Method and System for Compensating Phase Error Between SAR Antenna Panels of Lightweight Satellites

Abstract

This invention provides a method and system for compensating inter-panel phase error of a lightweight satellite SAR antenna, comprising: Step S1: calibrating the horn antenna position, calculating the RF link level, and establishing a wireless internal calibration test state; Step S2: setting the radar payload operating parameter command packet mode and parameters, performing payload power-on imaging, and processing and analyzing the payload data; Step S3: calibrating the spatial distance of the processed and analyzed data; Step S4: calculating the inter-panel phase error based on the calibrated spatial distance. This invention's method for compensating inter-panel phase error of a lightweight satellite SAR antenna effectively solves the problem of inter-panel phase error caused by the installation of SAR antenna sub-panels on the satellite cabin and the reconnection of inter-panel cables, eliminating the need to measure the phase error of each channel between panels in a near-field scanning system within a microwave anechoic chamber.

Description

Technical Field

[0001] This invention relates to the field of aerospace systems technology, specifically to a method and system for compensating phase error between SAR antenna panels of a lightweight satellite. Background Technology

[0002] Spaceborne Synthetic Aperture Radar (SAR) is an all-weather, all-time active Earth observation method that has played a significant role in military high-resolution observation, natural resource monitoring, and ocean monitoring. Most spaceborne SAR satellites employ planar active phased array antennas. Due to the envelope limitations of the launch vehicle, the SAR antenna is structurally composed of multiple sub-plates, which are retracted and deployed during the overall satellite testing phase.

[0003] Traditionally, the central electronic equipment and antenna integration testing for large satellite SAR are conducted integrated with the entire satellite module, significantly delaying the platform's installation and testing time. For smaller SAR satellites, to shorten the overall development process, the SAR payload integration testing phase can be conducted without integration with the satellite module. However, this necessitates the removal of high-frequency cables between the antenna sub-boards during transition phases, as well as the transportation, installation, and integration with the module. This installation of antenna sub-boards on the satellite module and the reconnection of cables introduce inter-board phase errors. These errors primarily originate from errors in the main RF path and calibration network. RF main path errors affect payload imaging quality. Therefore, precise calibration and compensation of inter-board cable phase errors are essential to ensure phase consistency across all radiation channels of the entire SAR antenna array.

[0004] For traditional SAR satellites, internal calibrators are often used to monitor the relative changes in amplitude and phase of each active path during imaging, while simultaneously performing compensation and calibration. However, this conventional wired internal calibration method often cannot distinguish whether the inter-plate phase error originates from the main path or the calibration path. Measuring inter-plate phase using a vector network analyzer requires disconnecting the inter-plate cable, connecting one end of the vector network analyzer to the inter-plate cable, and the other end to the main power divider. This method does not require powering on the entire satellite and is simple, but restoring the inter-plate cable to its onboard state inevitably causes changes in the shape of the cable connection, resulting in inaccurate inter-plate phase error compensation. Furthermore, this method involves onboard cable operations, which carries significant risks. Using a microwave anechoic chamber near-field scanning system to monitor the amplitude and phase of each T / R channel between the inter-plates offers high measurement accuracy, but the method is complex and time-consuming, increasing the development cycle of small and lightweight satellites.

[0005] A search revealed that while several domestic invention patents exist regarding phase error compensation methods between SAR antenna panels for lightweight satellites, they differ fundamentally from the present invention in their implementation. The specific differences are as follows:

[0006] The patented method for measuring and compensating the amplitude and phase error between channels of a multi-channel spaceborne SAR antenna (patent application number 202210139383.5) uses a planar near-field test system to measure the amplitude and phase data of the radiating element corresponding to each T / R component of the SAR antenna transmit / receive feed link. However, this invention does not consider the consistency of the channel amplitude and phase error between adjacent sub-boards.

[0007] The patented method for testing the performance of multi-channel SAR antennas based on wireless single T / R calibration (patent application number 201911150553.4) uses a wireless internal calibration method to test the performance of SAR antennas. This invention mainly detects the relative change in SAR antenna performance before and after vibration test, but does not introduce the measurement and compensation of phase error between the inter-board channels.

[0008] The patented satellite SAR antenna T / R channel amplitude and phase inspection device and its operation method (2019, application number 201910689477.8) mainly introduces the operation of the measuring device, but does not propose the measurement and compensation of the phase error of the inter-plate channel.

[0009] The patented "Measurement Method for Amplitude and Phase Consistency Error Calibration between Channels in Spaceborne SAR Imaging" (2019, Application No. 201910290379.7) and the patented "Test Method for Full-Link Amplitude and Phase Stability of Channels in Active Phased Array SAR" (2019, Application No. 201911276320.9) mainly detect the relative changes in amplitude and phase between channels under different operating conditions, but do not mention the measurement and compensation of phase error between channels; the paper "Research on a Novel Wireless Internal Calibration Method for Spaceborne SAR" (2018, Journal of Radar) proposes a wireless internal calibration method to obtain the amplitude and phase characteristics of T / R channels, but does not mention the measurement and compensation of phase error between channels.

[0010] The patented method for far-field measurement of inter-plate phase difference in the whole-satellite stage of spaceborne synthetic aperture radar (application number 201910291110.0) has an inaccurate data model and certain approximation errors. In addition, the invention does not propose an inter-plate phase compensation method.

[0011] Regarding the phase compensation method for the inter-panel channel of SAR antennas for lightweight satellites, no descriptions or reports of similar technologies as this invention have been found, and no similar information has been collected domestically or internationally. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for compensating phase errors between panels of a lightweight satellite SAR antenna.

[0013] A method for compensating phase error between panels of a lightweight satellite SAR antenna according to the present invention includes:

[0014] Step S1: Calibrate the horn antenna position, calculate the RF link level, and establish the wireless internal calibration test state;

[0015] Step S2: Set the radar payload operating parameter command package mode and parameters, perform payload power-on imaging, and process and analyze payload data;

[0016] Step S3: Perform spatial distance calibration on the processed and analyzed data;

[0017] Step S4: Calculate the inter-plate phase error based on the calibrated spatial distance.

[0018] Preferably, in step S1:

[0019] A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated.

[0020] The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation:

[0021]

[0022] Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength;

[0023] Based on the transmission power Pt dBm and the connection cable insertion loss C L dB, antenna element gain is Gr dB, probe gain is Gt dB, and additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the dynamic requirements of T / R component reception;

[0024] The receiving calibration signal link includes the output power P of the internal calibration module.cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows:

[0025] P r =P cal +C L +G t +S L +G r +M L +G re +M re

[0026] P is inserted in series in the ground test cable link r dB fixed attenuator;

[0027] Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

[0028] Preferably, in step S2:

[0029] The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to the ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. The comprehensive service parameters are set, including the payload mission start time, mission duration, file number, file playback duration and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to the ground through the data transmission channel. The ground performs pulse compression processing on the payload data and extracts the phase values ​​of the peak points of each T / R channel.

[0030] Preferably, in step S3:

[0031] The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows:

[0032] Step S3.1: Based on the geometric relationships between the horn probe, the center of the inter-board, and the waveguides, establish the following relationships:

[0033]

[0034] Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array.

[0035] Step S3.2: Based on the phase data of each channel of each sub-board, use function fitting to fit the R0 and constant c of each sub-board;

[0036]

[0037] Where, φ n Let n be the phase of each sub-board channel n, and k be a constant.

[0038] Preferably, in step S4:

[0039] Step S4.1: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase difference between adjacent plates when the phase is at the midpoint.

[0040] Step S4.2: After compensating for the phase error of each channel of the sub-board, calculate R0 and constant c for each sub-board using function fitting.

[0041] Step S4.3: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase at the midpoint. The phase difference is the phase difference between adjacent plates after compensation.

[0042] Step S4.4: Generate wave control codes from the inter-board errors and remotely transmit the wave control codes to the load subsystem.

[0043] A lightweight satellite SAR antenna inter-panel phase error compensation system according to the present invention includes:

[0044] Module M1: calibrates the horn antenna position, calculates the RF link level, and establishes the wireless internal calibration test state;

[0045] Module M2: Sets the command package mode and parameters for radar payload operation, performs payload startup imaging, and processes and analyzes payload data;

[0046] Module M3: Performs spatial distance calibration on the processed and analyzed data;

[0047] Module M4: Calculates inter-board phase error based on the calibrated spatial distance.

[0048] Preferably, in module M1:

[0049] A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated.

[0050] The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation:

[0051]

[0052] Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength;

[0053] Based on the transmission power Pt dBm and the connection cable insertion loss C L dB, antenna element gain is Gr dB, probe gain is Gt dB, and additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the dynamic requirements of T / R component reception;

[0054] The receiving calibration signal link includes the output power P of the internal calibration module. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows:

[0055] P r =P cal +C L +G t +S L +G r +M L +G re +M re

[0056] P is inserted in series in the ground test cable link r dB fixed attenuator;

[0057] Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

[0058] Preferably, in module M2:

[0059] The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to the ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. The comprehensive service parameters are set, including the payload mission start time, mission duration, file number, file playback duration and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to the ground through the data transmission channel. The ground performs pulse compression processing on the payload data and extracts the phase values ​​of the peak points of each T / R channel.

[0060] Preferably, in module M3:

[0061] The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows:

[0062] Module M3.1: Based on the geometric relationships between the horn probe, the center of the board, and the waveguides, the following relationships are established:

[0063]

[0064] Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array.

[0065] Module M3.2: Based on the phase data of each channel of each input sub-board, the R0 and constant c of each sub-board are fitted using a function fitting method;

[0066]

[0067] Where, φ n Let n be the phase of each sub-board channel n, and k be a constant.

[0068] Preferably, in module M4:

[0069] Module M4.1: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase difference between adjacent plates when the phase is at the midpoint.

[0070] Module M4.2: After compensating for the phase error of each channel of the sub-board, the R0 and constant c of each sub-board are calculated by function fitting.

[0071] Module M4.3: Substitute R0 and constant c into the formula to fit two curves between phase φ and Y on both sides of the plate, and calculate the phase at the midpoint. The phase difference is the phase difference between adjacent plates after compensation.

[0072] Module M4.4: Generates wave control codes from inter-board errors and transmits these codes to the load subsystem via remote control.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] 1. The present invention provides a method for compensating phase errors between SAR antenna panels of a lightweight SAR satellite, which addresses the phase error problem caused by the installation of SAR antenna sub-panels on the satellite cabin and the reconnection of cables between the panels. It eliminates the need to measure the phase error of each channel between the panels in a near-field scanning system in a microwave anechoic chamber.

[0075] 2. The phase error compensation method between SAR antenna panels of the lightweight SAR satellite of the present invention is simple to operate and has guaranteed accuracy. It significantly shortens the development cycle of small satellites, improves the overall satellite testing efficiency, provides important technical support for the mass production of lightweight SAR satellites, and accelerates the development progress of batch small satellites.

[0076] 3. The phase error compensation method between SAR antenna boards of the lightweight SAR satellite of the present invention makes up for the shortcomings of the internal calibration system that cannot monitor the semi-steel cables and waveguides connecting the T / R components and the waveguide subarray. It can also monitor the amplitude and phase changes of each T / R channel of the SAR antenna subboard during the whole satellite integration test process (transition, mechanical vibration).

[0077] 4. The phase error compensation method between SAR antenna panels of the present invention for lightweight SAR satellites is also applicable to the compensation of phase error between SAR antenna panels of all SAR satellites using planar active phased array antennas. Attached Figure Description

[0078] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0079] Figure 1 This is a schematic flowchart of the method of the present invention;

[0080] Figure 2 This is a top view of the SAR antenna layout according to the method of the present invention;

[0081] Figure 3 This is a front view of the SAR antenna array layout of the method of the present invention;

[0082] Figure 4 This is a schematic diagram of the antenna spherical wave principle of the method of the present invention;

[0083] Figure 5 This is a curve showing the distribution of phase error between the front plates compensated by the method of the present invention.

[0084] Figure 6 This is a graph showing the distribution of phase error between boards after compensation using the method of the present invention. Detailed Implementation

[0085] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0086] Example 1:

[0087] This invention discloses a method for compensating phase errors between panels of a lightweight satellite SAR antenna, belonging to the field of aerospace system technology. The main steps include: Step 1, precise calibration of the horn antenna position; Step 2, calculation of the radio frequency link level; Step 3, establishment of a wireless internal calibration test state; Step 4, setting the radar payload operating parameter command packet mode and parameters, payload power-on imaging, data processing and analysis; Step 5, precise spatial distance calibration based on phase data; Step 6, inter-panel phase error compensation and verification. The inter-panel phase error compensation method for lightweight satellite SAR antennas proposed in this invention achieves simple and efficient testing using a standard horn antenna, eliminating the need for complex testing operations of traditional anechoic chamber planar near-field scanning systems, significantly reducing testing time while ensuring accuracy. This significantly shortens the development cycle of lightweight SAR satellites, improves overall satellite testing efficiency, and provides important technical support for the mass production of lightweight satellites.

[0088] The present invention provides a method for compensating phase error between panels of a lightweight satellite SAR antenna, such as... Figures 1-6 As shown, it includes:

[0089] Step S1: Calibrate the horn antenna position, calculate the RF link level, and establish the wireless internal calibration test state;

[0090] Specifically, in step S1:

[0091] A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated.

[0092] The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation:

[0093]

[0094] Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength;

[0095] Based on the transmission power Pt dBm and the connection cable insertion loss C L dB, antenna element gain is Gr dB, probe gain is Gt dB, and additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the dynamic requirements of T / R component reception;

[0096] The receiving calibration signal link includes the output power P of the internal calibration module. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows:

[0097] P r =P cal +C L +G t +S L +G r +M L +G re +M re

[0098] P is inserted in series in the ground test cable link r dB fixed attenuator;

[0099] Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

[0100] Step S2: Set the radar payload operating parameter command package mode and parameters, perform payload power-on imaging, and process and analyze payload data;

[0101] Specifically, in step S2:

[0102] The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to the ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. The comprehensive service parameters are set, including the payload mission start time, mission duration, file number, file playback duration and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to the ground through the data transmission channel. The ground performs pulse compression processing on the payload data and extracts the phase values ​​of the peak points of each T / R channel.

[0103] Step S3: Perform spatial distance calibration on the processed and analyzed data;

[0104] Specifically, in step S3:

[0105] The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows:

[0106] Step S3.1: Based on the geometric relationships between the horn probe, the center of the inter-board, and the waveguides, establish the following relationships:

[0107]

[0108] Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array.

[0109] Step S3.2: Based on the phase data of each channel of each sub-board, use function fitting to fit the R0 and constant c of each sub-board;

[0110]

[0111] Where, φ n Let n be the phase of each sub-board channel n, and k be a constant.

[0112] Step S4: Calculate the inter-plate phase error based on the calibrated spatial distance.

[0113] Specifically, in step S4:

[0114] Step S4.1: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase difference between adjacent plates when the phase is at the midpoint.

[0115] Step S4.2: After compensating for the phase error of each channel of the sub-board, calculate R0 and constant c for each sub-board using function fitting.

[0116] Step S4.3: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase at the midpoint. The phase difference is the phase difference between adjacent plates after compensation.

[0117] Step S4.4: Generate wave control codes from the inter-board errors and remotely transmit the wave control codes to the load subsystem.

[0118] Example 2:

[0119] Example 2 is a preferred embodiment of Example 1, and is used to illustrate the present invention in more detail.

[0120] The present invention also provides a phase error compensation system between lightweight satellite SAR antenna panels. The phase error compensation system between lightweight satellite SAR antenna panels can be implemented by executing the process steps of the phase error compensation method between lightweight satellite SAR antenna panels. That is, those skilled in the art can understand the phase error compensation method between lightweight satellite SAR antenna panels as a preferred embodiment of the phase error compensation system between lightweight satellite SAR antenna panels.

[0121] A lightweight satellite SAR antenna inter-panel phase error compensation system according to the present invention includes:

[0122] Module M1: calibrates the horn antenna position, calculates the RF link level, and establishes the wireless internal calibration test state;

[0123] Specifically, in module M1:

[0124] A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated.

[0125] The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation:

[0126]

[0127] Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength;

[0128] Based on the transmission power Pt dBm and the connection cable insertion loss C L dB, antenna element gain is Gr dB, probe gain is Gt dB, and additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the dynamic requirements of T / R component reception;

[0129] The receiving calibration signal link includes the output power P of the internal calibration module. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows:

[0130] P r =P cal +C L +G t +S L +G r +M L +G re +M re

[0131] P is inserted in series in the ground test cable link r dB fixed attenuator;

[0132] Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

[0133] Module M2: Sets the command package mode and parameters for radar payload operation, performs payload startup imaging, and processes and analyzes payload data;

[0134] Specifically, in module M2:

[0135] The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to the ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. The comprehensive service parameters are set, including the payload mission start time, mission duration, file number, file playback duration and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to the ground through the data transmission channel. The ground performs pulse compression processing on the payload data and extracts the phase values ​​of the peak points of each T / R channel.

[0136] Module M3: Performs spatial distance calibration on the processed and analyzed data;

[0137] Specifically, in module M3:

[0138] The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows:

[0139] Module M3.1: Based on the geometric relationships between the horn probe, the center of the board, and the waveguides, the following relationships are established:

[0140]

[0141] Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array.

[0142] Module M3.2: Based on the phase data of each channel of each input sub-board, the R0 and constant c of each sub-board are fitted using a function fitting method;

[0143]

[0144] Where, φ n Let n be the phase of each sub-board channel n, and k be a constant.

[0145] Module M4: Calculates inter-board phase error based on the calibrated spatial distance.

[0146] Specifically, in module M4:

[0147] Module M4.1: Substitute R0 and constant c into the formula, fit two curves between phase φ and Y on both sides of the plate, and calculate the phase difference between adjacent plates when the phase is at the midpoint.

[0148] Module M4.2: After compensating for the phase error of each channel of the sub-board, the R0 and constant c of each sub-board are calculated by function fitting.

[0149] Module M4.3: Substitute R0 and constant c into the formula to fit two curves between phase φ and Y on both sides of the plate, and calculate the phase at the midpoint. The phase difference is the phase difference between adjacent plates after compensation.

[0150] Module M4.4: Generates wave control codes from inter-board errors and transmits these codes to the load subsystem via remote control.

[0151] Example 3:

[0152] Example 3 is a preferred example of Example 1, and is used to illustrate the present invention in more detail.

[0153] To address the shortcomings of existing technologies, this invention provides a method for phase error compensation between panels of a lightweight satellite SAR antenna. This method disconnects the internal calibration system from the antenna calibration network port and connects the fixed attenuator and the horn probe through a ground high-frequency test cable of a certain length to form a wireless external calibration network. This network forms a transceiver loop with the SAR antenna, establishing a wireless internal calibration state. The main phase data of each single T / R channel between sub-boards is obtained using a wireless internal calibration method. Based on the obtained phase data of each sub-board channel, the R0 and constant c of each sub-board are accurately calibrated using a function fitting method. Substituting R0 and constant c into the spherical wave equation, two curves between the phase and Y are fitted on both sides of the sub-board, and then the phase at the midpoint is calculated. The phase difference is the phase difference between adjacent sub-boards. After compensating for the phase error of the channel between sub-boards, the R0 and constant c of each sub-board are accurately calibrated again using the same function fitting method. Substituting R0 and constant c into the spherical wave equation, the compensated phase difference between the sub-boards is calculated. The inter-board error is generated into a wave control code, which is then remotely transmitted to the load subsystem.

[0154] This invention employs a wireless internal calibration method to achieve phase compensation between SAR antenna boards. It eliminates the need for an antenna calibration network; the phase error between boards can be monitored and compensated simply through the RF transceiver path. This invention eliminates the complex testing operations of traditional anechoic chamber planar near-field scanning systems, significantly reducing testing time while maintaining accuracy. It noticeably shortens the development cycle of lightweight SAR satellites, improves overall satellite testing efficiency, and provides crucial technical support for the mass production of lightweight satellites. Furthermore, this invention overcomes the limitations of internal calibration systems in monitoring the semi-steel cables connecting the T / R components to the waveguide subarray, as well as the waveguide itself. It also monitors the amplitude and phase changes of each T / R channel on the SAR antenna subboard during the overall satellite integration testing process (field transitions, mechanical vibrations).

[0155] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solutions.

[0156] See Figure 1 , Figure 1 This is a flowchart illustrating a phase error compensation method between SAR antenna panels for a lightweight SAR satellite, as provided in this embodiment. The specific steps are as follows:

[0157] A method for compensating phase error between panels of a lightweight satellite SAR antenna includes the following steps:

[0158] Step 1: Accurately calibrate the position of the horn antenna and ensure it meets the far-field conditions;

[0159] Step 2, RF link level calculation;

[0160] Step 3: Establish wireless internal calibration test status;

[0161] Step 4: Radar payload operating parameter command package mode and parameter settings, payload power-on imaging, data processing and analysis;

[0162] Step 5: Perform spatial distance calibration based on the measured data;

[0163] Step 6: Inter-board phase error compensation and verification.

[0164] Step 1 involves preparing the entire test site.

[0165] Step 2 is to calculate the level of the entire RF link, which is equivalent to the evaluation of the system level.

[0166] Step 3 involves establishing the entire test setup, including connecting the ground cables and satellite cables.

[0167] Step 4 involves setting the command package at the start of the experiment, powering on the load for imaging, and performing data processing and analysis.

[0168] Step 5: Based on the data processed in Step 4, spatial distance is calibrated.

[0169] Step 6: Calculate and verify the inter-plate phase error based on the spatial distance calibrated in Step 5.

[0170] Preferably, in step 1, a level is used to precisely aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, and the relative positional relationship between the laser rangefinder and the horn antenna probe is measured to calculate the specific positional relationship between the horn antenna probe and the SAR antenna array. This invention ensures that the radiation patterns of each element of the horn antenna and the SAR antenna are within the main lobe of the beam; ensures that the distance between the horn antenna probe and each element of the SAR antenna meets the far-field condition; and ensures that the horn antenna is aligned with the mechanical center between the sub-plates of the SAR antenna array for inter-plate phase measurement.

[0171] Preferably, in step 2, the method described herein employs a calibration signal receiving link. The output signal from the frequency modulation signal source is transmitted to the horn antenna via an internal calibrator and a calibration test cable. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is mainly determined by the horn probe's transmit power and the receiving P-1 of the T / R components. The probe's transmit power is directly taken from the output signal received by the internal calibrator, according to the radar equation:

[0172]

[0173] R is the distance between the phase center of the horn antenna and the antenna array, λ is the wavelength, and its value is 0.03125. Based on the transmit power Pt dBm and the connection cable insertion loss approximately C... L dB, antenna element gain is Gr dB, probe gain is approximately Gt dB, and additional spatial transmission loss is approximately S. L dB, calculate the input power P of the T / R receiver. r dBm, P r The T / R component must be able to receive dynamic signals.

[0174] The method of this invention mainly includes the internal calibration module output power P in the calibration signal receiving link. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G reReceiver Manual Gain Control (MGC) (M re ), calculate the total received power of the entire link as:

[0175] P r =P cal +C L +G t +S L +G r +M L +G re +M re

[0176] To balance the signal level of the entire system's received signal link, P is inserted in series into the ground test cable link in this invention. r A fixed attenuator in dB.

[0177] Preferably, in step 3, compared to the traditional wired internal calibration method, this invention disconnects the internal calibrator from the antenna calibration network port and connects the attenuator and horn antenna probe through a certain length of ground high-frequency test cable to form a wireless internal calibration network, which constitutes a transceiver loop with the SAR antenna. Traditional wired internal calibration methods often use an internal calibrator to monitor the relative changes in amplitude and phase of each active path in the system during the imaging process, while simultaneously performing compensation and calibration. However, this conventional wired internal calibration method often cannot distinguish whether the inter-board phase error originates from the main path or the calibration path. This invention employs a wireless internal calibration test method, which only passes through the RF transceiver link and not the antenna calibration network, thus eliminating the influence of antenna calibration network errors. Furthermore, the wireless internal calibration method used in this invention, in addition to monitoring the amplitude and phase characteristics of the active T / R components, can also monitor the amplitude and phase characteristics of passive arrays such as semi-rigid cables and waveguide antennas from the T / R components to the antenna.

[0178] Preferably, in step 4, the payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to the ground while recording and playing back. Appropriate PRF and working pulse width are set to meet the maximum duty cycle limit; appropriate signal bandwidth, sampling rate, sampling start, compression ratio, and other parameters are set to select an appropriate frame length to meet the maximum and minimum frame length limits, as well as the data rate limit; comprehensive service parameters such as payload mission start time, mission duration, file number, file playback duration, and data transmission mission mode are set. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to the ground through the data transmission channel. The ground performs pulse compression processing on the payload data and extracts the phase values ​​of the peak points of each T / R channel.

[0179] Preferably, in step 5, based on engineering experience, the installation of the horn bracket and horn antenna probe inevitably introduces measurement errors. Therefore, the spatial distance R0 cannot be directly substituted into the spherical wave equation to calculate the inter-plate phase. This invention uses the T / R channel phase data extracted from testing or simulation to deduce the spatial distance between the horn antenna probe and the SAR antenna, as follows:

[0180] Step 5.1: Based on the geometric relationships between the horn probe, the center of the inter-board structure, and the waveguides, establish the following relationships:

[0181]

[0182] Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array.

[0183] Step 5.2: Based on the phase data of each channel of each sub-board input from the test or simulation, use function fitting to fit the R0 and constant c of each sub-board;

[0184]

[0185] Where, φ n Let n be the phase of each sub-board channel n, and k be a constant.

[0186] Preferably, step 6 mainly includes the following steps:

[0187] Step 6.1: Substitute R0 and constant c into formula (2), fit two curves between phase φ and Y on both sides of the plate, and then calculate their phase at the midpoint (when Y = 0). The phase difference is the phase difference between adjacent plates.

[0188] Step 6.2: After compensating for the phase error of each channel of the sub-board, the R0 and constant c of each sub-board are calculated by function fitting.

[0189] Step 6.3: Substitute R0 and constant c into formula (2), fit two curves between phase φ and Y on both sides of the plate, and then calculate their phase at the midpoint (when Y = 0). The phase difference is the phase difference between adjacent plates after compensation.

[0190] Step 6.4: Generate wave control codes from the inter-board errors and remotely transmit the wave control codes to the load subsystem.

[0191] The compensated inter-board phase error results meet the system error requirements, verifying that the system state is stable after the inter-board phase error compensation.

[0192] Example 4:

[0193] Example 4 is a preferred example of Example 1, which is used to illustrate the present invention in more detail.

[0194] The effects of the present invention will be further explained below with reference to simulation data.

[0195] Typical parameters of X-band spaceborne SAR were used in this experiment, as shown in Table 1. First, a wireless internal calibration state was established. A standard BJ100 X-band horn probe and a fine-tuning bracket were selected. The horn probe was precisely aimed at the geometric and mechanical center of points A and B. The distance from the horn probe to the antenna array was approximately 3 meters. The SAR antenna and horn probe setup are as follows: Figure 2-3 Point A is located at the geometric center of channel 60 of sub-board 1 and channel 61 of sub-board 2, and point B is located at the geometric center of channel 121 of sub-board 3 and channel 120 of sub-board 2.

[0196] Table 1 Input parameters in the embodiments

[0197]

[0198]

[0199] Based on the input system requirements parameters given in Table 1, after aiming the horn probe at positions A to B, the method of this invention is used to fit R0 and constant c to the input T / R channel phase data to complete the precise calibration of the spatial distance R0.

[0200] Table 2. Precise calibration results of spatial distance R0

[0201] dot number Sub-board Number of channels <![CDATA[R0]]> c A 1 1-60 3.06 654.8 A 2 61-120 2.876 579.2 B 2 61-120 2.991 644.6 B 3 121-180 2.918 585.8

[0202] Substituting R0 and the constant c into formula (2), two curves between phase φ and Y are fitted on both sides of the plate, as follows: Figure 5 As shown. When Y=0, the phase between each plate is calculated, and the phase difference is the phase difference between adjacent plates.

[0203] Table 3. Measurement results of the center phase difference between plates

[0204]

[0205] By monitoring the main path phase error of a single T / R channel between each sub-board using this invention, it was found that the maximum phase error between two adjacent channels of sub-board 1 and sub-board 2 is approximately 0.905654 rad. The phase error between sub-board 1 is higher than that between sub-board 2, while the phase error between sub-board 3 is lower than that between sub-board 2. Therefore, this invention reduces the original channel phase value of sub-board 1 (1-60) by 0.905654 rad and adds the original channel phase value of sub-board 3 (121-180) by 0.14024 rad to balance the phase error between the boards.

[0206] The original phase data of each channel after balancing are once again precisely calibrated in terms of spatial distance, and R0 and constant c are calculated by fitting.

[0207] Table 4. Accurate calibration results of spatial distance R0 after compensation

[0208] dot number Sub-board aisle <![CDATA[R0]]> c A Sub-board 1 1-60 3.06 653.9 B Sub-board 3 121-180 2.918 585.9

[0209] Substituting R0 and the constant c into formula (2), two curves between the phase and Y are fitted on both sides of the plate, as follows: Figure 6 As shown. When Y=0, the phase between each plate is calculated, and the phase difference is the phase difference between the plates after compensation.

[0210] Table 5. Measurement results of the center phase difference between the plates after compensation.

[0211]

[0212] This invention measures and compensates for the phase error between SAR antenna panels. After compensation, the phase error between sub-panels 1 and 2 is better than 0.00565 rad, and the phase error between sub-panels 2 and 3 is better than 0.04024 rad, all less than 5.625°, indicating that the system is stable. Therefore, simulation analysis verifies the effectiveness of the proposed method for compensating for phase error between SAR antenna panels of a lightweight SAR satellite.

[0213] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0214] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for compensating phase error between panels of a lightweight satellite SAR antenna, characterized in that, include: Step S1: Calibrate the horn antenna position, calculate the RF link level, and establish the wireless internal calibration test state; Step S2: Set the radar payload operating parameter command package mode and parameters, perform payload power-on imaging, and process and analyze payload data; Step S3: Perform spatial distance calibration on the processed and analyzed data; Step S4: Calculate the inter-plate phase error based on the calibrated spatial distance; In step S3: The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows: Step S3.1: Based on the geometric relationships between the horn probe, the center of the inter-board, and the waveguides, establish the following relationships: Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array. Step S3.2: Based on the phase data of each channel of each sub-board, use function fitting to fit the R0 and constant c of each sub-board; Where, φ n Let n be the phase of each sub-board channel n, and k be a constant. λ is the wavelength.

2. The method for compensating phase error between panels of a lightweight satellite SAR antenna according to claim 1, characterized in that, In step S1: A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated. The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation: Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength; According to the transmission power P t dBm, cable insertion loss C L dB, antenna element gain is G r dB, probe gain G t dB, additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the requirements for dynamic reception by the T / R component; The receiving calibration signal link includes the output power P of the internal calibration module. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows: P r =P cal +C L +G t +S L +G r +M L +G re +M re P is inserted in series in the ground test cable link r dB fixed attenuator; Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

3. The method for compensating phase error between panels of a lightweight satellite SAR antenna according to claim 1, characterized in that, In step S2: The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start time, and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. Comprehensive service parameters are set, including payload mission start time, mission duration, file number, file playback duration, and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to ground via the data transmission channel. The ground system performs pulse compression processing on the load data to extract the phase values ​​of the peak points of each T / R channel.

4. A lightweight satellite SAR antenna inter-panel phase error compensation system, characterized in that, include: Module M1: calibrates the horn antenna position, calculates the RF link level, and establishes the wireless internal calibration test state; Module M2: Sets the command package mode and parameters for radar payload operation, performs payload startup imaging, and processes and analyzes payload data; Module M3: Performs spatial distance calibration on the processed and analyzed data; Module M4: Calculates inter-board phase error based on the calibrated spatial distance; In module M3: The spatial distance between the horn antenna probe and the SAR antenna is deduced from the extracted T / R channel phase data, as follows: Module M3.1: Based on the geometric relationships between the horn probe, the center of the board, and the waveguides, the following relationships are established: Among them, R n Y represents the distance from the horn phase center to the nth waveguide; n R0 represents the distance between the center O' of the inter-plate space and the nth waveguide, and R0 is the distance between the phase center of the horn antenna and the antenna array. Module M3.2: Based on the phase data of each channel of each input sub-board, the R0 and constant c of each sub-board are fitted using a function fitting method; Where, φ n Let n be the phase of each sub-board channel n, and k be a constant. λ is the wavelength.

5. The lightweight satellite SAR antenna inter-panel phase error compensation system according to claim 4, characterized in that, In module M1: A level is used to aim at the horn antenna probe and the SAR antenna array, ensuring that the horn antenna probe is parallel to the SAR antenna array and perpendicular to the ground; a laser rangefinder is fixed on the horn antenna probe, the relative positional relationship between the laser rangefinder and the horn probe is measured, and the specific positional relationship between the horn probe and the SAR antenna array is calculated. The calibration signal receiving link transmits the FM signal source output signal through the internal calibrator and calibration test cable to the horn antenna. It is then spatially coupled to the receiving channels of each T / R component of the active phased array antenna, and finally synthesized before being sent to the radar receiver. The safe power range of the calibration signal is determined by the horn probe's transmit power and the T / R component's reception. The probe's transmit power is taken from the internal calibrator's received output signal, according to the radar equation: Where R is the distance between the phase center of the horn antenna and the antenna array, and λ is the wavelength; According to the transmission power P t dBm, cable insertion loss C L dB, antenna element gain is G r dB, probe gain G t dB, additional spatial transmission loss is S L dB, calculate the input power P of the T / R receiver. r dBm, P r Meets the requirements for dynamic reception by the T / R component; The receiving calibration signal link includes the output power P of the internal calibration module. cal Calibration test cable insertion loss C L horn antenna gain G t , Probe-to-antenna array coupling attenuation S L Antenna receiving gain G r Microwave combined insertion loss M L Receiver gain G re Receiver manual gain control M re The total received power of the entire link is calculated as follows: P r =P cal +C L +G t +S L +G r +M L +G re +M re P is inserted in series in the ground test cable link r dB fixed attenuator; Disconnect the internal calibrator from the antenna calibration network port, and connect the attenuator and horn antenna probe through a ground high-frequency test cable of a preset length to form a wireless internal calibration network, which together with the SAR antenna forms a transceiver loop.

6. The lightweight satellite SAR antenna inter-panel phase error compensation system according to claim 4, characterized in that, In module M2: The payload imaging mode is set to continuous test calibration mode, the calibration mode is set to continuous single T / R calibration, the payload working mode is set to receive only, and the whole satellite mission mode is set to transmit data to ground while recording and playing back. The PRF and working pulse width are set to meet the maximum duty cycle limit. The signal bandwidth, sampling rate, sampling start time, and compression ratio are set, and the frame length is selected to meet the maximum and minimum frame length limits, as well as the data rate limit. Comprehensive service parameters are set, including payload mission start time, mission duration, file number, file playback duration, and data transmission mission mode. The payload subsystem performs power-on imaging according to the command packet parameter settings, and the effective payload data is transmitted to ground via the data transmission channel. The ground system performs pulse compression processing on the load data to extract the phase values ​​of the peak points of each T / R channel.

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