A light and small super-high-resolution wide-width spaceborne SAR system

Abstract

The application discloses a light and small super-high resolution wide-width spaceborne SAR system, which comprises a signal processor, a frequency synthesizer, a transmitting channel, a multi-channel receiving channel, a multi-channel internal scaler, a power supply and distribution unit, a beam forming network, a phased array feed and a parasol reflector; the light and small parasol reflector antenna combined with the phased array feed is used in a multi-channel multi-beam receiving mode to realize beam scanning receiving in the distance direction; and the whole surveying and mapping band is covered by switching different channels to receive. The system has the advantages of light weight, small size, low power consumption and low heat consumption, the imaging resolution can reach the centimeter level, the action distance is in the kilometer level, and the system has great significance for high-resolution earth observation.

Description

Technical Field

[0001] This invention belongs to the field of spaceborne high-resolution SAR imaging and relates to a spaceborne ultra-high resolution wide-swath lightweight SAR system. Background Technology

[0002] The spaceborne high-resolution wide-swath SAR system can achieve ground imaging with a resolution independent of distance, reaching the centimeter level, corresponding to a swath width of more than ten kilometers. It fills the gap in ultra-high resolution wide-swath SAR imaging in terms of application, and is also easy to miniaturize.

[0003] When the resolution reaches the centimeter level and the corresponding swath width is more than ten kilometers, the requirements for antenna gain, power and system bandwidth are relatively high. The implementation of the entire SAR system is very difficult, complex and large-scale. To reduce the implementation cost, new technical routes must be found.

[0004] A survey of publicly available information on the implementation methods of lightweight, high-resolution, wide-swath spaceborne SAR systems, both domestically and internationally, revealed that the available information was limited to signal processing methods and did not cover the specific implementation of the radar system, thus failing to solve the problem of miniaturized ultra-high-resolution wide-swath SAR. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a lightweight, ultra-high resolution, wide-swath spaceborne SAR system. This system addresses the challenges of achieving centimeter-level high resolution and wide swath width in lightweight, compact spaceborne SAR systems. The system weighs less than 100 kilograms, achieves centimeter-level imaging resolution, and has an operating range of thousands of kilometers. This system is of great significance for high-resolution Earth observation.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A lightweight, ultra-high resolution, wide-swath spaceborne SAR system includes a signal processor, a frequency synthesizer, a transmit channel, multiple receive channels, multiple internal scalers, a power supply and distribution unit, a beamforming network, a phased array feed, and an umbrella-shaped reflector. The signal processor receives instructions from the satellite through a communication interface, can output intermediate frequency signals to the transmission channel, can send control signals to the beamforming network, and can also sample the received echo signals. The transmit channel is used to upconvert the intermediate frequency signal generated by the signal processor to produce the ultra-wideband radio frequency signal required for high resolution, and output it to the beamforming network. The multi-channel receiving system is used to amplify, filter, and down-convert radar echo signals that have passed through the beamforming network to intermediate frequency signals, forming multiple receiving signals, which are then output to the signal processor. The beamforming network is used to receive control signals from the signal processor, perform power division, phase shifting, and power amplification on the signals from the transmit channel, and then output them to the phased array feed. At the same time, it couples out signals for calibration. It amplifies, phase shifts, and attenuates the multiple signals received by the phased array feed and then outputs them to multiple receive channels. It can also couple calibration signals from multiple calibrators into the receive path. A phased array feed is used to radiate a high-power signal emitted by the beamforming network onto an umbrella reflector, and then send the echo received by the umbrella reflector to the beamforming network. Umbrella-shaped reflectors are used to transmit high-power signals radiated by the phased array feed to the ground, and then gather the echoes from the ground and feed them back into the phased array feed. The multi-channel internal calibrator connects the transmit channel, beamforming network, and multiple receive channels to form the three required calibration paths. The frequency synthesizer is used to generate the working clock and send it to the signal processor, and to generate the local oscillator signal required for radar frequency conversion and send it to the transmitting channel and multiple receiving channels. The power supply and distribution unit is used to provide power to all active units.

[0008] The present invention also includes the following technical features: Specifically, the signal processor is connected to the intermediate frequency input port of the transmitting channel via the intermediate frequency output port. It generates the timing sequence and intermediate frequency signal required for the upconversion of the transmitting channel through the internal signal generation unit, outputs the intermediate frequency signal to the transmitting channel, and calculates the required beamwidth and number of beams according to the SAR working coverage distance range. It generates corresponding control signals through the internal beam control unit and sends them to the beamforming network. The multi-channel sampling unit samples the received echo signal and completes the scanning reception through weighted calculation to obtain a high antenna receiving gain.

[0009] Specifically, the three calibration paths formed by the multi-channel internal calibrator are as follows: the signal from the transmit channel is divided and sent to the beamforming network, which is the receive calibration path; the signal from the beamforming network is sent to the multiple receive channels, which is the transmit calibration path; and the signal from the transmit channel is divided and sent to the multiple receive channels, which is the reference calibration path. The switching of each switch inside the multi-channel internal calibrator is controlled by the signal processor.

[0010] Specifically, the power supply and distribution unit is connected to the signal processor, frequency synthesizer, transmit channel, multiple receive channel, multiple internal scaler, beamforming network and phased array feed via power supply interfaces through power supply lines.

[0011] Specifically, the system is installed on a spaceborne motion platform to achieve two-dimensional high-resolution imaging of ground targets, and the system has the characteristics of high resolution and wide swath.

[0012] The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system is as follows: During system operation, the intermediate frequency (IF) and signal bandwidth are designed based on the SAR operating frequency band and required signal bandwidth. The signal is then up-converted to radio frequency (RF) via the transmit channel to generate the required ultra-wideband signal. This signal is then processed by a beamforming network to form the required transmit signal, which is output to the phased array feed. After passing through an umbrella reflector, the wide-beam signal is transmitted. Upon reaching the illuminated target, the signal is backscattered and returns to the umbrella reflector. The umbrella reflector focuses the echo back onto the phased array feed, which then enters the beamforming network. In the beamforming network, the signal is amplified, phase-shifted, attenuated, and synthesized. The four received signals output from the beamforming network are down-converted into multiple receive channels. Multiple IF signals are simultaneously output to a signal processor. The processor simultaneously acquires data from multiple channels according to the designed receive gate, and then performs weighted synthesis of the multiple received data in the data domain to form the desired directional narrow beam.

[0013] Specifically, the multiple high-power signals transmitted by the phased array feed need to be reflected by the umbrella-shaped reflector before they can be transmitted as a wide beam.

[0014] Specifically, when receiving multiple narrow beams, the signal backscattered from the ground needs to be reflected by an umbrella reflector before entering the phased array feed, and then received through the subsequent receiving path.

[0015] Specifically, when receiving signals, multiple sets of weighting coefficients are received simultaneously within the signal processor to form multiple narrow receiving beams. Each receiving beam receives a portion of the signal width separately, thereby maximizing the receiving gain.

[0016] Specifically, in the beamforming network, power amplifiers N_1, N_2, and N_3 are grouped into power amplifier group 1, with different output powers. They are controlled by the signal processor, which selects one of the three power amplifiers to output to the phased array feed N. The total number of power amplifiers is three times the number of phased array feed sources; the first output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_1, power amplifier 2_1, ... is equal to the output power of power amplifier N_1; the second output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_2, power amplifier 2_2, ... is equal to the output power of power amplifier N_2; the third output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_3, power amplifier 2_3, ... is equal to the output power of power amplifier N_3.

[0017] Compared with the prior art, the present invention has the following technical effects: This invention utilizes a phased array feed-based umbrella-shaped reflector antenna SAR system, solving the problem of achieving high resolution and wide swath in spaceborne lightweight high-resolution SAR. By using phased array feed for transmission and reception, and an umbrella-shaped reflector antenna, the size and weight of the product are reduced, while maintaining excellent signal quality. It also has the advantages of being lightweight, having low power consumption, and low heat dissipation, thus reducing engineering development costs and difficulties. Attached Figure Description

[0018] Figure 1 This is a block diagram of the composition of the spaceborne ultra-high resolution wide-swath lightweight SAR system of the present invention.

[0019] Figure 2 This is a block diagram of the beamforming network of the present invention.

[0020] Figure 3 This is a block diagram of the multi-channel calibrator of the present invention.

[0021] Figure 4 This is a schematic diagram of multiple narrow beams formed inside the signal processor of the present invention. Detailed Implementation

[0022] This invention provides a lightweight, ultra-high resolution, wide-swath spaceborne SAR system. To achieve lightweight, ultra-high resolution, and wide-swath imaging, a lightweight umbrella-shaped reflector antenna combined with a phased array feed is proposed. Multi-channel, multi-beam reception is used to achieve range-direction beam scanning reception. Since the beams of different channels point to different range-direction mapping swathes, full mapping swathe coverage can be achieved by switching between different channels. This system has advantages such as light weight, small size, and strong engineering feasibility. This technology has already been applied to spaceborne high-resolution SAR systems.

[0023] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0024] Example: This embodiment provides a lightweight, ultra-high resolution, wide-swath spaceborne SAR system, including a signal processor, frequency synthesizer, transmit channel, multiple receive channels, multiple internal scalers, power supply and distribution unit, beamforming network, phased array feed, and umbrella reflector, such as Figure 1 As shown.

[0025] Signal processor: Connected to the intermediate frequency (IF) input port of the transmitting channel via the IF output port, the signal processor receives instructions from the satellite through the communication interface. It generates the timing required for upconversion and the IF broadband signal for the transmitting channel through its internal signal generation unit, outputs the IF signal to the transmitting channel, and calculates the required beamwidth and number of beams based on the SAR operating coverage distance. It generates corresponding control signals through its internal beam control unit and sends them to the beamforming network. The multi-channel sampling unit samples the received echo signals and performs weighted calculations to complete the scanning reception, thereby obtaining high antenna receiving gain.

[0026] Transmit channel: Upconverts the intermediate frequency signal generated by the signal processor to produce the ultra-wideband radio frequency signal required for high resolution, and outputs it to the beamforming network.

[0027] Multiple receiving channels: The radar echo signal passing through the beamforming network is amplified, filtered, and down-converted to an intermediate frequency signal to form multiple receiving signals, which are then output to the signal processor.

[0028] Beamforming network: It receives control signals from the signal processor, performs power division, phase shifting, and power amplification on signals from the transmit channel, and then outputs them to the phased array feed. Simultaneously, it couples out signals for calibration. It amplifies, phase-shifts, and attenuates multiple signals received from the phased array feed, and then outputs them to multiple receive channels. It can also couple calibration signals from multiple calibrators into the receive path. Its composition is as follows: Figure 2 As shown.

[0029] Phased array feed: The high-power signal emitted by the beamforming network is radiated onto the umbrella-shaped reflector, and then the echo received by the umbrella-shaped reflector is sent to the beamforming network.

[0030] Umbrella-shaped reflector: It transmits the high-power signal radiated by the phased array feed to the ground, and then focuses the echo from the ground back into the phased array feed.

[0031] The power supply and distribution unit provides various power supplies for all active units and connects to the signal processor, frequency synthesizer, transmit channel, multiple receive channel, multiple internal scaler, beamforming network and phased array feed via power supply interfaces.

[0032] The multi-channel internal calibrator connects the transmit channel, beamforming network, and multiple receive channels, forming the three calibration paths required by the system. It divides the signal from the transmit channel and sends it to the beamforming network (receive calibration path); it sends the signal from the beamforming network to the multiple receive channels (transmit calibration path); and it divides the signal from the transmit channel and sends it to the multiple receive channels (reference calibration path). The switching of its internal switches is controlled by a signal processor, forming a structure as follows: Figure 3 As shown.

[0033] Frequency synthesizer: generates the working clock and sends it to the signal processor, and generates the local oscillator signal required for radar frequency conversion and sends it to the transmitting channel and multiple receiving channels.

[0034] During system operation, the intermediate frequency (IF) and signal bandwidth are designed based on the SAR operating frequency band and required signal bandwidth. The signal is then up-converted to radio frequency (RF) via the transmit channel to generate the required ultra-wideband signal. This signal is then processed by a beamforming network to form the desired transmit signal, which is output to the phased array feed. After passing through an umbrella reflector, the signal is transmitted as a wide beam. Upon reaching the illuminated target, the signal is backscattered and returns to the umbrella reflector. The umbrella reflector focuses the echo back onto the phased array feed, which then enters the beamforming network. Within the beamforming network, the signal is amplified, phase-shifted, attenuated, and synthesized. The four received signals output from the beamforming network are down-converted into multiple receive channels. Multiple IF signals are simultaneously output to the signal processor. The processor simultaneously acquires data from multiple channels according to the designed receive gate, and then performs weighted synthesis of the multiple received data in the data domain to form the desired directional narrow beam.

[0035] The system of this invention is installed on a spaceborne motion platform to achieve two-dimensional high-resolution imaging of ground targets. The system has the characteristics of high resolution and wide swath.

[0036] Multiple high-power signals transmitted by a phased array feed need to be reflected by an umbrella-shaped reflector before they can be transmitted as a single wide beam.

[0037] When receiving multiple narrow beams, the signal backscattered from the ground needs to be reflected by the umbrella-shaped reflector before entering the phased array feed, and then received through the subsequent receiving path.

[0038] When receiving signals, multiple sets of weighting coefficients are simultaneously received within the signal processor (e.g., Figure 4 As shown in the figure, multiple narrow receiving beams are formed, and each receiving beam receives a portion of the signal width separately, thus achieving maximum gain reception.

[0039] In the beamforming network, power amplifiers N_1, N_2, and N_3 are grouped into power amplifier group 1. Their output power is different and controlled by the signal processor. One of the three power amplifiers is selected to output to the phased array feed N.

[0040] The total number of power amplifiers is three times the number of phased array feed sources; the first output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_1, power amplifier 2_1, ... is equal to the output power of power amplifier N_1; the second output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_2, power amplifier 2_2, ... is equal to the output power of power amplifier N_2; the third output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_3, power amplifier 2_3, ... is equal to the output power of power amplifier N_3.

[0041] This invention can be extended to high-resolution imaging radar for space targets.

[0042] The contents not described in detail in this specification are common knowledge to those skilled in the art.

[0043] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0044] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0045] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A lightweight, ultra-high resolution, wide-swath spaceborne SAR system, characterized in that, It includes a signal processor, frequency synthesizer, transmit channel, multiple receive channel, multiple internal scaler, power supply and distribution unit, beamforming network, phased array feed and umbrella reflector; The signal processor receives instructions from the satellite through a communication interface, can output intermediate frequency signals to the transmission channel, can send control signals to the beamforming network, and can also sample the received echo signals. The transmit channel is used to upconvert the intermediate frequency signal generated by the signal processor to produce the ultra-wideband radio frequency signal required for high resolution, and output it to the beamforming network. The multi-channel receiving system is used to amplify, filter, and down-convert radar echo signals that have passed through the beamforming network to intermediate frequency signals, forming multiple receiving signals, which are then output to the signal processor. The beamforming network is used to receive control signals from the signal processor, perform power division, phase shifting, and power amplification on the signals from the transmit channel, and then output them to the phased array feed. At the same time, it couples out signals for calibration. It amplifies, phase shifts, and attenuates the multiple signals received by the phased array feed and then outputs them to multiple receive channels. It can also couple calibration signals from multiple calibrators into the receive path. A phased array feed is used to radiate a high-power signal emitted by the beamforming network onto an umbrella reflector, and then send the echo received by the umbrella reflector to the beamforming network. Umbrella-shaped reflectors are used to transmit high-power signals radiated by the phased array feed to the ground, and then gather the echoes from the ground and feed them back into the phased array feed. The multi-channel internal calibrator connects the transmit channel, beamforming network, and multiple receive channels to form the three required calibration paths. The frequency synthesizer is used to generate the working clock and send it to the signal processor, and to generate the local oscillator signal required for radar frequency conversion and send it to the transmitting channel and multiple receiving channels. The power supply and distribution unit is used to provide power to all active units.

2. The lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 1, characterized in that, The signal processor is connected to the intermediate frequency input port of the transmitting channel via the intermediate frequency output port. It generates the timing sequence and intermediate frequency signal required for the upconversion of the transmitting channel through the internal signal generation unit, outputs the intermediate frequency signal to the transmitting channel, and calculates the required beamwidth and number of beams according to the SAR working coverage distance range. It generates corresponding control signals through the internal beam control unit and sends them to the beamforming network. The multi-channel sampling unit samples the received echo signal and completes the scanning reception through weighted calculation to obtain a high antenna receiving gain.

3. The lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 1, characterized in that, The three calibration paths formed by the multi-channel internal calibrator are as follows: the signal from the transmit channel is divided and sent to the beamforming network, which is the receive calibration path; the signal from the beamforming network is sent to the multiple receive channels, which is the transmit calibration path. The signal power of the transmitting channel is divided and sent to multiple receiving channels; this is the reference calibration path. The switching of each switch inside the multi-channel internal scaler is controlled by the signal processor.

4. The lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 1, characterized in that, The power supply and distribution unit is connected to the signal processor, frequency synthesizer, transmit channel, multiple receive channel, multiple internal scaler, beamforming network and phased array feed via power supply interfaces and power supply lines.

5. The lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 1, characterized in that, The system is installed on a spaceborne motion platform and enables two-dimensional high-resolution imaging of ground targets. The system features high resolution and wide swath.

6. The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system according to any one of claims 1 to 5, characterized in that, When the system is working, the intermediate frequency and signal bandwidth are designed according to the SAR working frequency band and the required signal bandwidth. Then, the frequency is up-converted to radio frequency through the transmission channel to generate the required ultra-wideband signal. The signal is then generated by the beamforming network to form the required transmission signal, which is output to the phased array feed. After passing through the umbrella reflector, the wide beam signal is transmitted. The signal reaches the illuminated target, is backscattered by the target, and returns to the umbrella reflector. The umbrella-shaped reflector focuses the echo onto the phased array feed, and then into the beamforming network, where it is amplified, phase-shifted, attenuated, and synthesized. The four received signals output from the beamforming network are down-converted into multiple receiving channels, and multiple intermediate frequency signals are simultaneously output to the signal processor. The processor simultaneously acquires data from multiple channels according to the designed receiving gate, and then performs weighted synthesis of the multiple received data in the data domain to form the desired narrow beam.

7. The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 6, characterized in that, The multiple high-power signals transmitted by the phased array feed need to be reflected by the umbrella-shaped reflector before they can be transmitted as a wide beam.

8. The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 6, characterized in that, When receiving multiple narrow beams, the signal backscattered from the ground needs to be reflected by an umbrella reflector before entering the phased array feed, and then received through the subsequent receiving path.

9. The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 6, characterized in that, When receiving signals, multiple sets of weighting coefficients inside the signal processor are received simultaneously to form multiple narrow receiving beams. Each receiving beam receives a portion of the signal width separately, thereby maximizing the receiving gain.

10. The operating method of the lightweight, ultra-high resolution, wide-swath spaceborne SAR system as described in claim 6, characterized in that, In the beamforming network, power amplifiers N_1, N_2, and N_3 are grouped into power amplifier group 1. Their output power is different and controlled by the signal processor. One of the three power amplifiers is selected to output to the phased array feed N. The total number of power amplifiers is three times the number of phased array feed sources; the first output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_1, power amplifier 2_1, ... is equal to the output power of power amplifier N_1; the second output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_2, power amplifier 2_2, ... is equal to the output power of power amplifier N_2; the third output power of each group of power amplifiers is equal, that is, the output power of power amplifier 1_3, power amplifier 2_3, ... is equal to the output power of power amplifier N_3.

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