Space-borne interference SAR (Synthetic Aperture Radar) system based on reflector antenna system and design method

Abstract

The invention provides a satellite-borne interference SAR (Synthetic Aperture Radar) system based on a reflector antenna system. The satellite-borne interference SAR system comprises a reflector antenna, a power combiner, a transceiving channel, a circulator, a low noise amplifier component, a radar processor and an inter-satellite communication terminal, the interference mode of the spaceborne interference SAR system adopts a two-satellite formation flight mode, and the spaceborne interference SAR system configurations of the two satellites are completely consistent; during working, any satellite is set as a primary satellite, and the other satellite is set as a secondary satellite; time, space and phase synchronization is carried out on the satellite-borne interference SAR systems of the two satellites, space synchronization is achieved through the satellites, time synchronization is achieved through an S-frequency-band and Ka-frequency-band communication link, and phase synchronization between the satellite-borne interference SAR systems is achieved through an X-frequency-band and Ka-frequency-band communication link. The system has the advantages of stable performance, high efficiency, strong expansion capability and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of space synthetic aperture radar, and relates to an interferometric SAR system based on a reflector antenna system and a design method. BACKGROUND

[0002] Satellite-borne synthetic aperture radar (SAR) technology can image and observe the earth all day long without being restricted by sunlight and weather conditions, and has a certain ground penetration capability, and has unique advantages in disaster monitoring, environmental monitoring, ocean monitoring, resource exploration, crop yield estimation, mapping and military applications, and can play a role that optical remote sensing methods cannot play. According to the different forms of radar antennas used, synthetic aperture radar can be mainly divided into phased array antenna systems and reflector antenna systems, and the two systems have their own technical characteristics.

[0003] The interferometric SAR system is a further application of the general SAR system, and by interferometric processing of two radar images covering the same area, the phase difference of the same pixel point is extracted, and then the terrain elevation information is obtained. The differential interferometric mode can also be used to measure the small deformation of the ground, and thus becomes an important means of geological and disaster monitoring.

[0004] At present, satellite-borne interferometric SAR systems using phased array antenna systems have been widely used, but the multiple antenna beams of the phased array antenna make it difficult to stabilize the radiation accuracy of the radar, and it is difficult to meet the quantitative remote sensing application. For large phased array SAR systems, due to the excessive number of antenna units and channel units, the hardware structure and signal processing of the system are very complex, and the low-efficiency power amplifier makes the system have a very large working power consumption. Therefore, the increase in weight and power consumption caused by the large antenna scale restricts the application of small satellite platforms, and further limits the large-scale application of distributed satellites. SUMMARY

[0005] The technical problem of the present application is to overcome the shortcomings of the prior art and provide a satellite-borne interferometric SAR system based on a reflector antenna system and a design method. The system has the advantages of stable performance, high efficiency and strong expansion capability.

[0006] The object of the present application is achieved by the following technical solution: a satellite-borne interferometric SAR system design method based on a reflector antenna system, comprising:

[0007] According to the application requirements and the orbit height of the satellite-borne interferometric SAR system, the spatial resolution p and the observation width B required by the satellite-borne interferometric SAR system are determined w ;

[0008] According to the mapping accuracy requirement of the spaceborne interferometric SAR system, errors affecting the absolute height accuracy, the relative height accuracy, the absolute plane accuracy and the relative plane accuracy of the spaceborne interferometric SAR system are decomposed, a de-coherence coefficient γ related to the errors of the absolute height accuracy, the relative height accuracy, the absolute plane accuracy and the relative plane accuracy is analyzed, and an interferometric phase error probability density function p φ (φ) is solved, working parameters of the spaceborne interferometric SAR system, including a system sensitivity NEσ0, a range ambiguity RASR and an azimuth ambiguity AASR, are determined;

[0009] According to a spatial resolution ρ, an observation width B w and the system sensitivity NEσ0 required by the spaceborne interferometric SAR system, an imaging working mode of the radar is set, a beam width of the antenna, an average transmitting power are determined, and a beam transmitting-receiving timing parameter is optimized, so that the beam transmitting-receiving timing parameter meets the range ambiguity RASR and the azimuth ambiguity AASR;

[0010] According to the imaging working mode of the radar, the beam width of the antenna, the average transmitting power and the beam transmitting-receiving timing parameter, a peak transmitting power, a size of an antenna aperture, a receiver noise coefficient and a working bandwidth range of the spaceborne interferometric SAR system are determined, and a form of the antenna and a transmitting power combiner are determined.

[0011] A spaceborne interferometric SAR system based on a reflector antenna system, comprising a reflector antenna, a power combiner, a transmitting-receiving channel, a circulator, a low-noise amplifier assembly, a radar processor and an inter-satellite communication terminal;

[0012] The reflector antenna is used for radiating and receiving radar electromagnetic signals.

[0013] The radar processor generates radar signals, triggers a working timing of the spaceborne interferometric SAR system, and realizes bus remote control, telemetry parameter acquisition and framing of the radar system.

[0014] The transmitting-receiving channel realizes up-conversion and driving amplification of a radar transmitting excitation signal and down-conversion and power amplification of a radar echo signal.

[0015] The power combiner is used for power amplification of the radar transmitting excitation signal.

[0016] The circulator is a transmitting-receiving conversion switch for the radar signals, and performs conversion of the radar signal transmitting and receiving.

[0017] The low-noise amplifier assembly performs low-noise amplification of the radar echo signal.

[0018] The frequency reference generates a reference signal of the radar system, and performs frequency reference conversion.

[0019] The inter-satellite communication terminal realizes inter-satellite communication and phase solution.

[0020] Further, the interference mode of the spaceborne interferometric SAR system adopts a two-satellite formation flight mode, and the spaceborne interferometric SAR systems of the two satellites are configured completely identically; in operation, any one of the satellites is set as a main satellite, and the other satellite is set as a deputy satellite; the spaceborne interferometric SAR systems of the two satellites are time-, space-, and phase-synchronized, wherein the space synchronization is achieved by the satellites, the time synchronization is achieved by using S-band and Ka-band communication links, and the phase synchronization between the spaceborne interferometric SAR systems is achieved by using X-band and Ka-band communication links.

[0021] Further, the spaceborne interferometric SAR system is provided with a unified frequency reference source for providing a reference for the transceiving channels of the SAR load, and the frequency reference source is also provided for an inter-satellite communication terminal, which transmits and receives the frequency and phase difference of the frequency reference sources on the two different satellites through the inter-satellite link to achieve time synchronization and phase synchronization; the inter-satellite communication terminal includes S-band, X-band, and Ka-band.

[0022] Further, the reflector antenna adopts an umbrella-shaped retractable solid network combined parabolic antenna, which includes a solid surface reflector, a feed waveguide, a locking and releasing mechanism, a feed support structure, a metal reflecting net, and an antenna rib; the solid surface reflector and the metal reflecting net form an antenna reflector, and the solid surface reflector is connected with the satellite platform; the metal reflecting net is installed on the solid surface reflector through the arc-shaped antenna ribs which are uniformly distributed in the circumferential direction; the feed waveguide realizes the transmission and feeding of microwave signals, and is installed on the solid surface reflector at the center of the antenna together with the feed support structure; the locking and releasing mechanism is installed on the top of the feed support structure; before the satellite is launched, each antenna rib is locked through the locking and releasing mechanism, and after the satellite is launched, the locking and releasing mechanism is released in orbit to realize the on-orbit deployment of the reflector antenna.

[0023] Further, the power combiner includes a plurality of phase-shifting / attenuation components, traveling wave tube amplifiers, and a power combination matrix; the phase-shifting / attenuation components include a phase shifter and an attenuator, which adjust the amplitude and phase of the corresponding traveling wave tube amplifiers; each traveling wave tube amplifier amplifies the power of the microwave signal; and the power combination matrix combines the powers of the microwave signals output by the traveling wave tube amplifiers.

[0024] Further, the power combination matrix adopts a four-port Butler matrix, the input is divided into four identical traveling wave tube amplifiers, the input phase weight is set as [0, π / 2, π / 2, π], the power of each traveling wave tube amplifier is 1700 watts, and the combined power is greater than 6400 watts.

[0025] Further, the traveling wave tube amplifier comprises a high-voltage power supply, a preamplifier and a traveling wave tube, the high-voltage power supply performs high-voltage conversion from direct current to direct current, and provides various voltages required for the traveling wave tube to work; the traveling wave tube performs power amplification on the microwave signal, the traveling wave tube is of conduction type heat dissipation, and the gate control is of pulse type; the preamplifier performs driving amplification on the microwave signal; the preamplifier and the high-voltage power supply are installed on a box body, and are connected with the traveling wave tube through a high-voltage cable and a radio frequency cable.

[0026] Further, the transceiving channel comprises a transmitting up-conversion, a receiving up-conversion and an in-system loop scaler, and performs frequency conversion and amplitude and phase scaling of the space-borne interferometric SAR system.

[0027] Further, the radar processor comprises a radar intermediate frequency signal source, a timing unit, an acquisition and compression unit and a remote control and telemetry unit, the intermediate frequency signal source generates the radar signal, the timing unit generates the working timing of the space-borne interferometric SAR system and performs timing triggering, the acquisition and compression unit performs acquisition and data compression of the radar echo signal and the scaling signal; the remote control and telemetry unit realizes bus remote control, telemetry parameter acquisition and framing of the radar system, and communicates with a satellite data management system.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) The whole system of the present application adopts the architecture of a high-power traveling wave tube amplifier and a reflector antenna, and has the advantages of stable performance, high efficiency and strong expansion capability;

[0030] (2) The inter-satellite synchronization scheme of the present application adopts a time-frequency synchronization scheme of cross correction through a multi-band inter-satellite link, and has the advantages of high synchronization accuracy, stable synchronization performance and strong redundancy capability;

[0031] (3) The reflector antenna of the present application has a unique beam, and the beam performance is stable, which is beneficial to improve the radiation stability of the radar system; the reflector antenna has a low sidelobe characteristic, so that the radar has good ambiguity performance, which is beneficial to improve the coherence of the system and the elevation measurement accuracy;

[0032] (4) The power combining matrix of the present application has the characteristics of low loss and high combining efficiency, and the pulse traveling wave tube amplifier has the characteristics of high power, high efficiency and light weight;

[0033] (5) The system of the present application has moderate volume, weight and power consumption, and is suitable for launching on a small satellite platform, and has strong practicability. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The figure is a system composition block diagram (double-satellite system) of the present application;

[0035] Figure 2A schematic diagram of the reflector antenna structure of the present application;

[0036] Figure 3 A block diagram of the high-power combiner of the present application;

[0037] Figure 4 A schematic diagram of the traveling wave tube amplifier structure of the present application; DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0039] A satellite-borne interferometric SAR system design method based on reflector antenna technology, comprising:

[0040] (1) According to the application requirements and the orbit height of the satellite-borne interferometric SAR system, the spatial resolution p and the observation width B required by the radar system are determined w ;

[0041] (2) Interferometric SAR parameter design: according to the system's mapping accuracy requirements, the errors affecting the absolute height accuracy, relative height accuracy, absolute plane accuracy, and relative plane accuracy of the interferometric SAR are decomposed, the de-coherence coefficient γ related to the errors of the absolute height accuracy, relative height accuracy, absolute plane accuracy, and relative plane accuracy is analyzed, the interferometric phase error probability density function is solved, and the working parameter distribution of the radar system is determined according to the distribution results, including the system sensitivity NEσ0, range ambiguity RASR, and azimuth ambiguity AASR;

[0042] (3) System working parameter calculation: according to the spatial resolution and the observation width determined in step (1) and the system sensitivity NEσ0 determined in step (2), the imaging working mode of the radar, the beam width of the antenna, and the average transmit power are designed, and the beam transmit-receive timing parameters are optimized to meet the range ambiguity RASR and the azimuth ambiguity AASR determined in step (2);

[0043] (4) System scheme design: according to the system working parameters in step (3), the peak transmit power, the size of the antenna aperture, the receiver noise coefficient, and the system working bandwidth range are determined, the detailed index distribution of each component of the system is completed, and the form of the antenna and the scheme of the transmit power combiner are determined.

[0044] A satellite-borne interferometric SAR system based on reflector antenna technology, comprising a reflector antenna, a high-power combiner, a transceiver channel, a circulator, a low-noise amplifier component, a radar processor, and an inter-satellite communication terminal.

[0045] The reflector antenna adopts a circular aperture meshed parabolic antenna or a super-elliptical aperture solid parabolic antenna, the antenna has an azimuth dimension greater than 4 meters and a range dimension greater than 2 meters;

[0046] The high-power combiner adopts a four-port power combiner matrix form, four same traveling wave tube amplifiers are inputted, the difficulty of high output power of a single power amplifier is solved, and high combining efficiency is realized;

[0047] The transceiver channel comprises a transmitting up-converter, a receiving up-converter and an in-system looped scaler, and realizes frequency conversion and amplitude and phase calibration of the system;

[0048] The low-noise amplifier assembly comprises a limiter, an isolator and a low-noise amplifier, and has a noise coefficient less than 2 dB;

[0049] The inter-satellite communication terminal comprises an S-band inter-satellite communication machine, an X-band solid-state amplifier and a Ka-band transceiver terminal, realizes time synchronization and phase synchronization of a dual-inter-satellite load system, realizes 20 ns of time synchronization, realizes 3° of phase synchronization, and realizes cross-redundancy and precision correction of different frequency band devices.

[0050] Embodiment

[0051] A satellite-borne interferometric SAR system design method based on a reflector antenna system, comprising the following steps:

[0052] (1) System requirement analysis: the satellite orbit height is 500 km, high-resolution SAR imaging and interferometric SAR mapping are considered, the two-dimensional imaging resolution of the system is required to be better than 2 meters, and the mapping width is required to be better than 20 kilometers;

[0053] (2) Interferometric SAR parameter design: the system meets the requirements of 1:25000 scale, the absolute height accuracy is better than 3 meters, the relative height accuracy is better than 2 meters, the decorrelation coefficient γ is better than 0.7 according to error analysis, and the interferometric phase error probability density function p φ (φ) is solved:

[0054]

[0055] Wherein, φ represents the interferometric phase, Γ represents the gamma function, L represents the view number,

[0056] is a Gauss hypergeometric function.

[0057] Further, the standard deviation σ φ of the interferometric phase error is solved:

[0058]

[0059] Within the 10-meter grid coordinates, with a total system view count of 25, the above correlation coefficients meet the requirements for elevation accuracy. Under this constraint, the radar system operating parameters are determined to have system sensitivity NEσ0 better than -22dB, range ambiguity RASR better than -20dB, and azimuth ambiguity AASR better than -20dB.

[0060] (3) Calculation of system operating parameters: Based on the spatial resolution of 2 meters and the observation width of 20 kilometers determined in step (1), and the system sensitivity NEσ0 determined in step (2) is not greater than -22 dB, the radar imaging working mode is designed to be strip working mode, the antenna beam width in range is 1.5°, the beam width in azimuth is 0.5°, and the average transmission power is 1200 watts;

[0061] (4) System design: According to the system operating parameters in step (3), the radar peak transmission power is greater than 6400 watts, the antenna aperture is 4 meters, the receiver noise coefficient is less than 3dB, the system maximum operating bandwidth is 300MHz, the antenna adopts a circular aperture parabolic umbrella antenna, and the transmission power synthesizer uses a 4-port Butler matrix as the power synthesis matrix, which is synthesized into a high-power signal through 4 traveling wave tube amplifiers.

[0062] The above method is used to design a satellite-borne interferometric SAR system based on a reflector antenna system, including a reflector antenna, a high-power synthesizer, a transceiver channel, a circulator, a low-noise amplifier component, a radar processor, and an intersatellite communication terminal. The interference method adopts the method of two satellites flying in formation. The SAR system configurations of the two satellites are completely consistent. When working, any satellite can be set as the main satellite and the other satellite as the secondary satellite. The SAR systems of the two satellites need to be synchronized in time, space, and phase. Spatial synchronization is achieved through satellites, time synchronization is achieved using S-band and Ka-band communication links, and inter-system phase synchronization is achieved using X-band and Ka-band communication links. The block diagram of the dual-satellite SAR system is shown below. Figure 1 As shown in the figure, the radar processor is the central control and processing unit of the radar system. The transceiver channel implements up-conversion and drive amplification of the radar transmission excitation signal and down-conversion and power amplification of the radar echo signal. The high-power synthesizer is used for power amplification of the radar excitation signal. The circulator is the transmit-receive switch of the radar signal. The low-noise amplifier implements low-noise amplification of the radar echo signal. The frequency reference realizes reference signal generation and frequency reference conversion of the radar system. The inter-satellite communication terminal realizes communication and phase resolution between two satellites.

[0063] The satellite-borne interferometric SAR system based on the reflector antenna system uses a unified frequency reference source to provide a reference for the SAR payload channel. At the same time, the reference source is provided to the inter-satellite communication terminal. The frequency and phase difference of the frequency reference sources on two different satellites are corrected through inter-satellite links to achieve time synchronization and phase synchronization. The inter-satellite communication terminal includes three channels: S-band, X-band, and Ka-band. Among them, the S-band is dedicated to data communication and combines with the GNSS system to achieve time synchronization. The X-band is dedicated to signal measurement and is shared with the SAR transceiver channel to achieve phase cross-measurement. The Ka-band takes into account both data communication and signal measurement, serving as redundancy for the S-band and X-band, and can improve synchronization accuracy through error extraction and cross-correction.

[0064] The reflector antenna is the core component of the interferometric SAR system, responsible for the radiation and reception of radar electromagnetic signals. An umbrella-shaped, retractable, fixed-net combined parabolic antenna is selected. The core components are composed of a fixed-surface reflector 1, a feed waveguide 2, a locking and releasing mechanism 3, a feed support structure 4, a metal reflective mesh 5, and antenna ribs 6. Figure 2 As shown, the solid surface reflector 1 and the metal reflective mesh 5 together constitute an antenna reflector. The solid surface reflector 1 is directly connected to the satellite platform. The metal reflective mesh 5 is installed on the solid surface reflector 1 through the antenna ribs 6. The feed waveguide 2 realizes the transmission and feeding of microwave signals and is installed together with the feed support structure 4 on the solid surface reflector in the center of the antenna. The locking and releasing mechanism 3 is installed on the top of the feed support structure 4. All the antenna ribs 6 of the antenna are locked together before the satellite is launched. After the satellite is launched, they are released in orbit to realize the in-orbit deployment of the antenna.

[0065] The high power combiner consists of phase shift / attenuation components, traveling wave tube amplifiers, and power combining matrices, such as Figure 3 As shown in the figure, the phase shift / attenuation component includes a phase shifter and an attenuator to adjust the amplitude and phase of the amplifier. The traveling wave tube amplifier realizes the power amplification of the microwave signal. The power synthesis matrix realizes the power synthesis of the microwave signal. A four-port Butler matrix is ​​used as the power synthesis matrix. The input is divided into four identical traveling wave tube amplifiers. The input phase weight is set to [0,π / 2,π / 2,π]. The synthesis efficiency is better than 97%. The power of each traveling wave tube amplifier is 1700 watts, and the synthesized power is greater than 6400 watts.

[0066] The traveling wave tube amplifier consists of a high voltage power supply 7, a preamplifier 8, and a traveling wave tube 9. Figure 4 As shown, the high-voltage power supply 7 realizes high-voltage DC-DC conversion and provides various voltages required for the operation of the traveling wave tube 9. The traveling wave tube 9 realizes power amplification of the microwave signal. The traveling wave tube 9 uses conductive heat dissipation and gate-controlled pulse operation. The pre-amplifier 8 realizes drive amplification of the microwave signal. The pre-amplifier 8 and the high-voltage power supply 7 are installed in a box body and are connected to the traveling wave tube 9 through a high-voltage cable and a radio frequency cable.

[0067] The transceiving channel comprises transmitting up-conversion, receiving up-conversion, and an inner-loop scaler, so as to realize frequency conversion and amplitude and phase scaling of the system;

[0068] The radar processor is composed of a radar intermediate frequency signal source, a timing unit, an acquisition and compression unit, and a remote control and telemetry unit, the intermediate frequency signal source completes generation of radar signals, the timing unit realizes working timing and triggering of the whole radar system, the acquisition and compression unit completes acquisition and data compression of radar echo signals and scaling signals, and the remote control and telemetry unit realizes total control of the radar system, acquisition and framing of telemetry parameters, and communication with a satellite data management system.

[0069] Compared with a conventional large phased array radar system, the above-mentioned system solution can solve the problem of small satellite platforms carrying out interferometric measurement tasks, and has the characteristics of stable performance and high efficiency, the adopted two-satellite synchronization scheme has the advantages of high synchronization accuracy, stable synchronization performance, strong redundancy, and the like, and has strong practicability.

[0070] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0071] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A design method for a spaceborne interferometric SAR system based on a reflector antenna system, characterized in that: include: According to the application requirements and orbital height of the spaceborne interferometric SAR system, the spatial resolution ρ and observation width B required by the spaceborne interferometric SAR system are determined. w ; According to the surveying and mapping accuracy requirements of the spaceborne interferometric SAR system, the errors affecting the absolute elevation accuracy, relative elevation accuracy, absolute plane accuracy, and relative plane accuracy of the spaceborne interferometric SAR system are decomposed, the decorrelation coefficient γ related to the errors of absolute elevation accuracy, relative elevation accuracy, absolute plane accuracy, and relative plane accuracy is analyzed, and the probability density function of the interferometric phase error p is solved. φ (φ), determine the operating parameters of the spaceborne interferometric SAR system, including system sensitivity NEσ0, range ambiguity RASR, and azimuth ambiguity AASR; According to the spatial resolution ρ and observation width B required by the spaceborne interferometric SAR system w and system sensitivity NEσ0, set the radar imaging working mode, determine the antenna beam width and average transmit power, and optimize the beam transmit and receive timing parameters so that the beam transmit and receive timing parameters meet the range ambiguity RASR and azimuth ambiguity AASR; According to the radar's imaging working mode, antenna beam width, average transmit power, and beam transmission and reception timing parameters, the peak transmit power, antenna aperture size, receiver noise factor, and operating bandwidth range of the spaceborne interferometric SAR system are determined, as well as the antenna form and transmit power synthesizer.

2. A spaceborne interferometric SAR system based on a reflector antenna system, characterized in that: Including reflector antenna, power combiner, transceiver channel, circulator, low noise amplifier component, radar processor, and intersatellite communication terminal; Reflector antennas are used to radiate and receive radar electromagnetic signals; The radar processor generates radar signals, triggers the working sequence of the spaceborne interferometric SAR system, and realizes bus remote control, telemetry parameter acquisition and framing of the radar system; The transceiver channel realizes the up-conversion and drive amplification of the radar transmission excitation signal and the down-conversion and power amplification of the radar echo signal. The power combiner is used to amplify the power of the radar transmission excitation signal; The circulator is a radar signal transceiver switch that converts the radar signal between transceiver and receiver. The low noise amplifier component performs low noise amplification of the radar echo signal; The frequency reference generates the reference signal of the radar system and performs frequency reference conversion; Intersatellite communication terminals enable communication and phase resolution between satellites.

3. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 2, characterized in that: The interferometric SAR system adopts the interferometric method of two satellites flying in formation, and the configuration of the spaceborne interferometric SAR systems of the two satellites is completely identical. During operation, any one satellite is set as the primary satellite and the other satellite is set as the secondary satellite. The spaceborne interferometric SAR systems of the two satellites are synchronized in time, space, and phase, among which spatial synchronization is achieved by the satellites, time synchronization is achieved by S-band and Ka-band communication links, and phase synchronization between the spaceborne interferometric SAR systems is achieved by X-band and Ka-band communication links.

4. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 3, characterized in that: The satellite-borne interferometric SAR system uses a unified frequency reference source to provide a reference for the transceiver channels of the SAR payload. The frequency reference source is also provided to the intersatellite communication terminal. The frequency and phase differences of the frequency reference sources on two different satellites are corrected through inter-satellite links to achieve time synchronization and phase synchronization. The intersatellite communication terminal includes S-band, X-band, and Ka-band frequencies.

5. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 4, characterized in that: The reflector antenna adopts an umbrella-shaped foldable fixed-net combined parabolic antenna, comprising a fixed-surface reflector (1), a feed waveguide (2), a locking and releasing mechanism (3), a feed support structure (4), a metal reflective mesh (5), and antenna ribs (6); the fixed-surface reflector (1) and the metal reflective mesh (5) form an antenna reflector, and the fixed-surface reflector (1) is connected to a satellite platform; the metal reflective mesh (5) is mounted on the fixed-surface reflector (1) through arc-shaped antenna ribs (6) uniformly distributed along the circumference; the feed waveguide (2) realizes the transmission and feeding of microwave signals, and is mounted together with the feed support structure (4) on the fixed-surface reflector (1) located at the center of the antenna; the locking and releasing mechanism (3) is mounted on the top of the feed support structure (4); before the satellite is launched, each antenna rib (6) is locked by the locking and releasing mechanism (3), and is released on orbit after the satellite is launched, so as to realize the on-orbit deployment of the reflector antenna.

6. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 5, characterized in that: The power combiner includes several phase shift / attenuation components, traveling wave tube amplifiers and a power combination matrix; the phase shift / attenuation components include phase shifters and attenuators, which adjust the amplitude and phase of the corresponding traveling wave tube amplifiers, and each traveling wave tube amplifier amplifies the power of the microwave signal; the power combination matrix combines the power of the microwave signals output by each traveling wave tube amplifier.

7. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 6, characterized in that: The power synthesis matrix adopts a four-port Butler matrix, the input is divided into four identical traveling wave tube amplifiers, the input phase weight is set to [0,π / 2,π / 2,π], the power of each traveling wave tube amplifier is 1700 watts, and the combined power is greater than 6400 watts.

8. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 7, characterized in that The traveling wave tube amplifier comprises a high-voltage power supply (7), a preamplifier (8) and a traveling wave tube (9). The high-voltage power supply (7) performs high-voltage conversion from direct current to direct current, and provides various voltages required for the operation of the traveling wave tube (9); the traveling wave tube (9) performs power amplification on microwave signals, and the traveling wave tube (9) performs conductive heat dissipation and gate-controlled pulse operation; the preamplifier (8) drives and amplifies the microwave signals; the preamplifier (8) and the high-voltage power supply (7) are installed on a box body, and are connected to the traveling wave tube (9) via a high-voltage cable and a radio frequency cable.

9. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 8, characterized in that: The transceiver channel includes a transmitting up-converter, a receiving up-converter and a system inner-loop calibrator, which performs frequency conversion and amplitude and phase calibration of the spaceborne interferometric SAR system.

10. The spaceborne interferometric SAR system based on a reflector antenna system according to claim 9, characterized in that: The radar processor includes a radar intermediate frequency signal source, a timing unit, an acquisition and compression unit, and a remote control and telemetry unit. The intermediate frequency signal source generates radar signals, the timing unit generates the working timing of the space-borne interferometric SAR system and performs timing triggering, the acquisition and compression unit acquires radar echo signals and calibration signals and performs data compression; the remote control and telemetry unit realizes bus remote control of the radar system, telemetry parameter acquisition and framing, and communicates with the satellite data management system.

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