CN115267771A - Satellite-borne Ka-band SAR system and on-orbit imaging working method thereof - Google Patents
Satellite-borne Ka-band SAR system and on-orbit imaging working method thereof Download PDFInfo
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
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- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9004—SAR image acquisition techniques
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- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/89—Radar or analogous systems specially adapted for specific applications for mapping or imaging
- G01S13/90—Radar or analogous systems specially adapted for specific applications for mapping or imaging using synthetic aperture techniques, e.g. synthetic aperture radar [SAR] techniques
- G01S13/9021—SAR image post-processing techniques
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
- G01S7/292—Extracting wanted echo-signals
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- G—PHYSICS
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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Abstract
The embodiment of the invention provides a satellite-borne Ka-band SAR system, wherein when the system works in an on-orbit imaging mode, a monitoring timer (3) controls a radar distributor (8) and an antenna power distribution unit (9) to power on each single machine; the monitoring timer (3) is used as a time reference of the satellite-borne Ka-band SAR system and controls the power-on and imaging time sequence of the system; under the control of the frequency synthesizer, a frequency synthesizer part of the frequency synthesizer receiver (4) generates a radio frequency master oscillator signal, and high-power high-orientation pulse wave beams are radiated to a designated area through a pre-power amplifier (6) and an antenna (1) in sequence; the ground object echo sequentially passes through an antenna (1), a pre-amplifier (6), a waveguide switch (7), an analog receiver part of a frequency synthesis receiver (4) and a digital receiver (5) to form formatted data and output the formatted data to a data transmission system, and the data transmission system is used for receiving the output data of the SAR system.
Description
Technical Field
The invention belongs to the technical field of synthetic aperture radars, and relates to a satellite-borne Ka-band SAR system.
Background
Because the atmospheric attenuation of the millimeter wave band is greater than that of the traditional low frequency band, the development of the satellite-borne millimeter wave SAR at the early stage is more limited. In recent years, with the development of a large number of millimeter wave SAR technical researches and the improvement of corresponding process levels, the satellite-borne millimeter wave SAR begins to enter a rapid development stage.
International famous space research institutions such as the european space agency, the de-aerospace, the dutch space agency, the italian alaian space shuttle company, the california academy of science and technology, the jet propulsion laboratory and the like successively put forward a plurality of sets of satellite-borne Ka waveband SAR technical schemes, but most of the schemes stay in the scheme demonstration stage and actual engineering realization is not carried out.
Among them, the face water and ocean Topograph (SWOT) satellite developed by the United states jet propulsion laboratory in conjunction with the French national space research center has entered the development stage and is expected to be launched in 2023. The main load of SWOT is InSAR of Ka wave band, the working frequency is 35GHz, the high-precision and wide swath measurement of sea surface can be realized by adopting 10m interference base line and 0.4-3.5 degree near-bottom observation, thereby researching the change of small and medium range in the sea; meanwhile, the height of the land water body can be measured, and the spatial and time distribution caused by storage and loss of the land water body is researched.
The prior art mostly stays at a scheme stage, only a SWOT system for engineering development adopts near-bottom vision observation, and the image resolution is poor.
Disclosure of Invention
The invention aims to provide a satellite-borne Ka-band SAR system aiming at the situation that an on-orbit satellite-borne SAR system is not available at home and abroad at present and meeting the requirement of satellite-borne millimeter wave fine earth observation.
The system comprises: the system comprises an antenna 1, an inner calibrator 2, a monitoring timer 3, a frequency synthesizer receiver 4, a digital receiver 5, a pre-amplifier 6, a waveguide switch 7, a radar distributor 8, an antenna power distribution unit 9 and a waveguide adapter plate 10; wherein,
the antenna transmits high-power high-orientation pulse beams to a free space and receives echo signals reflected by ground objects; providing a large angle electronic scanning capability in the distance direction; an internal calibration loop is provided for the satellite-borne Ka-band SAR system;
the inner calibrator 2 is used for matching with the antenna calibration network to realize calibration of system amplitude and phase performance so as to ensure system performance; measuring the relative variation of the total gain of the system, measuring the variation of the amplitude of a receiving and transmitting channel of the subsystem, and copying an LFM signal of the subsystem to provide a reference signal for imaging processing for correcting system errors;
the monitoring timer 3 is used as a time reference of the satellite-borne Ka-band SAR system, is used for ensuring the synchronization of receiving and sending work of the system, simultaneously executes remote control and remote measurement tasks of the ground to the system, controls the power-on and imaging time sequence of the system, detects the working state of the subsystem and realizes various measurement and control requirements of the ground to the system.
The frequency synthesizer receiver 4 comprises a frequency synthesizer and an analog receiver; the frequency synthesis adopts an implementation framework based on FPGA + DA, is compatible with two modes of waveform storage direct reading and waveform real-time calculation, compensates amplitude-phase errors of a system link through predistortion processing, generates a radio frequency master oscillation signal and sends the radio frequency master oscillation signal to a preamplifier 6; the analog receiver receives the radio frequency echo signal output from the waveguide switch, and outputs an intermediate frequency echo signal to the digital receiver 5 after frequency conversion and amplification;
the digital receiver 5 receives the instruction and the auxiliary data of the monitoring timer to complete the receiving and acquisition of the echo signals; carrying out down-conversion, digital filtering processing and BAQ compression on echo data, and combining and packaging the echo data and system auxiliary data to form a formatted data frame; outputting the packed formatted data to a data transmission system, wherein the data transmission system is used for receiving the output data of the SAR system;
the pre-amplifier 6 amplifies the main vibration signal output by the frequency synthesizer to meet the antenna power requirement and outputs the signal to the antenna;
the waveguide switch 7 is used for switching a calibration signal during system calibration, and is controlled by a monitoring timer to be switched to be effective in echo input or effective in calibration input in different calibration states;
the radar distributor 8 provides a primary power supply of 30V for each single machine in the cabin and controls the power on and off of each single machine; each single machine in the cabin does not comprise a monitoring timer, and the monitoring timer is directly powered by a satellite platform;
the antenna power distribution unit 9 provides a 60V primary power supply for an antenna secondary power supply and controls the power-on and power-off of the antenna secondary power supply;
the antenna and the pre-power amplifier and the waveguide switch are connected by adopting waveguides, so that the transmission loss is reduced; the pre-power amplifier and the waveguide switch are uniformly arranged on the waveguide adapter plate 10; the monitoring timer 3 controls the antenna beam pointing direction through the storage and the forwarding of the wave control code of the active phased array antenna.
Preferably, the frequency synthesizer consists of a reference frequency source and a frequency modulation signal source, and the reference frequency source provides a reference frequency and a clock signal for the SAR system by a crystal oscillator so as to ensure the coherence characteristic of the system; and generating various intermediate frequency and radio frequency references according to the reference clock output by the reference frequency source.
Preferably, the frequency modulation signal source generates a baseband linear frequency modulation signal meeting the system requirement according to the control signal and the timing signal by adopting a digital waveform generation mode; and obtaining the radio frequency linear frequency modulation signal with time domain, frequency domain and signal power meeting the requirements through quadrature modulation, intermediate frequency gating amplification, up-conversion, filtering and power amplification.
Preferably, the analog receiver consists of a high-frequency amplification and frequency conversion module and an intermediate-frequency amplification and MGC module; the high-frequency amplification and frequency conversion module completes down-conversion and filtering of the received signal to obtain an intermediate-frequency signal; the intermediate frequency amplifying and MGC module amplifies and controls the gain of the intermediate frequency echo signal to adapt to the dynamic output requirement of receiving.
Preferably, the waveguide switch 7 is switched to the echo input to be effective during imaging, so that the normal reception of ground echo is realized.
Preferably, the antenna adopts a waveguide slot active phased array antenna and has a large-angle electrical scanning capability.
Preferably, the inner calibrator adopts a non-delay calibration scheme and is matched with a waveguide switch array to realize high isolation among different loops, and the isolation among the loops is more than or equal to 70dB.
The invention also provides a method suitable for the satellite-borne Ka-band SAR system, which is characterized by comprising the following steps of:
step 1: the monitoring timer 3 controls the radar distributor 8 and the antenna distribution unit 9 to power on each single machine of the system;
step 2: the monitoring timer 3 controls a frequency modulation signal source of the frequency synthesis frequency synthesizer of the frequency synthesis receiver 4 to generate a broadband Linear Frequency Modulation (LFM) signal;
and 3, step 3: the LFM signal output by the frequency synthesizer is amplified by a pre-amplifier 6 and then output to the antenna 1 through a circulator;
and 4, step 4: the transmitted signal is amplified through power division and output to a gallium nitride TR component for power amplification, the power signal is output to a waveguide slot array surface through a circulator, and the high-power radiation signal is controlled to irradiate different imaging areas;
and 5: the antenna 1 receives echo signals reflected by the ground, the echo signals return to the TR component through the same path as the transmission, enter an R channel, are synthesized by a power divider for secondary amplification and are synthesized and output again;
step 6: the echo signal enters a pre-power amplifier and returns to the waveguide switch 7 through a circulator;
and 7: in a receiving state in an imaging mode, the waveguide switch is in a conducting state; the echo signal enters an analog receiver, and is subjected to low-noise amplification, down-conversion, intermediate-frequency filtering amplification and gain control to obtain an intermediate-frequency echo signal;
and 8: after the intermediate frequency signal enters the digital receiver 5, an SAR echo data stream is formed through AD acquisition, quadrature demodulation, filtering, extraction, BAQ compression and packing framing;
and step 9: and the data stream is transmitted to a ground receiving station through a data transmission subsystem, and a ground processing system carries out BAQ decompression and SAR imaging processing on the echo data to obtain a high-resolution ground scene image.
Drawings
Fig. 1 is a block diagram of a satellite-borne Ka-band SAR system according to the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description thereof.
The invention provides a satellite-borne Ka-band SAR system. The system comprises: the system comprises an antenna 1, an inner calibrator 2, a monitoring timer 3, a frequency synthesis receiver 4, a digital receiver 5, a pre-power amplifier 6, a waveguide switch 7, a radar distributor 8, an antenna power distribution unit 9 and a waveguide adapter plate 10; wherein,
the antenna transmits high-power high-orientation pulse beams to a free space and receives echo signals reflected by ground objects; providing a large angle electronic scanning capability in the distance direction; providing an internal calibration loop for the satellite-borne Ka-band SAR system;
the inner calibrator 2 is used for matching with the antenna calibration network to realize calibration of system amplitude and phase performance so as to ensure system performance; measuring the relative variation of the total gain of the system, measuring the variation of the amplitude of a receiving and transmitting channel of the subsystem, and copying an LFM signal of the subsystem to provide a reference signal for imaging processing for correcting system errors;
the monitoring timer 3 is used as a time reference of the satellite-borne Ka-band SAR system, is used for ensuring the synchronization of receiving and sending work of the system, simultaneously executes remote control and remote measurement tasks of the ground to the system, controls the power-on and imaging time sequence of the system, detects the working state of the subsystem and realizes various measurement and control requirements of the ground to the system.
The frequency synthesizer receiver 4 comprises a frequency synthesizer and an analog receiver; the frequency synthesis adopts an implementation framework based on FPGA + DA, is compatible with two modes of waveform storage direct reading and waveform real-time calculation, compensates amplitude-phase errors of a system link through predistortion processing, generates a radio frequency master oscillation signal and sends the radio frequency master oscillation signal to a preamplifier 6; the analog receiver receives the radio frequency echo signal output from the waveguide switch, and outputs an intermediate frequency echo signal to the digital receiver 5 after frequency conversion and amplification;
the digital receiver 5 receives the instruction and the auxiliary data of the monitoring timer to complete the receiving and acquisition of the echo signals; carrying out down-conversion, digital filtering processing and BAQ compression on echo data, and combining and packaging the echo data and system auxiliary data to form a formatted data frame; outputting the packed formatted data to a data transmission system, wherein the data transmission system is used for receiving the output data of the SAR system;
the pre-amplifier 6 amplifies the main vibration signal output by the frequency synthesizer to meet the antenna power requirement and outputs the signal to the antenna;
the waveguide switch 7 is used for switching a calibration signal during system calibration, and is controlled by a monitoring timer to be switched to be effective in echo input or effective in calibration input in different calibration states;
the radar distributor 8 provides a primary power supply of 30V for each single machine in the cabin and controls the power on and off of each single machine; each single machine in the cabin does not comprise a monitoring timer, and the monitoring timer is directly powered by a satellite platform;
the antenna power distribution unit 9 provides a 60V primary power supply for an antenna secondary power supply and controls the power on and off of the antenna secondary power supply;
the antenna and the pre-power amplifier and the waveguide switch are connected by adopting waveguides, so that the transmission loss is reduced; the pre-power amplifier and the waveguide switch are uniformly arranged on the waveguide adapter plate 10; the monitoring timer 3 controls the antenna beam pointing direction through the storage and the forwarding of the wave control code of the active phased array antenna.
According to one embodiment of the invention, the frequency synthesizer consists of a reference frequency source and a frequency modulation signal source, wherein the reference frequency source provides a reference frequency and a clock signal for the SAR system by a crystal oscillator so as to ensure the coherence characteristic of the system; and generating various intermediate frequency and radio frequency references according to the reference clock output by the reference frequency source.
According to one embodiment of the invention, the frequency modulation signal source adopts a digital waveform generation mode to generate a baseband linear frequency modulation signal meeting the system requirement according to the control signal and the timing signal; and obtaining the radio frequency linear frequency modulation signal with time domain, frequency domain and signal power meeting the requirements through quadrature modulation, intermediate frequency gating amplification, up-conversion, filtering and power amplification.
According to one embodiment of the invention, the analog receiver is composed of a high-frequency amplifying and frequency converting module and a medium-frequency amplifying and MGC module; the high-frequency amplification and frequency conversion module completes down-conversion and filtering of the received signal to obtain an intermediate-frequency signal; the intermediate frequency amplifying and MGC module amplifies and controls the gain of the intermediate frequency echo signal to adapt to the dynamic output requirement of receiving.
According to one embodiment of the invention, the waveguide switch 7 is switched to the echo input to be effective during imaging, and normal reception of ground echo is realized.
According to one embodiment of the invention, the antenna adopts a waveguide slot active phased array antenna and has a large-angle electric scanning capability.
According to one embodiment of the invention, the inner calibrator adopts a non-delay calibration scheme and is matched with the waveguide switch array to realize high isolation between different loops, and the isolation between the loops is more than or equal to 70dB.
The invention also provides an on-orbit imaging method suitable for the satellite-borne Ka-band SAR system, which comprises the following steps of:
step 1: the monitoring timer 3 controls the radar distributor 8 and the antenna distribution unit 9 to power up the single machines of the system;
step 2: the monitoring timer 3 controls a frequency modulation signal source of the frequency synthesis frequency synthesizer of the frequency synthesis receiver 4 to generate a broadband Linear Frequency Modulation (LFM) signal;
and step 3: the LFM signal output by the frequency synthesizer is amplified by a pre-amplifier 6 and then output to the antenna 1 through a circulator;
and 4, step 4: the transmitting signal is amplified through power division and output to the gallium nitride TR component for power amplification, and is output to the waveguide slot array surface through the circulator, and the high-power radiation signal is controlled to irradiate different imaging areas;
and 5: the antenna 1 receives echo signals reflected by the ground, the echo signals return to the TR component through the same path as the transmission, enter an R channel, are synthesized by a power divider for secondary amplification and are synthesized and output again;
and 6: the echo signal enters a pre-power amplifier and returns to the waveguide switch 7 through a circulator;
and 7: in a receiving state in an imaging mode, the waveguide switch is in a conducting state; the echo signal enters an analog receiver, and is subjected to low-noise amplification, down-conversion, intermediate-frequency filtering amplification and gain control to obtain an intermediate-frequency echo signal;
and 8: after the intermediate frequency signal enters the digital receiver 5, an SAR echo data stream is formed through AD acquisition, orthogonal demodulation, filtering, extraction, BAQ compression and packaging framing;
and step 9: and the data stream is transmitted to a ground receiving station through a data transmission subsystem, and a ground processing system carries out BAQ decompression and SAR imaging processing on the echo data to obtain a high-resolution ground scene image.
It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (8)
1. An on-board Ka-band SAR system, the system comprising: the antenna comprises an antenna (1), an inner calibrator (2), a monitoring timer (3), a frequency synthesizer receiver (4), a digital receiver (5), a pre-power amplifier (6), a waveguide switch (7), a radar distributor (8), an antenna power distribution unit (9) and a waveguide adapter plate (10); wherein,
the antenna (1) transmits high-power high-orientation pulse beams to a free space and receives echo signals reflected by ground objects; providing a large angle electronic scanning capability in the distance direction; providing an internal calibration loop for the satellite-borne Ka-band SAR system;
the inner calibrator (2) is used for matching with the antenna calibration network to realize calibration of the system amplitude and phase performance so as to ensure the system performance; measuring the relative variation of the total gain of the system, measuring the variation of the amplitude of a receiving and transmitting channel of the subsystem, and copying an LFM signal of the subsystem to provide a reference signal for imaging processing for correcting system errors;
the monitoring timer (3) is used as a time reference of the satellite-borne Ka-band SAR system, is used for ensuring the synchronization of receiving and sending work of the system, simultaneously executes remote control and remote measurement tasks of the ground to the system, controls the power-on and imaging time sequence of the system, detects the working state of the subsystem and realizes various measurement and control requirements of the ground to the system.
The frequency synthesizer receiver (4) comprises a frequency synthesizer and an analog receiver; the frequency synthesis adopts an implementation framework based on FPGA + DA, is compatible with two modes of waveform storage direct reading and waveform real-time calculation, compensates the amplitude-phase error of a system link through predistortion treatment, generates a radio frequency master oscillation signal and sends the radio frequency master oscillation signal to a preamplifier (6); the analog receiver receives the radio frequency echo signal output from the waveguide switch, and outputs an intermediate frequency echo signal to the digital receiver (5) after frequency conversion and amplification;
the digital receiver (5) receives the instruction and the auxiliary data of the monitoring timer to complete the receiving and acquisition of the echo signals; carrying out down-conversion, digital filtering processing and BAQ compression on echo data, and combining and packaging the echo data and system auxiliary data to form a formatted data frame; outputting the packed formatted data to a data transmission system, wherein the data transmission system is used for receiving the output data of the SAR system;
the pre-amplifier (6) amplifies a main vibration signal output by the frequency synthesizer to meet the antenna power requirement and outputs the main vibration signal to the antenna;
the waveguide switch (7) is used for switching a calibration signal during system calibration, and is controlled by the monitoring timer to be switched to be effective in echo input or effective in calibration input in different calibration states;
the radar distributor (8) provides a 30V primary power supply for each single machine in the cabin and controls each single machine to be powered on or powered off; each single machine in the cabin does not comprise a monitoring timer, and the monitoring timer is directly powered by a satellite platform;
the antenna power distribution unit (9) provides a 60V primary power supply for an antenna secondary power supply and controls the power on and off of the antenna secondary power supply;
the antenna and the pre-power amplifier and the waveguide switch are connected by adopting waveguides, so that the transmission loss is reduced; the pre-power amplifier and the waveguide switch are uniformly arranged on a waveguide adapter plate (10); and the monitoring timer (3) controls the antenna beam pointing direction through the storage and the forwarding of the active phased array antenna wave control code.
2. The spaceborne Ka-band SAR system of claim 1, wherein the frequency synthesizer is composed of a reference frequency source and a frequency modulation signal source, the reference frequency source provides a reference frequency and a clock signal for the SAR system by a crystal oscillator to ensure the coherence characteristic of the system; and generating various intermediate frequency and radio frequency references according to the reference clock output by the reference frequency source.
3. The spaceborne Ka-band SAR system of claim 1 wherein the FM signal source generates baseband chirp signals meeting system requirements according to control signals and timing signals in a digital waveform generation manner; and obtaining the radio frequency linear frequency modulation signal with time domain, frequency domain and signal power meeting the requirements through quadrature modulation, intermediate frequency gating amplification, up-conversion, filtering and power amplification.
4. The spaceborne Ka-band SAR system of claim 3 characterized in that the analog receiver is composed of a high frequency amplification and frequency conversion module, a medium frequency amplification and MGC module; the high-frequency amplification and frequency conversion module completes down-conversion and filtering of the received signal to obtain an intermediate-frequency signal; the intermediate frequency amplifying and MGC module amplifies and controls the gain of the intermediate frequency echo signal to adapt to the dynamic output requirement of receiving.
5. The space-borne Ka-band SAR system according to claim 1, wherein said waveguide switch (7) is switched active to the echo input during imaging, enabling a normal reception of ground echoes.
6. The spaceborne Ka-band SAR system of claim 1, wherein said antenna employs a waveguide slot active phased array antenna with large angle electrical scanning capability.
7. The spaceborne Ka-band SAR system of claim 1, characterized in that the inner calibrator adopts a non-delay calibration scheme and is matched with a waveguide switch array to realize high isolation between different loops, and the isolation between the loops is more than or equal to 70dB.
8. An on-orbit imaging working method suitable for the satellite-borne Ka-band SAR system of any one of claims 1-7, characterized by comprising the following steps:
step 1: the monitoring timer (3) controls the radar distributor (8) and the antenna power distribution unit (9) to power on each single machine of the system;
step 2: the monitoring timer (3) controls a frequency modulation signal source of the frequency synthesis frequency synthesizer of the frequency synthesis receiver (4) to generate a broadband Linear Frequency Modulation (LFM) signal;
and step 3: LFM signals output by the frequency synthesizer are amplified by a pre-amplifier (6) and then output to the antenna (1) through a circulator;
and 4, step 4: the transmitting signal is amplified through power division and output to the gallium nitride TR component for power amplification, and is output to the waveguide slot array surface through the circulator, and the high-power radiation signal is controlled to irradiate different imaging areas;
and 5: the antenna (1) receives echo signals reflected by the ground, the echo signals return to the TR component through the same path as the transmission, enter an R channel, are synthesized by the power divider for secondary amplification and are synthesized again for output;
step 6: the echo signal enters a pre-power amplifier and returns to a waveguide switch (7) through a circulator;
and 7: in a receiving state in an imaging mode, the waveguide switch is in a conducting state; the echo signal enters an analog receiver, and is subjected to low-noise amplification, down-conversion, intermediate-frequency filtering amplification and gain control to obtain an intermediate-frequency echo signal;
and 8: after the intermediate frequency signal enters a digital receiver (5), an SAR echo data stream is formed through AD acquisition, quadrature demodulation, filtering, extraction, BAQ compression and packing framing;
and step 9: and the data stream is transmitted to a ground receiving station through a data transmission subsystem, and a ground processing system carries out BAQ decompression and SAR imaging processing on the echo data to obtain a high-resolution ground scene image.
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| CN202210322875.8A CN115267771A (en) | 2022-03-29 | 2022-03-29 | Satellite-borne Ka-band SAR system and on-orbit imaging working method thereof |
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| CN117949949A (en) * | 2024-03-26 | 2024-04-30 | 长光卫星技术股份有限公司 | Pulse radar baseband signal acquisition processing method, device and medium |
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