Satellite-borne ultrahigh-resolution SAR (synthetic aperture radar) system and working method thereof

Abstract

The invention discloses a satellite-borne ultrahigh-resolution SAR (Synthetic Aperture Radar) system and a working method thereof. The system comprises a signal processor, a frequency multiplication unit, a receiver, a synthesis network front end, a traveling wave tube amplifier group, an amplitude limiting low noise amplifier, a magic T, a waveguide switch, a circulator, a waveguide load and an umbrella antenna, the system is loaded on an agile satellite platform, and large-angle scanning imaging of a target area is achieved by means of maneuvering of the platform. Various working methods are provided through combination of output signals of different ports of the magic T. The ultra-high resolution imaging system has the advantages that ultra-high resolution imaging superior to centimeter-level resolution is realized, the working mode is flexible, the reliability is good, the system composition is simple, the volume and the weight of the product are reduced through centralized transmitting and receiving, the weight is light, the heat consumption is small, and the engineering development cost and difficulty are reduced.

Description

Technical Field

[0001] The invention belongs to the field of spaceborne synthetic aperture radar (SAR), and relates to a spaceborne ultra-high resolution SAR system and a working method thereof. Background Art

[0002] The rapid development of remote sensing applications has put forward higher and higher requirements on the resolution of spaceborne SAR, and the resolution requirement has increased from decimeter level to centimeter level. As the system resolution gradually increases, the bandwidth of the system's transceiver signals also increases. Centimeter-level resolution requires a system bandwidth of more than 4GHz. There are two main systems of spaceborne SAR: one is SAR based on phased array antennas; the other is SAR based on reflector antennas. When the bandwidth increases to several GHz, phased array antennas will face the problems of severe dispersion and inconsistent full-bandwidth beam pointing, while reflector antennas do not have these problems and are particularly suitable for use in high-resolution SAR. At present, the maximum bandwidth of international spaceborne SAR systems has only reached 1.2GHz, and the corresponding resolution is about 0.3m, which cannot meet the needs of centimeter-level resolution. Therefore, there is an urgent need for a spaceborne ultra-high-resolution SAR system and its working method. Summary of the invention

[0003] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a satellite-borne ultra-high resolution SAR system and a working method thereof to solve the above-mentioned deficiencies in the prior art. The system realizes the generation of ultra-wide bandwidth signals through a frequency doubling unit, transmits the signal using a reflective antenna and receives ground echoes, and divides the ultra-wide bandwidth echoes into multiple small and medium bandwidth echoes using a power divider and a filter inside the receiver and down-converts them to an intermediate frequency, and finally completes multi-channel analog-to-digital conversion at the signal processor to convert them into data and output them in a frame; the system can generate signals with a bandwidth exceeding 4 GHz, meeting the needs of centimeter-level resolution.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems: A spaceborne ultra-high resolution SAR system comprises: a signal processor, a frequency multiplication unit, a synthesis network front end, a traveling wave tube amplifier group, a magic T, a waveguide load, a waveguide switch, a circulator, an umbrella antenna, a frequency synthesizer, a limiting low noise amplifier and a receiver; wherein: The signal processor is used to generate intermediate frequency signals with small and medium bandwidths and send them to the frequency multiplication unit. At the same time, it collects the multi-channel intermediate frequency echoes output by the receiver, and then frames the collected data for output. The signal processor also receives external remote control to generate various control signals within the system and returns telemetry signals. The frequency multiplication unit is used to multiply the intermediate frequency transmission signal with small or medium bandwidth to the required bandwidth range to meet the system resolution requirements; The synthesis network front end can receive the RF signal output by the frequency multiplication unit and send it to four phase shifters for phase adjustment after power division; A traveling wave tube amplifier group, including four traveling wave tube amplifiers, is used to complete the power amplification of the radio frequency signal; Three magic Ts can combine the different signal phases controlled by the phase shifters to complete the power synthesis of high-power RF signals; Three waveguide switches can realize the selective output of three high-power RF signals; Three waveguide loads can absorb leakage signals and ensure the system has low electromagnetic leakage; Circulator, used to send high-power transmission signal to the umbrella antenna, and then send the echo received by the umbrella antenna to the limited low-noise amplifier; Umbrella antenna, used to radiate high-power radio frequency signals and receive ground echoes; Frequency synthesizer, used to generate the clock required by the signal processor and the local oscillator signal required by the receiver; Limiting low noise amplifier, used to withstand high-power leakage signals to prevent them from affecting subsequent electronic equipment, while completing the amplification of low-power echo signals; The receiver is used to divide the broadband echo signal into multiple paths. Each path selects the frequency band through a different filter, and then down-converts it to the required intermediate frequency and sends it to the signal processor for collection.

[0005] The present invention also includes the following technical features: Specifically, the umbrella antenna is installed outside the satellite cabin and maneuvers in conjunction with the satellite platform during the imaging process to achieve large-angle scanning imaging of the target area.

[0006] Specifically, the principle for selecting the number of power splitters inside the receiver is: let the system RF signal bandwidth divided by the signal processor acquisition rate and then multiplied by 2.4 be M, and the number of power splitters N be the smallest integer greater than or equal to M.

[0007] Specifically, the three magic Ts are magic T1, magic T2 and magic T3, and the four ports of magic T1, magic T2 and magic T3 are port 1, port 2, port 3 and port 4 respectively; the three waveguide switches are waveguide switch 1, waveguide switch 2 and waveguide switch 3, and the three waveguide loads are waveguide load 1, waveguide load 2 and waveguide load 3.

[0008] Specifically, the four phase shifters are phase shifter 1, phase shifter 2, phase shifter 3 and phase shifter 4; the four traveling wave tube amplifiers are traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3 and traveling wave tube amplifier 4.

[0009] Specifically, the system has three working modes, each of which corresponds to different settings, including phase shifter settings, number of traveling wave tube amplifiers, and waveguide switch settings; the working method flow in all working modes is: The signal processor generates an intermediate frequency signal with a small or medium bandwidth, the frequency multiplication unit completes signal bandwidth expansion to generate a radio frequency signal with a required bandwidth, the synthesis network front end completes power division and phase shifting, the traveling wave tube amplifier group completes power amplification, and the high-power signal is sent to the circulator through the selection of the magic T and waveguide switch, reaches the umbrella antenna and radiates out, and the echo received by the umbrella antenna enters the limiting low-noise amplifier after passing through the circulator for amplification. The amplified echo is divided into a plurality of small or medium bandwidth echoes by a power divider and a filter inside the receiver, and down-converted to the intermediate frequency, and finally the multi-channel analog-to-digital conversion is completed at the signal processor to become data and output in a frame.

[0010] The working method of the spaceborne ultra-high resolution SAR system is as follows: in the first working mode, the transmission power is 2 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting correspond to the following two setting methods: Mode 1: TWT amplifiers 1 and 2 are working, phase shifter 1 is set to 0°, and phase shifter 2 is set to 180°; TWT amplifiers 3 and 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide switch 3, waveguide switch 2 is set so that the signal is connected from waveguide switch 3 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from waveguide switch 1 to circulator; at this time, the high-power transmission signal is output from port 4 of magic T1, passes through waveguide switch 1 and waveguide switch 3 to the circulator, and finally radiates from the umbrella antenna; Mode 2: TWT amplifier 1 and TWT amplifier 2 do not work; TWT amplifier 3 and TWT amplifier 4 work, phase shifter 3 is set to 0°, and phase shifter 4 is set to 180°; waveguide switch 1 is set so that the signal is connected from waveguide switch 3 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide switch 3, and waveguide switch 3 is set so that the signal is connected from waveguide switch 2 to the circulator; at this time, the high-power transmission signal is output from port 4 of magic T2, reaches the circulator after passing through waveguide switch 2 and waveguide switch 3, and finally radiates from the umbrella antenna.

[0011] Specifically, in the second working mode, the transmission power is 4 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting method are: Traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3, and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 2 is set to 0°, phase shifter 3 is set to 0°, and phase shifter 4 is set to 0°; waveguide switch 1 is set so that the signal is connected to waveguide load 1 from port 4 of magic T1, waveguide switch 2 is set so that the signal is connected to waveguide load 2 from port 4 of magic T2, and waveguide switch 3 is set so that the signal is connected to the circulator from port 3 of magic T3; at this time, the high-power transmission signal is output from port 3 of magic T1 and magic T2, and after being synthesized by magic T3, it enters waveguide switch 3 and circulator, and finally radiates from the umbrella antenna.

[0012] Specifically, in the third working mode, the transmission power is 1 times the output power of the traveling wave tube amplifier; there are four corresponding setting modes for the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting: Mode 1: Traveling wave tube amplifier 1 and traveling wave tube amplifier 3 are working, phase shifter 1 is set to 0°, and phase shifter 3 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 2: Traveling wave tube amplifier 1 and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 4 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 3: TWT amplifier 2 and TWT amplifier 3 are working, phase shifter 2 is set to 0°, and phase shifter 3 is set to 0°; TWT amplifier 1 and TWT amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 4: TWT amplifier 2 and TWT amplifier 4 are working, phase shifter 2 is set to 0°, and phase shifter 4 is set to 0°; TWT amplifier 1 and TWT amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected to waveguide load 1 from port 4 of magic T1, waveguide switch 2 is set so that the signal is connected to waveguide load 2 from port 4 of magic T2, and waveguide switch 3 is set so that the signal is connected to the circulator from port 3 of magic T3; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna.

[0013] Compared with the prior art, the present invention has the following technical effects: The present invention generates and transmits an ultra-wide bandwidth radio frequency signal with a bandwidth of several GHz through a signal processor, a frequency multiplication unit, a traveling wave tube amplifier, a magic T, a circulator and an umbrella antenna, and receives an ultra-wide bandwidth echo signal with a bandwidth of several GHz through the umbrella antenna, the circulator, a limiting low noise amplifier, a receiver and a signal processor, thereby realizing centimeter-level resolution imaging and having the advantage of ultra-high resolution.

[0014] During the working process of the present invention, transmission signals with different powers can be generated by configuring the value of the phase shifter, the number of power amplifiers involved in the work and the state of the waveguide switch, and the working mode is flexible and the reliability is good.

[0015] The invention has a simple composition and reduces the volume and weight of the product through centralized transmission and reception. It has the advantages of light weight and low heat consumption, and reduces the cost and difficulty of engineering development. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The present invention is a block diagram of the spaceborne ultra-high resolution SAR system.

[0017] Figure 2 This is a high-power signal flow diagram of the first working mode setting method 1 of the system of the present invention.

[0018] Figure 3 This is a high-power signal flow diagram of the first working mode setting method 2 of the system of the present invention.

[0019] Figure 4 This is a high-power signal flow diagram of the second working mode setting method of the system of the present invention.

[0020] Figure 5 This is a high-power signal flow diagram of the third working mode setting method 1 of the system of the present invention.

[0021] Figure 6 This is a high-power signal flow diagram of the third working mode setting method 2 of the system of the present invention.

[0022] Figure 7 This is a high-power signal flow diagram of the third working mode setting method 3 of the system of the present invention.

[0023] Figure 8 This is a high-power signal flow diagram of the third working mode setting method 4 of the system of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a spaceborne ultra-high resolution SAR system, such as Figure 1 , including: signal processor, frequency multiplication unit, synthesis network front end, traveling wave tube amplifier group, magic T, waveguide load, waveguide switch, circulator, umbrella antenna, frequency synthesizer, limited low noise amplifier and receiver; the signal processor transmits small and medium bandwidth intermediate frequency signal, and then the frequency multiplication unit expands the signal bandwidth to the required bandwidth; the signal reaches the input port of the traveling wave tube amplifier after power division and phase shifting at the synthesis network front end; the traveling wave tube amplifier completes the power amplification of the RF transmission signal, and its output signal enters the magic T to complete power synthesis; the waveguide switch selects different high-power transmission signals and sends the transmission signal to the circulator; the high-power transmission signal is transmitted from the umbrella antenna after passing through the circulator; the RF echo is received by the antenna, passes through the circulator to the limited low noise amplifier, and after low noise amplification, the RF echo enters the receiver, is filtered by the power division and down-converted to the receiving intermediate frequency, and finally the signal processor completes the echo data acquisition and packages it for output to the satellite platform. Among them, more specifically: The signal processor is used to generate intermediate frequency signals with small and medium bandwidths and send them to the frequency multiplication unit. At the same time, it collects multiple intermediate frequency echoes output by the receiver, and then frames the collected data for output. The signal processor also accepts external remote control to generate various control signals within the system and returns telemetry signals.

[0025] The frequency multiplication unit is used to multiply the intermediate frequency transmission signal with small or medium bandwidth to the required bandwidth range to meet the system resolution requirements.

[0026] The synthesis network front end can receive the RF signal output by the frequency multiplication unit and send it to four phase shifters for phase adjustment after power division.

[0027] The traveling wave tube amplifier group includes four traveling wave tube amplifiers and is used to complete the power amplification of the radio frequency signal.

[0028] The three magic Ts can combine the different signal phases controlled by the phase shifters to complete the power synthesis of high-power RF signals.

[0029] Three waveguide switches can realize the selective output of three high-power RF signals.

[0030] The three waveguide loads can absorb the leakage signal and ensure that the system has lower electromagnetic leakage.

[0031] The circulator is used to send the high-power transmission signal to the umbrella antenna, and then send the echo received by the umbrella antenna to the limited low-noise amplifier.

[0032] Umbrella antenna is used to radiate high-power radio frequency signals and receive ground echoes.

[0033] The frequency synthesizer is used to generate the clock required by the signal processor and the local oscillator signal required by the receiver.

[0034] The limiting low noise amplifier is used to withstand high-power leakage signals to prevent them from affecting subsequent electronic equipment, while also completing the amplification of low-power echo signals.

[0035] The receiver is used to divide the broadband echo signal into multiple paths. Each path selects the frequency band through a different filter, and then down-converts it to the required intermediate frequency and sends it to the signal processor for collection.

[0036] Specifically, the umbrella antenna is installed outside the satellite cabin and maneuvers in conjunction with the satellite platform during the imaging process to achieve large-angle scanning imaging of the target area.

[0037] The principle for selecting the number of power splitters inside the receiver is: let the system RF signal bandwidth divided by the signal processor acquisition rate and then multiplied by 2.4 to obtain the result M, and the number of power splitters N is the smallest integer greater than or equal to M.

[0038] The three magic Ts are magic T1, magic T2 and magic T3, and the four ports of magic T1, magic T2 and magic T3 are port 1, port 2, port 3 and port 4 respectively; the three waveguide switches are waveguide switch 1, waveguide switch 2 and waveguide switch 3, and the three waveguide loads are waveguide load 1, waveguide load 2 and waveguide load 3.

[0039] The four phase shifters are phase shifter 1, phase shifter 2, phase shifter 3 and phase shifter 4; the four traveling wave tube amplifiers are traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3 and traveling wave tube amplifier 4.

[0040] The system of the present invention has three working modes, each of which corresponds to different settings, including different phase shifter settings, the number of traveling wave tube amplifiers working, and waveguide switch settings; the working method flow in all working modes is: The signal processor generates an intermediate frequency signal with a small or medium bandwidth, the frequency multiplication unit completes the signal bandwidth expansion to generate the required bandwidth RF signal, the synthesis network front end completes the power division and phase shifting, the traveling wave tube amplifier group completes the power amplification, and the high-power signal is sent to the circulator through the magic T and waveguide switch selection, and reaches the umbrella antenna for radiation. The echo received by the umbrella antenna passes through the circulator and enters the limiting low-noise amplifier for amplification. The amplified echo is divided into multiple small and medium bandwidth echoes by the power divider and filter inside the receiver and down-converted to the intermediate frequency. Finally, the multi-channel analog-to-digital conversion is completed at the signal processor to convert it into data and output it in a frame.

[0041] In the first working mode, the transmission power is 2 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting correspond to the following two setting methods: Mode 1: TWT amplifiers 1 and 2 are working, phase shifter 1 is set to 0°, and phase shifter 2 is set to 180°; TWT amplifiers 3 and 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide switch 3, waveguide switch 2 is set so that the signal is connected from waveguide switch 3 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from waveguide switch 1 to circulator; at this time, the high-power transmission signal is output from port 4 of magic T1, passes through waveguide switch 1 and waveguide switch 3, reaches the circulator, and finally radiates from the umbrella antenna; Figure 2 shown.

[0042] Mode 2: TWT amplifier 1 and TWT amplifier 2 do not work; TWT amplifier 3 and TWT amplifier 4 work, phase shifter 3 is set to 0°, and phase shifter 4 is set to 180°; waveguide switch 1 is set so that the signal is connected from waveguide switch 3 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide switch 3, and waveguide switch 3 is set so that the signal is connected from waveguide switch 2 to circulator; at this time, the high-power transmission signal is output from port 4 of magic T2, reaches the circulator after passing through waveguide switch 2 and waveguide switch 3, and finally radiates from the umbrella antenna; Figure 3 shown.

[0043] In the second working mode, the transmission power is 4 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting method are: Traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3, and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 2 is set to 0°, phase shifter 3 is set to 0°, and phase shifter 4 is set to 0°; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T1 and magic T2, and after being synthesized by magic T3, it enters waveguide switch 3 and circulator, and finally radiates from the umbrella antenna; Figure 4 shown.

[0044] In the third working mode, the transmission power is 1 times the output power of the traveling wave tube amplifier; there are four corresponding settings for the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting: Mode 1: Traveling wave tube amplifier 1 and traveling wave tube amplifier 3 are working, phase shifter 1 is set to 0°, phase shifter 3 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Figure 5 .

[0045] Mode 2: Traveling wave tube amplifier 1 and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 4 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Figure 6 shown.

[0046] Mode 3: TWT amplifier 2 and TWT amplifier 3 are working, phase shifter 2 is set to 0°, and phase shifter 3 is set to 0°; TWT amplifier 1 and TWT amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Figure 7 shown.

[0047] Mode 4: TWT amplifier 2 and TWT amplifier 4 are working, phase shifter 2 is set to 0°, and phase shifter 4 is set to 0°; TWT amplifier 1 and TWT amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Figure 8 shown.

[0048] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0049] Example: This embodiment provides a spaceborne ultra-high resolution SAR system and a working method thereof. The method of the present invention is used to design and operate a spaceborne SAR with a resolution of 7.5 cm. The system operates in the Ku band, with an operating frequency range of 12.6 GHz to 17.4 GHz and a signal bandwidth of about 4.8 GHz. The specific implementation process is as follows: System like Figure 1 As shown, it includes: a signal processor, a frequency multiplication unit, a synthesis network front end, a traveling wave tube amplifier group, magic T1~3, waveguide loads 1~3, waveguide switches 1~3, a circulator, an umbrella antenna, a frequency synthesizer, a limiting low noise amplifier and a receiver.

[0050] The signal processor generates a small- to medium-bandwidth intermediate frequency signal with a frequency range of 2.1GHz to 2.9GHz and a bandwidth of 800MHz, which is sent to the frequency multiplication unit. At the same time, it collects and receives multiple intermediate frequency echoes at a rate of 4Gsps / channel, and then frames the collected data for output. The signal processor also accepts external remote control to generate various control signals within the system and returns telemetry signals.

[0051] The frequency multiplication unit multiplies the small-bandwidth intermediate frequency signal with a frequency range of 2.1GHz~2.9GHz and a bandwidth of 800MHz by 6 to the required operating frequency range of 12.6GHz~17.4GHz, which can meet the system resolution requirements.

[0052] The front end of the synthesis network receives the RF signal output by the frequency multiplication unit and sends it to four phase shifters for phase adjustment after power division.

[0053] The traveling wave tube amplifier group consists of four traveling wave tube amplifiers to complete the power amplification of the radio frequency signal.

[0054] Magic T 1~3 combines the different signal phases controlled by the aforementioned phase shifters to complete the power synthesis of high-power RF signals.

[0055] Waveguide switches 1 to 3 select and output three types of high-power radio frequency signals.

[0056] Waveguide loads 1 to 3 absorb the leakage signal to ensure that the system has low electromagnetic leakage.

[0057] The circulator sends the high-power transmission signal to the umbrella antenna, and then sends the echo received by the umbrella antenna to the limiting low-noise amplifier.

[0058] The umbrella antenna radiates high-power radio frequency signals and receives ground echoes.

[0059] The frequency synthesizer generates the clock required by the signal processor and the local oscillator signal required by the receiver.

[0060] The limiting low noise amplifier withstands high-power leakage signals to prevent them from affecting subsequent electronic equipment, while also completing the amplification of low-power echo signals.

[0061] The receiver divides the broadband echo signal into multiple paths, each of which is selected through a different filter to select the frequency band, and then down-converted to the required intermediate frequency and sent to the signal processor for acquisition.

[0062] The umbrella antenna is installed outside the satellite cabin and performs mobile scanning in conjunction with the satellite platform during imaging.

[0063] The principle for selecting the number of power splitters inside the receiver is: the system RF signal bandwidth of 4.8 GHz divided by the signal processor acquisition rate of 4 Gsps multiplied by 2.4 is 2.88, and the number of power splitters is 3.

[0064] In the second working mode setting of the system, the phase shifter setting, the number of working traveling wave tube amplifiers, and the waveguide switch setting are as follows: Traveling wave tube amplifiers 1, 2, 3, and 4 are working, phase shifter 1 is set to 0°, phase shifter 2 is set to 0°, phase shifter 3 is set to 0°, and phase shifter 4 is set to 0°; waveguide switches 1 to 3 are set according to Figure 4 At this time, the high-power transmission signal is output from port 3 of magic T1 and magic T2, synthesized by magic T3, enters waveguide switch 3 and circulator, and finally radiates from the umbrella antenna.

[0065] The above embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0066] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

[0067] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0069] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A spaceborne ultra-high resolution SAR system, characterized in that: include: Signal processor, frequency multiplication unit, synthesis network front end, traveling wave tube amplifier group, magic T, waveguide load, waveguide switch, circulator, umbrella antenna, frequency synthesizer, limiting low noise amplifier and receiver; among which: The signal processor is used to generate intermediate frequency signals with small and medium bandwidths and send them to the frequency multiplication unit. At the same time, it collects the multi-channel intermediate frequency echoes output by the receiver, and then frames the collected data for output. The signal processor also receives external remote control to generate various control signals within the system and returns telemetry signals. The frequency multiplication unit is used to multiply the intermediate frequency transmission signal with small or medium bandwidth to the required bandwidth range to meet the system resolution requirements; The synthesis network front end can receive the RF signal output by the frequency multiplication unit and send it to four phase shifters for phase adjustment after power division; A traveling wave tube amplifier group, including four traveling wave tube amplifiers, is used to complete the power amplification of the radio frequency signal; Three magic Ts can combine the different signal phases controlled by the phase shifters to complete the power synthesis of high-power RF signals; Three waveguide switches can realize the selective output of three high-power RF signals; Three waveguide loads can absorb leakage signals and ensure the system has low electromagnetic leakage; Circulator, used to send high-power transmission signal to the umbrella antenna, and then send the echo received by the umbrella antenna to the limited low-noise amplifier; Umbrella antenna, used to radiate high-power radio frequency signals and receive ground echoes; Frequency synthesizer, used to generate the clock required by the signal processor and the local oscillator signal required by the receiver; Limiting low noise amplifier, used to withstand high-power leakage signals to prevent them from affecting subsequent electronic equipment, while completing the amplification of low-power echo signals; The receiver is used to divide the broadband echo signal into multiple paths. Each path selects the frequency band through a different filter, and then down-converts it to the required intermediate frequency and sends it to the signal processor for collection.

2. The spaceborne ultra-high resolution SAR system according to claim 1, characterized in that: The umbrella antenna is installed outside the satellite cabin and maneuvers in conjunction with the satellite platform during the imaging process to achieve large-angle scanning imaging of the target area.

3. The spaceborne ultra-high resolution SAR system according to claim 1, characterized in that: The principle for selecting the number of power splitters inside the receiver is as follows: assume that the system RF signal bandwidth is divided by the signal processor acquisition rate and then multiplied by 2.4 to obtain a result M, and the number of power splitters N is the smallest integer greater than or equal to M.

4. The spaceborne ultra-high resolution SAR system according to claim 1, characterized in that: The three magic Ts are magic T1, magic T2 and magic T3, and the four ports of magic T1, magic T2 and magic T3 are port 1, port 2, port 3 and port 4 respectively; the three waveguide switches are waveguide switch 1, waveguide switch 2 and waveguide switch 3, and the three waveguide loads are waveguide load 1, waveguide load 2 and waveguide load 3.

5. The spaceborne ultra-high resolution SAR system according to claim 4, characterized in that: The four phase shifters are phase shifter 1, phase shifter 2, phase shifter 3 and phase shifter 4; the four traveling wave tube amplifiers are traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3 and traveling wave tube amplifier 4.

6. The operating method of the spaceborne ultra-high resolution SAR system according to claim 5, characterized in that: The system has three working modes, each of which corresponds to different settings, including phase shifter settings, number of traveling wave tube amplifiers, and waveguide switch settings; the working method flow in all working modes is: The signal processor generates an intermediate frequency signal with a small or medium bandwidth, the frequency multiplication unit completes signal bandwidth expansion to generate a radio frequency signal with a required bandwidth, the synthesis network front end completes power division and phase shifting, the traveling wave tube amplifier group completes power amplification, and the high-power signal is sent to the circulator through the selection of the magic T and waveguide switch, reaches the umbrella antenna and radiates out, and the echo received by the umbrella antenna enters the limiting low-noise amplifier after passing through the circulator for amplification. The amplified echo is divided into a plurality of small or medium bandwidth echoes by a power divider and a filter inside the receiver, and down-converted to the intermediate frequency, and finally the multi-channel analog-to-digital conversion is completed at the signal processor to become data and output in a frame.

7. The operating method of the spaceborne ultra-high resolution SAR system according to claim 6, characterized in that: In the first working mode, the transmission power is 2 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting correspond to the following two setting methods: Mode 1: TWT amplifiers 1 and 2 are working, phase shifter 1 is set to 0°, and phase shifter 2 is set to 180°; TWT amplifiers 3 and 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide switch 3, waveguide switch 2 is set so that the signal is connected from waveguide switch 3 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from waveguide switch 1 to circulator; at this time, the high-power transmission signal is output from port 4 of magic T1, passes through waveguide switch 1 and waveguide switch 3 to the circulator, and finally radiates from the umbrella antenna; Mode 2: TWT amplifier 1 and TWT amplifier 2 do not work; TWT amplifier 3 and TWT amplifier 4 work, phase shifter 3 is set to 0°, and phase shifter 4 is set to 180°; waveguide switch 1 is set so that the signal is connected from waveguide switch 3 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide switch 3, and waveguide switch 3 is set so that the signal is connected from waveguide switch 2 to the circulator; at this time, the high-power transmission signal is output from port 4 of magic T2, reaches the circulator after passing through waveguide switch 2 and waveguide switch 3, and finally radiates from the umbrella antenna.

8. The operating method of the spaceborne ultra-high resolution SAR system according to claim 6, characterized in that: In the second working mode, the transmission power is 4 times the output power of the traveling wave tube amplifier; the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting method are: Traveling wave tube amplifier 1, traveling wave tube amplifier 2, traveling wave tube amplifier 3, and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 2 is set to 0°, phase shifter 3 is set to 0°, and phase shifter 4 is set to 0°; waveguide switch 1 is set so that the signal is connected to waveguide load 1 from port 4 of magic T1, waveguide switch 2 is set so that the signal is connected to waveguide load 2 from port 4 of magic T2, and waveguide switch 3 is set so that the signal is connected to the circulator from port 3 of magic T3; at this time, the high-power transmission signal is output from port 3 of magic T1 and magic T2, and after being synthesized by magic T3, it enters waveguide switch 3 and circulator, and finally radiates from the umbrella antenna.

9. The operating method of the spaceborne ultra-high resolution SAR system according to claim 6, characterized in that: In the third working mode, the transmission power is 1 times the output power of the traveling wave tube amplifier; there are four corresponding settings for the phase shifter setting, the number of traveling wave tube amplifiers working, and the waveguide switch setting: Mode 1: Traveling wave tube amplifier 1 and traveling wave tube amplifier 3 are working, phase shifter 1 is set to 0°, and phase shifter 3 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 2: Traveling wave tube amplifier 1 and traveling wave tube amplifier 4 are working, phase shifter 1 is set to 0°, phase shifter 4 is set to 0°; traveling wave tube amplifier 2 and traveling wave tube amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 3: TWT amplifier 2 and TWT amplifier 3 are working, phase shifter 2 is set to 0°, and phase shifter 3 is set to 0°; TWT amplifier 1 and TWT amplifier 4 are not working; waveguide switch 1 is set so that the signal is connected from port 4 of magic T1 to waveguide load 1, waveguide switch 2 is set so that the signal is connected from port 4 of magic T2 to waveguide load 2, and waveguide switch 3 is set so that the signal is connected from port 3 of magic T3 to circulator; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna; Mode 4: TWT amplifier 2 and TWT amplifier 4 are working, phase shifter 2 is set to 0°, and phase shifter 4 is set to 0°; TWT amplifier 1 and TWT amplifier 3 are not working; waveguide switch 1 is set so that the signal is connected to waveguide load 1 from port 4 of magic T1, waveguide switch 2 is set so that the signal is connected to waveguide load 2 from port 4 of magic T2, and waveguide switch 3 is set so that the signal is connected to the circulator from port 3 of magic T3; at this time, the high-power transmission signal is output from port 3 of magic T3, reaches the circulator after passing through waveguide switch 3, and finally radiates from the umbrella antenna.

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