阅读说明：本技术 基于数据仿真验证三频信标tec反演精度的方法及系统 (Method and system for verifying inversion precision of tri-band beacon TEC based on data simulation ) 是由 林剑 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种基于数据仿真验证三频信标TEC反演精度的方法及系统,属于TEC测量技术领域,包括：(1)利用站星距与电离层背景信息仿真三种频率信号的多普勒频移；(2)利用高斯分布仿真相位观测噪音；(3)基于多普勒频移与相位观测噪音获取仿真的三种频率信号的差分多普勒相移；(4)基于仿真的三种频率信号的差分多普勒相移数据反演电离层TEC。本发明主要基于仿真技术来实现对电波在电离层中传播引起的多普勒频移的模拟,来实现利用三频信标技术反演高精度电离层TEC；通过仿真验证证明了三频信标反演高精度TEC的精度与可行性,对于中国地震局电磁试验卫星随后的工作具有重要指导意义。(The invention discloses a method and a system for verifying inversion accuracy of a tri-band beacon TEC based on data simulation, belonging to the technical field of TEC measurement and comprising the following steps: (1) simulating Doppler frequency shift of three frequency signals by using the station star distance and the ionosphere background information; (2) simulating phase observation noise by using Gaussian distribution; (3) acquiring differential Doppler phase shifts of the simulated three frequency signals based on the Doppler frequency shift and phase observation noise; (4) and inverting the ionized layer TEC based on the simulated differential Doppler phase shift data of the three frequency signals. The invention mainly realizes the simulation of Doppler frequency shift caused by the propagation of electric waves in the ionized layer based on a simulation technology, so as to realize the inversion of the high-precision ionized layer TEC by utilizing a triple-frequency beacon technology; simulation verification proves that the accuracy and feasibility of the high-accuracy TEC inverted by the triple-frequency beacon have important guiding significance for subsequent work of the electromagnetic test satellite of the China seismic Bureau.)

1. A method for verifying inversion accuracy of a tri-band beacon TEC based on data simulation is characterized by comprising the following steps:

(1) simulating Doppler frequency shift of three frequency signals by using the station star distance and the ionosphere background information;

(2) simulating phase observation noise by using Gaussian distribution;

(3) acquiring differential Doppler phase shifts of the simulated three frequency signals based on the Doppler frequency shift and phase observation noise;

(4) and inverting the ionized layer TEC based on the simulated differential Doppler phase shift data of the three frequency signals.

2. The method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation as claimed in claim 1, wherein the step (1) is:

obtaining the ephemeris of the epoch station by using the known real-time satellite coordinates of the epoch and the coordinates of the survey station; then simulating Doppler frequency shift of three frequency signals by using station star distance and IRI model ionosphere background information;

doppler shift between two signal links of adjacent epochs:

wherein, Δ f is Doppler shift, the first term of the right expression is Doppler shift caused by satellite motion, and the second term is Doppler shift caused by ionosphere; the first term is proportional to the signal frequency f, the second term is inversely proportional to the signal frequency f, and the influence of the first term is eliminated by using difference; and (3) making a difference on the distance s of the adjacent links to obtain Δ s, and taking the time interval 1s as a time increment Δ t, then:

the same is that:

the Doppler frequency shifts of the three frequency signals are respectively obtained.

3. The method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation as claimed in claim 1 or 2, wherein the step (2) is:

adding simulated signal phases and simulating the receiving errors of signals by Gaussian distribution phase errors of 1 degree, 3 degrees and 6 degrees respectively; so as to realize the observation of noise by simulating the phase by utilizing Gaussian distribution.

4. The method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation as claimed in claim 3, wherein the step (3) is:

the wavelength variation Δ λ of the signal can be calculated from the doppler shift and the initial wavelength λ of the signal:

based on the station-to-satellite distance, the wavelength variation, and the phase error, a simulated differential doppler phase shift may be obtained.

5. The method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation as claimed in any one of claims 1 to 4, wherein the step (4) is:

the resolving formula of the TEC is as follows:

TEC＝8.3165×10¹⁶[(Δφ₁₃×7-Δφ₁₂×8)_mod(1)+k]

wherein, is₁₂And delta phi₁₃Respectively representing differential Doppler phase shifts Δ Φ₁₂And Δ Φ₁₃The fractional part of (a); delta phi₁₂Representing a differential doppler phase shift of 1 frequency and 2 frequencies; delta phi₁₃Representing differential doppler phase shifts of 1 and 3 frequencies; mod (1) represents a remainder on 1; k denotes a tri-frequency phase integration constant.

6. The method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation as claimed in claim 5, wherein the calculation method of the tri-band phase integration constant k is as follows: estimating a coarse TEC value through a double-station or multi-station method based on an ionosphere local spherical symmetry hypothesis and through a double-frequency phase; and calculating an integral constant through a tri-frequency phase TEC expression.

7. A system for verifying inversion accuracy of a tri-band beacon TEC based on data simulation is characterized by comprising the following steps:

one or more processors;

storage means for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement a method of verifying inversion accuracy of a triple-band beacon TEC based on data simulation according to any one of claims 1 to 6.

Technical Field

The invention relates to the technical field of TEC measurement, in particular to a method and a system for verifying inversion accuracy of a tri-band beacon TEC based on data simulation.

Background

The tri-band beacon technology is a novel TEC measurement technology, and is a novel efficient space environment measurement technology for acquiring parameter information such as total electron content of an ionosphere and an electron density profile in a large range and high precision by transmitting a group of phase-coherent radio signals (VHF, UHF and L frequency bands) to receiving equipment located in a ground monitoring station through a tri-band beacon transmitter installed on a low earth orbit satellite.

In 2018, the first electromagnetic test satellite ZH-1 in China was successfully launched by the earthquake Bureau of China. ZH-1 carries high-precision magnetometer, GNSS masker receiver, threeThe equal load of the frequency beacon transmitter opens the precedent river of autonomously detecting the space geophysical field and various electromagnetic disturbance signals in China^[1]. Since the first discovery by academists of Alaska earthquake in 1964 that earthquake can cause significant ionospheric disturbance^[2]It has become common knowledge that an earthquake can induce ionospheric disturbances. A number of methods for obtaining high resolution ionospheric parameters have emerged in recent years: occultation inversion method^[3]Time delay method for tri-band beacon^[4]Doppler frequency shift method for tri-band beacon^[5]And the like.

TEC can reflect the main properties of the ionosphere and is closely related to the time delay and phase delay of radio waves propagating in the ionosphere. Therefore, the ionized layer TEC information can be widely applied to the fields of navigation positioning, radio wave signal correction of communication and the like, and meanwhile, the ionized layer TEC can be inverted according to the time delay and the phase delay of radio wave propagation.

The triple-frequency beacon technology is an emerging technology which can obtain the high-precision TEC by utilizing the propagation frequency shift inversion of three frequency electric wave signals. Austen et al (1988) first studied the ionospheric tomography (CIT) technique, which thereafter became the detection tool used with satellite beacons and ground-based receiving stations^[1]. The dual-frequency beacon technology is to calculate the differential time delay or doppler shift of two frequencies, so as to obtain the Total Electronic Content (TEC) on a link. When the tri-band beacon technology is adopted, the TEC on the link can be obtained by the same method, and three groups of values can be obtained. The precision and the reliability of the TEC can be improved through related mathematical processing. Bernhardt, American navy laboratory^[6]And the like performs strict mathematical derivation on the basis of flexible application of number theory knowledge to obtain the TEC algorithm. The algorithm has the advantages that on one hand, the accuracy of determining the phase integral constant is improved by a large amplitude, on the other hand, the difficulty in solving the phase integral constant is greatly reduced, and the algorithm has great significance for the development of the tri-frequency beacon technology. The united states first applied this innovative work to military and meteorological research. The COSMIC satellite successfully transmitted in 2006 carries a tri-band beacon transmitter TBB, and the project cooperates with Taiwan areas in China to establish low latitude ionosphere explorationThe chain measurement is used for researching the ionosphere form and disturbance in a low latitude area, and can effectively monitor the ionosphere structure change in an earthquake high-incidence area^[7]. Therefore, the China earthquake Bureau also carries out a satellite-based ionosphere detection plan, and a Zhang Heng I electromagnetic test satellite which is launched to the sky in 2018 is also provided with a triple-frequency beacon transmitter developed by the China electronic department 22.

But for certain technical reasons the transmitter does not work properly. Therefore, how to put forward a method for verifying inversion accuracy of the tri-band beacon TEC based on data simulation based on the current state of China has important guiding significance for the subsequent work of the electromagnetic test satellite of the earthquake bureau of China.

The relevant documents are as follows:

[1] zhang student, Shenxuhui, Zhao Shun, Liu Jing, Euro Yang Xinyan, Lou Wen Yuu, Zeren Zhima, He Jianhui, Qian Heng seismic ionosphere survey technique and its application research progress [ J ]. earthquake science report 2016,38(03):356-375.

[2]Leonard R S,Barnes Jr R A.Observation of ionospheric disturbances following the Alaska earthquake[J].Journal of Geophysical Research,1965,70(5):1250-1253.

[3] Rinshu, Wuyun, Liu Jing nan. ionosphere GPS occultation inversion technique research [ J ]. geophysical science report, 2009,52(08): 1947-.

[4] Wujia, a new ionospheric weather measurement method by using tri-band satellite beacons [ J ]. China science A edition, 2000,30(Z1):111-114.DOI:10.3321/j.issn:1006-9232.2000.Z1.029.

[5] Zhao Haisheng, xu text, Wu Jian, Wang Zhangge, Liu Yu, Lian, Chen jin Song, three-frequency-communication new method for measuring elevation precision TEC [ J ]. New method for space science, 2011,31(02):201 and 207).

[6]Paul A.Bernhardt,Carl L.Siefring.New satellite-based systems for ionospheric tomography and scintillation region imaging[J].Paul A.Bernhardt；Carl L.Siefring,2006,41(5).

[7] Zhao Haisheng, three-frequency beacon ionosphere disturbance detection and tomography key technology research [ D ]. Hangzhou electronic technology university 2010.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for verifying the inversion accuracy of the tri-band beacon TEC based on data simulation, so that an effective verification method can be provided for the inversion accuracy of the tri-band beacon TEC, and the accuracy and feasibility of inverting the high-accuracy TEC by the tri-band beacon are proved.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method for verifying inversion accuracy of a tri-band beacon TEC based on data simulation comprises the following steps:

(1) simulating Doppler frequency shift of three frequency signals by using the station star distance and the ionosphere background information;

(2) simulating phase observation noise by using Gaussian distribution;

(3) acquiring differential Doppler phase shifts of the simulated three frequency signals based on the Doppler frequency shift and phase observation noise;

(4) and inverting the ionized layer TEC based on the simulated differential Doppler phase shift data of the three frequency signals.

As a further improvement of the invention, the step (1) is as follows:

obtaining the ephemeris of the epoch station by using the known real-time satellite coordinates of the epoch and the coordinates of the survey station; then simulating Doppler frequency shift of three frequency signals by using station star distance and IRI model ionosphere background information;

doppler shift between two signal links of adjacent epochs:

wherein, Δ f is Doppler shift, the first term of the right expression is Doppler shift caused by satellite motion, and the second term is Doppler shift caused by ionosphere; the first term is proportional to the signal frequency f, the second term is inversely proportional to the signal frequency f, and the influence of the first term is eliminated by using difference; and (3) making a difference on the distance s of the adjacent links to obtain Δ s, and taking the time interval 1s as a time increment Δ t, then:

the same is that:

the Doppler frequency shifts of the three frequency signals are respectively obtained.

Further, the step (2) is:

adding simulated signal phases and simulating the receiving errors of signals by Gaussian distribution phase errors of 1 degree, 3 degrees and 6 degrees respectively; so as to realize the observation of noise by simulating the phase by utilizing Gaussian distribution.

Further, the step (3) is:

the wavelength variation Δ λ of the signal can be calculated from the doppler shift and the initial wavelength λ of the signal:

based on the station-to-satellite distance, the wavelength variation, and the phase error, a simulated differential doppler phase shift may be obtained.

Further, the step (4) is:

the resolving formula of the TEC is as follows:

TEC＝8.3165×10¹⁶[(Δφ₁₃×7-Δφ₁₂×8)_mod(1)+k]

wherein, is₁₂And delta phi₁₃Respectively representing differential Doppler phase shifts Δ Φ₁₂And Δ Φ₁₃The fractional part of (a); delta phi₁₂Representing a differential doppler phase shift of 1 frequency and 2 frequencies; delta phi₁₃Representing differential doppler phase shifts of 1 and 3 frequencies; mod (1) represents a remainder on 1; k denotes a tri-frequency phase integration constant.

Further, the calculation method of the tri-frequency phase integration constant k is as follows: estimating a coarse TEC value through a double-station or multi-station method based on an ionosphere local spherical symmetry hypothesis and through a double-frequency phase; and calculating an integral constant through a tri-frequency phase TEC expression.

The invention also provides a system for verifying the inversion accuracy of the tri-band beacon TEC based on data simulation, which comprises the following steps: one or more processors; storage means for storing one or more programs; when executed by the one or more processors, cause the one or more processors to implement the above-described method for verifying inversion accuracy of a triple-band beacon TEC based on data simulation.

By adopting the technical scheme, the invention at least has the following advantages:

the invention mainly realizes the simulation of Doppler frequency shift caused by the propagation of electric waves in an ionized layer based on a simulation technology to realize the inversion of the high-precision ionized layer TEC by using a triple-frequency beacon technology.

Drawings

The foregoing is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and the detailed description.

FIG. 1 is a graph of error averages for a four-station dual-frequency inversion TEC;

FIG. 2 is a diagram of the error RMS of a four station dual frequency inversion TEC;

FIG. 3 is a graph of error averages for a four station three frequency inversion TEC;

FIG. 4 is a four station three frequency inversion TEC error RMS plot;

fig. 5 is a schematic diagram of a distribution of thirteen triple-frequency beacon receiving stations;

FIG. 6 is a thirteen station triple frequency inversion TEC error average;

FIG. 7 is a thirteen station triple frequency inversion TEC error RMS.

Detailed Description

The method is based on a triple-frequency beacon technology, utilizes a simulation method to simulate Doppler frequency shift caused by propagation of electric wave signals in an ionized layer, utilizes the Doppler frequency shift to solve the relative TEC, then uses a multi-station method to obtain the dual-frequency TEC based on the relative TEC, and combines an accurate Doppler phase shift decimal part with the rough TEC to solve the high-precision TEC. The accuracy and feasibility of the inversion of the high-accuracy TEC by the triple-frequency beacon technology are proved, and the method has important significance for the subsequent work of the electromagnetic test satellite of the Chinese seismic bureau.

The invention is described in detail below:

1. TEC principle for measuring tri-frequency beacon

1.1 TEC principle for double-frequency measurement

The ionosphere's propagation phase effect for different frequency signals is different due to the dispersive nature of the ionosphere. Two groups of signals with different frequencies are sent out simultaneously, the phases of the signals reaching the receiving station are different, and the phase difference comprises ionospheric information on the propagation path. Therefore, we can use the phase difference of the two sets of signals to invert the TEC on the propagation path.

Generally, high frequency signals (VHF and UHF) are used, and the approximate high frequency refractive index formula:

wherein q represents an angle between a propagation direction of the radio wave and the magnetic field,f_Bthe q value can be obtained by a magnetic field model, and the ionospheric electron density can be further inverted by the refractive index n. Here we assume that the propagating electrical wave signal collides with the medium inelastically, and the magnetic field has little or no effect on its propagation process, the above formula can be simplified as:

where n is the refractive index, f is the signal frequency, f_pIs the ionospheric plasma frequency.

Wherein N is_eIs electron density, e is electron charge, m is electron mass, e₀Is the free space dielectric constant. The following can be obtained:

obtaining:

suppose that the phase of the signal propagating to the receiving station is phi_rThe phase of the signal is phi_sThe relationship between them is:

where ω is the angular frequency and L represents the optical path distance from the satellite to the receiving station.

Two-sided differential over time:

as can be seen, the doppler shift Δ f:

wherein the former term represents the doppler shift caused by satellite motion and the latter term represents the doppler shift caused by ionospheric media. It can be seen that the effect of the satellite motion isThe signal frequency is directly proportional and the ionospheric medium influence is inversely proportional to the signal frequency. Therefore, the influence of the satellite motion can be eliminated by linearly combining and differentiating the two frequency signals. In the experiment we used three frequency signals: f. of₁＝150.012Mhz，f₂＝400.032Mhz，f₃1066.752Mhz, the three frequency signals are represented by f_rA 16.668Mhz fundamental frequency signal is generated.

Differentiating the Doppler shift of the dual-frequency signal:

integrating two sides to obtain:

phi (t) represents the differential Doppler shift, phi₀Which represents the phase integration constant, is,the integral of the electron density along the propagation path is represented as the TEC.

1.2 TEC principle for measuring tri-frequency beacon

The triple-band beacon technology is to add a frequency signal on the basis of double frequency. In principle, two signals are combined and differentiated, and three groups of doppler shifts can be obtained to perform TEC measurement:

the following can be obtained:

wherein m is₁,m₂And m₃Coprime, by mathematical relationship^[6]The above two formulas are combined to obtain a formula for resolving the TEC by the tri-band beacon:

TEC＝8.3165×10¹⁶[(Δφ₁₃×7-Δφ₁₂×8)_mod(1)+k]

wherein, is₁₂And delta phi₁₃Respectively represents delta phi₁₁And Δ Φ₁₃Taking the remainder of 2 pi, namely the decimal part of the differential Doppler phase; mod (1) represents a remainder on 1. k represents a tri-frequency phase integration constant, and is similar to a dual-frequency phase integration constant, and after an accurate k value is determined, the high-precision TEC can be obtained.

2. Simulation process and results

2.1 simulation principle

The invention mainly utilizes a simulation method to research the inversion of the high-precision ionized layer TEC by the triple-frequency beacon technology. In order to simulate Doppler frequency shift in a signal propagation process, coordinates of survey stations are required to be known, and each survey station receives an epoch real-time satellite coordinate, a corresponding real-time satellite height angle and IRI model background ionosphere TEC information. The invention initially establishes an observation network consisting of four stations, wherein the network is in rectangular distribution, and the coordinates of the four stations are as follows:

coordinate of measuring station	1	2	3	4
					Lat(N)	24°	26°	24°	26°
Long(E)	100°	100°	105°	105°

The observation epoch intervals of the four survey stations are 1s, the background ionized layer TEC between the survey stations and the satellite is given by an IRI model, and the coordinates of the stations and the coordinates of the real-time satellite are known.

Firstly, obtaining the epoch real-time station star distance by using the known epoch real-time satellite coordinates and the survey station coordinates. And then simulating the Doppler frequency shift of the three frequency signals by using the station star distance, the ionosphere background information and the like.

Doppler shift between two signal links of adjacent epochs:

where Δ f is the doppler shift, the first term of the right equation is the doppler shift caused by satellite motion, and the second term is the ionospheric doppler shift. The first term is proportional to the signal frequency f and the second term is inversely proportional, so that the influence of the first term can be eliminated by using a difference. And (3) making a difference on the distance S of the adjacent links to obtain an approximate delta S, and taking the time interval 1S as a time increment delta t, then:

the same is that:

the doppler shifts of the three frequency signals can be obtained respectively, and the wavelength variation Δ λ of the signal can be calculated from the doppler shifts:

by using the station-to-satellite distance, the wavelength variation and the phase error, the doppler phase shift can be calculated:

according to the foregoing, the influence of satellite motion can be eliminated by performing pairwise difference on the doppler phase shifts of the three frequency signals:

and respectively obtaining the differential phase shift of the 1-frequency signal (150MHz) and the 2-frequency signal (400MHz) and the differential phase shift of the 1-frequency signal (150MHz) and the 3-frequency signal (1066 MHz). The relative TEC values can be found using differential phase shift:

since the integration constant is unknown, the TEC found is only the relative TEC between epochs, and only represents the relative change. The integration constant needs to be estimated if the absolute TEC is to be known.

After obtaining the relative TEC, a multi-station method is required to estimate the integration constant. We use four stations, roughly square in distribution. First we need to calculate the ionosphere puncture point coordinates (height set to 350km) from known information, find the puncture point coordinates (IPP) for each observation epoch for four stations (guo weshing. TEC distribution and electron density inversion technique based on satellite beacons study [ D ]. sienna electronics university, 2017.):

wherein Φ is the geocentric angle, which represents the angle between the radial direction from the puncture point IPP to the geocentric and the radial direction from the receiving station to the geocentric. Theta denotes the satellite elevation angle and alpha denotes the satellite azimuth angle at the receiving station. R denotes the earth radius and H denotes the puncture point height, we take the average ionospheric height of 350 km.

As mentioned above, we can obtain the relative TEC from the Doppler shift, and after determining the phase integration constant, we can obtain the absolute TEC. In general, the two-station method proposed by Leitinger in 1975 (Leitinger R, Schmidt G, Tauriainen A. an evaluation method combining the differential Doppler measurements from two stations that can be used for the calculation of the electronic content of the ionic P.J. Revista Current I, 1975,41(2):201 and 213) is used, and the two-station method can be expanded to a multi-station method. Here we choose a multi-station approach to estimate the phase integration constant.

Because the inversion of the method needs the synchronous observation result of three frequency signals, the time epoch screening is firstly carried out on the measurement result, the screening condition is that the satellite altitude is higher than 15 degrees, and the common time epoch data of four observation stations is selected, and 285 epochs are counted. The central idea of the multi-station method is to use the least square principle to perform fitting:

for two stations that are relatively close to each other, the vertical TEC values that we can measure at the same time should be equal. Therefore, two stations with a short distance of each epoch are selected to form a set of equations, and 570 equations are combined to form an equation set for fitting.

The path tilt TEC can be converted to a perpendicular TEC using a puncture point elevation trigonometric function:

TEC_v＝TEC_S*cosχ

TEC_s1*cosχ₁-TEC_s2*cosx₂＝0

and establishing a multi-station method equation set, solving the equation set to obtain an estimated initial absolute TEC value of each measuring station, and adding the relative TEC value between epochs obtained in the last step to obtain a dual-frequency absolute TEC value.

Different from the dual-frequency signal, the calculation principle of utilizing the tri-frequency signal is to firstly utilize the dual-frequency signal to calculate the TEC coarse value and then utilize the tri-frequency signal to precisely measure the relative value of the TEC. The differential phase is considered as an integer term and a decimal term, and similar to the integer ambiguity problem in GPS observation, the integer term can be solved by using an iterative method. The phase integral constant of the tri-band beacon is far larger than the phase integral constant of the dual-band beacon, the relative TEC value can be determined well, the combination of the decimal terms can be used for accurately determining the relative TEC value, and the relative TEC value and the fractional terms are added to obtain the high-precision absolute TEC value.

WhereinAndrepresenting 1 and 2,3 frequencies respectivelyThe fractional part of the differential Doppler phase, k is a triple-frequency phase integral constant and is an integer, and the specific k solving method comprises the following steps: estimating a coarse TEC value through a double-station or multi-station method based on an ionosphere local spherical symmetry hypothesis and through a double-frequency phase; and calculating an integral constant through a tri-frequency phase TEC expression.

2.2 program implementation and results

According to the principle and the data processing steps, an algorithm program is written by using a Fortran language, and the simulation data of the four measuring stations are solved. The input data comprises station coordinates of the survey station, corresponding satellite coordinates at epoch time, satellite altitude and background ionosphere information of the IRI model. And outputting the ionized layer TEC value resolved by using a three-frequency technology, and comparing the ionized layer TEC value with background ionized layer information of a prior model to obtain the resolving precision of a three-frequency algorithm.

The program functions mainly comprise three major parts:

1. the Doppler frequency shift/time delay of the three-frequency beacon signal propagation is simulated by using the known data to obtain the differential relative TEC between epochs

2. Calculating coarse dual-frequency TEC by utilizing multi-station method

3. Determination of high-precision TEC by utilizing fraction part of simulated relative TEC

Firstly, a 150MHz signal and a 400MHz signal are combined by using a double-frequency technology, Doppler phase shift of the double-frequency signal is obtained through simulation, then a phase integration constant is estimated by using a multi-station method, and the two are substituted into a calculation formula to obtain the double-frequency TEC. The dual-frequency TEC has large calculation ambiguity (namely a phase integration constant), and the phase integration estimated by using a multi-station method is often not accurate enough, so that the inversion accuracy is poor, and the dual-frequency TEC is called as a dual-frequency coarse TEC.

The statistics of differences between the four station TECs and the background ionosphere TEC inverted using the dual-frequency technique are shown in fig. 1 and 2. The invention uses the mean value and the root mean square value RMS to evaluate the accuracy of the inversion algorithm, wherein the accuracy comprises the statistic of the absolute value of the difference value of the TEC and the statistic of the relative value. It can be seen that the absolute mean of the differences for the four station inversion TECs when using the dual frequency method is between 0.7 TECUs and 2.5 TECUs, the relative mean of the differences is between 3% and 8.5%, the absolute RMS difference is between 0.7 and 2.7 TECUs, and the relative RMS difference is between 3% and 9%. The inversion accuracy of the third survey station is high, the absolute value of the difference can reach below 1 TECU, and other stations are 1.5 to 2.5 TECUs. And the size of the Gaussian error has no obvious influence on the precision of the double-frequency inversion. This is because the dual-frequency phase integral constant is small and the phase integral constant has a decisive influence, so that the accuracy of the relative doppler shift does not greatly affect the accuracy of the dual-frequency inversion.

After the double-frequency coarse TEC is obtained, the high-precision tri-frequency TEC is solved by using the method given in the flow chart. The above principle mentions that the tri-band TEC has high precision because the phase integration constant is large, the corresponding phase integration constant is better solved, and the precision of the inversion TEC can be determined by the precise doppler shift decimal part.

As shown in fig. 3 and 4, the TEC obtained by inversion using the triple-frequency technique has high accuracy. Under the condition of not adding errors, the difference average value of the TEC obtained by inversion and the background TEC can reach 2.0E-07 to 2.5E-07, the difference relative value can reach 4.8E-7 to 8.6E-7 percent, the RMS can reach about 3E-7 TECUs, and the relative RMS can reach 6E-07 to 8.5E-7 percent, so that the TEC inversion technology based on the triple-frequency technology has very high precision, the calculation errors are removed by the algorithm, and the TEC obtained by inversion is consistent with the background TEC. In actual observation, under the observation conditions of the conventional receiving instrument, the phase of the received signal has an observation error of 3 ° to 6 °, which corresponds to a phase capture error of 1/120 weeks to 1/60 weeks. The electric wave signal is a sine wave, and has a phase change of 2 pi after one circle of propagation, namely, the observation error can cause a phase error of pi/60 to pi/30. Therefore, the phase errors of Gaussian distribution of 1 degree, 3 degrees and 6 degrees are added into the simulated signal phase, the receiving error of the signal is simulated, and the inversion result of the three-frequency technology added with the white Gaussian noise error is obtained. As shown in FIG. 3, the difference between the inverted TEC value and the background TEC is below 1 TECU, and the effect is good.

2.3 simulation calculation result of thirteen measuring stations

The earthquake bureau of China deploys 13 ground survey stations in the western region of China in total to receive the three-frequency beacon signals, the three-frequency beacon signals are approximately distributed from the northwest to the southwest, mainly in the earthquake high-occurrence region of China, and the high-precision ionosphere information is hoped to be used for researching earthquake precursors and ionosphere changes caused by earthquakes. These 13 stations are: a big theory station, a solid original station, a cooperation station, a Maqu station, a salt pond station, a Yuxi station, a Zhaotong station, a Zhongwei station, a Tianshui station, a Honghe station, a Pu' er station, a shrimp puller station and a Mianyang station. The specific distribution diagram is shown in fig. 5.

The method is the same as the processing method of 4 experimental stations, firstly, the relative TEC is obtained by utilizing a simulated Doppler frequency shift method, and then the high-precision tri-band TEC is obtained by utilizing the combination of the accurate Doppler phase shift decimal part and the estimated phase integration constant. Statistics of the inversion results of the three-band TEC of 13 stations are shown in fig. 6 and 7, and it can be seen from the figures that: when the observation error is 3 degrees, the relative error average value calculated by the TEC is within 2.5 percent, and the relative error RMS is within 3 percent; when the observed error is 6 degrees, the relative error mean value calculated by the TEC is within 4.5 percent, and the relative error RMS is within 6 percent. The accuracy of the ionized layer TEC inverted by the triple-frequency beacon technology is high.

In summary, the invention simulates the doppler shift generated by the electric wave signal passing through the ionosphere by using a simulation method, and realizes the technology of inverting the high-precision ionosphere TEC by using triple-frequency beacon doppler by using a program. By comparing the double-frequency inversion results, the effect of the triple-frequency beacon technology on improving the inversion accuracy of the ionized layer TEC is found to be remarkable. The influence of the observation error on the triple-frequency beacon technology is obviously larger than that on the double-frequency technology, and the observation error is mainly because the double-frequency phase integral constant is smaller, and the triple-frequency phase integral constant is improved by more than 60 times compared with the double-frequency phase integral constant, so that the precision of the observation quantity directly influences the precision of triple-frequency inversion. Therefore, the popularization of the tri-band technology also requires the support of the related observation technology and instruments. At present, the observation precision of a related instrument can reach approximately 3 degrees to 6 degrees of gauss, and the calculation result according to the invention can meet the requirement.

Based on the method, the invention also provides a system for verifying the inversion accuracy of the tri-band beacon TEC based on data simulation, which comprises the following steps: one or more processors; storage means for storing one or more programs; when executed by the one or more processors, cause the one or more processors to implement the above-described method for verifying inversion accuracy of a triple-band beacon TEC based on data simulation. Since the hardware part of the system belongs to the conventional technology in the field, the detailed description is not repeated here.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention in any way, and it will be apparent to those skilled in the art that the above description of the present invention can be applied to various modifications, equivalent variations or modifications without departing from the spirit and scope of the present invention.