CN113671536B - Three-frequency beacon receiver station chain ionosphere CT simulation system and simulation method based on channel simulator - Google Patents
Three-frequency beacon receiver station chain ionosphere CT simulation system and simulation method based on channel simulator 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
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Abstract
The invention discloses a three-frequency beacon receiver station chain ionosphere CT simulation system and a simulation method based on a channel simulator. The simulation method disclosed by the invention is used for simulating and verifying the ionosphere CT algorithm of the satellite-ground link three-frequency beacon receiver station chain based on the two-dimensional distribution of the ionosphere electron density of the region along with the latitude and the height calculated based on the ionosphere CT algorithm inversion, and lays a foundation for designing and applying a satellite-borne three-frequency beacon measuring system based on a low-orbit spacecraft.
Description
Technical Field
The invention belongs to the technical field of ionosphere CT simulation, and particularly relates to a three-frequency beacon receiver station chain ionosphere CT simulation system and a simulation method based on a channel simulator, which can simulate the amplitude and the phase of a satellite-borne three-frequency beacon signal when the satellite-borne three-frequency beacon signal reaches the ground through ionosphere propagation and is linked by a three-frequency beacon receiver station, the two-dimensional distribution of regional ionosphere electron density along the latitude and the height can be obtained through the amplitude and the phase, and the simulation verification of the three-frequency beacon receiver station chain ionosphere CT algorithm is carried out.
Background
The ionosphere CT algorithm principle of the satellite beacon receiver station chain is as follows: and when the satellite passes through, a plurality of beacon receivers of the station chain synchronously receive and measure the differential Doppler phases of the coherent beacons transmitted by the satellite-borne system to obtain ionosphere electron density integrals (TECs) along a large number of mutually crossed propagation paths in a detection area, and the acquired data are analyzed and inverted based on a CT technology to obtain two-dimensional distribution of the ionosphere electron density along the latitude and the height.
The method is characterized in that 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 the dual-frequency or multi-frequency coherent signals is utilized to eliminate 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 ionospheric probe beacons were typically carried on the united states navy meridian satellite navigation system (Navy Navigation Satellite System, NNSS). The NNSS satellite-mounted double-frequency beacon transmitter transmits double-frequency coherent signals with carrier frequencies of 150MHz and 400 MHz. And a receiver arranged on the ground receives the satellite beacon signal, and ionosphere TEC measurement can be realized by utilizing a differential Doppler frequency shift technology. Subsequently, the united states, russia, etc. have successively transmitted OSCAR, RADCAL, DMSP F15, COSMOS, etc. satellites, each of which has a coherent beacon transmitter mounted thereon. In the 20 th century, the united states transmitted a COSMIC satellite constellation, with 6 satellites carrying a coherent beacon transmitter, a occultation receiver, and a compact photometer. Wherein the coherent beacon transmitter is used as a scintillation measurement of ionosphere TEC and coherent frequency point signals along the star-to-ground link. With the success of the COSMIC satellite program, 6 COSMIC-II low-orbit equatorial satellites were again transmitted in the united states in 2019, and the main payload included a three-frequency beacon transmitter, a occultation receiver, and an ion drift rate meter.
The three-frequency beacon measurement system consists of a satellite-borne subsystem and a ground subsystem. The 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 the satellite-borne subsystem realizes large-range rapid scanning of the ionosphere along with the movement of the satellite. The three-frequency beacon receiver of the ground subsystem tracks and receives the three-frequency coherent signals transmitted by the satellite through an antenna, processes the signals to obtain an ionosphere TEC of a satellite-ground link, and transmits the ionosphere TEC to a data processing center through a network. The data processing center jointly utilizes the ionized layer TEC of each three-frequency beacon receiver station network, and realizes large-scale ionized layer electron density reconstruction based on CT technology. The data product of the three-frequency beacon measurement can be used for 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 three-frequency beacon receiver station chain ionosphere CT simulation system and a simulation method based on a channel simulator.
The invention adopts the following technical scheme:
in a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator, the improvement comprising: the system comprises a three-frequency beacon transmitter, a signal input adapter, an ionosphere scene setting terminal, a channel simulator, three-frequency beacon receiver station chains, a receiver station chain TEC processing module and a CT inversion module, wherein the signal input adapter is connected with the three-frequency beacon transmitter and the channel simulator, the ionosphere scene setting terminal is connected with the channel simulator, the three-frequency beacon receiver station chains comprise at least 3 three-frequency beacon receivers, the input ends of the three-frequency beacon receivers are respectively connected with the channel simulator, the output ends of the three-frequency beacon receivers are 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.
Further, the three-frequency beacon transmitter outputs two paths of single carrier signals with orthogonality of I/Q of VHF, UHF and L frequency points, the signal input adapter converts the two paths of orthogonal signals of the I/Q of the VHF, UHF and L frequency points into input signals of the channel simulator, the ionosphere scene setting terminal simulates and calculates the change 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 multichannel ground-air link, the simulated channel parameters comprise fading, attenuation, delay, doppler shift and noise, each three-frequency beacon receiver of the three-frequency beacon receiver station chain is distributed along a meridian, and each three-frequency beacon receiver outputs a continuous sequence of I/Q components of coherent signals of the multiple frequency points; the receiver station chain TEC processing module and the CT inversion module are used for inverting and calculating the two-dimensional distribution of the electron density of the region along with the latitude and the height.
The three-frequency beacon receiver station chain ionosphere CT simulation method based on the channel simulator uses the simulation system, and the improvement is that the method comprises the following steps:
step 1, constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator;
step 2, given a calculation scene, generating a channel parameter input file of a channel simulator, and simulating the changes generated by the propagation of signal amplitudes and phases of different links through an ionosphere;
giving a calculation scene comprising the time of observation, the position of a station chain of a three-frequency beacon receiver, a TLE ephemeris file of a low-orbit satellite and a cut-off elevation angle of visible satellite observation;
calculating satellite positions corresponding to observation time, elevation angles and azimuth angles of satellite observation, when the observation elevation angles are higher than the cut-off elevation angles of visible satellites, considering that the satellites are visible, calculating ionosphere TEC values in each satellite visible period, and the influence of the ionosphere TEC values on the amplitudes and phases of VHF, UHF and L frequency point signals received by each three-frequency beacon receiver when the signals pass through the ionosphere to reach the ground, writing the influence of the ionosphere on the amplitudes and phases of different frequency point signals into a text file as a channel parameter input file of a channel simulator;
step 3, starting up the three-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step 2 into a channel simulator, simultaneously tracking and capturing beacon signals by all three-frequency beacon receivers, and outputting a continuous sequence of components of the multi-frequency coherent signal I, Q;
step 4, calling a receiver station chain TEC processing module, reading continuous sequences of components of the multi-frequency-point coherent signals I, Q of each three-frequency beacon receiver, and calculating an observation TEC time sequence above each three-frequency beacon receiver;
invoking a receiver station chain TEC processing module, reading a continuous sequence of components of the multi-frequency-point coherent signal I, Q subjected to differential processing by each three-frequency beacon receiver, calculating to obtain the amplitude and the phase of each frequency band signal, correcting and connecting the phases subjected to differential processing to obtain a continuous phase curve, and further converting the continuous phase curve into an observation TEC time sequence above each three-frequency beacon receiver;
and 5, the CT inversion module calls the time sequence of the observation TEC above each three-frequency beacon receiver, and inverts and calculates the two-dimensional distribution of the ionosphere electron density of the region along with the latitude and the height based on an ionosphere CT algorithm.
Further, in step 2, the satellite position sequence during the satellite visible period, the positions of each tri-frequency beacon receiver and the observation time are input into an ionosphere empirical model NeQuick, the electron density value on the satellite-ground link is obtained through calculation, the ionosphere TEC time sequence of the satellite-ground link is obtained through integration according to the observation path, and the calculation formula of the Doppler frequency shift of the channel simulator is as follows:
wherein f represents the signal frequency, c is the speed of light, n represents the refractive index of the atmosphere,ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>Representing the difference over time, N e The electron density on the signal propagation path is represented, doppler frequency shift values of three frequency points are obtained through calculation, the signal amplitude attenuation and Doppler frequency shift of the three frequency points are written into text files respectively and are used as channel parameter input of a channel simulatorAnd (5) entering a file.
Further, in step 4, the amplitude P and phase Φ of the signal are calculated by:
P＝10×lg(I 2 +Q 2 ) (2)
Φ＝tan -1 (Q/I) (3)
where I and Q represent in-phase and quadrature components, respectively, of the coherent signal.
The beneficial effects of the invention are as follows:
the simulation method disclosed by the invention is used for constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator, simulating satellite signals measured by the three-frequency beacon receiver station chain on the ground, inverting and calculating the two-dimensional distribution of the regional ionosphere electron density along with the latitude and the height based on an ionosphere CT algorithm, and laying a foundation for designing and applying a satellite-borne three-frequency beacon measurement system based on a low-orbit spacecraft.
Drawings
FIG. 1 is a block diagram of the components of the disclosed simulation system;
FIG. 2 is a flow chart of the disclosed simulation method;
FIG. 3 is elevation and azimuth of the MARIZE station observation during a satellite transit of example 1;
FIG. 4 is a time series of example 1 Star-Earth Link ionosphere TEC;
FIG. 5 shows the Doppler shift of the VHF frequency point signal in example 1;
fig. 6 is an I/Q component sequence of VHF frequency points of the smart station in embodiment 1;
FIG. 7 is a relative TEC time series of station overhead in example 1;
FIG. 8 is the ionospheric CT algorithm results of example 1;
FIG. 9 is elevation and azimuth of the Marside station observations during an example 2 satellite transit;
FIG. 10 is a time series of example 2 Star-Earth Link ionosphere TEC;
fig. 11 is a doppler shift of VHF frequency point signals in embodiment 2;
FIG. 12 is a relative TEC time series of station overhead in example 2;
fig. 13 is the ionospheric CT algorithm results of example 2.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, the invention discloses a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator, which comprises a three-frequency beacon transmitter, a signal input adapter, an ionosphere scene setting terminal, a channel simulator, a three-frequency 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 three-frequency beacon transmitter and the channel simulator, the ionosphere scene setting terminal is connected with the channel simulator, the three-frequency beacon receiver station chain comprises at least 3 three-frequency beacon receivers, the input ends of the three-frequency beacon receivers are respectively connected with the channel simulator, the output ends of the three-frequency beacon receivers are 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 I/Q orthogonal single carrier signals of VHF (150 MHz), UHF (400 MHz) and L (1067 MHz) frequency points, and the signal input adapter converts the two paths of I/Q orthogonal signals 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 propagation of the three-frequency beacon transmitter signal through the ionosphere, namely simulates the change generated by the propagation of the amplitude and the phase of the satellite-borne three-frequency beacon transmitter signal received by different stations through the ionosphere. The channel simulator is a key component of the simulation system and is used for simulating a multichannel ground-air link, the simulated channel parameters comprise information such as fading, attenuation, delay, doppler frequency shift, noise and the like, and carrier signals received by three-frequency beacon receivers at different positions can be simulated by independently loading the set channel parameters to different channels. Each tri-frequency beacon receiver of the tri-frequency beacon receiver station chain used as ionospheric CT simulation is typically distributed along a meridian, each tri-frequency beacon receiver outputting a continuous sequence of I/Q components of the multi-frequency point coherent signal; the receiver station chain TEC processing module and the CT inversion module are used for inverting and calculating 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 three-frequency beacon receiver station chain ionosphere CT simulation method based on the channel simulator, which uses the simulation system, and comprises the following steps:
step 1, constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator;
step 2, given a calculation scene, generating a channel parameter input file of a channel simulator, and simulating the changes generated by the propagation of signal amplitudes and phases of different links through an ionosphere by each three-frequency beacon receiver;
giving a calculation scene comprising the time of observation, the position of a station chain of a three-frequency beacon receiver, a TLE ephemeris file of a low-orbit satellite and a cut-off elevation angle of visible satellite observation;
calculating satellite positions corresponding to observation time, elevation angles and azimuth angles of satellite observation, considering that the satellite is visible when the observation elevation angle is higher than the cut-off elevation angle of a visible satellite, calculating the TEC value of an ionized layer in each satellite visible (transit) period, and the influence of the TEC value of the ionized layer on the amplitude and the phase of the VHF, UHF and L frequency point beacon signals received by each three-frequency beacon receiver when the signals pass 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 of different frequency points into a text file as a channel parameter input file of a channel simulator;
step 3, starting up the three-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step 2 into a channel simulator, simultaneously tracking and capturing beacon signals by all three-frequency beacon receivers, and outputting a continuous sequence of components of the multi-frequency coherent signal I, Q;
step 4, calling a receiver station chain TEC processing module, reading continuous sequences of components of the multi-frequency point coherent signals I, Q of the three-frequency beacon receivers of each station, and calculating the time sequence of the observation TEC over the three-frequency beacon receivers of each station;
and calling a receiver station chain TEC processing module, reading a continuous sequence of components of a multi-frequency-point coherent signal I, Q of a three-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 three-frequency beacon receiver has performed differential processing on the phase data, and output I, Q information after differential processing, so that the calculated phase is the phase after differential processing.
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 above a three-frequency beacon receiver of each station;
and 5, the CT inversion module calls an observation TEC time sequence above the three-frequency beacon receiver of each station, and inverts and calculates the two-dimensional distribution of the ionosphere electron density of the region along with the latitude and the height based on an ionosphere CT algorithm.
Embodiment 1, this embodiment discloses a three-frequency beacon receiver station chain ionosphere CT simulation method based on a channel simulator, using the simulation system described above, comprising the steps of:
step 1, constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator;
step 2: given a calculation scene comprising the observed time, the position of a station chain of a receiver, a TLE ephemeris file of a low orbit satellite and a cut-off elevation angle observed by a visible satellite, calculating ionosphere electron density distribution during satellite transit, obtaining ionosphere TEC values of a satellite-ground link through integration, further converting the ionosphere TEC values into amplitude attenuation and Doppler frequency shift of VHF, UHF and L frequency point beacon signals received by each three-frequency beacon receiver when the signals pass through the ionosphere to reach the ground, and writing the amplitude attenuation and Doppler frequency shift into a text file as a channel parameter input file of a channel simulator.
The observation time of this example is 06-07UT at 1 month and 7 days of 2015, and the three-frequency beacon receiver station chain is located at the horse edge (28.84 DEG N,120.87 DEG E), the Qiaojia (26.92 DEG N,120.25 DEG E), the Kunming (25.14 DEG N,120.07 DEG E) and the Yuanjiang (23.6 DEG N,118.32 DEG E), and the cut-off elevation angle of the observation satellite is 5 deg. The calculated satellite transit time of the four station overhead is 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. Fig. 3 shows the elevation (up) and azimuth (down) of the man-side station observations during satellite transit.
The satellite position sequence during the satellite passing period, the positions of the three-frequency beacon receivers, the observation time and the like are input into an ionosphere empirical model Nequick, the electron density value on the satellite-ground link is obtained through calculation, and the satellite-ground link ionosphere TEC time sequence shown in figure 4 is obtained through integration according to the observation path.
Channel parameters that can be modeled by the channel simulator include information such as fading, attenuation, delay, doppler shift, noise, etc. The TEC measurement is mainly based on the differential doppler technique, so the input parameters of the channel simulator mainly include doppler shift, and the calculation formula is as follows:
wherein f represents the signal frequency, c is the speed of light, n represents the refractive index of the atmosphere,ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>Representing the difference over time, N e The Doppler frequency shift values of the three frequency points are calculated by representing the electron density on the signal propagation path, and the Doppler frequency shift of the VHF frequency point signal is given in FIG. 5.
Here, the amplitude attenuation of VHF, UHF, and L frequency points were taken as 17dB, 10dB, and 2dB, respectively, taking the attenuation of the signal amplitude into consideration temporarily. To mark the end of the input signal, the last value of the three-frequency-point amplitude attenuation is taken as 70dB.
And respectively writing the signal amplitude attenuation and Doppler frequency shift of the three frequency points into text files as channel parameter input files of the channel simulator.
Step 3: and (3) starting up the tri-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step (2) into a channel simulator, simultaneously receiving the tri-frequency beacon signals output by the channel simulator by a tri-frequency beacon receiver station chain, generating a file, and respectively recording the continuous sequences of the I/Q components of the multi-frequency point coherent signals. Fig. 6 shows the I/Q component sequence of the smart station VHF frequency points.
Step 4: and calling a receiver station chain TEC processing module, reading the continuous sequence of the components of the multi-frequency-point coherent signal I, Q of the three-frequency beacon receiver of each station, and calculating the time sequence of the observed TEC above the three-frequency beacon receiver of each station.
And calling a receiver station chain TEC processing module, and reading a continuous sequence of components of the multi-frequency point coherent signal I, Q of the three-frequency beacon receiver of each station. The intermediate frequency processing unit of the three-frequency beacon receiver performs differential processing on the phase data, and outputs I, Q information after differential processing. The amplitude P and phase Φ of the signal are calculated from:
P＝10×lg(I 2 +Q 2 ) (2)
Φ＝tan -1 (Q/I) (3)
where I and Q represent in-phase and quadrature components, respectively, of the coherent beacon signal. And (5) phase connecting the signal phases to obtain a continuous phase curve. Further translates into the observed TEC time series over the station as shown in fig. 7.
Step 5: and (3) the CT inversion module reads the time sequence of the observation TEC above the three-frequency beacon receiver of each station, reads the position sequence during the satellite transit period calculated in the step (2), and inverts and calculates the two-dimensional distribution of the regional ionosphere electron density along with the latitude and the height based on an ionosphere CT algorithm. Ionospheric CT algorithms can be referred to in satellite signal based ionospheric feature parameter reconstruction techniques research (ohmming, doctor's paper, university of armed chinese, 2017). The ionospheric CT algorithm results are shown in fig. 8.
Embodiment 2, this embodiment discloses a three-frequency beacon receiver station chain ionosphere CT simulation method based on a channel simulator, using the simulation system described above, comprising the steps of:
step 1, constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator;
step 2, given a computing scenario, the observation time of this embodiment is 2017, 6, 22, 07-08UT, the three-frequency beacon receiver station chain is located at the horse edge (28.84 ° N,103.55 ° E), smart home (26.92 ° N,102.93 ° E), kunming (25.14 ° N,102.75 ° E), and vojiang (23.6 ° N,101 ° E), and the cut-off elevation angle of the observation satellite is 5 °. The calculated satellite transit times over four stations are 07:36:11.44-07:45:18.68, 07:36:42.52-07:45:49.68, 07:37:10.54-07:46:16.9, 07:37:37.98-07:46:46.62, respectively. Fig. 9 shows the elevation (up) and azimuth (down) of the man-side station observations during satellite transit.
The satellite position sequence during the satellite passing period, the positions of the three-frequency beacon receivers, the observation time and the like are input into an ionosphere empirical model Nequick, the electron density value on the satellite-ground link is obtained through calculation, and the satellite-ground link ionosphere TEC time sequence shown in figure 10 is obtained through integration according to the observation path.
Further, the amplitude attenuation and the Doppler shift of the VHF, UHF and L frequency point beacon signals received by each three-frequency beacon receiver when the signals pass through the ionosphere to reach the ground are calculated, and the Doppler shift of the VHF frequency point signals is shown in figure 11. The attenuation of the three-frequency point signal amplitude is taken as 17dB, 10dB and 2dB respectively as in the embodiment 1, and the final value of the amplitude attenuation is taken as 70dB. And respectively writing the signal amplitude attenuation and Doppler frequency shift of the three frequency points into text files as channel parameter input files of the channel simulator.
And step 3, starting up the tri-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step 2 into a channel simulator, simultaneously receiving the tri-frequency beacon signals output by the channel simulator by a tri-frequency beacon receiver station chain, generating a file, and respectively recording the continuous sequences of the I/Q components of the multi-frequency coherent signals.
And 4, calling a receiver station chain TEC processing module, reading continuous sequences of components of the multi-frequency-point coherent signals I, Q of the three-frequency beacon receivers of each station, and calculating an observation TEC time sequence over the three-frequency beacon receivers of each station, wherein the result is shown in figure 12.
And 5, a CT inversion module reads the time sequence of the observation TEC above the three-frequency beacon receiver of each station, reads the position sequence during the satellite transit period calculated in the step 2, and inverts and calculates the two-dimensional distribution of the ionosphere electron density of the region along with the latitude and the height based on an ionosphere CT algorithm, wherein the result is shown in figure 13.
Claims (3)
1. The system comprises a three-frequency beacon transmitter, a signal input adapter, an ionized layer scene setting terminal, a channel simulator, a three-frequency 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 three-frequency beacon transmitter and the channel simulator, the ionized layer scene setting terminal is connected with the channel simulator, the three-frequency beacon receiver station chain comprises at least 3 three-frequency beacon receivers, the input ends of the three-frequency beacon receivers are respectively connected with the channel simulator, the output ends of the three-frequency beacon receivers are 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 single carrier signals with orthogonality of I/Q of VHF, UHF and L frequency points, the signal input adapter converts the two paths of orthogonal signals of the VHF, UHF and L frequency points into input signals of the channel simulator, the ionosphere scene setting terminal simulates and calculates the change 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 multichannel ground-air link, the simulated channel parameters comprise fading, attenuation, delay, doppler shift and noise, each three-frequency beacon receiver of a three-frequency beacon receiver station chain is distributed along a meridian, and each three-frequency beacon receiver outputs a continuous sequence of coherent signal I/Q components of the multiple frequency points; the receiver station chain TEC processing module and the CT inversion module are used for inverting and calculating the two-dimensional distribution of the electron density of the region along with the latitude and the height, and are characterized by comprising the following steps:
step 1, constructing a three-frequency beacon receiver station chain ionosphere CT simulation system based on a channel simulator;
step 2, given a calculation scene, generating a channel parameter input file of a channel simulator, and simulating the changes generated by the propagation of signal amplitudes and phases of different links through an ionosphere;
giving a calculation scene comprising the time of observation, the position of a station chain of a three-frequency beacon receiver, a TLE ephemeris file of a low-orbit satellite and a cut-off elevation angle of visible satellite observation;
calculating satellite positions corresponding to observation time, elevation angles and azimuth angles of satellite observation, when the observation elevation angles are higher than the cut-off elevation angles of visible satellites, considering that the satellites are visible, calculating ionosphere TEC values in each satellite visible period, and the influence of the ionosphere TEC values on the amplitudes and phases of VHF, UHF and L frequency point signals received by each three-frequency beacon receiver when the signals pass through the ionosphere to reach the ground, writing the influence of the ionosphere on the amplitudes and phases of different frequency point signals into a text file as a channel parameter input file of a channel simulator;
taking the last bit value of the amplitude attenuation of the three frequency points as 70dB for marking the end of the input signal;
step 3, starting up the three-frequency beacon transmitter and preheating for 15 minutes, inputting the file generated in the step 2 into a channel simulator, simultaneously tracking and capturing beacon signals by all three-frequency beacon receivers, and outputting a continuous sequence of components of the multi-frequency coherent signal I, Q;
step 4, calling a receiver station chain TEC processing module, reading continuous sequences of components of the multi-frequency-point coherent signals I, Q of each three-frequency beacon receiver, and calculating an observation TEC time sequence above each three-frequency beacon receiver;
invoking a receiver station chain TEC processing module, reading a continuous sequence of components of the multi-frequency-point coherent signal I, Q subjected to differential processing by each three-frequency beacon receiver, calculating to obtain the amplitude and the phase of each frequency band signal, correcting and connecting the phases subjected to differential processing to obtain a continuous phase curve, and further converting the continuous phase curve into an observation TEC time sequence above each three-frequency beacon receiver;
and 5, the CT inversion module calls the time sequence of the observation TEC above each three-frequency beacon receiver, and inverts and calculates the two-dimensional distribution of the ionosphere electron density of the region along with the latitude and the height based on an ionosphere CT algorithm.
2. The channel simulator-based three-frequency beacon receiver station chain ionosphere CT simulation method as claimed in claim 1, wherein the method comprises the following steps: in step 2, the satellite position sequence during the satellite visible period, the position of each three-frequency beacon receiver and the observation time are input into an ionosphere empirical model NeQuick, the electron density value on the satellite-ground link is obtained through calculation, the ionosphere TEC time sequence of the satellite-ground link is obtained through integration according to the observation path, and the Doppler frequency shift calculation formula of the channel simulator is as follows:
wherein f represents the signal frequency, c is the speed of light, n represents the refractive index of the atmosphere,ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>Representing the difference over time, N e And (3) representing the electron density on the signal propagation path, calculating Doppler frequency shift values of three frequency points, and writing the signal amplitude attenuation and Doppler frequency shift of the three frequency points into text files respectively as channel parameter input files of a channel simulator.
3. The channel simulator-based three-frequency beacon receiver station chain ionosphere CT simulation method as claimed in claim 1, wherein the method comprises the following steps: in step 4, the amplitude P and phase Φ of the signal are calculated from:
P＝10×lg(I 2 +Q 2 ) (2)
Φ＝tan -1 (Q/I) (3)
where I and Q represent in-phase and quadrature components, respectively, of the coherent signal.
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