CN116094579B

CN116094579B - High-low speed cooperative low-orbit satellite communication system and method

Info

Publication number: CN116094579B
Application number: CN202310366939.9A
Authority: CN
Inventors: 陈建中; 胡宇波; 陶伟; 汤刚刚; 汤玮珉; 杨宏博; 朱湘兰; 吕亚静; 张玉奇
Original assignee: Hunan Jingling Zhilian Information Technology Co ltd
Current assignee: Hunan Jingling Zhilian Information Technology Co ltd
Priority date: 2023-04-07
Filing date: 2023-04-07
Publication date: 2023-06-30
Anticipated expiration: 2043-04-07
Also published as: CN116094579A

Abstract

The application relates to a high-low speed cooperative low-orbit satellite communication system and a method. The system comprises: a Ka phased array antenna, an L receiving antenna, an L transmitting antenna and a transceiver; the Ka phased array antenna, the L receiving antenna and the L transmitting antenna are respectively in communication connection with the transceiver; the transceiver is respectively in communication connection with the star service component and the data transmission component; the L receiving antenna is used for receiving an L frequency band uplink instruction sent by the ground terminal; the ground terminal comprises a ground L station and a ground K station; the L transmitting antenna is used for transmitting L frequency band downlink low-speed data to the appointed ground terminal and broadcasting navigation data to the ground terminal in the service area; the Ka phased array antenna is used for sending Ka frequency band downlink high-speed data to the appointed ground terminal; the transceiver is used for sending the task demand data to the corresponding antenna and sending the telemetry and remote control data to the L transmitting antenna. The method can realize wide-area broadcasting and point-to-point transmission.

Description

High-low speed cooperative low-orbit satellite communication system and method

Technical Field

The present disclosure relates to the field of satellite communications technologies, and in particular, to a low-orbit satellite communications system and method for high-low speed coordination.

Background

After the 21 st century, the rapid development of the industries of computers, micro-electro-mechanical systems, advanced manufacturing and the like promotes the upgrading and updating of communication technology and microsatellite technology, so that the satellite communication cost is reduced, and the low-orbit satellite communication constellation shows a broad application prospect. In the satellite communication field, because signal interference on similar frequencies does not allow different satellite communication systems to share frequencies in principle internationally, the frequencies become the most precious resources, particularly for low-orbit satellites, relatively wide bandwidths are helpful for improving communication capacity, and reasonable scheduling of satellite frequency bands is more critical for effective utilization of resources.

Low-orbit communication satellite systems can be classified into two types, mobile and broadband, according to the application direction and the supported services. The low-orbit mobile communication satellite system adopts L, S low-frequency band operation, mainly uses medium-low bandwidth service, and supports the service of the handheld mobile communication oriented and low-power consumption miniaturized Internet of things; the low-orbit broadband communication satellite system is also called as a low-orbit high-flux satellite system, works in high frequency bands such as Ku, ka, Q/V and the like, has a large number of satellites, mainly supports medium-high speed service, and supports services such as Internet access, network node interconnection, base station backhaul and the like. The communication system acts as a core system for the communication satellite, and its design will directly affect the performance of the communication satellite. With the continuous development of technology, the compatibility requirement of the communication satellite on the working frequency band is also increasing.

However, the conventional communication system often adopts a single working frequency band for communication, and there are few communication systems capable of utilizing the high frequency band and the low frequency band to cooperatively work, so that in order to meet the development requirement of the communication satellite, a new communication system for the communication satellite needs to be designed.

Disclosure of Invention

In view of the foregoing, it is desirable to provide a high-low speed cooperative low-orbit satellite communication system and method.

A high-low speed cooperative low orbit satellite communication system, the system comprising:

a Ka phased array antenna, an L receiving antenna, an L transmitting antenna and a transceiver; the Ka phased array antenna, the L receiving antenna and the L transmitting antenna are respectively in communication connection with the transceiver; the transceiver is respectively in communication connection with the star service component and the data transmission component;

the L receiving antenna is used for receiving an L frequency band uplink instruction sent by the ground terminal; the ground terminal comprises a ground L station and a ground K station;

the L transmitting antenna is used for transmitting L frequency band downlink low-speed data to a specified ground terminal and broadcasting navigation data to the ground terminal in a service area;

the Ka phased array antenna is used for sending Ka frequency band downlink high-speed data to the appointed ground terminal;

The transceiver is used for receiving the L frequency band uplink instruction, obtaining task demand data according to the L frequency band uplink instruction, sending the task demand data to a corresponding antenna, receiving telemetry and remote control data sent by a star service component, and sending the telemetry and remote control data to an L transmitting antenna; the task demand data comprises L-band downlink low-speed data or Ka-band downlink high-speed data.

In one embodiment, the method further comprises: the transceiver is also used for receiving the beam pointing adjustment information sent by the star service component so as to adjust the beam pointing; the beam pointing adjustment information includes satellite orbit information, satellite position information, and satellite attitude information.

In one embodiment, the method further comprises: the ground L station comprises an L central station, an L mobile station and an L portable terminal; the ground K stations include a K central station and a K mobile station.

In one embodiment, the method further comprises: the working modes of the system comprise an L-band working mode, a Ka-band working mode and a combined working mode; the working modes of the L wave band comprise an L processing forwarding mode, an L measurement and control backup mode, an L broadcasting mode and an L service pushing mode; the working mode of the L wave band works in a time-sharing way; the working mode of the Ka wave band comprises a Ka data transmission mode; the combined working mode comprises four modes obtained by respectively combining the Ka data transmission mode with four working modes of an L wave band; and in the combined working mode, the Ka data transmission mode and the L-band working mode work simultaneously.

In one embodiment, the method further comprises: the system switches working modes through an S measurement and control link control mode or an L communication link control mode; the S measurement and control link control mode comprises that a star component analyzes a control instruction of the uplink of the measurement and control link to obtain instruction information, and the working mode of the communication system is controlled through a CAN bus according to the instruction information; the L communication link control mode comprises that the star service component analyzes a remote control telemetry mode control instruction sent by the ground L station to obtain instruction information, and the working mode of the communication system is controlled according to the instruction information through the CAN bus.

In one embodiment, the method further comprises: the transceiver analyzes the L-band uplink instruction, correspondingly generates a series of required star-service related instructions, and forwards the star-service related instructions to a star-service assembly; the star-service related instruction comprises a data transmission solid-memory playback instruction and a data transmission solid-memory stop instruction; and the data processing module of the data transmission component plays back the stored data of the fixed storage designated partition according to the data transmission fixed storage playback instruction and the data transmission fixed storage stopping instruction sent by the star service component to obtain the task demand data.

In one embodiment, the method further comprises: the data transmission assembly sets the communication rate of the data transmission bus according to the bus instruction, and communicates with the transceiver according to the set communication rate; the data transmission component communicates with the transceiver according to a four-wire system protocol; the communication rates include 2Mbps, 10Mbps, and 20Mbps.

In one embodiment, the method further comprises: the transceiver is connected with the star service assembly through a star service bus; the star service bus comprises a CAN bus

A bus; the CAN bus and->

Buses are backup; the transceiver is connected with the data transmission assembly through a data transmission bus; the data transfer bus includes an LVDS bus.

In one embodiment, the method further comprises: an L-band interface specification and a Ka-band interface specification; the L frequency band interface specification specifies that data is transmitted in an L frequency band by adopting an incoherent direct sequence spread spectrum transmission system, a downlink frame format comprises a frame synchronization code and a data field, and an uplink frame format comprises the frame synchronization code and the data field; the data field of the downlink frame comprises a mode word, a frame count, original data and RS check bits; the original data of the downlink frame comprises telemetry data, original data and uplink forwarding data; the data field of the uplink frame comprises a mode word, original data and a check bit field, and the original data of the uplink frame comprises star service data and uplink forwarding; the Ka frequency band interface specification specifies that a data transmission frame format of the Ka frequency band comprises a synchronization word, a version number, a spacecraft identifier, a virtual channel data frame count, a signaling field, a VCDU data unit and a VCDU check field.

A method of high and low speed cooperative low orbit satellite communication, the method comprising:

receiving an L-band uplink instruction of a ground terminal;

obtaining L-band downlink low-speed data or Ka-band downlink high-speed data according to the L-band uplink instruction, sending the L-band downlink low-speed data to an L-transmitting antenna, and sending the Ka-band downlink high-speed data to a Ka phased array antenna so as to realize point-to-point communication;

and acquiring telemetry data and remote control data, acquiring navigation data according to the telemetry data and the remote control data, and broadcasting the navigation data to ground terminals in a service area through an L transmitting antenna.

According to the high-low speed cooperative low-orbit satellite communication system and the method, the L receiving and transmitting antenna and the Ka phased array antenna are arranged in the space section, the ground L station and the ground Ka station are arranged at the ground terminal, the communication system compatible with high-frequency band and low-frequency band operation is provided, and the transceiver can realize communication with the satellite component and the data transmission component, so that the communication system can cooperatively work by utilizing high-low speed data transmission rate. The communication system can provide standard uplink and downlink services, the uplink provides the service for transmitting the reliability instructions to the space-based platform, the downlink can realize wide-area broadcasting and point-to-point transmission, and the service for transmitting data to the space, ground and sea platforms is provided.

Drawings

FIG. 1 is a block diagram of a low-orbit satellite communication system with high-low speed coordination in one embodiment;

FIG. 2 is a schematic diagram of a low-orbit satellite communication system with high-low speed cooperation in one embodiment;

FIG. 3 is a schematic information flow diagram of an L-process forwarding mode in one embodiment;

FIG. 4 is a schematic information flow diagram of an L measurement and control backup mode in one embodiment;

FIG. 5 is a schematic diagram of an information flow of an L-broadcast mode in one embodiment;

FIG. 6 is a schematic information flow diagram of a Ka data transfer mode in one embodiment;

FIG. 7 is a schematic diagram of a downlink 4Kbps processing flow in one embodiment;

FIG. 8 is a schematic diagram of a downstream 32Kbps processing flow in one embodiment;

FIG. 9 is a schematic diagram of an upstream process flow in one embodiment;

FIG. 10 is a schematic diagram of the operating principle of an RS (255,223) encoder in one embodiment;

FIG. 11 is a block diagram of RS encoding with an interleaving depth of 4 in one embodiment;

FIG. 12 is a block diagram of RS encoding without interleaving in one embodiment;

FIG. 13 is a schematic diagram of the convolution (2, 1, 7) in one embodiment;

FIG. 14 is a schematic diagram of a downlink frame format in one embodiment;

FIG. 15 is a schematic diagram of an uplink frame format according to one embodiment;

FIG. 16 is a diagram illustrating scrambling logic specified by the L-band interface specification in one embodiment;

FIG. 17 is a schematic diagram of an interface between a data transfer component and a transceiver in one embodiment;

FIG. 18 is a timing diagram of an interface for communication of data transmission component outputs to a transceiver in one embodiment;

FIG. 19 is a diagram illustrating a format of a data transmission frame in one embodiment;

FIG. 20 is a diagram of Ka data information flow in one embodiment;

FIG. 21 is a diagram of scrambling logic specified by the Ka band interface Specification, in one embodiment;

FIG. 22 is a schematic diagram of an LVDS interface circuit of a low-rail satellite communication system for receiving high-low speed coordination in one embodiment;

FIG. 23 is a flow chart of a method of low-orbit satellite communication for high-low speed coordination in one embodiment;

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

The high-low speed cooperative low-orbit satellite communication system is a full duplex anti-interference terminal device, works in the L frequency band and the Ka frequency band, and can provide 'standard' uplink and downlink services: the uplink provides a service for transmitting the reliability instruction to the space-based platform, and the uplink instruction comprises a satellite remote control instruction and a ground terminal task instruction; the downlink can be broadcast in a wide area, or can be transmitted in a point-to-point manner, and provides a service for transmitting data to an empty, ground and sea platform.

In one embodiment, as shown in fig. 1, there is provided a high-low speed cooperative low-orbit satellite communication system comprising:

the L transmitting antenna is used for transmitting L frequency band downlink low-speed data to the appointed ground terminal and broadcasting navigation data to the ground terminal in the service area;

the transceiver is used for receiving the L-band uplink instruction, obtaining task demand data according to the L-band uplink instruction, sending the task demand data to the corresponding antenna, receiving telemetry and remote control data sent by the star service component, and sending the telemetry and remote control data to the L-emission antenna; the task demand data includes L-band downlink low-speed data or Ka-band downlink high-speed data.

The antenna is arranged outside the cabin, the L receiving and transmitting antenna is mainly responsible for receiving and transmitting L frequency band data, the Ka phased array antenna is mainly responsible for amplifying and amplitude-phase control of Ka radio frequency signals and transmitting the Ka radio frequency signals to the ground, the Ka phased array antenna comprises a transmitting assembly, an antenna array and an external component, the transceiver is arranged in the cabin and used for completing primary power supply processing of a communication system, completing interface communication with a satellite assembly and a data transmission assembly, interface communication with a satellite center computer, data modulation coding, channel signal up-down conversion processing, beam pointing control processing and other functions, and the transceiver comprises a power supply, a baseband, a Ka transmitting channel, an L receiving and transmitting channel and the like. The hardware equipment configured by the communication system comprises a transceiver, a Ka phased array antenna, an L receiving antenna, an L transmitting antenna, a Ka transmitting high-frequency cable, an L transmitting high-frequency cable and an L receiving high-frequency cable, wherein matched software is communication system processing software and is arranged in the transceiver.

In the high-low speed cooperative low-orbit satellite communication system, the L receiving and transmitting antenna and the Ka phased array antenna are arranged in the space section, the ground L station and the ground Ka station are arranged at the ground terminal, the communication system compatible with high-frequency band and low-frequency band operation is provided, and the transceiver can realize communication with the satellite component and the data transmission component, so that the communication system can cooperatively operate by utilizing high-low speed data transmission rate. The communication system can provide standard uplink and downlink services, the uplink provides the service for transmitting the reliability instructions to the space-based platform, the downlink can realize wide-area broadcasting and point-to-point transmission, and the service for transmitting data to the space, ground and sea platforms is provided.

The above-described low-orbit satellite communication system with high-low speed cooperation may be implemented in whole or in part by software, hardware, or a combination thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.

The high-low speed cooperative low-orbit satellite communication system has the functions of data low-speed distribution function, data low-speed broadcasting function, data high-speed distribution function, uplink low-speed receiving function, state monitoring and satellite command processing function, the transmitting channel has the functions of channel coding, scrambling, modulating, amplifying, filtering and transmitting baseband data, and the receiving channel has the functions of receiving, filtering, amplifying, demodulating, descrambling and channel decoding radio-frequency signals to obtain baseband information. The data low-speed distribution function refers to sending L-band downlink low-speed data to a terminal according to the data requirement of the ground terminal, the data low-speed broadcasting function refers to actively sending the L-band downlink low-speed data to the ground terminal, the data high-speed distribution function refers to sending Ka-band downlink high-speed data to the terminal according to the data requirement of the ground terminal, and CAN provide services for a plurality of users through beam agility according to the position information of the terminal, the uplink low-speed receiving function refers to receiving and demodulating the L-band uplink low-speed instruction, formatting data and the like of the ground terminal, completing the analysis response of the uplink instruction and the data buffer forwarding, transmitting the L-band downlink low-speed instruction and the data buffer forwarding to a star service component through a CAN bus, and the state monitoring and star service instruction processing function refers to completing the acquisition of working state information and processing of the star service component; and receiving instruction information from the star service component and controlling the working state of the star service component.

In one embodiment, the transceiver is coupled to the star subassembly via a star bus; the star service bus comprises a CAN bus

A bus; CAN bus and->

In this embodiment, the interface relationship between the transceiver and the star service component includes: the high-low speed cooperative low-orbit satellite communication system completes the startup and shutdown of the equipment by receiving 2 OC instructions provided by the star service; telemetry and remote control data of the high-low speed cooperative low-orbit satellite communication system are transmitted through a satellite bus, and the bus is in the form of a CAN bus,

Buses are backups of each other. CAN bus communication speed is 500kbps, physical layer accords with CAN technical specification 2.0A, and link layer accords with CAN technical specification 2.0A->

The bus communication rate is 220kbps; the satellite computer also feeds back necessary information for adjusting beam pointing of auxiliary communication systems such as satellite orbits, positions, postures and the like to a low-orbit satellite communication system with high-low speed coordination; other interface requirements must conform to the CAN bus communication protocol @, ">

Bus communication protocol "," star subsystem and communication system data engagement ", and IDS table requirements. The interface relation between the transceiver and the data transmission is that the data of the low-orbit satellite communication system with high-low speed cooperation can be played back from the storage area by the data transmission component according to the instruction; the interface mode of the high-low speed cooperative low-orbit satellite communication system and the data transmission component is an LVDS interface, and the communication speed can be switched between 2Mbps/10Mbps/20Mbps, and the system comprises four paths of signals including gating, IQ data and clock.

In one embodiment, the transceiver is further configured to receive beam pointing adjustment information sent by the star component to adjust beam pointing; the beam pointing adjustment information includes satellite orbit information, satellite position information, and satellite attitude information.

In this embodiment, the low-orbit satellite communication system with high-low speed cooperation is composed of a regional mobile beam and a wide-area coverage beam, and mainly completes tasks such as task uploading, data wide-area broadcasting, data directional broadcasting and the like, and is an important component for guaranteeing application information service of a mobile satellite. Point-to-point communication can be achieved by using regional mobile beams, and wide-area broadcasting of communication navigation data can be achieved by using wide-area coverage beams.

In one embodiment, as shown in fig. 2, there is provided a schematic diagram of a low-orbit satellite communication system overview of high-low speed cooperation, and the ground L station includes an L central station, an L mobile station and an L portable terminal; the ground K stations include a K central station and a K mobile station. In this embodiment, the satellite communication system is composed of a space part (satellite) and ground users, and the satellite communication system is divided into: a Ka transmitting link, an L transmitting link and an L receiving link; the types of the ground user terminals are divided into: l-center station (stationary), ka-center station (stationary), L-mobile station, ka-mobile station, L-portable terminal.

In one embodiment, the modes of operation of the system include an L-band mode of operation, a Ka-band mode of operation, and a combined mode of operation; the working modes of the L wave band comprise an L processing forwarding mode, an L measurement and control backup mode, an L broadcasting mode and an L service pushing mode; the working mode of the L wave band works in a time-sharing way; the working mode of the Ka wave band comprises a Ka data transmission mode; the combined working mode comprises four modes obtained by respectively combining the Ka data transmission mode with four working modes of an L wave band; in the combined working mode, the Ka data transmission mode and the L-band working mode work simultaneously.

Specifically, as shown in fig. 3, an information flow diagram of an L processing forwarding mode is provided, where the downlink transmission rate of the L band of the communication link is defaulted to 4Kbps, when uplink data needs to be distributed, the data to be distributed is directly broadcasted in a specified format, if there is no broadcast data to be broadcasted, idle data with the rate of 4Kbps is broadcasted in the specified format, and when the communication link works in the L processing forwarding mode, the broadcast data uploaded by the ground terminal can be broadcasted in the specified format.

As shown in fig. 4, an information flow diagram of an L measurement and control backup mode is provided, when the communication system works in the L measurement and control backup mode, backup of an S measurement and control link is mainly completed, downloading of on-board telemetry information is achieved, a ground L station is responsible for receiving downlink information, the received remote telemetry information is transmitted to an S measurement and control center through a ground network, and analysis and evaluation of the information are uniformly completed by the measurement and control center. When the communication system works in the L measurement and control backup mode, the communication system receives whole satellite telemetry through the CAN bus and issues 4Kbps information rate according to a specified format.

As shown in fig. 5, an information flow diagram of an L broadcast mode is provided, and when the communication system works in the L broadcast mode, it can support direct broadcast of satellite original data according to a specified format after processing the satellite original data by a communication link, so as to improve real-time performance of service information. The direct broadcast rate is 4Kbps. When the communication system works in the L broadcasting mode, the communication system receives the 1Mbps data stream sent by the data transmission system through LVDS, stores the data, analyzes the storage, extracts the data, and then issues the data at the information rate of 4Kbps according to the specified format and control instruction.

The information flow in the L service push mode may refer to the L broadcast mode, but the downlink rate in the L service push mode is 32Kbps.

As shown in fig. 6, an information flow diagram of a Ka data transmission mode is provided, because a Ka link of the communication system is a phased array system, an antenna beam is an area beam and beam pointing can be flexibly intercepted in a ±60° area, therefore, the Ka link of the communication system is a passive controlled link, when the communication system works in the Ka data transmission mode, the Ka link can be used as a backup link of an X data transmission high-speed link on one hand, and the flexibility of the beam pointing of the Ka link can be recycled on the other hand, so that fixed-point pushing of specific services including service pushing for a mobile station or a central station is realized. When the communication system works in the Ka data transmission mode, the communication system receives 2Mbps or 20Mbps data streams sent by the data transmission system through LVDS, and outputs the data streams to the Ka phased array antenna for transmission through DA. The phased array antenna beam calculates the position information of satellites input by the satellite service and the position information of ground stations on the ground according to the communication system, and the phased array antenna beam is directed to the ground stations in real time.

In one embodiment, the system switches working modes through an S measurement and control link control mode or an L communication link control mode; the S measurement and control link control mode comprises that a star component analyzes a control instruction of the uplink of the measurement and control link to obtain instruction information, and the working mode of the communication system is controlled through a CAN bus according to the instruction information; the L communication link control mode comprises that the star service component analyzes a remote control telemetry mode control instruction sent by the ground L station to obtain instruction information, and the working mode of the communication system is controlled through the CAN bus according to the instruction information.

In this embodiment, when the communication system operates in the other mode, the target operation mode may be switched by the S measurement and control link control mode and the L communication link control mode. The S measurement and control link control mode needs to be a direct control mode by uploading control instructions to the measurement and control link, and when the satellite is in the environment, the L communication link control mode is a direct control mode by sending remote control and telemetry mode control instructions from the ground L station. The bus instructions are shown in Table 1:

TABLE 1 bus instruction

In one embodiment, obtaining task demand data according to the L-band uplink instruction includes: the transceiver analyzes the L frequency band uplink instruction, correspondingly generates a series of required star service related instructions, and forwards the star service related instructions to the star service assembly; the star-service related instruction comprises a data transmission solid-memory playback instruction and a data transmission solid-memory stop instruction; the data processing module of the data transmission assembly plays back the stored data of the fixed storage designated partition according to the data transmission fixed storage playback instruction and the data transmission fixed storage stopping instruction sent by the star service assembly to obtain task demand data; the system further comprises: the data transmission component sets the communication rate of the data transmission bus according to the bus command and communicates with the transceiver according to the set communication rate.

In this embodiment, the data transfer component communicates with the transceiver according to a four-wire protocol, with communication rates including 2Mbps, 10Mbps, and 20Mbps.

The characteristic parameters of the high-low speed cooperative low-orbit satellite communication system specifically comprise:

(1) Working frequency band: the uplink central frequency point of the L frequency band is 1600MHz, and the signal bandwidth is 5MHz; the L frequency band downlink center frequency point is 1500MHz, and the signal bandwidth is 5MHz; the Ka frequency band center frequency point is 22.5GHz, and the signal bandwidth is 40MHz.

(2) Modulation mode: the L frequency band uplink modulation mode is BPSK+CDMA direct sequence spread spectrum, the spread spectrum code rate is 2.046MHz, the spread spectrum code length is 1023, and the spread spectrum code type is GOLD; the L frequency band downlink modulation mode is BPSK+CDMA direct sequence spread spectrum, the spread spectrum code rate is 2.046MHz, the spread spectrum code length is 1023, and the spread spectrum code type is GOLD; the downlink modulation mode of the Ka frequency band is QPSK.

(3) Error rate

。

(4) Rate requirements: l band rate requirement: the L frequency band uplink receiving rate is 4kbps; the L frequency band downlink transmission rate is 32kbps and 4kbps; ka band rate requirement: the Ka band downstream transmission rate is 2Mbps and 10Mbps/20Mbps.

(5) Emission performance:

l frequency band

(pitch angle 0-68 azimuth angle 0-360, shape to ground);

(1) The emission power is more than or equal to 4W;

(2) antenna polarization mode: left-hand circular polarization;

(3) antenna pattern:

the gain is not less than +.>

；

(4) Frequency stability: carrier frequency accuracy is better than

Short term stability of carrier frequency is better than

；

(5) Channel characteristics: the amplitude unbalance degree of the modulation signal of the transmitting channel is better than that of the modulation signal of the transmitting channel

The phase imbalance degree of the modulation signal of the transmitting channel is better than +/-4 degrees, and the harmonic suppression degree of the modulation signal of the transmitting channel is +.>

Not less than 35dB in addition;

ka band EIRP:

(0 DEG normal),>

（±30°），/>

(±60°)；

(1) transmitting power: the output power has the capability of adjusting along with the temperature and meeting the EIRP requirement;

(2) antenna polarization mode: left-hand circular polarization;

(3) frequency stability: carrier frequency accuracy is better than

Short-term stability of carrier frequency: is superior to

；

(4) Channel characteristics: the amplitude unbalance degree of the modulation signal of the transmitting channel is better than that of the modulation signal of the transmitting channel

The phase imbalance of the modulation signal of the transmitting channel is better than +.>

The modulation signal carrier suppression degree of the transmitting channel is +.>

Except not less than 40dB.

(6) Reception characteristics (L band):

antenna polarization mode: right-hand circular polarization;

antenna pattern:

the gain is not less than +.>

；

Channel characteristics: reception sensitivity

(information Rate 4kbps, maximum Doppler reception)

Doppler change Rate->

) Receiving error rate +.>

。

(7) Dynamic range: l reception (4 kbps): 40dB.

(8) Anti-co-channel interference: better than 7dB (4 kbps rate).

(9) The capturing time is less than or equal to 4s.

(10) The capture probability is more than or equal to 0.9;

(11) On-board end-to-end processing delay (delay of L receiving L sending when information is transmitted through)

；

(12) The phase noise parameters for the L band and Ka band are shown in table 2:

TABLE 2 phase noise parameters

The protocol specifications of the high-low speed cooperative low-orbit satellite communication system comprise an L-band interface specification and a Ka-band interface specification:

the L-band interface specification prescribes technical requirements of the satellite communication system L-band data transmission link, such as working frequency, transmission rate, transmission system, link performance, radio frequency characteristics, channel characteristics and the like, and is a basic basis for proving, designing and formulating development requirements and interface control files of each constituent unit of the satellite-ground link.

(1) Transmission rate: the transmission rate defined by the specification refers to the data rate of the modem output port. The downlink rate file includes a coded modulated data stream rate 1 and a coded modulated data stream rate 2, the coded modulated data stream rate 1 being 8Kbps and the coded modulated data stream rate 2 being 64Kbps. The coded modulated data stream rate for the uplink rate stage is 8Kbps.

(2) Transmission system: as shown in fig. 7, a downlink 4Kbps processing flow diagram is provided, as shown in fig. 8, a downlink 32Kbps processing flow diagram is provided, as shown in fig. 9, an uplink processing flow diagram is provided, and an incoherent direct sequence spread spectrum (DS) transmission system is adopted, specifically, a formatting mode includes addition mode word and frame count, and a polarization mode is circular polarization (downlink left-handed and uplink right-handed); the modulation/demodulation mode is PCM-CDMA-PSK; the PCM code pattern is NRZ-L; the pseudo code pattern is a balanced GOLD code; pseudo code length of

The method comprises the steps of carrying out a first treatment on the surface of the The spread spectrum code rate is 2.046Mcps; channel coding is RS (223, 255) + convolution (2, 1, 7); the scrambling mode is PN8 scrambling code.

The channel coding is RS (223, 255) +convolution (2, 1, 7), wherein the RS coding is (255,223), the symbol length is 8, the error correction capability is 16, the dual base is the downlink interleaving depth is 4, and the uplink is not interleaved. As shown in fig. 10, there is provided a schematic diagram of an operating principle of an RS (255,223) encoder, as shown in fig. 11, an RS coding block diagram when an interleaving depth is 4, as shown in fig. 12, and an RS coding block diagram when no interleaving is provided, where specific parameter requirements include: the number of bits per R-S symbol is j=8; the error correction capability of the RS symbol in one R-S codeword is e=16; each code word contains 255 symbols; the domain generation polynomial is:

(defined over GF (2));

the code generating polynomial is

(defined on GF (28), F (α) =0), downlink four-level interleaving, uplink no interleaving, and symbol represented by dual basis.

As shown in fig. 13, a schematic diagram of the principle of convolution (2, 1, 7) is provided, the code generation vector of CONV (2, 1, 7): g1 = 1111001, g2= 1011011. As shown in fig. 14, a structural diagram of a downlink frame format is provided, where the total length of the pilot code is 1 second, and the first 750ms is all 1, and the second 250ms is 0 and 1 bit alternating. The data frame includes a frame synchronization code and a data field, the frame synchronization code: 1ACFFC1D, the frame synchronization code length is 4Byte; the data field comprises a mode word, a frame count, original data and RS check bits, and the total length of the data field is 1020Byte, wherein the mode word: the telemetry data is CC, the original data is 33, the uploading forwarding is 66, the invalid data is 99, the mode word length is 1Byte, the frame count is used for data frame count, the original data types comprise telemetry data (length to be confirmed), original data (format to be determined) and uploading forwarding data (format to be determined), if the length is more than 890Byte, the multi-frame transmission is carried out, and if the length is less than 890Byte, the subsequent data is AA.

As shown in fig. 15, a schematic structure of an uplink frame format is provided, where the total length of the pilot code is 1 second, the first 750ms is all 1, and the second 250ms is 0 and 1 bit alternate. The data frame includes a frame synchronization code and a data field, the frame synchronization code: 1ACFFC1D, the frame synchronization code length is 4Byte; the data field comprises a mode word, original data and a check bit field, and the total length of the data field is 255Byte, wherein the mode word is as follows: the star data is CC, the uploading forwarding is 66, the word length is 1Byte, the original data mainly comprises star data and uploading forwarding, the length and the format are to be confirmed, the frame transmission is carried out when the length exceeds 222Byte, and the subsequent data is AA when the length is less than 222 Byte.

The scrambling mode is PN8 scrambling, in order to generate enough bit jumps to be beneficial to the receiving end to realize bit synchronization, the transmitting end realizes scrambling through pseudo random sequence and input data modulo 2 scrambling, the scrambling is carried out by taking each transmission frame or coded transmission frame as a unit, and when scrambling is carried out on each transmission frame or coded transmission frame, the state of a shift register is set to be an initial state.

a) Pseudo-random sequence generator polynomial

The pseudo-random sequence is generated by the following polynomial:

；

b) Scrambling logic a schematic diagram of scrambling logic specified by the L-band interface specification is shown in fig. 16.

Ka band interface Specification:

(1) Interface form: under the control allocation of the satellite service, the satellite data transmission component is matched with a high-low speed cooperative low-orbit satellite communication system to complete the function verification of the communication system. A schematic diagram of the interface of the data transfer assembly with the transceiver is shown in fig. 17. The communication interface of the data transmission component output to the transceiver adopts an LVDS form, wherein the data transmission component is an output party, and the transceiver is a receiving party. The timing diagram of the interface for the data transfer component to output to the transceiver for communication is shown in fig. 18.

a. The data transmission component outputs two paths of data of gating (EN), I and Q and CLK code Zhong Silu signals, and the interface signal is LVDS level;

b. Clock: the frequency is 1/5/10MHz, the continuous clock is provided, the duty ratio is 45-55%, the clock frequency is switched through a bus instruction, and the default is 1Mhz;

c. and (3) gating: the low level corresponds to valid data, the high level corresponds to invalid data, and the EN corresponds to a completed transmission frame;

d. IQ data: data is transmitted in bytes. The high byte is before the multi-byte data is sent, the low byte is after the multi-byte data is sent, and the high byte is before and the low byte is after the multi-byte data is sent. For example, the transmission data "0x1ACF" is transmitted in the order of "0001101011001111", the order of the I-path data is "0011 1011", and the order of the Q-path is "0100 1011";

(2) Working mode: the interaction between the data transmission component and the communication system mainly comprises the following two working modes.

TABLE 3 working mode of interaction of data transmission assembly and high-low speed cooperative low orbit satellite communication system

Communication playback mode: according to task requirements, when the data transmission component is required to play back data from the solid memory to the high-low speed cooperative low-orbit satellite communication system, the communication rate (2 Mbps, 10Mbps, 20Mbps three-gear, 2Mbps default) output to the high-low speed cooperative low-orbit satellite communication system is required to be set through the bus instruction, and then the data in the FLASH is played back to the transceiver for communication through the playback instruction. The communication system data in FLASH is stored by taking 1024 bytes as a frame after LDPC coding, and the data transmission frame format illustration is shown in figure 19. The frame length is 1024 bytes, the effective area bit 886 bytes of the VCDU data, the LDPC code check code is 128 bytes, the specific situation is as follows:

(1) Synchronous word: "1ACFFC1D"

(2) Version number: "01"

(3) Spacecraft identifier SCID (8 bits total);

(4) The virtual channel identifier VCID (6 bits total) is:

"001001" means "infrared camera communication system data";

"010010" means "integrated radio communication system data";

"100100" means "compound eye camera communication system data";

"101010" means "padding frame (data field is 55H)";

(5) Virtual channel data frame count: transmission frames generated on virtual channels are numbered sequentially, with the value'

", the padding frames are also counted separately;

(6) Signaling domain:

the working mode identification:

"b7" -playback flag, 1 represents playback transmission frame, 0 represents real-time transmission;

standby identification:

"b 6-b 5" -an explicit flag, "00" represents an explicit state (default), and "11" represents a dense state;

"b 4-b 0" -fill "00000".

(7) VCDU data unit: the effective data area is real-time data or playback data of the communication system, and 55H is filled in the frame;

(8) VCDU check field: the check code is 128 bytes, and the 128 bytes of check codes coded by LDPC codes (8160 and 7136) are adopted.

As shown in fig. 20, a schematic diagram of a Ka data information flow is provided, after the data in the FLASH is read, scrambling, serial-parallel conversion and differential coding processing are completed according to the data information processing flow, and finally LVDS data is output to a transceiver for communication according to a contracted four-wire system protocol. After QPSK modulation is carried out on the output data, the communication system transmits the data through a phased array antenna. In addition, the bit sequence numbers of the transmission data are agreed, and the high bits in the bytes are transmitted first, and the high bytes are transmitted first under the condition of multiple bytes. Taking the sync header 1ACFFC1D as an example, the output bit stream (32 bits total) is 00011010110011111111110000011101.

The specific playback process comprises the following steps: and sending a bus 'data transfer solid storage 1/2/3/4 zone playback' instruction, wherein the data processing FPGA plays back the designated partition from the beginning sequentially until receiving the 'data transfer solid storage stop' instruction, stopping playback, recording the current playback address, playing back from the address when the zone is required to be played back again next time, continuing playing back until playing back to the end address when not receiving the 'data transfer solid storage stop' instruction, and then circularly playing back from the beginning to the end address.

The specific process of scrambling comprises the following steps: scrambling the downloaded serial data stream according to CCSDS standard, wherein the scrambling polynomial is

As shown in fig. 21, the scrambling logic diagram defined by the Ka band interface specification, in which the initial phase of the scrambling polynomial is all '1' (CCSDS), is performed in units of each frame structure unit, and only the data frame format is scrambled and the synchronization header is not scrambled. Starting from the first bit of the code block or transmission frame, it repeats every 255 bits later. Within each sync mark period, the sequence generator is reinitialized to the "all 1" state. The first 40 bits of this sequence are:

；

the specific process of serial-parallel conversion and differential coding comprises the following steps: serial-parallel conversion divides the received serial data into two odd-even paths, and delays one path by one bit to align the front and back code elements. The differential encoding logic relationship is as follows:

when the symbols of the previous pair of outputs are identical, i.e

The method comprises the following steps:

；

；

when the symbols of the previous pair of outputs are different, i.e

The method comprises the following steps:

；

；

wherein, the liquid crystal display device comprises a liquid crystal display device,

，/>

is the current output of the encoder,/>

，/>

Is the current input of the encoder, < >>

，/>

Is the output of the encoder at the previous time.

Auxiliary recording mode: when an auxiliary record instruction of a star computer is received, the data processing FPGA of the data transmission component stores the data of the high-low speed cooperative low-orbit satellite communication system, and simultaneously, the LVTLL level signals of the high-low speed cooperative low-orbit satellite communication system are directly shunted to the interface of data transmission and communication without processing.

The interface between the data transmission component and the transceiver is in the form of LVDS interface. The data transmission interface device adopts SN65LVD32D (receiving), and the communication adopts SN65LVD31D (receiving). A schematic diagram of a low-orbit satellite communication system LVDS interface circuit for receiving high-low speed cooperation is shown in fig. 22.

a. The communication system outputs gating (SYN), DATA (DATA) and CLK code Zhong Sanlu signals, the interface signal is LVDS level, and the timing diagram provided by the communication system to the DATA transmission is shown in fig. 21;

b. clock: the frequency is 5MHz, which is a continuous clock, and the duty ratio is 45-55%;

c. and (3) gating: low level corresponds to valid data, and high level corresponds to invalid data;

d. data: 1bit, code rate 5Mbps, data is transmitted in bytes. The high byte is before the multi-byte data is sent, the low byte is after the multi-byte data is sent, and the high byte is before and the low byte is after the multi-byte data is sent. For example, the transmission data "0x1ACF" is transmitted in the order of "0001101011001111";

e. clock code time delay: the gating and data transitions align with the clock rising edge + -2 ns.

In the forwarding process, the data transmission does not process the data of the low-orbit satellite communication system with the high-speed and low-speed cooperation, and directly forwards the original data to the transceiver. Since the transceiver is three-wire system, and four-wire system is between the data transmission and the transceiver. Thus, agree that: the gate (SYN), DATA (DATA) and CLK code Zhong Sanlu signals input by the transceiver are respectively output to the gate (EN), I DATA and CLK code Zhong Sanlu signals of the transceiver interface by the corresponding output components, and the Q-way DATA is set to "1".

In one embodiment, as shown in fig. 23, there is provided a low-orbit satellite communication method for high-low speed cooperation, comprising the steps of:

s1, receiving an L-band uplink instruction of a ground terminal.

S2, obtaining L-band downlink low-speed data or Ka-band downlink high-speed data according to the L-band uplink instruction, sending the L-band downlink low-speed data to an L-transmitting antenna, and sending the Ka-band downlink high-speed data to a Ka phased array antenna so as to realize point-to-point communication.

S3, obtaining telemetry data and remote control data, obtaining navigation data according to the telemetry data and the remote control data, and broadcasting the navigation data to the ground terminals in the service area through the L transmitting antennas.

It should be understood that, although the steps in the flowchart of fig. 22 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 22 may include a plurality of sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, or the order in which the sub-steps or stages are performed is not necessarily sequential, but may be performed in turn or alternately with at least some of the other steps or sub-steps of other steps.

Specific limitations regarding the high-low speed cooperative low-orbit satellite communication method can be found in the above limitation of the high-low speed cooperative low-orbit satellite communication system, and will not be described herein.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims

1. A high-low speed cooperative low orbit satellite communication system, the system comprising:

the transceiver is used for receiving the L frequency band uplink instruction, obtaining task demand data according to the L frequency band uplink instruction, sending the task demand data to a corresponding antenna, receiving telemetry and remote control data sent by a star service component, and sending the telemetry and remote control data to an L transmitting antenna; the task demand data comprise L-band downlink low-speed data or Ka-band downlink high-speed data;

the protocol specification of the system includes:

an L-band interface specification and a Ka-band interface specification;

the L frequency band interface specification specifies that data is transmitted in an L frequency band by adopting an incoherent direct sequence spread spectrum transmission system, a downlink frame format comprises a frame synchronization code and a data field, and an uplink frame format comprises the frame synchronization code and the data field; the data field of the downlink frame comprises a mode word, a frame count, original data and RS check bits; the original data of the downlink frame comprises telemetry data, original data and uplink forwarding data; the data field of the uplink frame comprises a mode word, original data and a check bit field, and the original data of the uplink frame comprises star service data and uplink forwarding;

The Ka frequency band interface specification specifies that a data transmission frame format of the Ka frequency band comprises a synchronization word, a version number, a spacecraft identifier, a virtual channel data frame count, a signaling field, a VCDU data unit and a VCDU check field.

2. The system of claim 1, wherein the transceiver is further configured to receive beam pointing adjustment information sent by the star assembly to adjust beam pointing; the beam pointing adjustment information includes satellite orbit information, satellite position information, and satellite attitude information.

3. The system of claim 1, wherein the ground L station comprises an L center station, an L mobile station, and an L portable terminal; the ground K stations include a K central station and a K mobile station.

4. The system of claim 1, wherein the modes of operation of the system include an L-band mode of operation, a Ka-band mode of operation, and a combined mode of operation;

the working modes of the L wave band comprise an L processing forwarding mode, an L measurement and control backup mode, an L broadcasting mode and an L service pushing mode; the working mode of the L wave band works in a time-sharing way;

the working mode of the Ka wave band comprises a Ka data transmission mode;

the combined working mode comprises four modes obtained by respectively combining the Ka data transmission mode with four working modes of an L wave band; and in the combined working mode, the Ka data transmission mode and the L-band working mode work simultaneously.

5. The system of claim 4, wherein the system switches modes of operation by either an S measurement and control link control mode or an L communication link control mode;

the S measurement and control link control mode comprises that a star component analyzes a control instruction of the uplink of the measurement and control link to obtain instruction information, and the working mode of the communication system is controlled through a CAN bus according to the instruction information;

the L communication link control mode comprises that the star service component analyzes a remote control telemetry mode control instruction sent by the ground L station to obtain instruction information, and the working mode of the communication system is controlled according to the instruction information through the CAN bus.

6. The system of claim 1, wherein the obtaining task demand data according to the L-band uplink instruction includes:

the transceiver analyzes the L-band uplink instruction, correspondingly generates a series of required star-service related instructions, and forwards the star-service related instructions to a star-service assembly; the star-service related instruction comprises a data transmission solid-memory playback instruction and a data transmission solid-memory stop instruction;

and the data processing module of the data transmission component plays back the stored data of the fixed storage designated partition according to the data transmission fixed storage playback instruction and the data transmission fixed storage stopping instruction sent by the star service component to obtain the task demand data.

7. The system of claim 1, wherein the system further comprises:

the data transmission assembly sets the communication rate of the data transmission bus according to the bus instruction, and communicates with the transceiver according to the set communication rate; the data transmission component communicates with the transceiver according to a four-wire system protocol; the communication rates include 2Mbps, 10Mbps, and 20Mbps.

8. The system of claim 1, wherein the transceiver is coupled to the star assembly via a star bus; the star service bus comprises a CAN bus and I ² A C bus; the CAN bus and I ² The C buses are mutually backup;

the transceiver is connected with the data transmission assembly through a data transmission bus; the data transfer bus includes an LVDS bus.

9. A method of high and low speed cooperative low orbit satellite communication, the method comprising:

receiving an L-band uplink instruction of a ground terminal;

acquiring telemetry data and remote control data, acquiring navigation data according to the telemetry data and the remote control data, and broadcasting the navigation data to ground terminals in a service area through an L transmitting antenna;

The method further comprises the steps of:

defining an L frequency band interface specification and a Ka frequency band interface specification;