CN112039579A - Signal synchronization method and device for satellite communication - Google Patents
Signal synchronization method and device for satellite communication Download PDFInfo
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- CN112039579A CN112039579A CN202010951645.9A CN202010951645A CN112039579A CN 112039579 A CN112039579 A CN 112039579A CN 202010951645 A CN202010951645 A CN 202010951645A CN 112039579 A CN112039579 A CN 112039579A
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Abstract
The invention provides a signal synchronization method and a signal synchronization device for satellite communication, which relate to the technical field of satellite communication and comprise the following steps: acquiring a downlink signal transmitted by a satellite; calculating a signal offset of an uplink signal of the ground terminal based on the downlink signal and the target parameter; compensating the uplink signal with a signal offset; after the uplink signal is compensated, sending the compensated uplink signal to the satellite, and acquiring the signal offset of the compensated uplink signal calculated by the satellite; and correcting the signal offset of the compensated uplink signal based on the signal offset and the target variable quantity of the compensated uplink signal to obtain a target signal offset, so that the technical problem of low time and frequency synchronization precision of the signal in the conventional satellite communication is solved.
Description
Technical Field
The present invention relates to the field of satellite communications technologies, and in particular, to a signal synchronization method and apparatus for satellite communications.
Background
In a medium-low orbit broadband satellite communication system adopting a multi-frequency time division communication system, such as a medium-low orbit communication satellite constellation based on a DVB-RCS2/DVB-S2X air interface protocol or a 4G air interface protocol, the medium-low orbit communication satellite constellation has the characteristics of high communication signal frequency, fast satellite movement and the like, which causes extra difficulty in time and frequency synchronization between satellites and the ground, as shown in fig. 1. On one hand, due to the rapid movement of the satellite, particularly for a communication system working in a Ka frequency band, the Doppler frequency offset and the Doppler change rate are large, when a terminal has large Doppler compensation residue, the difficulty of satellite demodulation is increased, and meanwhile, the interference of an adjacent channel can be caused; on the other hand, in a time division air interface system, users send data to a satellite in a burst mode, which requires high time synchronization precision to avoid data collision between users, however, in medium and low orbit broadband satellite communication, the satellite moves fast, which causes fast time delay change between satellites and the ground, and meanwhile, because the broadband satellite communication rate is high, the protection time slot is small, and the requirement on time synchronization is high. Finally, when the satellite and the terminal adopt a common constant temperature crystal oscillator or a temperature compensation crystal oscillator, the frequency deviation of a frequency conversion channel is large, so that the satellite-ground frequency deviation is further increased, and accurate compensation is required.
No effective solution has been proposed to the above problems.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a signal synchronization method for satellite communication, so as to alleviate the technical problem of low accuracy of time and frequency synchronization of signals in the existing satellite communication.
In a first aspect, an embodiment of the present invention provides a signal synchronization method for satellite communication, which is applied to a ground terminal, and includes: acquiring a downlink signal transmitted by a satellite; calculating a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, wherein the signal offset comprises: the uplink signal is a link signal sent to the satellite by the ground terminal; compensating the uplink signal with the signal offset; after the uplink signal is compensated, sending the compensated uplink signal to the satellite, and acquiring the signal offset of the compensated uplink signal calculated by the satellite; correcting the compensated signal offset of the uplink signal based on the compensated signal offset of the uplink signal and a target variation to obtain a target signal offset, wherein the target variation comprises: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
Further, the target parameters include: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
Further, calculating a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, comprising: calculating a frequency offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; calculating a time offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; and determining the frequency offset corresponding to the communication time slot of the uplink and the time offset corresponding to the communication time slot of the uplink as the signal offset of the uplink signal of the ground terminal.
Further, calculating a frequency offset corresponding to the uplink communication timeslot by using the target parameter and the downlink signal, includes: calculating a Doppler offset between the ground terminal and the satellite using the target parameter and the downlink signal, wherein the Doppler offset comprises: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite; and calculating the frequency offset corresponding to the communication time slot of the uplink based on the Doppler offset between the ground terminal and the satellite.
Further, calculating a time offset corresponding to the uplink communication slot by using the target parameter and the downlink signal, includes: calculating the satellite-ground distance and the propagation delay between the ground terminal and the satellite by using the target parameters and the downlink signals; and calculating the time offset corresponding to the communication time slot of the uplink based on the satellite-to-ground distance and the propagation delay.
In a second aspect, an embodiment of the present invention further provides a signal synchronization apparatus for satellite communication, which is applied to a ground terminal, and includes: the device comprises an acquisition unit, a calculation unit, a compensation unit, an execution unit and a correction unit, wherein the acquisition unit is used for acquiring a downlink signal transmitted by a satellite; the calculating unit is configured to calculate a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, where the signal offset includes: the uplink signal is a link signal sent to the satellite by the ground terminal; the compensation unit is configured to compensate the uplink signal by using the signal offset; the execution unit is configured to send a compensated uplink signal to the satellite after the uplink signal is compensated, and obtain a signal offset of the compensated uplink signal calculated by the satellite; the correcting unit is configured to correct the compensated signal offset of the uplink signal based on the compensated signal offset of the uplink signal and a target variation, so as to obtain a target signal offset, where the target variation includes: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
Further, the target parameters include: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
Further, the computing unit is configured to: calculating a frequency offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; calculating a time offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; and determining the frequency offset corresponding to the communication time slot of the uplink and the time offset corresponding to the communication time slot of the uplink as the signal offset of the uplink signal of the ground terminal.
Further, the computing unit is configured to: calculating a Doppler offset between the ground terminal and the satellite using the target parameter and the downlink signal, wherein the Doppler offset comprises: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite; and calculating the frequency offset corresponding to the communication time slot of the uplink based on the Doppler offset between the ground terminal and the satellite.
In a third aspect, the present invention further provides a computer-readable storage medium, on which a computer program is stored, where the computer program is executed by a processor to perform the steps of the method in the first aspect.
In the embodiment of the invention, a downlink signal sent by a satellite is obtained; calculating a signal offset of an uplink signal of the ground terminal based on the downlink signal and the target parameter; compensating the uplink signal with a signal offset; after the uplink signal is compensated, sending the compensated uplink signal to the satellite, and acquiring the signal offset of the compensated uplink signal calculated by the satellite; and correcting the signal offset of the compensated uplink signal based on the signal offset and the target variation of the compensated uplink signal to obtain the target signal offset.
In the embodiment of the invention, the frequency and time compensation is carried out on the uplink signal through the downlink signal and the target parameter, then the ground terminal corrects the signal offset of the compensated uplink signal by utilizing the signal offset of the compensated uplink signal calculated by the satellite.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of a signal synchronization method for satellite communication according to an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating compensation of frequency offset according to an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating compensation of time offset according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a signal synchronization apparatus for satellite communication according to an embodiment of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
in accordance with an embodiment of the present invention, there is provided an embodiment of a method for signal synchronization for satellite communications, wherein the steps illustrated in the flowchart of the figure may be performed in a computer system, such as a set of computer-executable instructions, and wherein, although a logical order is illustrated in the flowchart, in some cases, the steps illustrated or described may be performed in an order different than that illustrated.
Fig. 1 is a flowchart of a signal synchronization method for satellite communication according to an embodiment of the present invention, as shown in fig. 1, the method includes the following steps:
step S102, acquiring a downlink signal sent by a satellite;
it should be noted that the downlink signal is a downlink signal in the current communication process, and each communication process includes an uplink signal and a downlink signal.
Step S104, calculating a signal offset of the uplink signal of the ground terminal based on the downlink signal and a target parameter, wherein the signal offset includes: the uplink signal is a link signal sent to the satellite by the ground terminal;
the target parameters include: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
Step S106, compensating the uplink signal by using the signal offset;
intermediate frequency signal f transmitted by satellite, starting from signal transmitted by satellitezThe frequency of the satellite-borne up-converter is affected by the frequency deviation of the up-conversion frequency source, and the radio frequency signals after frequency conversion are affected by Doppler frequency shift through space transmission. On the ground terminal side, the frequency deviation of the down-conversion frequency source can be superposed into the frequency deviation of the signal, so that the intermediate frequency signal received by the ground terminal is influenced by the up-conversion of the satellite side signal, the down-conversion of the ground terminal side signal and the Doppler frequency difference; the output if signal of the ground terminal needs to compensate for these frequency deviations, and at the same time, the effect of up-conversion on the ground terminal side, the effect of down-conversion on the satellite side signal, and the effect of up-doppler need to be compensated.
As shown in fig. 2, fig. 2 is a schematic diagram of frequency offset compensation.
And setting up and down frequency conversion sources of the satellite to be the same point frequency source, setting up and down frequency conversion sources of the ground terminal to be the same point frequency source, and setting frequency deviation of the frequency sources.
Satellite downlink broadcast frequency deviation delta f measured by ground terminal2Including frequency deviation caused by satellite up-conversion and ground terminal down-conversion, down-going satelliteDoppler deviation f between the groundsdp1And other frequency deviations; the calculated Doppler deviation of the uplink transmission time slot is fdp2。
Uplink frequency compensation df ═ k ([ delta ] f)2-fdp1)-fdp2Wherein
fUFor uplink signal frequency, fDFor the downlink signal frequency, fzAt the intermediate frequency.
As shown in fig. 3, fig. 3 is a schematic diagram of time offset compensation.
After the ground terminal finishes the acquisition of the downlink synchronous mark signal, the mark position is set to a clock timing unit;
the clock timing unit clears the timer at the falling edge of the pulse per second, reads the value of the timer after receiving the capture mark of the baseband and transmits the value to the time delay calculation unit;
setting the synchronization mark specified by the air interface as time t0The receiving time of the synchronization mark measured by the clock timing unit is t1Calculating to obtain the transmission delay t of the lower planetdAnd the satellite-ground transmission time delay t corresponding to uplink transmissionuIf yes, the time delay calculation unit outputs a time delay offset to the sending unit: dt ═ t0-t1+td-tuAnd the delay offset is the offset of the time corresponding to the uplink time slot by taking the local time as the time reference.
Step S108, after the uplink signal is compensated, sending the compensated uplink signal to the satellite, and obtaining the signal offset of the compensated uplink signal calculated by the satellite;
step S110, based on the compensated signal offset of the uplink signal and a target variation, correcting the compensated signal offset of the uplink signal to obtain a target signal offset, where the target variation includes: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
In the embodiment of the invention, the frequency and time compensation is carried out on the uplink signal through the downlink signal and the target parameter, then the ground terminal corrects the signal offset of the compensated uplink signal by utilizing the signal offset of the compensated uplink signal calculated by the satellite.
In a medium-low orbit broadband communication satellite system with a time division and frequency division air interface system adopted by an uplink, due to the problems that satellite-ground propagation delay is changed fast due to rapid movement of a satellite, Doppler frequency deviation is large and Doppler change rate is large due to high communication frequency, frequency deviation caused by frequency conversion is large due to low accuracy of a satellite frequency source, and the like, the risk of time collision and adjacent channel interference of signals among multiple users of an uplink channel of the satellite exists.
In the embodiment of the application, aiming at the problems, the frequency offset and the time error of the downlink broadcast signal are measured, the Doppler offset and the satellite-to-ground transmission delay information which are obtained through the calculation of the terminal information and the satellite ephemeris are combined, the symmetry characteristic of the frequency offset caused by frequency conversion of the satellite and the terminal is fully utilized, the time frequency is compensated, and the time frequency alignment can be realized when the uplink signal of the terminal reaches the satellite. The method is simple and is particularly suitable for a medium and low orbit broadband satellite communication system based on-satellite processing and forwarding.
In the embodiment of the present invention, step S104 includes the following steps:
step S11, calculating a frequency offset corresponding to the uplink communication slot using the target parameter and the downlink signal;
step S12, calculating a time offset corresponding to the uplink communication slot using the target parameter and the downlink signal;
step S13, determining the frequency offset corresponding to the uplink communication timeslot and the time offset corresponding to the uplink communication timeslot as the signal offset of the uplink signal of the ground terminal.
Step S11 includes the following steps:
step S111, calculating a doppler offset between the ground terminal and the satellite by using the target parameter and the downlink signal, wherein the doppler offset includes: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite;
step S112, based on the doppler shift between the ground terminal and the satellite, calculates a frequency shift corresponding to the uplink communication timeslot.
Specifically, the terminal receives a downlink broadcast signal of a satellite, measures frequency deviation according to the broadcast signal, calculates doppler frequency shifts between the downlink and uplink satellites and the terminal respectively by combining position information of the ground terminal, satellite ephemeris, downlink signal transmission time and uplink communication time slot time, and calculates frequency compensation quantity of an uplink signal of the ground terminal by combining frequency deviation measurement and doppler estimation.
Step S12 includes the following steps:
step S121, calculating the satellite-ground distance and the propagation delay between the ground terminal and the satellite by using the target parameters and the downlink signals;
step S122, calculating a time offset corresponding to the uplink communication timeslot based on the satellite-to-ground distance and the propagation delay.
Specifically, the satellite broadcasts a pseudo code signal to a terminal by taking the start of each superframe as a time reference, the terminal performs time deviation measurement after receiving the broadcast signal, calculates the satellite-ground distance and the propagation delay by using the position information of the ground terminal, the satellite ephemeris information, the downlink signal sending time and the uplink communication time slot time, and calculates the time compensation quantity of the uplink signal of the ground terminal by combining the time deviation measurement and the propagation delay calculation.
The following exemplifies the specific effects of the present invention: consider a low earth orbit communications satellite with an orbital altitude of 1000km, a satellite uplink operating frequency of 30GHz and a satellite downlink operating frequency of 20 GHz. The frequency sources of the up-down conversion in the satellite all come from the same point frequency source, the point frequency source is a constant temperature crystal oscillator of 100MHz, the frequency accuracy index is superior to 0.1ppm, and the short-term stability is superior to 5e-13(10 s). Meanwhile, the terminal communicating with the satellite also adopts the same constant-temperature crystal oscillator, and the frequency accuracy is better than 0.1 ppm.
Assuming that the elevation angle of the user terminal to the satellite at a certain time of communication is 55 °, the doppler frequency of the downlink is 245 KHz. Meanwhile, the deviation of the point frequency source on the time star is assumed to be df1At 8Hz (@100MHz), the point source offset at ground is df2The central frequency point of the baseband processing of the satellite is f under-2 Hz (@100MHz)zWhen the frequency deviation of the downlink transmission signal of the satellite is 1.2GHz, the frequency deviation is 2.304KHz, and the frequency deviation reaching the receiving port surface of the terminal amounts to 247.304KHz because the doppler frequency deviation of the satellite is 245 KHz. On the terminal side, the frequency offset after down-conversion is 247.880 KHz. As can be seen from the above, the doppler frequency offset caused by the rapid movement of the satellite accounts for the vast majority of the whole frequency offset, if the ground terminal needs to demodulate the signal, the frequency offset needs to be properly compensated, and the remaining frequency offset may cause deterioration to the demodulation performance, and the specific deterioration degree is related to the signal system, the bandwidth, the demodulation algorithm, and the like. The terminal side can estimate the Doppler frequency offset according to the ephemeris of the satellite and the position information of the terminal, so as to compensate before demodulation.
Since the satellite is oriented to multiple users, the Doppler frequency for each user is shiftedLine compensation is difficult and therefore requires the terrestrial terminal to correct the frequency of the transmitted signal in order to compensate for frequency offsets due to doppler and crystal accuracy. In the present invention, the ground terminal estimates a frequency offset from a baseband reception signal so as to compensate for the frequency offset of the uplink. Assuming that the frequency deviation estimation error for the downlink is 100Hz, the actual uplink compensation frequency is df ═ k × (Δ f)2-fdp1)-fdp21.532 (2880+100) -367500 Hz. After the up-conversion of the ground terminal, the up-line transmission of the satellite and the down-conversion of the satellite, the frequency deviation of the satellite intermediate frequency receiving signal is 100Hz, and the frequency deviation has little influence on the communication of the Ka frequency band, namely, the method can well compensate the frequency deviation and simplify the complexity of satellite demodulation.
Example two:
the embodiment of the present invention further provides a signal synchronization device for satellite communication, where the signal synchronization device for satellite communication is used to execute the signal synchronization method for satellite communication provided in the foregoing content of the embodiment of the present invention, and the following is a detailed description of the signal synchronization device for satellite communication provided in the embodiment of the present invention.
As shown in fig. 4, fig. 4 is a schematic diagram of the signal synchronization apparatus for satellite communication, and the signal synchronization apparatus for satellite communication includes: the device comprises an acquisition unit 10, a calculation unit 20, a compensation unit 30, an execution unit 40 and a correction unit 50.
The acquiring unit 10 is configured to acquire a downlink signal transmitted by a satellite;
the calculating unit 20 is configured to calculate a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, where the signal offset includes: the uplink signal is a link signal sent to the satellite by the ground terminal;
the compensation unit 30 is configured to compensate the uplink signal by using the signal offset;
the execution unit 40 is configured to send a compensated uplink signal to the satellite after the uplink signal is compensated, and obtain a signal offset of the compensated uplink signal calculated by the satellite;
the correcting unit 50 is configured to correct the compensated signal offset of the uplink signal based on the compensated signal offset of the uplink signal and a target variation, so as to obtain a target signal offset, where the target variation includes: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
In the embodiment of the invention, the frequency and time compensation is carried out on the uplink signal through the downlink signal and the target parameter, then the ground terminal corrects the signal offset of the compensated uplink signal by utilizing the signal offset of the compensated uplink signal calculated by the satellite.
Preferably, the target parameters include: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
Preferably, the computing unit is configured to: calculating a frequency offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; calculating a time offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal; and determining the frequency offset corresponding to the communication time slot of the uplink and the time offset corresponding to the communication time slot of the uplink as the signal offset of the uplink signal of the ground terminal.
Preferably, the computing unit is configured to: calculating a Doppler offset between the ground terminal and the satellite using the target parameter and the downlink signal, wherein the Doppler offset comprises: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite; and calculating the frequency offset corresponding to the communication time slot of the uplink based on the Doppler offset between the ground terminal and the satellite.
Preferably, the computing unit is configured to: calculating the satellite-ground distance and the propagation delay between the ground terminal and the satellite by using the target parameters and the downlink signals; and calculating the time offset corresponding to the communication time slot of the uplink based on the satellite-to-ground distance and the propagation delay.
Example three:
the embodiment of the present invention further provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the computer program performs the steps of the method in the first embodiment.
In addition, in the description of the embodiments of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one logical division, and there may be other divisions when actually implemented, and for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some communication interfaces, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A signal synchronization method for satellite communication is applied to a ground terminal, and comprises the following steps:
acquiring a downlink signal transmitted by a satellite;
calculating a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, wherein the signal offset comprises: the uplink signal is a link signal sent to the satellite by the ground terminal;
compensating the uplink signal with the signal offset;
after the uplink signal is compensated, sending the compensated uplink signal to the satellite, and acquiring the signal offset of the compensated uplink signal calculated by the satellite;
correcting the compensated signal offset of the uplink signal based on the compensated signal offset of the uplink signal and a target variation to obtain a target signal offset, wherein the target variation comprises: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
2. The method of claim 1, wherein the target parameters comprise: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
3. The method of claim 2, wherein calculating a signal offset for the uplink signal of the ground terminal based on the downlink signal and a target parameter comprises:
calculating a frequency offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal;
calculating a time offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal;
and determining the frequency offset corresponding to the communication time slot of the uplink and the time offset corresponding to the communication time slot of the uplink as the signal offset of the uplink signal of the ground terminal.
4. The method of claim 3, wherein calculating the frequency offset corresponding to the uplink communication slot using the target parameter and the downlink signal comprises:
calculating a Doppler offset between the ground terminal and the satellite using the target parameter and the downlink signal, wherein the Doppler offset comprises: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite;
and calculating the frequency offset corresponding to the communication time slot of the uplink based on the Doppler offset between the ground terminal and the satellite.
5. The method of claim 3, wherein calculating the time offset corresponding to the uplink communication slot using the target parameter and the downlink signal comprises:
calculating the satellite-ground distance and the propagation delay between the ground terminal and the satellite by using the target parameters and the downlink signals;
and calculating the time offset corresponding to the communication time slot of the uplink based on the satellite-to-ground distance and the propagation delay.
6. A signal synchronization device for satellite communication, applied to a ground terminal, comprises: an acquisition unit, a calculation unit, a compensation unit, an execution unit and a correction unit, wherein,
the acquisition unit is used for acquiring a downlink signal transmitted by a satellite;
the calculating unit is configured to calculate a signal offset of an uplink signal of the ground terminal based on the downlink signal and a target parameter, where the signal offset includes: the uplink signal is a link signal sent to the satellite by the ground terminal;
the compensation unit is configured to compensate the uplink signal by using the signal offset;
the execution unit is configured to send a compensated uplink signal to the satellite after the uplink signal is compensated, and obtain a signal offset of the compensated uplink signal calculated by the satellite;
the correcting unit is configured to correct the compensated signal offset of the uplink signal based on the compensated signal offset of the uplink signal and a target variation, so as to obtain a target signal offset, where the target variation includes: the method comprises the steps of changing Doppler frequency shift between a first communication process and a second communication process, and changing satellite-to-ground distance between the first communication process and the second communication process, wherein the first communication process is a current communication process between the ground terminal and the satellite, and the second communication process is a communication process before the current communication process.
7. The apparatus of claim 6, wherein the target parameters comprise: position information of the ground terminal, satellite ephemeris, downlink signal transmission time, and uplink communication time slot.
8. The apparatus of claim 7, wherein the computing unit is configured to:
calculating a frequency offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal;
calculating a time offset corresponding to a communication time slot of the uplink by using the target parameter and the downlink signal;
and determining the frequency offset corresponding to the communication time slot of the uplink and the time offset corresponding to the communication time slot of the uplink as the signal offset of the uplink signal of the ground terminal.
9. The apparatus of claim 7, wherein the computing unit is configured to:
calculating a Doppler offset between the ground terminal and the satellite using the target parameter and the downlink signal, wherein the Doppler offset comprises: an uplink communication doppler offset between the ground terminal and the satellite, and a downlink communication doppler offset between the ground terminal and the satellite;
and calculating the frequency offset corresponding to the communication time slot of the uplink based on the Doppler offset between the ground terminal and the satellite.
10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method according to any one of the claims 1 to 5.
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