to ensure that the distance component in the two-dimensional steering vector does not cause the generation of pseudo peaks.

[0053] In step S102, the echo signal of each detection is transformed into the frequency domain, and the transformed echo signals are arranged according to the number of detections to generate an echo matrix, and the echo matrix is ​​truncated and reconstructed using the diagonal of the echo matrix to obtain a reconstructed echo matrix.

[0054] As a possible implementation method, the embodiment of the present application can transform a single detection echo signal into the frequency domain and arrange it according to the number of detections to form an echo matrix, and intercept and reconstruct the echo signal matrix along the diagonal of the echo matrix to obtain a reconstructed echo matrix.

[0055] Optionally, in one embodiment of the present application, the echo signal is transformed into the frequency domain, and the transformed echo signal is arranged according to the number of detections to obtain an echo matrix, including: transforming the echo signal into the frequency domain to obtain a corresponding output sequence, wherein the adjacent frequency interval of the output sequence is less than or equal to the spread spectrum modulation bandwidth; and obtaining the echo matrix based on the output sequence.

[0056] Among them, the adjacent frequency interval of the output sequence of the fast Fourier transform performed when transforming a single detection echo signal into the frequency domain is not greater than the spread spectrum modulation bandwidth B, so as to ensure that the phase difference between adjacent frequency components of the echo signal in a single detection is no greater than 2π, thereby ensuring that the distance component in the two-dimensional steering vector will not cause the generation of pseudo peaks in the spectrum estimation.

[0057] Optionally, in one embodiment of the present application, the echo matrix is ​​truncated and reconstructed using the diagonal of the echo matrix to obtain a reconstructed echo matrix, including: truncating the echo matrix using the diagonal and preset intervals to obtain multiple sub-matrices that meet preset estimation accuracy conditions; expanding the sub-matrices into vectors, and arranging and reconstructing the vectors to obtain a reconstructed echo matrix.

[0058] In some embodiments, the embodiment of the present application can intercept the original echo matrix along the diagonal of the echo matrix at intervals of 1 row and 1 column. o It is expressed as the following formula:

[0059]

[0060] Among them, s m (f m ) is the nth (n=

[0061] 1, 2, …, N frequency components, M is the number of coherent detections, and N is the maximum distance gate for a single detection.

[0062] In this embodiment of the present application, the original echo matrix S o By intercepting along the diagonal line at intervals of 1 row and 1 column, the lth (l = 1, 2, ..., L) submatrix can be obtained as shown below:

[0063]

[0064] Among them, it should be ensured that L+P≤N, L+Q≤M. In this way, the maximum number of sub-matrices can be obtained while ensuring that no pseudo peaks are generated during the two-dimensional spectrum estimation process, thereby obtaining the best estimation accuracy.

[0065] The truncated echo sub-matrix should be expanded into a vector and then arranged and reconstructed. Since there are two forms of expansion, row-wise expansion and column-wise expansion, two forms of reconstructed matrices can be obtained.

[0066] If s l (f l ) is written in the form of row vectors, then:

[0067]

[0068] in,* T Indicates transpose.

[0069] If s l (f l ) is written in the form of a column vector, then:

[0070]

[0071] Then we can get the reconstructed matrix S in two forms: row expansion and column expansion row and S col As shown below:

[0072]

[0073] Optionally, in one embodiment of the present application, the echo matrix is ​​truncated and reconstructed using the diagonal of the echo matrix to obtain a reconstructed echo matrix, including: adjusting the size of the sub-matrix so that the sub-matrix meets preset imaging and operation conditions.

[0074] In the actual implementation process, matrix reconstruction can balance the imaging effect and computing time by flexibly adjusting the size of the intercepted matrix.

[0075] The preset imaging and operation conditions may be set by those skilled in the art according to actual conditions, and are not specifically limited here.

[0076] In step S103, a two-dimensional steering vector is constructed according to the spatial domain sampling rate and the frequency domain sampling rate, and a two-dimensional spectrum is estimated using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result.

[0077] As a possible implementation method, the embodiment of the present application can construct a two-dimensional steering vector based on the space (distance) and frequency (Doppler) sampling rate, and use the space-frequency two-dimensional steering vector and the reconstructed echo matrix to perform two-dimensional spectrum estimation to obtain a spectrum estimation result.

[0078] Optionally, in one embodiment of the present application, a two-dimensional steering vector is constructed based on the spatial domain sampling rate and the frequency domain sampling rate, including: constructing a distance steering vector for distance using the spatial domain sampling rate; constructing a frequency steering vector for frequency using the frequency domain sampling rate; and obtaining a two-dimensional steering vector based on the distance steering vector and the frequency steering vector.

[0079] Furthermore, the embodiment of the present application can construct the distance dimension for the distance r according to the spatial and frequency sampling rates. k (r k is not greater than the maximum unambiguous distance) and the Doppler dimension for the frequency f v (f v The steering vectors a(k) and b(v) that are not greater than the maximum unambiguous Doppler frequency are as follows:

[0080]

[0081] Among them, N h To improve the number of range gates after the range resolution is improved, if the original range resolution is Δr o , the required range resolution of high-resolution imaging is Then we have:

[0082]

[0083] Similarly, in Doppler we have:

[0084]

[0085] Among them, M h To improve the Doppler frequency after the Doppler resolution is increased, if the original Doppler resolution is Δf o , the required distance resolution of high-resolution imaging is Δf, then:

[0086]

[0087] Therefore, the two expansion methods of the embodiment of the present application are for the distance r k With Doppler frequency f v Two forms of 2D steering vectors can be constructed:

[0088]

[0089] in, represents the Kronecker product.

[0090] Optionally, in one embodiment of the present application, a two-dimensional spectrum estimation is performed using a reconstructed echo matrix and a two-dimensional steering vector to obtain a spectrum estimation result, including: obtaining a first covariance matrix of the reconstructed echo matrix based on the two-dimensional steering vector; regularizing the first covariance matrix to obtain a second covariance matrix that satisfies a preset numerical stability condition; performing a two-dimensional spectrum estimation on the second covariance matrix to obtain a spectrum estimation result; wherein the expression of the spectrum estimation result is:

[0091]

[0092] Among them, F row (k,v) represents the row spectrum estimation result, c row (k,v) represents the row-direction two-dimensional steering vector form, R row represents the first covariance matrix, * H represents the conjugate transpose, N h Indicates the number of range gates after improving the range resolution, M h Indicates the number of Doppler frequency points after improving the Doppler resolution, F col (k,v) represents the column spectrum estimation result, c col (k,v) represents the row-direction two-dimensional steering vector form, R col represents the second covariance matrix.

[0093] Furthermore, the embodiment of the present application may adopt the Capon spectrum estimation method, based on the above two expansion methods, to obtain the covariance matrix of the reconstructed signal matrix:

[0094]

[0095] in,* H represents the conjugate transpose.

[0096] In order to ensure the numerical stability of computer calculation when inverting the covariance matrix in Capon spectrum estimation, the embodiment of the present application can regularize the covariance matrix, that is, add a relatively small amount to its main diagonal. Finally, two expanded forms of space-frequency two-dimensional spectrum estimation results can be obtained based on the Capon spectrum estimation algorithm:

[0097]

[0098] The resolutions of the distance dimension and the Doppler dimension of the embodiment of the present application are respectively and times.

[0099] In step S104, the spectrum estimation results are arranged according to the direction and order of the steering vector construction to obtain the ionospheric super-resolution imaging results.

[0100] In the actual implementation process, the embodiment of the present application can arrange the spectrum estimation results according to the direction and order of the steering vector construction to obtain the ionospheric super-resolution imaging results.

[0101] Combination Figure 2 As shown in FIG6 , the working principle of the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology of the embodiment of the present application is described in detail with an embodiment.

[0102] like Figure 2 As shown, the working principle of an embodiment of the present application is as follows: an ionospheric detection system (such as a vertical meter) is used to modulate the shortwave signal for detection by spread spectrum, and the reflected echo of the ionosphere is first transformed in the frequency domain, and the echo matrix is ​​reconstructed according to the coherence between each frequency component and the coherence between multiple detection echoes, and a two-dimensional guidance vector of distance (space)-Doppler (frequency) is constructed, and then super-resolution imaging of the ionosphere is achieved by performing space-frequency two-dimensional spectrum estimation.

[0103] Furthermore, if Figure 3 As shown, the embodiment of the present application may include the following steps:

[0104] Step S301: Determine the spread spectrum modulation mode and echo sampling rate for ionospheric detection. s It should not be less than the spread spectrum modulation bandwidth B to ensure that the distance component in the two-dimensional steering vector does not cause the generation of pseudo peaks.

[0105] Step S302: perform ionosphere detection and perform echo demodulation based on spread spectrum modulation.

[0106] Step S303: transform the single detection echo signal into the frequency domain and arrange it according to the detection times to form an echo matrix. The adjacent frequency interval of the output sequence of the fast Fourier transform performed when transforming the single detection echo signal into the frequency domain is not greater than the spread spectrum modulation bandwidth to ensure that the distance component in the two-dimensional steering vector will not cause the generation of pseudo peaks.

[0107] Step S304: truncate and reconstruct the echo signal matrix along the diagonal line of the echo matrix.

[0108] In the embodiment of the present application, the original echo matrix can be intercepted at intervals of 1 row and 1 column along the diagonal of the echo matrix. o It is expressed as the following formula:

[0109]

[0110] Among them, s m (f m ) is the nth (n=

[0111] 1, 2, …, N frequency components, M is the number of coherent detections, and N is the maximum distance gate for a single detection.

[0112] In this embodiment of the present application, the original echo matrix S o By intercepting along the diagonal line at intervals of 1 row and 1 column, the lth (l = 1, 2, ..., L) submatrix can be obtained as shown below:

[0113]

[0114] Among them, it should be ensured that L+P≤N, L+Q≤M. In this way, the maximum number of sub-matrices can be obtained while ensuring that no pseudo peaks are generated during the two-dimensional spectrum estimation process, thereby obtaining the best estimation accuracy.

[0115] The truncated echo sub-matrix should be expanded into a vector and then arranged and reconstructed. Since there are two forms of expansion, row-wise expansion and column-wise expansion, two forms of reconstructed matrices can be obtained.

[0116] If s l (f l ) is written in the form of row vectors, then:

[0117]

[0118] in,* T Indicates transpose.

[0119] If s l (f l ) is written in the form of a column vector, then:

[0120]

[0121] Then we can get the reconstructed matrix S in two forms: row expansion and column expansion row and S col As shown below:

[0122]

[0123] Among them, matrix reconstruction can balance the imaging effect and calculation time by flexibly adjusting the size of the intercepted matrix.

[0124] Step S305: construct a two-dimensional steering vector according to the spatial (range) and frequency (Doppler) sampling rates.

[0125] In the embodiment of the present application, the distance dimension can be constructed according to the spatial and frequency sampling rates. k (r k is not greater than the maximum unambiguous distance) and the Doppler dimension for the frequency f v (f v The steering vectors a(k) and b(v) that are not greater than the maximum unambiguous Doppler frequency are as follows:

[0126]

[0127] Among them, N h To improve the number of range gates after the range resolution is improved, if the original range resolution is Δr o , the required range resolution of high-resolution imaging is Then we have:

[0128]

[0129] Similarly, in Doppler we have:

[0130]

[0131] Among them, M h To improve the Doppler frequency after the Doppler resolution is increased, if the original Doppler resolution is Δf o , the required distance resolution of high-resolution imaging is Δf, then:

[0132]

[0133] Therefore, the two expansion methods of the embodiment of the present application are for the distance r k With Doppler frequency f v Two forms of 2D steering vectors can be constructed:

[0134]

[0135] in, represents the Kronecker product.

[0136] Step S306: perform two-dimensional spectrum estimation using the space-frequency two-dimensional steering vector and the reconstructed echo matrix.

[0137] The embodiment of the present application may adopt the Capon spectrum estimation method, and based on the above two expansion methods, obtain the covariance matrix of the reconstructed signal matrix:

[0138]

[0139] in,* H represents the conjugate transpose.

[0140] In order to ensure the numerical stability of computer calculation when inverting the covariance matrix in Capon spectrum estimation, the embodiment of the present application can regularize the covariance matrix, that is, add a relatively small amount to its main diagonal. Finally, two expanded forms of space-frequency two-dimensional spectrum estimation results can be obtained based on the Capon spectrum estimation algorithm:

[0141]

[0142] The resolutions of the distance dimension and the Doppler dimension of the embodiment of the present application are respectively and times.

[0143] Step S307: Arrange the spectrum estimation results according to the direction and order of the steering vector construction to obtain the ionospheric super-resolution imaging results.

[0144] In the actual implementation process, for example, the embodiment of the present application can use a conventional ionospheric detection system to implement an ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology. For a result of 256 coherent accumulation times, the detection frequency is 4.8MHz, and a 16-bit complementary code is used as a spread spectrum modulation sequence. The original signal sampling rate is 39.0625kHz, and the corresponding original distance resolution is 3.84km. The maximum detection distance gate is configured to be 320. For a complementary code modulated signal with two complementary sequences, it means that its single detection period is 16.384ms, that is, its Doppler observation range is plus or minus 30.5Hz, and 256 detections mean that its Doppler resolution is approximately 0.24Hz.

[0145] Whether it is the distance resolution of 3.84km or the Doppler resolution of 0.24Hz, for the ionosphere with fine structure and slow motion characteristics, the resolution is not enough to meet the requirements of fine measurement. Figure 4aAs shown in the figure, a typical measured time domain echo map of the Es layer shows that the virtual height of the Es layer is distributed within the range of 110-120 km, and its echo trace is diffuse, making it difficult to identify the multi-layer structure. After using the conventional method to obtain the range-Doppler imaging results, as shown in Figure 4b As shown, it can be found that its echo structure is difficult to clearly distinguish, and its Doppler is difficult to accurately measure; and the method of the embodiment of the present application is used to estimate the space-frequency two-dimensional spectrum, the sub-matrix is ​​32×32, that is, P=Q=32, a total of 150 sub-matrices are taken, and the reconstruction matrix is ​​expanded in the form of row vectors, and 0.001 is loaded on the diagonal of the covariance matrix to achieve regularization, as shown Figure 4c As shown in the figure, when the range resolution and Doppler resolution are increased by 10 times to 0.384 km and 0.024 Hz respectively, the two layers of Es echo can be clearly distinguished in the range-Doppler imaging diagram, and their virtual heights can be accurately measured to be 114.432 km and 122.88 km respectively, and the corresponding Dopplers are -0.179 Hz and 0.203 Hz respectively. The fine structure and motion characteristics of the ionosphere can be effectively identified. The improvement of range resolution does not require changes in hardware performance and detection parameters, while the improvement of Doppler resolution does not require an increase in the number of coherent detections.

[0146] In the embodiments of the present application, Figure 5 As shown, when the reconstruction matrix is ​​expanded in column vector form while other parameters remain unchanged, the same result can be obtained. This also shows that the distance domain component and Doppler domain component of the guidance quality of the two expansion methods are consistent, and the imaging methods of the two expansion methods are equivalent.

[0147] In the embodiments of the present application, Figure 6a Taking the sub-matrix as 20×20, that is, P=Q=20, and keeping other parameters unchanged, it can be found that its imaging effect reflects the distance and Doppler distribution range of the Es layer, but it cannot distinguish the echoes of the two layers. At the same time, due to the small order of its sub-matrix, its calculation time of 0.39s is relatively Figure 4c The 2.04s is shorter. Figure 6b As shown, if the sub-matrix is ​​50×50, that is, P=Q=50, the two-layer structure in the imaging result is more obvious, the boundary is clearer, and the imaging effect is better, but it takes longer, about 46.14 seconds.

[0148] It should be noted that the calculation time here can be regarded as a reference for the calculation complexity, which is limited to the computer configuration used in the experiment. The calculation time in different scenarios is determined by the actual computer hardware performance and system resource allocation.

[0149] In summary, the embodiments of the present application have the following technical effects:

[0150] The embodiment of the present application does not require changing the hardware indicators and detection parameters of the ionospheric detection system, and can simultaneously utilize the coherence between the frequencies of the detection echoes and the coherence of the echo signals between multiple detections of the same frequency component, thereby simultaneously realizing high-resolution spectral estimation in the distance dimension and the Doppler dimension.

[0151] The embodiments of the present application can simultaneously and equally improve the range dimension and Doppler dimension resolution of ionospheric detection, thereby improving the detection accuracy in the two dimensions equally.

[0152] The embodiment of the present application can balance the imaging effect and the operation time by flexibly adjusting the shape and size of the sub-matrix in the matrix reconstruction.

[0153] According to the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology proposed in the embodiment of the present application, the preset spread spectrum modulation mode and the preset echo sampling frequency can be used to perform ionospheric detection to obtain the echo signal of each detection, and the echo signal of each detection is transformed into the frequency domain, and the transformed echo signals are arranged according to the number of detections to generate an echo matrix, thereby performing interception and reconstruction of the echo matrix to obtain a reconstructed echo matrix, and then constructing a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and using the reconstructed echo matrix and the two-dimensional steering vector to perform two-dimensional spectrum estimation to obtain a spectrum estimation result; the spectrum estimation results are arranged according to the construction direction and order of the steering vector to obtain an ionospheric super-resolution imaging result, and by simultaneously utilizing the coherence between the frequencies of the detection echoes and the coherence of the echo signals between multiple detections of the same frequency component, high-resolution spectrum estimation of the distance dimension and the Doppler dimension is achieved at the same time, and the range dimension and Doppler dimension resolution of the ionospheric detection are equally improved, thereby improving the detection accuracy of the two dimensions equally. Thereby, the technical problem in the related art that the single-dimensional spectral estimation method can only act on one of the distance domain or the Doppler domain, and the imaging capability of the distance dimension of the frequency domain energy aggregation combined with the spectral estimation method is weak, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy is solved.

[0154] Next, an ionospheric imaging device based on space-frequency two-dimensional spectrum estimation technology proposed in an embodiment of the present application is described with reference to the accompanying drawings.

[0155] Figure 7 It is a block diagram of an ionospheric imaging device based on space-frequency two-dimensional spectrum estimation technology according to an embodiment of the present application.

[0156] like Figure 7 As shown, the ionospheric imaging device 10 based on the space-frequency two-dimensional spectrum estimation technology includes: a detection module 100, a reconstruction module 200, an estimation module 300 and an imaging module 400.

[0157] Specifically, the detection module 100 is used to perform ionospheric detection using a preset spread spectrum modulation method and a preset echo sampling frequency to obtain an echo signal for each detection.

[0158] The reconstruction module 200 is used to transform the echo signal of each detection into the frequency domain, and arrange the transformed echo signals according to the number of detections to generate an echo matrix, and use the diagonal of the echo matrix to intercept and reconstruct the echo matrix to obtain a reconstructed echo matrix.

[0159] The estimation module 300 is used to construct a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and perform two-dimensional spectrum estimation using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result.

[0160] The imaging module 400 is used to arrange the spectrum estimation results according to the direction and sequence of the steering vector construction to obtain the ionospheric super-resolution imaging results.

[0161] Optionally, in one embodiment of the present application, the preset echo sampling frequency is greater than or equal to a spread spectrum modulation bandwidth of a preset spread spectrum modulation method.

[0162] Optionally, in one embodiment of the present application, the reconstruction module 200 includes: a transformation unit and a first calculation unit.

[0163] The transformation unit is used to transform the echo signal into the frequency domain to obtain a corresponding output sequence, wherein the adjacent frequency interval of the output sequence is less than or equal to the spread spectrum modulation bandwidth.

[0164] The first calculation unit is used to obtain an echo matrix based on the output sequence.

[0165] Optionally, in one embodiment of the present application, the reconstruction module 200 includes: a capture unit and a reconstruction unit.

[0166] The interception unit is used to intercept the echo matrix using the diagonal line and the preset interval to obtain multiple sub-matrices that meet the preset estimation accuracy conditions.

[0167] The reconstruction unit is used to expand the sub-matrix into a vector and arrange and reconstruct the vector to obtain a reconstructed echo matrix.

[0168] Optionally, in one embodiment of the present application, the reconstruction module 200 includes: an adjustment unit.

[0169] The adjusting unit is used to adjust the size of the sub-matrix so that the sub-matrix meets the preset imaging and operation conditions.

[0170] Optionally, in one embodiment of the present application, the estimation module 300 includes: a first construction unit, a second construction unit and a second calculation unit.

[0171] Wherein, the first construction unit is used to construct a distance-oriented vector for distance using the spatial domain sampling rate.

[0172] The second construction unit is used to construct a frequency-oriented vector for the frequency by using the frequency domain sampling rate.

[0173] The second calculation unit is used to obtain a two-dimensional steering vector based on the distance steering vector and the frequency steering vector.

[0174] Optionally, in one embodiment of the present application, the estimation module 300 includes: a third calculation unit, a fourth calculation unit and an estimation unit.

[0175] Wherein, the third calculation unit is used to obtain a first covariance matrix of the reconstructed echo matrix based on the two-dimensional steering vector.

[0176] The fourth computing unit is used to perform regularization processing on the first covariance matrix to obtain a second covariance matrix that meets a preset numerical stability condition.

[0177] an estimation unit, used for performing two-dimensional spectrum estimation on the second covariance matrix to obtain a spectrum estimation result;

[0178] The expression of the spectrum estimation result is:

[0179]

[0180] Among them, F row (k,v) represents the row spectrum estimation result, c row (k,v) represents the row-direction two-dimensional steering vector form, R row represents the first covariance matrix, * H represents the conjugate transpose, N h Indicates the number of range gates after improving the range resolution, M h Indicates the number of Doppler frequency points after improving the Doppler resolution, F col (k,v) represents the column spectrum estimation result, c col (k,v) represents the row-direction two-dimensional steering vector form, R col represents the second covariance matrix.

[0181] It should be noted that the aforementioned explanation of the embodiment of the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology is also applicable to the ionospheric imaging device based on the space-frequency two-dimensional spectrum estimation technology of this embodiment, and will not be repeated here.

[0182] According to the ionospheric imaging device based on the space-frequency two-dimensional spectrum estimation technology proposed in the embodiment of the present application, the preset spread spectrum modulation method and the preset echo sampling frequency can be used to perform ionospheric detection, and the echo signal of each detection can be obtained, and the echo signal of each detection can be transformed into the frequency domain, and the transformed echo signals can be arranged according to the number of detections to generate an echo matrix, so as to perform interception and reconstruction of the echo matrix to obtain a reconstructed echo matrix, and then a two-dimensional steering vector can be constructed according to the spatial domain sampling rate and the frequency domain sampling rate, and the reconstructed echo matrix and the two-dimensional steering vector can be used to perform two-dimensional spectrum estimation to obtain a spectrum estimation result; the spectrum estimation results can be arranged according to the construction direction and order of the steering vector to obtain an ionospheric super-resolution imaging result, and by simultaneously utilizing the coherence between the frequencies of the detection echoes and the coherence of the echo signals between multiple detections of the same frequency component, high-resolution spectrum estimation of the distance dimension and the Doppler dimension can be achieved at the same time, and the resolution of the distance dimension and the Doppler dimension of the ionospheric detection can be equally improved, thereby improving the detection accuracy of the two dimensions equally. Thereby, the technical problem in the related art that the single-dimensional spectral estimation method can only act on one of the distance domain or the Doppler domain, and the imaging capability of the distance dimension of the frequency domain energy aggregation combined with the spectral estimation method is weak, making it difficult to achieve a balance between the detection distance dimension and the detection accuracy is solved.

[0183] Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0184] A memory 801 , a processor 802 , and a computer program stored in the memory 801 and executable on the processor 802 .

[0185] When the processor 802 executes the program, the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology provided in the above embodiment is implemented.

[0186] Furthermore, the electronic device further comprises:

[0187] The communication interface 803 is used for communication between the memory 801 and the processor 802 .

[0188] The memory 801 is used to store computer programs that can be executed on the processor 802 .

[0189] The memory 801 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0190] If the memory 801, the processor 802 and the communication interface 803 are implemented independently, the communication interface 803, the memory 801 and the processor 802 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 8 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0191] Optionally, in a specific implementation, if the memory 801, the processor 802 and the communication interface 803 are integrated on a chip, the memory 801, the processor 802 and the communication interface 803 can communicate with each other through an internal interface.

[0192] The processor 802 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0193] This embodiment also provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology as described above is implemented.

[0194] An embodiment of the present application also provides a computer program product, including a computer program, which, when executed by a processor, implements the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology provided by an embodiment of the present invention.

[0195] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0196] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0197] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0198] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purpose of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or N wirings (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways as necessary and then storing it in a computer memory.

[0199] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0200] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0201] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0202] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology, characterized in that: The following steps are involved: ionosphere detection is performed using a preset spread spectrum modulation mode and a preset echo sampling frequency to obtain an echo signal for each detection; The echo signals of each detection are transformed into the frequency domain, and the transformed echo signals are arranged according to the number of detections to generate an echo matrix, and the echo matrix is ​​intercepted and reconstructed using the diagonal of the echo matrix to obtain a reconstructed echo matrix; Constructing a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate, and performing two-dimensional spectrum estimation using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result; The spectrum estimation results are arranged according to the direction and sequence of the steering vector construction to obtain the ionospheric super-resolution imaging results.

2. The method according to claim 1, characterized in that The preset echo sampling frequency is greater than or equal to the spread spectrum modulation bandwidth of the preset spread spectrum modulation mode.

3. The method according to claim 2, characterized in that The step of transforming the echo signal into the frequency domain and arranging the transformed echo signal according to the number of detections to obtain an echo matrix includes: Transforming the echo signal into the frequency domain to obtain a corresponding output sequence, wherein the adjacent frequency interval of the output sequence is less than or equal to the spread spectrum modulation bandwidth; The echo matrix is ​​obtained based on the output sequence.

4. The method according to claim 1, characterized in that: The method of truncating and reconstructing the echo matrix by using the diagonal of the echo matrix to obtain a reconstructed echo matrix includes: Using the diagonal line and the preset interval to intercept the echo matrix, a plurality of sub-matrices satisfying a preset estimation accuracy condition are obtained; The submatrix is ​​expanded into a vector, and the vector is arranged and reconstructed to obtain the reconstructed echo matrix.

5. The method according to claim 4, characterized in that The method of truncating and reconstructing the echo matrix by using the diagonal of the echo matrix to obtain a reconstructed echo matrix includes: The size of the sub-matrix is ​​adjusted so that the sub-matrix meets preset imaging and operation conditions.

6. The method according to claim 1, characterized in that The step of constructing a two-dimensional steering vector according to the spatial domain sampling rate and the frequency domain sampling rate includes: constructing a range-oriented vector for the distance using the spatial sampling rate; constructing a frequency-oriented vector for the frequency using the frequency domain sampling rate; The two-dimensional steering vector is obtained based on the range steering vector and the frequency steering vector.

7. The method according to claim 1, characterized in that The using the reconstructed echo matrix and the two-dimensional steering vector to perform two-dimensional spectrum estimation to obtain a spectrum estimation result includes: Obtaining a first covariance matrix of the reconstructed echo matrix based on the two-dimensional steering vector; Regularizing the first covariance matrix to obtain a second covariance matrix that satisfies a preset numerical stability condition; Performing two-dimensional spectrum estimation on the second covariance matrix to obtain the spectrum estimation result; Wherein, the expression of the spectrum estimation result is: Among them, F row (k,v) represents the row spectrum estimation result, c row (k,v) represents the row-direction two-dimensional steering vector form, R row represents the first covariance matrix, * H represents the conjugate transpose, N h Indicates the number of range gates after improving the range resolution, M h Indicates the number of Doppler frequency points after improving the Doppler resolution, F col (k,v) represents the column spectrum estimation result, c col (k,v) represents the row-direction two-dimensional steering vector form, R col Denotes the second covariance matrix.

8. An ionospheric imaging device based on space-frequency two-dimensional spectrum estimation technology, characterized in that: include: The detection module is used to perform ionospheric detection using a preset spread spectrum modulation method and a preset echo sampling frequency to obtain an echo signal for each detection; A reconstruction module, used for transforming the echo signal of each detection into the frequency domain, arranging the transformed echo signals according to the number of detections, generating an echo matrix, and intercepting and reconstructing the echo matrix using the diagonal of the echo matrix to obtain a reconstructed echo matrix; An estimation module, used for constructing a two-dimensional steering vector according to a spatial domain sampling rate and a frequency domain sampling rate, and performing a two-dimensional spectrum estimation using the reconstructed echo matrix and the two-dimensional steering vector to obtain a spectrum estimation result; The imaging module is used to arrange the spectrum estimation results according to the direction and sequence of the steering vector construction to obtain ionospheric super-resolution imaging results.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the ionospheric imaging method based on the space-frequency two-dimensional spectrum estimation technology as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the ionospheric imaging method based on space-frequency two-dimensional spectrum estimation technology as described in any one of claims 1 to 7.

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