CN113671536A - Channel simulator-based ionized layer CT simulation system and method for three-frequency beacon receiver chain - Google Patents
Channel simulator-based ionized layer CT simulation system and method for three-frequency beacon receiver chain Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
- G01S19/07—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing data for correcting measured positioning data, e.g. DGPS [differential GPS] or ionosphere corrections
- G01S19/072—Ionosphere corrections
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/35—Constructional details or hardware or software details of the signal processing chain
- G01S19/37—Hardware or software details of the signal processing chain
Abstract
The invention discloses a triple-frequency beacon receiver chain ionosphere CT simulation system and a triple-frequency beacon receiver chain ionosphere CT simulation method based on a channel simulator. The simulation method disclosed by the invention is used for carrying out inversion calculation on the two-dimensional distribution of the ionosphere electron density along with the latitude and the height in the region based on the ionosphere CT algorithm, is used for simulation verification of the ionosphere CT algorithm of the satellite-ground link three-frequency beacon receiver station chain, and lays a foundation for designing and applying a low-orbit spacecraft-based satellite-borne three-frequency beacon measurement system.
Description
Technical Field
The invention belongs to the technical field of ionosphere CT simulation, and particularly relates to a channel simulator-based ionosphere CT simulation system and method for a station chain of a tri-band beacon receiver.
Background
The ionosphere CT algorithm principle of the satellite beacon receiver station chain is as follows: and when the satellite passes the border each time, a plurality of beacon receivers of the station chain synchronously receive and measure the coherent beacon differential Doppler phase transmitted by the satellite-borne system to obtain the ionized layer electron density integral (TEC) along a large number of mutually crossed propagation paths in the detection area, and the acquired data is analyzed and inverted based on the CT technology to obtain the two-dimensional distribution of the ionized layer electron density along the latitude and the height.
The coherent beacon receiving and measuring the ionized layer TEC is based on a differential Doppler technology, the dispersion effect of the ionized layer is utilized, the Doppler frequency shift difference of a dual-frequency or multi-frequency coherent signal is used for eliminating the frequency shift caused by satellite motion, the additional frequency shift related to the ionized layer TEC is reserved, and the ionized layer TEC value can be obtained through conversion.
Early typical ionospheric sounding beacons were carried on the naval meridian Satellite Navigation System (NNSS). The dual-frequency beacon transmitter carried by the NNSS satellite transmits dual-frequency coherent signals with carrier frequencies of 150MHz and 400 MHz. And a receiver arranged on the ground receives the satellite beacon signal, and the ionosphere TEC measurement can be realized by utilizing a differential Doppler frequency shift technology. Subsequently, the united states, russia, etc. have transmitted successively OSCAR, RADCAL, DMSP F15, COSMOS, etc. satellites, all of which carry coherent beacon transmitters. Since the 20 th century, the united states transmitted the constellation of cosinc satellites, with 6 small satellites carrying a coherent beacon transmitter, a masker receiver, and a small photometer. Wherein the coherent beacon transmitter is used as a scintillation measurement of the ionosphere TEC and coherent frequency point signals along the satellite-ground link. Due to the success of the cosinc satellite program, the united states transmitted 6 again cosic-II low-orbit equatorial moonlets in 2019, with the main payload including a triple-band beacon transmitter, a masker receiver, and an ion drift rate meter.
The three-frequency beacon measuring system consists of a satellite-borne subsystem and a ground subsystem. A three-frequency beacon transmitter of the satellite-borne subsystem transmits a group of phase-coherent VHF, UHF and L frequency band signals to the ground, and large-range rapid scanning of an ionosphere is realized along with the movement of a satellite. The triple-frequency beacon receiver of the ground subsystem tracks and receives triple-frequency coherent signals transmitted by a satellite through an antenna, processes the triple-frequency coherent signals to obtain the ionized layer TEC of the satellite-ground link, and transmits the ionized layer TEC to a data processing center through a network. The data processing center jointly utilizes the ionized layer TECs of each tri-band beacon receiver station network to realize the reconstruction of the electron density of the ionized layer in a large range based on the CT technology. The data product of the three-frequency beacon measurement can serve the fields of earthquake electromagnetic monitoring, space environment monitoring and early warning and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a channel simulator-based ionized layer CT simulation system and method for a tri-band beacon receiver chain.
The invention adopts the following technical scheme:
the improvement of a three-frequency beacon receiver chain ionosphere CT simulation system based on a channel simulator is as follows: the system comprises a tri-band beacon transmitter, a signal input adapter, an ionosphere scene setting terminal, a channel simulator, a tri-band beacon receiver chain, a receiver chain TEC processing module and a CT inversion module, wherein the signal input adapter is connected with the tri-band beacon transmitter and the channel simulator, the ionosphere scene setting terminal is connected with the channel simulator, the tri-band beacon receiver chain comprises at least 3 tri-band beacon receivers, the input end of each tri-band beacon receiver is connected with the channel simulator, the output end of each tri-band beacon receiver is connected with the receiver chain TEC processing module, and the receiver chain TEC processing module is connected with the CT inversion module.
Furthermore, the three-frequency beacon transmitter outputs two paths of I/Q single carrier signals with orthogonality of VHF, UHF and L frequency points, the signal input adapter converts the two paths of I/Q orthogonal signals of the VHF, UHF and L frequency points into input signals of a channel simulator, the ionosphere scene setting terminal simulates and calculates the amplitude and phase of the signals of the three-frequency beacon transmitter, the amplitude and phase of the signals of the three-frequency beacon transmitter change through ionosphere propagation, the channel simulator is used for simulating a multi-channel ground-to-air link, simulated channel parameters comprise fading, attenuation, delay, Doppler frequency shift and noise, all three-frequency beacon receivers of a station chain of the three-frequency beacon receiver are distributed along a meridian circle, and all the three-frequency beacon receivers output a continuous sequence of I/Q components of a multi-frequency point coherent signal; and the receiver station chain TEC processing module and the CT inversion module are used for performing inversion calculation on the two-dimensional distribution of the electron density of the region along with the latitude and the height.
The ionosphere CT simulation method of the tri-band beacon receiver chain based on the channel simulator uses the simulation system, and the improvement is that the method comprises the following steps:
setting a calculation scene, including observation time, the position of a station chain of a tri-frequency beacon receiver, a TLE (satellite tracking index) ephemeris file of a low-orbit satellite and a cut-off elevation angle observed by a visible satellite;
calculating the satellite position corresponding to the observation time, the elevation angle and the azimuth angle observed by the satellite, considering the satellite to be visible when the observation elevation angle is higher than the cut-off elevation angle of the visible satellite, calculating the ionized layer TEC value in the satellite visible period of each time and the influence of the ionized layer TEC value on the amplitude and the phase of the VHF, UHF and L frequency point signals received by each tri-band beacon receiver when the ionized layer passes through the ionized layer to reach the ground, writing the influence of the ionized layer on the amplitude and the phase of different frequency point signals into a text file, and using the text file as a channel parameter input file of a channel simulator;
calling a receiver station chain TEC processing module, reading a continuous sequence of the multi-frequency point coherent signal I, Q components after differential processing of each tri-frequency beacon receiver, calculating to obtain the amplitude and phase of each frequency band signal, correcting and connecting the phases after differential processing to obtain a continuous phase curve, and further converting the continuous phase curve into an overhead observation TEC time sequence of each tri-frequency beacon receiver;
and 5, calling the observation TEC time sequence over each tri-frequency beacon receiver by the CT inversion module, and performing inversion calculation on the two-dimensional distribution of the electron density of the ionized layer in the region along with the latitude and the height based on the ionized layer CT algorithm.
Further, in step 2, inputting a satellite position sequence, positions of the three-frequency beacon receivers and observation time in a satellite visible period into an ionosphere empirical model NeQuick, calculating to obtain an electron density value on a satellite-ground link, integrating according to an observation path to obtain an ionosphere TEC time sequence of the satellite-ground link, wherein a channel simulator doppler frequency shift calculation formula is as follows:
where f denotes the signal frequency, c the speed of light, n the atmospheric refractive index,
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
representing the difference over time, NeAnd representing the electron density on a signal propagation path, calculating to obtain Doppler frequency shift values of three frequency points, writing the signal amplitude attenuation and the Doppler frequency shift of the three frequency points into text files respectively, and using the text files as channel parameter input files of a channel simulator.
Further, in step 4, the amplitude P and phase Φ of the signal are calculated by:
P＝10×lg(I2+Q2) (2)
Φ＝tan-1(Q/I) (3)
where I and Q represent the in-phase and quadrature components of the coherent signal, respectively.
The invention has the beneficial effects that:
the simulation method disclosed by the invention is used for building a three-frequency beacon receiver chain ionosphere CT simulation system based on a channel simulator, simulating a satellite signal which is received and measured by a three-frequency beacon receiver chain on the ground, calculating two-dimensional distribution of regional ionosphere electron density along with latitude and height based on an ionosphere CT algorithm in an inversion way, and laying a foundation for designing and applying a low-orbit spacecraft-based satellite-borne three-frequency beacon measurement system.
Drawings
FIG. 1 is a block diagram of the components of the disclosed simulation system;
FIG. 2 is a schematic flow chart of a disclosed simulation method;
FIG. 3 is the elevation and azimuth of the horse side station observations during the satellite transit of example 1;
FIG. 4 is an ionized layer TEC time sequence of the satellite-ground link in the embodiment 1;
FIG. 5 is a Doppler shift of a VHF frequency band signal in example 1;
FIG. 6 is the sequence of the I/Q components of the VHF frequency points of the smart home station in example 1;
FIG. 7 is a relative TEC time sequence over the station in example 1;
FIG. 8 shows the ionospheric CT algorithm results of example 1;
FIG. 9 is the elevation and azimuth of the horse side station observations during the satellite transit of example 2;
FIG. 10 is an embodiment 2 ionized layer TEC time sequence of satellite-ground link;
FIG. 11 is a Doppler shift of a VHF frequency band signal in example 2;
FIG. 12 is a relative TEC time sequence over the station in example 2;
fig. 13 shows the ionospheric CT algorithm results of example 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the invention discloses a triple-band beacon receiver station chain ionosphere CT simulation system based on a channel simulator, which comprises a triple-band beacon transmitter, a signal input adapter, an ionosphere scene setting terminal, a channel simulator, a triple-band beacon receiver station chain, a receiver station chain TEC processing module and a CT inversion module, wherein the signal input adapter is connected with the triple-band beacon transmitter and the channel simulator, the ionosphere scene setting terminal is connected with the channel simulator, the triple-band beacon receiver station chain comprises at least 3 triple-band beacon receivers, the input end of each triple-band beacon receiver is respectively connected with the channel simulator, the output end of each triple-band beacon receiver is respectively connected with the receiver station chain TEC processing module, and the receiver station chain TEC processing module is connected with the CT inversion module.
The three-frequency beacon transmitter outputs two paths of orthogonal single carrier signals of the I/Q of the VHF (150MHz), UHF (400MHz) and L (1067MHz) frequency points, and the signal input adapter converts the two paths of orthogonal signals of the I/Q of the VHF, UHF and L frequency point beacons into input signals of the channel simulator. The ionosphere scene setting terminal simulates and calculates the effect of the three-frequency beacon transmitter signals transmitted through the ionosphere, namely simulates the change of the amplitude and the phase of the satellite-borne three-frequency beacon transmitter signals received by different stations through the ionosphere. The channel simulator is a key component of the simulation system, is used for simulating a multi-channel ground-air link, the simulated channel parameters comprise information such as fading, attenuation, delay, Doppler shift, noise and the like, and the carrier signals received by the tri-frequency beacon receivers at different positions can be simulated by independently loading the set channel parameters to different channels. Each tri-band beacon receiver of a tri-band beacon receiver station chain used for ionosphere CT simulation is generally distributed along a meridian, and each tri-band beacon receiver outputs a continuous sequence of I/Q components of a multi-frequency point coherent signal; and the receiver station chain TEC processing module and the CT inversion module are used for performing inversion calculation on the two-dimensional distribution of the electron density of the region along with the latitude and the height.
As shown in fig. 2, the invention also discloses a channel simulator-based ionosphere CT simulation method for a triple-frequency beacon receiver chain, which uses the simulation system and comprises the following steps:
setting a calculation scene, including observation time, the position of a station chain of a tri-frequency beacon receiver, a TLE (satellite tracking index) ephemeris file of a low-orbit satellite and a cut-off elevation angle observed by a visible satellite;
calculating the satellite position corresponding to the observation time, the elevation angle and the azimuth angle observed by the satellite, considering that the satellite is visible when the observation elevation angle is higher than the cut-off elevation angle of the visible satellite, calculating the ionized layer TEC value in the visible (transit) period of the satellite each time, and the influence of the ionized layer TEC value on the amplitude and the phase of the VHF, UHF and L frequency point beacon signals received by each tri-band beacon receiver when the ionized layer passes through the ionized layer to reach the ground, writing the influence of the ionized layer on the amplitude and the phase of the beacon signals with different frequency points into a text file, and using the text file as a channel parameter input file of a channel simulator;
calling a receiver station chain TEC processing module, reading a continuous sequence of multi-frequency point coherent signal I, Q components of the tri-frequency beacon receiver of each station, and calculating to obtain the amplitude and the phase of each frequency band signal, wherein an intermediate frequency processing unit of the tri-frequency beacon receiver performs differential processing on phase data, and outputs the I, Q information after the difference, so that the calculated phase is the phase after the difference.
Correcting and connecting the phases after the difference to obtain a continuous phase curve, and further converting the continuous phase curve into an observation TEC time sequence over the three-frequency beacon receiver of each station;
and 5, calling the observation TEC time sequence above the tri-band beacon receiver of each station by the CT inversion module, and performing inversion calculation on the two-dimensional distribution of the electron density of the ionized layer in the region along with the latitude and the height based on the ionized layer CT algorithm.
The embodiment 1 discloses a channel simulator-based ionosphere CT simulation method for a triple-frequency beacon receiver chain, which uses the simulation system and comprises the following steps:
step 2: setting a calculation scene, including observation time, a receiver station chain position, a TLE ephemeris file of a low orbit satellite and a cut-off elevation angle observed by a visible satellite, calculating the electron density distribution of an ionized layer during the satellite transit period, obtaining the ionized layer TEC value of a satellite-ground link through integration, further converting the ionized layer TEC value into amplitude attenuation and Doppler frequency shift of VHF, UHF and L frequency point beacon signals received by each tri-frequency beacon receiver when the beacon signals pass through the ionized layer and reach the ground, writing the amplitude attenuation and Doppler frequency shift into a text file, and using the text file as a channel parameter input file of a channel simulator.
In this embodiment, the observation time is 06-07UT at 7 days 1 month 2015, the station chain of the triple-frequency beacon receiver is located at horse side (28.84 ° N, 120.87 ° E), skilful home (26.92 ° N, 120.25 ° E), kunming (25.14 ° N, 120.07 ° E), yunjiang (23.6 ° N, 118.32 ° E), and the cut-off elevation angle of the observation satellite is 5 °. The transit time of the satellite over the four stations is calculated to be 06:09:38.16-06:18:42.98, 06:10:9.42-06:19:13.7, 06:10:37.34-06:19:41.1, 06:11:6.06-06:20:9.14 respectively. Figure 3 shows the elevation (up) and azimuth (down) of the horse-side station observations during satellite transit.
Inputting a satellite position sequence during the satellite transit period, positions of all three-frequency beacon receivers, observation time and the like into an ionosphere empirical model NeQuick, calculating to obtain an electron density value on a satellite-ground link, and integrating according to an observation path to obtain the ionosphere TEC time sequence of the satellite-ground link shown in figure 4.
The channel parameters that can be simulated by the channel simulator include information such as fading, attenuation, delay, doppler shift, noise, etc. Here, TEC measurement is mainly based on differential doppler technology, so the input parameters of the channel simulator mainly include doppler shift, and its calculation formula is as follows:
where f denotes the signal frequency, c the speed of light, n the atmospheric refractive index,
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
representing the difference over time, NeThe electron density on the signal propagation path is represented, the doppler shift values of three frequency points are obtained by calculation, and the doppler shift of the VHF frequency point signal is shown in fig. 5.
Here, the amplitude attenuation of VHF, UHF and L frequency points is taken as 17dB, 10dB and 2dB, respectively, without considering the attenuation of the signal amplitude for the first time. To mark the end of the input signal, the last bit value of the amplitude attenuation of the three frequency points is taken as 70 dB.
And respectively writing the signal amplitude attenuation and the Doppler frequency shift of the three frequency points into text files to be used as channel parameter input files of the channel simulator.
And step 3: and (3) starting a tri-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step (2) into the channel simulator, and simultaneously receiving tri-frequency beacon signals output by the channel simulator by a tri-frequency beacon receiver chain to generate files, wherein continuous sequences of I/Q components of the multi-frequency point coherent signals are respectively recorded. Fig. 6 shows the sequence of the I/Q components of the VHF frequency point of the smart station.
And 4, step 4: and calling a receiver station chain TEC processing module, reading a continuous sequence of the multi-frequency point coherent signal I, Q components of the tri-frequency beacon receiver of each station, and calculating an observation TEC time sequence over the tri-frequency beacon receiver of each station.
And calling a TEC processing module of a station chain of the receiver to read the continuous sequence of the multi-frequency point coherent signal I, Q components of the tri-frequency beacon receiver of each station. The intermediate frequency processing unit of the tri-band beacon receiver performs differential processing on the phase data, and outputs the I, Q information after differential processing. The amplitude P and phase Φ of the signal are calculated by:
P＝10×lg(I2+Q2) (2)
Φ＝tan-1(Q/I) (3)
where I and Q represent the in-phase and quadrature components of the coherent beacon signal, respectively. And carrying out phase connection on the signal phases to obtain a continuous phase curve. Further translated into an observed TEC time series over the station as shown in fig. 7.
And 5: and (3) reading the observation TEC time sequence over the tri-band beacon receiver of each station by a CT inversion module, reading the position sequence of the satellite in the transit period calculated in the step (2), and performing inversion calculation on the two-dimensional distribution of the electron density of the ionosphere in the region along with the latitude and the height based on an ionosphere CT algorithm. The ionospheric CT algorithm may refer to "ionospheric feature parameter reconstruction technique research based on satellite signals" (ouming, doctor paper, university of wuhan, 2017). The ionospheric CT algorithm results are shown in fig. 8.
The embodiment 2 discloses a channel simulator-based ionosphere CT simulation method for a triple-frequency beacon receiver chain, which uses the simulation system and comprises the following steps:
Inputting the satellite position sequence, the positions of all three-frequency beacon receivers, observation time and the like in the satellite transit period into an ionosphere empirical model NeQuick, calculating to obtain an electron density value on a satellite-ground link, and integrating according to an observation path to obtain the ionosphere TEC time sequence of the satellite-ground link shown in figure 10.
Amplitude attenuation and Doppler frequency shift of the VHF, UHF and L frequency point beacon signals received by the three-frequency beacon receiver when passing through the ionosphere and reaching the ground are further calculated, and the Doppler frequency shift of the VHF frequency point signals is shown in figure 11. The attenuation of the amplitude of the tri-band signal is 17dB, 10dB and 2dB as in example 1, and the final value of the amplitude attenuation is 70 dB. And respectively writing the signal amplitude attenuation and the Doppler frequency shift of the three frequency points into text files to be used as channel parameter input files of the channel simulator.
And 3, starting the triple-frequency beacon transmitter for preheating for 15 minutes, inputting the file generated in the step 2 into the channel simulator, and simultaneously receiving triple-frequency beacon signals output by the channel simulator by the triple-frequency beacon receiver chain to generate files and respectively record continuous sequences of I/Q components of the multi-frequency point coherent signals.
And 5, reading the time sequence of the observation TEC in the sky of the tri-band beacon receiver of each station by a CT inversion module, reading the position sequence of the satellite in the transit period calculated in the step 2, and performing inversion calculation on the two-dimensional distribution of the electron density of the ionized layer in the region along with the latitude and the height based on the ionized layer CT algorithm, wherein the result is shown in FIG. 13.
Claims (5)
1. A three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator is characterized in that: the system comprises a tri-band beacon transmitter, a signal input adapter, an ionosphere scene setting terminal, a channel simulator, a tri-band beacon receiver chain, a receiver chain TEC processing module and a CT inversion module, wherein the signal input adapter is connected with the tri-band beacon transmitter and the channel simulator, the ionosphere scene setting terminal is connected with the channel simulator, the tri-band beacon receiver chain comprises at least 3 tri-band beacon receivers, the input end of each tri-band beacon receiver is connected with the channel simulator, the output end of each tri-band beacon receiver is connected with the receiver chain TEC processing module, and the receiver chain TEC processing module is connected with the CT inversion module.
2. The ionospheric CT simulation system of a triple-band beacon receiver chain based on a channel simulator of claim 1, wherein: the method comprises the steps that a three-frequency beacon transmitter outputs two paths of I/Q single carrier signals with orthogonality of VHF, UHF and L frequency points, a signal input adapter converts the two paths of I/Q orthogonal signals of the VHF, UHF and L frequency points into input signals of a channel simulator, an ionosphere scene setting terminal simulates and calculates changes generated by the amplitude and phase of the signals of the three-frequency beacon transmitter through ionosphere propagation, the channel simulator is used for simulating a multi-channel ground-to-air link, simulated channel parameters comprise fading, attenuation, delay, Doppler frequency shift and noise, three-frequency beacon receivers of a three-frequency beacon receiver chain are distributed along a sub-circle, and each three-frequency beacon receiver outputs a continuous sequence of I/Q components of a multi-frequency point coherent signal; and the receiver station chain TEC processing module and the CT inversion module are used for performing inversion calculation on the two-dimensional distribution of the electron density of the region along with the latitude and the height.
3. A channel simulator-based ionosphere CT simulation method of a tri-band beacon receiver chain, which uses the simulation system of claim 1, and is characterized by comprising the following steps:
step 1, building a three-frequency beacon receiver chain ionosphere CT simulation system based on a channel simulator;
step 2, setting a calculation scene, generating a channel parameter input file of a channel simulator, and simulating the changes of signal amplitudes and phases of different links through ionosphere propagation;
setting a calculation scene, including observation time, the position of a station chain of a tri-frequency beacon receiver, a TLE (satellite tracking index) ephemeris file of a low-orbit satellite and a cut-off elevation angle observed by a visible satellite;
calculating the satellite position corresponding to the observation time, the elevation angle and the azimuth angle observed by the satellite, considering the satellite to be visible when the observation elevation angle is higher than the cut-off elevation angle of the visible satellite, calculating the ionized layer TEC value in the satellite visible period of each time and the influence of the ionized layer TEC value on the amplitude and the phase of the VHF, UHF and L frequency point signals received by each tri-band beacon receiver when the ionized layer passes through the ionized layer to reach the ground, writing the influence of the ionized layer on the amplitude and the phase of different frequency point signals into a text file, and using the text file as a channel parameter input file of a channel simulator;
step 3, starting up the tri-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step 2 into the channel simulator, simultaneously tracking and capturing beacon signals by each tri-frequency beacon receiver, and outputting a continuous sequence of components of the multi-frequency point coherent signal I, Q;
step 4, calling a receiver station chain TEC processing module, reading a continuous sequence of multi-frequency point coherent signal I, Q components of each tri-frequency beacon receiver, and calculating an overhead observation TEC time sequence of each tri-frequency beacon receiver;
calling a receiver station chain TEC processing module, reading a continuous sequence of the multi-frequency point coherent signal I, Q components after differential processing of each tri-frequency beacon receiver, calculating to obtain the amplitude and phase of each frequency band signal, correcting and connecting the phases after differential processing to obtain a continuous phase curve, and further converting the continuous phase curve into an overhead observation TEC time sequence of each tri-frequency beacon receiver;
and 5, calling the observation TEC time sequence over each tri-frequency beacon receiver by the CT inversion module, and performing inversion calculation on the two-dimensional distribution of the electron density of the ionized layer in the region along with the latitude and the height based on the ionized layer CT algorithm.
4. The ionospheric CT simulation method of a triple-band beacon receiver chain based on a channel simulator as claimed in claim 3, wherein: in step 2, a satellite position sequence, positions of all three-frequency beacon receivers and observation time in a satellite visible period are input into an ionosphere empirical model NeQuick, an electron density value on a satellite-ground link is obtained through calculation, integration is carried out according to an observation path, an ionosphere TEC time sequence of the satellite-ground link is obtained, and a Doppler frequency shift calculation formula of a channel simulator is as follows:
where f denotes the signal frequency, c the speed of light, n the atmospheric refractive index,
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
the difference of the time is expressed, Ne expresses the electron density on the signal propagation path, Doppler frequency shift values of three frequency points are obtained through calculation, and the signal amplitude attenuation and the Doppler frequency shift of the three frequency points are written into text files respectively to be used as channel parameter input files of a channel simulator.
5. The ionospheric CT simulation method of a triple-band beacon receiver chain based on a channel simulator as claimed in claim 3, wherein: in step 4, the amplitude P and phase Φ of the signal are calculated from:
P＝10×lg(I2+Q2) (2)
Φ＝tan-1(Q/I) (3)
where I and Q represent the in-phase and quadrature components of the coherent signal, respectively.
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