WO2024119562A1 - Method and system for quickly establishing communication link between satellite and ground - Google Patents

Method and system for quickly establishing communication link between satellite and ground Download PDF

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Publication number
WO2024119562A1
WO2024119562A1 PCT/CN2022/143226 CN2022143226W WO2024119562A1 WO 2024119562 A1 WO2024119562 A1 WO 2024119562A1 CN 2022143226 W CN2022143226 W CN 2022143226W WO 2024119562 A1 WO2024119562 A1 WO 2024119562A1
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low
orbit satellite
communication
time
uplink signal
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PCT/CN2022/143226
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French (fr)
Chinese (zh)
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吴琼
蒋林
李奇奋
朱富颖
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北京遥测技术研究所
航天长征火箭技术有限公司
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Publication of WO2024119562A1 publication Critical patent/WO2024119562A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/18523—Satellite systems for providing broadcast service to terrestrial stations, i.e. broadcast satellite service
    • H04B7/18526—Arrangements for data linking, networking or transporting, or for controlling an end to end session
    • 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
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • the invention relates to a method and system for quickly establishing a communication link between a satellite and an earth, belonging to the technical field of satellite communications.
  • some low-orbit satellites and communication terminals use long codes with a period of several days for communication.
  • the Doppler and code phase of the low-orbit long code signal are unknown, it is difficult for the low-orbit satellite and the communication terminal to establish a connection.
  • the code phase of the low-orbit long code signal requires the calculation of the propagation delay between the two.
  • the current method of calculating the propagation delay requires the known low-orbit satellite system time, and then combined with the low-orbit satellite ephemeris and the terminal position, the propagation delay can be calculated; in addition, Doppler compensation requires the known communication terminal clock drift.
  • the common means of obtaining the low-orbit navigation system time and clock drift can be obtained by receiving satellite navigation signals and positioning.
  • This method requires the communication terminal to have the ability to receive satellite navigation signals and locate, and after obtaining, the satellite navigation system time is converted to the low-orbit satellite system time; or the communication terminal has the ability to be timed and keep time, but the communication terminal clock drift cannot be obtained. This makes the design of the communication terminal more complicated, and it needs to have additional navigation and positioning capabilities.
  • the technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a method and system for quickly establishing a communication link between the satellite and the ground, to simply compensate for the low-orbit long code signal, without the need for navigation timing or terminal clock drift, so that the low-orbit satellite and the communication terminal can quickly establish a connection.
  • the technical solution of the present invention is: a method for quickly establishing a communication link between a satellite and a ground, which is applied to a communication terminal, and the method comprises the following steps:
  • the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris.
  • the control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
  • step S1-4 taking the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delaying for a period of time, and obtaining the communication uplink signal transmission time t3 ;
  • step S1-6 configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
  • Another technical solution provided by the present invention is: a method for quickly establishing a communication link between a satellite and an earth, which is applied to a low-orbit satellite, and the method comprises the following steps:
  • the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
  • the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
  • the communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
  • the communication uplink signal is obtained by the communication terminal through the following method:
  • step S2-2-3 using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal reaches the low-orbit satellite at the next full second of the low-orbit satellite;
  • step S2-2-5 Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
  • the next full second time t2 of the low-orbit satellite is:
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
  • ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite
  • ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
  • the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1- ⁇ , wherein ⁇ is the delay to the next full second.
  • the communication terminal adopts an atomic clock.
  • the communication uplink signal Doppler f dop is:
  • k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier;
  • f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
  • the broadcast downlink signal adopts spread spectrum BPSK modulation.
  • the broadcast downlink signal pseudo code is a Gold code.
  • a technical solution of the present invention is: a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
  • a low-orbit satellite sends a broadcast downlink signal to a communication terminal, wherein a control data frame is modulated in the broadcast downlink signal, a start time of a frame header of the control data frame is aligned with an integer second time of the low-orbit satellite, the control data frame includes an integer second time corresponding to a current frame header, control information, and an ephemeris of the low-orbit satellite, and the control information includes an initial phase information of a pseudo-random code used for an uplink signal and a downlink signal when the low-orbit satellite communicates with the communication terminal; and according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next integer second of the low-orbit satellite system time;
  • the communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time.
  • the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication
  • the period of time is 1-2 ⁇ .
  • the method provided by the present invention can use the low-orbit satellite system time at the current frame header moment obtained from the received downlink signal to calculate the next full second launch time of the low-orbit satellite system.
  • the error of this time is only the propagation delay of the low-orbit satellite.
  • the Doppler and code phase accuracy required by the dynamic requirements of the low-orbit satellite fully meet its timing accuracy.
  • the present invention does not need to obtain the communication terminal clock drift, and the Doppler calculation method is simple. Since the communication terminal uses an atomic clock, the clock drift error between the payload and the communication terminal is less than the compensation accuracy requirement of the uplink signal Doppler and can be ignored. The compensation Doppler can be calculated only by tracking the Doppler obtained by the downlink signal.
  • FIG1 is a flow chart of a method according to an embodiment of the present invention.
  • the satellite payload has high accuracy requirements on the Doppler and code phase of the low-orbit long code signal, and the communication terminal needs to accurately compensate for the Doppler and code phase of the uplink transmission signal.
  • the present invention does not require the communication terminal to have navigation timing capability, nor does it need to provide positioning clock drift.
  • the low-orbit satellite system time at the current frame header moment is obtained from the downlink signal, and the propagation delay is ignored, so that the transmission time of the next full second can be obtained to calculate the propagation delay; then the relationship between the broadcast downlink signal Doppler and the communication uplink signal Doppler is used, and the characteristics of the atomic clock with small clock drift are combined to realize the compensation of the uplink transmission signal Doppler and code phase.
  • the method is simple and the accuracy meets the compensation requirements.
  • the core idea of the present invention is to obtain the low-orbit satellite system time of the current frame header moment from the broadcast downlink signal. This time plus one is the low-orbit satellite system launch moment of the next full second. However, there is a propagation delay error. As long as the error meets the timing accuracy and the communication terminal receives the pseudo-random code phase much more than 10ms in advance of the next full second, it will be sufficient.
  • the error between the moment when the communication terminal receives the frame header of the broadcast downlink signal and the full second moment of the low-orbit satellite is in the millisecond level.
  • the maximum acceleration of the low-orbit satellite is about 400Hz/s, and the maximum pseudo-range change rate is about 6000m/s.
  • the maximum propagation delay does not exceed 10ms.
  • the pseudo-range change within 10ms does not exceed 60m/s.
  • the 60m error meets the phase accuracy requirement of the transmission compensation; in addition, the communication terminal will receive the pseudo-random code phase in advance of the next full second, and the advance time is much greater than 10ms. Therefore, even if there is a propagation delay, the next full second moment obtained from the broadcast downlink signal can be used as the uplink signal transmission time, and its timing accuracy is acceptable.
  • Doppler compensation since the terminal uses an atomic clock, its clock drift can be ignored. It is only necessary to calculate the communication uplink signal Doppler based on the broadcast downlink signal Doppler at the time of transmission.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • the present invention provides a method for quickly establishing a communication link between a satellite and a ground, and the method is applied to a communication terminal and comprises the following steps:
  • the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris.
  • the control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
  • step S1-4 using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t3 ; the period of time is 1-2 ⁇ .
  • step S1-6 configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • a method for quickly establishing a communication link between a satellite and an earth comprising the following steps:
  • the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
  • the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
  • the communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
  • the communication uplink signal is obtained by the communication terminal through the following method:
  • step S2-2-3 Based on the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1, a delay of 2 ⁇ is performed to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal arrives at the low-orbit satellite at the next full second of the low-orbit satellite, wherein ⁇ is the propagation delay between the low-orbit satellite and the communication terminal; and the period of time is 1-2 ⁇ .
  • step S2-2-5 Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
  • t 2 , t 1 , and ⁇ t represent the low-orbit satellite system time of the next full second, the low-orbit satellite system time corresponding to the current frame header moment, and the propagation delay error, respectively.
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
  • ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite
  • ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
  • the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1- ⁇ , where ⁇ is the delay to the next full second.
  • the signal Doppler has the following relationship:
  • f track f SV + f D - f R
  • f dop -k ⁇ (f track + 2 ⁇ f R - f sv )
  • f track is the broadcast downlink signal tracking frequency
  • f D is the motion-induced Doppler
  • f SV is the corresponding clock drift of the broadcast downlink signal, in Hz
  • f R is the corresponding clock drift of the broadcast downlink frequency of the communication terminal
  • k is the nominal carrier frequency of the communication uplink signal/nominal carrier frequency of the broadcast downlink signal
  • f dop is the Doppler of the communication uplink signal. Since the communication terminal uses an atomic clock and the payload clock drift is also small, its error is less than the compensation accuracy requirement of the uplink signal Doppler, so f R and f SV can be ignored. Therefore, when the communication terminal uses an atomic clock, the communication uplink signal Doppler f dop is:
  • k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier;
  • f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
  • the broadcast downlink signal adopts spread spectrum BPSK modulation
  • the broadcast downlink signal pseudo code is Gold code
  • Embodiment 3 is a diagrammatic representation of Embodiment 3
  • This embodiment provides a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
  • the low-orbit satellite sends a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the full second time of the low-orbit satellite, and the control data frame includes the full second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, wherein the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal; according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next full second of the low-orbit satellite system time;
  • the communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time.
  • the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication
  • Embodiment 4 is a diagrammatic representation of Embodiment 4:
  • the frequency of the broadcast downlink signal is 1176.45MHz
  • the second pulse can be obtained through frame synchronization, and the low-orbit satellite time corresponding to the control data frame header can be obtained through the telegram, and the Doppler f track of the 1176.45MHz frequency point can be tracked.
  • the signal propagation delay ⁇ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite t 2 is calculated to be 0.003329609 seconds; the low-orbit satellite system time corresponding to its launch time should be:
  • f track -436

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Abstract

The present invention relates to a method and system for quickly establishing a communication link between a satellite and the ground, wherein when a long code system is used in communication with a low-orbit satellite, a communication terminal is required to accurately compensate Doppler and a code phase of an uplink transmission signal. In the method, first, a low-orbit satellite system time at a frame header moment of a control data frame is acquired from a broadcast downlink signal, wherein the time delay difference of the moment can be ignored according to a low-orbit signal dynamic and system design guarantee, and the transmission moment of a communication uplink signal which is received by a low-orbit satellite at the next whole second is obtained, so as to calculate a code phase; and then, by using a relationship between Doppler of the broadcast downlink signal and Doppler of the communication uplink transmission signal combined with the characteristic of an atomic clock having a small clock drift, compensation for the Doppler and code phase of the uplink transmission signal is realized.

Description

一种星地快速建立通信链接的方法和***A method and system for quickly establishing a communication link between satellite and ground
本申请要求于2022年12月09日提交中国专利局、申请号为202211584671.8、发明名称为“一种星地快速建立通信链接的方法和***”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。This application claims the priority of the Chinese patent application filed with the China Patent Office on December 9, 2022, with application number 202211584671.8 and invention name “A method and system for quickly establishing communication links between satellites and the ground”, the entire contents of which are incorporated by reference in this application.
技术领域Technical Field
本发明涉及一种星地快速建立通信链接的方法和***，属于卫星通信技术领域。The invention relates to a method and system for quickly establishing a communication link between a satellite and an earth, belonging to the technical field of satellite communications.
背景技术Background technique
目前有一些低轨卫星和通信终端之间采用周期长达数天的长码进行通信，在低轨长码信号的多普勒、码相位未知的前提下，低轨卫星和通信终端很难建立连接。然而，低轨长码信号的码相位需要计算两者之间的传播延迟，目前计算传播时延的方式需要已知低轨卫星***时间，再结合低轨卫星星历和终端位置，即可计算传播时延；另外，多普勒补偿需要已知通信终端钟漂。，目前可以获取低轨导航***时间和钟漂的常用手段可以采用接收卫星导航信号并定位的方式获取，该方式需要通信终端具备接收卫星导航信号并定位的能力，获取后将卫星导航***时间转换为低轨卫星***时间；或者通信终端具备被授时和守时能力，但还是无法获取通信终端钟漂。这导致通信终端设计较为复杂，需额外具备导航定位能力。At present, some low-orbit satellites and communication terminals use long codes with a period of several days for communication. Under the premise that the Doppler and code phase of the low-orbit long code signal are unknown, it is difficult for the low-orbit satellite and the communication terminal to establish a connection. However, the code phase of the low-orbit long code signal requires the calculation of the propagation delay between the two. The current method of calculating the propagation delay requires the known low-orbit satellite system time, and then combined with the low-orbit satellite ephemeris and the terminal position, the propagation delay can be calculated; in addition, Doppler compensation requires the known communication terminal clock drift. At present, the common means of obtaining the low-orbit navigation system time and clock drift can be obtained by receiving satellite navigation signals and positioning. This method requires the communication terminal to have the ability to receive satellite navigation signals and locate, and after obtaining, the satellite navigation system time is converted to the low-orbit satellite system time; or the communication terminal has the ability to be timed and keep time, but the communication terminal clock drift cannot be obtained. This makes the design of the communication terminal more complicated, and it needs to have additional navigation and positioning capabilities.
发明内容Summary of the invention
本发明的技术解决问题是：克服现有技术不足，提供了一种星地快速建立通信链接的方法和***,对低轨长码信号的简单补偿，无需导航授时也无需提供终端钟漂，就可以使低轨卫星和通信终端快速建立连接。The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a method and system for quickly establishing a communication link between the satellite and the ground, to simply compensate for the low-orbit long code signal, without the need for navigation timing or terminal clock drift, so that the low-orbit satellite and the communication terminal can quickly establish a connection.
本发明的技术解决方案是：一种星地快速建立通信链接的方法，应用于通信终端，所述方法包括如下步骤：The technical solution of the present invention is: a method for quickly establishing a communication link between a satellite and a ground, which is applied to a communication terminal, and the method comprises the following steps:
S1-1、接收低轨卫星发送的广播下行信号，所述广播下行信号中调制控 制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括通信终端的通信上行信号和通信下行信号所使用的伪随机码初相信息；S1-1, receiving a broadcast downlink signal sent by a low-orbit satellite, wherein a control data frame is modulated in the broadcast downlink signal, and the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite. The control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris. The control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
S1-2、实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S1-2, real-time tracking of the low-orbit satellite broadcast downlink signal, when the communication terminal receives the initial phase information of the pseudo-random code and starts communication, it records the low-orbit satellite full second time t 1 corresponding to the start time of the frame header in the control data frame, and restores the second pulse signal corresponding to the reception time of the current control data frame header;
S1-3、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S1-3, according to the low-orbit satellite ephemeris, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 ;
S1-4、以步骤S1-2恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3； S1-4, taking the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delaying for a period of time, and obtaining the communication uplink signal transmission time t3 ;
S1-5、记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop； S1-5, record the broadcast downlink signal tracking Doppler f track corresponding to the communication uplink signal transmission time t 3 , and convert it into the Doppler f dop of the communication uplink signal;
S1-6、按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照步骤S1-5计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，正好为低轨卫星下一整秒时刻，且运动多普勒为零，便于低轨卫星按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻快速捕获并跟踪通信上行信号； S1-6, according to the control information contained in the control data frame, configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
S1-7、按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。S1-7. According to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite and quickly establish a communication link with the low-orbit satellite.
本发明提供的另一个技术方案是：一种星地快速建立通信链接的方法，应用于低轨卫星，所述方法包括如下步骤：Another technical solution provided by the present invention is: a method for quickly establishing a communication link between a satellite and an earth, which is applied to a low-orbit satellite, and the method comprises the following steps:
S2-1、向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；S2-1, sending a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
S2-2、按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻捕获并跟踪通信上行信号，与通信终端快速建立连接；S2-2, according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
所述通信上行信号正好在低轨卫星下一整秒时刻到达低轨卫星，且通信上行信号到达低轨卫星时，运动多普勒为零；The communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
S2-3、按照约定的伪随机码及其初相信息，发送通信下行信号，与通信终端快速建立通信链接。S2-3. Send a communication downlink signal according to the agreed pseudo-random code and its initial phase information, and quickly establish a communication link with the communication terminal.
优选地，所述通信上行信号由通信终端通过如下方法得到：Preferably, the communication uplink signal is obtained by the communication terminal through the following method:
S2-2-1、跟踪低轨卫星广播下行信号，获取控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S2-2-1, tracking the downlink signal broadcast by the low-orbit satellite, obtaining the low-orbit satellite whole second time t 1 corresponding to the start time of the frame header in the control data frame, and restoring the second pulse signal corresponding to the reception time of the current control data frame header;
S2-2-2、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S2-2-2, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 according to the low-orbit satellite ephemeris;
S2-2-3、以步骤S2-2-1恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻； S2-2-3, using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal reaches the low-orbit satellite at the next full second of the low-orbit satellite;
S2-2-4、记录通信上行信号发射时刻t 3的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop，使得通信上行信号到达低轨卫星时，运动多普勒为零； S2-2-4, recording the broadcast downlink signal tracking Doppler ftrack at the communication uplink signal transmission time t3 , and converting it into the Doppler fdop of the communication uplink signal, so that when the communication uplink signal reaches the low-orbit satellite, the motion Doppler is zero;
S2-2-5、按照从控制数据帧中所包含的控制信息配置通信上行信号所使用的伪随机码初相信息，按照步骤S2-2-4计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号。 S2-2-5. Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
优选地，所述低轨卫星下一整秒时刻t 2为： Preferably, the next full second time t2 of the low-orbit satellite is:
t 2＝t 1+1。 t2 = t1 +1.
优选地，所述低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ通过如下方法计算得到： Preferably, the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
Figure PCTCN2022143226-appb-000001
Figure PCTCN2022143226-appb-000001
其中，(x s，y s，z s)为低轨卫星下一整秒时刻t 2对应的卫星位置，(x u，y u，z u)为低轨卫星下一整秒时刻t 2对应的通信终端位置。 Among them, ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite, and ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
优选地，所述通信上行信号的发射时刻t 3所对应的低轨卫星时间为t 1+1-τ，其中，τ为下一整秒时刻的时延。 Preferably, the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1-τ, wherein τ is the delay to the next full second.
优选地，通信终端采用原子钟。Preferably, the communication terminal adopts an atomic clock.
优选地，所述通信上行信号多普勒f dop为： Preferably, the communication uplink signal Doppler f dop is:
f dop＝-k×f track f dop = -k × f track
其中，k为通信上行信号载波标称频率/广播下行信号载波标称频率；f track为通信上行信号发射时刻对应的广播下行信号跟踪多普勒。 Wherein, k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier; f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
优选地，所述广播下行信号采用扩频BPSK调制。Preferably, the broadcast downlink signal adopts spread spectrum BPSK modulation.
优选地，广播下行信号伪码为Gold码。Preferably, the broadcast downlink signal pseudo code is a Gold code.
本发明的有一个技术方案是：一种星地快速建立通信链接的***，该***包括低轨卫星和通信终端；A technical solution of the present invention is: a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
低轨卫星，向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；按照约定的伪随机码及其初相信息，在低轨卫星***时间下一整秒时刻快速捕获并跟踪通信上行信号；A low-orbit satellite sends a broadcast downlink signal to a communication terminal, wherein a control data frame is modulated in the broadcast downlink signal, a start time of a frame header of the control data frame is aligned with an integer second time of the low-orbit satellite, the control data frame includes an integer second time corresponding to a current frame header, control information, and an ephemeris of the low-orbit satellite, and the control information includes an initial phase information of a pseudo-random code used for an uplink signal and a downlink signal when the low-orbit satellite communicates with the communication terminal; and according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next integer second of the low-orbit satellite system time;
通信终端，接收低轨卫星发送的广播下行信号，实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号；根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ；以恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到 通信上行信号发射时刻t 3；记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop；按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻，且运动多普勒为零；按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。 The communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time. When the communication terminal receives the initial phase information of the pseudo-random code and starts communication, the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication uplink signal; configures the pseudo-random code and its initial phase information used by the communication uplink signal according to the control information contained in the control data frame, modulates the carrier of the communication uplink signal according to the calculated Doppler fdop of the communication uplink signal, and transmits the communication uplink signal at the communication uplink signal transmission time t 3. Start sending a communication uplink signal to the low-orbit satellite, so that when the communication uplink signal reaches the low-orbit satellite, it is the next full second of the low-orbit satellite, and the motion Doppler is zero; according to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite, and quickly establish a communication link with the low-orbit satellite.
所述一段时间为1-2τ。The period of time is 1-2τ.
本发明与现有技术相比的有益效果是：The beneficial effects of the present invention compared with the prior art are:
(1)、本方法获取当前卫星导航***时间方式简单。通过本发明所提供的方法可以利用从已接收下行信号获取当前帧头时刻的低轨卫星***时间，计算低轨卫星***的下一整秒发射时刻，该时刻误差仅为低轨卫星的传播时延，对于低轨卫星动态要求的多普勒和码相位精度，完全满足其授时精度。(1) This method is simple to obtain the current satellite navigation system time. The method provided by the present invention can use the low-orbit satellite system time at the current frame header moment obtained from the received downlink signal to calculate the next full second launch time of the low-orbit satellite system. The error of this time is only the propagation delay of the low-orbit satellite. The Doppler and code phase accuracy required by the dynamic requirements of the low-orbit satellite fully meet its timing accuracy.
(2)、本发明无需获取通信终端钟漂，计算多普勒方式简单。由于通信终端采用原子钟，载荷和通信终端的钟漂误差小于上行信号多普勒的补偿精度要求，可以忽略，仅需通过下行信号跟踪获取的多普勒即可计算补偿多普勒。(2) The present invention does not need to obtain the communication terminal clock drift, and the Doppler calculation method is simple. Since the communication terminal uses an atomic clock, the clock drift error between the payload and the communication terminal is less than the compensation accuracy requirement of the uplink signal Doppler and can be ignored. The compensation Doppler can be calculated only by tracking the Doppler obtained by the downlink signal.
附图说明BRIEF DESCRIPTION OF THE DRAWINGS
图1为本发明实施例方法流程图。FIG1 is a flow chart of a method according to an embodiment of the present invention.
具体实施方式Detailed ways
下面结合附图对本发明的具体实施方式进行进一步的详细描述。The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.
卫星载荷对低轨长码信号的多普勒、码相位提出了精度要求，需要通信终端对上行发射信号的多普勒和码相位进行精确补偿。The satellite payload has high accuracy requirements on the Doppler and code phase of the low-orbit long code signal, and the communication terminal needs to accurately compensate for the Doppler and code phase of the uplink transmission signal.
本发明无需通信终端具备导航授时能力，也无需提供定位钟漂。从下行 信号获取当前帧头时刻的低轨卫星***时间，并忽略传播时延，可以获取下一整秒的发射时刻，用来计算传播时延；再利用广播下行信号多普勒与通信上行信号多普勒关系，同时结合原子钟钟漂小的特点，实现对上行发射信号多普勒和码相位的补偿，方法简单且精度满足补偿要求。The present invention does not require the communication terminal to have navigation timing capability, nor does it need to provide positioning clock drift. The low-orbit satellite system time at the current frame header moment is obtained from the downlink signal, and the propagation delay is ignored, so that the transmission time of the next full second can be obtained to calculate the propagation delay; then the relationship between the broadcast downlink signal Doppler and the communication uplink signal Doppler is used, and the characteristics of the atomic clock with small clock drift are combined to realize the compensation of the uplink transmission signal Doppler and code phase. The method is simple and the accuracy meets the compensation requirements.
本发明的核心思想是从广播下行信号获取当前帧头时刻的低轨卫星***时间，该时间加一即为下一整秒的低轨卫星***发射时刻，但存在传播时延误差，只要误差满足授时精度且通信终端提前下一整秒收到伪随机码相位的时间远大于10ms即可。The core idea of the present invention is to obtain the low-orbit satellite system time of the current frame header moment from the broadcast downlink signal. This time plus one is the low-orbit satellite system launch moment of the next full second. However, there is a propagation delay error. As long as the error meets the timing accuracy and the communication terminal receives the pseudo-random code phase much more than 10ms in advance of the next full second, it will be sufficient.
由于低轨卫星轨道高度较低，传播时延在毫秒量级，因此通信终端接收广播下行信号帧头时刻与低轨卫星整秒时刻误差在毫秒量级。低轨卫星的加速度最大约400Hz/s，伪距变化率最大约6000m/s。传播时延最大不超过10ms。那么10ms内伪距变化不超过60m/s。60m误差满足发射补偿的相位精度要求；另外，通信终端会提前下一整秒收到伪随机码相位，提前时间远大于10ms。故即使存在传播时延，从广播下行信号获取的下一整秒时刻可以作为上行信号发射时刻，其授时精度可以接受。Since the orbital altitude of low-orbit satellites is relatively low and the propagation delay is in the millisecond level, the error between the moment when the communication terminal receives the frame header of the broadcast downlink signal and the full second moment of the low-orbit satellite is in the millisecond level. The maximum acceleration of the low-orbit satellite is about 400Hz/s, and the maximum pseudo-range change rate is about 6000m/s. The maximum propagation delay does not exceed 10ms. Then the pseudo-range change within 10ms does not exceed 60m/s. The 60m error meets the phase accuracy requirement of the transmission compensation; in addition, the communication terminal will receive the pseudo-random code phase in advance of the next full second, and the advance time is much greater than 10ms. Therefore, even if there is a propagation delay, the next full second moment obtained from the broadcast downlink signal can be used as the uplink signal transmission time, and its timing accuracy is acceptable.
而对于多普勒补偿，由于终端采用原子钟，其钟漂可以忽略，只需在发射时刻根据广播下行信号多普勒计算出通信上行信号多普勒即可。As for Doppler compensation, since the terminal uses an atomic clock, its clock drift can be ignored. It is only necessary to calculate the communication uplink signal Doppler based on the broadcast downlink signal Doppler at the time of transmission.
实施例1：Embodiment 1:
如图1所示，本发明提供了一种星地快速建立通信链接的方法，该方法应用于通信终端包括如下步骤：As shown in FIG1 , the present invention provides a method for quickly establishing a communication link between a satellite and a ground, and the method is applied to a communication terminal and comprises the following steps:
S1-1、接收低轨卫星发送的广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括通信终端的通信上行信号和通信下行信号所使用的伪随机码初相信息；S1-1, receiving a broadcast downlink signal sent by a low-orbit satellite, wherein a control data frame is modulated in the broadcast downlink signal, and the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite. The control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris. The control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
S1-2、实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间 t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S1-2, real-time tracking of the low-orbit satellite broadcast downlink signal, when the communication terminal receives the initial phase information of the pseudo-random code and starts communication, it records the low-orbit satellite full second time t 1 corresponding to the start time of the frame header in the control data frame, and restores the second pulse signal corresponding to the reception time of the current control data frame header;
S1-3、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S1-3, according to the low-orbit satellite ephemeris, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 ;
S1-4、以步骤S1-2恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3；所述一段时间为1-2τ。 S1-4, using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t3 ; the period of time is 1-2τ.
S1-5、记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop； S1-5, record the broadcast downlink signal tracking Doppler f track corresponding to the communication uplink signal transmission time t 3 , and convert it into the Doppler f dop of the communication uplink signal;
S1-6、按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照步骤S1-5计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，正好为低轨卫星下一整秒时刻，且运动多普勒为零，便于低轨卫星按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻快速捕获并跟踪通信上行信号； S1-6, according to the control information contained in the control data frame, configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is exactly the next full second of the low-orbit satellite, and the motion Doppler is zero, so that the low-orbit satellite can quickly capture and track the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
S1-7、按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。S1-7. According to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite and quickly establish a communication link with the low-orbit satellite.
实施例2：Embodiment 2:
一种星地快速建立通信链接的方法，该方法应用于低轨卫星包括如下步骤：A method for quickly establishing a communication link between a satellite and an earth, the method being applied to a low-orbit satellite and comprising the following steps:
S2-1、向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；S2-1, sending a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
S2-2、按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻捕获并跟踪通信上行信号，与通信终端快速建立连接；S2-2, according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
所述通信上行信号正好在低轨卫星下一整秒时刻到达低轨卫星，且通信 上行信号到达低轨卫星时，运动多普勒为零；The communication uplink signal arrives at the low-orbit satellite exactly at the next full second of the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
S2-3、按照约定的伪随机码及其初相信息，发送通信下行信号，与通信终端快速建立通信链接。S2-3. Send a communication downlink signal according to the agreed pseudo-random code and its initial phase information, and quickly establish a communication link with the communication terminal.
所述通信上行信号由通信终端通过如下方法得到：The communication uplink signal is obtained by the communication terminal through the following method:
S2-2-1、跟踪低轨卫星广播下行信号，获取控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S2-2-1, tracking the downlink signal broadcast by the low-orbit satellite, obtaining the low-orbit satellite whole second time t 1 corresponding to the start time of the frame header in the control data frame, and restoring the second pulse signal corresponding to the reception time of the current control data frame header;
S2-2-2、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S2-2-2, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 according to the low-orbit satellite ephemeris;
S2-2-3、以步骤S2-2-1恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间2τ，得到通信上行信号发射时刻t 3，使得通信上行信号到达低轨卫星时，正好为低轨卫星下一整秒时刻，所述τ为低轨卫星与通信终端之间的传播延迟；所述一段时间为1-2τ。 S2-2-3. Based on the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1, a delay of 2τ is performed to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal arrives at the low-orbit satellite at the next full second of the low-orbit satellite, wherein τ is the propagation delay between the low-orbit satellite and the communication terminal; and the period of time is 1-2τ.
S2-2-4、记录通信上行信号发射时刻t 3的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop，使得； S2-2-4, record the broadcast downlink signal tracking Doppler f track at the communication uplink signal transmission time t 3 , and convert it into the Doppler f dop of the communication uplink signal, so that;
S2-2-5、按照从控制数据帧中所包含的控制信息配置通信上行信号所使用的伪随机码初相信息，按照步骤S2-2-4计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号。 S2-2-5. Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
上述两个实施例中，根据低轨卫星***时间关系，具体为：In the above two embodiments, according to the time relationship of the low-orbit satellite system, specifically:
t 2＝t 1+Δt+1      (1) t 2 = t 1 + Δt + 1 (1)
式中：t 2、t 1、Δt分别表示下一整秒低轨卫星***时间、当前帧头时刻对应的低轨卫星***时间及传播时延误差。 Where: t 2 , t 1 , and Δt represent the low-orbit satellite system time of the next full second, the low-orbit satellite system time corresponding to the current frame header moment, and the propagation delay error, respectively.
根据低轨卫星动态特性，传播时延误差Δt带来的码相位误差影响可以忽略，因此，所述低轨卫星下一整秒时刻t 2为： According to the dynamic characteristics of low-orbit satellites, the influence of the code phase error caused by the propagation delay error Δt can be ignored. Therefore, the next full second time t2 of the low-orbit satellite is:
t 2＝t 1+1。       (2) t2 = t1 +1. (2)
上述两个实施例中，所述低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ通过如下方法计算得到： In the above two embodiments, the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
Figure PCTCN2022143226-appb-000002
Figure PCTCN2022143226-appb-000002
其中，(x s，y s，z s)为低轨卫星下一整秒时刻t 2对应的卫星位置，(x u，y u，z u)为低轨卫星下一整秒时刻t 2对应的通信终端位置。 Among them, ( xs , ys , zs ) is the satellite position corresponding to the next full second time t2 of the low-orbit satellite, and ( xu , yu , zu ) is the communication terminal position corresponding to the next full second time t2 of the low-orbit satellite.
上述两个实施例中，所述通信上行信号的发射时刻t 3所对应的低轨卫星时间为t 1+1-τ，其中，τ为下一整秒时刻的时延。 In the above two embodiments, the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1-τ, where τ is the delay to the next full second.
上述两个实施例中，信号多普勒存在如下关系：In the above two embodiments, the signal Doppler has the following relationship:
f track＝f SV+f D-f R f track = f SV + f D - f R
f dop＝-k×(f track+2×f R-f sv) f dop = -k × (f track + 2 × f R - f sv )
式中：f track为广播下行信号跟踪频率；f D为运动引起多普勒；f SV为广播下行信号对应钟漂，单位Hz；f R为通信终端广播下行频点对应钟漂；k为通信上行信号载波标称频率/广播下行信号载波标称频率；f dop为通信上行信号多普勒。由于通信终端采用了原子钟且载荷钟漂也较小，其误差小于上行信号多普勒的补偿精度要求，因此f R和f SV可忽略，所以，当通信终端采用原子钟时，所述通信上行信号多普勒f dop为： Where: f track is the broadcast downlink signal tracking frequency; f D is the motion-induced Doppler; f SV is the corresponding clock drift of the broadcast downlink signal, in Hz; f R is the corresponding clock drift of the broadcast downlink frequency of the communication terminal; k is the nominal carrier frequency of the communication uplink signal/nominal carrier frequency of the broadcast downlink signal; f dop is the Doppler of the communication uplink signal. Since the communication terminal uses an atomic clock and the payload clock drift is also small, its error is less than the compensation accuracy requirement of the uplink signal Doppler, so f R and f SV can be ignored. Therefore, when the communication terminal uses an atomic clock, the communication uplink signal Doppler f dop is:
f dop＝-k×f track f dop = -k × f track
其中，k为通信上行信号载波标称频率/广播下行信号载波标称频率；f track为通信上行信号发射时刻对应的广播下行信号跟踪多普勒。 Wherein, k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier; f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
上述两个实施例中，优选所述广播下行信号采用扩频BPSK调制，广播下行信号伪码为Gold码。In the above two embodiments, it is preferred that the broadcast downlink signal adopts spread spectrum BPSK modulation, and the broadcast downlink signal pseudo code is Gold code.
实施例3：Embodiment 3:
本实施例提供了一种星地快速建立通信链接的***，该***包括低轨卫星和通信终端；This embodiment provides a system for quickly establishing a communication link between a satellite and a ground, the system comprising a low-orbit satellite and a communication terminal;
低轨卫星，向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据 帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；按照约定的伪随机码及其初相信息，在低轨卫星***时间下一整秒时刻快速捕获并跟踪通信上行信号；The low-orbit satellite sends a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the full second time of the low-orbit satellite, and the control data frame includes the full second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, wherein the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal; according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next full second of the low-orbit satellite system time;
通信终端，接收低轨卫星发送的广播下行信号，实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号；根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ；以恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3；记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop；按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻，且运动多普勒为零；按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。所述一段时间为1-2τ。 The communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time. When the communication terminal receives the initial phase information of the pseudo-random code and starts communication, the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication uplink signal; configures the pseudo-random code and its initial phase information used by the communication uplink signal according to the control information contained in the control data frame, modulates the carrier of the communication uplink signal according to the calculated Doppler fdop of the communication uplink signal, and transmits the communication uplink signal at the communication uplink signal transmission time t 3. Start sending a communication uplink signal to the low-orbit satellite, so that when the communication uplink signal reaches the low-orbit satellite, it is the next full second of the low-orbit satellite, and the motion Doppler is zero; according to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite, and quickly establish a communication link with the low-orbit satellite. The period of time is 1-2τ.
实施例4：Embodiment 4:
以实际搜星为例，广播下行信号频率为1176.45MHz，通信上行信号频率为2020MHz，对应k＝2020/1176.45＝1.718730077776361。当接收到广播下行信号后，通过帧同步可以获取得到秒脉冲，同时通过电文获取控制数据帧帧头对应的低轨卫星时间，并跟踪得到1176.45MHz频点的多普勒f track。假设收到伪随机码相位开始通信时，记录广播下行信号当前帧头时刻对应的低轨卫星时间t 1＝52330秒，得到低轨卫星下一整秒时刻t 2＝52331秒，根据低轨卫星星历和终端位置，计算得到低轨卫星下一整秒时刻t 2所对应的低轨卫星 与通信终端之间的信号传播延迟τ＝0.003329609秒；其发射时刻所对应的低轨卫星***时间应该为： Taking the actual satellite search as an example, the frequency of the broadcast downlink signal is 1176.45MHz, and the frequency of the communication uplink signal is 2020MHz, corresponding to k＝2020/1176.45＝1.718730077776361. After receiving the broadcast downlink signal, the second pulse can be obtained through frame synchronization, and the low-orbit satellite time corresponding to the control data frame header can be obtained through the telegram, and the Doppler f track of the 1176.45MHz frequency point can be tracked. Assuming that when the pseudo-random code phase is received and the communication starts, the low-orbit satellite time t 1 =52330 seconds corresponding to the current frame header of the broadcast downlink signal is recorded, and the next full second of the low-orbit satellite t 2 =52331 seconds is obtained. According to the low-orbit satellite ephemeris and the terminal position, the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite t 2 is calculated to be 0.003329609 seconds; the low-orbit satellite system time corresponding to its launch time should be:
t 3＝52330+1-0.003329609＝52330.996670391 t 3 =52330+1-0.003329609=52330.996670391
另外，记录此时刻下行跟踪多普勒f track＝-436，则按照公式(5)补偿多普勒f dop＝-1.71873×(-436)＝749.3663。 In addition, the downlink tracking Doppler at this moment is recorded as f track =-436, and the Doppler compensation is performed according to formula (5): f dop =-1.71873×(-436)=749.3663.
即在低轨卫星***时间t 3＝52330.996670391时刻发射通信上行信号，并把749.3663Hz直接补偿到发射中频上，即可满足补偿指标要求，卫星载荷可以接收通信上行发射信号，效果理想。 That is, the communication uplink signal is transmitted at the time t 3 =52330.996670391 of the low-orbit satellite system, and 749.3663 Hz is directly compensated to the transmitting intermediate frequency, so that the compensation index requirement can be met, and the satellite payload can receive the communication uplink transmission signal with an ideal effect.
本发明说明书中未作详细描述的内容属于本领域专业技术人员的公知技术。The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims (12)

  1. 一种星地快速建立通信链接的方法，其特征在于，应用于通信终端，所述方法包括如下步骤：A method for quickly establishing a communication link between a satellite and an earth, characterized in that it is applied to a communication terminal and comprises the following steps:
    S1-1、接收低轨卫星发送的广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括通信终端的通信上行信号和通信下行信号所使用的伪随机码初相信息；S1-1, receiving a broadcast downlink signal sent by a low-orbit satellite, wherein a control data frame is modulated in the broadcast downlink signal, and the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite. The control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris. The control information includes the initial phase information of the pseudo-random code used by the communication uplink signal and the communication downlink signal of the communication terminal;
    S1-2、实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S1-2, real-time tracking of the low-orbit satellite broadcast downlink signal, when the communication terminal receives the initial phase information of the pseudo-random code and starts communication, it records the low-orbit satellite full second time t 1 corresponding to the start time of the frame header in the control data frame, and restores the second pulse signal corresponding to the reception time of the current control data frame header;
    S1-3、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S1-3, according to the low-orbit satellite ephemeris, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 ;
    S1-4、以步骤S1-2恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3； S1-4, taking the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S1-2 as a reference, delaying for a period of time, and obtaining the communication uplink signal transmission time t3 ;
    S1-5、记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop； S1-5, record the broadcast downlink signal tracking Doppler f track corresponding to the communication uplink signal transmission time t 3 , and convert it into the Doppler f dop of the communication uplink signal;
    S1-6、按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照步骤S1-5计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻，且运动多普勒为零，低轨卫星按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻快速捕获并跟踪通信上行信号； S1-6, according to the control information contained in the control data frame, configure the pseudo-random code and its initial phase information used by the communication uplink signal, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S1-5, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 , so that when the communication uplink signal arrives at the low-orbit satellite, it is the next full second of the low-orbit satellite, and the motion Doppler is zero, and the low-orbit satellite quickly captures and tracks the communication uplink signal according to the agreed pseudo-random code and its initial phase information at the next full second of the low-orbit satellite;
    S1-7、按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。S1-7. According to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite and quickly establish a communication link with the low-orbit satellite.
  2. 一种星地快速建立通信链接的方法，其特征在于，应用于低轨卫星，所述方法包括如下步骤：A method for quickly establishing a communication link between a satellite and an earth, characterized in that it is applied to a low-orbit satellite, and the method comprises the following steps:
    S2-1、向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；S2-1, sending a broadcast downlink signal to the communication terminal, wherein the broadcast downlink signal modulates a control data frame, wherein the start time of the frame header of the control data frame is aligned with the whole second time of the low-orbit satellite, and the control data frame includes the whole second time corresponding to the current frame header, control information, and low-orbit satellite ephemeris, and the control information includes the initial phase information of the pseudo-random code used for the uplink signal and the downlink signal when the low-orbit satellite communicates with the communication terminal;
    S2-2、按照约定的伪随机码及其初相信息，在低轨卫星下一整秒时刻捕获并跟踪通信上行信号，与通信终端快速建立连接；S2-2, according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is captured and tracked in the next full second of the low-orbit satellite, and a connection is quickly established with the communication terminal;
    所述通信上行信号在低轨卫星下一整秒时刻到达低轨卫星，且通信上行信号到达低轨卫星时，运动多普勒为零；The communication uplink signal arrives at the low-orbit satellite in the next full second from the low-orbit satellite, and when the communication uplink signal arrives at the low-orbit satellite, the motion Doppler is zero;
    S2-3、按照约定的伪随机码及其初相信息，发送通信下行信号，与通信终端快速建立通信链接。S2-3. Send a communication downlink signal according to the agreed pseudo-random code and its initial phase information, and quickly establish a communication link with the communication terminal.
  3. 根据权利要求2所述的一种星地快速建立通信链接的方法，其特征在于，所述通信上行信号由通信终端通过如下方法得到：The method for quickly establishing a satellite-to-ground communication link according to claim 2 is characterized in that the communication uplink signal is obtained by the communication terminal through the following method:
    S2-2-1、跟踪低轨卫星广播下行信号，获取控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号； S2-2-1, tracking the downlink signal broadcast by the low-orbit satellite, obtaining the low-orbit satellite whole second time t 1 corresponding to the start time of the frame header in the control data frame, and restoring the second pulse signal corresponding to the reception time of the current control data frame header;
    S2-2-2、根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ； S2-2-2, calculating the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 according to the low-orbit satellite ephemeris;
    S2-2-3、以步骤S2-2-1恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻； S2-2-3, using the pulse-per-second signal corresponding to the reception time of the current control data frame header restored in step S2-2-1 as a reference, delay for a period of time to obtain the communication uplink signal transmission time t 3 , so that the communication uplink signal reaches the low-orbit satellite at the next full second of the low-orbit satellite;
    S2-2-4、记录通信上行信号发射时刻t 3的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop，使通信上行信号到达低轨卫星时，运动多普勒为零； S2-2-4, recording the broadcast downlink signal tracking Doppler f track at the time t 3 when the communication uplink signal is transmitted, and converting it into the Doppler f dop of the communication uplink signal, so that the motion Doppler of the communication uplink signal is zero when it reaches the low-orbit satellite;
    S2-2-5、按照从控制数据帧中所包含的控制信息配置通信上行信号所使用的伪随机码初相信息，按照步骤S2-2-4计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送 通信上行信号。 S2-2-5. Configure the initial phase information of the pseudo-random code used for the communication uplink signal according to the control information contained in the control data frame, modulate the carrier of the communication uplink signal according to the Doppler f dop of the communication uplink signal calculated in step S2-2-4, and start sending the communication uplink signal to the low-orbit satellite at the communication uplink signal transmission time t 3 .
  4. 根据权利要求1或3任一项所述的一种星地快速建立通信链接的方法，其特征在于所述低轨卫星下一整秒时刻t 2为： The method for quickly establishing a communication link between a satellite and a ground according to any one of claims 1 or 3 is characterized in that the next full second time t2 of the low-orbit satellite is:
    t 2＝t 1+1。 t2 = t1 +1.
  5. 根据权利要求1或3任一项所述的一种星地快速建立通信链接的方法，其特征在于所述低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ通过如下方法计算得到： According to a method for quickly establishing a satellite-to-ground communication link according to any one of claims 1 or 3, it is characterized in that the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second of the low-orbit satellite at time t2 is calculated by the following method:
    Figure PCTCN2022143226-appb-100001
    Figure PCTCN2022143226-appb-100001
    其中，(x s,y s,z s)为低轨卫星下一整秒时刻t 2对应的卫星位置，(x u,y u,z u)为低轨卫星下一整秒时刻t 2对应的通信终端位置。 Among them, ( xs , ys , zs ) is the satellite position corresponding to the next full second of the low-orbit satellite at time t2 , and ( xu , yu , zu ) is the communication terminal position corresponding to the next full second of the low-orbit satellite at time t2 .
  6. 根据权利要求1或3任一项所述的一种低轨卫星与通信终端快速建立链接的方法，其特征在于所述通信上行信号的发射时刻t 3所对应的低轨卫星时间为t 1+1-τ，其中，τ为下一整秒时刻的时延。 The method for quickly establishing a link between a low-orbit satellite and a communication terminal according to any one of claims 1 or 3 is characterized in that the low-orbit satellite time corresponding to the transmission time t3 of the communication uplink signal is t1 +1-τ, wherein τ is the delay to the next full second.
  7. 根据权利要求1或3任一项所述的一种低轨卫星与通信终端快速建立链接的方法，其特征在于通信终端采用原子钟。A method for quickly establishing a link between a low-orbit satellite and a communication terminal according to any one of claims 1 or 3, characterized in that the communication terminal uses an atomic clock.
  8. 根据权利要求7所述的一种低轨卫星与通信终端快速建立链接的方法，其特征在于所述通信上行信号多普勒f dop为： According to claim 7, a method for quickly establishing a link between a low-orbit satellite and a communication terminal is characterized in that the communication uplink signal Doppler f dop is:
    f dop＝-k×f track f dop = -k × f track
    其中，k为通信上行信号载波标称频率/广播下行信号载波标称频率；f track为通信上行信号发射时刻对应的广播下行信号跟踪多普勒。 Wherein, k is the nominal frequency of the communication uplink signal carrier/the nominal frequency of the broadcast downlink signal carrier; f track is the tracking Doppler of the broadcast downlink signal corresponding to the communication uplink signal transmission time.
  9. 根据权利要求1或3任一项所述的一种低轨卫星与通信终端快速建立链接的方法，其特征在于所述广播下行信号采用扩频BPSK调制。According to a method for quickly establishing a link between a low-orbit satellite and a communication terminal as described in any one of claims 1 or 3, it is characterized in that the broadcast downlink signal adopts spread spectrum BPSK modulation.
  10. 根据权利要求1或3任一项所述的一种低轨卫星与通信终端快速建立链接的方法，其特征在于广播下行信号伪码为Gold码。According to a method for quickly establishing a link between a low-orbit satellite and a communication terminal as described in any one of claims 1 or 3, it is characterized in that the broadcast downlink signal pseudo code is a Gold code.
  11. 一种星地快速建立通信链接的***，其特征在于包括低轨卫星和通信终端；A system for quickly establishing a communication link between a satellite and an earth, characterized by comprising a low-orbit satellite and a communication terminal;
    低轨卫星，向通信终端发送广播下行信号，所述广播下行信号中调制控制数据帧，控制数据帧的帧头起始时刻与低轨卫星整秒时刻对齐，控制数据帧中包括当前帧头对应整秒时间、控制信息、低轨卫星星历，控制信息包括低轨卫星与通信终端通信时上行信号和下行信号所使用的伪随机码初相信息；按照约定的伪随机码及其初相信息，在低轨卫星***时间下一整秒时刻快速捕获并跟踪通信上行信号；A low-orbit satellite sends a broadcast downlink signal to a communication terminal, wherein a control data frame is modulated in the broadcast downlink signal, a start time of a frame header of the control data frame is aligned with an integer second time of the low-orbit satellite, the control data frame includes an integer second time corresponding to a current frame header, control information, and an ephemeris of the low-orbit satellite, and the control information includes an initial phase information of a pseudo-random code used for an uplink signal and a downlink signal when the low-orbit satellite communicates with the communication terminal; and according to the agreed pseudo-random code and its initial phase information, the communication uplink signal is quickly captured and tracked at the next integer second of the low-orbit satellite system time;
    通信终端，接收低轨卫星发送的广播下行信号，实时跟踪低轨卫星广播下行信号，当通信终端收到伪随机码初相信息开始通信时，记录控制数据帧中帧头起始时刻对应的低轨卫星整秒时间t 1，并恢复出当前控制数据帧帧头接收时刻对应的秒脉冲信号；根据低轨卫星星历，计算低轨卫星下一整秒时刻t 2所对应的低轨卫星与通信终端之间的信号传播延迟τ；以恢复出的当前控制数据帧帧头接收时刻对应的秒脉冲信号为基准，延迟一段时间，得到通信上行信号发射时刻t 3；记录通信上行信号发射时刻t 3对应的广播下行信号跟踪多普勒f track，并换算成通信上行信号的多普勒f dop；按照从控制数据帧中所包含的控制信息，配置通信上行信号所使用的伪随机码及其初相信息，按照计算的通信上行信号的多普勒f dop调制通信上行信号的载波，在通信上行信号发射时刻t 3开始向低轨卫星发送通信上行信号，使得通信上行信号到达低轨卫星时，为低轨卫星下一整秒时刻，且运动多普勒为零；按照伪随机码及其初相信息，接收低轨卫星发送的通信下行信号，与低轨卫星快速建立通信链接。 The communication terminal receives the broadcast downlink signal sent by the low-orbit satellite and tracks the broadcast downlink signal of the low-orbit satellite in real time. When the communication terminal receives the initial phase information of the pseudo-random code and starts communication, the communication terminal records the low-orbit satellite full second time t1 corresponding to the start time of the frame header in the control data frame, and recovers the second pulse signal corresponding to the reception time of the current control data frame header; calculates the signal propagation delay τ between the low-orbit satellite and the communication terminal corresponding to the next full second time t2 of the low-orbit satellite according to the low-orbit satellite ephemeris; takes the restored second pulse signal corresponding to the reception time of the current control data frame header as a reference, delays for a period of time, and obtains the communication uplink signal transmission time t3 ; records the broadcast downlink signal tracking Doppler ftrack corresponding to the communication uplink signal transmission time t3 , and converts it into the Doppler fdop of the communication uplink signal; configures the pseudo-random code and its initial phase information used by the communication uplink signal according to the control information contained in the control data frame, modulates the carrier of the communication uplink signal according to the calculated Doppler fdop of the communication uplink signal, and transmits the communication uplink signal at the communication uplink signal transmission time t 3. Start sending a communication uplink signal to the low-orbit satellite, so that when the communication uplink signal reaches the low-orbit satellite, it is the next full second of the low-orbit satellite, and the motion Doppler is zero; according to the pseudo-random code and its initial phase information, receive the communication downlink signal sent by the low-orbit satellite, and quickly establish a communication link with the low-orbit satellite.
  12. 根据权利要求1所述的一种星地快速建立通信链接的***，其特征在于所述一段时间为1-2τ。According to the system for quickly establishing a satellite-to-ground communication link according to claim 1, it is characterized in that the period of time is 1-2τ.
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