Land-sea boundary identification matching positioning method and system based on short-wave backscattering swept frequency signals
Through the land-sea boundary recognition method based on short-wave return scattering swept fixed frequency signal, combined with multi-frequency detection and data assimilation technology, the problem of low accuracy of ionospheric characteristics acquisition over the ocean is solved, and high-precision target positioning and land-sea are achieved in the remote area of the sea Demarcation identification improves short-wave radar detection capabilities.
Patent Information
- Application Number
- CN202411194310.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-28
- Publication Date
- 2024-12-27
AI Technical Summary
The prior art is difficult to obtain the ionosphere characteristics over the ocean with high accuracy. Traditional equipment deployment is difficult to be carried out on the ocean and data inversion is unstable, resulting in low accuracy of ionosphere characteristics information, especially in remote sea areas beacon deployment and insufficient detection capabilities.
Using the land-sea boundary recognition method based on short-wave return scattering sweep fixed frequency signal, the return scattering sweep ionization diagram is obtained through technologies such as time cross-border multi-frequency detection and segmented polynomial fitting, and combining the ionosphere model and Kalman filtered data assimilation to achieve High-precision inversion of characteristic parameters of ionosphere over the ocean and short-wave radar target positioning.
It improves the ionosphere perception accuracy over the ocean and the radar target positioning accuracy in the long-sea area, reduces system costs, expands the land-sea boundary line recognition capabilities of the detection area, and is suitable for remote sea areas without special hardware.
Smart Images
Figure CN119199817A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of ionosphere research and application, and particularly relates to a positioning method and system in the field for identifying and matching land and sea boundaries based on shortwave return scattering scanning fixed-frequency signals. Background Art
[0002] Traditional shortwave ionospheric detection mainly includes three methods: vertical detection, oblique detection and backscatter detection. It is the most basic way for shortwave radar detection equipment to obtain ionospheric characteristics. The means of vertical detection and oblique detection of the ionosphere are limited by the size and power of the equipment, making it difficult to deploy them at sea. The equipment is difficult to maintain after being deployed on islands and reefs, so land is the best choice for the deployment of detection stations. The characteristics of the ionosphere over the ocean can currently only be obtained through backscatter detection. Due to technical difficulties such as the single detection method and the instability of data inversion, the accuracy of ionospheric characteristic information extraction is significantly lower than the accuracy of information extraction based on vertical detection and oblique detection. How to obtain the characteristics of the ionosphere over the ocean with high precision is an urgent problem that needs to be solved, and it is crucial to improving the detection capabilities of shortwave radars.
[0003] Currently, active beacons can be used to obtain ionospheric characteristics of ocean areas, but the placement of active beacon sources is limited in actual situations. For example, the feasibility of placing beacon sources in the open sea or in enemy-occupied areas is very low. In this method, the beacon deployment area is limited and the beacon needs to be maintained. Summary of the invention
[0004] The technical problem to be solved by the present invention is to provide a positioning method and system for identifying and matching the land-sea boundary based on shortwave backscattered scanning fixed-frequency signals.
[0005] The present invention adopts the following technical solution: A positioning method based on shortwave return scattering scanning fixed frequency signal land-sea boundary identification and matching, the improvement of which is that it includes the following steps: Step 1: Obtain the measured backscattered fixed-frequency ionization map: Based on time-interleaved multi-frequency detection technology, shortwave full-band scanning and integrated rapid detection is realized; The frequency list of backscatter frequency sweep is selected through the data of shortwave equipment interference measurement. Assuming that the number of frequency lists of shortwave equipment is P and the number of wave positions is M, the frequency is swept first and then the wave positions are changed during operation, that is, all frequencies of each wave position are transmitted according to the wave position sequence before changing to the next wave position, and the backscatter frequency sweep ionization diagram at each wave position is obtained; Based on the acquired backscattered swept-frequency ionogram, select the fixed-frequency detection list fi, i=1,2,…N. During detection, first scan the azimuth and then the frequency. That is, for a certain detection frequency, first complete the detection of each beam and then detect the next frequency, and obtain the backscattered swept-frequency detection ionogram of each wave position and each frequency; Step 2, obtain the oblique ionogram of the land-sea boundary: The return scattered fixed-frequency signals of N frequencies and M wave positions in the same period acquired by detection are used for land and sea identification, and the mode extreme values are clustered and fused according to the ionospheric propagation characteristics, and the corresponding propagation mode group delay, energy, frequency shift and broadening are extracted; According to the identification results of the fixed-frequency data of all wave positions of the same frequency, the geographic information system of the detection range of the shortwave equipment is matched to obtain the distance of the echo group of the land-sea boundary, forming the land-sea clutter boundary point, which is a quasi-oblique frequency sweep point. The echo group distance of the land-sea clutter boundary is obtained by the same method for other frequencies, and then the quasi-oblique frequency sweep point group distance of the land-sea boundary point is obtained; The piecewise polynomial fitting algorithm is used to smooth the data, forming continuous and smooth tracing data at the frequency sweep point, which is similar to the oblique ionogram. Step 3: Jointly invert the oblique ionogram and the backscattered sweep signal to obtain the characteristic parameters of the ionosphere over the ocean: The ionospheric model is used to complete the pattern recognition of the tracing information of the quasi-oblique ionogram, and the perturbation theory linearization processing method is used to invert the quasi-oblique ionogram to obtain the initial profile of the ionospheric electron concentration. The regional ionospheric electron concentration distribution is formed by rasterization processing of the covered area. The Fredholm integral equation solution method and digital three-dimensional ray tracing technology are used to complete the joint inversion of the ionospheric electron concentration profile based on the minimum delay information of the backscattered swept frequency detection, thereby realizing the inversion of the gridded ionospheric electron concentration distribution. Step 4, ionospheric assimilation in the detection area: Based on the ensemble Kalman filter data assimilation method, the ionospheric multi-source data are assimilated by using the oblique return joint inversion results, oblique measurement inversion results and vertical measurement inversion results. Step 5, shortwave radar target positioning: Based on the assimilation results of the ionosphere in the coverage area, a digital three-dimensional ray tracing algorithm is applied to obtain the coordinate variation coefficient of the coverage area and realize the target positioning of the shortwave detection equipment.
[0006] A positioning system based on shortwave return scattering scanning fixed frequency signal land-sea boundary identification and matching, using the above positioning method, its improvement is that it includes: A first acquisition unit is used to acquire a measured backscattered fixed-frequency swept ionogram; The second acquisition unit is used to obtain a quasi-oblique ionogram of the land-sea boundary point; Joint inversion unit, used for joint inversion of oblique ionogram and backscattered sweep signal to obtain characteristic parameters of the ionosphere over the ocean; Assimilation unit, used for detection of regional ionospheric assimilation; Positioning unit, used for shortwave radar target positioning.
[0007] The beneficial effects of the present invention are: The positioning method disclosed by the present invention is based on backscattered scanning and fixed-frequency detection information, uses islands or coastlines in the far sea area as passive beacons to obtain relevant parameters of the ionosphere, improves the perception accuracy of the ionosphere above the ocean, and improves the positioning accuracy of radar targets in the medium and far sea areas. The land and sea clutter echoes in the detection area are obtained according to shortwave backscattered detection equipment. There is no need to specially add hardware processing equipment, and the cost of the radar system will not be increased. The reliability is high, and the land and sea boundaries of the entire detection area can be identified at the same time, and the application range is wide.
[0008] The positioning system disclosed in the present invention utilizes shortwave backscattered swept-frequency detection data to realize land-sea boundary recognition and matching, obtains information such as the distance of the land-sea clutter boundary echo group to form a "quasi-oblique measurement", and performs joint inversion with the backscattered swept-frequency detection data to obtain the characteristic parameters of the ionosphere above the ocean, assimilates the data with the vertical and oblique ionosphere data detected by the detection station, obtains the coordinate transformation coefficient, and realizes high-precision target positioning in the far sea area. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 It is a flow chart of the positioning method disclosed in the present invention; Figure 2 It is a comparison of the ionograms at the land-sea boundary and the oblique survey station; Figure 3 It is a comparison diagram of the joint inversion results. DETAILED DESCRIPTION
[0010] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0011] The existing shortwave equipment mainly obtains ionospheric characteristics through vertical measurement, oblique measurement and backscatter detection. Due to the characteristics of vertical measurement and oblique measurement detection equipment, it is impossible to deploy detection equipment on the ocean, and the accuracy of ionospheric characteristics obtained by backscatter detection is limited.
[0012] Example 1: Based on the above problems, this example discloses a positioning method based on the identification and matching of land-sea boundary by shortwave return scattered frequency-scanning fixed-frequency signals. It proposes to use islands or coastlines in the far sea area as passive beacons to obtain relevant parameters of the ionosphere, and to perform joint inversion with the return scattered frequency-scanning signals, and then assimilate with the equipment's ionosphere vertical and oblique detection data to construct the ionosphere in the detection area with high precision, thus achieving high-precision target positioning in the far sea area by shortwave radar. Figure 1As shown, the following steps are included: Step 1: Obtain the measured backscattered fixed-frequency ionization map: Based on the time-crossing multi-frequency detection technology, the shortwave full-band (5-28MHz) scanning integrated rapid detection is realized. The multi-frequency detection technology based on time crossing means that the transmitting device transmits multiple working frequencies in one pulse repetition period, and returns to the initial working frequency in the next pulse repetition period, and maintains the coherence characteristics of different detection pulses of the same frequency; The frequency list of backscatter frequency sweep is selected through the data of shortwave equipment interference measurement. Assuming that the number of frequency lists of shortwave equipment is P and the number of wave positions is M, the frequency is swept first and then the wave positions are changed during operation, that is, all frequencies of each wave position are transmitted according to the wave position sequence before changing to the next wave position, and the backscatter frequency sweep ionization diagram at each wave position is obtained; Based on the acquired backscattered swept-frequency ionogram, select the fixed-frequency detection list fi, i=1,2,…N. During detection, first scan the azimuth and then the frequency. That is, for a certain detection frequency, first complete the detection of each beam and then detect the next frequency, and obtain the backscattered swept-frequency detection ionogram of each wave position and each frequency; Step 2, obtain the oblique ionogram of the land-sea boundary: The return scattered fixed-frequency signals of N frequencies and M wave positions in the same period acquired by detection are used for land and sea identification, and the important mode extreme values are clustered and fused according to the ionospheric propagation characteristics, and the corresponding propagation mode group delay, energy, frequency shift, broadening and other characteristic information are extracted; According to the identification results of the fixed-frequency data of all wave positions of the same frequency, the geographic information system of the detection range of the shortwave equipment is matched to obtain the distance of the echo group of the land-sea boundary, and form the land-sea clutter boundary point, which is a quasi-oblique frequency sweep point. The echo group distance of the land-sea clutter boundary is obtained by the same method for other frequencies, and then the distance of the quasi-oblique frequency sweep point group of the land-sea boundary point is obtained; The acquired oblique frequency sweep points are "discrete" in frequency and have fluctuations (not smooth) in trend. The piecewise polynomial fitting algorithm is used to smooth the data to form continuous and smooth tracing data on the sweep points, which is the oblique ionogram. Step 3: Jointly invert the oblique ionogram and the backscattered sweep signal to obtain the characteristic parameters of the ionosphere over the ocean: Based on the identification results of the land-sea boundary obtained by multi-frequency detection, the "quasi-oblique measurement" swept-frequency detection ionogram information is formed, and the ionospheric model is used to complete the pattern recognition of the quasi-oblique measurement ionogram tracing information. The perturbation theory linearization processing method is used to invert the quasi-oblique measurement swept-frequency detection ionogram to obtain the initial ionospheric electron concentration profile; through the rasterization processing of the covered area, the regional ionospheric electron concentration distribution is formed, and the Fredholm integral equation solution method and digital three-dimensional ray tracing technology are used to complete the joint inversion of the ionospheric electron concentration profile based on the minimum delay information of the backscattered swept-frequency detection, thereby realizing the inversion of parameters such as the gridded ionospheric electron concentration distribution; Step 4, ionospheric assimilation in the detection area: The ionospheric oblique and vertical detection data obtained by the land-based detection stations are assimilated with the ionospheric characteristic parameters obtained by joint inversion to obtain more accurate ionospheric characteristics of the coverage area, especially over the ocean. Based on the Ensemble Kalman Filter (EnKF) data assimilation method, the ionospheric multi-source data are assimilated with the oblique return joint inversion results, oblique measurement inversion results and vertical measurement inversion results; the ionospheric data assimilation technology is used to realize the three-dimensional spatial distribution of ionospheric electron concentration from point to surface and volume in the coverage area of short-wave target detection equipment; Step 5, shortwave radar target positioning: Based on the assimilation results of the ionosphere in the coverage area, a digital three-dimensional ray tracing algorithm is applied to obtain the coordinate variation coefficient of the coverage area and realize the target positioning of the shortwave detection equipment.
[0013] Figure 2 This is a comparison of the ionograms at the land-sea boundary and the oblique survey station (the ground distance between the land-sea boundary and the oblique survey station differs by 1 km). Figure 3 It is a comparison chart of the joint inversion results (beam inversion results and certain measured data).
[0014] This embodiment also discloses a positioning system based on shortwave return scattering scanning fixed frequency signal land-sea boundary identification and matching, using the above positioning method, including: A first acquisition unit is used to acquire a measured backscattered fixed-frequency swept ionogram; The second acquisition unit is used to obtain a quasi-oblique ionogram of the land-sea boundary point; Joint inversion unit, used for joint inversion of oblique ionogram and backscattered sweep signal to obtain characteristic parameters of the ionosphere over the ocean; Assimilation unit, used for detection of regional ionospheric assimilation; Positioning unit, used for shortwave radar target positioning.
Claims
1. A positioning method based on shortwave return scattering scanning fixed frequency signal land-sea boundary identification and matching, characterized in that: The steps include: Step 1: Obtain the measured backscattered fixed-frequency ionization map: Based on time-interleaved multi-frequency detection technology, shortwave full-band scanning and integrated rapid detection is realized; The frequency list of backscatter frequency sweep is selected through the data of shortwave equipment interference measurement. Assuming that the number of frequency lists of shortwave equipment is P and the number of wave positions is M, the frequency is swept first and then the wave positions are changed during operation, that is, all frequencies of each wave position are transmitted according to the wave position sequence before changing to the next wave position, and the backscatter frequency sweep ionization diagram at each wave position is obtained; Based on the acquired backscattered swept-frequency ionogram, select the fixed-frequency detection list fi, i=1,2,…N. During detection, first scan the azimuth and then the frequency. That is, for a certain detection frequency, first complete the detection of each beam and then detect the next frequency, and obtain the backscattered swept-frequency detection ionogram of each wave position and each frequency; Step 2, obtain the oblique ionogram of the land-sea boundary: The return scattered fixed-frequency signals of N frequencies and M wave positions in the same period acquired by detection are used for land and sea identification, and the mode extreme values are clustered and fused according to the ionospheric propagation characteristics, and the corresponding propagation mode group delay, energy, frequency shift and broadening are extracted; According to the identification results of the fixed-frequency data of all wave positions of the same frequency, the geographic information system of the detection range of the shortwave equipment is matched to obtain the distance of the echo group of the land-sea boundary, forming the land-sea clutter boundary point, which is a quasi-oblique frequency sweep point. The echo group distance of the land-sea clutter boundary is obtained by the same method for other frequencies, and then the quasi-oblique frequency sweep point group distance of the land-sea boundary point is obtained; The piecewise polynomial fitting algorithm is used to smooth the data, forming continuous and smooth tracing data at the frequency sweep point, which is similar to the oblique ionogram. Step 3: Jointly invert the oblique ionogram and the backscattered sweep signal to obtain the characteristic parameters of the ionosphere over the ocean: The ionospheric model is used to complete the pattern recognition of the tracing information of the quasi-oblique ionogram, and the perturbation theory linearization processing method is used to invert the quasi-oblique ionogram to obtain the initial profile of the ionospheric electron concentration. The regional ionospheric electron concentration distribution is formed by rasterization processing of the covered area. The Fredholm integral equation solution method and digital three-dimensional ray tracing technology are used to complete the joint inversion of the ionospheric electron concentration profile based on the minimum delay information of the backscattered swept frequency detection, thereby realizing the inversion of the gridded ionospheric electron concentration distribution. Step 4, ionospheric assimilation in the detection area: Based on the ensemble Kalman filter data assimilation method, the ionospheric multi-source data are assimilated by using the oblique return joint inversion results, oblique measurement inversion results and vertical measurement inversion results. Step 5, shortwave radar target positioning: Based on the assimilation results of the ionosphere in the coverage area, a digital three-dimensional ray tracing algorithm is applied to obtain the coordinate variation coefficient of the coverage area and realize the target positioning of the shortwave detection equipment.
2. A positioning system based on shortwave backscatter scanning fixed frequency signal land-sea boundary identification and matching, using the positioning method described in claim 1, characterized in that: include: A first acquisition unit is used to acquire a measured backscattered fixed-frequency swept ionogram; The second acquisition unit is used to obtain a quasi-oblique ionogram of the land-sea boundary point; Joint inversion unit, used for joint inversion of oblique ionogram and backscattered sweep signal to obtain characteristic parameters of the ionosphere over the ocean; Assimilation unit, used for detection of regional ionospheric assimilation; Positioning unit, used for shortwave radar target positioning.