Dual polarized multi-sub-band satellite-earth communication system and method

Abstract

The application relates to the technical field of satellite communication, in particular to a dual-polarization multi-subband satellite-ground communication system and method, which comprises a data branching module, a plurality of independent subband modulation modules, a combined transmission module, a dual-polarization receiving antenna, a signal two-dimensional separation module and a multi-channel parallel demodulation module; the data branching module first splits wideband baseband data to be transmitted into a plurality of subband data, then the subband modulation modules perform high-order modulation processing on the plurality of subband data respectively to obtain a plurality of subband signals, then the combined transmission module combines the plurality of subband signals in an analog domain and performs frequency conversion and transmission; the dual-polarization receiving antenna and the signal two-dimensional separation module receive downlink radio frequency signals with orthogonal polarization characteristics, and separate a plurality of physical channel signals according to frequency division multiplexing and polarization orthogonal rules; finally, the multi-channel parallel demodulation module independently and asynchronously parallel demodulates the plurality of physical channel signals, and combines and restores the wideband baseband data.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology. More specifically, this invention relates to a dual-polarized multi-sub-band satellite-to-ground communication system and method. Background Technology

[0002] X-band high-speed microwave data transmission technology refers to a communication technology that utilizes the 8-12GHz X-band microwave resources and employs methods such as high-order modulation and demodulation, phase noise compensation, and intelligent channel equalization to achieve high code rate data transmission of up to 2100Mbps for a single channel and 6Gbps for dual channels between satellites and ground receiving stations. This technology can increase the code rate of traditional satellite-to-ground microwave communication by 75%, effectively breaking through the bandwidth bottleneck of current remote sensing satellite massive observation data downlink. It can support the real-time transmission of large-capacity data such as 8K remote sensing images and high-definition images of disaster sites, which is of great significance for improving my country's disaster relief, high-definition navigation, and precise land planning.

[0003] To achieve the above technologies, two main approaches are currently being used: One approach is a single-channel, high-bandwidth scheme. Its principle involves maximizing the reuse of existing ground equipment, employing 128QAM high-order orthogonal amplitude modulation to increase the bit capacity per symbol, and incorporating a deep neural network model into the modem's core algorithm. This allows AI to learn channel characteristics in real-time and adaptively adjust demodulation parameters. Finally, stable high-rate signal transmission is achieved through whole-band transmission within a single channel. However, in actual deployment, this scheme requires the onboard power amplifier to provide extremely high peak power and linearity, placing stringent demands on heat dissipation and power supply. Simultaneously, the ground station must be equipped with a large-aperture antenna (over 12m), which is typically incompatible with conventional telemetry and control stations, resulting in poor equipment compatibility and high deployment costs.

[0004] Another approach is the multi-subband carrier aggregation scheme. Its execution principle relies on the orthogonal isolation characteristics of dual polarization. Within two independent left- and right-hand polarization channels, broadband signal synthesis technology in the digital domain combines baseband signals originally belonging to different subbands. These signals are then radiated and transmitted across the entire bandwidth via a unified up-conversion and power amplification link. This eliminates the need for independent transmission of multiple subbands, achieving integrated scheduling and utilization of the entire frequency band's spectrum resources. However, this scheme lacks guard intervals between subbands, resulting in severe adjacent-channel crosstalk. Furthermore, it relies on complex digital baseband carrier aggregation and phase synchronization algorithms, making on-board implementation difficult, unstable, and fraught with engineering risks.

[0005] In summary, the existing technologies mainly suffer from weak compatibility and weak anti-interference capabilities. Summary of the Invention

[0006] To address the aforementioned technical problems of weak compatibility and weak anti-interference capability, this invention discloses a dual-polarized multi-subband satellite-to-ground communication system and method.

[0007] In a first aspect, the present invention discloses a dual-polarized multi-subband satellite-to-ground communication system, comprising a satellite terminal and a ground station; wherein the satellite terminal includes a data splitting module, multiple independent subband modulation modules, and a combining transmission module; and the ground station includes a dual-polarized receiving antenna, a two-dimensional signal separation module, and a multi-channel parallel demodulation module. The data splitting module is used to split the broadband baseband data to be transmitted into multiple sub-band data; in the spectrum allocation, a guard interval is maintained between adjacent sub-band data. The sub-band modulation module is used to perform high-order modulation processing on multiple sub-band data to obtain multi-channel sub-band signals; The combiner transmitter module is used to combine multiple sub-band signals in the analog domain and transmit them at a different frequency. The dual-polarized receiving antenna and signal two-dimensional separation module are used to receive downlink radio frequency signals with orthogonal polarization characteristics, and separate multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules. The multi-channel parallel demodulation module is used to demodulate multiple physical channel signals independently and asynchronously in parallel, and then merge them to restore broadband baseband data.

[0008] Preferably, the satellite end includes a central processing unit, a downlink transmitter, and an uplink receiver; the ground station includes a CCSDS receiver and an ACM control station; wherein, the data splitting module, multiple independent sub-band modulation modules, and a combining transmission module are configured in the downlink transmitter; the dual-polarized receiving antenna, the two-dimensional signal separation module, and the multi-channel parallel demodulation module are configured in the CCSDS receiver.

[0009] Preferably, the data splitter module includes a horizontally polarized positive traffic channel and a vertically polarized positive traffic channel; the horizontally polarized positive traffic channel includes at least three baseband modulation units; the vertically polarized positive traffic channel includes at least three baseband modulation units.

[0010] Preferably, the multi-channel parallel demodulation module includes multiple sub-channel demodulators configured with Doppler frequency offset correction units.

[0011] Preferably, the ground station further includes a channel state assessment module, and the satellite end further includes a parameter execution module; wherein, the parameter execution module is used to update the satellite execution parameters according to the signal fed back by the channel state assessment module.

[0012] Secondly, the present invention also discloses a dual-polarized multi-subzone satellite-to-ground communication method for the dual-polarized multi-subzone satellite-to-ground communication system described in the first aspect. The method of the present invention includes: S10: Divide the broadband baseband data to be transmitted into multiple sub-band data; wherein, in the spectrum allocation, a guard interval is maintained between adjacent sub-band data; S20: Perform high-order modulation processing on multiple sub-band data respectively to obtain multi-sub-band signals; S30: Combines and transmits multiple sub-band signals in the analog domain at a different frequency. S40: Receives downlink RF signals with orthogonal polarization characteristics and separates multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules; S50: Independently and asynchronously demodulate multiple physical channel signals in parallel and merge them to restore broadband baseband data.

[0013] Preferably, step S10 includes: Broadband baseband data within the total bandwidth is divided into multiple sub-band data; Configure the guard interval to carry a specific sequence for synchronization or calibration.

[0014] Preferably, the method of the present invention further includes: During the demodulation of multiple physical channel signals, the independent channel state parameters of each physical channel are evaluated in real time. Based on the channel state parameters, configure the target modulation scheme and / or coding rate for each physical channel, and generate corresponding control commands. Control commands are sent to the satellite via the uplink to update the relevant parameters for higher-order modulation processing.

[0015] Preferably, step S50 includes: Each separated physical channel signal is connected to an independent sub-channel demodulator; the sub-channel demodulators operate independently and asynchronously. The Doppler search range is configured using the received ephemeris data, and residual frequency offset correction is performed in combination with pilot or data-assisted algorithms.

[0016] Preferably, the protection interval is not less than 3MHz.

[0017] The advantages of this invention, which differ from existing technologies, are as follows: Firstly, the system of the present invention significantly reduces the implementation difficulty of on-board power amplifiers, and the peak power and linearity requirements of its single-channel power amplifier are reduced by more than 60%, which can be adapted to the miniaturized and low-power platform of low-orbit microsatellites and overcome the problem of weak compatibility of existing technologies.

[0018] Secondly, the system of the present invention adopts a simple architecture of first splitting and then combining, and completes demodulation and frequency offset correction based on the CCSDS standard demodulator, which has a low failure rate and strong engineering feasibility.

[0019] Thirdly, the method of the present invention reserves a dedicated protection interval of 3MHz between adjacent sub-bands, making its adjacent channel leakage ratio better than -45dBc, thereby effectively improving the information transmission accuracy and anti-interference capability. Attached Figure Description

[0020] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, and like or corresponding reference numerals denote like or corresponding parts, wherein: Figure 1 This is a schematic diagram of the structure of the dual-polarized multi-sub-band satellite-to-ground communication system in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of spectrum division in Embodiment 1 of the present invention; Figure 3 This is a block diagram of the on-board high-speed downlink principle in Embodiment 1 of the present invention; Figure 4 This is a block diagram of the ground receiving and demodulation link principle in Embodiment 1 of the present invention; Figure 5 This is a flowchart of the dual-polarized multi-subband satellite-to-ground communication method in Embodiment 2 of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present 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 the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] Example 1 like Figure 1 As shown, this embodiment discloses a dual-polarized multi-subband satellite-to-ground communication system, including a satellite terminal and a ground station. The satellite terminal includes a data splitting module, multiple independent subband modulation modules, and a combining transmission module. The ground station includes a dual-polarized receiving antenna, a two-dimensional signal separation module, and a multi-channel parallel demodulation module. Further, the satellite terminal includes a central processing unit (CPU), a downlink transmitter, and an uplink receiver. The ground station includes a CCSDS receiver and an ACM control station. The data splitting module, multiple independent subband modulation modules, and the combining transmission module are configured within the downlink transmitter. The dual-polarized receiving antenna, the two-dimensional signal separation module, and the multi-channel parallel demodulation module are configured within the CCSDS receiver.

[0024] Unlike existing technologies, the above communication architecture is simpler, more reliable, and more compatible.

[0025] In this embodiment, the data splitting module is primarily used to divide the broadband baseband data to be transmitted into multiple sub-band data. Specifically, the data splitting module includes a horizontally polarized orthogonal channel and a vertically polarized orthogonal channel; the horizontally polarized orthogonal channel includes at least three baseband modulation units; and the vertically polarized orthogonal channel includes at least three baseband modulation units. Within a continuous physical spectrum in a commonly used satellite communication frequency band (such as the X-band), for example, within a range with a total bandwidth of 300MHz, the spectrum is first divided into three independent sub-channels according to the frequency band to support the splitting of sub-band data.

[0026] Preferred, such as Figure 2 As shown, each sub-channel has an effective bandwidth of 90MHz. In terms of spectrum allocation, a guard interval is maintained between adjacent sub-band data, and a guard interval of no less than 3MHz is reserved between adjacent sub-channels. Within these guard intervals, no valid data is carried, or only specific sequences used for synchronization / calibration are carried, thus completely resolving the adjacent channel crosstalk problem in multi-sub-band parallel transmission.

[0027] More preferably, the center frequencies of the three sub-channels are 8.425 GHz, 8.520 GHz, and 8.615 GHz, respectively, based on the currently available frequency bands, and the protection interval is configured to be 5 MHz.

[0028] Furthermore, such as Figure 3 As shown, by using an FPGA (Field Programmable Gate Array) in conjunction with the above-mentioned spectrum partitioning rules for baseband modulation, the original 300MHz continuous broadband baseband data is split into three 90MHz narrowband sub-band data.

[0029] The above technical solution can eliminate subband crosstalk and improve the transmission signal-to-noise ratio. Specifically, by reserving a dedicated protection interval of more than 3MHz for adjacent subband data, the adjacent channel leakage ratio is better than -45dBc, thereby improving transmission accuracy and stability.

[0030] In this embodiment, the sub-band modulation module is mainly used to perform high-order modulation processing on multiple sub-band data to obtain multi-channel sub-band signals. Specifically, in conjunction with... Figure 3 As shown, this process belongs to the high-speed uplink and downlink processing stage. After the subband modulation module receives the subband data generated by the satellite CPU and modulates it through the baseband, it performs high-order modulation processing, that is, the three subband data are modulated and DA converted again and divided into right-hand and left-hand polarization channels to form 6 physically parallel independent transmission channels with 3 subbands × 2 polarizations. Each independent transmission channel carries one subband signal.

[0031] Compared to the 300MHz full-band transmission scheme, the above scheme, through narrowband splitting, significantly reduces the peak power and linearity requirements of a single power amplifier. Compared to the 4×75MHz digital synthesis scheme, the above scheme only requires three 90MHz sub-bands with dedicated guard intervals, eliminating the need for complex digital carrier aggregation and phase synchronization, making on-board implementation simpler and more stable. Furthermore, the above scheme can be further improved by adding a digital predistortion (DPD) module before the power amplifier to compensate for nonlinear distortion, thereby further enhancing satellite signal transmission efficiency.

[0032] The combining and transmitting module is used to combine and frequency-convert multiple sub-band signals in the analog domain. The dual-polarized receiving antenna and the two-dimensional signal separation module are used to receive downlink RF signals with orthogonal polarization characteristics and separate multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules.

[0033] In another embodiment, a hybrid multiplexing mode of polarization multiplexing and time-division multiplexing can be used on the basis of frequency division multiplexing to replace pure polarization multiplexing, so as to be suitable for asymmetric data transmission scenarios.

[0034] The multi-channel parallel demodulation module, as part of the ground station's CCSDS receiver, contains multiple sub-channel demodulators equipped with Doppler frequency offset correction units. Combined with... Figure 4 As can be seen, firstly, the multi-channel parallel demodulation module is used to independently and asynchronously demodulate multiple physical channel signals in parallel, and then merge them to restore the broadband baseband data. Secondly, the multi-channel parallel demodulation module is also used to support closed-loop feedback.

[0035] Regarding the first aspect, its working principle is as follows: First, the ground station receives downlink RF signals (multiple physical channel signals) from the satellite to the ground using a single conventional aperture antenna with dual-polarization reception capability. Then, the signals are sent to a broadband RF front-end for preprocessing such as filtering, low-noise amplification, and down-conversion. The preprocessed mixed signals are then separated by frequency and polarization into six independent sub-band signals, each corresponding to a unique (sub-band, polarization) combination. Each signal is then connected to a sub-channel demodulator conforming to the CCSDS standard. Finally, high-precision demodulation, Doppler frequency offset correction, and data restoration are performed within a 90MHz bandwidth.

[0036] During the Doppler frequency offset correction process, the demodulator uses the received ephemeris data to preset the Doppler search range and combines pilot or data-assisted algorithms to achieve accurate correction of the residual frequency offset. During the above process, the six parallel demodulators work independently and asynchronously without exchanging synchronization or phase information, which has stronger system fault tolerance.

[0037] Through the above technical solution, the single-channel information transmission rate of the system of the present invention can reach 300Mbps, and in the 6-channel parallel transmission mode, the theoretical maximum transmission rate of the system can reach 1.8Gbps, with a corresponding spectral efficiency of 6bps / Hz.

[0038] In another embodiment, the centralized 6-channel parallel demodulation architecture can be replaced with a distributed multi-node demodulation architecture, thereby further improving the system's fault tolerance and ensuring that a single point of failure does not affect the overall data transmission function.

[0039] Furthermore, the ground station also includes a channel state assessment module, and the satellite end includes a parameter execution module. The parameter execution module updates the satellite execution parameters based on the signals fed back from the channel state assessment module. The working principle of this second aspect is as follows: First, the ground station receives satellite ephemeris data in real time, calculates the current satellite-to-ground geometric distance and relative velocity, and predicts path loss and Doppler shift. Then, it measures the received signal in real time to obtain the independent carrier-to-noise ratio (C / N0) and bit error rate (BER) for each sub-band and each polarization channel. Next, based on the predefined modulation and coding table (MCS Table), it decides the modulation scheme and coding rate to be used for each channel, as well as whether to shut down certain sub-bands to prevent congestion. Finally, the ground station sends ACM control commands to the satellite through the uplink remote control link. At this time, the satellite performs parameter updates (including modulation scheme, coding, transmit gain, etc.) and feeds back the working status, forming a complete closed loop.

[0040] Through the above technical solution, the system in this embodiment successfully built a satellite-to-ground two-way adaptive modulation and coding (ACM) closed-loop control loop, realizing refined link adaptation.

[0041] Example 2 like Figure 5 As shown, based on Embodiment 1, this embodiment discloses a dual-polarization multi-sub-band satellite-to-ground communication method, including: S10: Divide the broadband baseband data to be transmitted into multiple subband data.

[0042] Specifically, in the spectrum allocation, a guard interval is maintained between adjacent sub-band signals, and the guard interval is not less than 3MHz. More specifically, step S10 above includes: S11: Divide the broadband baseband data within the total bandwidth range into multiple subband data.

[0043] For example, if the total bandwidth is 300MHz, the broadband baseband data is divided into three sub-bands, and the guard interval between each sub-band is configured to be greater than or equal to 3MHz.

[0044] S12: Configure the guard interval to carry a specific sequence for synchronization or calibration.

[0045] The aforementioned specific sequences may contain check codes or check tags. To ensure that the signal is decrypted or intercepted during transmission, these specific sequences can be encrypted using national cryptographic algorithms to improve the security of information transmission.

[0046] S20: Perform high-order modulation processing on multiple sub-band data respectively to obtain multi-channel sub-band signals.

[0047] It should be explained that the above steps mainly involve re-modulating and DA-converting the three sub-band data and separating them into right-hand and left-hand polarization channels, forming 6 physically parallel independent transmission channels with 3 sub-bands × 2 polarizations. Each independent transmission channel carries one sub-band signal.

[0048] S30: Combines multiple subband signals in the analog domain and transmits them at a different frequency.

[0049] In another embodiment, analog intermediate frequency combining can be replaced with digital channelized combining to suit satellite platforms with stronger processing capabilities (such as high-orbit satellites or large low-orbit constellations), while still achieving the effect of combining multiple subbands after independent modulation.

[0050] Steps S10-S30 above mainly describe the processing of signals sent from the satellite to the ground station, while steps S40-S50 describe the parsing process after the ground station receives the signals.

[0051] S40: Receives downlink RF signals with orthogonal polarization characteristics and separates multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules.

[0052] It should be explained that the aforementioned frequency division multiplexing refers to dividing the total available bandwidth of the communication channel into multiple non-overlapping independent sub-frequency bands. Each signal is modulated onto its own subcarrier frequency, enabling multiple signals to be transmitted in parallel within the same physical channel. The polarization orthogonality rule is a core principle in the field of electromagnetic wave polarization and will not be elaborated upon here.

[0053] S50: Independently and asynchronously demodulate multiple physical channel signals in parallel and merge them to restore broadband baseband data.

[0054] Further, step S50 above includes: S51: Connect each separated physical channel signal to an independent sub-channel demodulator.

[0055] Each sub-channel demodulator operates independently and asynchronously.

[0056] S52: Configure the Doppler search range using the received ephemeris data, and perform residual frequency offset correction in conjunction with pilot or data-assisted algorithms.

[0057] The steps S51-S52 described above have been clearly explained in the first aspect of the working principle of the ground station in Embodiment 1, and will not be repeated here.

[0058] Furthermore, the method in this embodiment also includes: S500: During the demodulation of multiple physical channel signals, the independent channel state parameters of each physical channel are evaluated in real time.

[0059] In this embodiment, the aforementioned channel state parameters include basic fading parameters, signal quality parameters, transmission efficiency parameters, multipath and delay parameters, and statistical characteristic parameters. Among these numerous channel state parameters, the carrier-to-noise ratio (CNR) from the signal quality parameters and the bit error rate (BER) from the transmission efficiency parameters are preferred as quantitative evaluation indicators. The CNR is the ratio of the carrier signal power to the white noise power spectral density at the receiver's intermediate frequency output. It is a core indicator used to evaluate the relative relationship between channel signal and noise, and to measure the quality of the received signal, directly affecting the demodulation performance of the system. The BER, on the other hand, is the proportion of erroneous bits to the total number of transmitted bits. It is a key indicator used to measure the reliability of channel transmission in a digital communication system, reflecting the final transmission error level of the channel.

[0060] S501: Based on the channel state parameters, configure the target modulation scheme and / or coding rate for each physical channel, and generate the corresponding control commands.

[0061] Specifically, the ground station can adjust the modulation method or coding rate of each channel and whether to close certain subbands to resist congestion by looking up a predefined modulation coding table.

[0062] S502: Sends control commands to the satellite via the uplink to update relevant parameters for higher-order modulation processing.

[0063] In this embodiment, the sub-bands are adjusted independently, supporting asymmetric rate configuration. The relevant parameters mainly include modulation scheme, coding format, and transmit gain.

[0064] Based on the above technical description, the present invention has at least the following technical advantages: Firstly, the method in this embodiment splits the 300MHz broadband into three 90MHz narrowband independent transmissions, reducing the peak power and linearity requirements of a single power amplifier by more than 60%, making it particularly suitable for miniaturized, low-power platforms for low-orbit microsatellites.

[0065] Secondly, the method in this embodiment abandons the complex digital baseband synthesis and phase synchronization algorithm of the traditional 4×75MHz scheme, adopts a simple architecture of first splitting and then combining, and completes demodulation and frequency offset correction based on the CCSDS standard demodulator, which has a low failure rate and strong engineering feasibility.

[0066] Third, the method in this embodiment reserves a dedicated protection interval of more than 3MHz between adjacent subbands, and the adjacent channel leakage ratio is better than -45dBc, which effectively eliminates the subband crosstalk problem and improves the transmission signal-to-noise ratio.

[0067] Fourth, the system in this embodiment does not require a large-aperture receiving antenna of more than 12m. It can complete signal reception and demodulation by relying on existing conventional dual-polarized ground telemetry and control antennas, which has low implementation cost and wide applicability.

[0068] Fifth, although the system in this embodiment sacrifices about 3.3% of spectrum resources due to the guard interval, it can achieve a total rate of 1.8Gbps (spectral efficiency of 6bps / Hz) within a fixed bandwidth of 300MHz by constructing a 6-channel parallel mechanism through frequency division and combination polarization dual reuse, which is 6 times higher than the traditional single-channel system.

[0069] Sixth, the system in this embodiment relies on the closed-loop adaptive control of the satellite-to-ground ACM, which can dynamically counteract cloud obstruction, channel fading and Doppler changes caused by high-speed satellite movement, and take into account both high-speed transmission and environmental adaptability.

[0070] Seventh, the system in this embodiment is backward compatible with traditional ground stations that only support single channel or single polarization. Channels that do not require maintenance can simply be shut down, thus protecting the user's existing investment.

[0071] In the description of this specification, "multiple" means at least two, such as two, three or more, etc., unless otherwise expressly and specifically defined.

[0072] While this specification has shown and described numerous embodiments of the invention, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of this invention.

Claims

1. A dual-polarized multi-sub-band satellite-to-ground communication system, characterized in that, It includes a satellite terminal and a ground station; wherein, the satellite terminal includes a data splitting module, multiple independent sub-band modulation modules, and a combined transmission module; the ground station includes a dual-polarized receiving antenna, a two-dimensional signal separation module, and a multi-channel parallel demodulation module; The data splitting module is used to split the broadband baseband data to be transmitted into multiple sub-band data; wherein, in the spectrum allocation, a guard interval is maintained between adjacent sub-band data. The sub-band modulation module is used to perform high-order modulation processing on multiple sub-band data respectively to obtain multi-channel sub-band signals; The combining and transmitting module is used to combine the multi-subband signals in the analog domain and transmit them at a frequency conversion. The dual-polarized receiving antenna and signal two-dimensional separation module are used to receive downlink radio frequency signals with orthogonal polarization characteristics, and separate multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules. The multi-channel parallel demodulation module is used to independently and asynchronously demodulate multiple physical channel signals in parallel and merge them to restore broadband baseband data.

2. The dual-polarization multi-sub-band satellite-to-ground communication system according to claim 1, characterized in that, The satellite terminal includes a central processing unit, a downlink transmitter, and an uplink receiver; the ground station includes a CCSDS receiver and an ACM control station; wherein, the data splitting module, multiple independent sub-band modulation modules, and a combining transmission module are configured in the downlink transmitter; the dual-polarized receiving antenna, the two-dimensional signal separation module, and the multi-channel parallel demodulation module are configured in the CCSDS receiver.

3. The dual-polarization multi-sub-band satellite-to-ground communication system according to claim 1, characterized in that, The data splitter module includes a horizontally polarized positive channel and a vertically polarized positive channel; the horizontally polarized positive channel includes at least three baseband modulation units; the vertically polarized positive channel includes at least three baseband modulation units.

4. The dual-polarization multi-sub-band satellite-to-ground communication system according to claim 1, characterized in that, The multi-channel parallel demodulation module contains multiple sub-channel demodulators equipped with Doppler frequency offset correction units.

5. The dual-polarized multi-sub-band satellite-to-ground communication system according to any one of claims 1-4, characterized in that, The ground station also includes a channel state assessment module, and the satellite terminal also includes a parameter execution module; wherein, the parameter execution module is used to update the satellite execution parameters according to the signal fed back by the channel state assessment module.

6. A dual-polarized multi-sub-band satellite-to-ground communication method, characterized in that, The method for the dual-polarized multi-subband satellite-to-ground communication system according to any one of claims 1-5 comprises: S10: Divide the broadband baseband data to be transmitted into multiple sub-band data; wherein, in the spectrum allocation, a guard interval is maintained between adjacent sub-band data; S20: Perform high-order modulation processing on multiple sub-band data respectively to obtain multi-sub-band signals; S30: Combine the multi-channel sub-band signals in the analog domain and transmit them at a different frequency; S40: Receives downlink RF signals with orthogonal polarization characteristics and separates multiple physical channel signals from the frequency point and polarization direction according to the frequency division multiplexing and polarization orthogonality rules; S50: Independently and asynchronously demodulate multiple physical channel signals in parallel and merge them to restore broadband baseband data.

7. The dual-polarization multi-sub-band satellite-to-ground communication method according to claim 6, characterized in that, Step S10 includes: Broadband baseband data within the total bandwidth is divided into multiple sub-band data; Configure the guard interval to carry a specific sequence for synchronization or calibration.

8. The dual-polarization multi-sub-band satellite-to-ground communication method according to claim 6, characterized in that, Also includes: During the demodulation of multiple physical channel signals, the independent channel state parameters of each physical channel are evaluated in real time. Based on the channel state parameters, configure the target modulation scheme and / or coding rate for each physical channel, and generate corresponding control commands. The control commands are sent to the satellite via the uplink to update the relevant parameters of the higher-order modulation processing.

9. The dual-polarization multi-sub-band satellite-to-ground communication method according to claim 6, characterized in that, Step S50 includes: Each separated physical channel signal is connected to an independent sub-channel demodulator; the sub-channel demodulators operate independently and asynchronously. The Doppler search range is configured using the received ephemeris data, and residual frequency offset correction is performed in combination with pilot or data-assisted algorithms.

10. The dual-polarization multi-sub-band satellite-to-ground communication method according to claim 6, characterized in that, The protection interval is not less than 3MHz.

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