Methods for Testing and Verifying Radio Frequency Compatibility of Microwave Payload Remote Sensing Satellite Prototype (Sea Breeze & Waves)

Abstract

This invention provides a method for testing and verifying the radio frequency (RF) compatibility of a prototype microwave payload remote sensing satellite for ocean wind and waves. The method includes the following steps: preparing an RF link simulator that represents the RF transmission characteristics of a microwave spectrometer prototype; installing the simulator in the mounting compartment of the microwave spectrometer prototype on the satellite; verifying the impact of the simulator's transmission state on the receiving and operational performance of the onboard equipment; verifying the impact of the onboard equipment's transmission state on the receiving performance of the simulator; verifying whether the radiated electric field strength in the spectrometer mounting compartment meets the requirements when both the simulator and the onboard equipment are transmitting; and verifying whether the electric field strength radiated by the simulator meets the radiation sensitivity requirements of the onboard equipment. This invention uses a microwave spectrometer RF link simulator instead of the original spectrometer product to verify the electromagnetic compatibility between the spectrometer and the onboard equipment, thereby achieving verification of the overall RF compatibility of the satellite prototype and reducing the risks and costs of developing the entire satellite without electrical components.

Description

Technical Field

[0001] This invention belongs to the field of satellite electromagnetic compatibility testing technology, and specifically relates to a method for testing and verifying the radio frequency compatibility of a prototype remote sensing satellite with ocean wind and wave microwave payload. Background Technology

[0002] The main payloads of the ocean wind and wave microwave remote sensing satellite are a microwave scatterometer and a microwave spectrometer. Both payloads are active microwave remote sensing devices, operating at frequencies in the Ku band, and their frequencies are relatively close. Both remote sensing payloads have high transmit power and high receive sensitivity. Furthermore, due to the small satellite platform and limited onboard space, coupled with the high antenna gain of both remote sensing payloads resulting in large antenna sizes, the distance between the two antennas cannot be increased, leading to strong coupling between them. Therefore, electromagnetic compatibility testing and verification between the two radar payloads is crucial for ensuring satellite performance.

[0003] Electromagnetic compatibility (EMC) testing during the satellite integration phase is conducted to verify the EMC of the platform and payload equipment under satellite-wide conditions. During the design phase, the overall satellite EMC design specifications are completed, serving as the basic requirements for the EMC design of each subsystem. During the prototype phase, radiated model satellite (antenna isolation) testing is completed, along with equipment-level (electrical or qualification product) EMC tests required by the overall satellite design specifications. After the satellite completes overall product acceptance, satellite-wide EMC testing is performed, including overall satellite electrical testing and simulated flight testing. Satellite-wide EMC testing can be divided into conducted and radiated tests. Conducted tests primarily verify EMC transmitted through cables, including ripple and surge, while radiated tests primarily verify EMC caused by unintentional radiation from antenna terminals, flanges, equipment housings, and cables.

[0004] Currently, the traditional method for verifying the radio frequency compatibility (RF) of a satellite during the prototype stage is for the equipment manufacturer to develop electrical or qualification products and participate in the satellite's electromagnetic compatibility (EMC) testing. This method is relatively realistic, but it requires the development of prototype electrical equipment, which is costly. For many international collaborative projects, since foreign parties often do not provide electrical or qualification components, it is impossible to conduct complete satellite RF compatibility testing during the prototype stage, leading to significant technical risks. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method for testing and verifying the radio frequency compatibility of a prototype remote sensing satellite with ocean wind and wave microwave payloads. This method solves the problem that the radio frequency compatibility of the entire satellite cannot be verified during the prototype stage when there are no electrical components.

[0006] The technical solution of this invention is:

[0007] A method for testing and verifying the radio frequency compatibility of a prototype remote sensing satellite with a microwave payload for ocean wind and waves. The microwave payload is a microwave spectrometer, whose antenna includes a SWIM antenna, which comprises six rotatable feed horn antennas with different beam angles. The method includes the following steps:

[0008] 1) Prepare a microwave spectrometer RF link simulator. The transmitting link of the simulator can represent the RF transmission characteristics of the microwave spectrometer prototype, including a SWIM antenna, a traveling wave tube amplifier, and a filter; the receiving link uses an EMI receiver to receive antenna signals.

[0009] 2) The simulation component is installed in the mounting compartment of the microwave spectrometer prototype on the satellite and connected to the signal generator via a coaxial cable; the simulation component has two operating modes: a transmit mode and a receive mode. In the transmit mode, the simulation component receives the Chirp test signal sent by the signal generator and transmits it through the SWIM antenna; in the receive mode, the simulation component receives the signal received by the SWIM antenna through an EMI receiver.

[0010] 3) Set the simulator to transmission mode, and allow the on-board equipment to operate normally. Test the impact of the electromagnetic emission of the simulator's antenna on the receiving and operating performance of the on-board equipment. Verify whether the satellite radio frequency compatibility requirements are met based on the test results. The on-board equipment includes at least a scatterometer, GPS, data transmission subsystem, and telemetry and control subsystem.

[0011] 4) Set the simulation device to receive mode, and the on-board equipment transmits signals in their respective operating frequency bands. Test the signal strength received by the EMI receiver of the simulation device, and verify whether the satellite radio frequency compatibility requirements are met based on the measured received signal strength.

[0012] 5) Set the simulation component to the transmission mode, and the on-board equipment transmits signals of their respective operating frequency bands at maximum power to test the electric field strength in the installation chamber of the microwave spectrometer prototype. Verify whether the electric field strength in the installation chamber meets the satellite radio frequency compatibility requirements based on the measured electric field strength.

[0013] 6) Remove the simulation component from the installation compartment of the microwave spectrometer prototype on the satellite, set the simulation component to the transmission mode, test the electric field strength radiated by it, and verify whether it meets the satellite radio frequency compatibility requirements based on the measured electric field strength radiated by the simulation component.

[0014] Preferably, the radio frequency transmission characteristics include at least transmission power, insertion loss, bandwidth, pulse repetition frequency, and pulse period.

[0015] Preferably, in step 4), verifying whether the satellite radio frequency compatibility requirements are met based on the measured received signal strength specifically involves: determining whether the signal is an interference signal within the operating frequency band of the onboard equipment or a noise signal within the operating frequency band of the microwave spectrometer based on the frequency of the received signal.

[0016] If the interference signal is within the operating frequency band of the on-board equipment, its signal strength I n Interference signal sensitivity limit S1 of microwave spectrometer n Comparison, if S1 n -I n If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

[0017] If the signal is noise within the operating frequency band of the microwave spectrometer, its signal strength N is... n The noise signal sensitivity limit S2 of the microwave spectrometer n Comparison, if S2 n -N n If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

[0018] Preferably, in step 5), the electric field strength inside the mounting chamber of the microwave spectrometer prototype is tested, and the satellite radio frequency compatibility requirements are verified based on the measured electric field strength inside the mounting chamber. Specifically:

[0019] The electric field strength at different locations within the installation cabin was measured within the operating frequency band of each on-board device, and the maximum electric field strength E within the installation cabin was obtained. i The radiation sensitivity limit E of the spectrometer s Compare, if E s -E i If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

[0020] Preferably, in step 6), verifying whether the satellite radio frequency compatibility requirements are met based on the measured electric field strength radiated by the simulated component specifically involves: obtaining the maximum value E of the electric field strength radiated by the simulated component. Ire The maximum radiation sensitivity limit E of each onboard device SRs Compare, if E SRs -E Ire If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

[0021] Preferably, the threshold is equal to 6dB.

[0022] The advantages of this invention compared to the prior art are:

[0023] (1) This invention replaces the entire subsystem by designing a simple radio frequency link simulator, namely a simulator of the transmit link and the receive link, which not only makes the test method simpler, but also greatly shortens the test time.

[0024] (2) The spectrumr RF link simulator transmission link used in this invention can represent the transmission characteristics of the spectrumr subsystem in the RF transmission path. Its in-band and out-of-band transmission characteristics at its RF output port can simulate the transmission characteristics of the real equipment of the spectrumr subsystem, reducing the technical risks caused by the lack of real equipment test results. Since the spectrumr RF link simulator transmission link can fully represent the characteristics of the real equipment, a closed-loop test circuit is constructed using the spectrumr RF link simulator transmission link to build a complete and real whole-satellite test environment for RF EMC testing of other equipment of the whole satellite.

[0025] (3) The spectrometer radio frequency link analog receiver link used in this invention is used to test various interference signals received by the spectrometer antenna within the working frequency band of the spectrometer and the working frequency band of each transmitter on the satellite, in order to evaluate whether other devices on the satellite will interfere with the spectrometer through the coupling of the spectrometer antenna. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the radio frequency link simulation component for the microwave spectrometer of the present invention;

[0027] Figure 2 This is a schematic diagram of the interference link between the microwave spectrometer and the on-board equipment of this invention. Detailed Implementation

[0028] The features and advantages of the present invention will become clearer and more explicit through the following detailed description.

[0029] To address the issue of insufficient verification of the satellite's radio frequency compatibility during the prototype testing phase of the ocean wind and wave microwave payload remote sensing satellite, which lacked the electrical components of a spectrometer, the interference between the spectrometer and other onboard equipment was first analyzed.

[0030] The sources of interference on the satellite include: T1: emission from the spectrometer antenna; T2: emission from the spectrometer cable and housing; T3: emission from other satellite equipment antennas; T4: emission from other satellite equipment cables and housings.

[0031] The satellite's sensitive receivers include: R1: Spectrometer antenna receiver; R2: Spectrometer cable and housing receiver; R3: Other satellite equipment antenna receiver; R4: Other satellite equipment cable and housing receiver.

[0032] Interference links between the spectrometer and other satellite equipment, such as Figure 2As shown, there are a total of 8 interference links, and electromagnetic compatibility verification of these interference links needs to be completed during the radio frequency electromagnetic compatibility process.

[0033] To conduct electromagnetic compatibility verification, this invention developed an RF link simulation device that can represent the RF link transmission characteristics of the spectrometer prototype, such as... Figure 1 As shown,

[0034] The composition of the spectrometer RF link simulator differs from that of the flight product, but it represents all the transmission characteristics (power, insertion loss, bandwidth, pulse repetition frequency, etc.) of the flight product. The spectrometer RF link simulator includes:

[0035] Antenna: Uses the same antenna as the flight product, which can rotate automatically (0.25 to 5.6 revolutions per minute), but switching between the 6 beams requires manual operation; Traveling wave tube amplifier (BWB) and its power supply: Provides the required RF power; Filters: Includes a transmit high-pass filter and a scatterometer band-stop filter; EMI receiver replaces the receive link; Automatic selector switch for transmit or receive mode.

[0036] The RF link analog device is connected to the ground auxiliary equipment via the following cables: a coaxial cable for the horizontal amplifier and two cables for power supply and telemetry / remote control of the horizontal amplifier.

[0037] All these cables pass through the port on the satellite, and all the cables are divided into two parts: a short section inside the satellite that connects to the onboard equipment components of the radio frequency link simulator, and a long section outside the satellite that connects to the ground support equipment of the radio frequency link simulator.

[0038] Other cables that do not run inside the satellite also require ground-based auxiliary equipment to connect to the RF link emulator, including:

[0039] One signal receiving coaxial cable; one signal transmitting coaxial cable; two motor drive cables (power supply and command); one transmit / receive switching drive cable.

[0040] The radio frequency (RF) link simulator for the spectrometer should be a flight-ready product whose RF characteristics fully represent the flight product's characteristics not only within the spectrometer's band but also outside the spectrometer's band (scatterometer band, data transmission band, telemetry and control band, and GPS band) to assess satellite RF compatibility. The signal generator settings are shown in the table below.

[0041] Table 1 Signal parameters of the radio frequency link analog component of the spectrometer of the present invention

[0042]

[0043]

[0044] The spectrometer equipment used in the test is shown in Table 2.

[0045] Because the spectrometer RF link simulator differs from the flight-ready product, its installation also differs, resulting in different electric field radiated emissions. In testing, only the electromagnetic compatibility related to radiation emitted by the SWIM antenna was verified.

[0046] The spectrometer's chirp signal is generated by ground-based auxiliary equipment outside the satellite. The ground-based auxiliary equipment, which is analogous to the spectrometer's radio frequency link, is located close to the satellite (approximately 2-3 meters away).

[0047] All spectrometer RF link analog devices are powered by ground auxiliary equipment (powered by 220 volts), and there is no electrical connection between the spectrometer RF link analog devices and the satellite platform equipment.

[0048] Table 2 Characteristics of the spectrometer tested in this invention

[0049] Serial Number equipment Electricity (volts) Location 1 signal source 220 Approximately 2-3 meters from the satellite 2 Receiver 220 Approximately 2-3 meters from the satellite 3 Low-frequency isolator Passive On the Star 4 Release Passive On the Star 5 Horizontal Amplifier Power Supply 220 On the Star 6 High frequency isolator Passive On the Star 7 H-filter Passive On the Star 8 Emission scattering filter Passive On the Star 9 antenna Passive On the Star 10 motor 220 On the Star

[0050] The spectrometer antenna rotates automatically and continuously (at speeds ranging from 0.25 rpm to 5.6 rpm) without requiring commands to be transmitted to the antenna via satellite. The antenna's rotation speed is remotely controlled by a computer within the auxiliary testing room. The spectrometer antenna motor does not return any information about its angular position; therefore, it is necessary to switch to manual mode to operate the antenna's rotation.

[0051] Switching between feed horns requires manual intervention. The switching matrix between the six feed horns has been removed to avoid associated losses, thereby ensuring in-band and out-of-band transmit power for the flight simulation product.

[0052] The spectrometer RF link analog can operate in two different modes:

[0053] Transmission mode: Power, pulse repetition frequency, and pulse period are the same as those for flight products;

[0054] Receive mode: The receiver (spectrum analyzer) is connected to the antenna port via a switch.

[0055] The implementation steps for verifying the compatibility of the receiving link with the two interference paths of electromagnetic emission from antennas, cables, and housings of other onboard equipment coupled and received by the spectrometer antenna using RF link emulators are as follows:

[0056] Confirm that the spectrometer beam settings are correct, and set the test sequence as follows: 0° beam, 2° beam, 4° beam, 6° beam, 8° beam, 10° beam. Power on the satellite.

[0057] The spectrometer is set to receive channel;

[0058] The scatterometer antenna rotates at the default speed;

[0059] The spectrometer antenna rotates at the default speed, and the spectrometer tests the received signal.

[0060] The spectrometer switched to the next beam and the test was performed again.

[0061] The spectrometer receiver receives interference signals I from each transmitter at the six fed horn antenna terminals. n and the noise signal N within the spectrometer band n , and the sensitivity limit S1 of the spectrometer n S2 n Comparison, if S1 n -I n >6dB and S2 n -N n With a sensitivity >6dB, and the spectrometer's individual immunity also meeting the limit requirements, the compatibility of the interference path where electromagnetic emissions from other onboard devices are coupled and received by the spectrometer's antenna is verified.

[0062] The implementation steps for verifying the compatibility of the spectrum analyzer's transmission via an analog radio frequency link with the two interference paths—the antenna, cable, and housing of the onboard electronic equipment—are as follows:

[0063] Confirm that the spectrometer beam settings are correct and set the test sequence as follows: 0° beam, 2° beam, 4° beam, 6° beam, 8° beam, 10° beam. Power on the satellite.

[0064] The spectrometer is set to connect to the transmission channel;

[0065] The spectrometer antenna rotates at the default speed.

[0066] The scatterometer is working normally, and both the receiving and transmitting channels are powered on.

[0067] The scatterometer antenna rotates at the default speed to test the scatterometer. The data transmission subsystem records the scatterometer data, including the scatterometer echo signal, signal calibration, and noise calibration.

[0068] Check if the GPS is functioning correctly;

[0069] Adjust the uplink level of the monitoring and control system to the sensitivity setting.

[0070] Check if the transponder telemetry is working properly;

[0071] The transponder sends two self-test commands to check whether the commands are received normally.

[0072] The uplink of the telemetry and control system is disconnected once, and the capture and lock-up are checked to see if they are normal.

[0073] When the spectrometer's transmitting simulation equipment and data transmission are powered on, and the spectrometer antenna is operating normally, the power level received by the scatterometer is the same as when the spectrometer's transmitting simulation equipment and data transmission are not powered on. Therefore, the scatterometer is not affected by interference from the spectrometer's transmitting simulation equipment or data transmission. Performance tests at sensitivity levels can also be performed on the transponder and GPS receiver to confirm radio frequency compatibility.

[0074] Four small sniffer antennas are arranged inside the satellite's cabin, one at each corner, for the spectrometer equipment. Each sniffer antenna is a WR75 open waveguide, connected to a wave-to-scan converter and a low-noise amplifier. The four coaxial cables of the sniffers and four power cables are then routed through the satellite cable hatch to the ground auxiliary equipment. The electric field strength inside the satellite cabin is evaluated using a sniffer testing system. Measurements are performed using a spectrum analyzer, and the field (assuming free-space propagation) can be calculated using the sniffer's conversion function.

[0075] The implementation steps for verifying the compatibility of the interference path—where the electromagnetic emissions from the antennas, cables, and housings of other onboard equipment are coupled and received by the housings and cables of the spectrometer's various electronic devices—using the sniffers testing system are as follows:

[0076] To confirm that the sniffer link is functioning correctly, a sniffer self-test is performed first. This self-test must be conducted before the formal test begins, and all devices must be powered off. SWIM will use the spectrometer's emission mode in the sniffer test; the electromagnetic field emitted by the spectrometer will be detected by the sniffer.

[0077] All equipment was powered on (spectrometer in transmit mode, scatterometer in transmit / receive mode, GPS powered on, data transmission in transmit mode, and telemetry and control in transmit mode). The power of the four sniffers was measured. Since this test is not closely related to the feedhorn, it was only performed when the 10-degree horn was operating.

[0078] Sniffers measured the field strength E across various frequency bands in spectrometers, scatterometers, and data transmission systems. I , and the radiation sensitivity limit requirement E of the spectrometer S Comparison, E S -E I With a signal strength >6dB and no other high-power signals received in other frequency bands, and the spectrometer confirmed to meet radiation sensitivity limits, the compatibility of the interference path—where electromagnetic emissions from other onboard devices are coupled and received by the spectrometer's electronic equipment housings and cables—is verified.

[0079] To verify the compatibility of electromagnetic emissions from the housings and cables of the spectrometer's various electronic devices with interference paths of antenna coupling and reception by the onboard electronic devices' antennas, housings, and cables, the electromagnetic field radiation limit E of the spectrometer was used. Ire The test results were analyzed in conjunction with the electric field radiation sensitivity limit E of other electronic devices on the satellite. SRs Compared with the test results, E SRs -E Ire With a value >6dB and all devices meeting the limits for electric field radiation emission and electric field radiation sensitivity, the compatibility of the two interference paths—the electromagnetic emission from the housings and cables of the spectrometer's electronic equipment being coupled and received by the antennas, housings, and cables of the onboard electronic equipment—is verified.

[0080] The above description is only the best specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the protection scope of the present invention.

[0081] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for testing and verifying the radio frequency compatibility of a prototype remote sensing satellite with a microwave payload for ocean wind and waves, wherein the microwave payload is a microwave spectrometer, and its antenna includes a SWIM antenna, wherein the SWIM antenna includes six rotatable feed horn antennas with different angle beams; characterized in that... Includes the following steps: 1) Prepare a microwave spectrometer RF link simulator. The transmitting link of the simulator can represent the RF transmission characteristics of the microwave spectrometer prototype, including a SWIM antenna, a traveling wave tube amplifier, and a filter; the receiving link uses an EMI receiver to receive antenna signals. 2) The simulation component is installed in the mounting compartment of the microwave spectrometer prototype on the satellite and connected to the signal generator via a coaxial cable; the simulation component has two operating modes: a transmit mode and a receive mode. In the transmit mode, the simulation component receives the Chirp test signal sent by the signal generator and transmits it through the SWIM antenna; in the receive mode, the simulation component receives the signal received by the SWIM antenna through an EMI receiver. 3) Set the simulator to transmission mode, and allow the on-board equipment to operate normally. Test the impact of the electromagnetic emission of the simulator's antenna on the receiving and operating performance of the on-board equipment. Verify whether the satellite radio frequency compatibility requirements are met based on the test results. The on-board equipment includes at least a scatterometer, GPS, data transmission subsystem, and telemetry and control subsystem. 4) Set the simulation device to receive mode, and the on-board equipment transmits signals in their respective operating frequency bands. Test the signal strength received by the EMI receiver of the simulation device, and verify whether the satellite radio frequency compatibility requirements are met based on the measured received signal strength. 5) Set the simulation component to the transmission mode, and the on-board equipment transmits signals of their respective operating frequency bands at maximum power to test the electric field strength in the installation chamber of the microwave spectrometer prototype. Verify whether the electric field strength in the installation chamber meets the satellite radio frequency compatibility requirements based on the measured electric field strength. 6) Remove the simulation component from the installation compartment of the microwave spectrometer prototype on the satellite, set the simulation component to the transmission mode, test the electric field strength radiated by it, and verify whether it meets the satellite radio frequency compatibility requirements based on the measured electric field strength radiated by the simulation component.

2. The method for testing and verifying the radio frequency compatibility of a microwave payload remote sensing satellite prototype for ocean wind and waves according to claim 1, characterized in that, The radio frequency transmission characteristics include at least the transmit power, insertion loss, bandwidth, pulse repetition frequency, and pulse period.

3. The method for testing and verifying the radio frequency compatibility of a microwave payload remote sensing satellite prototype for ocean wind and waves according to claim 2, characterized in that, In step 4), the satellite radio frequency compatibility requirements are verified based on the measured received signal strength. Specifically, the signal is determined to be an interference signal within the operating frequency band of the on-board equipment or a noise signal within the operating frequency band of the microwave spectrometer based on the frequency of the received signal. If the interference signal is within the operating frequency band of the on-board equipment, its signal strength I n Interference signal sensitivity limit S1 of microwave spectrometer n Comparison, if S1 n -I n If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met. If the signal is noise within the operating frequency band of the microwave spectrometer, its signal strength N is... n The noise signal sensitivity limit S2 of the microwave spectrometer n Comparison, if S2 n -N n If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

4. The method for testing and verifying the radio frequency compatibility of a microwave payload remote sensing satellite prototype for ocean wind and waves according to claim 3, characterized in that, In step 5), the electric field strength inside the mounting chamber of the microwave spectrometer prototype is tested, and the satellite radio frequency compatibility requirements are verified based on the measured electric field strength inside the mounting chamber. Specifically: The electric field strength at different locations within the installation cabin was measured within the operating frequency band of each on-board device, and the maximum electric field strength E within the installation cabin was obtained. i The radiation sensitivity limit E of the spectrometer s Compare, if E s -E i If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

5. The method for testing and verifying the radio frequency compatibility of a microwave payload remote sensing satellite prototype for ocean wind and waves according to claim 4, characterized in that, In step 6), the verification of whether the satellite radio frequency compatibility requirements are met is based on the measured electric field strength radiated by the simulated component. Specifically, this involves obtaining the maximum value E of the electric field strength radiated by the simulated component. Ire The maximum radiation sensitivity limit E of each onboard device SRs Compare, if E SRs -E Ire If the threshold is met, the satellite radio frequency compatibility requirement is satisfied; otherwise, the requirement is not met.

6. The method for testing and verifying the radio frequency compatibility of a microwave payload remote sensing satellite prototype for ocean wind and waves according to claim 5, characterized in that, The threshold is equal to 6dB.

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