A high-speed data transmission system for inertial orientation small satellites

Abstract

The present invention provides a high-speed data transmission system for inertial directional small satellites, including: a first multiplexing modulator, a second multiplexing modulator, a microwave network, a first phased array unit and a second phased array unit. The two multiplexing modulators are respectively used to receive and store various load data, and multiple load data are sequentially multiplexed, framed, channel-coded and carrier-modulated during inbound data transmission, and the modulated radio frequency signal is power pre-amplified and filtered, as well as the beam pointing angle is calculated. The two phased array units are respectively used to power-divide the received radio frequency signal into multiple channels, and form a directional beam after channel shifting and signal amplification according to the beam pointing angle, thereby completing the pointing tracking of the antenna beam to the ground data transmission station. The present invention adopts a variety of backup, redundancy and cross-connection design methods, which can meet the long life and high reliability requirements of the satellite for the data transmission system while reducing the system cost as much as possible.

Description

Technical Field

[0001] The invention relates to a satellite data transmission system. Background Art

[0002] The main functions of the satellite data transmission system are: receiving various types of payload data, as well as detailed engineering telemetry data from the satellite computer and the original data of the GNSS receiver, and completing the multiplexing and storage of the above multiple data; forming data transmission frames when the satellite passes through the ground data transmission station, completing channel coding, signal modulation, and power amplification, and then transmitting them to the ground data transmission station through the transmitting antenna.

[0003] Many space science satellites, especially astronomical observation satellites, generally set the whole satellite attitude pointing to inertial orientation mode to meet the needs of scientific payload observation, and require the satellite attitude to have high stability. In order to reduce costs, all kinds of satellites tend to adopt small satellite platforms. How to improve the reliability and life of the high-speed data transmission system of inertial orientation small satellites has become an urgent problem to be solved in this field.

[0004] There are generally three types of solutions for existing high-speed data transmission: one is a small power amplifier combined with a high-gain turntable antenna solution, the second is a high-power traveling wave tube amplifier combined with a wide-beam low-gain antenna solution, and the third is a phased array solution.

[0005] (1) The turntable in the solution of small power amplifier combined with high-gain turntable antenna will cause disturbance to the satellite attitude and is not suitable for satellites with high requirements for attitude stability. In addition, the design, development and test verification of long-life mechanical rotation mechanisms are currently quite difficult, so the turntable solution is not suitable for satellites with long life cycles.

[0006] (2) The high-power traveling wave tube amplifier combined with a wide-beam low-gain antenna solution requires a high-power amplifier and a waveguide, so it is heavy and consumes a lot of power. In addition, the layout and assembly of the waveguide have high requirements. Therefore, the traveling wave tube solution is not suitable for small satellites with limited weight and power consumption.

[0007] (3) The phased array solution uses electronic scanning to aim the beam at the ground data transmission station, which will not cause disturbance to the satellite's attitude. In addition, its weight and power consumption are less than the traveling wave tube amplifier solution. Although the current phased array single-machine technology is relatively complex and relatively mature, with the development of engineering technology, phased array RF single-machine has become increasingly mature. Recently, many satellites that have been launched and are under development have adopted phased array solutions.

[0008] In traditional phased array solutions, there is no redundant backup inside the phased array unit. To improve system reliability, a whole-machine backup mode is adopted, that is, each face is equipped with two completely independent phased array units. For example, a certain satellite model has a total of 4 phased array units on two faces, which is very expensive and not suitable for low-cost small satellite projects. Although some solutions do not adopt the whole-machine backup solution to reduce costs, there are weak points in the phased array unit, which does not meet the requirements of high reliability and long life. Summary of the invention

[0009] In order to overcome the above technical defects, the present invention provides a high-speed data transmission system for inertial orientation small satellite, comprising: a first multiplexing modulator, a second multiplexing modulator, a microwave network, a first phased array stand-alone machine and a second phased array stand-alone machine;

[0010] The first multiplexing modulator and the second multiplexing modulator are respectively used to receive and store the load data of each channel, perform multiplexing framing, channel coding and carrier modulation on the multiple load data in sequence during inbound data transmission, perform power pre-amplification and filtering on the modulated RF signal, and calculate the beam pointing angle and send it to the first phased array unit and the second phased array unit;

[0011] The microwave network provides a cross-connection channel between two multiplex modulators and two phased array stand-alone machines;

[0012] The first phased array unit and the second phased array unit are respectively used to divide the received RF signal into multiple channels, and form a directional beam after channel shifting and signal amplification according to the beam pointing angle, so as to complete the pointing tracking of the antenna beam to the ground data transmission station. The first phased array unit and the second phased array unit are symmetrically configured back to back. In order to cope with the uncertainty of satellite attitude pointing, two phased array units are configured and installed in opposite directions. For example, the opposite directions can be named +Z direction and -Z direction.

[0013] Furthermore, the first multiplexing modulator and the second multiplexing modulator are always powered on and work in a cold backup working mode, that is, at the same time, only one of the two multiplexing modulators is in working state. When one multiplexing modulator fails, it is immediately switched to the other one for work.

[0014] Microwave networks are passive devices that use low-power radio frequency signals. They have extremely high reliability and allow the existence of single points.

[0015] Furthermore, the first phased array unit and the second phased array unit are powered on and operated only during the data transmission transit period. The first phased array unit or the second phased array unit is selected to be powered on and operated according to the satellite attitude pointing. Only one phased array unit is powered on and operated at the same time.

[0016] Furthermore, when the data transmission enters the country, if the first phased array unit is facing the ground station, the first phased array unit is turned on and works; if the second phased array unit is facing the ground station, the second phased array unit is turned on and works; during the data transmission transit, if the posture is reversed, the two phased array units relay to work.

[0017] Furthermore, the first phased array unit and the second phased array unit both include a power supply module, a beam control module, a power division network, a multi-channel phase-shift amplification channel and an array antenna.

[0018] The power division network and array antenna are passive devices with extremely high reliability and single point is allowed to exist.

[0019] Furthermore, the power module and the wave control module are both set to A / B cold standby working mode, and when module A fails, it switches to module B to work.

[0020] Furthermore, the multi-channel phase-shift amplification channel modules are designed independently, that is, there is no common amplification circuit. The common amplification circuit is placed in the multiplexing modulator (the multiplexing modulator is in a dual-machine cold standby form and will not form a single point), that is, the signal pre-amplification module, and some redundant channels are reserved on the basis of the basic channel. The reserved redundant channels are not powered on by default. When the basic channel fails, it can be powered on by instructions. Assuming that the number of basic channels is M, the number of reserved redundant channels is N, and K channels fail during on-orbit operation. Then when K≤N, the system indicators will not decrease. Even if K is slightly greater than N, it will only reduce the margin of the satellite-to-ground communication link, and will not cause the communication link to be unavailable.

[0021] Furthermore, the first multiplexing modulator and the second multiplexing modulator each include a receiving storage module, a multiplexing framing module, a channel coding module, a signal modulation module, a signal pre-amplification module, a signal filtering module and a beam angle calculation module;

[0022] The receiving and storing module is used to receive and store the load data of each channel;

[0023] The multiplexing framing module is used to multiplex and frame multiple load data during inbound data transmission;

[0024] The channel coding module is used to perform channel coding on the multiplexed framed data;

[0025] The signal modulation module is used to perform carrier modulation on the channel-coded data;

[0026] The signal pre-amplification module is used to pre-amplify the power of the modulated RF signal;

[0027] The signal filtering module is used to filter the amplified signal;

[0028] The beam angle calculation module is used to calculate the beam pointing angle and provide the beam pointing angle to the first phased array unit and the second phased array unit.

[0029] Compared with the prior art, the above technical solution has the following beneficial effects:

[0030] The present invention proposes a small satellite suitable for inertial orientation and with high requirements for attitude stability. The scheme achieves high ground transmission EIRP and good satellite attitude stability through phased array electronic scanning, and has a high data transmission rate. At the same time, a variety of backup, redundancy and cross-connection design methods are adopted, which can meet the long life and high reliability requirements of the satellite data transmission system under the premise of reducing the system cost as much as possible.

[0031] To improve system reliability, single points should be eliminated as much as possible, and modules with weak reliability must have backups. In order to remove single points and reduce costs, the RF signal pre-amplification module shared by multiple phase-shifted amplification channels in a traditional phased array unit is placed in the multiplexing modulator (the multiplexing modulator is in a dual-machine cold standby form and will not form a single point). At the same time, the beam angle calculation function is also placed in the processor of the multiplexing modulator, thereby simplifying the processor design of the phased array unit beam control module, and only using a small-scale high-reliability FPGA (field programmable gate array) to further improve system reliability. Compared with the traditional whole-machine backup solution, this backup solution can greatly save volume, weight and financial costs, and is suitable for small satellite applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the composition and data transmission principle of the high-speed data transmission system used in inertial orientation small satellites;

[0033] Figure 2 for Figure 1 Detailed diagram of the digital transmission system composition and data transmission principle.

[0034] Figure 3 For Figure 2 The corresponding system reliability block diagram is: Figure 3 The "phase-shifted amplifier channel (redundancy)" is a dotted box to distinguish it from the traditional solution of conventional whole-machine backup. As can be seen from the figure, there is no weak single point in the entire digital transmission system, so it has extremely high reliability. DETAILED DESCRIPTION

[0035] The advantages of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention. The term "including" and its variations used in this article represent open inclusions, that is, "including but not limited to". It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other, and can refer to different or identical objects, and cannot be understood as indicating or implying relative importance.

[0036] The XX satellite of this embodiment operates in a near-earth circular orbit with a nominal altitude of 550 km, and its attitude pointing is inertial pointing. Figure 1 As shown, the data transmission system of the XX satellite includes a first multiplexing modulator (for example, in this embodiment, it is named as multiplexing modulator A), a second multiplexing modulator (for example, in this embodiment, it is named as multiplexing modulator B), a microwave network, a first phased array unit (for example, in this embodiment, it is named as +Z phased array unit) and a first phased array unit (for example, in this embodiment, it is named as -Z phased array unit).

[0037] like Figure 2 As shown, the multiplexing modulator A and the multiplexing modulator B both include a receiving storage module, a multiplexing framing module, a channel coding module, a signal modulation module, a signal pre-amplification module, a signal filtering module and a beam angle calculation module. The receiving storage module is used to receive and store the load data of each channel. The multiplexing framing module is used to perform multiplexing framing on the multiple load data during inbound data transmission. The channel coding module is used to perform channel coding on the data after multiplexing framing. The signal modulation module is used to perform carrier modulation on the data after channel coding. The signal pre-amplification module is used to perform power pre-amplification on the modulated RF signal. The signal filtering module is used to filter the amplified signal. The beam angle calculation module is used to solve the beam pointing angle and provide the beam pointing angle to the +Z phased array stand-alone and the -Z phased array stand-alone. The multiplexing modulator A and the multiplexing modulator B are used to receive and store the load data of each channel respectively, and perform multiplexing framing, channel coding and carrier modulation on the multiple load data in sequence during inbound data transmission, perform power pre-amplification and filtering on the modulated RF signal, and calculate the beam pointing angle and provide the beam pointing angle to the +Z phased array unit and the -Z phased array unit. The multiplexing modulator A and the multiplexing modulator B are always powered on and in cold backup working mode, that is, at the same time, only one of the two multiplexing modulators is in working state. When one multiplexing modulator fails, it will immediately switch to the other one to work.

[0038] like Figure 2As shown, both the +Z phased array stand-alone and the -Z phased array stand-alone include a power module, a beam control module, a power division network, a multi-channel phase-shift amplification channel and an array antenna. The power module and the beam control module are both set to the A / B cold standby working mode, and can switch to module B when module A fails. The power division network and the array antenna are passive devices with extremely high reliability, and single points are allowed to exist. The multi-channel phase-shift amplification channel module is designed independently, that is, there is no common amplification circuit, and some redundant channels are reserved on the basis of the basic channel. The +Z plane phased array stand-alone and the -Z plane phased array stand-alone divide the received RF signal into multiple channels, and form a directional beam after channel shifting and signal amplification according to the beam pointing angle, thereby completing the pointing tracking of the antenna beam to the ground data transmission station. In order to cope with the uncertainty of satellite attitude pointing, two phased array stand-als are configured back to back symmetrically, assuming that they are installed in the +Z direction and -Z direction respectively. +Z phased array stand-alone and -Z phased array stand-alone are powered on and work only during the digital transmission transit. The +Z and -Z phased array stand-alone are selected according to the satellite attitude and direction, and only one is powered on and work at the same time. When the digital transmission enters, if the first phased array stand-alone is facing the ground station, the first phased array stand-alone is powered on and work; if the second phased array stand-alone is facing the ground station, the second phased array stand-alone is powered on and work; during the digital transmission transit, if the attitude is flipped, the two phased array stand-alones will work in relay.

[0039] The microwave network provides a cross-connection channel between two multiplex modulators and two phased array stand-alone machines. The microwave network is a passive device that passes low-power radio frequency signals, has extremely high reliability, and allows the existence of a single point.

[0040] like Figure 3 As shown, the data transmission process of the high-speed data transmission system applied to the inertial orientation small satellite is as follows:

[0041] (1) The multiplexing modulator receives and stores the data of each load channel. When transmitting inbound data, it performs multiplexing framing, channel coding and carrier modulation on the multiple load channels in sequence, and performs power pre-amplification and filtering on the modulated RF signal. In addition, it also has the function of beam pointing solution, providing the beam pointing angle to the phased array unit. The multiplexing modulator is always powered on and working. Machines A and B are in cold backup working mode, that is, only one of the two multiplexing modulators is in working state. When one multiplexing modulator fails, it immediately switches to the other one to work.

[0042] (2) The microwave network provides a cross-connection channel between the two multiplexed modulators and the two phased array units. The microwave network is a passive device that transmits low-power radio frequency signals, has extremely high reliability, and allows the existence of a single point.

[0043] (3) To cope with the uncertainty of satellite attitude pointing, two phased array units are configured, installed in the +Z direction and -Z direction respectively. The phased array unit divides the received RF signal into multiple channels, shifts the channel direction and amplifies the signal according to the beam pointing angle to form a directional beam, and completes the pointing tracking of the antenna beam to the ground data transmission station. Specifically, the multiplexing modulator outputs the RF signal. The microwave network has a total of 4 interfaces, the two on the left are input interfaces, and the two on the right are output interfaces. The RF signal comes in from any input interface and can be output from the two output interfaces at the same time (similar to a splitter). The output signal of the microwave network enters the power division network of the phased array unit, and the signal is divided into multiple channels and enters the transmitting phase shift channel. According to the beam angle provided by the multiplexing modulator, the channel phase is shifted and the signal is amplified to form a directional beam and transmitted to the ground station.

[0044] The phased array unit is powered on and works only during the digital transmission transit. The phased array units in the +Z and -Z directions are selected according to the satellite attitude pointing, and only one unit is powered on and works at the same time. When the digital transmission enters, if the first phased array unit is facing the ground station, the first phased array unit is powered on and works; if the second phased array unit is facing the ground station, the second phased array unit is powered on and works. During the digital transmission transit, if the attitude is reversed, the two phased array units will work in relay.

[0045] The power module and wave control module of the phased array stand-alone are set to A / B cold standby working mode. When module A fails, it can switch to module B to work.

[0046] The multi-channel phase-shifted amplifier channel modules of the phased array stand-alone are designed independently, that is, there is no common amplifier circuit, and some redundant channels are reserved on the basis of the basic channels. The reserved redundant channels are not powered on by default, and they can be powered on by instructions when the basic channels fail. Assuming that the number of basic channels is M, the number of reserved redundant channels is N, and K channels fail during on-orbit operation. Then when K≤N, the system indicators will not decrease. Even if K is slightly greater than N, it will only reduce the margin of the satellite-to-ground communication link, and will not cause the communication link to be unavailable.

[0047] For example, by allocating the following indicators to each single machine, a 450Mbps high-speed ground data transmission function can be achieved.

[0048] The main technical indicators of the multiplex modulator are as follows:

[0049] (1) Storage capacity: ≥2Tb;

[0050] (2) Operating frequency band: X-band, 8025MHz~8400MHz;

[0051] (3) Channel code rate: 450Mbps;

[0052] (4) Carrier modulation method: OQPSK;

[0053] (5) RF signal output power: 26±1.5dBm

[0054] The main technical indicators of microwave networks and radio frequency cables are as follows:

[0055] (1) Operating frequency band: X-band, 8025MHz~8400MHz;

[0056] (2) Insertion loss: 4±0.5dBm

[0057] The main technical indicators of the phased array stand-alone are as follows:

[0058] (1) Operating frequency band: X-band, 8025MHz~8400MHz;

[0059] (2) RF signal input power: 22±2dBm

[0060] (3) Setting the number of array elements (phase-shift amplifier channels): 32 basic channels and 4 reserved redundant channels;

[0061] (4) Transmitter EIRP: ≥18dBW

[0062] The reserved redundant channel is not powered on by default. When the basic channel fails, it can be powered on by command. When the number of phase-shift amplifier channel failures is ≤4, the communication link margin will not decrease; when the number of phase-shift amplifier channel failures is 6, the communication link margin will decrease by 0.5dB; when the number of phase-shift amplifier channel failures is 8, the communication link margin will decrease by 1dB; the link margin reserved in general system design is ≥3dB, so even if the number of phase-shift amplifier channel failures is 8, the link margin is still ≥2dB, and normal communication is still possible.

[0063] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A high-speed data transmission system for inertial orientation small satellite, characterized in that: include: A first multiplexing modulator, a second multiplexing modulator, a microwave network, a first phased array stand-alone machine, and a second phased array stand-alone machine; The first multiplexing modulator and the second multiplexing modulator are used to receive and store the load data of each channel, perform multiplexing framing, channel coding and carrier modulation on the multiple load data in sequence during inbound data transmission, perform power pre-amplification and filtering on the modulated RF signal, and calculate the beam pointing angle and send it to the first phased array unit and the second phased array unit; The microwave network provides a cross-connection channel between two multiplex modulators and two phased array stand-alone machines; The first phased array unit and the second phased array unit are respectively used to divide the received radio frequency signal into multiple channels, and form a directional beam after channel shifting and signal amplification according to the beam pointing angle, so as to complete the pointing tracking of the antenna beam to the ground data transmission station. The first phased array unit and the second phased array unit are symmetrically arranged back to back. The first multiplexing modulator and the second multiplexing modulator are always powered on and work in a cold backup working mode, that is, at the same time, only one of the two multiplexing modulators is in working state; The first phased array stand-alone machine and the second phased array stand-alone machine are powered on and work only during the data transmission transit period. The first phased array stand-alone machine or the second phased array stand-alone machine is powered on and work according to the satellite attitude pointing direction. Only one phased array stand-alone machine is powered on and work at the same time. When the data transmission enters the country, if the first phased array unit faces the ground station, the first phased array unit will start working; if the second phased array unit faces the ground station, the second phased array unit will start working; during the data transmission transit, if the attitude is reversed, the two phased array units will work in relay; The first phased array stand-alone machine and the second phased array stand-alone machine both include a power module, a wave control module, a power division network, a multi-channel phase-shift amplification channel and an array antenna; The power module and wave control module in the phased array stand-alone machine are set to A / B cold standby working mode. When module A fails, it switches to module B to work; The multi-channel phase-shift amplification channel modules in the phased array stand-alone are designed independently, that is, there is no common amplification circuit. The common amplification circuit is placed in the multiplexing modulator, that is, the signal pre-amplification module, and some redundant channels are reserved on the basis of the basic channels. The reserved redundant channels are not powered on by default, and can be powered on by instructions when needed.

2. The high-speed data transmission system for inertial orientation small satellite according to claim 1, characterized in that: The first multiplexing modulator and the second multiplexing modulator each include a receiving storage module, a multiplexing framing module, a channel coding module, a signal modulation module, a signal pre-amplification module, a signal filtering module and a beam angle calculation module; The receiving and storing module is used to receive and store the load data of each channel; The multiplexing framing module is used to multiplex and frame multiple load data during inbound data transmission; The channel coding module is used to perform channel coding on the multiplexed framed data; The signal modulation module is used to perform carrier modulation on the channel-coded data; The signal pre-amplification module is used to pre-amplify the power of the modulated RF signal; The signal filtering module is used to filter the amplified signal; The beam angle calculation module is used to calculate the beam pointing angle and provide the beam pointing angle to the first phased array unit and the second phased array unit.

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