Satellite signal simulator ionosphere time delay simulation method and device

Abstract

The application provides a satellite signal simulator ionosphere time delay simulation method and device, adopts an IRI international reference ionosphere model to generate ionosphere time delay data files of a global range in a specified simulation time period in advance, a satellite simulator calculates a piercing point of a satellite through the ionosphere, reads the ionosphere time delay data files, calculates satellite signal ionosphere time delay based on the IRI model, and is used for correction of satellite pseudo-range generated by the satellite simulator, so that positioning capability of a satellite navigation device at any position in the world can be accurately evaluated by a user.

Description

Technical Field

[0001] This invention pertains to satellite navigation technology, specifically to a method and apparatus for simulating ionospheric time delay using a satellite signal simulator. Background Technology

[0002] Satellite navigation signal simulators are the primary equipment used in laboratories to simulate satellite navigation. They provide various testing methods for satellite navigation receivers and systems that rely on satellite navigation. These simulators can model the motion of the carrier and satellite, signal characteristics, atmospheric effects, and other factors, simulating the environment of the satellite navigation receiver on a moving platform. This allows the receiver to actually perform navigation based on the parameters of the test scenario. Currently, with the widespread application of navigation systems and the rapid development of the BeiDou system, satellite navigation signal simulators can simulate satellite signals from BeiDou, GPS, GLONASS, and Galileo systems. Regardless of the system, ionospheric delay is the primary source of atmospheric error in satellite signals. Compared to other error sources, ionospheric delay varies drastically, is unpredictable, and is affected by various factors such as geographical location, time, and solar activity. Furthermore, its value is much larger than other delays, accounting for more than 50% of the total satellite signal delay.

[0003] Currently, the ionospheric delay simulation commonly used by domestic and international satellite signal simulator manufacturers is based on a simple ionospheric model, most typically the Klobuchar model. Satellite simulators provide a parameter input window for the Klobuchar model, allowing users to manually input parameters or use the simulator's default values. The advantages of this ionospheric model are its simple algorithm, intuitively and concisely reflecting the diurnal variation characteristics of the ionosphere. It uses a trigonometric cosine function, requiring only a few hundred lines of code, resulting in high computational efficiency and minimal computer resource consumption. However, its disadvantage is that it cannot accurately represent the impact of the real ionosphere on satellite signals. The ionospheric delay estimated by this model typically accounts for 5%-60% of the actual delay, and in high-latitude regions, especially polar regions, the simulation results only account for 10% of the actual ionospheric delay, sometimes even resulting in unreasonable negative values. Since user receivers typically also use the Klobuchar model for ionospheric correction of pseudorange observations, the positioning error of receivers receiving satellite simulator signals is usually very small, generally on the centimeter level, while the positioning error of receivers receiving actual satellite signals can be as high as 10 meters or even greater. For users who want to evaluate receivers to be closer to their actual positioning accuracy globally, using the Klobuchar model in a satellite signal simulator is not feasible.

[0004] The IRI International Reference Ionospheric Model utilizes observational data from satellites, sounding rockets, and incoherent scattering radar, while also incorporating solar activity, geomagnetic indices, and multiple atmospheric models. Given the year, date, latitude, and longitude, it can provide relatively accurate VTEC data for a specific time and location globally. Users can calculate the ionospheric propagation delay based on the satellite puncture point and signal propagation direction. The IRI model can be applied anywhere in the world, and its accuracy in calculating ionospheric delay is far superior to the Klobuchar model, providing users with a time delay error simulation that approximates the actual ionospheric height. Satellite simulator users can set up their devices in different regions of the Earth to obtain near-realistic positioning errors, facilitating receiver performance evaluation. However, the interface provided by the official IRI ionospheric model requires access to a remote database for calculation, and each calculation takes a long time (for example, IRI-2007 takes about 3.6ms per execution and IRI-2012 takes about 9.2ms per execution). Satellite simulators have high real-time requirements for generating ionospheric delay (not exceeding 0.1ms). Therefore, directly using the calculation interface provided by the IRI International Reference Ionospheric Model cannot meet the real-time requirements of satellite signal simulators. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for simulating ionospheric delay in a satellite signal simulator, which can meet the real-time requirements of a satellite signal simulator.

[0006] In a first aspect, this application provides a satellite signal simulator method for simulating ionospheric time delay, the method comprising:

[0007] Step 1. Build the IRI model runtime environment to acquire global TEC grid data;

[0008] Step 2. Extract the simulation intervals input by the user from the satellite simulator interface. The start and end times of the simulation intervals are both UTC time.

[0009] Step 3. Divide the simulation time period, global latitude, global longitude, and ionospheric height into a four-dimensional grid according to the step size. Use the time t, latitude i, longitude j, and height k of each grid point as input parameters for the IRI model, and calculate the global TEC grid data Ne within the simulation time period. i,j,k (t), generating a global four-dimensional grid electron density field;

[0010] Step 4. Calculate the global four-dimensional grid electron density Ne. i,j,k (t) Perform integration to obtain the total vertical electron quantity vTEC at time t at horizontal grid i,j in the IRI model. i,j (t), based on the total vertical electron quantity vTEC at time t i,j(t) Obtain the global three-dimensional vertical electron total data file for the simulation period;

[0011] Step 5. The satellite simulator starts the satellite signal simulation function. According to the simulation time period and the required carrier trajectory in Step 1, it calculates in real time the puncture point (latitude φ) when each visible satellite signal passes through the ionosphere at the time of transmission. pp Longitude λ pp );

[0012] Step 6. Find the nearest time k0 and time k1 of the satellite simulator simulation time k, and perform linear interpolation on the three-dimensional vertical electron total data to obtain the two-dimensional ionospheric grid data at time k;

[0013] Step 7. Locate the distance from the puncture point (latitude φ) pp Longitude λ pp Nearest latitude and longitude (λ) pp1 , λ pp2 ,φ pp1 , φ pp2 ), for two-dimensional ionospheric grid data Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k ;

[0014] Step 8. Based on the vertical electron total amount vTEC at the puncture point of satellite i at simulation time k. k Calculate the corresponding ionospheric vertical delay V_iono i ;

[0015] Step 9. Based on the vertical delay of the ionosphere V_iono i Calculate the ionospheric delay I_iono generated by the satellite i signal along the propagation direction. i ;

[0016] Step 10. The satellite simulator will adjust the ionospheric time delay I_iono. i Together with other satellite signal delay information, it corrects the satellite signal transmission time, and at the same time assembles the ionospheric Klobuchar model parameters into the navigation message according to the specified signal format, and sends the satellite signal through the radio frequency port.

[0017] Furthermore, step 4 specifically includes:

[0018] Using formula Obtain the total vertical electron volume vTEC at time t at horizontal grid i,j in the IRI model. i,j (t), where i is the longitude of the global grid point, j is the latitude of the global grid point, and Δh k The vertical spacing of the grid.

[0019] Furthermore, step 6 specifically includes:

[0020] Using formula Linear interpolation is performed on the three-dimensional vertical electron totality data to obtain the two-dimensional ionospheric grid data at time k, where λ is the longitude of the ionospheric grid and φ is the latitude of the ionospheric grid.

[0021] Furthermore, step 7 specifically includes:

[0022] Using formula

[0023]

[0024] Two-dimensional ionospheric grid data Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k ,

[0025] in,

[0026]

[0027] Furthermore, step 8 specifically includes:

[0028] Using formula Calculate the corresponding ionospheric vertical delay V_iono i Where f0 is the operating frequency of the satellite system.

[0029] Furthermore, step 5 includes:

[0030] Step 51: Using the formula φ pp =sin -1 (sinφ u cosψ pp +cosφ u sinψ pp cosA (radians), calculate latitude φ pp ,

[0031] Where, ψ pp The angle between the line connecting the user's location and the center of the Earth and the line connecting the puncture point and the center of the Earth is calculated using the following formula:

[0032] Where A represents the clockwise position relative to the user. The satellite azimuth angle, It is the user's location dimension, λ u E is the user's location longitude, and E is the satellite's location relative to the user's location. altitude angle, R e h is the approximate radius of the Earth's ellipsoid.I It is the height of maximum electron density;

[0033] Step 52: Longitude λ of the puncture point pp The calculation is as follows:

[0034] if and or,

[0035] and So, the longitude λ of the puncture point pp for:

[0036] if and or,

[0037] and So, the longitude λ of the puncture point pp for:

[0038] Furthermore, step 9 includes:

[0039] Step 91: The satellite simulator uses the elevation angle of satellite i, combined with the formula... Calculate the slope factor F of the line-of-sight direction at the puncture point of the satellite signal. i , where θ i R is the elevation angle of satellite i. e h is the Earth's radius. I This represents the height of the ionosphere.

[0040] Step 92: Based on the vertical delay of the ionosphere V_iono i Combined with formula I_iono i =F i ×V_iono i Calculate the ionospheric delay I_iono caused by the satellite signal along the propagation direction. i .

[0041] Secondly, this application provides a satellite signal simulator ionospheric delay simulation device, which is used to implement the above-mentioned satellite signal simulator ionospheric delay simulation method.

[0042] The beneficial effects of this invention are:

[0043] 1) High fidelity: The simulated ionospheric delay is highly realistic. The ionospheric delay generated by the real signal makes it easier for users to evaluate the positioning accuracy of the receiver on the target point or target trajectory with higher confidence.

[0044] 2) Wide applicability: It can simulate navigation motion states at any location in the world, and can simulate navigation signals in static, low-dynamic and high-dynamic environments;

[0045] 3) Convenience: Dedicated software is used to generate ionospheric data files for the target time period, making it convenient for users to operate. Attached Figure Description

[0046] Figure 1 Flowchart for ionospheric delay calculation and superposition in a satellite signal simulator;

[0047] Figure 2 Generate a structure diagram for the radio frequency signals of a satellite signal simulator based on the IRI model;

[0048] Figure 3 This is a schematic diagram of the VTEC spatial interpolation algorithm for the ionosphere. Detailed Implementation

[0049] The technical solution is described in detail with reference to the accompanying drawings:

[0050] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0051] This invention employs the IRI (International Reference Ionospheric Model) to simulate ionospheric delay at the satellite navigation simulator end, providing the receiver end with satellite simulation signals that more closely resemble the real environment than currently used satellite simulators. This facilitates users' assessment of their own positioning capabilities at any location globally. This method is applicable to all simulators that generate satellite navigation signals, including but not limited to BeiDou, GPS, Galileo, and GLONASS satellite navigation systems.

[0052] To address the problems existing in the prior art, this invention proposes a method that uses the IRI (International Reference Ionospheric Model) to generate global ionospheric delay data files for a specified simulation period in advance. The satellite simulator calculates the puncture point of the satellite passing through the ionosphere, reads the ionospheric delay data files, and calculates the ionospheric delay of the satellite signal based on the IRI model. This is used to correct the satellite pseudorange generated by the satellite simulator, making it easier for users to accurately evaluate the positioning capability of satellite navigation equipment at any location globally.

[0053] This application provides a satellite signal simulator method for simulating ionospheric time delay, the method comprising:

[0054] Step 1. Build the IRI model running environment to acquire global ionospheric electron density (TEC) grid data;

[0055] Step 2. Extract the simulation intervals input by the user from the satellite simulator interface. The start and end times of the simulation intervals are all in UTC time (UTC time format is year, month, day, hour, minute, second).

[0056] Step 3. Divide the simulation time period, global latitude, global longitude, and ionospheric height into a four-dimensional grid according to the step size. Use the time t, latitude i, longitude j, and height k of each grid point as input parameters for the IRI model, and calculate the global TEC grid data Ne within the simulation time period. i,j,k (t), generating a global four-dimensional grid electron density field;

[0057] The data resolution of the global four-dimensional grid electron density field can be set according to actual needs, as shown in the following examples:

[0058] Grid time step Δt: 30 minutes;

[0059] Grid latitude step size Δφ: 2.5 degrees, latitude range from -90 degrees to 90 degrees;

[0060] The grid longitude step Δλ is 2.5 degrees, and the longitude range is from -180 degrees to 180 degrees.

[0061] Grid height step Δh: 30 km, with an altitude range of 60 km to 2000 km.

[0062] Step 4. Calculate the global four-dimensional grid electron density Ne. i,j,k (t) Perform integration to obtain the total vertical electron quantity vTEC at time t at horizontal grid i,j in the IRI model. i,j (t), based on the total vertical electron quantity vTEC at time t i,j (t) Obtain the global three-dimensional vertical electron total data file for the simulation period.

[0063]

[0064] Where i is the longitude of the global grid point, j is the latitude of the global grid point, and Δh k The vertical spacing of the grid.

[0065] Step 5. The satellite simulator starts the satellite signal simulation function. According to the simulation time period and the required carrier trajectory in Step 1, it calculates in real time the puncture point (latitude φ) when each visible satellite signal passes through the ionosphere at the time of transmission. pp Longitude λ pp );

[0066] Specifically, step 5 includes:

[0067] Step 51: Using the formula φ pp =sin -1 (sinφ u cosψ pp +cosφ u sinψ pp cosA (radians), calculate latitude φ pp ,

[0068] Where, ψ pp The angle between the line connecting the user's location and the center of the Earth and the line connecting the puncture point and the center of the Earth is calculated using the following formula:

[0069]

[0070] Where A represents the clockwise position relative to the user. The satellite azimuth angle. It is the user's location dimension, λ u E is the user's location longitude, and E is the satellite's location relative to the user's location. altitude angle, R e It is the approximate radius of the Earth's ellipsoid (taken as 6378.1363 km), h I It is the altitude of the maximum electron density (valued at 350km).

[0071] Step 52: Longitude λ of the puncture point pp The calculation is as follows:

[0072] if and or,

[0073] and So, the longitude λ of the puncture point pp for:

[0074] if, and or,

[0075] and So, the longitude λ of the puncture point pp for:

[0076]

[0077] Step 6. Find the nearest neighbors k0 and k1 of the satellite simulator simulation time k, and perform linear interpolation on the three-dimensional vertical electron total data to obtain the two-dimensional ionospheric grid data at time k:

[0078]

[0079] Where λ is the longitude of the ionospheric grid and φ is the latitude of the ionospheric grid.

[0080] Step 7. Locate the distance from the puncture point (latitude φ) pp Longitude λ pp Nearest latitude and longitude (λ) pp1 , λ pp2 ,φ pp1 , φ pp2 ), for two-dimensional ionospheric grid data Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k :

[0081]

[0082] in,

[0083]

[0084] Step 8. Based on the vertical electron total amount vTEC at the puncture point of satellite i at simulation time k. k Calculate the corresponding ionospheric vertical delay V_iono i ;

[0085]

[0086] Where f0 is the operating frequency of the satellite system, in MHz.

[0087] Step 9. Based on the vertical delay of the ionosphere V_iono i Calculate the ionospheric delay I_iono generated by the satellite i signal along the propagation direction. i ;

[0088] Specifically, step 9 includes:

[0089] Step 91: The satellite simulator uses the elevation angle of satellite i, combined with the formula, Calculate the slope factor F of the line-of-sight direction at the puncture point of the satellite signal. i , where θ i R is the elevation angle of satellite i (in radians). e The Earth's radius is 6,378,136 m, h I The ionospheric height is 350,000 m.

[0090] Step 92: Based on the vertical delay of the ionosphere V_iono i Combined with formula I_iono i =F i×V_iono i Calculate the ionospheric delay I_iono caused by the satellite signal along the propagation direction. i .

[0091] Step 10. The satellite simulator will adjust the ionospheric time delay I_iono. i Together with other satellite signal delay information, it corrects the satellite signal transmission time, and at the same time assembles the ionospheric Klobuchar model parameters into the navigation message according to the specified signal format, and sends the satellite signal through the radio frequency port.

[0092] Among them, satellite signal delay information includes satellite ephemeris / satellite clock delay, ionospheric delay, tropospheric delay, multipath delay, etc.

[0093] Example 1

[0094] This application provides a simulation method for ionospheric time delay using a GPS satellite signal simulator, the specific method being as follows:

[0095] Step 1. Build the IRI model runtime environment: Install MATLAB software and Fortran compiler on your computer, download the IRI interface Fortran language module provided by the official IRI model website, and ensure that your computer has internet access.

[0096] Step 2. The user inputs the start and end times of the GPS satellite signal simulation to be performed on the host computer of the GPS satellite simulator. The start and end times of this time period are both UTC time (time format is year, month, day, hour, minute, second).

[0097] Step 3: Divide the simulation time period, global latitude, global longitude, and ionospheric height into a grid according to the step size. Use the time t, latitude i, longitude j, and altitude k of each grid point as input parameters for the IRI model, and calculate the TEC grid data Ne within the simulation time period. i,j,k (t), generating a four-dimensional lattice electron density field:

[0098] Grid time step Δt: 30 minutes;

[0099] Grid latitude step size Δφ: 2.5 degrees, latitude range from -90 degrees to 90 degrees;

[0100] The grid longitude step Δλ is 2.5 degrees, and the longitude range is from -180 degrees to 180 degrees.

[0101] Grid height step Δh: 30 km, with an altitude range of 80 km to 2000 km;

[0102] Step 4. Ionospheric delay generation software processes the four-dimensional grid electron density file data Ne i,j,k(t) Integrate to obtain the total vertical electron volume vTEC of the IRI model at time t at longitude i and latitude j of the horizontal grid. i,j (t) yields a three-dimensional vertical total electron dataset.

[0103]

[0104] Save the dataset file to the specified storage directory. At this point, the generation and storage of the global ionospheric grid data are complete.

[0105] Step 5. The GPS satellite simulator starts the satellite signal simulation function. According to the simulation time period and the required carrier trajectory in Step 2, it calculates in real time the puncture point (latitude φ) of each visible GPS satellite signal transmission time when it passes through the ionosphere. pp Longitude λ pp );

[0106] Specifically, step 5 includes:

[0107] Step 51: Using the formula φ pp =sin -1 (sinφ u cosψ pp +cosφ u sinψ pp cosA (radians), calculate latitude φ pp ,

[0108] Where, ψ pp The angle between the line connecting the user's location and the center of the Earth and the line connecting the puncture point and the center of the Earth is calculated using the following formula:

[0109]

[0110] Where A represents the clockwise position relative to the user. The satellite azimuth angle. It is the user's location dimension, λ u E is the user's location longitude, and E is the satellite's location relative to the user's location. altitude angle, R e It is the approximate radius of the Earth's ellipsoid (taken as 6378.1363 km), h I It is the altitude of the maximum electron density (valued at 350km).

[0111] Step 52: Longitude λ of the puncture point pp The calculation is as follows:

[0112] if, and or,

[0113] and So, the longitude λ of the puncture point pp for:

[0114]

[0115] otherwise, and or,

[0116] and So, the longitude λ of the puncture point pp for:

[0117]

[0118] Step 6. Find the nearest neighbors k0 and k1 of the GPS satellite simulator simulation time k. Using the three-dimensional vertical electron total data, obtain the two-dimensional ionospheric grid data of time k through linear interpolation:

[0119]

[0120] Where i is the grid longitude and j is the grid latitude.

[0121] Step 7. Locate the distance from the puncture point (latitude φ) pp Longitude λ pp Nearest latitude and longitude (λ) pp1 , λ pp2 ,φ pp1 , φ pp2 Bilinear interpolation was performed on the two-dimensional ionospheric grid data to obtain the vertical electron total value (vTEC) at the puncture point. k :

[0122]

[0123] in,

[0124] Step 8. Based on the total vertical electron volume vTEC k The vertical ionospheric delay V_iono corresponding to the puncture point of the visible GPS satellite at the simulation time is calculated. i ;

[0125]

[0126] Where f0 is the operating frequency of the satellite system, in MHz.

[0127] Step 9. Based on the vertical delay of the ionosphere V_iono iCalculate the ionospheric delay I_iono generated by the GPS satellite i signal along the propagation direction. i ;

[0128] Specifically, step 9 includes:

[0129] Step 91: The satellite simulator uses the elevation angle of GPS satellite i, combined with the formula, Calculate the slope factor F of the line-of-sight direction at the puncture point of the GPS satellite signal. i , where θ i R is the elevation angle of GPS satellite i (in radians). e The Earth's radius is 6,378,136 m, h I The ionospheric height is 350,000 m.

[0130] Step 92: Based on the vertical delay of the ionosphere V_iono i Combined with formula I_iono i =F i ×V_iono i Calculate the ionospheric delay I_iono caused by GPS satellite signals along the propagation direction. i .

[0131] Step 10. The GPS satellite simulator uses the calculated ionospheric delay I_ionoi, along with other GPS satellite signal delay information such as ephemeris error, satellite clock error, Earth rotation, tropospheric delay, and multipath delay, to correct the GPS satellite signal transmission time. At the same time, it assembles the ionospheric Klobuchar model parameters into the GPS navigation message according to the specified signal format and sends the GPS satellite signal through the radio frequency port.

[0132] Example 2

[0133] This application provides a method for a satellite simulator to access a local or remote database to simulate ionospheric delay in 2024. The specific method is as follows:

[0134] Step 1. Build the IRI model runtime environment: Install MATLAB software and Fortran compiler on your computer, download the IRI interface Fortran language module provided by the official IRI model website, and ensure that your computer has internet access.

[0135] Step 2. The simulation period is the entire year of 2024, and the period is decomposed into time parameters with a step size of 30 minutes (time format is year, month, day, hour, minute, second);

[0136] Step 3. Using MATLAB-based ionospheric delay generation software, input the time t, latitude i, longitude j, and altitude k obtained in Step 2 into the IRI ionospheric model interface. The IRI model calculates the global ionospheric grid electron density data Ne corresponding to that moment. i,j,k (t), generating a four-dimensional (time t, latitude i, longitude j, altitude k) grid electron density file:

[0137] Grid time step: 30 minutes;

[0138] Grid latitude step size: 2.5 degrees, latitude range: -90 degrees to 90 degrees;

[0139] Grid longitude step: 5 degrees, longitude range: -180 degrees to 180 degrees;

[0140] Grid height step: 30 km, with an altitude range of 80 km to 2000 km;

[0141] Step 4: The ionospheric delay generation software integrates the four-dimensional grid electron density file data generated in Step 3 to obtain the total vertical electron quantity vTEC at time t at horizontal grid i,j in the IRI model. i,j (t) to obtain three-dimensional (time, latitude, longitude) vertical total electron data as a dataset, and save the dataset file to the specified storage directory.

[0142] Step 5. Save the dataset file generated in Step 4 to a large-capacity hard drive for repeated access by the satellite simulator, either locally or remotely.

[0143] Step 6. The satellite simulator starts the satellite signal simulation function. The simulation time period set by the user can be any time between 00:00 on January 1, 2024 and 23:59 on December 31, 2024. The user sets the carrier to be moving or stationary. The satellite simulator calculates in real time the puncture point position (latitude φ) when the signal of each visible satellite passes through the ionosphere at the time of signal transmission. pp Longitude λ pp );

[0144] Step 7: Find the nearest neighbors k0 and k1 of the satellite simulator simulation time k. Using the three-dimensional vertical electron total data generated in Step 3, obtain the two-dimensional ionospheric grid data at time k through linear interpolation:

[0145]

[0146] in,

[0147] Step 7. Locate the distance from the puncture point (latitude φ) pp Longitude λ pp Nearest latitude and longitude (λ)pp1 , λ pp2 ,φ pp1 φ pp2 Using two-dimensional ionospheric grid data, the vertical electron totality (vTEC) at the puncture point was obtained through bilinear interpolation. k :

[0148]

[0149] in,

[0150] Step 8. Based on the total vertical electron volume vTEC k Calculate the vertical ionospheric delay V_iono corresponding to all visible satellite puncture points at the simulation time. i ;

[0151]

[0152] Where f0 is the operating frequency of the satellite system, in MHz.

[0153] Step 9. The satellite simulator uses the satellite i position and the local position to calculate the slope factor Fi of the line of sight direction at the puncture point of the satellite signal, and then calculates the ionospheric delay I_ionoi generated by the satellite signal along the propagation direction;

[0154]

[0155] Where: θ i R is the elevation angle of satellite i (in radians). e The Earth's radius is 6,378,136 m, h I The average height of the ionosphere is 350,000 m.

[0156] I_iono i =F i ×V_iono i

[0157] Step 10. The satellite simulator uses the calculated ionospheric delay I_ionoi, along with other satellite signal delay information, to correct the satellite signal transmission time. At the same time, it assembles the ionospheric Klobuchar model parameters into the navigation message according to the specified signal format and sends the satellite signal through the radio frequency port.

[0158] Among them, satellite signal delay information includes ephemeris error, satellite clock error, Earth rotation, ionospheric delay, tropospheric delay, multipath delay, etc.

Claims

1. A method for simulating ionospheric time delay using a satellite signal simulator, characterized in that, The methods include: Step 1. Build the IRI model runtime environment to acquire global TEC grid data; Step 2. Extract the simulation intervals input by the user from the satellite simulator interface. The start and end times of the simulation intervals are both UTC time. Step 3. Calculate the global TEC grid data Ne during the simulation period. i,j,k (t), generating a global four-dimensional grid electron density field; Step 4. Based on the total vertical electron quantity vTEC at time t i,j (t) Obtain the global three-dimensional vertical electron total data file for the simulation period; Step 5. The satellite simulator starts the satellite signal simulation function to calculate in real time the location of the puncture point when the signal of each visible satellite passes through the ionosphere at the time of its transmission. Step 6. Perform linear interpolation on the three-dimensional vertical electron total data to obtain the two-dimensional ionospheric grid data at time k; Step 7. Find the nearest latitude and longitude coordinates to the puncture point and analyze the two-dimensional ionospheric grid data. Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k ; Step 8. Based on the total vertical electron volume vTEC k Calculate the corresponding ionospheric vertical delay V_iono i ; Step 9. Based on the vertical delay of the ionosphere V_iono i Calculate the ionospheric delay I_iono generated by the satellite i signal along the propagation direction. i ; Step 10. The satellite simulator will adjust the ionospheric time delay I_iono. i The satellite signal transmission time is corrected.

2. The method according to claim 1, characterized in that, include: Step 1. Build the IRI model runtime environment to acquire global TEC grid data; Step 2. Extract the simulation intervals input by the user from the satellite simulator interface. The start and end times of the simulation intervals are both UTC time. Step 3. Divide the simulation time period, global latitude, global longitude, and ionospheric height into a four-dimensional grid according to the step size. Use the time t, latitude i, longitude j, and height k of each grid point as input parameters for the IRI model, and calculate the global TEC grid data Ne within the simulation time period. i,j,k (t), generating a global four-dimensional grid electron density field; Step 4. Calculate the global four-dimensional grid electron density Ne. i,j,k (t) Perform integration to obtain the total vertical electron quantity vTEC at time t at horizontal grid i,j in the IRI model. i,j (t), based on the total vertical electron quantity vTEC at time t i,j (t) Obtain the global three-dimensional vertical electron total data file for the simulation period; Step 5. The satellite simulator starts the satellite signal simulation function. According to the simulation time period and the required carrier trajectory in Step 1, it calculates in real time the puncture point (latitude φ) when each visible satellite signal passes through the ionosphere at the time of transmission. pp Longitude λ pp ); Step 6. Find the nearest time k0 and time k1 of the satellite simulator simulation time k, and perform linear interpolation on the three-dimensional vertical electron total data to obtain the two-dimensional ionospheric grid data at time k; Step 7. Locate the distance from the puncture point (latitude φ) pp Longitude λ pp Nearest latitude and longitude (λ) pp1 , λ pp2 ,φ pp1 , φ pp2 ), for two-dimensional ionospheric grid data Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k ; Step 8. Based on the vertical electron total amount vTEC at the puncture point of satellite i at simulation time k. k Calculate the corresponding ionospheric vertical delay V_iono i ; Step 9. Based on the vertical delay of the ionosphere V_iono i Calculate the ionospheric delay I_iono generated by the satellite i signal along the propagation direction. i ; Step 10. The satellite simulator will adjust the ionospheric time delay I_iono. i Together with other satellite signal delay information, it corrects the satellite signal transmission time, and at the same time assembles the ionospheric Klobuchar model parameters into the navigation message according to the specified signal format, and sends the satellite signal through the radio frequency port.

3. The method according to claim 1, characterized in that, Step 4 specifically includes: Using formula Obtain the total vertical electron volume vTEC at time t at horizontal grid i,j in the IRI model. i,j (t), where i is the longitude of the global grid point, j is the latitude of the global grid point, and Δh k The vertical spacing of the grid.

4. The method according to claim 1, characterized in that, Step 6 specifically includes: Using formula Linear interpolation is performed on the three-dimensional vertical electron totality data to obtain the two-dimensional ionospheric grid data at time k, where λ is the longitude of the ionospheric grid and φ is the latitude of the ionospheric grid.

5. The method according to claim 1, characterized in that, Step 7 specifically includes: using the formula: Two-dimensional ionospheric grid data Bilinear interpolation is performed to obtain the vertical electron total value (vTEC) at the puncture point. k , in, 6. The method according to claim 1, characterized in that, Step 8 specifically includes: Using formula Calculate the corresponding ionospheric vertical delay V_iono i Where f0 is the operating frequency of the satellite system.

7. The method according to claim 1, characterized in that, Step 5 includes: Step 51: Using the formula φ pp =sin -1 (sinφ u cosψ pp +cosφ u sinψ pp cosA (radians), calculate latitude φ pp , Where, ψ pp The angle between the line connecting the user's location and the center of the Earth and the line connecting the puncture point and the center of the Earth is calculated using the following formula: Where A represents the clockwise position relative to the user. The satellite azimuth angle, It is the user's location dimension, λ u E is the user's location longitude, and E is the satellite's location relative to the user's location. altitude angle, R e h is the approximate radius of the Earth's ellipsoid. I It is the height of maximum electron density; Step 52: Longitude λ of the puncture point pp The calculation is as follows: if and or, and So, the longitude λ of the puncture point pp for: if and or, and So, the longitude λ of the puncture point pp for:

8. The method according to claim 1, characterized in that, Step 9 includes: Step 91: The satellite simulator uses the elevation angle of satellite i, combined with the formula... Calculate the slope factor F of the line-of-sight direction at the puncture point of the satellite signal. i , where θ i R is the elevation angle of satellite i. e h is the Earth's radius. I This represents the height of the ionosphere. Step 92: Based on the vertical delay of the ionosphere V_iono i Combined with formula I_iono i =F i ×V_iono i Calculate the ionospheric delay I_iono caused by the satellite signal along the propagation direction. i .

9. A satellite signal simulator for ionospheric time delay simulation, characterized in that, The device is used to implement the satellite signal simulator ionospheric delay simulation method as described in claim 1.

Images