Ionospheric parameter inversion method and system based on short-wave time difference information

Abstract

The application discloses an ionospheric parameter inversion method and system based on short-wave time difference information. A plurality of near-distance receiving stations are used to form a receiving station cluster, so that the reflection area of the short-wave propagation path corresponding to each receiving station in the ionosphere is approximately a common ionospheric reflection area, and a same set of F2 layer parameters is used to describe the ionospheric state of the area. The application obtains the observation time difference of each receiving station relative to a reference receiving station, performs ray tracing forward in a candidate parameter space to obtain the theoretical group path of each receiving station and calculate the theoretical time difference, searches for optimal ionospheric parameters by taking the error minimization of the observation time difference and the theoretical time difference as a criterion, and realizes the inversion of the F2 layer critical frequency, the peak height and the half thickness of the common ionospheric reflection area. The application uses the relative time difference between the receiving stations to replace the absolute propagation time delay for inversion, eliminates the influence of non-ionospheric factors such as the unknown transmission time, system delay and receiver clock difference, and improves the inversion precision and reliability.

Description

Technical Field

[0001] This invention belongs to the field of radio propagation, ionospheric detection and shortwave communication environment inversion technology, specifically relating to a method and system for ionospheric parameter inversion based on shortwave time difference information. Background Technology

[0002] When shortwave signals propagate in the ionosphere, their propagation path, group path, and time of arrival are closely related to the ionospheric electron density distribution. Parameters such as the F2 layer critical frequency, peak height, and half-layer thickness affect the refraction characteristics, reflection height, and propagation distance of shortwave signals. Therefore, retrieving ionospheric parameters from shortwave propagation observation information is an important aspect of ionospheric detection, shortwave communication frequency management, and radio propagation environment assessment.

[0003] Existing ionospheric parameter inversion methods typically rely on information such as vertical ionographs, oblique ionographs, absolute group paths, or absolute propagation delays. In actual shortwave propagation environments, absolute propagation delays can be affected by factors such as unknown transmission times, system delays at the transmitter and receiver, receiver clock deviations, and propagation mode aliasing. This makes ionospheric parameter inversion results based on single-station absolute arrival times susceptible to interference from non-ionospheric factors. Summary of the Invention

[0004] To address the problem that the absolute propagation delay in existing ionospheric parameter inversion methods is easily affected by factors such as unknown transmission time, system delay, and receiver clock error, this invention provides an ionospheric parameter inversion method based on shortwave time difference information. By constructing a matching relationship between the observation time difference between nearby receiving stations and the theoretical time difference of ray tracing, the parameters of the F2 layer in the common ionospheric reflection region can be inverted.

[0005] According to one aspect of the present invention, a method for ionospheric parameter inversion based on shortwave time difference information is provided, comprising: acquiring location information of a shortwave transmitting station and location information of multiple receiving stations, wherein the multiple receiving stations constitute a cluster of close-range receiving stations; acquiring the arrival time of the same shortwave signal received by each receiving station, and using one of the receiving stations as a reference receiving station to construct the observation time difference of the remaining receiving stations relative to the reference receiving station; establishing a parameterized ionospheric model for describing the common ionospheric reflection region corresponding to the cluster of close-range receiving stations, and selecting the critical frequency of the F2 layer, the peak height of the F2 layer, and the half-thickness of the F2 layer as the ionospheric parameters to be inverted, and setting... A candidate parameter search space is established; any set of candidate ionospheric parameters is selected within the candidate parameter search space; based on the operating frequency of the shortwave signal and the great circle distance between each receiving station and the transmitting station, ray tracing forward modeling is performed to obtain the theoretical group path from the transmitting station to each receiving station; the theoretical time difference corresponding to each receiving station is calculated based on the difference between the theoretical group path of each receiving station and the theoretical group path of the reference receiving station; a time difference error objective function is constructed based on the observed time difference and the theoretical time difference; candidate ionospheric parameters that minimize the time difference error objective function are searched within the candidate parameter search space and used as the ionospheric parameter inversion result.

[0006] As a further technical solution, the spatial distance between any two receiving stations in the cluster of nearby receiving stations is less than a preset distance threshold, so that the reflection area of ​​the shortwave propagation path corresponding to each receiving station in the ionosphere is approximately the common ionospheric reflection area, and the theoretical group path corresponding to each receiving station is calculated using the same set of candidate ionospheric parameters.

[0007] As a further technical solution, the candidate parameter search space is composed of the lower and upper limits of the critical frequency of the F2 layer, the lower and upper limits of the peak height of the F2 layer, and the lower and upper limits of the half thickness of the F2 layer.

[0008] As a further technical solution, when performing ray tracing forward modeling, a launch elevation angle is selected within a preset launch elevation angle range, and the ground distance and group path of the landing point corresponding to the ray are calculated; when the difference between the ground distance of the landing point and the great circle distance is less than or equal to a preset distance error threshold, the ray is determined to be an reachable ray that can reach the corresponding receiving station.

[0009] As a further technical solution, when multiple reachable rays correspond to the same receiving station, the group path corresponding to the reachable ray with the smallest group path is selected as the theoretical group path of that receiving station.

[0010] As a further technical solution, the objective function for time difference error is the sum of the absolute errors between the observed time difference and the theoretical time difference of each receiving station.

[0011] As a further technical solution, when the parameterized ionosphere model is a quasi-parabolic ionosphere model, the distribution of electron density in the F2 layer along the radial direction is determined based on the peak electron density, the radial distance corresponding to the peak height of the F2 layer, the half thickness of the F2 layer, and the radial distance to the bottom of the F2 layer.

[0012] According to one aspect of the present invention, an ionospheric parameter inversion system based on shortwave time difference information is provided, comprising: a location acquisition module for acquiring location information of a shortwave transmitting station and location information of multiple receiving stations, wherein the multiple receiving stations constitute a cluster of nearby receiving stations; a time difference extraction module for acquiring the arrival time of the same shortwave signal received by each receiving station, and constructing the observation time difference of the remaining receiving stations relative to the reference receiving station, using one of the receiving stations as a reference receiving station; and a model building module for building a parameterized ionospheric model for describing the common ionospheric reflection region corresponding to the cluster of nearby receiving stations, and selecting the F2 layer critical frequency, F2 layer peak height, and F2 layer half-thickness as ionospheric parameters to be inverted, and setting candidate parameters. The system comprises: a parameter search space; a forward modeling module, used to select any set of candidate ionospheric parameters within the candidate parameter search space, and perform ray tracing forward modeling based on the operating frequency of the shortwave signal and the great circle distance between each receiving station and the transmitting station to obtain the theoretical group path from the transmitting station to each receiving station; a time difference calculation module, used to calculate the theoretical time difference corresponding to each receiving station based on the difference between the theoretical group path of each receiving station and the theoretical group path of the reference receiving station; an objective function construction module, used to construct a time difference error objective function based on the observed time difference and the theoretical time difference; and a parameter search module, used to search for candidate ionospheric parameters within the candidate parameter search space that minimize the time difference error objective function, as the ionospheric parameter inversion result.

[0013] According to one aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the ionospheric parameter inversion method based on shortwave time difference information.

[0014] According to one aspect of the present invention, an electronic device is provided, comprising: one or more processors; and a storage device for storing one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement the ionospheric parameter inversion method based on shortwave time difference information.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention uses the time difference of arrival between nearby receiving stations to invert ionospheric parameters, which does not directly rely on the absolute propagation delay of a single station, thus reducing the impact of unknown launch time and common system delay on the inversion results; (2) The present invention utilizes the spatial correlation of the propagation paths of clusters of nearby receiving stations to approximate the propagation paths of multiple receiving stations as being controlled by the same local ionospheric reflection region, and uses the same set of ionospheric parameters to describe the ionospheric state of the region. (3) This invention calculates the theoretical group path under different candidate ionospheric parameters by ray tracing forward modeling, and obtains the theoretical time difference from the theoretical group path difference, thus transforming the ionospheric parameter inversion problem into the problem of minimizing the error between the observation time difference and the theoretical time difference; (4) This invention can be used to invert parameters such as the critical frequency of the F2 layer, the peak height of the F2 layer, and the half thickness of the F2 layer, and can be extended to multi-frequency or multi-time joint inversion. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating an ionospheric parameter inversion method based on shortwave time difference information provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the geometric relationship between the shortwave transmitting station, the common ionospheric reflection region, and the cluster of nearby receiving stations in an embodiment of the present invention. Figure 3 This is an oblique ionization map obtained based on analytical ray tracing under representative QP parameters in an embodiment of the present invention; Figure 4 This is a profile of the objective function corresponding to three ionospheric parameters in a representative case of this invention. Figure 5 This is a verification diagram showing the consistency between the set values ​​and the inverted values ​​of ionospheric parameters under multiple simulation conditions in the embodiments of the present invention. Detailed Implementation

[0018] It should be noted that:

[0019] For multiple spatially close receiving stations, when they receive the same shortwave signal, the propagation paths of each station typically exhibit strong spatial correlation near the ionospheric reflection region. When the distance between the receiving stations meets certain conditions, the propagation paths corresponding to multiple receiving stations can be approximated as being controlled by the same local ionospheric reflection region. In this case, the time difference of arrival between the receiving stations can reflect the differences between different propagation path groups and can be used to construct constraints for ionospheric parameter inversion. Therefore, this invention provides a method for ionospheric parameter inversion using time difference information between nearby receiving stations to reduce the impact of factors such as absolute propagation delay and unknown transmission time on the inversion results.

[0020] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be decomposed, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0023] This invention provides a method for ionospheric parameter inversion based on shortwave time difference information. By constructing a matching relationship between the observed time difference and the theoretical time difference, it achieves the inversion of parameters in the common ionospheric reflection region. Figure 1 As shown, it includes the following steps:

[0024] Step 1: Obtain the coordinates of the transmitting station and multiple nearby receiving stations.

[0025] This step involves obtaining the shortwave transmitting station. Location information, multiple receiving stations The location information is used to calculate the shortwave transmitting station. to each receiving station Great circle distance ,in The multiple receiving stations constitute a cluster of near-field receiving stations.

[0026] Specifically, the launch station is calculated based on the latitude and longitude of the launch station and each receiving station. to each receiving station Great circle distance express: , in, For the Earth's radius, and They are shortwave transmission stations latitude and longitude and The first One receiving station The latitude and longitude are calculated in radians.

[0027] The cluster of nearby receiving stations satisfies the condition that the spatial distance between multiple receiving stations is less than a preset distance threshold (e.g., within 200 kilometers), so that the reflection area of ​​the shortwave propagation path corresponding to multiple receiving stations in the ionosphere is approximately a common reflection area, and the ionospheric state of the common reflection area is described by the same set of ionospheric parameters.

[0028] Step 2: Extract the arrival time of the same signal received by each receiving station.

[0029] This step obtains information from each receiving station. Arrival time of receiving the same shortwave signal And using one of the receiving stations as the reference receiving station, the observation time difference of the other receiving stations relative to the reference receiving station is constructed.

[0030] Specifically, with the first receiving station As a reference receiving station, the observation time difference of the other receiving stations relative to the reference receiving station is: , in, For the first One receiving station Relative to the reference receiving station The observation time difference For the first One receiving station The arrival time of receiving the same shortwave signal For reference receiving station The arrival time of the received shortwave signal.

[0031] Step 3: Construct a parameterized ionospheric model and a candidate parameter search space.

[0032] This step establishes a parameterized ionospheric model to describe the common ionospheric reflection region corresponding to the cluster of nearby receiving stations. The critical frequency of the F2 layer, the peak height of the F2 layer, and the half thickness of the F2 layer are selected as the ionospheric parameters to be inverted, and a candidate parameter search space is set.

[0033] In step 3, the parameterized ionosphere model adopts a quasi-parabolic ionosphere model. A set of candidate ionosphere parameters. Recorded as: , in This is the critical frequency for layer F2. This represents the peak height of the F2 layer. The thickness is half of F2 layer.

[0034] The parameterized ionosphere model described in this invention is not limited to the quasi-parabolic ionosphere model, but also includes any one of the Chapman model, IRI parameterized model, etc.

[0035] In the aforementioned quasi-parabolic ionosphere model, the radial distribution of the electron density in the F2 layer is expressed as follows: , in, The peak value of electron density. The radial distance is measured from the Earth's center. This represents the radial distance corresponding to the peak height of layer F2. For F2 layer half thickness, This is the radial distance from the bottom of layer F2.

[0036] The candidate parameter search space Represented as: , in, and These are the lower and upper limits for the critical frequency search in layer F2, respectively. and These are the lower and upper limits for searching the peak height of layer F2, respectively. and These are the lower and upper limits for the half-thickness search of layer F2, respectively.

[0037] Step 4, ray tracing forward modeling.

[0038] This step involves the search space for candidate parameters. Any set of candidate ionospheric parameters Based on operating frequency Distance from the Great Circle Ray tracing forward modeling is performed within a preset emission elevation angle range (e.g., 5° to 60°) to obtain the shortwave transmission station. to each receiving station Theoretical group path The difference between the ground distance of the landing point and the great circle distance of the station in the ray tracing results is used to determine whether the ray has reached the corresponding receiving station, and the ray that meets the reachability condition is identified as a reachable ray; when the same receiving station corresponds to multiple reachable rays, the theoretical group path corresponding to the receiving station is determined according to the preset mode selection criteria.

[0039] In step 4, for any set of candidate ionospheric parameters Operating frequency Distance from the Great Circle Select the launch elevation angle within the preset elevation angle range. Ray tracing forward modeling is performed based on a parameterized ionospheric model. For each emission elevation angle β, the ground distance of the corresponding ray's landing point is calculated. Group path .

[0040] Distance from the ground at the landing point Distance from the great circle Between satisfy At that time, the ray was determined to have reached the first... One receiving station The reachable rays, among which, Set a preset distance error threshold (e.g., within 2 kilometers).

[0041] When the One receiving station When multiple reachable rays are involved, the theoretical group path corresponding to the receiving station is determined according to a preset mode selection criterion. In one implementation, the ray pattern with the smallest group path among multiple reachable rays is selected as the theoretical group path corresponding to the receiving station: , in, For the i-th receiving station The group path of the corresponding k-th reachable ray.

[0042] Step 5: Calculate the theoretical time difference.

[0043] This step uses the theoretical group path corresponding to the reference receiving station as a benchmark, and calculates the theoretical time difference based on the difference between the theoretical group paths corresponding to the other receiving stations and the theoretical group path of the reference receiving station.

[0044] In step 5, the first receiving station As a reference receiving station, the theoretical time difference is calculated using the following formula: , in, For the first One receiving station Relative to the reference receiving station Theoretical time difference, For shortwave transmission station up to the first Receiving station Theoretical group path, For shortwave transmission station To the reference receiving station Theoretical group path, This refers to the speed of radio wave propagation.

[0045] Step 6: Construct the objective function for time difference error based on the observed time difference and the theoretical time difference.

[0046] In one implementation, the objective function for the time difference error is the sum of the absolute errors between the observed time difference and the theoretical time difference: , in, Candidate ionospheric parameters The corresponding objective function value for time difference error.

[0047] Step 7: Match the observed time difference with the theoretical time difference to invert the ionospheric parameters.

[0048] Search space for candidate ionospheric parameters The parameters are searched internally, and candidate ionospheric parameters that minimize the objective function of time difference error are selected as the ionospheric parameter inversion results.

[0049] Specifically, in the candidate ionospheric parameter search space Inner candidate ionosphere parameters Perform a search and record candidate parameter combinations that minimize the objective function: , in, This represents the optimal combination of ionospheric parameters obtained through inversion.

[0050] The optimal combination of ionospheric parameters is expressed as follows: , in, The critical frequency of the F2 layer obtained by inversion. The peak height of layer F2 obtained by inversion, The half-thickness of F2 layer obtained by inversion.

[0051] As a preferred embodiment, this embodiment uses a station geometry consisting of one shortwave transmitting station and four near-field receiving stations to illustrate the method of the present invention.

[0052] Among them, shortwave transmission station Let's call it City B, with its latitude and longitude as follows: The four receiving stations are located in City W, City J, City X, and City S of Province A, denoted as... Among them, the W city station serves as a reference receiving station. The latitude and longitude coordinates of each receiving station are as follows: , The operating frequency of the shortwave signal is set to: MHz.

[0053] The four receiving stations are located in the same area, forming a cluster of close-range receiving stations. Under this condition, the reflection regions of the shortwave propagation paths corresponding to the four receiving stations in the ionosphere are approximated as common reflection regions, and the same set of ionospheric parameters are used to describe the ionospheric state of this region.

[0054] (1) Calculate the latitude and longitude of the launching station and each receiving station. to each receiving station propagation distance In this embodiment, based on the above formula, the approximate great circle distances from the B city station to the four receiving stations can be obtained as follows: , The aforementioned distance is used in subsequent ray tracing forward modeling to determine whether the ray has reached the corresponding receiving station.

[0055] (2) In this embodiment, a QP parameterized ionosphere model is established. The parameters to be inverted are: .

[0056] In this embodiment, to verify the inversion capability of the method under different ionospheric parameter conditions, multiple sets of QP parameters were set as simulation parameters. The parameters are shown in Table 1.

[0057] Table 1. Multiple QP Ionospheric Setting Parameters .

[0058] In practical applications, the above parameters are unknown and need to be obtained by inversion from the observation time difference; in this embodiment, the above parameters are only used to generate simulated observation data to verify the feasibility of the inversion method.

[0059] (3) Obtain the oblique ionization map by analytical ray tracing using the QP model. For each set of parameters, analytical ray tracing is performed at different operating frequencies and different emission elevation angles within a given frequency range to calculate the ground distance and group path of the corresponding ray. When the difference between the ground distance of the landing point and the propagation distance of the corresponding receiving station is less than 2 km, the ray is identified as an reachable ray, and the group path at that frequency is recorded. The group path points that meet the reachability conditions at different frequencies are arranged by frequency to obtain the oblique ionization map of the corresponding propagation path. To illustrate the source of the group path forward modeling data, this embodiment selects representative case S3 to generate the oblique ionization map, and its QP parameters are set as follows: , The operating frequency is: =8.0MHz.

[0060] Figure 3 Used to demonstrate the frequency-group path relationship obtained from analytical ray tracing forward modeling; in the actual parameter search process, for each candidate parameter, the theoretical group path of each path at the working frequency is directly calculated, and the theoretical time difference is constructed accordingly.

[0061] (4) Construct the simulated observation time difference, and set the parameters for the m-th group. Analytical ray tracing was performed on four paths: B city station - W city station, B city station - J city station, B city station - X city station, and B city station - S city station, to obtain the group path under set parameters. Taking the W city station as an example... As a reference receiving station, the simulated observation time difference is constructed based on the difference between the paths of each receiving station group and the path of the reference receiving station group.

[0062] (5) This embodiment uses a local search grid with a fixed step size for parameter inversion. To verify the algorithm's local inversion capability under different parameter conditions, a candidate parameter space is constructed in the simulation test using the preset parameter range near each set of parameters; in practical applications, the candidate parameter space can be given by the background ionospheric model, historical experience range, or prior detection results. Specifically, in this embodiment... The search range is 2.0 MHz above and below the preset center value. The search range is 40.0 km above and below the preset center value. The search range is 20.0 km above and below the preset center value. The search steps are 0.021 MHz, 2.0 km, and 1.0 km.

[0063] (6) Search for the optimal ionospheric parameters by traversing all parameter combinations in the candidate parameter space. For each set of candidate parameters, repeatedly perform theoretical group path calculation, theoretical time difference calculation, and objective function calculation. Record the candidate parameter combinations that minimize the objective function, and then obtain the inverted optimal ionospheric parameters. Figure 4 The objective function profiles for the three parameter directions (foF2), (hmF2), and (ymF2) in the representative case S3 are given. Figure 4 It can be seen that the objective function has a significant minimum region within the candidate parameter space. It should be noted that due to parameter coupling under the single-frequency time difference constraint, the minimum point of the objective function may not completely coincide with the set parameters, but the corresponding theoretical time difference can maintain good consistency with the observed time difference. Table 2 presents the time difference matching results for the representative case S3.

[0064] Table 2. Time difference matching results for representative case S3 .

[0065] It should be noted that, under actual observation conditions, the observation time difference is obtained from the arrival time of the same shortwave signal received by each receiving station. In this embodiment, the group path difference under set parameters is used to generate the simulated observation time difference, which is only used to verify the inversion process.

[0066] (7) To further verify the applicability of the method of the present invention under different QP parameter conditions, this embodiment performs inversion tests on 10 sets of set parameters respectively. Figure 5 The comparison results of the set parameters and inversion parameters in 10 sets of tests are presented. The black dashed line in the figure represents the ideal coincidence line (y=x), used to characterize the case where the set value and the inversion value are completely consistent; the blue solid line represents the fitted line obtained by least-squares linear fitting of the scatter points of the set value and the inversion value. Figure 5 It is evident that the inversion results of (foF2) and (hmF2) maintain good linear consistency with the set values ​​overall, while the consistency of (ymF2) is relatively weak, indicating that the half-thickness parameter still exhibits some parameter coupling under single-frequency near-distance time difference conditions. Table 3 presents the inversion test results of multiple sets of QP parameters. As can be seen from Table 3, all 10 test sets obtained valid inversion results, with no invalid solutions or null values ​​caused by unreachable paths. The minimum value of the objective function for each set is mainly around 10. -4The millisecond-level magnitude indicates a good consistency between the theoretical time difference corresponding to the inversion parameters and the simulated observation time difference. Regarding parameter errors, the average absolute errors of (foF2), (hmF2), and (ymF2) in the 10 test groups are approximately 0.234 MHz, 9.467 km, and 9.600 km, respectively. Furthermore, for... Figure 5 The set parameters and inversion parameters were linearly fitted, and the correlation coefficients (R) of (foF2), (hmF2), and (ymF2) were 0.90788, 0.96634, and 0.79192, respectively. Among them, (hmF2) had the highest correlation coefficient, indicating that the peak height parameter had good linear consistency; (foF2) also showed a significant positive correlation; the correlation coefficient of (ymF2) was relatively low, and some groups showed certain deviations, indicating that under the conditions of a single operating frequency and a limited number of receiving stations, different combinations of QP parameters may produce relatively close time differences between receiving stations, and there is a certain compensation relationship between the half-thickness parameter and other parameters. Specifically, the errors of the three parameters of S2 and S10 were relatively small; S3, as a representative case, was achievable through forward modeling, and its hmF2 was located in the high value range of the set range in this embodiment, and its inversion result could reproduce the time difference between receiving stations well; the errors of (ymF2) of S1, S4, and S8 were relatively large. The above phenomena indicate that the test results of this embodiment should not be interpreted as a unique and accurate recovery of all QP parameters, but rather as follows: given the station geometry, operating frequency, and candidate parameter space conditions, the present invention can filter out ionospheric parameter combinations that match the observation time difference by using the inter-station time difference information, thereby effectively constraining the local QP ionospheric parameters.

[0067] Table 3. Results of multiple QP parameter inversion tests .

[0068] This invention also provides an ionospheric parameter inversion system based on shortwave time difference information. This system belongs to the same inventive concept as the above method embodiments. For the contents not described in detail in the system embodiments, please refer to the corresponding descriptions in the method embodiments.

[0069] The system includes: a location acquisition module, a time difference extraction module, a model building module, a forward modeling module, a time difference calculation module, an objective function construction module, and a parameter search module.

[0070] The location acquisition module is used to acquire the location information of the shortwave transmitting station and multiple receiving stations. These receiving stations form a cluster of close-range receiving stations, where the spatial distance between any two stations is less than a preset distance threshold. This ensures that the reflection regions of the shortwave propagation paths of each receiving station in the ionosphere approximate the same common ionospheric reflection region. The location information includes the latitude and longitude coordinates of each station, which can be obtained by the location acquisition module through satellite positioning, map data reading, or manual configuration.

[0071] The time difference extraction module is used to obtain the arrival time of the same shortwave signal received by each receiving station, and constructs the observation time difference of each receiving station relative to the reference receiving station, using one of the receiving stations as a reference receiving station. Specifically, the time difference extraction module detects the arrival time of the same shortwave signal received by each receiving station, subtracts the arrival time of each receiving station from the arrival time of the reference receiving station, and obtains multiple observation time difference values. Because relative time differences are used instead of absolute arrival times, common error terms introduced by unknown transmission time, common system delay, and non-ionospheric factors can be canceled out in the difference calculation.

[0072] The model building module is used to establish a parameterized ionospheric model describing the common ionospheric reflection region corresponding to the near-field receiving station cluster. It selects the F2 layer critical frequency, F2 layer peak height, and F2 layer half-thickness as the ionospheric parameters to be inverted and sets a candidate parameter search space. The candidate parameter search space is jointly composed of the lower and upper search limits for the F2 layer critical frequency, the F2 layer peak height, and the F2 layer half-thickness. The parameterized ionospheric model can be any of the following: a quasi-parabolic ionospheric model, a Chapman model, or an IRI parameterized model.

[0073] The forward modeling module is used to select any set of candidate ionospheric parameters within the candidate parameter search space. Based on the operating frequency of the shortwave signal and the great circle distance between each receiving station and the transmitting station, it performs ray tracing forward modeling to obtain the theoretical group paths from the transmitting station to each receiving station. Specifically, the forward modeling module selects a transmission elevation angle within a preset transmission elevation angle range and calculates the ground distance and group path corresponding to the ray. When the difference between the ground distance and the great circle distance is less than or equal to a preset distance error threshold, the ray is determined as a reachable ray to the corresponding receiving station. When multiple reachable rays correspond to the same receiving station, the group path corresponding to the reachable ray with the smallest group path is selected as the theoretical group path for that receiving station. The theoretical group paths for each receiving station are calculated using the same set of candidate ionospheric parameters.

[0074] The time difference calculation module is used to calculate the theoretical time difference for each receiving station based on the difference between the theoretical group path of each receiving station and the theoretical group path of the reference receiving station. Specifically, the time difference calculation module subtracts the theoretical group path of the reference receiving station from the theoretical group path of each receiving station, and then divides the resulting difference by the radio wave propagation speed to obtain the theoretical time difference value for each receiving station.

[0075] The objective function construction module is used to construct a time difference error objective function based on the observed time difference and the theoretical time difference. In one embodiment, the time difference error objective function is the sum of the absolute errors between the observed time difference and the theoretical time difference at each receiving station. The smaller the value of this objective function, the higher the degree of matching between the theoretical and measured time differences under the current candidate ionospheric parameters.

[0076] The parameter search module is used to search for candidate ionospheric parameters within the candidate parameter search space that minimize the objective function of the time difference error, and output these parameters as the ionospheric parameter inversion result. The parameter search module can employ search strategies such as grid search, genetic algorithms, or particle swarm optimization to perform a global or local search within the candidate parameter space, recording the combination of the F2 layer critical frequency, F2 layer peak height, and F2 layer half-thickness that minimizes the objective function value, and outputting this combination as the final inversion result.

[0077] The collaborative relationship between the modules of the system described in this embodiment is as follows: The location acquisition module provides the station location information to the time difference extraction module (used to determine the signal source and the correspondence between stations) and the forward modeling module (used to calculate the great circle distance). The time difference extraction module outputs the observed time difference to the objective function construction module. The model building module outputs the candidate parameter search space to the forward modeling module. The forward modeling module outputs the theoretical group path to the time difference calculation module. The time difference calculation module outputs the theoretical time difference to the objective function construction module. The objective function construction module outputs the objective function to the parameter search module. The parameter search module uses the objective function value as feedback to control the forward modeling module to continue traversing the next set of candidate parameters until the search is complete, and finally outputs the inversion result.

[0078] It should be noted that the above modules can be integrated into a single processing unit, or each unit can exist as a separate physical entity, or two or more units can be integrated into a single unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0079] For details on the implementation of each module, please refer to the corresponding steps in the method embodiment. For any parts not covered in this system embodiment, please refer to the method embodiment section.

[0080] This invention also provides an electronic device, including: one or more processors; and a storage device for storing one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors implement the ionospheric parameter inversion method based on shortwave time difference information according to any of the aforementioned method embodiments.

[0081] The electronic device also includes a communication interface for communication between the storage device and the processor. The memory may include high-speed RAM, and may also include non-volatile memory, such as at least one disk drive.

[0082] If the memory, processor, and communication interface are implemented independently, they can be interconnected via a bus to communicate with each other. The bus can be an industry-standard architecture bus, an external device interconnect bus, or an extended industry-standard architecture bus, etc. Buses can be categorized as address buses, data buses, control buses, etc.

[0083] Optionally, in a specific implementation, if the memory, processor, and communication interface are integrated on a single chip, then the memory, processor, and communication interface can communicate with each other through an internal interface. The processor can be a central processing unit, a specific integrated circuit, or one or more integrated circuits configured to implement embodiments of the present invention.

[0084] This invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the ionospheric parameter inversion method based on shortwave time difference information according to any of the aforementioned method embodiments.

[0085] The computer-readable storage medium can be any means capable of containing, storing, communicating, propagating, or transmitting a program for use by or in conjunction with an instruction execution system, apparatus, or device. More specific examples of computer-readable storage media include, but are not limited to: an electrical connection (electronic device) having one or more wires, a portable computer disk drive (magnetic device), random access memory, read-only memory, erasable and editable read-only memory, fiber optic device, and portable optical disc read-only memory. The computer-readable storage medium can even be paper or other suitable media on which the program can be printed, as the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0086] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (FPGAs), field-programmable gate arrays (FPGAs), etc.

[0087] In summary, this invention discloses an ionospheric parameter inversion method based on shortwave time difference information. The method acquires the location information of a shortwave transmitting station and multiple nearby receiving stations, and calculates the great circle distance from the transmitting station to each receiving station. It extracts the arrival time of the same shortwave signal received by multiple receiving stations, and uses one of the receiving stations as a reference station to obtain the observation time difference of each receiving station relative to the reference station. It establishes a parameterized ionospheric model corresponding to the common reflection region, and uses the F2 layer critical frequency, F2 layer peak height, and F2 layer half-thickness as inversion parameters. Ray tracing forward modeling is performed within the set parameter range to obtain the theoretical group paths from the transmitting station to each receiving station under different candidate ionospheric parameters. The theoretical time difference is calculated based on the difference between the theoretical group paths of each receiving station and the theoretical group paths of the reference station. The observation time difference is matched with the theoretical time difference, and the ionospheric parameter with the smallest error is determined as the inversion result. This method uses the time difference information between nearby receiving stations to constrain the common ionospheric reflection region, reducing the impact of absolute propagation delay and unknown transmission time on the inversion results. It can be used for local ionospheric parameter inversion under shortwave propagation conditions.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for ionospheric parameter inversion based on shortwave time difference information, characterized in that, include: The location information of the shortwave transmitting station and the location information of multiple receiving stations are obtained, and the multiple receiving stations constitute a cluster of close-range receiving stations; The spatial distance between any two receiving stations in the cluster of nearby receiving stations is less than a preset distance threshold, so that the reflection area of ​​the shortwave propagation path corresponding to each receiving station in the ionosphere is approximately the common ionospheric reflection area, and the theoretical group path corresponding to each receiving station is calculated using the same set of candidate ionospheric parameters. Obtain the arrival time of the same shortwave signal received by each receiving station, and use one of the receiving stations as the reference receiving station to construct the observation time difference of the other receiving stations relative to the reference receiving station; A parameterized ionospheric model is established to describe the common ionospheric reflection region corresponding to the cluster of nearby receiving stations. The critical frequency of the F2 layer, the peak height of the F2 layer, and the half thickness of the F2 layer are selected as the ionospheric parameters to be inverted, and a candidate parameter search space is set. Within the candidate parameter search space, select any set of candidate ionospheric parameters, and based on the operating frequency of the shortwave signal and the great circle distance between each receiving station and the transmitting station, perform ray tracing forward modeling to obtain the theoretical group path from the transmitting station to each receiving station. The theoretical time difference for each receiving station is calculated based on the difference between the theoretical group path of each receiving station and the theoretical group path of the reference receiving station. Construct a time difference error objective function based on the observed time difference and the theoretical time difference; Search within the candidate parameter search space for candidate ionospheric parameters that minimize the objective function of the time difference error, and use these as the ionospheric parameter inversion results.

2. The ionospheric parameter inversion method based on shortwave time difference information according to claim 1, characterized in that, The candidate parameter search space is composed of the lower and upper limits of the critical frequency of the F2 layer, the lower and upper limits of the peak height of the F2 layer, and the lower and upper limits of the half thickness of the F2 layer.

3. The ionospheric parameter inversion method based on shortwave time difference information according to claim 1, characterized in that, When performing ray tracing forward modeling, the emission elevation angle is selected within the preset emission elevation angle range, and the ground distance and group path of the landing point corresponding to the ray are calculated; when the difference between the ground distance of the landing point and the great circle distance is less than or equal to the preset distance error threshold, the ray is determined as a reachable ray to the corresponding receiving station.

4. The ionospheric parameter inversion method based on shortwave time difference information according to claim 3, characterized in that, When multiple reachable rays correspond to the same receiving station, the group path corresponding to the reachable ray with the smallest group path is selected as the theoretical group path of that receiving station.

5. The ionospheric parameter inversion method based on shortwave time difference information according to claim 1, characterized in that, The objective function for time difference error is the sum of the absolute errors between the observed time difference and the theoretical time difference at each receiving station.

6. The ionospheric parameter inversion method based on shortwave time difference information according to claim 1, characterized in that, When the parameterized ionosphere model is a quasi-parabolic ionosphere model, the distribution of electron density in the F2 layer along the radial direction is determined based on the peak electron density, the radial distance corresponding to the peak height of the F2 layer, the half thickness of the F2 layer, and the radial distance to the bottom of the F2 layer.

7. An ionospheric parameter inversion system based on shortwave time difference information, characterized in that, include: The location acquisition module is used to acquire the location information of the shortwave transmitting station and the location information of multiple receiving stations, wherein the multiple receiving stations constitute a cluster of close-range receiving stations; The spatial distance between any two receiving stations in the cluster of nearby receiving stations is less than a preset distance threshold, so that the reflection area of ​​the shortwave propagation path corresponding to each receiving station in the ionosphere is approximately the common ionospheric reflection area, and the theoretical group path corresponding to each receiving station is calculated using the same set of candidate ionospheric parameters. The time difference extraction module is used to obtain the arrival time of the same shortwave signal received by each receiving station, and to construct the observation time difference of the other receiving stations relative to the reference receiving station, using one of the receiving stations as the reference receiving station. The model building module is used to build a parameterized ionospheric model to describe the common ionospheric reflection region corresponding to the near-range receiving station cluster, and selects the critical frequency of the F2 layer, the peak height of the F2 layer, and the half thickness of the F2 layer as the ionospheric parameters to be inverted, and sets the candidate parameter search space. The forward modeling module is used to select any set of candidate ionospheric parameters in the candidate parameter search space, and perform ray tracing forward modeling based on the operating frequency of the shortwave signal and the great circle distance between each receiving station and the transmitting station to obtain the theoretical group path from the transmitting station to each receiving station. The time difference calculation module is used to calculate the theoretical time difference for each receiving station based on the difference between the theoretical group path of each receiving station and the theoretical group path of the reference receiving station. The objective function construction module is used to construct a time difference error objective function based on the observed time difference and the theoretical time difference; The parameter search module is used to search for candidate ionospheric parameters that minimize the objective function of the time difference error within the candidate parameter search space, and use them as the ionospheric parameter inversion result.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the ionospheric parameter inversion method based on shortwave time difference information as described in any one of claims 1 to 6.

9. An electronic device, characterized in that, include: One or more processors; And a storage device for storing one or more programs, which, when executed by the one or more processors, cause the one or more processors to implement the ionospheric parameter inversion method based on shortwave time difference information as described in any one of claims 1 to 6.

Images