CN113671537A - Three-frequency beacon signal ionosphere channel simulation method - Google Patents

Three-frequency beacon signal ionosphere channel simulation method Download PDF

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CN113671537A
CN113671537A CN202110940748.XA CN202110940748A CN113671537A CN 113671537 A CN113671537 A CN 113671537A CN 202110940748 A CN202110940748 A CN 202110940748A CN 113671537 A CN113671537 A CN 113671537A
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CN113671537B (en
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於晓
孙芳
刘钝
郭敏军
孙兴信
谭帅
冯健
许娜
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China Institute of Radio Wave Propagation CETC 22 Research Institute
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China Institute of Radio Wave Propagation CETC 22 Research Institute
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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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The invention discloses a method for simulating an ionospheric channel of a tri-band beacon signal, which comprises the following steps: step 1, calculating the position of a satellite: step 2, calculating the transit time of the low-orbit satellite according to the positions of the satellite and the receiver: step 3, calculating a TEC value of the ionized layer of the satellite-ground link during the satellite transit period; step 4, calculating the changes of the phase and amplitude of the beacon signal of the frequency point when the beacon signal passes through the ionosphere channel to reach the ground according to the ionosphere TEC time sequence information of the satellite-ground link: and 5, writing the variation values of the amplitude and the phase of the frequency point beacon signals when the 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 a tri-frequency beacon receiver. The simulation method disclosed by the invention can generate an input file of the channel simulator (the channel simulator is connected with the tri-band beacon receiver) and is used as the input of the simulation verification of the satellite-ground link tri-band beacon ionized layer TEC measurement method, thereby laying a foundation for the design and application of a low-orbit spacecraft-based satellite-borne tri-band beacon measurement system.

Description

Three-frequency beacon signal ionosphere channel simulation method
Technical Field
The invention belongs to the technical field of ionosphere channel simulation, and particularly relates to a method for simulating an ionosphere channel of a three-frequency beacon signal 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 ionosphere channel passes through 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 ionosphere TEC is defined as an integral value of an ionosphere electron density along a signal propagation path per unit cross section, and is an ionosphere characteristic parameter closely related to a radio wave propagation characteristic.
The ionosphere TEC detection technology generally uses a satellite as a beacon, and utilizes a doppler frequency shift, an additional time delay or faraday rotation equivalent generated when a satellite signal propagates through an ionosphere channel to perform a corresponding solution. The ionospheric TEC measurement technique based on satellite beacons has the greatest advantages that a signal source is provided, and a receiving device is simple, wherein the differential doppler technique is based on the dispersion effect of the ionospheric layer, the frequency shift caused by satellite motion is eliminated by the difference of doppler frequency shifts of dual-frequency (or multi-frequency) coherent signals, an additional frequency shift related to the ionospheric TEC is reserved, and the ionospheric TEC value is obtained through conversion.
An early typical low-earth Satellite that can be used for ionospheric beacon detection is the Navy Satellite Navigation System (NNSS), the NNSS Satellite carries a dual-frequency beacon transmitter and transmits dual-frequency coherent signals with carrier frequencies of 150MHz and 400MHz, and a receiver receives Satellite beacon signals on the ground and realizes ionospheric TEC measurement by using 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 cosmc satellites on which were mounted a coherent beacon transmitter used as a measure of ionosphere TEC and multi-band signal flicker over the satellite-ground link, a masquerading receiver, and a miniphotometer. 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. A three-frequency beacon receiver of the ground subsystem tracks and receives three-frequency coherent signals transmitted by a satellite through an antenna, changes of phases, amplitudes and the like of the three-frequency signals when the three-frequency signals pass through an ionosphere channel are obtained through processing, an ionosphere TEC of a satellite-ground link is obtained through differential Doppler calculation, the ionosphere TEC is transmitted to a data processing center through a network, and the data processing center comprehensively utilizes the ionosphere TEC of each three-frequency beacon receiver station network to realize large-range ionosphere electron density reconstruction based on the ionosphere tomography (CIT) technology. Data products measured by the tri-band beacon comprise an ionized layer TEC, two-dimensional/three-dimensional electron density distribution and the like, and can serve the fields of seismic electromagnetic monitoring, space environment monitoring and early warning and the like.
Compared with the traditional ground monitoring technology, the main advantages of the measurement of the tri-band beacon ionized layer TEC are as follows: the global scope measurement is realized along with the satellite motion, the top ionized layer TEC information above the F2 layer can be contained, the low-orbit satellite motion is fast, so that the ionized layer static assumption is established, the horizontal resolution is high, and the like. In recent years, China also accelerates the research on satellite-borne triple-frequency beacon measurement technology, the first satellite-borne coherent beacon load is successfully carried on a seismic electromagnetic monitoring test satellite, ionosphere TEC measurement can be realized by emitting a group of coherent carrier signals, one (or more) receiver chains in the meridian direction are distributed on the ground, and two-dimensional (or multi-dimensional) ionosphere electron density distribution reconstruction can be realized by combining a CIT technology.
Disclosure of Invention
The invention provides a method for simulating an ionospheric channel of a tri-band beacon signal.
The invention adopts the following technical scheme:
the improvement of a method for simulating an ionospheric channel by a tri-band beacon signal is that the method comprises the following steps:
step 1, given a calculation scene, including a start time and an end time of measurement, a position of a receiver and a TLE ephemeris file of a low-orbit satellite, calculating the position of the satellite:
extracting satellite orbit inclination angles, eccentricity ratios and intervals from TLE ephemeris files of the low-orbit satellites, calculating the positions of the low-orbit satellites under a geocentric inertial coordinate system by combining an SGP4 model or an SDP4 model, and then converting the positions into satellite positions of longitude, latitude and altitude coordinates;
step 2, calculating the transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating the satellite elevation angle and the azimuth angle of ground observation according to the positions of a satellite and a receiver, setting a cut-off elevation angle of visible satellite observation, taking the time period that the elevation angle of the satellite observation is not lower than the observation cut-off elevation angle as the transit period of the low-orbit satellite, and calculating the position of the low-orbit satellite during the transit period of the satellite, the elevation angle and the azimuth angle of the satellite observation;
step 3, calculating a TEC value of the ionized layer of the satellite-ground link during the satellite transit period by using an ionized layer empirical model NeQuick;
inputting the position sequences of the satellite and the receiver into an ionized layer empirical model NeQuick during the low-orbit satellite transit period, calculating to obtain an electron density value of a satellite-ground link, and integrating according to an observation path to obtain an ionized layer TEC time sequence of the satellite-ground link;
and 4, calculating the changes of the phases and amplitudes of the beacon signals of the VHF, UHF and L frequency points when passing through an ionosphere channel to reach the ground according to the ionosphere TEC time sequence information of the satellite-ground link:
the change in signal phase is a function of signal frequency:
Figure BDA0003214754230000021
Figure BDA0003214754230000031
wherein f represents the signal frequency, c is the speed of light, N represents the atmospheric refractive index, NeRepresents the density of electrons on the signal propagation path,
Figure BDA0003214754230000032
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
Figure BDA0003214754230000033
expressing the difference of time, and calculating by the formula (1) to obtain Doppler frequency shift values of different frequency points;
the change in signal amplitude is characterized by a signal amplitude attenuation, as a function of signal frequency:
Figure BDA0003214754230000034
where L1 is the signal amplitude attenuation, f represents the signal frequency, R is the satellite-receiver distance, fcolFor collision frequency, the TEC represents an ionized layer TEC of a satellite-ground link, and signal amplitude attenuation values of different frequency points are obtained through calculation of the formula (2);
and 5, writing the variation values of the amplitudes and phases of the VHF, UHF and L frequency point beacon signals when passing through the ionosphere channel to reach the ground into a text file, inputting the text file into a satellite channel simulator connected with a tri-band beacon receiver, and using the text file as the input of simulation verification of the satellite-ground link tri-band beacon ionosphere TEC measurement method.
Further, in step 2, firstly, the calculated observation time and the signal sampling interval are both longer, rough low-orbit satellite transit time is calculated according to step 1 and step 2, then the time of the calculation scene is changed to be slightly longer than the transit time of the low-orbit satellite, meanwhile, the sampling interval of the signal is shortened, the satellite transit time with shorter signal sampling interval is obtained by recalculation 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 period with the signal sampling interval of 20ms can be obtained by repeating for 2-3 times.
The invention has the beneficial effects that:
the simulation method disclosed by the invention is mainly based on the dispersion effect of an ionized layer and is used for simulating the change of the signal amplitude and phase of VHF (150MHz), UHF (400MHz) and L (1067MHz) frequency band signals transmitted by a satellite-borne three-frequency beacon when the signals pass through the ionized layer channel to reach the ground.
Drawings
FIG. 1 is a schematic flow chart of a disclosed simulation method;
FIG. 2 is a diagram of the location of low-earth orbit satellites of the same day as in example 1;
FIG. 3 is a graph of the results of the satellite observation in elevation (up) and azimuth (down) calculated in example 1;
FIG. 4 is a diagram of ionosphere TEC time sequence of the satellite-ground link in embodiment 1;
FIG. 5 is Doppler frequency shift values of different frequency points in example 1;
FIG. 6 shows the attenuation values of signal amplitudes at different frequency points in example 1;
FIG. 7 is a graph of the results of the satellite observation in elevation (up) and azimuth (down) calculated in example 2;
FIG. 8 is a diagram of ionosphere TEC time sequence of the satellite-ground link in embodiment 2;
FIG. 9 is Doppler frequency shift values of different frequency points in example 2;
fig. 10 shows the attenuation values of the signal amplitudes at different frequency points in 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.
The invention discloses a method for simulating an ionospheric channel of a tri-band beacon signal, which comprises the following steps of:
step 1, given a calculation scene, including the observation time, the position of a receiver and a TLE ephemeris file of a low-orbit satellite, calculating the position of the satellite:
parameters such as satellite orbit inclination angle, eccentricity, interval and the like are extracted from TLE ephemeris files of the low-orbit satellites, the positions of the low-orbit satellites in the geocentric inertial coordinate system are calculated by combining an SGP4 model or an SDP4 model, and then the positions are converted into satellite positions (longitude, latitude and height) in the geodetic coordinate system. Here, we chose the SGP4 model;
step 2, calculating the transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating the satellite elevation angle and the satellite 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 for the satellite elevation angle is consistent with actual observation, selecting the time period that the elevation angle of the satellite observation 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 and the elevation angle and the azimuth angle of the satellite observation during the transit period of the satellite;
to obtain data for a complete satellite transit period, the simulated observation time needs to be taken long enough, while the signal sampling interval for ionosphere TEC measurement is short (here taken as 20ms), which results in a long calculation time. In order to save the calculation time, firstly, the calculated observation time and the signal sampling interval are both taken to be longer, such as 1 day and 30s respectively, the rough low-orbit satellite transit time is calculated according to the step 1 and the step 2, then the time of the calculation scene is changed to be slightly longer than the transit time of the low-orbit satellite, meanwhile, the sampling interval of the signal is shortened, the satellite transit time with the shorter signal sampling interval is obtained by recalculation according to the step 1 and the step 2, and the satellite position, the observed elevation angle and the azimuth angle sequence during the low-orbit satellite transit period with the signal sampling interval of 20ms can be obtained by repeating for 2-3 times.
Step 3, calculating a TEC value of the ionized layer of the satellite-ground link during the satellite transit period by using an ionized layer empirical model NeQuick;
inputting the position sequences of the satellite and the receiver and the like into an ionized layer empirical model NeQuick during the low-orbit satellite transit period, calculating to obtain an electron density value of a satellite-ground link, and integrating according to an observation path to obtain an ionized layer TEC time sequence of the satellite-ground link;
step 4, calculating the changes of the phases and amplitudes of the beacon signals of the VHF, UHF and L frequency points when passing through an ionosphere channel to reach the ground according to information such as the ionosphere TEC time sequence of the satellite-ground link;
and 5, writing the variation values of the amplitudes and phases of the VHF, UHF and L frequency point beacon signals when passing through the ionosphere channel to reach the ground into a text file, inputting the text file into a satellite channel simulator connected with a tri-band beacon receiver, and using the text file as the input of simulation verification of the satellite-ground link tri-band beacon ionosphere TEC measurement method.
Embodiment 1 discloses a method for simulating an ionospheric channel of a tri-band beacon signal, which comprises the following steps:
step 1, setting a calculation scene, including the start time and the end time of measurement, the position of a receiver and a TLE ephemeris file of a low-orbit satellite.
The measurement of the scene was calculated to start at 0 on day 1/7 of 2015 and end at 24 on day 1/7 of 2015, with the receiver at horse side (28.84 ° N, 120.87 ° E).
Parameters such as satellite orbit inclination angle, eccentricity, interval and the like are extracted from TLE ephemeris files of the low-orbit satellites, the positions of the low-orbit satellites in the geocentric inertial coordinate system are calculated through an SGP4 model, and then the positions are converted into satellite positions (longitude, latitude and height) in the geodetic coordinate system. Since this technology is mature, it is not described here in detail. Fig. 2 shows the location of the low earth orbit satellite for the current day, with latitude and longitude for the satellite up and down in sequence.
And 2, calculating the elevation angle and the azimuth angle of the satellite observed on the ground according to the positions of the satellite and the receiver, and taking the time period when the elevation angle observed by the satellite is not lower than the observation cut-off elevation angle as the transit period of the low-orbit satellite.
In the embodiment, the elevation angle of the observation satellite is set to be 5 degrees, and the time when the elevation angle of the observation satellite is not less than 5 degrees is intercepted as the transit time of the low-orbit satellite. In order to save the calculation time, the embodiment selects the calculation time of 2015, 1 month, 7 days and 0-24 days, the signal sampling interval is 30s, and the results of the observation elevation angle (upper) and the observation azimuth angle (lower) of the satellite calculated according to the steps 1 and 2 are 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 diagram is the observation azimuth of the satellite. The portion of the upper graph where the curve exceeds the straight line corresponds to the transit time of the low earth orbit satellite. Three low-orbit satellite transit times, respectively 06:10:00-06:19:00, 16:41:30-16:48:30, 18:14:30-18:22:30, were observed at the receiving station on horses at 0-24 days 1/7/2015.
And shortening the signal sampling interval, and recalculating the satellite transit time with shorter signal sampling interval. And repeating 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 obtained satellite transit time is 2015, 1 month, 7 days 06:09:38.16-06:18: 42.98.
Step 3, calculating a TEC value of the ionized layer of the satellite-ground link during the satellite transit period by using an ionized layer empirical model NeQuick;
inputting the position sequences of the satellite and the receiver and the like into an ionized layer empirical model NeQuick during the low-orbit satellite transit period, calculating to obtain an electron density value on a satellite-ground link, and integrating according to an observation path to obtain an ionized layer TEC time sequence of the satellite-ground link shown in figure 4;
and 4, calculating the changes of the phases and amplitudes of the beacon signals of the VHF, UHF and L frequency points when passing through an ionosphere channel to reach the ground according to information such as the ionosphere TEC time sequence of the satellite-ground link:
the change of the 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:
Figure BDA0003214754230000061
wherein f represents the signal frequency, c is the speed of light, N represents the atmospheric refractive index, NeRepresents the density of electrons on the signal propagation path,
Figure BDA0003214754230000062
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
Figure BDA0003214754230000063
the difference of the time is expressed, the frequency of the satellite beacon signal, the satellite motion speed and the ionosphere TEC value are brought into formula (1), and the doppler shift values of different frequency points can be calculated, and as a result, the doppler shifts of VHF, UHF and L frequency point signals are sequentially from top to bottom as shown in fig. 5.
The change in signal amplitude is characterized by a signal amplitude attenuation, which includes the following contributions: attenuation due to ionospheric absorption, losses due to link propagation, gain of the transmitter and receiver, etc. In this example, power gains of the transmitter and the receiver are not considered for the moment, and only attenuation caused by ionospheric absorption and loss caused by link propagation are considered, which can be expressed as a function of signal frequency:
Figure BDA0003214754230000064
where L1 is the signal amplitude attenuation, f represents the signal frequency, R is the satellite-receiver distance, fcolAs collision frequency, the TEC represents an ionosphere TEC of a satellite-ground link, and the frequency of a satellite beacon signal, the positions of a satellite and a receiver, and the ionosphere TEC value are brought into formula (2), so that signal amplitude attenuation values of different frequency points can be calculated, and as a result, as shown in fig. 6, the amplitude attenuation values of VHF, UHF, and L frequency point signals are sequentially obtained from top to bottom;
and 5, writing the variation values of the amplitudes and phases of the VHF, UHF and L frequency point beacon signals when passing through the ionosphere channel to reach the ground into corresponding text files, inputting the text files into a satellite channel simulator connected with a tri-band beacon receiver, and using the text files as the input of simulation verification of the satellite-ground link tri-band beacon ionosphere TEC measurement method.
Embodiment 2 discloses a method for simulating an ionospheric channel of a tri-band beacon signal, which comprises the following steps:
step 1: given a calculation scenario, the position (longitude, latitude and altitude) of the low-orbit satellite is calculated from the TLE ephemeris file of the low-orbit satellite and the SGP4 model.
The time measured, TLE ephemeris file for low orbit satellites is consistent with example 1, step 1, with the receiver at the opponent's home (26.92 ° N, 120.25 ° E). And calculating the positions (longitude, latitude and altitude) of the low-orbit satellites according to the TLE ephemeris file and the SGP4 model of the low-orbit satellites. The low-earth satellite position of the day is again given by fig. 2, in order from top to bottom, the latitude and longitude of the satellite.
Step 2: and calculating the elevation angle and the azimuth angle of the satellite observed on the ground according to the positions of the satellite and the receiver, and taking the time that the elevation angle of the satellite is not lower than the observation cut-off elevation angle as the transit time of the low-orbit satellite.
The cutoff elevation angle of an observation satellite is set to be 5 degrees, the calculation time is 2015, 1, 7, 0-24 days, and the signal sampling interval is 30 s. The results of calculating the elevation and azimuth of the satellite are shown in fig. 7. The reception station of the skillet observes three satellite transit times on 1 month and 7 days of 2015, which are 06:10:30-06:19:30, 16:41:30-16:47:30 and 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 time of the first satellite transit is 2015, 1 month, 7 days 06:10:9.42-06:19: 13.7.
And step 3: the ionosphere time sequence of the satellite-ground link ionosphere TEC during the satellite transit is calculated by an ionosphere empirical model NeQuick, and the result is shown in fig. 8.
And 4, step 4: and respectively calculating the changes of the amplitude and the phase of the beacon signals of the VHF, UHF and L frequency points when passing through an ionosphere channel to reach the ground according to information such as the ionosphere TEC sequence of the satellite-ground link.
The change of the signal phase mainly takes the frequency shift caused by the relative motion of the satellite-receiver and the frequency shift caused by the ionospheric electron density into consideration. The frequency of the satellite beacon signal, the satellite motion speed and the ionosphere TEC value are taken into formula (1), and the doppler shift results of different frequency points are calculated and are shown in fig. 9, and the doppler shifts of VHF, UHF and L frequency point signals are sequentially performed from top to bottom.
The change of the signal amplitude mainly considers the attenuation caused by ionospheric absorption and the loss 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 taken into formula (2), and the amplitude attenuation results of the signals at different frequency points are calculated and shown in fig. 10, and the amplitude attenuation values of the VHF, UHF and L frequency point signals are sequentially obtained from top to bottom.
And 5: the method comprises the steps of writing the amplitude and phase changes of a tri-band beacon signal when the tri-band beacon signal passes through an ionosphere channel to reach the ground into a text file, inputting the text file into a satellite channel simulator connected with a tri-band beacon receiver, and using the text file as the input of simulation verification of a satellite-ground link tri-band beacon ionosphere TEC measurement method.

Claims (2)

1. A method for simulating an ionospheric channel of a tri-band beacon signal is characterized by comprising the following steps:
step 1, given a calculation scene, including a start time and an end time of measurement, a position of a receiver and a TLE ephemeris file of a low-orbit satellite, calculating the position of the satellite:
extracting satellite orbit inclination angles, eccentricity ratios and intervals from TLE ephemeris files of the low-orbit satellites, calculating the positions of the low-orbit satellites under a geocentric inertial coordinate system by combining an SGP4 model or an SDP4 model, and then converting the positions into satellite positions of longitude, latitude and altitude coordinates;
step 2, calculating the transit time of the low-orbit satellite according to the positions of the satellite and the receiver:
calculating the satellite elevation angle and the azimuth angle of ground observation according to the positions of a satellite and a receiver, setting a cut-off elevation angle of visible satellite observation, taking the time period that the elevation angle of the satellite observation is not lower than the observation cut-off elevation angle as the transit period of the low-orbit satellite, and calculating the position of the low-orbit satellite during the transit period of the satellite, the elevation angle and the azimuth angle of the satellite observation;
step 3, calculating a TEC value of the ionized layer of the satellite-ground link during the satellite transit period by using an ionized layer empirical model NeQuick;
inputting the position sequences of the satellite and the receiver into an ionized layer empirical model NeQuick during the low-orbit satellite transit period, calculating to obtain an electron density value of a satellite-ground link, and integrating according to an observation path to obtain an ionized layer TEC time sequence of the satellite-ground link;
and 4, calculating the changes of the phases and amplitudes of the beacon signals of the VHF, UHF and L frequency points when passing through an ionosphere channel to reach the ground according to the ionosphere TEC time sequence information of the satellite-ground link:
the change in signal phase is a function of signal frequency:
Figure FDA0003214754220000011
wherein f represents the signal frequency, c is the speed of light, N represents the atmospheric refractive index, NeRepresents the density of electrons on the signal propagation path,
Figure FDA0003214754220000012
the ionosphere TEC, which represents the satellite-ground link, r is the position of the receiver, s is the position of the satellite,
Figure FDA0003214754220000013
expressing the difference of time, and calculating by the formula (1) to obtain Doppler frequency shift values of different frequency points;
the change in signal amplitude is characterized by a signal amplitude attenuation, as a function of signal frequency:
Figure FDA0003214754220000014
where L1 is the signal amplitude attenuation, f represents the signal frequency, R is the satellite-receiver distance, fcolFor collision frequency, the TEC represents the ionized layer TEC of the satellite-ground link, and the signal amplitudes of different frequency points are calculated by the formula (2)A degree attenuation value;
and 5, writing the variation values of the amplitudes and phases of the VHF, UHF and L frequency point beacon signals when passing through the ionosphere channel to reach the ground into a text file, inputting the text file into a satellite channel simulator connected with a tri-band beacon receiver, and using the text file as the input of simulation verification of the satellite-ground link tri-band beacon ionosphere TEC measurement method.
2. The method for ionospheric channel simulation of a tri-band beacon signal according to claim 1, wherein: in step 2, firstly, the calculated observation time and signal sampling interval are both longer, rough low-orbit satellite transit time is calculated according to step 1 and step 2, then the time of the calculation scene is changed to be slightly longer than the transit time of the low-orbit satellite, meanwhile, the sampling interval of the signal is shortened, the time is recalculated according to step 1 and step 2 to obtain the satellite transit time with shorter signal sampling interval, and the satellite position, the observed elevation angle and the azimuth angle sequence during the low-orbit satellite transit period with the signal sampling interval of 20ms can be obtained by repeating for 2-3 times.
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CN114184848A (en) * 2021-12-03 2022-03-15 中国科学院国家空间科学中心 Goertzel algorithm-based point-by-point scanning real-time processing method for satellite-borne VHF transient signals
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