CN113671537B - Three-frequency beacon signal ionosphere channel simulation method - Google Patents
Three-frequency beacon signal ionosphere channel simulation method 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
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- 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
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Abstract
The invention discloses a three-frequency beacon signal ionosphere channel simulation method, which comprises the following steps: step 1, calculating the position of satellites: step 2, calculating transit time of the low-orbit satellite according to the positions of the satellite and the receiver: step 3, calculating a satellite-ground link ionosphere TEC value in the satellite transit period; step 4, calculating the change of the phase and the amplitude of the frequency point beacon signal when the ionosphere crossing channel reaches the ground by using the ionosphere TEC time sequence information of the star-ground link: and 5, writing the change values of the amplitude and the phase of the frequency point beacon signals when the amplitude and the phase of the frequency point beacon signals pass through the ionosphere channel to reach the ground into a text file, and inputting the text file into a satellite channel simulator connected with the three-frequency beacon receiver. The simulation method disclosed by the invention can generate an input file of a channel simulator (the channel simulator is connected with a three-frequency beacon receiver) which is used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method, and lays a foundation for the design and application of a satellite-borne three-frequency beacon measurement system based on a low-orbit spacecraft.
Description
Technical Field
The invention belongs to the technical field of ionosphere channel simulation, and particularly relates to a three-frequency beacon signal ionosphere channel simulation method in the field, which is used for simulating the change of the amplitude and the phase of a satellite-borne three-frequency beacon signal when the satellite-borne three-frequency beacon signal passes through an ionosphere channel to reach the ground and is used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
Background
The definition of the ionosphere TEC is the integral value of the ionosphere electron density along the signal propagation path in a unit section, and is an ionosphere characteristic parameter closely related to the radio wave propagation characteristics.
The ionosphere TEC detection technology generally uses satellites as beacons, and utilizes the effects of doppler shift, additional time delay or faraday rotation, etc. generated when satellite signals propagate through ionosphere channels. The ionosphere TEC measurement technology based on satellite beacons has the greatest advantages that a signal source is provided, receiving equipment is simple, the differential Doppler technology is based on the dispersion effect of an ionosphere, the frequency shift caused by satellite motion is eliminated by the difference of Doppler frequency shift of a dual-frequency (or multi-frequency) coherent signal, the additional frequency shift related to the ionosphere TEC is reserved, and the ionosphere TEC value is obtained through conversion.
Early typical low-orbit satellites used for ionosphere beacon detection were us navy meridian satellite navigation systems (Navy Navigation Satellite System, NNSS), the NNSS satellites were equipped with dual-frequency beacon transmitters, transmitting dual-frequency coherent signals with carrier frequencies of 150MHz and 400MHz, and the receivers received satellite beacon signals on the ground, and the ionosphere TEC measurements were achieved using differential doppler 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 a coherent beacon transmitter, a occultation receiver and a compact photometer mounted thereon, wherein the coherent beacon transmitter was used as a measure of ionospheric TEC and multi-band signal flicker over 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 three-frequency coherent signals transmitted by satellites through antennas, processes and obtains the changes of the phases, the amplitudes and the like of the three-frequency signals when the three-frequency signals pass through ionosphere channels, acquires ionosphere TECs of a satellite-ground link through differential Doppler calculation, transmits the ionosphere TECs to a data processing center through a network, and the data processing center comprehensively utilizes the ionosphere TECs of station networks of the three-frequency beacon receivers and realizes large-range ionosphere electron density reconstruction based on the ionosphere tomography (CIT) technology. The data products of the three-frequency beacon measurement comprise ionized layer TEC, two-dimensional/three-dimensional electron density distribution and the like, and can be used for the fields of earthquake electromagnetic monitoring, space environment monitoring and early warning and the like.
Compared with the traditional foundation monitoring technology, the three-frequency beacon ionosphere TEC measurement has the main advantages that: global measurement is realized along with satellite movement, the global measurement can comprise the TEC information of the top ionosphere above the F2 layer, the ionosphere static assumption is established due to the fact that the low-orbit satellite moves faster, the horizontal resolution is high, and the like. In recent years, research on satellite-borne three-frequency beacon measurement technology is accelerated in China, a first satellite-borne coherent beacon load is successfully carried on a seismic electromagnetic monitoring test satellite, ionosphere TEC measurement can be achieved by transmitting a group of coherent carrier signals, one (or more) receiver chains along the meridian direction are arranged on the ground, and distribution reconstruction of two-dimensional (or multidimensional) ionosphere electron density can be achieved by combining with CIT technology.
Disclosure of Invention
The invention aims to provide a three-frequency beacon signal ionosphere channel simulation method.
The invention adopts the following technical scheme:
in a method for ionosphere channel simulation of a three-frequency beacon signal, the improvement comprising the steps of:
step 1, given a calculation scenario comprising a measured start time and end time, a receiver position and a TLE ephemeris file for low orbit satellites, calculating the satellite position:
extracting satellite orbit inclination angle, eccentricity and interval from TLE ephemeris file of the low orbit satellite, combining SGP4 model or SDP4 model, calculating the position of the low orbit satellite under the geocentric inertial coordinate system, and converting the position into satellite positions of longitude, latitude and altitude coordinates;
step 2, calculating transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating the satellite elevation angle and azimuth angle of ground observation by the positions of the satellite and the receiver, setting a cut-off elevation angle of visible satellite observation, taking the time period that the satellite observation elevation angle is not lower than the observation cut-off elevation angle as the transit period of the low orbit satellite, and calculating the low orbit satellite position, the satellite observation elevation angle and azimuth angle during the transit period of the satellite;
step 3, calculating a satellite-ground link ionosphere TEC value in the satellite transit period by using an ionosphere experience model Nequick;
during the transit period of a low-orbit satellite, the position sequences of the satellite and the receiver are input into an ionosphere empirical model Nequick, an electron density value of a satellite-ground link is obtained through calculation, and an ionosphere TEC time sequence of the satellite-ground link is obtained through integration according to an observation path;
step 4, calculating the changes of the phases and the amplitudes of VHF, UHF and L frequency point beacon signals when the ionosphere channel is crossed to reach the ground by using the ionosphere TEC time sequence information of the star-ground link:
the change in signal phase is a function of signal frequency:
wherein f represents the signal frequency, c is the speed of light, N represents the refractive index of the atmosphere, N e Representing the electron density on the signal propagation path,
ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>
Representing the difference of time, and calculating Doppler frequency shift values of different frequency points by the formula (1);
the change in signal amplitude is characterized by signal amplitude attenuation as a function of signal frequency:
wherein L1 is signal amplitude attenuation, f represents signal frequency, R is distance of satellite-receiver, f col For collision frequency, TEC represents ionosphere TEC of a satellite-ground link, and signal amplitude attenuation values of different frequency points are obtained through calculation according to a formula (2);
and 5, writing the change values of the amplitude and the phase of the VHF, UHF and L frequency point beacon signals when the amplitude and the phase of the VHF, UHF and L frequency point beacon signals pass through an ionosphere channel to reach the ground into a text file, and inputting the text file into a satellite channel simulator connected with a three-frequency beacon receiver to be used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
Further, in step 2, firstly, the calculated observation time and the signal sampling interval are taken longer, the rough low-orbit satellite transit time is calculated according to step 1 and step 2, then the calculated scene time is changed to be slightly longer than the low-orbit satellite transit time, meanwhile, the signal sampling interval is shortened, the satellite transit time with the shorter signal sampling interval is calculated again according to step 1 and step 2, and the satellite position, the observed elevation angle and the azimuth sequence during the low-orbit satellite transit with the signal sampling interval of 20ms can be obtained by repeating for 2-3 times.
The beneficial effects of the invention are as follows:
the simulation method disclosed by the invention is mainly based on the dispersion effect of an ionosphere, is used for simulating the changes of the signal amplitude and the phase of VHF (150 MHz), UHF (400 MHz) and L (1067 MHz) frequency band signals transmitted by a satellite-borne three-frequency beacon when the signals pass through an ionosphere channel to reach the ground, can generate an input file of a channel simulator (the channel simulator is connected with a three-frequency beacon receiver) and is used as the input of simulation verification of the satellite-ground link three-frequency beacon ionosphere TEC measurement method, and lays a foundation for the design and the application of a satellite-borne three-frequency beacon measurement system based on a low-orbit spacecraft.
Drawings
FIG. 1 is a schematic flow chart of the disclosed simulation method;
FIG. 2 is a low-orbit satellite position map for the day of example 1;
FIG. 3 is a graph of satellite observation elevation (up) and azimuth (down) results calculated in example 1;
FIG. 4 is a ionospheric TEC time series plot for the Star-Earth link of example 1;
fig. 5 shows doppler shift values of different frequency points in embodiment 1;
FIG. 6 is the signal amplitude attenuation values for different frequency points in example 1;
FIG. 7 is a graph of satellite observation elevation (up) and azimuth (down) results calculated in example 2;
FIG. 8 is a ionospheric TEC time-series diagram of the Star-Earth link of example 2;
fig. 9 is the doppler shift values of different frequency points in embodiment 2;
fig. 10 is the signal amplitude attenuation values of different frequency points in embodiment 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.
The invention discloses a three-frequency beacon signal ionosphere channel simulation method, which is shown in figure 1 and comprises the following steps:
step 1, given a computing scenario comprising the time of observation, the position of the receiver and the TLE ephemeris file of the low orbit satellites, the position of the satellites is computed:
parameters such as satellite orbit inclination angle, eccentricity, interval and the like are extracted from TLE ephemeris files of the low-orbit satellites, and the position of the low-orbit satellites under a geocentric inertial coordinate system is calculated by combining with an SGP4 model or an SDP4 model and then converted into satellite positions (longitude, latitude and altitude) under a geodetic coordinate system. Here we choose the SGP4 model;
step 2, calculating transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating satellite elevation angle and azimuth angle of ground observation according to the positions of the satellite and the receiver, setting a cut-off elevation angle of visible satellite observation to be consistent with actual observation, selecting a time period of which the elevation angle of satellite observation is not lower than the cut-off elevation angle of observation as a transit period of a low orbit satellite, and calculating the position of the low orbit satellite and the elevation angle and azimuth angle of satellite observation during the transit period of the satellite;
to obtain data during a complete satellite transit, the simulated observation time needs to be taken long enough, while the signal sampling interval used as ionosphere TEC measurement is short (here taken as 20 ms), which results in a long computation time. In order to save calculation time, firstly, taking longer observation time and signal sampling interval, for example, 1 day and 30s respectively, calculating to obtain coarser transit time of the low-orbit satellite according to the steps 1 and 2, then changing the time of a calculation scene to enable the transit time to be slightly longer than the transit time of the low-orbit satellite, simultaneously shortening the signal sampling interval, recalculating according to the steps 1 and 2 to obtain satellite transit time with shorter signal sampling interval, and repeating for 2-3 times to obtain satellite positions, observed elevation angles and azimuth sequences of the low-orbit satellite in the transit period of the signal sampling interval of 20 ms.
Step 3, calculating a satellite-ground link ionosphere TEC value in the satellite transit period by using an ionosphere experience model Nequick;
inputting the position sequences of the satellite and the receiver and the like into an ionosphere empirical model Nequick during the transit of the low-orbit satellite, calculating to obtain an electron density value of a satellite-ground link, and integrating according to an observation path to obtain an ionosphere TEC time sequence of the satellite-ground link;
step 4, calculating the changes of the phases and the amplitudes of the VHF, UHF and L frequency point beacon signals when the signals pass through the ionosphere channel to reach the ground according to the information such as the ionosphere TEC time sequence of the star-ground link;
and 5, writing the change values of the amplitude and the phase of the VHF, UHF and L frequency point beacon signals when the amplitude and the phase of the VHF, UHF and L frequency point beacon signals pass through an ionosphere channel to reach the ground into a text file, and inputting the text file into a satellite channel simulator connected with a three-frequency beacon receiver to be used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
Embodiment 1 discloses a three-frequency beacon signal ionosphere channel simulation method, which comprises the following steps:
step 1, a given computing scenario, including a measured start time and end time, a receiver position, a TLE ephemeris file for low orbit satellites.
The measurement start time of the calculated scene is 2015, 1 month, 7 days, 0 point, the end time is 2015, 1 month, 7 days, 24 points, and the receiver is located in Ma Bian (28.84 DEG N,120.87 DEG E).
Parameters such as satellite orbit inclination, eccentricity, interval and the like are extracted from a TLE ephemeris file of the low-orbit satellite, the position of the low-orbit satellite under a geocentric inertial coordinate system is calculated by an SGP4 model, and then the position is converted into satellite positions (longitude, latitude and altitude) under a geodetic coordinate system. Since this technology is mature, it is not described in detail here. Fig. 2 shows the low-orbit satellite positions of the day, in order of the latitude and longitude of the satellites, up and down.
And 2, calculating the elevation angle and azimuth angle of the satellite observed on the ground according to the positions of the satellite and the receiver, and taking the time period of which the elevation angle of the satellite observation is not lower than the elevation angle of the observation cut-off as the transit period of the low orbit satellite.
In the embodiment, the cut-off elevation angle of the observation satellite is set to be 5 degrees, and the time when the elevation angle of the intercepted observation satellite is not lower than 5 degrees is the transit time of the low orbit satellite. In order to save calculation time, when the calculation time is selected to be 0-24 on 1 month and 7 days of 2015, the signal sampling interval is 30s, and the observation elevation angle (up) and azimuth angle (down) of the satellite are calculated according to the steps 1 and 2, and the result is shown in fig. 3. The upper graph curve is the observation elevation angle of the satellite, and the observation elevation angle of the straight line corresponding to the satellite is 5 degrees; the lower plot is the satellite's observation azimuth. The portion of the upper graph exceeding the straight line corresponds to the transit time of the low-orbit satellite. The equine edge receiving station observed three low orbit satellite passes at 5, 1 month, 7 days, 0-24, 06:10:00-06:19:00, 16:41:30-16:48:30, 18:14:30-18:22:30, respectively.
And shortening the signal sampling interval, and recalculating to obtain the satellite transit time with shorter signal sampling interval. Repeating the process for 2 times to obtain the low-orbit satellite transit time with the signal sampling interval of 20 ms. Taking the first transit as an example, the satellite transit time is 2015, 1 month, 7 days 06:09:38.16-06:18:42.98.
Step 3, calculating a satellite-ground link ionosphere TEC value in the satellite transit period by using an ionosphere experience model Nequick;
inputting the position sequences of the satellite and the receiver and the like into an ionosphere empirical model Nequick during the transit of the low-orbit satellite, calculating to obtain an electron density value on a satellite-earth link, and integrating according to an observation path to obtain an ionosphere TEC time sequence of the satellite-earth link shown in fig. 4;
step 4, calculating the changes of the phases and the amplitudes of the VHF, UHF and L frequency point beacon signals when the signals pass through the ionosphere channel to reach the ground according to the information such as the ionosphere TEC time sequence of the star-ground link and the like:
the change in signal phase mainly takes into account the frequency shift caused by the relative motion of the satellite-receiver and the frequency shift caused by the ionospheric electron density, which is a function of the signal frequency:
wherein f represents the signal frequency, c is the speed of light, N represents the refractive index of the atmosphere, N e Representing the electron density on the signal propagation path,
ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>
Representing the difference of time, bringing the frequency of satellite beacon signals, the speed of satellite motion and the ionosphere TEC value into formula (1), and calculating Doppler frequency shift values of different frequency points to obtain the resultAs shown in fig. 5, the doppler shifts of VHF, UHF and L frequency point signals are sequentially from top to bottom.
The change in signal amplitude is characterized by a signal amplitude decay, which comprises contributions of: attenuation due to ionospheric absorption, loss due to link propagation, gain of the transmitter and receiver, etc. The power gain of the transmitter and the receiver and the like are not considered in the example, only the attenuation caused by ionosphere absorption and the loss caused by link propagation are considered, and the power gain can be expressed as a function of signal frequency:
wherein L1 is signal amplitude attenuation, f represents signal frequency, R is distance of satellite-receiver, f col For collision frequency, TEC represents ionosphere TEC of a satellite-ground link, the frequency of a satellite beacon signal, the positions of a satellite and a receiver and the value of the ionosphere TEC are brought into formula (2), signal amplitude attenuation values of different frequency points can be obtained through calculation, and the result is shown in figure 6, namely the amplitude attenuation values of VHF, UHF and L frequency point signals in sequence from top to bottom;
and 5, writing the change values of the amplitude and the phase of the VHF, UHF and L frequency point beacon signals when the amplitude and the phase of the VHF, UHF and L frequency point beacon signals pass through an ionosphere channel to reach the ground into corresponding text files, and inputting the text files into a satellite channel simulator connected with a three-frequency beacon receiver to be used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
Embodiment 2 discloses a three-frequency beacon signal ionosphere channel simulation method, which comprises the following steps:
step 1: given a computing scenario, the position (longitude, latitude, and altitude) of the low-orbit satellite is computed from the TLE ephemeris file and SGP4 model of the low-orbit satellite.
The TLE ephemeris file for the time of measurement, low orbit satellite, is consistent with example 1, step 1, with the receiver located at the smart home (26.92°n,120.25 °e). The location (longitude, latitude and altitude) of the low orbit satellite is calculated from the TLE ephemeris file and SGP4 model of the low orbit satellite. The low orbit satellite position for the day is still given by fig. 2, which shows the latitude and longitude of the satellite in order from top to bottom.
Step 2: and calculating the elevation angle and azimuth angle of the satellite observed on the ground according to the positions of the satellite and the receiver, and taking the time of which the elevation angle of the satellite is not lower than the elevation angle of the observed cut-off as the transit time of the low orbit satellite.
And setting the cut-off elevation angle of the observation satellite to be 5 degrees, and setting the signal sampling interval to be 30s when the calculation time is 2015, 1, 7 and 0-24. The result of the calculation of the satellite's observation elevation and azimuth is shown in fig. 7. Three satellite passes were observed by the smart receiving station on day 1 and 7 of 2015, 06:10:30-06:19:30, 16:41:30-16:47:30, 18:14:00-18:22:30, respectively. And shortening the signal sampling interval, and repeating the calculation for 2 times to obtain the low-orbit satellite transit time with the signal sampling interval of 20 ms. Wherein the first satellite transit time is 2015, 1 month, 7 days 06:10:9.42-06:19:13.7.
Step 3: the time series of the satellite-ground link ionosphere TEC during the satellite transit is calculated by an ionosphere experience model Nequick, and the result is shown in figure 8.
Step 4: and calculating the changes of the amplitude and the phase of the VHF, UHF and L frequency point beacon signals when the signals pass through the ionosphere channel to reach the ground according to the information such as the ionosphere TEC sequence of the star-ground link and the like.
The change in signal phase mainly takes into account the frequency shift caused by the satellite-receiver relative motion and the frequency shift caused by the ionospheric electron density. The frequency of the satellite beacon signal, the speed of the satellite motion and the ionosphere TEC value are brought into the formula (1), and Doppler frequency shift results of different frequency points are calculated as shown in figure 9, and the Doppler frequency shifts of VHF, UHF and L frequency point signals are sequentially from top to bottom.
The change in signal amplitude mainly takes into account the attenuation caused by ionospheric absorption and the losses caused by link propagation. The frequency of the satellite beacon signal, the positions of the satellite and the receiver and the ionosphere TEC value are brought into the step (2), and the signal amplitude attenuation results of different frequency points are calculated, as shown in figure 10, and the amplitude attenuation values of VHF, UHF and L frequency point signals are sequentially obtained from top to bottom.
Step 5: the change of signal amplitude and phase of the three-frequency beacon signal when the three-frequency beacon signal passes through the ionosphere channel to reach the ground is written into a text file, and the text file is input into a satellite channel simulator connected with a three-frequency beacon receiver and is used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
Claims (2)
1. The ionosphere channel simulation method for the three-frequency beacon signal is characterized by comprising the following steps of:
step 1, given a calculation scenario comprising a measured start time and end time, a receiver position and a TLE ephemeris file for low orbit satellites, calculating the satellite position:
extracting satellite orbit inclination angle, eccentricity and interval from TLE ephemeris file of the low orbit satellite, combining SGP4 model or SDP4 model, calculating the position of the low orbit satellite under the geocentric inertial coordinate system, and converting the position into satellite positions of longitude, latitude and altitude coordinates;
step 2, calculating transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating the satellite elevation angle and azimuth angle of ground observation by the positions of the satellite and the receiver, setting a cut-off elevation angle of visible satellite observation, taking the time period that the satellite observation elevation angle is not lower than the observation cut-off elevation angle as the transit period of the low orbit satellite, and calculating the low orbit satellite position, the satellite observation elevation angle and azimuth angle during the transit period of the satellite;
step 3, calculating a satellite-ground link ionosphere TEC value in the satellite transit period by using an ionosphere experience model Nequick;
during the transit period of a low-orbit satellite, the position sequences of the satellite and the receiver are input into an ionosphere empirical model Nequick, an electron density value of a satellite-ground link is obtained through calculation, and an ionosphere TEC time sequence of the satellite-ground link is obtained through integration according to an observation path;
step 4, calculating the changes of the phases and the amplitudes of VHF, UHF and L frequency point beacon signals when the ionosphere channel is crossed to reach the ground by using the ionosphere TEC time sequence information of the star-ground link:
the change in signal phase is a function of signal frequency:
wherein f represents the signal frequency, c is the speed of light, N represents the refractive index of the atmosphere, N e Representing the electron density on the signal propagation path,
ionosphere TEC, r being the position of the receiver, s being the position of the satellite, +.>
Representing the difference of time, and calculating Doppler frequency shift values of different frequency points by the formula (1);
the change in signal amplitude is characterized by signal amplitude attenuation as a function of signal frequency:
wherein L1 is signal amplitude attenuation, f represents signal frequency, R is distance of satellite-receiver, f col For collision frequency, TEC represents ionosphere TEC of a satellite-ground link, and signal amplitude attenuation values of different frequency points are obtained through calculation according to a formula (2);
and 5, writing the change values of the amplitude and the phase of the VHF, UHF and L frequency point beacon signals when the amplitude and the phase of the VHF, UHF and L frequency point beacon signals pass through an ionosphere channel to reach the ground into a text file, and inputting the text file into a satellite channel simulator connected with a three-frequency beacon receiver to be used as the input of simulation verification of a satellite-ground link three-frequency beacon ionosphere TEC measurement method.
2. The three-frequency beacon ionosphere channel simulation method according to claim 1, wherein: in step 2, firstly, the calculated observation time and the signal sampling interval are taken longer, the rough low-orbit satellite transit time is calculated according to step 1 and step 2, then the calculation scene time is changed to be slightly longer than the low-orbit satellite transit time, meanwhile, the signal sampling interval is shortened, the satellite transit time with the shorter signal sampling interval is calculated again according to step 1 and step 2, and the satellite position, the observed elevation angle and the azimuth angle sequence during the low-orbit satellite transit with the signal sampling interval of 20ms can be obtained by repeating for 2-3 times.
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