A multi-beam spaceborne SAR system based on serial sub-band synthesis

Abstract

The invention discloses a multi-beam satellite-borne SAR system based on serial sub-band synthesis, including a signal processor, a frequency source, a multi-sub-band upconverter, a beamforming network, a power amplifier group, a circulator group, a multi-channel limited low noise amplifier, a multi-sub-band downconverter, a power distribution unit and a multi-beam reflector antenna; the multi-sub-band upconverter generates a radio frequency sub-band signal to be transmitted serially, and the multi-sub-band downconverter amplifies the sub-band signal after low noise amplification and down-converts it to an intermediate frequency signal; the beamforming network realizes the combination of different beams, and selects the corresponding power amplifier to output a high-power signal to a multi-beam feed source, and then obtains the required high gain through a reflector to meet the power aperture product required for high resolution. The invention solves the problems of achieving ultra-wideband and wide bandwidth in achieving high resolution at the centimeter level, has excellent signal quality, and has the advantages of light weight, low power consumption and low heat consumption, reducing the cost and difficulty of engineering development.

Description

Technical Field

[0001] The invention belongs to the field of spaceborne high-resolution SAR imaging, relates to a multi-beam spaceborne SAR system based on serial sub-band synthesis, and also relates to a high-resolution and wide-band implementation method of the spaceborne high-resolution SAR system. Background Art

[0002] The satellite-borne high-resolution SAR system can realize ground imaging. The imaging resolution is independent of distance and can reach centimeter level. The operation is not affected by lighting conditions. This application fills the gap in centimeter-level resolution imaging.

[0003] The operating orbit altitude of the high-resolution spaceborne SAR system is over hundreds of kilometers. The system has a centimeter-level resolution and a swath width of over ten kilometers. Therefore, the system signal bandwidth requirements are very high, with a relative bandwidth of over 30%. New technical methods must be considered to achieve high resolution and wide mapping swaths.

[0004] Regarding the publicly available implementation methods of high-resolution spaceborne SAR systems at home and abroad, the public information is limited to the signal processing method of sub-band splicing, and does not involve the implementation of the radar system, and cannot solve the system problems faced by high-resolution SAR. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a multi-beam spaceborne SAR system based on serial sub-band synthesis to solve the problems of achieving ultra-wideband and wide bandwidth when achieving centimeter-level high resolution on board space. The system is of great significance for high-resolution observation of the Earth.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0007] A multi-beam spaceborne SAR system based on serial sub-band synthesis includes a signal processor, a frequency source, a multi-sub-band up-converter, a beamforming network, a power amplifier group, a circulator group, a multi-channel limiting low noise amplifier, a multi-sub-band down-converter, a power distribution unit and a multi-beam reflector antenna; wherein:

[0008] A signal processor is used to generate an intermediate frequency transmission signal under the control of the communication interface and send it to the multi-sub-band up-converter, and to perform multi-channel sampling on the intermediate frequency receiving signal from the multi-sub-band down-converter, and output the sampled data through the data transmission interface;

[0009] A multi-sub-band upconverter is used to up-convert the intermediate frequency transmission signal to generate the radio frequency transmission signal required by each sub-band and output it to the beamforming network;

[0010] A beam forming network is used to gate, phase shift and attenuate the RF transmission signal and output it to the power amplifier group;

[0011] A power amplifier group is used to amplify a low-power radio frequency transmission signal to a required power and output a high-power radio frequency transmission signal;

[0012] A circulator group is used to send a high-power radio frequency transmission signal to a multi-beam reflector antenna, and then send the echo signal received by the multi-beam reflector antenna to a multi-channel limiting low noise amplifier;

[0013] Multi-channel limiting low noise amplifier, used to limit the high-power signal leaked from the antenna during transmission, protect the receiving path, and amplify the echo signal received by the antenna;

[0014] A multi-sub-band down-converter is used to perform signal conditioning and down-conversion to an intermediate frequency signal on the signal amplified by the limiting low noise amplifier group, thereby forming a multi-sub-band receiving signal and outputting it to a signal processor;

[0015] The multi-beam reflector antenna includes a multi-beam feed array and a reflector. The multi-path high-power RF transmission signals sent by the circulator are irradiated onto the reflector through multiple feeds to form multiple transmission beams; the echoes from multiple areas enter different feeds through the reflector to form multiple receiving beams, and the received echoes are sent to the circulator group.

[0016] The present invention also includes the following technical features:

[0017] Specifically, the system further includes a frequency source, which can generate a clock required by the signal processor and a local oscillator signal required by the multi-sub-band up-converter and the multi-sub-band down-converter.

[0018] Specifically, the system also includes a power distribution unit, which is used to receive a primary power supply input to provide power for a signal processor, a frequency source, a multi-sub-band up-converter, a power amplifier group, a multi-channel limiting low noise amplifier and a multi-sub-band down-converter.

[0019] Specifically, the system is installed on an agile mobile satellite platform to achieve two-dimensional high-resolution imaging of ground targets.

[0020] Specifically, the multi-subband upconverter upconverts the intermediate frequency transmission signal generated by the signal processor in sequence according to the designed subband signal timing to achieve serial transmission, thereby obtaining a multi-subband signal; the transmission timing of the multi-subband signal is to transmit the odd subbands first and then the even subbands.

[0021] Specifically, the number of the multiple sub-band signals and the bandwidth and starting frequency of each sub-band signal are determined according to the following criteria:

[0022] Number of multi-subband signals is greater than The smallest integer of is the total signal bandwidth required by the system, is the maximum bandwidth that can be achieved by the intermediate frequency transmission signal; the bandwidth of each sub-band signal is ;No. The starting frequency of the subband signal is ,in The lowest frequency of the RF signal transmitted by the system.

[0023] Specifically, the number of feed sources of the multi-beam reflector antenna is is greater than The smallest integer of which is the width required by the system, is the width that a single beam can cover; the number of power amplifiers in the power amplifier group, the number of circulators in the circulator group, the number of channels in the multi-channel limiting low noise amplifier, and the number of multi-subband down converters are all equal to .

[0024] Specifically, the multi-subband signals transmitted in series are irradiated to the ground and then returned to the antenna. After being received by different feed sources, they pass through the circulator group, multi-channel limiting low noise amplifier and multi-subband down converter to reach the signal processor. Each multi-subband down converter outputs The signal processor needs to simultaneously The intermediate frequency receiving signal is sampled at high speed.

[0025] Specifically, after the system transmits and receives the multi-subband signals in series, the system performs sub-band synthesis through digital signal processing in the signal processor to obtain a synthesized large-bandwidth signal to meet the bandwidth requirements of the system.

[0026] The working method of the multi-beam spaceborne SAR system based on serial sub-band synthesis comprises the following steps:

[0027] Step 1, first provide a primary power supply input to the power distribution unit, so that the signal processor, frequency source, multi-sub-band up-converter, power amplifier group, multi-channel limiting low noise amplifier and multi-sub-band down-converter in the system are powered on and work;

[0028] Step 2, controlling the signal processor to transmit an intermediate frequency transmission signal through the communication interface;

[0029] Step 3, the intermediate frequency signal generated by the signal processor is output to the multi-sub-band up-converter, and the multi-sub-band up-converter transmits the multi-sub-band signal in series under the control of the signal processor;

[0030] Step 4: The multi-subband transmission signal reaches the beamforming network, where it is controlled by the signal processor to complete gating, phase shifting and attenuation, and then completes power amplification in the power amplifier group, and finally passes through the circulator group to enter the feed array of the multi-beam reflector antenna, and is amplified and transmitted through the reflector;

[0031] Step 5, the signal transmitted by the multi-beam reflector antenna is received by the ground after being scattered by the ground; the received signal is output to the multi-channel limiting low noise amplifier through the circulator group, and then converted to an intermediate frequency signal through a multi-subband downconverter, and the output intermediate frequency signal is sent to the signal processor for digital processing.

[0032] Compared with the prior art, the present invention has the following technical effects:

[0033] The present invention utilizes a SAR radar system with simultaneous multi-beam and sub-band synthesis to solve the problems of achieving ultra-wideband and wide bandwidth when satellite-borne high resolution reaches the centimeter level. Through centralized transmission and reception, the volume and weight of the product are reduced, and the signal quality is excellent. At the same time, it has the advantages of light weight, low power consumption, and low heat consumption, thereby reducing the cost and difficulty of engineering development. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of a multi-beam spaceborne SAR system based on serial sub-band synthesis of the present invention.

[0035] Figure 2 Schematic diagram of a multi-subband upconverter of the present invention.

[0036] Figure 3 It is a schematic diagram of serial sub-band transmission of the present invention.

[0037] Figure 4 Schematic diagram of a multi-sub-band down converter of the present invention.

[0038] Figure 5 It is a schematic diagram of the beamforming network generating multiple beams according to the present invention. DETAILED DESCRIPTION

[0039] Aiming at the design difficulties of centimeter-level resolution satellite-borne high-resolution SAR system, especially when the resolution reaches centimeter level and the relative bandwidth reaches more than 30%, the present invention proposes a radar system combining serial sub-band synthesis and multi-beam, whose system imaging resolution can reach centimeter level, the effective range is more than hundreds of kilometers, and has excellent signal quality. At the same time, it has the advantages of light weight, low power consumption and low heat consumption, which reduces the cost and difficulty of engineering development. At present, this technology has been successfully applied to satellite-borne high-resolution SAR system.

[0040] The specific implementation of the present invention is further described below with reference to the accompanying drawings.

[0041] The present invention provides a multi-beam spaceborne SAR system based on serial sub-band synthesis, such as Figure 1As shown, it includes: a signal processor, a frequency source, a multi-sub-band up-converter, a beam forming network, a power amplifier group, a circulator group, a multi-channel limiting low noise amplifier, a multi-sub-band down-converter, a power distribution unit and a multi-beam reflector antenna; wherein:

[0042] The signal processor is used to generate an intermediate frequency transmission signal under the control of the communication interface and send it to the multi-sub-band up-converter, and perform multi-channel sampling on the intermediate frequency receiving signal from the multi-sub-band down-converter. The data obtained after sampling is output through the data transmission interface.

[0043] The multi-sub-band up-converter is used to up-convert the intermediate frequency transmission signal to generate the radio frequency transmission signal required by each sub-band and output it to the beamforming network.

[0044] The beamforming network is used to select, phase shift and attenuate the RF transmission signal and output it to the power amplifier group.

[0045] The power amplifier group is used to amplify the low-power RF transmission signal to the required power and output a high-power RF transmission signal.

[0046] The circulator group is used to send the high-power RF transmission signal to the multi-beam reflector antenna, and then send the echo signal received by the multi-beam reflector antenna to the multi-channel limiting low noise amplifier.

[0047] The multi-channel limiting low noise amplifier is used to limit the high-power signal leaked from the antenna during transmission, protect the receiving path, and amplify the echo signal received by the antenna.

[0048] The multi-sub-band down-converter is used to perform signal conditioning and down-conversion to an intermediate frequency signal on the signal amplified by the limiting low noise amplifier group, thereby forming a multi-sub-band receiving signal and outputting it to the signal processor.

[0049] The multi-beam reflector antenna includes a multi-beam feed array and a reflector. The multi-path high-power RF transmission signals sent by the circulator are irradiated onto the reflector through multiple feeds to form multiple transmission beams; the echoes from multiple areas enter different feeds through the reflector to form multiple receiving beams, and the received echoes are sent to the circulator group.

[0050] The frequency source generates the clock required by the signal processor and the local oscillator signal required by the multi-sub-band up-converter and the multi-sub-band down-converter.

[0051] The power distribution unit receives a primary power supply input and provides power for the signal processor, the frequency source, the multi-sub-band up-converter, the power amplifier group, the multi-channel limiting low noise amplifier and the multi-sub-band down-converter.

[0052] The system is installed on an agile mobile satellite platform to achieve two-dimensional high-resolution imaging of ground targets.

[0053] As Figure 2 shown, the multi-subband upconverter upconverts the intermediate-frequency transmission signal generated by the signal processor in sequence according to the designed subband signal timing to achieve serial transmission, and obtains a multi-subband signal; as Figure 3 shown, the transmission timing of the multi-subband signal is to transmit the odd subbands first and then the even subbands.

[0054] The number of multi-subband signals, the bandwidth and starting frequency of each subband signal are determined according to the following criteria:

[0055] The number of multi-subband signals is the smallest integer greater than , where is the total signal bandwidth required by the system, is the maximum bandwidth that the intermediate-frequency transmission signal can achieve; the bandwidth of each subband signal is ; the starting frequency of the rd subband signal is , where is the lowest frequency of the radio frequency signal transmitted by the system.

[0056] Specifically, in this embodiment, the bandwidth required by the system is 2300 MHz, the maximum bandwidth that the intermediate-frequency transmission signal can achieve is 600 MHz, and the lowest frequency of the radio frequency signal transmitted by the system is 8600 MHz. Then the number of multi-subband signals is 5; the bandwidth of each subband signal is 500 MHz; the starting frequencies of the 5 subband signals are 8600 MHz, 9050 MHz, 9500 MHz, 9950 MHz, and 10400 MHz in sequence.

[0057] The number of feeds of the multi-beam reflector antenna is the smallest integer greater than , where is the beam width required by the system, is the beam width that a single beam can cover; the number of power amplifiers in the power amplifier group, the number of circulators in the circulator group, the number of channels in the multi-channel limiting low-noise amplifier, and the number of multi-subband downconverters are all equal to .

[0058] Specifically, in this embodiment, the beam width required by the system is 10 km, the beam width that a single beam can cover is 3 km, the number of feeds of the multi-beam reflector antenna is 4; the number of power amplifiers in the power amplifier group, the number of circulators in the circulator group, the number of channels in the multi-channel limiting low-noise amplifier, and the number of multi-subband downconverters are all equal to 4.

[0059] The serially transmitted multi-subband signal irradiates the ground and returns to the antenna. After being received by different feed sources, it passes through the circulator group, multi-channel limiting low noise amplifier and multi-subband down converter to reach the signal processor. Each multi-subband down converter outputs The signal processor needs to simultaneously receive the intermediate frequency signal. The intermediate frequency receiving signal is sampled at high speed.

[0060] Specifically, in this embodiment, if Figure 4 As shown, each multi-sub-band down-converter outputs 5 intermediate frequency receiving signals, and the signal processor needs to perform high-speed sampling on 20 intermediate frequency receiving signals at the same time.

[0061] After the system transmits and receives the multi-subband signals in serial, it performs sub-band synthesis in the signal processor through digital signal processing to obtain a synthesized large-bandwidth signal to meet the system bandwidth requirement of 2600MHz.

[0062] The working method of the multi-beam spaceborne SAR system based on serial sub-band synthesis of the present invention comprises the following steps:

[0063] Step 1, first provide a primary power supply input to the power distribution unit, so that the signal processor, frequency source, multi-sub-band up-converter, power amplifier group, multi-channel limiting low noise amplifier and multi-sub-band down-converter in the system are powered on and work;

[0064] Step 2, controlling the signal processor to transmit an intermediate frequency transmission signal through the communication interface;

[0065] Step 3, the intermediate frequency signal generated by the signal processor is output to the multi-sub-band up-converter, and the multi-sub-band up-converter transmits the multi-sub-band signal in series under the control of the signal processor;

[0066] Step 4, such as Figure 5 As shown, the multi-subband transmission signal reaches the beamforming network, where it is controlled by the signal processor to complete gating, phase shifting and attenuation, and then completes power amplification in the power amplifier group, and finally passes through the circulator group to enter the feed array of the multi-beam reflector antenna, and is amplified and transmitted through the reflector;

[0067] Step 5, the signal transmitted by the multi-beam reflector antenna is received by the ground after being scattered by the ground; the received signal is output to the multi-channel limiting low noise amplifier through the circulator group, and then converted to an intermediate frequency signal through a multi-subband downconverter, and the output intermediate frequency signal is sent to the signal processor for digital processing.

[0068] The present invention can be extended to high-resolution airborne SAR applications and high-resolution imaging radars for space targets.

[0069] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

[0070] 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.

[0071] 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.

[0072] 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 multi-beam spaceborne SAR system based on serial sub-band synthesis, characterized in that: It includes a signal processor, a frequency source, a multi-sub-band up-converter, a beamforming network, a power amplifier group, a circulator group, a multi-channel limiting low noise amplifier, a multi-sub-band down-converter, a power distribution unit and a multi-beam reflector antenna; wherein: A signal processor is used to generate an intermediate frequency transmission signal under the control of the communication interface and send it to the multi-sub-band up-converter, and to perform multi-channel sampling on the intermediate frequency receiving signal from the multi-sub-band down-converter, and output the sampled data through the data transmission interface; A multi-sub-band upconverter is used to up-convert the intermediate frequency transmission signal to generate the radio frequency transmission signal required by each sub-band and output it to the beamforming network; A beam forming network is used to gate, phase shift and attenuate the RF transmission signal and output it to the power amplifier group; A power amplifier group is used to amplify a low-power radio frequency transmission signal to a required power and output a high-power radio frequency transmission signal; A circulator group is used to send a high-power radio frequency transmission signal to a multi-beam reflector antenna, and then send the echo signal received by the multi-beam reflector antenna to a multi-channel limiting low noise amplifier; Multi-channel limiting low noise amplifier, used to limit the high-power signal leaked from the antenna during transmission, protect the receiving path, and amplify the echo signal received by the antenna; A multi-sub-band down-converter is used to perform signal conditioning and down-conversion to an intermediate frequency signal on the signal amplified by the limiting low noise amplifier group, thereby forming a multi-sub-band receiving signal and outputting it to a signal processor; The multi-beam reflector antenna includes a multi-beam feed array and a reflector. The multi-channel high-power radio frequency transmission signals sent by the circulator are irradiated onto the reflector through multiple feeds to form multiple transmission beams. The echoes from multiple regions enter different feeds through the reflector to form multiple receiving beams, and the received echoes are sent to the circulator group. The multi-subband up-converter sequentially up-converts the intermediate frequency transmission signal generated by the signal processor according to the designed sub-band signal timing to realize serial transmission, thereby obtaining a multi-sub-band signal; the transmission timing of the multi-sub-band signal is to transmit the odd sub-bands first and then the even sub-bands; The number of the multi-subband signals and the bandwidth and starting frequency of each subband signal are determined according to the following criteria: Number of multi-subband signals is greater than The smallest integer of is the total signal bandwidth required by the system, is the maximum bandwidth that can be achieved by the intermediate frequency transmission signal; the bandwidth of each sub-band signal is ;No. The starting frequency of the subband signal is ,in The lowest frequency of the RF signal transmitted by the system.

2. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 1, characterized in that: The system also includes a frequency source, which can generate a clock required by the signal processor and a local oscillator signal required by the multi-sub-band up-converter and the multi-sub-band down-converter.

3. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 2, characterized in that: The system also includes a power distribution unit, which is used for receiving a primary power supply input and providing power to a signal processor, a frequency source, a multi-sub-band up-converter, a power amplifier group, a multi-channel limiting low noise amplifier and a multi-sub-band down-converter.

4. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 1, characterized in that: The system is installed on an agile mobile satellite platform to achieve two-dimensional high-resolution imaging of ground targets.

5. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 1, characterized in that: Number of feed sources of the multi-beam reflector antenna is greater than The smallest integer of is the width required by the system, is the width covered by a single beam; the number of power amplifiers in the power amplifier group, the number of circulators in the circulator group, the number of channels in the multi-channel limiting low noise amplifier, and the number of multi-subband down converters are all equal to .

6. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 5, characterized in that: The serially transmitted multi-subband signal irradiates the ground and returns to the antenna. After being received by different feed sources, it passes through the circulator group, multi-channel limiting low noise amplifier and multi-subband down converter to reach the signal processor. Each multi-subband down converter outputs The signal processor needs to simultaneously The intermediate frequency receiving signal is sampled at high speed.

7. The multi-beam spaceborne SAR system based on serial sub-band synthesis as claimed in claim 1, characterized in that: After the system transmits and receives the multi-subband signals in serial, it performs sub-band synthesis through digital signal processing in the signal processor to obtain a synthesized large-bandwidth signal to meet the bandwidth requirements of the system.

8. A working method of a multi-beam spaceborne SAR system based on serial sub-band synthesis according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, first provide a primary power supply input to the power distribution unit, so that the signal processor, frequency source, multi-sub-band up-converter, power amplifier group, multi-channel limiting low noise amplifier and multi-sub-band down-converter in the system are powered on and work; Step 2, controlling the signal processor to transmit an intermediate frequency transmission signal through the communication interface; Step 3, the intermediate frequency signal generated by the signal processor is output to the multi-sub-band up-converter, and the multi-sub-band up-converter transmits the multi-sub-band signal in series under the control of the signal processor; Step 4: The multi-subband transmission signal reaches the beamforming network, where it is controlled by the signal processor to complete gating, phase shifting and attenuation, and then completes power amplification in the power amplifier group, and finally passes through the circulator group to enter the feed array of the multi-beam reflector antenna, and is amplified and transmitted through the reflector; Step 5, the signal transmitted by the multi-beam reflector antenna is received by the ground after being scattered by the ground; the received signal is output to the multi-channel limiting low noise amplifier through the circulator group, and then converted to an intermediate frequency signal through a multi-subband downconverter, and the output intermediate frequency signal is sent to the signal processor for digital processing.

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