Electromagnetic compatibility design method for low-orbit satellite system

Abstract

The invention discloses an electromagnetic compatibility design method for a low-orbit satellite system, and aims to solve the problems that the traditional design focuses on a single machine, measures are isolated, and complex electromagnetic interference of the low-orbit satellite system cannot be handled. The method comprises the following steps: S1, analyzing a system-level electromagnetic environment and requirements, determining parameters, and identifying an interference source and a coupling path; s2, providing a layered and graded electromagnetic compatibility framework including platform and load isolation, power supply interference suppression, satellite-borne cable network optimization and grounding system construction; s3, performing frequency resource and signal integrity management, planning a frequency spectrum, and optimizing a clock and a digital circuit; s4, providing a software anti-interference and fault-tolerant mechanism, and realizing data verification, instruction voting and state monitoring; s5, performing on-orbit electromagnetic compatibility prediction; and S6, carrying out ground test verification. According to the method, a full-link design system is formed, interference risks are avoided in advance, and the operation stability and data reliability of the satellite in a complex electromagnetic environment are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spacecraft design and electromagnetic compatibility, and particularly relates to a low-orbit satellite system electromagnetic compatibility design method. BACKGROUND

[0002] Low Earth Orbit (LEO) satellite systems are usually composed of a constellation of multiple satellites and are widely used in communication, remote sensing, scientific exploration and other fields. They are the core infrastructure for realizing multi-scene services in modern aerospace technology. With the continuous complication of satellite functions, the continuous improvement of integration, the significant increase in the number of electronic devices carried on the satellite, the gradual increase in device power level, and the further widening of the working frequency range, the electromagnetic interference (EMI) problem inside and outside the system has become increasingly prominent and has become one of the key challenges affecting the stable operation of the satellite.

[0003] In the prior art, electromagnetic compatibility (EMC) design is mostly focused on the single-device level, and only the electromagnetic characteristics of a single device are optimized, or simple shielding, filtering and other isolated measures are used to deal with local interference problems, and there is a lack of overall design consideration from the top-level architecture of the satellite system to the single device, from hardware design to software optimization, and from on-orbit operation to ground testing and verification. This fragmented design mode cannot solve the electromagnetic interference problem from a holistic perspective, leading to problems such as performance degradation, data transmission anomalies, and even mission interruption or failure in on-orbit satellites, which greatly restricts the reliability and service capability of low-orbit satellite systems.

[0004] Therefore, there is an urgent need for a systematic low-orbit satellite system electromagnetic compatibility design method to suppress electromagnetic interference from the root cause through full-dimensional and full-process design optimization, ensuring that the low-orbit satellite system can operate stably and reliably in a complex electromagnetic environment. SUMMARY

[0005] The purpose of the present application is to provide a low-orbit satellite system electromagnetic compatibility design method that achieves overall electromagnetic compatibility of the satellite system from single devices to systems and from on-orbit to ground through hierarchical, graded, and full-linkage collaborative design.

[0006] The present application provides a low-orbit satellite system electromagnetic compatibility design method, comprising: S1, providing a system-level electromagnetic environment and performing demand analysis; S2, providing a hierarchical and graded electromagnetic compatibility architecture; S3, performing frequency resource and signal integrity management; S4, providing software anti-interference and fault-tolerant mechanism; S5, performing electromagnetic compatibility prediction in orbit; and S6, performing ground test verification.

[0007] In an embodiment of the present application, step S1 comprises: determining mission tasks of the satellite system, determining a system operating frequency range, an upper limit of power spectral density and a sensitivity threshold; checking electronic equipment in the system, locating interference sources and sensitive equipment; identifying paths through which interference sources transmit interference to sensitive equipment, and forming an interference link list; and based on the above analysis, formulating system-level electromagnetic compatibility index requirements.

[0008] In an embodiment of the present application, step S2 comprises: centralizing electromagnetic radiation equipment on one side of the satellite and arranging the load on the other side; and setting a metal shielding cabin or shielding body between the two.

[0009] In an embodiment of the present application, step S2 further comprises: using a distributed independent power bus to separately configure a power supply circuit for the load; and installing transient suppression devices and multi-stage filter networks at the power input end to simultaneously suppress common-mode interference and differential-mode interference.

[0010] In an embodiment of the present application, step S2 further comprises: using a double-layer shielding cable for sensitive signals, wherein the shielding layer is 360-degree terminated to ensure shielding integrity; separately arranging power lines and signal lines, separately arranging cables for different frequencies, and controlling parallel wire length to be within a minimum range; and using a twisted pair structure or a coaxial structure for part of the signal lines to reduce differential-mode interference.

[0011] In an embodiment of the present application, step S2 further comprises: providing a hybrid grounding system combining single-point grounding and multi-point grounding on the satellite; and dividing power circuit grounding, signal reference grounding and shielding layer grounding, and independently connecting them to the main ground network to avoid ground loop interference.

[0012] In an embodiment of the present application, step S3 comprises: unified planning and assigning frequencies, bandwidths and transmission times of all transmitting equipment on the satellite; using a low-jitter clock source to perform package ground processing on clock signals, and impedance matching and termination design on high-speed digital signals. Deploying multi-capacitance decoupling capacitors near the power supply pins of the digital chip; and Controlling the signal line of the reset signal and the interrupt signal by adopting dual backup and watchdog monitoring.

[0013] In an embodiment of the present application, step S4 comprises: In the transmission and storage of star management data and payload data, cyclic redundancy check or forward error correction coding is embedded; A multiple sending or encoding check mechanism is adopted for control instructions, and a multiple voting mechanism is adopted to execute instructions; and The software monitors the electromagnetic environment parameters and working state of the key equipment in real time, and when an abnormality is detected, a preset reset, switching backup or safety mode process is started.

[0014] In an embodiment of the present application, step S6 comprises: The electromagnetic emission and sensitivity of a single device are tested to ensure that the single machine itself meets the electromagnetic compatibility requirements; The compatibility between devices in a subsystem is tested to avoid interference within the subsystem; The electromagnetic compatibility of all devices of the satellite when working cooperatively is tested to simulate the on-orbit working scenario; The interference intensity of the device transmitted outward through the power line and the signal line is detected; External interference is simulated to be injected into the device through the cable to verify the anti-interference ability of the device; The interference intensity of the device radiated outward through space is detected; and The space radiation interference is simulated to irradiate the device to verify the normal working ability of the device.

[0015] In an embodiment of the present application, it further comprises: The ground test results are substituted into the simulation model to correct the simulation parameters and improve the prediction accuracy; and According to the results of simulation and test combination, the design scheme is optimized to reduce the on-orbit interference risk.

[0016] The present application has the following beneficial effects: (1) From the top layer of the system to the single machine, multiple dimensions such as architecture, power supply, cable, grounding, frequency and software are covered, forming a complete electromagnetic compatibility design system; (2) Through early analysis, simulation prediction and hierarchical design, electromagnetic interference is actively suppressed in the design stage, and the on-orbit risk is reduced.

[0017] (3) The hardware level realizes the physical isolation of the platform and the load, the power supply and the interference suppression of the cable, and the software level supplements the hardware anti-interference ability through data checking, instruction voting and other fault-tolerant measures; meanwhile, the on-orbit electromagnetic simulation prediction result is combined with the ground full-level test result to dynamically optimize the design scheme, so that the anti-interference synergistic effect is formed in each link, and the overall electromagnetic compatibility performance is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A flow chart of a low-orbit satellite system electromagnetic compatibility design method in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] In the following description, the present application is described with reference to various embodiments. Those skilled in the art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other replacement and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations have not been shown or described in detail in order to avoid obscuring aspects of the application. Likewise, the specific numerals employed in the figures do not limit the present application.

[0020] In the present application, each embodiment is only intended to illustrate the scheme of the present application, and should not be understood as limiting.

[0021] In this specification, the reference to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

[0022] In addition, the numbering of the steps of each method of the present application does not limit the execution order of the method steps. Unless specifically indicated, each method step can be executed in different order.

[0023] The present application is further illustrated below with reference to the specific embodiments and the accompanying drawings.

[0024] Figure 1 A flow chart of a low-orbit satellite system electromagnetic compatibility design method in an embodiment of the present application is shown.

[0025] As Figure 1 shown, in an embodiment of the present application, the flow of the low-orbit satellite system electromagnetic compatibility design method includes: S1, a system-level electromagnetic environment is provided and demand analysis is performed, and this step is the design basis, the core of which is to clarify the "target and boundary" of the satellite system electromagnetic compatibility, so as to avoid subsequent design blindness, and the specific content includes: The core mission tasks of the satellite system, such as communication, remote sensing, and scientific exploration, determine the system's frequency range, upper limit of power spectral density, and sensitivity threshold, i.e., the maximum electromagnetic interference threshold that the equipment can withstand. These parameters directly determine the index benchmark for subsequent design.

[0026] Investigate all electronic equipment in the system, locate the main interference sources (such as high-power transmitters, SAR antennas, etc.) and sensitive equipment (in this embodiment, optical payload detectors, low-noise amplifiers, etc.), and determine their locations and working characteristics.

[0027] Identify potential paths for interference transmission from the interference source to the sensitive equipment, such as through cable coupling, spatial radiation coupling, and ground loop coupling, and form a list of interference links.

[0028] Based on the above analysis, develop system-level electromagnetic compatibility index requirements, such as radiation emission limits and conducted sensitivity limits.

[0029] S2, provide a hierarchical electromagnetic compatibility architecture, from the satellite hardware architecture level, achieve interference source control through "isolation, suppression, and optimized layout", divided into four sub-steps: S21, platform and payload isolation design, according to the electromagnetic characteristic differences between satellite platform equipment (such as power supply, attitude control system) and payload (such as SAR, optical camera), implement physical and electromagnetic double isolation in structural layout: Strong electromagnetic radiation equipment (in this embodiment, SAR transmitter, high-power data transmission module, etc.) is concentrated on one side of the satellite, and high-sensitivity payload (in this embodiment, optical detector, scientific exploration instrument, etc.) is arranged on the other side; A metal shielding compartment or shield is arranged between them, usually made of high-conductivity materials such as aluminum alloy and copper alloy, to block the direct transmission of spatial radiation interference.

[0030] S22, electromagnetic interference suppression of the power supply system, to solve the problem of power supply noise interfering with sensitive equipment through the power supply link, using independent power supply and multi-stage filtering scheme, including: Use distributed independent power bus to configure power supply circuit for sensitive payload (in this embodiment, optical payload, low-noise amplifier, etc.), avoiding sharing power supply with high-interference equipment; Install transient suppression devices such as TVS diodes at the input end of the power supply to deal with voltage spikes, and install multi-stage filtering networks such as π-type filter and common-mode choke to simultaneously suppress common-mode interference caused by different equipment to ground and differential-mode interference caused by interference between the positive and negative poles of the power supply.

[0031] S23, design and layout of on-board cable network, reduce coupling through cable selection and layout optimization: Sensitive signals (such as star sensor signals, scientific exploration data signals) adopt double-layer shielding cables, and the shielding layer needs to be 360-degree terminated, that is, tightly lapped with the connector shell to ensure the shielding integrity; The power lines and signal lines are separately laid to avoid power noise coupling to the signal; high-frequency lines (such as data transmission links) and low-frequency lines (such as control signals) need to be separately laid and parallel to each other with the length controlled within a minimum range to reduce electromagnetic induction between the lines; For key signal lines (such as high-speed data buses), a double-twisted structure is adopted to reduce differential mode interference or a coaxial structure to enhance the anti-radiation capability.

[0032] S24, Grounding system design, to avoid current interference caused by the potential difference of different equipment ground loops, a targeted grounding system is constructed: According to the characteristics of satellite equipment, single-point grounding (suitable for low-frequency signal equipment to avoid ground loops) or a combination of multi-point grounding and single-point grounding is adopted, in which multi-point grounding for high-frequency equipment reduces the grounding impedance, and single-point grounding for low-frequency equipment avoids interference; The power ground (power loop ground), signal ground (signal reference ground), and shielding ground (shielding layer ground) are clearly divided and independently connected to the main ground network to ensure low-impedance grounding path and prevent interference crosstalk between different types of ground.

[0033] S3, Frequency resource and signal integrity management, from the frequency planning and signal design point of view, to solve the problems of co-frequency interference and signal distortion, including: S31, Spectrum planning and assignment, for the risk of frequency overlap of multiple devices on the satellite (such as SAR, data transmission, and TT&C), the whole system spectrum is planned and allocated: The working frequency, bandwidth, and transmission time of all transmitting devices are uniformly allocated to avoid co-frequency interference; sufficient protection frequency bands are reserved for key receiving devices (such as low-noise receivers and scientific exploration receiving modules), which are 1-2 times the receiving bandwidth in this embodiment, to prevent adjacent frequency interference; Dynamic frequency allocation strategy is introduced to adjust the transmission parameters in real time according to the actual electromagnetic environment in orbit.

[0034] S32, Clock and signal design, clock signal is the reference of digital system, and signal distortion is an important source of interference, which is ensured through design: Low-jitter clock source is adopted, and in this embodiment, the jitter value is usually controlled within ps level to reduce the influence of clock noise on digital circuits; Ground wires are laid around the clock lines to isolate external radiation interference; Impedance matching for high-speed digital signals (in this embodiment, Gigabit Ethernet, LVDS data link, etc.), adjusting the PCB trace impedance to match the device impedance; and termination design, such as series matching resistance, parallel matching resistance, to reduce signal reflection and transmission distortion.

[0035] S33, anti-interference design of digital circuit, to enhance the anti-interference ability of digital chip (such as FPGA, CPU, star computer): Deploy multiple capacitance decoupling capacitors near the power supply pins of the digital chip, 0.1 μF ceramic capacitors and 10 μF tantalum capacitors in this embodiment, to suppress high-frequency noise on the power supply line and provide stable power supply for the chip; For key control signal lines such as reset signal and interrupt signal, use redundant design (such as dual backup) and watchdog monitoring (real-time monitoring of signal state, triggering reset when abnormal), to prevent signal interference from causing equipment downtime.

[0036] S4, provide software anti-interference and fault tolerance mechanism, to make up for the lack of hardware anti-interference from the software level, including: S41, data verification and error correction, to solve the problem of data transmission error caused by electromagnetic interference, use mature encoding algorithm: In the transmission and storage of star management data (such as device status data) and payload data (such as remote sensing image data, scientific exploration data), embed cyclic redundancy check (CRC, such as CRC32, fast detection of data error) or forward error correction encoding (FEC, such as Reed-Solomon encoding, can automatically correct part of the error data), to ensure data integrity.

[0037] S42, instruction redundancy and voting, to address the risk of key control instructions being interfered and tampered, to strengthen instruction reliability: For key control instructions such as SAR switch-on and off and satellite attitude adjustment, use multiple sending (such as triple redundant sending) or encoding verification (such as instructions with check code), to avoid single instruction loss or error; Use multiple voting mechanisms, such as 3-to-2 voting, after receiving 3 identical instructions, execute the instructions consistent with 2, to prevent single instruction interference from causing misoperation.

[0038] S43, state monitoring and autonomous recovery, to achieve fast response and recovery after interference, build a software monitoring closed loop: Software continuously collects electromagnetic environment parameters (such as interference signal strength) and working state parameters (such as bus error rate, device temperature) of key equipment, and sets threshold values, in this embodiment, bus error rate exceeds 10 -6 ; When the parameter is detected to be over the threshold, a preset process is automatically started, such as device reset (slight interference), switching backup device (moderate interference), entering safety mode (severe interference, such as shutting down high-power devices to ensure core functions).

[0039] S5, on-orbit electromagnetic compatibility prediction and verification is performed, professional electromagnetic simulation software (such as CST, FEKO) is used to perform system-level electromagnetic compatibility numerical simulation based on a satellite three-dimensional entity model and electromagnetic characteristic parameters (such as radiation emission power and sensitivity) of each device, an on-orbit space electromagnetic environment is simulated, coupling strength of interference sources and sensitive devices is predicted, and potential risk points (such as an area where a radiation field exceeds a standard) are located.

[0040] S6, ground test verification is performed, and a full-level and full-project ground test process is constructed to ensure that a physical product meets design requirements. Electromagnetic emission and sensitivity of a single device are tested to ensure that the single machine itself meets electromagnetic compatibility requirements; Compatibility between devices in a subsystem is tested to avoid interference in the subsystem; Electromagnetic compatibility of all devices of the satellite when working together is tested to simulate an on-orbit working scene; Intensity of interference transmitted by the device through a power line and a signal line is detected; External interference is simulated to be injected into the device through a cable to verify the anti-interference ability of the device; Intensity of interference radiated by the device through space is detected; Radiation interference in space is simulated to irradiate the device to verify the normal working ability of the device.

[0041] After the test is completed, the ground test result is substituted into the simulation model, the simulation parameters are corrected, and the prediction accuracy is improved; According to a result of combination of simulation and test, a design scheme is optimized, and on-orbit interference risk is reduced.

[0042] In an embodiment of the application, a certain low-orbit remote sensing satellite system is taken as an example, and the electromagnetic compatibility design method of the application is applied.

[0043] Firstly, step S1 is performed, the satellite system contains an S-band data transmission, an X-band synthetic aperture radar (SAR) load, various optical loads and a star service computer, the SAR transmitter is identified as a main interference source, and optical load detectors and low-noise amplifiers are sensitive devices.

[0044] Then, step S3 is performed. In S31, the SAR working period and the data transmission period are strictly planned to avoid mutual interference. In S32, impedance control and termination resistance matching are performed on the high-speed data bus. In S33, multiple decoupling capacitors with different capacitances are arranged near the power supply pins of the FPGA and CPU of the satellite computer.

[0045] Then, step S3 is performed. In S31, the SAR working period and the data transmission period are strictly planned to avoid mutual interference. In S32, impedance control and termination resistance matching are performed on the high-speed data bus. In S33, multiple decoupling capacitors with different capacitances are arranged near the power supply pins of the FPGA and CPU of the satellite computer.

[0046] Subsequently, step S4 is performed. In S41, the data transmission data is corrected by Reed-Solomon encoding. In S42, the SAR switch-on instruction is sent and checked by triple redundancy. In S43, the software monitors the bus error rate on the satellite, and automatically initiates bus reset when the threshold is exceeded.

[0047] Finally, steps S5 and S6 are performed. During the satellite development stage, electromagnetic simulation software (such as CST, FEKO) is used to simulate the radiation field of the whole satellite model. During the assembly stage, the satellite is tested according to the GJB151B standard to ensure that the indicators meet the requirements before launch.

[0048] In another embodiment of the present application, a low-orbit communication constellation system is taken as an example, which includes multiple satellites with similar functions.

[0049] According to the characteristics of the constellation system, when the above method is applied, special emphasis is placed on the system compatibility analysis in step S1 to ensure the frequency coordination between adjacent orbital surface satellites, inter-satellite links and satellite-ground links. In the frequency management of step S3, a dynamic frequency allocation strategy is introduced to dynamically adjust the transmission parameters according to the actual electromagnetic environment in orbit. In the software design of step S4, real-time signal-to-noise ratio monitoring and adaptive modulation and coding functions for inter-satellite link signals are added to cope with transient strong interference.

[0050] In addition, in step S5, multi-satellite joint simulation is used to evaluate the electromagnetic environment when multiple satellites in the constellation work simultaneously; in step S6, a constellation system-level EMC test platform is provided to simulate the multi-satellite cooperative working scenario and verify the system compatibility.

[0051] In another embodiment of the present application, taking a low-orbit scientific exploration satellite system as an example, the system is equipped with high-sensitivity exploration instruments, and the electromagnetic environment requirement is extremely harsh.

[0052] In the application of the method of the present application, the shielding and isolation design in step S2 is highlighted, a special electromagnetic shielding cabin is designed for the scientific load, and high shielding performance materials are used. In step S3, the frequency band of the scientific load is strictly protected, and a wider isolation frequency band is set. In step S4, a multi-level fault-tolerant mechanism is designed, including hardware redundancy and software recovery strategy, to ensure the integrity and availability of scientific data in the case of extreme interference.

[0053] Through the implementation of the above embodiments, the applicability and effectiveness of the method of the present application in different types of low-orbit satellite systems are verified, and a systematic and standardized solution for electromagnetic compatibility design of future complex satellite systems is provided.

[0054] Although the embodiments of the present application are described above, it should be understood that they are presented only as examples, not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made without departing from the spirit and scope of the present application. Therefore, the width and scope of the present application disclosed herein should not be limited by the above disclosed exemplary embodiments, but should be defined only according to the appended claims and their equivalent replacements.

Claims

1. A method for electromagnetic compatibility design of a low earth orbit satellite system, characterized by, Comprise: S1, provide system-level electromagnetic environment and conduct demand analysis; S2, provide hierarchical electromagnetic compatibility architecture; S3, conduct frequency resource and signal integrity management; S4, provide software anti-jamming and fault-tolerant mechanism; S5, conduct on-orbit electromagnetic compatibility prediction; and S6, conduct ground test verification.

2. The method of claim 1, wherein, Step S1 comprises: Determine the mission of the satellite system, determine the system operating frequency range, power spectral density upper limit and sensitivity threshold; Investigate the system electronic equipment, locate the interference source and sensitive equipment; Identify the path of the interference source to the sensitive equipment, and form an interference link list; and Based on the above analysis, the system-level electromagnetic compatibility index requirements are formulated.

3. The method of claim 1, wherein, Step S2 comprises: The electromagnetic radiation equipment is concentrated on one side of the satellite, and the load is arranged on the other side; and A metal shielding compartment or shield is provided between them.

4. The method of claim 3, wherein, Step S2 further comprises: A distributed independent power supply bus is used to separately configure power supply circuits for the load; and Transient suppression devices and multi-stage filter networks are installed at the power input end to simultaneously suppress common mode interference and differential mode interference.

5. The method of claim 3, wherein, Step S2 further comprises: For sensitive signals, a double-layer shielding cable is used, in which the shielding layer is 360-degree terminated to ensure shielding integrity; Power lines and signal lines are laid separately, and different frequency cables are laid separately, and the parallel wire length is controlled within a minimum range; and For some signal lines, a twisted pair structure or a coaxial structure is used to reduce differential mode interference.

6. The method of claim 3, wherein, Step S2 further comprises: A single-point grounding or a hybrid grounding system combining single-point grounding and multi-point grounding on the satellite is provided; and The power supply circuit ground, signal reference ground and shielding layer ground are all independently connected to the main ground network to avoid ground loop interference.

7. The method of claim 1, wherein, Step S3 comprises: The frequency, bandwidth and transmission time of all transmitting devices on the satellite are uniformly planned and assigned; Low-jitter clock sources are used to perform package ground processing on clock signals, and impedance matching and termination design are performed on high-speed digital signals; Multi-value decoupling capacitors are deployed near the power supply pins of digital chips; and The reset signal and interrupt signal control signal lines are backed up by dual channels and monitored by watchdog.

8. The method of claim 1, wherein, Step S4 comprises: In the transmission and storage of satellite management data and load data, cyclic redundancy check or forward error correction coding is embedded; Multiple sending or encoding check mechanisms are used for control instructions, and a multi-channel voting mechanism is used to execute instructions; and The software monitors the electromagnetic environment parameters and working status of the key equipment in real time, and when an anomaly is detected, the preset reset, backup switching or safety mode process is started.

9. The method of claim 1, wherein, Step S6 comprises: Test the electromagnetic emission and sensitivity of a single device to ensure that the single machine itself meets the electromagnetic compatibility requirements; Test the compatibility between devices in a subsystem to avoid interference within the subsystem; Test the electromagnetic compatibility of all devices working together on the satellite to simulate on-orbit working scenarios; Detect the interference intensity of the device transmitted through the power line and signal line; Simulate external interference injected into the device through the cable to verify the anti-interference ability of the device; Detect the interference intensity of the device radiated through space; and Simulate space radiation interference to illuminate the device to verify the normal working ability of the device.

10. The method of claim 1, wherein, Further comprise: The ground test result is substituted into the simulation model, the simulation parameter is corrected, and the prediction accuracy is improved; And According to the result of the simulation and the test combination, the design scheme is optimized, and the on-orbit interference risk is reduced.

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