On-orbit calibration system for low-orbit satellite digital phased array and method for applying the system

Abstract

This invention provides an on-orbit calibration system for a low-Earth orbit (LEO) satellite digital phased array and a method for applying the system. The system includes a satellite to be calibrated, an auxiliary satellite, and a ground control unit interconnected by communication. The auxiliary satellite has the same phased array system structure as the satellite to be calibrated and is used to transmit or receive given calibration signals during collaborative calibration of the satellite to be calibrated. The ground control unit monitors the satellite status of the satellite to be calibrated, determines calibration conditions, and schedules the transmission of calibration start commands. The calibration compensation module applies calculated error compensation parameters to pre-compensate or post-compensate the amplitude, phase, and delay of the digital signals transmitted or received through each channel of the satellite to be calibrated. This invention achieves on-orbit calibration of the satellite to be calibrated through collaboration among LEO satellites, effectively improving the autonomous survivability and on-orbit service reliability of the satellite system.

Description

Technical Field

[0001] This invention relates to the field of satellite communication and radio frequency technology, and in particular to an on-orbit calibration system for a low-Earth orbit satellite digital phased array and a method for applying the system. Background Technology

[0002] As a key component of modern low-Earth orbit satellite communication systems, the beamforming quality of phased array antennas directly affects signal coverage and transmission stability. During on-orbit operation, the amplitude, phase, and delay parameters of each channel of the satellite antenna are susceptible to changes in the external space environment and the performance evolution of internal components, resulting in inconsistencies. This can lead to problems such as beam pointing errors and gain reduction, posing a continuous threat to the stability of the communication link and data transmission efficiency.

[0003] Currently, calibration methods for addressing the aforementioned channel parameter drift mainly fall into two categories: autonomous calibration based on onboard auxiliary circuits and external calibration completed in cooperation with ground control stations. Onboard autonomous calibration typically embeds a reference signal source, coupling network, and detection unit within the system to construct a closed-loop correction circuit, enabling the monitoring and adjustment of the status of each channel. External calibration, on the other hand, relies on ground stations transmitting or receiving specific calibration signals, completing parameter measurement and compensation through satellite-to-ground interaction.

[0004] However, while onboard autonomous calibration schemes can operate in real time, they require dedicated hardware, which not only increases the weight and power consumption burden on the satellite platform but may also cause slow drift of the onboard calibration reference due to interference from the same environmental factors, leading to a gradual decline in long-term calibration accuracy. On the other hand, calibration modes relying on ground stations are limited by the distribution and availability of ground infrastructure. When ground stations fail to cover certain transit areas of the satellite (such as polar regions or offshore areas) or when the ground system experiences temporary failures, the satellite cannot obtain timely and effective parameter corrections, resulting in continuous degradation of antenna performance and making it difficult to guarantee continuous global service capabilities. Summary of the Invention

[0005] This invention provides an on-orbit calibration system for a low-orbit satellite digital phased array and a method for applying the system, in order to solve the defects of existing technologies in terms of applicability and reliability that cannot be maintained stably for a long time, and to achieve the goal of effectively improving the system's accuracy, adaptability and reliability.

[0006] This invention provides an on-orbit calibration system for a low-Earth orbit satellite digital phased array, comprising a satellite to be calibrated, an auxiliary satellite, and a ground control unit that are interconnected. The satellite to be calibrated includes: a phased array antenna, a radio frequency front-end, a digital-to-analog / analog-to-digital converter, a digital beamforming network, a calibration compensation module, and a main control unit; The auxiliary satellite has the same phased array system structure as the satellite to be calibrated, and is used to transmit or receive a given calibration signal during the process of collaboratively calibrating the satellite to be calibrated. The ground control unit is used to monitor the satellite status of the satellite to be calibrated, determine the calibration conditions, and schedule the sending of calibration start commands. The calibration compensation module stores and applies the calculated error compensation parameters to perform pre-compensation or post-compensation on the amplitude, phase and delay of the digital signals transmitted or received through each channel of the satellite to be calibrated.

[0007] According to the present invention, a low-orbit satellite digital phased array on-orbit calibration system is provided, wherein the main control unit of the satellite to be calibrated is used to monitor the received G / T value, and when the received G / T value is detected to be lower than a preset threshold, a first calibration request is sent to the ground control unit; The ground control unit is used to receive the first calibration request, and select and schedule the first auxiliary satellite that meets the conditions according to the ephemeris and the first calibration request; The first auxiliary satellite is used to calculate the beam pointing angle according to the first calibration request, and based on the beam pointing angle, transmit a first calibration signal to the satellite to be calibrated; The phased array antenna of the satellite to be calibrated is used to receive the first calibration signal and transmit the first calibration signal to the radio frequency front end through each channel of the satellite to be calibrated; The radio frequency front end of the satellite to be calibrated is used to down-convert the first calibration signal to obtain an intermediate frequency signal; The digital-to-analog / analog-to-digital converter of the satellite to be calibrated is used to perform analog-to-digital conversion processing on the intermediate frequency signal to obtain a digital baseband signal; The digital beamforming network of the satellite to be calibrated is used to calculate the measurement delay of each channel by cross-correlation based on the digital baseband signal, and to calculate the amplitude and phase response by least squares. Based on the channel measurement delay and the amplitude and phase response, combined with the incident direction and the array element position, the first ideal DBF phase difference is calculated, and the first ideal DBF phase difference is discarded to obtain the first channel-level error. The calibration compensation module of the satellite to be calibrated is used to update the receiving compensation parameters based on the first channel-level error, and complete the receiving channel calibration.

[0008] According to the present invention, in an on-orbit calibration system for a low-Earth orbit satellite digital phased array, the first auxiliary satellite, when used to transmit a first calibration signal to the satellite to be calibrated, is specifically used for: The first calibration request is obtained by the main control unit of the first auxiliary satellite, and an initial calibration signal is generated based on the first calibration request; The calibration compensation module of the first auxiliary satellite applies digital amplitude, phase, and delay channel-level calibration to the initial calibration signal to obtain the first compensation signal; The digital beamforming network of the first auxiliary satellite applies corresponding phase weighting to the first compensation signal flowing through the channel by specifying the beam direction, and obtains the weighted signal; The digital-to-analog / analog-to-digital converter of the first auxiliary satellite is used to convert the weighted signal into a first analog signal; The radio frequency front-end of the first auxiliary satellite sequentially performs filtering, up-conversion, and amplification operations on the first analog signal to obtain the first calibration signal of radio frequency type; The phased array antenna of the first auxiliary satellite transmits the first calibration signal to the satellite to be calibrated via an air interface.

[0009] According to the present invention, a low-Earth orbit satellite digital phased array on-orbit calibration system is provided, wherein the ground control unit, when selecting and scheduling a first auxiliary satellite that meets the conditions based on the ephemeris and the first calibration request, is configured to: Based on the orbital prediction of the ephemeris and the first calibration request, if it is determined that at a future time t0, the distance between the satellite to be calibrated and the target satellite is less than a preset threshold and the inter-satellite perspective is good, then the target satellite is determined to be the first auxiliary satellite, and calibration instructions are issued to the satellite to be calibrated and the first auxiliary satellite respectively, specifying time t0 as the calibration execution time, so that the first auxiliary satellite can transmit the first calibration signal to the satellite to be calibrated at time t0.

[0010] According to the present invention, a low-Earth orbit satellite digital phased array on-orbit calibration system is provided, wherein when the first auxiliary satellite transmits a first calibration signal to the satellite to be calibrated based on the beam pointing angle, it is used to: Before time t0, the first auxiliary satellite calculates the beam pointing angle (θ, φ) pointing towards the satellite to be calibrated based on the first calibration request and real-time orbit parameters. At time t0, the digital beamforming network of the first auxiliary satellite loads the required phase weights for the beam pointing angle (θ, φ), and modulates the pre-stored calibration signal onto radio frequency via the main control unit of the first auxiliary satellite as the first calibration signal, and then transmits the first calibration signal directionally towards the satellite to be calibrated via the phased array antenna.

[0011] According to the present invention, a low-Earth orbit satellite digital phased array on-orbit calibration system is provided, assuming the channel measurement delay is t. k The amplitude-phase response includes the measured amplitude a k and measuring phase φ kThe first ideal DBF phase difference is transferred from the measured phase φ. k After removal, the obtained first channel-level error includes the first phase error Δφ. k Then, when the calibration compensation module of the satellite to be calibrated updates the receiving compensation parameters based on the first channel-level error, it is used to: Based on channel measurement delay t k Measurement amplitude a k and the first phase error Δφ k The compensation parameter set for the receiving channel is determined to be (1 / a). k , Δφ k , t k ), and utilize (1 / a k , Δφ k , t k Update the receive compensation parameters to prepare for subsequent digital signals entering the receive channel. k (t) are all according to the formula s' k (t) = (1 / a k ) s k (t + t k ) exp(j Real-time compensation is performed using Δφk) to correct the errors of each receiving channel of the satellite to be calibrated, where k represents the sequence number of the receiving channel.

[0012] The present invention provides an on-orbit calibration system for a low-Earth orbit satellite digital phased array. The main control unit of the satellite to be calibrated is used to monitor the launch performance of the satellite to be calibrated, and when the launch performance is detected to be degraded, it sends a second calibration request to the ground control unit. The ground control unit is used to receive the second calibration request, and select and schedule a second auxiliary satellite that meets the conditions according to the ephemeris and the second calibration request; The phased array antenna of the satellite to be calibrated is used to transmit a second calibration signal to the second auxiliary satellite through each channel after the second auxiliary satellite is in place; The second auxiliary satellite is used to receive the second calibration signal, and based on the second calibration signal, obtain the amplitude and phase delay information of each channel through cross-correlation and solution, and, based on the amplitude and phase delay information, calculate the second ideal DBF phase difference and extract the second channel-level error, and, through the inter-satellite communication module, transmit the second channel-level error back to the main control unit of the satellite to be calibrated; The calibration compensation module of the satellite to be calibrated is used to update the launch compensation parameters based on the second channel-level error and complete the launch channel calibration.

[0013] According to the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the present invention, the second auxiliary satellite, when used for extracting the second channel-level error, is specifically used for: The phased array antenna of the second auxiliary satellite receives the second calibration signal via an air interface; The radio frequency front-end of the second auxiliary satellite performs low-noise amplification, down-conversion, and filtering operations on the second calibration signal in sequence to obtain the second analog signal; The digital-to-analog / analog-to-digital converter of the second auxiliary satellite performs analog-to-digital conversion on the second analog signal to obtain a digital signal; The digital beamforming network of the second auxiliary satellite obtains the amplitude and phase delay information of each channel through cross-correlation and decomposition based on the direction of arrival and the digital signal, and calculates the second ideal DBF phase difference based on the amplitude and phase delay information; The calibration compensation module of the second auxiliary satellite performs channel-level compensation for amplitude, phase and delay on the second calibration signal based on the second ideal DBF phase difference to obtain the second compensation signal; The main control unit of the second auxiliary satellite analyzes and processes the second compensation signal to obtain the second channel-level error.

[0014] According to the present invention, a low-Earth orbit satellite digital phased array on-orbit calibration system is provided, wherein the given calibration signal is a ZC sequence or a cyclic shift variant of a ZC sequence or a broadband signal with autocorrelation characteristics.

[0015] The present invention also provides a method for applying the on-orbit calibration system of a low-Earth orbit satellite digital phased array as described above, comprising: Using the main control unit of the satellite to be calibrated, monitor whether the phased array channel parameters of the satellite to be calibrated have shifted. If so, send a calibration request to the ground control unit. The ground control unit selects and schedules target satellites that meet the conditions as auxiliary satellites according to the ephemeris and the calibration request, and controls the link between the auxiliary satellites and the satellite to be calibrated to transmit or receive a given calibration signal. The auxiliary satellites are used as calibration reference sources. Based on the given calibration signal, the digital beamforming network of the satellite to be calibrated or the auxiliary satellite is used to perform cross-correlation and least squares algorithm operations to obtain the measurement amplitude, measurement phase and measurement delay of each transceiver channel of the satellite to be calibrated; Based on the given calibration signal and the phased array element parameters of the satellite to be calibrated, the theoretical inter-channel phase difference introduced by the beamforming network of the satellite to be calibrated or the auxiliary satellite is removed from the measured phase to obtain the actual channel-level phase difference of each transmit and receive channel of the satellite to be calibrated. Based on the actual channel-level phase difference, the measurement amplitude, and the measurement delay, the calibration compensation module of the satellite to be calibrated is used to perform error compensation on each transmit and receive channel of the satellite to be calibrated, thereby achieving on-orbit calibration of the satellite to be calibrated.

[0016] The low-Earth orbit (LEO) satellite digital phased array on-orbit calibration system and the method for applying the system provided by this invention utilize the networking characteristics of the LEO satellite constellation itself. Through cooperation between LEO satellites, it achieves high-precision autonomous measurement and compensation of amplitude, phase and delay errors of the satellite phased array transmit and receive channels without the need for ground station participation or additional on-board dedicated calibration hardware. This enhances the autonomous survivability and on-orbit service reliability of the satellite system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments of this invention or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the on-orbit calibration system for a low-Earth orbit satellite digital phased array provided by the present invention; Figure 2 This is a schematic diagram illustrating the data flow during the calibration phase of the receiving channel in the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the present invention. Figure 3 A schematic diagram of the data flow during the launch channel calibration phase in the on-orbit calibration system for a low-Earth orbit satellite digital phased array provided by the present invention; Figure 4 A flowchart illustrating the method for applying the on-orbit calibration system for low-Earth orbit satellite digital phased arrays provided by this invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] This invention addresses the problems of existing technologies that rely on ground stations or dedicated onboard hardware, resulting in poor adaptability, low reliability, and inability to maintain accuracy over long periods. By leveraging the inherent network characteristics of low-Earth orbit (LEO) satellite constellations and through collaboration among LEO satellites, it achieves high-precision autonomous measurement and compensation of amplitude, phase, and delay errors in the onboard phased array transceiver channels without the need for ground station involvement or additional onboard calibration hardware. This enhances the satellite system's autonomous survivability and on-orbit service reliability. The invention will be further described and illustrated below with reference to the accompanying drawings and several specific embodiments.

[0021] like Figure 1 The diagram shown is a structural schematic of an on-orbit calibration system for a low-orbit satellite digital phased array provided by the present invention. The system includes a satellite to be calibrated 101, an auxiliary satellite 102, and a ground control unit 103 that are interconnected.

[0022] The satellite 101 to be calibrated includes: a phased array antenna, a radio frequency front-end, a digital-to-analog / analog-to-digital converter, a digital beamforming network, a calibration compensation module, and a main control unit; The auxiliary satellite 102 has the same phased array system structure as the satellite 101 to be calibrated, and the auxiliary satellite 102 is used to transmit or receive a given calibration signal during the process of cooperating to calibrate the satellite 101 to be calibrated. The ground control unit 103 is used to monitor the satellite status of the satellite 101 to be calibrated, determine the calibration conditions, and schedule the sending of calibration start commands. The calibration compensation module stores and applies the calculated error compensation parameters to perform pre-compensation or post-compensation on the amplitude, phase and delay of the digital signals transmitted or received through each channel of the satellite 101 to be calibrated.

[0023] In essence, the core of this invention lies in utilizing a normal satellite in a low-Earth orbit satellite network as an auxiliary satellite to provide calibration services for another satellite to be calibrated. The system includes the satellite to be calibrated 101, the auxiliary satellite 102, and a ground control unit 103. The calibration is divided into two stages: receiving channel calibration and transmitting channel calibration. By transmitting and receiving orthogonal broadband calibration signals, channel errors are extracted using cross-correlation and least squares algorithms, and digital compensation is performed.

[0024] The core components of the system include the satellite to be calibrated 101, the auxiliary satellite 102, and the ground control unit 103. The satellite to be calibrated 101 is mainly equipped with the phased array transceiver channel to be calibrated and an inter-satellite communication module. The phased array includes transceiver antennas, digital-to-analog converters and RF front-ends, a digital beamforming (DBF) network, a calibration compensation module, and a main control unit. The auxiliary satellite (calibration satellite) 102 has the same system structure as the satellite to be calibrated; any normally functioning satellite in a low-Earth orbit satellite network can serve as an auxiliary satellite. The ground control unit 103 is responsible for monitoring the satellite status, determining calibration conditions (such as inter-satellite distance and position, beam pointing offset), scheduling and sending calibration start commands. The calibration compensation module is used to perform digital amplitude, phase, and time delay compensation on the transmitted and received signals based on the measured channel errors. The calibration process is mainly divided into two stages: receive channel calibration and transmit channel calibration.

[0025] Optionally, both the satellite to be calibrated and the auxiliary satellite are low-Earth orbit communication satellites, and the phased array antenna is a two-dimensional planar array in the S-band or other communication bands.

[0026] The low-Earth orbit (LEO) satellite digital phased array on-orbit calibration system provided by this invention utilizes the networking characteristics of the LEO satellite constellation itself. Through cooperation between LEO satellites, it achieves high-precision autonomous measurement and compensation of amplitude, phase, and delay errors of the satellite phased array transmission and reception channels without the need for ground station participation or additional on-board dedicated calibration hardware. This enhances the autonomous survivability and on-orbit service reliability of the satellite system.

[0027] In the on-orbit calibration system for low-Earth orbit satellite digital phased arrays provided by the above embodiments, optionally, the main control unit of the satellite to be calibrated is used to monitor the received G / T value, and when the received G / T value is detected to be lower than a preset threshold, sends a first calibration request to the ground control unit; the ground control unit is used to receive the first calibration request, and select and schedule a first auxiliary satellite that meets the conditions according to the ephemeris and the first calibration request; the first auxiliary satellite is used to calculate the beam pointing angle according to the first calibration request, and transmit a first calibration signal to the satellite to be calibrated based on the beam pointing angle; the phased array antenna of the satellite to be calibrated is used to receive the first calibration signal, and transmit the first calibration signal to the radio frequency front end through each channel of the satellite to be calibrated. The radio frequency front-end of the satellite to be calibrated is used to down-convert the first calibration signal to obtain an intermediate frequency (IF) signal. The digital-to-analog (DAC) / analog-to-digital (ADC) of the satellite to be calibrated is used to perform analog-to-digital conversion on the IF signal to obtain a digital baseband signal. The digital beamforming network of the satellite to be calibrated is used to calculate the measurement delay of each channel based on the digital baseband signal by cross-correlation, and to calculate the amplitude and phase response by least squares. Based on the channel measurement delay and the amplitude and phase response, combined with the incident direction and the array element position, the first ideal DBF phase difference is calculated, and the first ideal DBF phase difference is discarded to obtain the first channel-level error. The calibration compensation module of the satellite to be calibrated is used to update the receiving compensation parameters based on the first channel-level error to complete the receiving channel calibration.

[0028] This embodiment can be understood as primarily used to calibrate the receiving channels of the satellite to be calibrated. It achieves efficient calibration of the receiving channels by rationally utilizing the components of the satellite, the ground control unit, and the auxiliary satellite (referred to as the first auxiliary satellite). For example... Figure 2 The diagram shown illustrates the data flow during the calibration phase of the receiving channel in the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the present invention.

[0029] First, the master control unit of the satellite to be calibrated periodically or in real time monitors the received G / T value of the receiving channel to monitor the receiving status of the satellite. If the received G / T value is detected to be lower than a preset threshold, a calibration request is sent to the ground control unit through the master control unit, which is called the first calibration request.

[0030] After receiving the first calibration request, the ground control unit determines whether the distance between the target satellite and the satellite to be calibrated meets the link budget based on the ephemeris. If it does, the target satellite is scheduled as an auxiliary satellite, referred to as the first auxiliary satellite.

[0031] After the first auxiliary satellite is in place, it transmits a given calibration signal, such as a ZC sequence calibration signal, to the satellite to be calibrated based on the calculated beam pointing angle. This is called the first calibration signal.

[0032] Next, the satellite to be calibrated receives the first calibration signal through the phased array antenna and transmits the first calibration signal through each channel. Then, the first calibration signal is down-converted and converted from analog to digital using the radio frequency front-end and digital-to-analog / analog-to-digital converter of the satellite to be calibrated to obtain a digital baseband signal.

[0033] The digital baseband signal flows through the digital beamforming network (DBF) of the satellite to be calibrated. The measurement delay of each channel is obtained through cross-correlation calculations using the DBF network, and the amplitude and phase response is calculated using least squares. Based on this, the DBF network calculates the ideal DBF phase difference according to the incident direction and array element position, called the first ideal DBF phase difference, and removes it from the measurement phase in the amplitude and phase response to obtain the channel-level error, called the first channel-level error.

[0034] Finally, the calibration compensation module of the satellite to be calibrated obtains the first channel-level error from the DBF network and updates the calibration compensation module parameters based on it to complete the receiving channel calibration.

[0035] Optionally, in the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the above embodiments, when the first auxiliary satellite transmits the first calibration signal to the satellite to be calibrated, it is specifically used for: obtaining the first calibration request through the main control unit of the first auxiliary satellite, and generating an initial calibration signal based on the first calibration request; the calibration compensation module of the first auxiliary satellite applying digital amplitude, phase, and delay channel-level calibration to the initial calibration signal to obtain a first compensation signal; the digital beamforming network of the first auxiliary satellite applying corresponding phase weighting to the first compensation signal flowing through the channel through a specified beam direction to obtain a weighted signal; the digital-to-analog / analog-to-digital converter of the first auxiliary satellite converting the weighted signal into a first analog signal; the radio frequency front-end of the first auxiliary satellite sequentially performing filtering, up-conversion, and amplification operations on the first analog signal to obtain the first calibration signal of radio frequency type; and the phased array antenna of the first auxiliary satellite transmitting the first calibration signal to the satellite to be calibrated through an air interface.

[0036] This can be understood as follows: during the calibration process of each receiving channel of the satellite to be calibrated in the above embodiments, the auxiliary satellite, i.e., the first auxiliary satellite, also participates in signal transmission and calculation when transmitting the first calibration signal to the satellite to be calibrated. Specifically, as shown in Figure 2, the main control unit first obtains the first calibration request and calibration command from the ground control unit, and generates or extracts the initial calibration signal based on this. Then, the initial calibration signal flows out from the main control unit. When the initial calibration signal flows through the calibration compensation module, it is subjected to digital amplitude, phase, and delay channel-level calibration, and the resulting signal is called the first compensation signal. After that, the first compensation signal passes through the DBF network. The DBF network applies corresponding phase weighting to the channel signal flowing through it by specifying the beam direction, and the resulting signal is called the weighted signal.

[0037] The weighted signal obtained after DBF weighting is converted into an analog signal by a digital-to-analog converter, which is called the first analog signal. Then, the first analog signal undergoes filtering, up-conversion, and amplification by the RF front-end to obtain the RF signal, which is called the first calibration signal. Finally, the RF signal is transmitted from the air interface through the transmitting antenna of the first auxiliary satellite.

[0038] Optionally, in the low-orbit satellite digital phased array on-orbit calibration system provided by the above embodiments, when the ground control unit selects and schedules a first auxiliary satellite that meets the conditions based on the ephemeris and the first calibration request, it is configured to: determine, based on the orbit prediction of the ephemeris and the first calibration request, that at a future time t0, the distance between the satellite to be calibrated and the target satellite is less than a preset threshold and the inter-satellite angle is good, then determine the target satellite as the first auxiliary satellite, and issue calibration instructions to the satellite to be calibrated and the first auxiliary satellite respectively, specifying time t0 as the calibration execution time, so that the first auxiliary satellite can transmit the first calibration signal to the satellite to be calibrated at time t0.

[0039] This invention can be understood as follows: by transmitting information between the master control unit of the satellite to be calibrated and the ground control unit, the calibration triggering and scheduling of the receiving channel of the satellite to be calibrated is realized. Specifically, the master control unit of the satellite to be calibrated periodically or in real time monitors the received G / T value of the receiving channel and determines whether the receiving channel of the satellite to be calibrated has deviated based on this value. When the received signal G / T value is continuously lower than a preset threshold, such as 90% of the theoretical value (i.e., weight w=0.9), it is determined that receiving calibration is required. This calibration request is reported to the ground control unit through the active unit. Based on the orbit prediction, the ground control unit finds that at a certain time t0 in the future, the distance between the satellite to be calibrated and the target satellite is about 80 kilometers, which meets the minimum distance d_min requirement and the viewing angle is good. Then, the target satellite is determined as the auxiliary satellite for receiving channel calibration. Afterwards, the ground control unit issues calibration instructions to the two satellites (the satellite to be calibrated and the target satellite), specifying t0 as the calibration execution time. After receiving the calibration instructions from the ground control unit, the auxiliary satellite transmits a given calibration signal to the satellite to be calibrated at time t0, which can be called the first calibration signal.

[0040] Optionally, in the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the above embodiments, when the first auxiliary satellite transmits a first calibration signal to the satellite to be calibrated based on the beam pointing angle, it performs the following: before time t0, the first auxiliary satellite calculates the beam pointing angle (θ, φ) pointing to the satellite to be calibrated based on the first calibration request and real-time orbit parameters. At time t0, the digital beamforming network of the first auxiliary satellite loads the phase weight required for the beam pointing angle (θ, φ), and modulates the pre-stored calibration signal onto radio frequency through the main control unit of the first auxiliary satellite as the first calibration signal, and transmits the first calibration signal directionally to the satellite to be calibrated via the phased array antenna.

[0041] This can be understood as follows: after the scheduling of the auxiliary satellites is completed, that is, after the calibration command is determined and sent to the first auxiliary satellite, the first auxiliary satellite calculates the beam pointing angle (θ, φ) pointing to the satellite to be calibrated before time t0, based on the real-time orbit parameters and the first calibration request. At time t0, the digital beamforming network (DBF) of the first auxiliary satellite loads the phase weight required for this pointing and modulates the pre-stored reference calibration signal x1(t) onto the radio frequency via the main control unit, and then transmits it directionally to the satellite to be calibrated via the phased array antenna. Optionally, the given calibration signal can be a ZC sequence or a cyclic shift variant of a ZC sequence or a broadband signal with autocorrelation characteristics, in which case the reference calibration signal x1(t) can be a reference ZC sequence.

[0042] In the on-orbit calibration system for low-Earth orbit satellite digital phased arrays provided in the above embodiments, it is optionally assumed that the channel measurement delay is t.k The amplitude-phase response includes the measured amplitude a k and measuring phase φ k The first ideal DBF phase difference is transferred from the measured phase φ. k After removal, the obtained first channel-level error includes the first phase error Δφ. k Then, when the calibration compensation module of the satellite to be calibrated updates the receiving compensation parameters based on the first channel-level error, it is used to: based on the channel measurement delay t k Measurement amplitude a k and the first phase error Δφ k The compensation parameter set for the receiving channel is determined to be (1 / a). k , Δφ k , t k ), and utilize (1 / a k , Δφ k , t k Update the receive compensation parameters to prepare for subsequent digital signals entering the receive channel. k (t) are all according to the formula s' k (t) = (1 / a k ) s k (t + t k ) exp(j Real-time compensation is performed using Δφk) to correct the errors of each receiving channel of the satellite to be calibrated, where k represents the sequence number of the receiving channel.

[0043] This invention can be understood as follows: for ease of description, the specific parameters in the calculation process are defined using variables. Specifically, the relevant peak position τ is searched through cross-correlation calculation. k This value is the measurement delay t of this channel. k Then the reference calibration signal x1(t) is delayed by t. k , and the received signal y k (t) The LS equations are constructed as follows: x1(tt k ) h k = y k (t).

[0044] By solving the above LS equation, the complex coefficients h are obtained. k The modulus a of this coefficient k = abs(h k This refers to the channel amplitude, and the argument φ. k = angle(h k This refers to the measurement phase, which includes the error and the DBF phase.

[0045] Next, the measured phase φ obtained in the above steps is... k Subtracting the theoretical phase (i.e., the ideal DBF phase) yields the pure phase error of the receiving channel, which is called the first phase error Δφ. k Ultimately, the compensation parameter set for this channel is (1 / a) k , Δφ k , t k Update this parameter set to the calibration compensation module of the receiving channel. Afterwards, all digital signals entering this channel... k (t) will all be calculated according to the formula s'_k(t) = (1 / a k ) s k (t + t k ) exp(j Δφ k Real-time compensation is performed to correct the error in the receiving channel.

[0046] In the on-orbit calibration system for low-Earth orbit satellite digital phased arrays provided in the above embodiments, optionally, the main control unit of the satellite to be calibrated is used to monitor the launch performance of the satellite to be calibrated, and when a decrease in launch performance is detected, sends a second calibration request to the ground control unit; the ground control unit is used to receive the second calibration request, and select and schedule a second auxiliary satellite that meets the conditions according to the ephemeris and the second calibration request; the phased array antenna of the satellite to be calibrated is used to transmit a second calibration signal to the second auxiliary satellite through each channel after the second auxiliary satellite is in place; the second auxiliary satellite is used to receive the second calibration signal, and based on the second calibration signal, obtain the amplitude and phase delay information of each launch channel through cross-correlation and solution, and calculate the second ideal DBF phase difference and extract the second channel-level error based on the amplitude and phase delay information, and transmit the second channel-level error back to the main control unit of the satellite to be calibrated through the inter-satellite communication module; the calibration compensation module of the satellite to be calibrated is used to update the launch compensation parameters based on the second channel-level error to complete the launch channel calibration.

[0047] This embodiment can be understood as primarily used to calibrate the various launch channels of the satellite to be calibrated. By rationally utilizing the components of the satellite to be calibrated, the ground control unit, and the auxiliary satellite (referred to as the second auxiliary satellite), efficient calibration of the launch channels of the satellite to be calibrated is achieved. For example... Figure 3 The diagram shown illustrates the data flow during the launch channel calibration phase of the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the present invention.

[0048] First, the master control unit of the satellite to be calibrated periodically or in real time monitors the launch performance of the launch channel to monitor the launch status of the satellite. If a degradation in launch performance is detected, a calibration request, known as a second calibration request, is sent from the master control unit to the ground control unit.

[0049] After receiving the second calibration request, the ground control unit determines whether the distance between the target satellite and the satellite to be calibrated meets the link budget based on the ephemeris. If it does, the target satellite is scheduled as an auxiliary satellite, referred to as the second auxiliary satellite.

[0050] After the second auxiliary satellite is in place, the phased array antenna of the satellite to be calibrated transmits a given calibration signal, such as a ZC sequence calibration signal, to the satellite based on the calculated beam pointing angle. This is called the second calibration signal.

[0051] Subsequently, the second auxiliary satellite receives the second calibration signal through the phased array antenna, and performs cross-correlation calculations based on the second calibration signal to obtain the measurement delay of each transmission channel. It then calculates the amplitude and phase response using least squares, calculates the ideal DBF phase difference based on the amplitude and phase response, and extracts the transmission channel error of the satellite to be calibrated. Finally, it transmits the transmission channel error back to the satellite to be calibrated through the inter-satellite link.

[0052] Finally, the calibration compensation module of the satellite to be calibrated updates the parameters of the calibration compensation module based on the received transmission channel error, and completes the transmission channel calibration.

[0053] Optionally, in the low-Earth orbit satellite digital phased array on-orbit calibration system provided by the above embodiments, the second auxiliary satellite, when used for extracting the second channel-level error, specifically performs the following: the phased array antenna of the second auxiliary satellite receives the second calibration signal through an air interface; the radio frequency front-end of the second auxiliary satellite sequentially performs low-noise amplification, down-conversion, and filtering operations on the second calibration signal to obtain a second analog signal; the digital-to-analog / analog-to-digital converter of the second auxiliary satellite performs analog-to-digital conversion on the second analog signal to obtain a digital signal; the digital beamforming network of the second auxiliary satellite obtains the amplitude and phase delay information of each channel through cross-correlation and decomposition based on the direction of arrival and the digital signal, and calculates the second ideal DBF phase difference based on the amplitude and phase delay information; the calibration compensation module of the second auxiliary satellite performs channel-level compensation of amplitude, phase, and delay on the second calibration signal based on the second ideal DBF phase difference to obtain a second compensation signal; and the main control unit of the second auxiliary satellite analyzes and processes the second compensation signal to obtain the second channel-level error.

[0054] This can be understood as follows: during the calibration process of each transmission channel of the satellite to be calibrated in the above embodiments, when the satellite to be calibrated transmits calibration signals to the second auxiliary satellite, its various components also participate in signal transmission and calculation. Specifically, as follows: Figure 3 As shown, the direction of the received calibration data flow is the opposite of that of the transmitted data: First, the air interface incoming signal, i.e. the second calibration signal, is received from the antenna port of the second auxiliary satellite.

[0055] The second calibration signal undergoes low-noise amplification, down-conversion, and filtering at the RF front-end of the second auxiliary satellite, resulting in a second analog signal. This second analog signal is then converted to a digital signal via analog-to-digital conversion by the second auxiliary satellite. After the digital signal is processed by a DBF network with phase weighting based on the direction of arrival, it flows to the calibration compensation module for channel-level compensation of amplitude, phase, and delay, resulting in the second compensated signal. Finally, the second compensated signal flows to the main control unit of the second auxiliary satellite for analysis and processing, generating a second channel-level error that is then fed back to the satellite to be calibrated.

[0056] This invention utilizes an auxiliary satellite in a low-Earth orbit (LEO) satellite constellation as a far-field reference source or receiving measurement device. Without ground station support, it autonomously measures and compensates for amplitude, phase, and delay in the phased array receiving and transmitting channels of the satellite to be calibrated via inter-satellite links. This invention eliminates dependence on ground infrastructure, enhances the autonomous operation capability and on-orbit maintenance efficiency of the satellite constellation, and boasts advantages such as high autonomy, strong real-time performance, simplified structure, and low cost. It is suitable for long-term on-orbit maintenance and performance assurance of LEO satellite constellations.

[0057] To further illustrate the technical solution of the present invention, the following description uses an S-band low-orbit communication satellite as an example for more detailed explanation, but does not limit the scope of protection claimed by the present invention.

[0058] This invention relates to a collaborative calibration system for S-band low-Earth orbit communication satellites, comprising: Satellite to be calibrated (Satellite A): Equipped with a complete phased array transceiver system, inter-satellite communication module and core digital processing unit (including DBF network and calibration compensation module).

[0059] Auxiliary satellite (Satellite B): Any normal operating satellite in the constellation that can be used as a calibration reference, with the same system configuration as the satellite to be calibrated.

[0060] Ground control unit: responsible for constellation status monitoring, calibration condition (inter-satellite visibility, distance) judgment, and calibration task scheduling and command issuance.

[0061] For the above calibration system, the overall system parameters need to be set before application.

[0062] Satellite platform: Both the satellite to be calibrated and the auxiliary satellite are low-Earth orbit communication satellites with an orbital altitude of approximately 500 km, equipped with S-band phased array antennas and inter-satellite link communication capabilities.

[0063] Phased array: The antenna array is a 16×16 two-dimensional planar array with a total of 256 elements. The element spacing dc is set to half the operating wavelength, which is approximately 71.4 mm at the center frequency of 2.1 GHz.

[0064] Signal Design: The calibration signal uses a ZC sequence of length 8191 with a root sequence number of 1. This sequence has ideal periodic autocorrelation and a low peak-to-average power ratio. For transmit calibration, a set of 256 mutually orthogonal sequences are generated by cyclically shifting the basic ZC sequence with different numbers of sampling points. These sequences are emitted from the 256 transmit channels respectively, allowing for channel separation at the receiver.

[0065] Link budget: The receiver sensitivity RP_min is set to -110 dBm, the transmit power Pt to 20 dBm, and the transmit / receive antenna gains Gt / Gr to 30 dBi. The operating frequency F is 2100 MHz. Based on the free space loss formula Lp = 32.44 + 20lg(d) + 20lg(F) and the link equation RP_min = Pt + Gt + Gr - Lp, the minimum inter-satellite cooperation distance d_min required for calibration can be calculated to be approximately 100 km. The ground control unit predicts and selects a time when the satellite distance is less than d_min and the relative geometry is suitable, based on the satellite's precise ephemeris, to initiate calibration.

[0066] Secondly, the receiving channel calibration is implemented, including: Triggering and Scheduling: The master control unit of the satellite to be calibrated detects that the received signal G / T value is consistently below 90% of the theoretical value (i.e., weight w=0.9), and determines that reception calibration is required. This request is reported to the ground control unit. Based on orbit prediction, the ground control unit finds that at a future time t0, the distance between satellite A (to be calibrated) and satellite B (auxiliary) will be approximately 80 kilometers, meeting the d_min requirement, and the viewing angle is good. Therefore, calibration instructions are issued to both satellites, specifying t0 as the calibration execution time.

[0067] Signal transmission: Before time t0, auxiliary satellite B calculates the beam pointing angle (θ, φ) pointing to satellite A based on real-time orbital parameters. At time t0, its DBF network loads the phase weights required for this pointing and modulates the pre-stored reference ZC sequence x1(t) onto the radio frequency via the main control unit, and transmits it directionally to satellite A via the phased array antenna.

[0068] Signal reception and acquisition: Satellite A pre-sets its receiving beam to wide-beam mode to simultaneously receive signals from all array elements. Each receiving channel synchronously receives calibration signals from Satellite B. After low-noise amplification, down-conversion, filtering, and analog-to-digital conversion, 256 digital baseband signals yk(t), k=1,2,…,256, are obtained and buffered in memory.

[0069] Channel error measurement: For each channel k, calculate its received signal y. k The cross-correlation function Rxy_k(t) between x1(t) and the local reference sequence x1(t) is as follows: ; In the formula, This indicates that cross-correlation calculations are being performed. x 1( t () represents a digital baseband signal. This indicates the received and acquired signals of each receiving channel. t Representing the independent variable of time, Indicates time delay. k This indicates the channel number of the satellite to be calibrated.

[0070] Search for relevant peak positions τ k This value is the measurement delay t of this channel. k Then delay x1(t) by t. k , and y k (t) Construct the LS equation: x1(tt) k ) h k = y k (t), solve for the complex coefficients h k The modulus a of this coefficient k = abs(h k This refers to the channel amplitude, and the argument φ. k = angle(h k This refers to the measurement phase, which includes the error and the DBF phase.

[0071] DBF theoretical phase calculation: Based on the incident angles (θ, φ) obtained in the above steps, and the coordinates (m, n) of each element in the array, the ideal DBF phase is calculated using the path difference formula: Ø_theory_k = - (dc / (c / F)) 2π sin(θ) [(m-1)cos(φ) + (n-1)sin(φ)].

[0072] In the formula, Indicates the spacing between array elements (unit: mm). Indicates the signal frequency (unit: GHz).

[0073] Error extraction and compensation: The measured phase φ obtained in the above steps is... k Subtracting the theoretical phase Ø_theory_k, we obtain the pure phase error Δφ of the receiving channel. k Ultimately, the compensation parameter set for this channel is (1 / a) k , Δφ k , t k Update this parameter set to the calibration compensation module of the receiving channel. Afterwards, all digital signals entering this channel... k (t) will be calculated according to the formula s'_k(t) = (1 / a k ) s k (t + t k ) exp(j Δφ k Real-time compensation is performed to correct channel errors.

[0074] Next, the launch channel calibration will be implemented, including: Triggering and Scheduling: Similar to receiver calibration, a decrease in the launch performance of satellite A to be calibrated is detected by the ground station or a neighboring satellite, triggering the launch calibration process. The ground control unit schedules satellite B as an auxiliary measurement satellite and issues commands within the appropriate time window t1.

[0075] Orthogonal signal transmission: At time t1, satellite A master control unit generates 256 mutually orthogonal transmission calibration sequences x. k (t) (generated by cyclic shifting of the basic ZC sequence). After the DBF network loads the theoretical phase weight Ø1_theory_k according to the beam pointing angle (θ1, φ1) pointing to satellite B, each channel synchronously transmits its own calibration signal.

[0076] Auxiliary satellite measurements: Satellite B receives signals from Satellite A using a wide beam. Utilizing each x k (t) The orthogonality between the sequences is used to separate the signal components from different transmission channels of satellite A from the mixed signal through matched filtering or correlation processing. For each separated signal component, the amplitude a of the k-th transmission channel of satellite A at satellite B is measured using the same method as in the receive calibration step S204. 1k Measure the phase φ 1k and measurement delay t 1k .

[0077] Error Calculation and Transmission: Satellite B calculates the DBF theoretical phase φ1_theory_k based on the known incoming wave direction (θ1, φ1). The measured phase φ... 1kSubtracting φ1_theory_k yields the pure phase error Δφ of satellite A's transmission channel. 1k Satellite B will transmit error data from all 256 channels (a 1k , Δφ 1k , t 1k The data is packaged and sent back to satellite A via an inter-satellite link.

[0078] Error loading: After receiving the error data packet, satellite A will load the compensation parameter group (1 / a) of the transmission channel. 1k , Δφ 1k ,t 1k Update the calibration compensation module to the transmit channel. Afterwards, all digital signals to be transmitted from this channel... k (t) will be calculated according to the formula s'_k(t) = s k (t - t 1k ) a 1k exp(-j Δφ 1k Pre-compensation is performed before the data is sent to the DBF network and RF link to achieve error correction of the transmission channel.

[0079] This invention utilizes an auxiliary satellite as a far-field reference source. By transmitting and receiving calibration signals, it completes the error measurement and compensation of the receiving and transmitting channel parameters of the satellite to be calibrated, respectively. It eliminates the dependence on ground feedback channels, enabling calibration to be completed through inter-satellite cooperation even in areas without ground station coverage or when ground systems fail, greatly enhancing the on-orbit survivability and service continuity of the satellite system.

[0080] Based on the same inventive concept, this invention also provides a method for applying the above-described low-Earth orbit (LEO) satellite digital phased array on-orbit calibration systems according to the above embodiments. This method achieves on-orbit calibration of the satellite digital phased array by applying the systems described in the above embodiments. Therefore, the descriptions and definitions in the LEO satellite digital phased array on-orbit calibration systems of the above embodiments can be used to understand the steps in the method of this invention. For details, please refer to the above system embodiments, which will not be repeated here.

[0081] According to an embodiment of the present invention, the steps of the method for applying the on-orbit calibration system of the low-Earth orbit satellite digital phased array of the present invention are as follows: Figure 4 The diagram shown is a flowchart illustrating a method for applying the low-Earth orbit (LEO) satellite digital phased array on-orbit calibration system provided by this invention. This method utilizes the LEO satellite digital phased array on-orbit calibration system described in the above system embodiments to achieve on-orbit calibration of a LEO digital phased array. The method includes: S401, using the main control unit of the satellite to be calibrated, monitor whether the phased array channel parameters of the satellite to be calibrated have shifted. If so, send a calibration request to the ground control unit.

[0082] It can be understood that the core of this invention is: based on a network of low-orbit satellites, under certain conditions (such as when the inter-satellite distance meets the link budget requirements), triggered by ground commands or initiated autonomously by the satellite, one of the satellites (referred to as the "auxiliary satellite" or "calibration satellite") is used as a known far-field signal source or signal receiving measurement device to provide calibration services for another miscalibrated satellite, hereinafter referred to as the satellite to be calibrated, and the calibration of the receiving channel and the transmitting channel are completed respectively.

[0083] This step involves calibration triggering and condition judgment: First, the main control unit of the satellite to be calibrated monitors its status in real time. The monitoring targets include the phased array channel parameters of the satellite, such as the direction of the phased array receiving beam. If a deviation in the phased array channel parameters is detected, the calibration process is triggered, and a calibration request is sent to the ground control unit.

[0084] For example, the main control unit can calculate the received signal G / T value to determine if recalibration is needed if the G / T value is lower than the expected value for a certain weight. The real-time calculated G / T value is denoted as... (Unit: dB), expected value is denoted as (Unit: dB), weight w (value (0-1, can be adjusted according to actual needs), judgment criteria are: .

[0085] When the above formula is true, recalibration is required, and the calibration command is sent to the ground control unit.

[0086] S402, the ground control unit selects and schedules a target satellite that meets the conditions as an auxiliary satellite according to the ephemeris and the calibration request, and controls the link between the auxiliary satellite and the satellite to be calibrated to transmit or receive a given calibration signal, wherein the auxiliary satellite is used as a calibration reference source.

[0087] This can be understood as follows: upon receiving a calibration request from the satellite to be calibrated, the ground control unit begins to detect whether there are any satellites in orbit that meet the requirements. If so, the satellite that meets the requirements is designated as an auxiliary satellite and used as a reference source for calibration, and the scheduling is completed. After scheduling is completed, the ground control unit transmits calibration commands to the satellite to be calibrated and the auxiliary satellite. The satellite to be calibrated then performs a service switch and sets its status to receive calibration mode.

[0088] For example, the ground control unit can determine whether the inter-satellite distance between the target satellite and the satellite to be calibrated meets the link budget requirements by calculating path loss and judging the received signal level. If it does, the target satellite is determined to be a satellite that meets the conditions and is used as an auxiliary satellite.

[0089] After the auxiliary satellite enters its expected orbital position, if the calibration is for the receiving channel, the phased array antenna of the auxiliary satellite will directionally transmit a calibration signal with known characteristics to the satellite to be calibrated, based on a preset beam pointing (the off-axis and azimuth angle of which are calculated from the orbital parameters of the two satellites and fed into the beamforming DBF network). Each receiving element of the phased array antenna of the satellite to be calibrated receives the incident calibration signal, and the entire array receiving channel simultaneously receives the signal, performs down-conversion and analog-to-digital conversion to obtain and store the digital baseband signal for each channel. If the calibration is for the transmitting channel, the satellite to be calibrated will send a calibration signal to the auxiliary satellite.

[0090] S403, based on the given calibration signal, the corresponding digital beamforming network of the satellite to be calibrated or the auxiliary satellite is used to perform cross-correlation and least squares algorithm operations to obtain the measurement amplitude, measurement phase and measurement delay of each transceiver channel of the satellite to be calibrated.

[0091] This step can be understood as follows: in the calibration of the receiving channel or the transmitting channel, the digital beamforming network of the satellite to be calibrated or the auxiliary satellite is used to process the digital signals acquired by each channel of the satellite to be calibrated through cross-correlation and the LS algorithm, and to calculate the amplitude, phase, and delay differences of each channel, that is, the measurement amplitude, measurement phase, and measurement delay of each transmitting and receiving channel of the satellite to be calibrated. The differences include channel error and beamforming DBF phase difference.

[0092] S404, based on the given calibration signal and the phased array element parameters of the satellite to be calibrated, the theoretical inter-channel phase difference introduced by the beamforming network is removed from the measured phase using the digital beamforming network of the satellite to be calibrated or the auxiliary satellite, and the actual channel-level phase difference of each transmit and receive channel of the satellite to be calibrated is obtained.

[0093] This can be understood as follows: based on the calculated measured values ​​and the ideal DBF phase difference obtained according to the above steps, and based on the phased array element parameters of the satellite to be calibrated, the DBF phase difference, i.e., the theoretical inter-channel phase difference introduced by the beamforming network, is removed from the calculated measured values ​​to obtain the amplitude, phase, and delay errors of the calibration channel, i.e., the actual channel-level phase difference of each transmit and receive channel. Specifically, in the receive channel calibration, the theoretical channel phase difference is removed using the DBF network of the satellite to be calibrated; in the transmit channel calibration, the theoretical channel phase difference is removed using the DBF network of the auxiliary satellite.

[0094] In other words, during the receive channel calibration phase, based on the incident direction of the auxiliary satellite signal and the geometric position of each receiving array element, the theoretical inter-channel phase difference that the digital beamforming network should apply under ideal conditions is calculated; the measured phase is then subtracted from the theoretical inter-channel phase difference to obtain the pure phase error of the receive channel. During the transmit channel calibration phase, based on the known incoming wave direction and the geometric position of each transmit array element, the auxiliary satellite calculates the theoretical inter-channel phase difference that the DBF network should apply under ideal conditions; the measured phase is then subtracted from the theoretical inter-channel phase difference to obtain the pure phase error of the transmit channel.

[0095] It should be understood that the measured values ​​calculated in the above embodiments include channel-level errors and DBF phase differences. According to the above embodiments, the DBF phase difference is removed from the measured values ​​to obtain the calibration channel amplitude, phase, and delay errors. The phase difference parameter is the measurement phase difference calculated during calibration. Subtract the ideal phase difference calculated by DBF above. .

[0096] S405, based on the actual channel-level phase difference, the measurement amplitude, and the measurement delay, the calibration compensation module of the satellite to be calibrated is used to perform error compensation on each transmit and receive channel of the satellite to be calibrated, thereby achieving on-orbit calibration of the satellite to be calibrated.

[0097] This invention can be understood as follows: after calculating the actual channel-level phase difference of each transceiver channel according to the above steps, the present invention combines the measurement amplitude and measurement delay calculated in step S403 to construct the error compensation parameters for the transceiver channels. In the receiving channel calibration, the satellite to be calibrated directly updates the error compensation parameters to its calibration compensation module to update the transceiver signals and compensate for errors in each transceiver channel. In the transmitting channel calibration, the auxiliary satellite sends the error compensation parameters of the transmitting channel back to the satellite to be calibrated via an inter-satellite link, allowing the satellite to update its calibration compensation module, thereby achieving on-orbit calibration. The low-Earth orbit (LEO) satellite digital phased array on-orbit calibration method provided by this invention utilizes the networking characteristics of the LEO satellite constellation itself. Through cooperation between LEO satellites, it achieves high-precision autonomous measurement and compensation of amplitude, phase, and delay errors of the onboard phased array transceiver channels without the need for ground station involvement or additional onboard dedicated calibration hardware, thereby improving the autonomous survivability and on-orbit service reliability of the satellite system.

[0098] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a USB flash drive, mobile hard drive, ROM, RAM, magnetic disk, or optical disk, etc., and includes several instructions to cause a computer device (such as a personal computer, server, or network device, etc.) to execute the methods described in the above method embodiments or some parts of the method embodiments.

[0099] Furthermore, those skilled in the art should understand that in the application documents of this invention, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0100] Numerous specific details are set forth in this specification. However, it should be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification. Similarly, it should be understood that, in order to simplify the disclosure of this invention and aid in the understanding of one or more aspects of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An on-orbit calibration system for a low-Earth orbit satellite digital phased array, characterized in that, This includes the satellites to be calibrated, auxiliary satellites, and ground control units that are interconnected; The satellite to be calibrated includes: a phased array antenna, a radio frequency front-end, a digital-to-analog / analog-to-digital converter, a digital beamforming network, a calibration compensation module, and a main control unit; The auxiliary satellite has the same phased array system structure as the satellite to be calibrated, and is used to transmit or receive a given calibration signal during the process of collaboratively calibrating the satellite to be calibrated. The ground control unit is used to monitor the satellite status of the satellite to be calibrated, determine the calibration conditions, and schedule the sending of calibration start commands. The calibration compensation module stores and applies the calculated error compensation parameters to perform pre-compensation or post-compensation on the amplitude, phase and delay of the digital signals transmitted or received through each channel of the satellite to be calibrated.

2. The low-orbit satellite digital phased array on-orbit calibration system according to claim 1, characterized in that: The main control unit of the satellite to be calibrated is used to monitor the received G / T value, and when the received G / T value is detected to be lower than a preset threshold, it sends a first calibration request to the ground control unit. The ground control unit is used to receive the first calibration request, and select and schedule the first auxiliary satellite that meets the conditions according to the ephemeris and the first calibration request; The first auxiliary satellite is used to calculate the beam pointing angle according to the first calibration request, and based on the beam pointing angle, transmit a first calibration signal to the satellite to be calibrated; The phased array antenna of the satellite to be calibrated is used to receive the first calibration signal and transmit the first calibration signal to the radio frequency front end through each channel of the satellite to be calibrated; The radio frequency front end of the satellite to be calibrated is used to down-convert the first calibration signal to obtain an intermediate frequency signal; The digital-to-analog / analog-to-digital converter of the satellite to be calibrated is used to perform analog-to-digital conversion processing on the intermediate frequency signal to obtain a digital baseband signal; The digital beamforming network of the satellite to be calibrated is used to calculate the measurement delay of each channel by cross-correlation based on the digital baseband signal, and to calculate the amplitude and phase response by least squares. Based on the channel measurement delay and the amplitude and phase response, combined with the incident direction and the array element position, the first ideal DBF phase difference is calculated, and the first ideal DBF phase difference is discarded to obtain the first channel-level error. The calibration compensation module of the satellite to be calibrated is used to update the receiving compensation parameters based on the first channel-level error, and complete the receiving channel calibration.

3. The low-orbit satellite digital phased array on-orbit calibration system according to claim 2, characterized in that, When the first auxiliary satellite transmits the first calibration signal to the satellite to be calibrated, it is specifically used for: The first calibration request is obtained by the main control unit of the first auxiliary satellite, and an initial calibration signal is generated based on the first calibration request; The calibration compensation module of the first auxiliary satellite applies digital amplitude, phase, and delay channel-level calibration to the initial calibration signal to obtain the first compensation signal; The digital beamforming network of the first auxiliary satellite applies corresponding phase weighting to the first compensation signal flowing through the channel by specifying the beam direction, and obtains the weighted signal; The digital-to-analog / analog-to-digital converter of the first auxiliary satellite is used to convert the weighted signal into a first analog signal; The radio frequency front-end of the first auxiliary satellite sequentially performs filtering, up-conversion, and amplification operations on the first analog signal to obtain the first calibration signal of radio frequency type; The phased array antenna of the first auxiliary satellite transmits the first calibration signal to the satellite to be calibrated via an air interface.

4. The low-orbit satellite digital phased array on-orbit calibration system according to claim 2, characterized in that, When the ground control unit is used to select and schedule a first auxiliary satellite that meets the conditions based on the ephemeris and the first calibration request, it is used to: Based on the orbital prediction of the ephemeris and the first calibration request, if it is determined that at a future time t0, the distance between the satellite to be calibrated and the target satellite is less than a preset threshold and the inter-satellite perspective is good, then the target satellite is determined to be the first auxiliary satellite, and calibration instructions are issued to the satellite to be calibrated and the first auxiliary satellite respectively, specifying time t0 as the calibration execution time, so that the first auxiliary satellite can transmit the first calibration signal to the satellite to be calibrated at time t0.

5. The low-orbit satellite digital phased array on-orbit calibration system according to claim 4, characterized in that, When the first auxiliary satellite transmits a first calibration signal to the satellite to be calibrated based on the beam pointing angle, it is used to: Before time t0, the first auxiliary satellite calculates the beam pointing angle (θ, φ) pointing towards the satellite to be calibrated based on the first calibration request and real-time orbit parameters. At time t0, the digital beamforming network of the first auxiliary satellite loads the required phase weights for the beam pointing angle (θ, φ), and modulates the pre-stored calibration signal onto radio frequency via the main control unit of the first auxiliary satellite as the first calibration signal, and then transmits the first calibration signal directionally towards the satellite to be calibrated via the phased array antenna.

6. The low-orbit satellite digital phased array on-orbit calibration system according to claim 2, characterized in that, Assume the channel measurement delay is t. k The amplitude-phase response includes the measured amplitude a k and measuring phase φ k The first ideal DBF phase difference is transferred from the measured phase φ. k After removal, the obtained first channel-level error includes the first phase error Δφ. k Then, when the calibration compensation module of the satellite to be calibrated updates the receiving compensation parameters based on the first channel-level error, it is used to: Based on channel measurement delay t k Measurement amplitude a k and the first phase error Δφ k The compensation parameter set for the receiving channel is determined to be (1 / a). k , Δφ k , t k ), and utilize (1 / a k , Δφ k , t k Update the receive compensation parameters to prepare for subsequent digital signals entering the receive channel. k (t) are all according to the formula s' k (t) = (1 / a k ) s k (t + t k ) exp(j Real-time compensation is performed using Δφk) to correct the errors of each receiving channel of the satellite to be calibrated, where k represents the sequence number of the receiving channel.

7. The low-Earth orbit satellite digital phased array on-orbit calibration system according to any one of claims 1-6, characterized in that: The main control unit of the satellite to be calibrated is used to monitor the launch performance of the satellite to be calibrated, and when the launch performance is detected to be degraded, it sends a second calibration request to the ground control unit. The ground control unit is used to receive the second calibration request, and select and schedule a second auxiliary satellite that meets the conditions according to the ephemeris and the second calibration request; The phased array antenna of the satellite to be calibrated is used to transmit a second calibration signal to the second auxiliary satellite through each channel after the second auxiliary satellite is in place; The second auxiliary satellite is used to receive the second calibration signal, and based on the second calibration signal, obtain the amplitude and phase delay information of each channel through cross-correlation and solution, and, based on the amplitude and phase delay information, calculate the second ideal DBF phase difference and extract the second channel-level error, and, through the inter-satellite communication module, transmit the second channel-level error back to the main control unit of the satellite to be calibrated; The calibration compensation module of the satellite to be calibrated is used to update the launch compensation parameters based on the second channel-level error and complete the launch channel calibration.

8. The low-orbit satellite digital phased array on-orbit calibration system according to claim 7, characterized in that, The second auxiliary satellite, when used for extracting the second channel-level error, is specifically used for: The phased array antenna of the second auxiliary satellite receives the second calibration signal via an air interface; The radio frequency front-end of the second auxiliary satellite performs low-noise amplification, down-conversion, and filtering operations on the second calibration signal in sequence to obtain the second analog signal; The digital-to-analog / analog-to-digital converter of the second auxiliary satellite performs analog-to-digital conversion on the second analog signal to obtain a digital signal; The digital beamforming network of the second auxiliary satellite obtains the amplitude and phase delay information of each channel through cross-correlation and decomposition based on the direction of arrival and the digital signal, and calculates the second ideal DBF phase difference based on the amplitude and phase delay information; The calibration compensation module of the second auxiliary satellite performs channel-level compensation for amplitude, phase and delay on the second calibration signal based on the second ideal DBF phase difference to obtain the second compensation signal; The main control unit of the second auxiliary satellite analyzes and processes the second compensation signal to obtain the second channel-level error.

9. The low-orbit satellite digital phased array on-orbit calibration system according to claim 1, characterized in that, The given calibration signal is a ZC sequence or a cyclic shift variant of a ZC sequence or a broadband signal with autocorrelation properties.

10. A method for applying the on-orbit calibration system for low-Earth orbit satellite digital phased arrays as described in any one of claims 1-9, characterized in that, include: Using the main control unit of the satellite to be calibrated, monitor whether the phased array channel parameters of the satellite to be calibrated have shifted. If so, send a calibration request to the ground control unit. The ground control unit selects and schedules target satellites that meet the conditions as auxiliary satellites according to the ephemeris and the calibration request, and controls the link between the auxiliary satellites and the satellite to be calibrated to transmit or receive a given calibration signal. The auxiliary satellites are used as calibration reference sources. Based on the given calibration signal, the digital beamforming network of the satellite to be calibrated or the auxiliary satellite is used to perform cross-correlation and least squares algorithm operations to obtain the measurement amplitude, measurement phase and measurement delay of each transceiver channel of the satellite to be calibrated; Based on the given calibration signal and the phased array element parameters of the satellite to be calibrated, the theoretical inter-channel phase difference introduced by the beamforming network of the satellite to be calibrated or the auxiliary satellite is removed from the measured phase to obtain the actual channel-level phase difference of each transmit and receive channel of the satellite to be calibrated. Based on the actual channel-level phase difference, the measurement amplitude, and the measurement delay, the calibration compensation module of the satellite to be calibrated is used to perform error compensation on each transmit and receive channel of the satellite to be calibrated, thereby achieving on-orbit calibration of the satellite to be calibrated.

Images