Remote control and remote adjustment system and method based on super-narrow band linear spread spectrum of stationary meteorological satellite

Abstract

This invention discloses a remote control and telemetry system and method based on ultra-narrowband linear spread spectrum (CSS) of a geostationary meteorological satellite, relating to the fields of satellite communication and the Internet of Things (IoT). The system includes: encapsulating, forward error correction coding, and repetition coding of remote control or telemetry command data to obtain a bitstream to be modulated; performing linear frequency modulation spread spectrum modulation on the bitstream to generate an ultra-narrowband CSS baseband signal, up-converting it, and transmitting it to the geostationary meteorological satellite; amplifying the uplink radio frequency signal with low noise and performing frequency conversion before broadcasting it to the ground coverage area; a ground receiving terminal using positive and negative frequency sweep reference signals to perform correlation despreading and soft decision demodulation on the down-converted signal to obtain a soft decision bitstream; and performing repetition code merging, forward error correction decoding, and address authentication on the soft decision bitstream to recover the remote control or telemetry command data. This invention can improve the anti-interference capability and long-distance transmission reliability of remote control and telemetry signals in weak signal environments, reduce the complexity of onboard equipment, and improve spectrum utilization efficiency.

Description

Technical Field

[0001] This invention relates to the fields of satellite communication and Internet of Things (IoT) technology, specifically to a remote control and adjustment system and method based on geostationary meteorological satellite ultra-narrowband linear spread spectrum. Background Technology

[0002] Currently, traditional remote control and telemetry transmission methods typically employ conventional narrowband modulation or fixed-frequency transmission. In long-distance communication with geostationary meteorological satellites, these methods are susceptible to noise interference, co-channel interference, and multipath fading, resulting in a high bit error rate in weak signal environments. Remote control or telemetry commands are prone to loss, misjudgment, or transmission failure. Furthermore, traditional methods consume a large amount of spectrum and have low spectrum utilization efficiency, which can easily lead to channel congestion in scenarios where multiple terminals access the system simultaneously. Additionally, some traditional systems require onboard equipment to perform demodulation, buffering, and forwarding processing, increasing the high path loss of the satellite-end forwarding link and reducing the overall system's operational stability and deployment flexibility.

[0003] Furthermore, traditional remote control and telemetry receiving methods typically employ hard-decision detection and a single correlation demodulation mechanism. In low signal-to-noise ratio environments, these methods struggle to achieve high-precision symbol synchronization and reliable despreading. They are also prone to error accumulation due to insignificant correlation peaks, resulting in low command recovery accuracy. Moreover, traditional methods lack soft-decision confidence-assisted error correction mechanisms, making them less adaptable to sudden interference and weak signal scenarios. Additionally, some traditional systems lack robust address authentication and data verification mechanisms, making them susceptible to erroneous control, illegal command injection, and broadcast conflicts. Consequently, they fail to meet the high-reliability remote control and telemetry requirements in large-scale, multi-device, and unattended scenarios, thus limiting their application in remote equipment control, meteorological monitoring, and wide-area broadcast control scenarios. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide, on the one hand, a remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum, comprising:

[0005] The instruction encoding and encapsulation module responds to the remote control or teleading instruction data generated by the ground control center, encapsulates the instruction data into a data frame containing the target address and check code, and performs forward error correction encoding and repetition encoding to obtain the bit stream to be modulated.

[0006] The spread spectrum modulation transmission module is responsive to mapping the bit stream to be modulated into symbols, and modulating each symbol using a linear frequency modulation spread spectrum method to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is then upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite.

[0007] The radio frequency signal broadcasting module responds to the onboard transparent transponder receiving the uplink radio frequency signal and performing low-noise amplification. After low-noise amplification, it is downconverted to intermediate frequency and then upconverted to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal. After high-power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode, or store the signal throughout the entire process.

[0008] The soft decision bitstream generation module, in response to the ground receiving terminal receiving the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and uses positive and negative sweep frequency reference signals matched with the transmitting end to process the down-converted signal, despread the down-converted signal into a narrowband pulse signal and demodulate the soft decision bitstream;

[0009] The instruction recovery module, in response to performing duplicate code merging and forward error correction decoding on the soft decision bitstream, and performing verification and address authentication on the decoded data frame, recovers the remote control or teleadjustment instruction data; converts the recovered instruction data into control signals recognizable by the controlled device and outputs them to the connected controlled device to perform corresponding operations.

[0010] Preferably, the instruction data is encapsulated into a data frame containing a target address and a checksum, and forward error correction coding and repetition coding are performed to obtain the bit stream to be modulated, including:

[0011] The ground control center generates remote control or teleading command data, adds a target address field to the command data, and the target address field supports unicast address, multicast address or broadcast address to obtain command data containing the target address;

[0012] A frame header field is added to the instruction data containing the target address. The frame header field is used for frame synchronization and frame type identification to obtain instruction data containing a frame header.

[0013] The checksum is calculated and appended to the instruction data containing the frame header to obtain a data frame containing the target address and the checksum;

[0014] The complete data frame is channel-coded using a forward error correction coding method. A check bit is appended to the information bits of the data frame to obtain a forward error correction codeword. The forward error correction coding method includes Hamming code, BCH code, or convolutional code.

[0015] The forward error correction codewords are repeatedly encoded to obtain several forward error correction codewords. Several identical forward error correction codewords are then concatenated in sequence to obtain the bit stream to be modulated.

[0016] Preferably, the bitstream to be modulated is mapped to symbols, and each symbol is modulated using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal, including:

[0017] The bit stream to be modulated is mapped to modulation symbols to obtain a symbol sequence;

[0018] For each symbol in the symbol sequence, the linear frequency modulation sweep direction is determined according to its corresponding bit value, and the sweep direction includes positive sweep and negative sweep;

[0019] Based on the sweep direction, determine the linear frequency modulation pulse corresponding to each symbol;

[0020] The linear frequency modulated pulses corresponding to each symbol are sequentially connected on the time axis to obtain a continuous linear frequency modulated pulse sequence, which is then used as the ultra-narrowband CSS baseband signal.

[0021] Preferably, for each symbol in the symbol sequence, determining the linear frequency modulation sweep direction based on its corresponding bit value includes:

[0022] Obtain the bit value corresponding to the currently unprocessed symbol in the symbol sequence;

[0023] Determine whether the bit value is a preset first bit value. If the bit value is a preset first bit value, then determine that the linear frequency modulation sweep direction of the current symbol is a positive sweep direction. The positive sweep direction means that the frequency increases linearly from low to high during the symbol duration.

[0024] If the bit value is a preset second bit value, then the linear frequency modulation sweep direction of the current symbol is determined to be a negative sweep direction, which means that the frequency decreases linearly from high to low during the symbol duration.

[0025] Preferably, the ultra-narrowband CSS baseband signal is upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, including:

[0026] The ultra-narrowband CSS baseband signal is input to a digital-to-analog converter and converted into a continuous analog baseband signal. It is then band-limited filtered by a pulse shaping filter to eliminate out-of-band spectral components, resulting in a processed analog baseband signal.

[0027] Based on the frequency planning of the uplink frequency band of geostationary meteorological satellites, the corresponding uplink local oscillator frequency is selected, and the processed analog baseband signal is orthogonally upconverted and mixed with the uplink local oscillator frequency to obtain the uplink intermediate frequency signal.

[0028] The uplink intermediate frequency signal is subjected to intermediate frequency bandpass filtering to remove the image frequency components and spurious signals generated during the mixing process, and the filtered uplink intermediate frequency signal is obtained.

[0029] Based on the target frequency of the uplink radio frequency band of the geostationary meteorological satellite, the radio frequency local oscillator signal is selected, and the filtered uplink intermediate frequency signal is mixed with the radio frequency local oscillator signal by a second upconversion to obtain the uplink radio frequency signal.

[0030] Preferably, the processed analog baseband signal is orthogonally up-converted and mixed with the uplink local oscillator frequency to obtain the uplink intermediate frequency signal, including:

[0031] The processed analog baseband signal is separated into in-phase and quadrature components to obtain I-path baseband signal and Q-path baseband signal;

[0032] The local oscillator generates the local oscillator signal corresponding to the uplink local oscillator frequency, and the local oscillator signal is divided into two local oscillator signals with orthogonal phases by a 90-degree phase shifter, resulting in an in-phase local oscillator signal and a quadrature local oscillator signal, respectively.

[0033] The baseband signal of the I-path and the in-phase local oscillator signal are fed into the first mixer for mixing to obtain the in-phase intermediate frequency component;

[0034] The Q-band baseband signal and the quadrature local oscillator signal are fed into the second mixer for mixing to obtain quadrature intermediate frequency components.

[0035] The in-phase intermediate frequency component and the quadrature intermediate frequency component are superimposed and combined by a combiner to obtain the uplink intermediate frequency signal.

[0036] Preferably, the onboard transparent transponder receives the uplink radio frequency signal and performs low-noise amplification, then downconverts it to an intermediate frequency (IF), and then upconverts it to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal, including:

[0037] The uplink radio frequency signal is acquired and then amplified by a satellite low-noise amplifier to obtain a low-noise amplified uplink radio frequency signal.

[0038] Based on the frequency relationship between the satellite uplink frequency band and intermediate frequency, the corresponding downlink local oscillator signal is selected, and the uplink radio frequency signal after low noise amplification and the downlink local oscillator signal are downconverted and mixed to obtain the downlink intermediate frequency signal.

[0039] Based on the target frequency of the downlink broadcast band of the geostationary meteorological satellite, the corresponding uplink local oscillator signal is selected, and the downlink intermediate frequency signal and the uplink local oscillator signal are upconverted and mixed to obtain the satellite downlink broadcast radio frequency signal.

[0040] Preferably, the down-converted signal is processed using positive and negative frequency sweep reference signals matched with the transmitter, despreading the down-converted signal into a narrowband pulse signal and demodulating it to obtain a soft-decision bitstream, including:

[0041] The down-conversion signal is input to the positive and negative sweep frequency correlators, and sliding correlation operations are performed with the positive and negative sweep frequency reference signals, respectively, to obtain the correlation operation results.

[0042] Continuous peak detection is performed on the relevant calculation results, and the moment when the relevant peak appears within each symbol duration window is determined as the precise symbol synchronization point;

[0043] By comparing the peak output amplitudes of the positive and negative frequency sweep correlators at the symbol synchronization point, the bit determination results are obtained, including:

[0044] If the peak amplitude of the positive frequency sweep correlator is greater than that of the negative frequency sweep correlator, then the current symbol is determined to correspond to the preset first bit value;

[0045] If the peak amplitude of the negative frequency sweep correlator is greater than that of the positive frequency sweep correlator, then the current symbol is determined to correspond to the preset second bit value;

[0046] The amplitude difference between the peak values ​​of the two correlator outputs at each symbol synchronization point is extracted as soft-decision confidence information. The bit determination result is combined with the corresponding soft-decision confidence information to form a soft-decision bit stream.

[0047] Preferably, the down-conversion signal is input to the positive sweep frequency correlator and the negative sweep frequency correlator, and sliding correlation operations are performed with the positive sweep frequency reference signal and the negative sweep frequency reference signal, respectively, to obtain the correlation operation results, including:

[0048] The down-converted signal is multiplied point by point with the positive sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the positive sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband positive pulse signal and obtaining the first correlation operation result of the positive sweep correlator containing the narrowband positive pulse signal.

[0049] The down-converted signal is multiplied point by point with the negative sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the negative sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband negative pulse signal, and obtaining the second correlation operation result of the negative sweep correlator outputting the narrowband negative pulse signal.

[0050] Another aspect of the present invention discloses a remote control and telemetry method based on ultra-narrowband linear spread spectrum of geostationary meteorological satellites, comprising:

[0051] S1. The ground control center generates remote control or teleading command data, encapsulates the command data into a data frame containing the target address and check code, and performs forward error correction coding and repetition coding to obtain the bit stream to be modulated.

[0052] S2. The bit stream to be modulated is mapped into symbols, and each symbol is modulated using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite.

[0053] S3. The onboard transparent transponder receives the uplink radio frequency signal and performs low-noise amplification. After low-noise amplification, it is downconverted to intermediate frequency and then upconverted to satellite downlink broadcast frequency band to obtain satellite downlink broadcast radio frequency signal. After high-power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode or store the signal throughout the entire process.

[0054] S4. The ground receiving terminal receives the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and processes the down-converted signal using positive and negative sweep frequency reference signals matched with the transmitting end, despreads the down-converted signal into a narrowband pulse signal and demodulates the soft decision bit stream.

[0055] S5. Perform duplicate code merging and forward error correction decoding on the soft decision bitstream, and perform verification and address authentication on the decoded data frame to recover the remote control or teleadjustment command data; convert the recovered command data into control signals that can be recognized by the controlled device and output them to the connected controlled device to perform the corresponding operation.

[0056] Compared with the prior art, the beneficial effects of the present invention are:

[0057] 1. This invention significantly improves the noise resistance and weak signal transmission reliability of remote control or telemetry signals during long-distance transmission by performing forward error correction coding, repetition coding, and ultra-narrowband linear spread spectrum modulation on remote control or telemetry commands. By using positive and negative frequency sweep linear frequency modulation spread spectrum, stable signal transmission under ultra-narrowband conditions is achieved, which can effectively reduce spectrum occupation and improve spectrum resource utilization efficiency. Furthermore, combined with the onboard transparent forwarding mechanism, there is no need for complex demodulation and storage processing at the satellite end, which reduces the complexity and power consumption of onboard equipment and improves the overall system operation stability and engineering deployment flexibility.

[0058] 2. This invention utilizes dual correlator sliding correlation despreading technology and a soft-decision decoding mechanism in the ground receiving terminal to achieve accurate synchronization and reliable recovery of spread spectrum signals under extremely low signal-to-noise ratio conditions. By generating a soft-decision bitstream using correlation peak detection and soft-decision confidence information, it can improve error correction capability and command recovery accuracy. At the same time, combined with address authentication and data frame verification mechanisms, it can effectively avoid miscontrol and illegal command interference, improving the security and reliability of the remote control and adjustment system. Moreover, through broadcast satellite coverage, it can simultaneously realize wide-area remote control and adjustment of multiple remotely controlled devices, enhancing the system's applicability in meteorological monitoring, unattended equipment control, and communication scenarios in remote areas. Attached Figure Description

[0059] Figure 1 This is a schematic diagram showing the connection of various modules in the remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to an embodiment of this application.

[0060] Figure 2 This is a schematic flowchart illustrating the steps of a remote control and telemetry method based on ultra-narrowband linear spread spectrum using geostationary meteorological satellites, according to an embodiment of this application. Detailed Implementation

[0061] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0062] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of the present invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in one or more embodiments of the present invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0063] Example 1

[0064] Please see Figure 1 As shown, this application provides a remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum, including:

[0065] The instruction encoding and encapsulation module responds to the remote control or teleading instruction data generated by the ground control center, encapsulates the instruction data into a data frame containing the target address and check code, and performs forward error correction encoding and repetition encoding to obtain the bit stream to be modulated.

[0066] The spread spectrum modulation transmission module is responsive to mapping the bit stream to be modulated into symbols, and modulating each symbol using a linear frequency modulation spread spectrum method to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is then upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite.

[0067] The radio frequency signal broadcasting module responds to the onboard transparent transponder receiving the uplink radio frequency signal and performing low-noise amplification. After low-noise amplification, it is downconverted to intermediate frequency and then upconverted to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal. After high-power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode, or store the signal throughout the entire process.

[0068] The soft decision bitstream generation module, in response to the ground receiving terminal receiving the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and uses positive and negative sweep frequency reference signals matched with the transmitting end to process the down-converted signal, despread the down-converted signal into a narrowband pulse signal and demodulate the soft decision bitstream;

[0069] The instruction recovery module, in response to performing duplicate code merging and forward error correction decoding on the soft decision bitstream, and performing verification and address authentication on the decoded data frame, recovers the remote control or teleadjustment instruction data; converts the recovered instruction data into control signals recognizable by the controlled device and outputs them to the connected controlled device to perform corresponding operations.

[0070] It should be noted that when the ground control center needs to issue remote control commands or modify remote adjustment parameters to remotely controlled equipment (such as remote weather stations, unattended monitoring stations, etc.), the system encapsulates the command data generated by the control center into a standardized data frame containing the target address and check code, and performs forward error correction coding and repetition coding to form a bit stream to be modulated. This process is equivalent to putting a "protective coat" on the command data. Even if some bit errors occur during transmission, they can be repaired through error correction coding, and repetition coding further improves the anti-interference capability of the signal in a weak signal-to-noise ratio environment.

[0071] After mapping the bit stream to be modulated into symbols, each symbol is modulated using linear frequency modulation to generate an ultra-narrowband CSS baseband signal. Since the energy of the CSS signal is extended to an extremely narrow bandwidth, its power spectral density is extremely low, similar to being "hidden" in noise. Subsequently, the baseband signal is upconverted to the satellite uplink frequency band, amplified, and then transmitted to a geostationary meteorological satellite to achieve reliable uplink transmission over long distances with low probability of interception.

[0072] After receiving the uplink radio frequency signal, the onboard transparent transponder only performs low-noise amplification, down-conversion to intermediate frequency, and up-conversion to the satellite downlink broadcast frequency band. It does not demodulate, decode, or store the signal throughout the entire process. This means that the satellite only acts as a "mirror", forwarding the signal as is and broadcasting it to the ground coverage area. This transparent forwarding method avoids the latency and complexity caused by onboard processing, and the broadcast signal after high-power amplification can be received simultaneously by all authorized ground terminals in the coverage area.

[0073] After receiving the satellite downlink broadcast radio frequency signal, the ground receiving terminal first performs low-noise amplification and down-conversion processing to obtain the down-converted signal. Then, it uses positive and negative sweep frequency reference signals matched with the transmitter to perform correlation processing on the down-converted signal, despreading the broadband CSS signal into a narrowband pulse signal. This process is similar to using a "matching key" to extract the original signal from the noise. Finally, the soft-decision bitstream is demodulated. Soft decision retains the confidence information of each bit, which can significantly improve the accuracy of subsequent decoding compared to hard decision.

[0074] The soft-decision bitstream is subjected to duplicate code merging and forward error correction decoding. Redundant information is used to repair the bit errors introduced during transmission. The decoded data frames are then checked and address authenticated to ensure that only commands with matching target addresses and passing verification are accepted. Finally, the recovered command data is converted into control signals that can be recognized by the controlled device and output, such as adjusting satellite payload operating parameters or switching remote sensing observation modes, thereby realizing precise remote control and adjustment of remote devices.

[0075] In a preferred embodiment, the instruction data is encapsulated into a data frame containing a target address and a checksum, and forward error correction coding and repetition coding are performed to obtain the bit stream to be modulated, including:

[0076] The ground control center generates remote control or teleading command data, adds a target address field to the command data, and the target address field supports unicast address, multicast address or broadcast address to obtain command data containing the target address;

[0077] A frame header field is added to the instruction data containing the target address. The frame header field is used for frame synchronization and frame type identification to obtain instruction data containing a frame header.

[0078] The checksum is calculated and appended to the instruction data containing the frame header to obtain a data frame containing the target address and the checksum;

[0079] The complete data frame is channel-coded using a forward error correction coding method. A check bit is appended to the information bits of the data frame to obtain a forward error correction codeword. The forward error correction coding method includes Hamming code, BCH code, or convolutional code.

[0080] The forward error correction codewords are repeatedly encoded to obtain several forward error correction codewords. Several identical forward error correction codewords are then concatenated in sequence to obtain the bit stream to be modulated.

[0081] It should be noted that after the ground control center generates remote control or telemetry command data, it first adds a target address field to the command data. This field supports three modes: unicast address, multicast address, or broadcast address. Unicast is used to precisely control a single device, multicast is used to control a group of similar devices simultaneously, and broadcast is used to send unified commands to all terminals in the coverage area. This flexible address mechanism enables the system to achieve both precise point-to-point control and support large-scale batch scheduling.

[0082] A frame header field is added to the instruction data containing the target address. This frame header is used by the receiver for frame synchronization and frame type identification. Frame synchronization ensures that the receiver can accurately lock the starting position of each frame of data and avoid data misalignment caused by timing offset. The frame type identification enables the receiver to quickly distinguish whether the current received command is a remote control command or a remote adjustment command, thereby triggering the corresponding processing flow.

[0083] The checksum is calculated for the instruction data including the frame header and appended to the data tail to form a complete data frame containing the target address and the checksum. The checksum is like adding a "fingerprint" to the entire data frame. The receiving end can compare the checksum to determine whether bit flips or loss have occurred during the transmission of the data, thus preventing erroneous instructions from being executed.

[0084] Forward error correction coding is used for channel coding of complete data frames, and parity bits are added after the information bits to form forward error correction codewords. The specific coding method can be Hamming code, BCH code or convolutional code. Hamming code is suitable for short frame scenarios where the error correction capability requirement is not high, BCH code can correct multi-bit errors, and convolutional code performs better in continuous transmission. The core value of forward error correction is that the receiver can repair a certain number of transmission errors without requesting retransmission, which is particularly critical for scenarios with high latency and low backhaul efficiency such as satellite links.

[0085] The forward error correction codewords are repeatedly encoded to generate several identical forward error correction codewords, which are then sequentially concatenated to form the bit stream to be modulated. Although the repeated encoding reduces the effective transmission rate, it can significantly improve the demodulation success rate by receiving the same information multiple times in an environment with extremely low signal-to-noise ratio. This design, together with the subsequent ultra-narrowband CSS spread spectrum modulation, constitutes a dual guarantee that the system can reliably transmit commands under adverse channel conditions.

[0086] In a preferred embodiment, the bitstream to be modulated is mapped to symbols, and each symbol is modulated using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal, including:

[0087] The bit stream to be modulated is mapped to modulation symbols to obtain a symbol sequence;

[0088] For each symbol in the symbol sequence, the linear frequency modulation sweep direction is determined according to its corresponding bit value, and the sweep direction includes positive sweep and negative sweep;

[0089] Based on the sweep direction, determine the linear frequency modulation pulse corresponding to each symbol;

[0090] The linear frequency modulated pulses corresponding to each symbol are sequentially connected on the time axis to obtain a continuous linear frequency modulated pulse sequence, which is then used as the ultra-narrowband CSS baseband signal.

[0091] It should be noted that mapping the bit stream to be modulated into modulation symbols forms a symbol sequence. This mapping process converts the original bit information into a symbol form suitable for spread spectrum modulation. Each symbol carries one or more bits of information, providing a modulation basis for subsequent linear frequency modulation spread spectrum.

[0092] For each symbol in the symbol sequence, the direction of the linear frequency modulation (LFM) sweep is determined based on its corresponding bit value. The sweep direction includes positive and negative sweeps. Specifically, if the bit value is "0", it is mapped to a positive sweep, meaning the frequency changes linearly from low to high over time. If the bit value is "1", it is mapped to a negative sweep, meaning the frequency changes linearly from high to low over time. This bidirectional sweep mechanism makes different bit values ​​present mirror-symmetric LFM pulses on the time-frequency plane, and the receiver can effectively distinguish between the two through matched filtering.

[0093] Based on the determined frequency sweep direction, a linear frequency modulated pulse corresponding to each symbol is generated. This pulse completes the frequency sweep within an extremely narrow bandwidth. The time width of a single pulse is much larger than its bandwidth, so the power spectral density is extremely low. The signal energy is "spread" over a wider time and frequency range, thus possessing the characteristics of low interception and anti-interference.

[0094] The linear frequency modulated pulses corresponding to each symbol are sequentially connected on the time axis to form a continuous linear frequency modulated pulse sequence, which serves as the ultra-narrowband CSS baseband signal. The continuous splicing ensures the temporal continuity between symbols, with no guard intervals or zero-return gaps, so that the signal appears as an uninterrupted linear frequency modulated pulse sequence in the time domain. This baseband signal will then be upconverted to the satellite uplink frequency band for transmission. Its ultra-narrowband characteristics enable it to achieve reliable transmission with extremely low power in the transparent relay link of geostationary meteorological satellites.

[0095] In a preferred embodiment, for each symbol in the symbol sequence, determining the linear frequency modulation sweep direction based on its corresponding bit value includes:

[0096] Obtain the bit value corresponding to the currently unprocessed symbol in the symbol sequence;

[0097] Determine whether the bit value is a preset first bit value. If the bit value is a preset first bit value, then determine that the linear frequency modulation sweep direction of the current symbol is a positive sweep direction. The positive sweep direction means that the frequency increases linearly from low to high during the symbol duration.

[0098] If the bit value is a preset second bit value, then the linear frequency modulation sweep direction of the current symbol is determined to be a negative sweep direction, which means that the frequency decreases linearly from high to low during the symbol duration.

[0099] It should be noted that the system first obtains the bit value corresponding to the current symbol to be processed in the symbol sequence, and uses this as the sole basis for determining the frequency sweep direction; this determination process is essentially mapping binary information into a physical waveform in the time and frequency domain, which is the core step of the "bit to waveform" conversion in CSS modulation;

[0100] Determine if the current bit value is the preset first bit value (e.g., "0"). If so, determine that the linear frequency modulation sweep direction of the symbol is the positive sweep direction. That is, during the entire symbol duration, the signal frequency increases linearly from the starting frequency to the high frequency. This process is equivalent to drawing a diagonal line from the lower left to the upper right on the time-frequency plane. The instantaneous frequency of the positive sweep pulse increases uniformly with time, and its matched filter output will produce a sharp correlation peak in the time domain.

[0101] If the current bit value is a preset second bit value (e.g., "1"), then the linear frequency modulation sweep direction of the symbol is determined to be the negative sweep direction. That is, during the symbol duration, the signal frequency decreases linearly from the starting frequency to the low. This process is presented as a diagonal line from the upper left to the lower right on the time-frequency plane, which forms a mirror symmetry with the positive sweep pulse. The receiver uses the positive and negative sweep reference signals matched with the transmitter to perform correlation processing, which can accurately distinguish the two bit values ​​and achieve reliable demodulation. This bidirectional sweep mapping mechanism enables the CSS signal to maintain a high demodulation accuracy even under extremely low signal-to-noise ratio conditions.

[0102] In a preferred embodiment, the ultra-narrowband CSS baseband signal is upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, including:

[0103] The ultra-narrowband CSS baseband signal is input to a digital-to-analog converter and converted into a continuous analog baseband signal. It is then band-limited filtered by a pulse shaping filter to eliminate out-of-band spectral components, resulting in a processed analog baseband signal.

[0104] Based on the frequency planning of the uplink frequency band of geostationary meteorological satellites, the corresponding uplink local oscillator frequency is selected, and the processed analog baseband signal is orthogonally upconverted and mixed with the uplink local oscillator frequency to obtain the uplink intermediate frequency signal.

[0105] The uplink intermediate frequency signal is subjected to intermediate frequency bandpass filtering to remove the image frequency components and spurious signals generated during the mixing process, and the filtered uplink intermediate frequency signal is obtained.

[0106] Based on the target frequency of the uplink radio frequency band of the geostationary meteorological satellite, the radio frequency local oscillator signal is selected, and the filtered uplink intermediate frequency signal is mixed with the radio frequency local oscillator signal by a second upconversion to obtain the uplink radio frequency signal.

[0107] It should be noted that the ultra-narrowband CSS baseband signal is input to the digital-to-analog converter and converted into a continuous analog baseband signal. Then, it is band-limited filtered by a pulse shaping filter to eliminate out-of-band spectral components. This step restores the discrete signal in the digital domain to a continuous waveform in the analog domain. The pulse shaping filter acts like a "spectral gate," strictly limiting the signal energy within a preset bandwidth to prevent out-of-band spectral components from interfering with adjacent channels. It also provides a clean signal base for subsequent mixing.

[0108] Based on the frequency planning of the uplink frequency band of geostationary meteorological satellites, the corresponding uplink local oscillator frequency is selected. The processed analog baseband signal is then orthogonally upconverted and mixed with this local oscillator frequency to obtain the uplink intermediate frequency signal. The orthogonal upconversion adopts an I / Q two-way mixing architecture, which can effectively suppress image frequency components. Compared with single-way mixing, it can improve the image suppression ratio by tens of dB. For satellite links that need to be amplified by transparent transponders, this can avoid image interference from degrading the system signal-to-noise ratio.

[0109] The intermediate frequency (IF) signal is subjected to an IF bandpass filter to remove residual image frequency components and spurious signals generated during the mixing process. Although quadrature mixing has significantly suppressed the image, the amplitude and phase imbalance of the actual device will still leave a small amount of image energy. In addition, spurious signals introduced by factors such as local oscillator leakage and higher harmonics are also present. The IF bandpass filter serves as the second "spectrum cleaning" step to ensure that the signal entering the next mixing stage has sufficient spectral purity.

[0110] The radio frequency local oscillator signal is selected based on the target frequency of the uplink radio frequency band of the geostationary meteorological satellite. The filtered uplink intermediate frequency signal and the radio frequency local oscillator signal are then mixed by a second upconversion to obtain the uplink radio frequency signal. Its core advantage is that the frequency span of each mixing stage is small, the local oscillator design is easier to implement, and the filter is easier to manufacture. At the same time, the step-by-step filtering method can effectively suppress spurious signals at each frequency band node. The final output uplink radio frequency signal can be transmitted to the geostationary meteorological satellite after power amplification to complete the uplink injection of commands.

[0111] In a preferred embodiment, the processed analog baseband signal is orthogonally up-converted and mixed with the uplink local oscillator frequency to obtain an uplink intermediate frequency signal, including:

[0112] The processed analog baseband signal is separated into in-phase and quadrature components to obtain I-path baseband signal and Q-path baseband signal;

[0113] The local oscillator generates the local oscillator signal corresponding to the uplink local oscillator frequency, and the local oscillator signal is divided into two local oscillator signals with orthogonal phases by a 90-degree phase shifter, resulting in an in-phase local oscillator signal and a quadrature local oscillator signal, respectively.

[0114] The baseband signal of the I-path and the in-phase local oscillator signal are fed into the first mixer for mixing to obtain the in-phase intermediate frequency component;

[0115] The Q-band baseband signal and the quadrature local oscillator signal are fed into the second mixer for mixing to obtain quadrature intermediate frequency components.

[0116] The in-phase intermediate frequency component and the quadrature intermediate frequency component are superimposed and combined by a combiner to obtain the uplink intermediate frequency signal.

[0117] It should be noted that the processed analog baseband signal is separated into in-phase and quadrature components, resulting in I-channel and Q-channel baseband signals, respectively. This separation process essentially decomposes a single real signal into two quadrature signals with a 90-degree phase difference. The I-channel carries the amplitude information of the signal, while the Q-channel carries the phase information of the signal. Together, they completely characterize all the features of the baseband signal, providing a dual-channel input basis for subsequent quadrature mixing.

[0118] The local oscillator generates a local oscillator signal corresponding to the uplink local oscillator frequency. This local oscillator signal is then split into two orthogonal local oscillator signals by a 90-degree phase shifter, resulting in an in-phase local oscillator signal and a quadrature local oscillator signal, respectively. The 90-degree phase shifter ensures that the two local oscillator signals maintain a strict phase difference of one-quarter of a cycle. This is the core prerequisite for the quadrature upconversion architecture to suppress image frequencies. If the phase deviation between the two local oscillator signals deviates from 90 degrees, the image suppression capability will decrease significantly.

[0119] The I-channel baseband signal and the in-phase local oscillator signal are fed into the first mixer for mixing to obtain the in-phase intermediate frequency component; at the same time, the Q-channel baseband signal and the quadrature local oscillator signal are fed into the second mixer for mixing to obtain the quadrature intermediate frequency component; the two mixing channels are processed in parallel, each completing the frequency shift from baseband to intermediate frequency. The I-channel and Q-channel do not interfere with each other during the mixing process, and carry the in-phase and quadrature information of the original signal respectively.

[0120] The in-phase intermediate frequency (IF) component and the quadrature IF component are superimposed and combined by a combiner to obtain the uplink IF signal. The combined signal exhibits a single-sideband spectrum in the frequency domain. That is, the quadrature upconversion architecture physically eliminates the image frequency component that is inevitably generated by traditional single-channel mixing through the phase coordination of the I and Q channels. Compared with the single-channel mixing method, quadrature upconversion can improve the image rejection ratio by more than 30dB. For the uplink of geostationary meteorological satellites, this can effectively avoid image interference occupying valuable satellite relay bandwidth, while improving the demodulation signal-to-noise ratio at the receiver.

[0121] In a preferred embodiment, the onboard transparent transponder receives the uplink radio frequency signal and performs low-noise amplification, then downconverts it to an intermediate frequency (IF), and then upconverts it to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal, including:

[0122] The uplink radio frequency signal is acquired and then amplified by a satellite low-noise amplifier to obtain a low-noise amplified uplink radio frequency signal.

[0123] Based on the frequency relationship between the satellite uplink frequency band and intermediate frequency, the corresponding downlink local oscillator signal is selected, and the uplink radio frequency signal after low noise amplification and the downlink local oscillator signal are downconverted and mixed to obtain the downlink intermediate frequency signal.

[0124] Based on the target frequency of the downlink broadcast band of the geostationary meteorological satellite, the corresponding uplink local oscillator signal is selected, and the downlink intermediate frequency signal and the uplink local oscillator signal are upconverted and mixed to obtain the satellite downlink broadcast radio frequency signal.

[0125] It should be noted that the onboard transparent transponder first acquires the uplink radio frequency signal transmitted from the ground, and then performs low-noise power amplification through the satellite low-noise amplifier to obtain the low-noise amplified uplink radio frequency signal. The low-noise amplifier is the first active device in the onboard receiving link. Its core task is to boost the weak uplink signal to a usable power level with minimal additional noise. Since the uplink signal power has been significantly attenuated after propagating through long-distance free space, the noise figure of the low-noise amplifier directly determines the carrier-to-noise ratio of the entire transponder link. Therefore, selecting a high-gain, low-noise-figure amplifier is the key to ensuring the quality of subsequent transparent transponders.

[0126] Based on the frequency relationship between the satellite uplink frequency band and the intermediate frequency (IF), the corresponding downlink local oscillator (LO) signal is selected. The uplink RF signal, after low-noise amplification, is then downconverted and mixed with the LO signal to obtain the downlink IF signal. This step completes the first frequency shift from RF to IF. The principle for selecting the downlink LO frequency is to ensure that the mixed IF falls within the predetermined IF passband, while ensuring that the image frequency is effectively suppressed by the IF filter. Downconversion to IF is performed instead of direct downconversion to baseband because IF processing is easier to implement on-board with narrowband filtering and gain control, providing a stable signal base for subsequent upconversion.

[0127] Based on the target frequency of the downlink broadcast band of the geostationary meteorological satellite, the corresponding uplink local oscillator signal is selected. The downlink intermediate frequency signal and the uplink local oscillator signal are then upconverted and mixed to obtain the satellite downlink broadcast radio frequency signal. The signal is then moved from the on-board intermediate frequency to the local oscillator of the ground receiving band. The upconverted radio frequency signal enters a high-power amplifier for power amplification and is then radiated to the ground coverage area via broadcast. Throughout the entire process, the transparent transponder does not demodulate, decode, or store the signal; it only performs pure radio frequency operations such as amplification and frequency conversion. This "receive and transmit simultaneously" method minimizes the complexity of on-board processing and avoids the processing delay caused by on-board decoding, ensuring that commands can reach the terminal controlled equipment from the ground control center via the shortest path.

[0128] In a preferred embodiment, the down-converted signal is processed using positive and negative frequency sweep reference signals matched with the transmitter, despreading the down-converted signal into a narrowband pulse signal and demodulating it to produce a soft-decision bitstream, including:

[0129] The down-conversion signal is input to the positive and negative sweep frequency correlators, and sliding correlation operations are performed with the positive and negative sweep frequency reference signals, respectively, to obtain the correlation operation results.

[0130] Continuous peak detection is performed on the relevant calculation results, and the moment when the relevant peak appears within each symbol duration window is determined as the precise symbol synchronization point;

[0131] By comparing the peak output amplitudes of the positive and negative frequency sweep correlators at the symbol synchronization point, the bit determination results are obtained, including:

[0132] If the peak amplitude of the positive frequency sweep correlator is greater than that of the negative frequency sweep correlator, then the current symbol is determined to correspond to the preset first bit value;

[0133] If the peak amplitude of the negative frequency sweep correlator is greater than that of the positive frequency sweep correlator, then the current symbol is determined to correspond to the preset second bit value;

[0134] The amplitude difference between the peak values ​​of the two correlator outputs at each symbol synchronization point is extracted as soft-decision confidence information. The bit determination result is combined with the corresponding soft-decision confidence information to form a soft-decision bit stream.

[0135] It should be noted that the down-converted signal is simultaneously input into both the positive and negative sweep correlators, and sliding correlation operations are performed with the positive and negative sweep reference signals matched at the transmitter, respectively. This process is essentially about finding the hidden pulse signal in the up-converted signal. The positive sweep correlator specifically captures the linear frequency modulation component from low to high frequency, while the negative sweep correlator specifically captures the linear frequency modulation component from high to low frequency. The sliding correlation operation compresses the broadband CSS signal energy into an extremely narrow time-domain pulse by sliding point by point on the time axis, thereby achieving despreading.

[0136] Continuous peak detection is performed on the two correlation operation results. Within each symbol duration window, the moment when the correlation peak appears is determined as the precise symbol synchronization point. The moment when the correlation peak appears is the starting boundary of the current symbol. The precise locking of this moment is a prerequisite for subsequent bit determination. If there is a deviation in the symbol synchronization point, the correlator will sample in the wrong time window, directly causing bit misjudgment. Therefore, the accuracy of peak detection directly determines the reliability of the entire demodulation link.

[0137] The peak output amplitudes of the positive and negative frequency sweep correlators at the symbol synchronization point are compared to determine the bit value corresponding to the current symbol. If the peak amplitude of the positive frequency sweep correlator is greater than that of the negative frequency sweep correlator, the current symbol is determined to correspond to a preset first bit value; if the peak amplitude of the negative frequency sweep correlator is greater than that of the positive frequency sweep correlator, the current symbol is determined to correspond to a preset second bit value. The physical basis of this determination logic is that when the transmitter sends a positive frequency sweep symbol, the positive frequency sweep correlator outputs a strong correlation peak due to matching, while the negative frequency sweep correlator outputs a weak response due to mismatch, and vice versa. By comparing the relative magnitudes of the two peaks, the original bit information of the transmitter can be unambiguously restored.

[0138] The amplitude difference between the peak values ​​of the two correlators at each symbol synchronization point is extracted as soft-decision confidence information. The bit decision result is then combined with this confidence information to form a soft-decision bitstream. Unlike hard decision, which only outputs "0" or "1", soft decision retains a reliability measure for each bit. When the amplitude difference between the two peak values ​​is large, it indicates that the confidence of the bit decision is high, and the receiver can be almost certain of its accuracy. When the amplitudes of the two peak values ​​are close, it indicates that the bit is on the ambiguity boundary and has low confidence. This confidence information plays a crucial role in subsequent forward error correction decoding. The decoder can use this information to assign higher weights to high-confidence bits and focus on correcting low-confidence bits, thereby achieving near-limit decoding performance even under extremely low signal-to-noise ratio conditions.

[0139] In a preferred embodiment, the down-conversion signal is input to a positive sweep frequency correlator and a negative sweep frequency correlator, and sliding correlation operations are performed with the positive sweep frequency reference signal and the negative sweep frequency reference signal, respectively, to obtain the correlation operation results, including:

[0140] The down-converted signal is multiplied point by point with the positive sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the positive sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband positive pulse signal and obtaining the first correlation operation result of the positive sweep correlator containing the narrowband positive pulse signal.

[0141] The down-converted signal is multiplied point by point with the negative sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the negative sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband negative pulse signal, and obtaining the second correlation operation result of the negative sweep correlator outputting the narrowband negative pulse signal.

[0142] It should be noted that after multiplying the down-converted signal and the positive sweep reference signal point by point and then integrating and accumulating the results, when the sweep direction of any symbol in the received signal is consistent with the positive sweep reference signal, a correlation peak is output within the duration window of that symbol, thereby despreading the down-converted signal into a narrowband positive pulse signal, and obtaining the first correlation operation result output by the positive sweep correlator. The physical essence of this process is matched filtering—when the sweep direction of the received signal is completely consistent with the reference signal, the result of multiplying the two point by point remains the same sign throughout the entire symbol period, and after integration and accumulation, the energy is coherently superimposed, outputting a sharp correlation peak; while when the directions are inconsistent, the product results alternate between positive and negative, cancel each other out after integration, and the output approaches zero; therefore, the positive sweep correlator actually acts as a "directional filter," responding only to positive sweep symbols, compressing the originally wideband CSS signal into a narrowband pulse, and completing the despreading.

[0143] The down-converted signal and the negative sweep reference signal are multiplied point by point and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the negative sweep reference signal, the correlation peak is output within the duration window of that symbol, thereby despreading the down-converted signal into a narrowband negative pulse signal, and obtaining the second correlation operation result output by the negative sweep correlator. Its working principle is completely symmetrical with that of the positive sweep correlator. The frequency change direction of the negative sweep reference signal is mirrored and opposite to that of the positive sweep reference signal. Therefore, it only produces a strong correlation response for negative sweep symbols and outputs a near-zero value for positive sweep symbols. The two correlators work in parallel, which is equivalent to deploying two complementary "detectors" at the receiver to capture two possible sweep directions respectively.

[0144] The combination of point-by-point multiplication and integral accumulation essentially implements sliding correlation operation, that is, the reference signal slides gradually relative to the received signal on the time axis, and the correlation value is calculated at each possible time offset; when sliding to a certain offset, if the offset happens to correspond to the start time of a certain symbol and the frequency sweep direction matches, then all the products in the integration window have the same sign, the correlation value reaches the maximum, and a peak value is formed; the time of occurrence of this peak value precisely marks the position of the symbol on the time axis, and the polarity of the peak value (whether it comes from a positive or negative frequency sweep correlator) directly indicates the bit value carried by the symbol;

[0145] After the above processing, the first correlation operation result output by the positive frequency sweep correlator contains only narrowband positive pulse signals, and the second correlation operation result output by the negative frequency sweep correlator contains only narrowband negative pulse signals. The two results are strictly aligned in time, with the symbol duration as the window, but only one of them has a significant peak within the current symbol window, while the other remains at a low level. This "one high and one low" output pattern provides a clear and unambiguous basis for subsequent peak comparison and bit determination. At the same time, the amplitude difference between the two peaks directly constitutes the confidence information required for soft decision.

[0146] Example 2

[0147] Please see Figure 2 As shown, in another embodiment of the present invention, the present invention also discloses a remote control and telemetry method based on ultra-narrowband linear spread spectrum of geostationary meteorological satellites, comprising:

[0148] S1. The ground control center generates remote control or teleading command data, encapsulates the command data into a data frame containing the target address and check code, and performs forward error correction coding and repetition coding to obtain the bit stream to be modulated.

[0149] S2. The bit stream to be modulated is mapped into symbols, and each symbol is modulated using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite.

[0150] S3. The onboard transparent transponder receives the uplink radio frequency signal and performs low-noise amplification. After low-noise amplification, it is downconverted to intermediate frequency and then upconverted to satellite downlink broadcast frequency band to obtain satellite downlink broadcast radio frequency signal. After high-power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode or store the signal throughout the entire process.

[0151] S4. The ground receiving terminal receives the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and processes the down-converted signal using positive and negative sweep frequency reference signals matched with the transmitting end, despreads the down-converted signal into a narrowband pulse signal and demodulates the soft decision bit stream.

[0152] S5. Perform duplicate code merging and forward error correction decoding on the soft decision bitstream, and perform verification and address authentication on the decoded data frame to recover the remote control or teleadjustment command data; convert the recovered command data into control signals that can be recognized by the controlled device and output them to the connected controlled device to perform the corresponding operation.

[0153] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0154] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum, characterized in that, include: The instruction encoding and encapsulation module responds to the remote control or teleading instruction data generated by the ground control center, encapsulates the instruction data into a data frame containing the target address and check code, and performs forward error correction encoding and repetition encoding to obtain the bit stream to be modulated. The spread spectrum modulation transmission module is responsive to mapping the bit stream to be modulated into symbols, and modulating each symbol using a linear frequency modulation spread spectrum method to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is then upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite. The radio frequency signal broadcasting module responds to the onboard transparent transponder receiving the uplink radio frequency signal and performing low-noise amplification. After low-noise amplification, it is downconverted to intermediate frequency and then upconverted to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal. After high-power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode, or store the signal throughout the entire process. The soft decision bitstream generation module, in response to the ground receiving terminal receiving the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and uses positive and negative sweep frequency reference signals matched with the transmitting end to process the down-converted signal, despread the down-converted signal into a narrowband pulse signal and demodulate the soft decision bitstream; The instruction recovery module, in response to performing duplicate code merging and forward error correction decoding on the soft decision bitstream, and performing verification and address authentication on the decoded data frame, recovers the remote control or teleadjustment instruction data; converts the recovered instruction data into control signals recognizable by the controlled device and outputs them to the connected controlled device to perform corresponding operations.

2. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 1, characterized in that, The instruction data is encapsulated into a data frame containing the target address and a checksum, and forward error correction coding and repetition coding are performed to obtain the bit stream to be modulated, including: The ground control center generates remote control or teleading command data, adds a target address field to the command data, and the target address field supports unicast address, multicast address or broadcast address to obtain command data containing the target address; A frame header field is added to the instruction data containing the target address. The frame header field is used for frame synchronization and frame type identification to obtain instruction data containing a frame header. The checksum is calculated and appended to the instruction data containing the frame header to obtain a data frame containing the target address and the checksum; The complete data frame is channel-coded using a forward error correction coding method. A check bit is appended to the information bits of the data frame to obtain a forward error correction codeword. The forward error correction coding method includes Hamming code, BCH code, or convolutional code. The forward error correction codewords are repeatedly encoded to obtain several forward error correction codewords. Several identical forward error correction codewords are then concatenated in sequence to obtain the bit stream to be modulated.

3. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 2, characterized in that, The process involves mapping the bitstream to be modulated into symbols, and modulating each symbol using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal, including: The bit stream to be modulated is mapped to modulation symbols to obtain a symbol sequence; For each symbol in the symbol sequence, the linear frequency modulation sweep direction is determined according to its corresponding bit value, and the sweep direction includes positive sweep and negative sweep; Based on the sweep direction, determine the linear frequency modulation pulse corresponding to each symbol; The linear frequency modulated pulses corresponding to each symbol are sequentially connected on the time axis to obtain a continuous linear frequency modulated pulse sequence, which is then used as the ultra-narrowband CSS baseband signal.

4. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 3, characterized in that, For each symbol in the symbol sequence, the linear frequency modulation sweep direction is determined based on its corresponding bit value, including: Obtain the bit value corresponding to the currently unprocessed symbol in the symbol sequence; Determine whether the bit value is a preset first bit value. If the bit value is a preset first bit value, then determine that the linear frequency modulation sweep direction of the current symbol is a positive sweep direction. The positive sweep direction means that the frequency increases linearly from low to high during the symbol duration. If the bit value is a preset second bit value, then the linear frequency modulation sweep direction of the current symbol is determined to be a negative sweep direction, which means that the frequency decreases linearly from high to low during the symbol duration.

5. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 3, characterized in that, The ultra-narrowband CSS baseband signal is upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, including: The ultra-narrowband CSS baseband signal is input to a digital-to-analog converter and converted into a continuous analog baseband signal. It is then band-limited filtered by a pulse shaping filter to eliminate out-of-band spectral components, resulting in a processed analog baseband signal. Based on the frequency planning of the uplink frequency band of geostationary meteorological satellites, the corresponding uplink local oscillator frequency is selected, and the processed analog baseband signal is orthogonally upconverted and mixed with the uplink local oscillator frequency to obtain the uplink intermediate frequency signal. The uplink intermediate frequency signal is subjected to intermediate frequency bandpass filtering to remove the image frequency components and spurious signals generated during the mixing process, and the filtered uplink intermediate frequency signal is obtained. Based on the target frequency of the uplink radio frequency band of the geostationary meteorological satellite, the radio frequency local oscillator signal is selected, and the filtered uplink intermediate frequency signal is mixed with the radio frequency local oscillator signal by a second upconversion to obtain the uplink radio frequency signal.

6. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 5, characterized in that, The processed analog baseband signal is orthogonally up-converted and mixed with the uplink local oscillator frequency to obtain the uplink intermediate frequency signal, including: The processed analog baseband signal is separated into in-phase and quadrature components to obtain I-path baseband signal and Q-path baseband signal; The local oscillator generates the local oscillator signal corresponding to the uplink local oscillator frequency, and the local oscillator signal is divided into two local oscillator signals with orthogonal phases by a 90-degree phase shifter, resulting in an in-phase local oscillator signal and a quadrature local oscillator signal, respectively. The baseband signal of the I-path and the in-phase local oscillator signal are fed into the first mixer for mixing to obtain the in-phase intermediate frequency component; The Q-band baseband signal and the quadrature local oscillator signal are fed into the second mixer for mixing to obtain quadrature intermediate frequency components. The in-phase intermediate frequency component and the quadrature intermediate frequency component are superimposed and combined by a combiner to obtain the uplink intermediate frequency signal.

7. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 1, characterized in that, The onboard transparent transponder receives the uplink radio frequency signal and performs low-noise amplification. After low-noise amplification, it is down-converted to an intermediate frequency (IF), and then up-converted to the satellite downlink broadcast frequency band to obtain the satellite downlink broadcast radio frequency signal, including: The uplink radio frequency signal is acquired and then amplified by a satellite low-noise amplifier to obtain a low-noise amplified uplink radio frequency signal. Based on the frequency relationship between the satellite uplink frequency band and intermediate frequency, the corresponding downlink local oscillator signal is selected, and the uplink radio frequency signal after low noise amplification and the downlink local oscillator signal are downconverted and mixed to obtain the downlink intermediate frequency signal. Based on the target frequency of the downlink broadcast band of the geostationary meteorological satellite, the corresponding uplink local oscillator signal is selected, and the downlink intermediate frequency signal and the uplink local oscillator signal are upconverted and mixed to obtain the satellite downlink broadcast radio frequency signal.

8. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 1, characterized in that, The down-converted signal is processed using positive and negative frequency sweep reference signals matched with the transmitter. The down-converted signal is despread into a narrowband pulse signal and demodulated to produce a soft-decision bitstream, including: The down-conversion signal is input to the positive and negative sweep frequency correlators, and sliding correlation operations are performed with the positive and negative sweep frequency reference signals, respectively, to obtain the correlation operation results. Continuous peak detection is performed on the relevant calculation results, and the moment when the relevant peak appears within each symbol duration window is determined as the precise symbol synchronization point; By comparing the peak output amplitudes of the positive and negative frequency sweep correlators at the symbol synchronization point, the bit determination results are obtained, including: If the peak amplitude of the positive frequency sweep correlator is greater than that of the negative frequency sweep correlator, then the current symbol is determined to correspond to the preset first bit value; If the peak amplitude of the negative frequency sweep correlator is greater than that of the positive frequency sweep correlator, then the current symbol is determined to correspond to the preset second bit value; The amplitude difference between the peak values ​​of the two correlator outputs at each symbol synchronization point is extracted as soft-decision confidence information. The bit determination result is combined with the corresponding soft-decision confidence information to form a soft-decision bit stream.

9. The remote control and telemetry system based on geostationary meteorological satellite ultra-narrowband linear spread spectrum according to claim 8, characterized in that, The down-converted signal is input to the positive and negative sweep frequency correlators, and sliding correlation operations are performed with the positive and negative sweep frequency reference signals, respectively, to obtain the correlation results, including: The down-converted signal is multiplied point by point with the positive sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the positive sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband positive pulse signal and obtaining the first correlation operation result of the positive sweep correlator containing the narrowband positive pulse signal. The down-converted signal is multiplied point by point with the negative sweep reference signal and then integrated and accumulated. When the sweep direction of any symbol in the received signal is consistent with the negative sweep reference signal, the correlation peak value corresponding to the duration window of that symbol is output, thereby despreading the down-converted signal into a narrowband negative pulse signal, and obtaining the second correlation operation result of the negative sweep correlator outputting the narrowband negative pulse signal.

10. A remote control and telemetry method based on ultra-narrowband linear spread spectrum of geostationary meteorological satellites, employing the remote control and telemetry system based on ultra-narrowband linear spread spectrum of geostationary meteorological satellites as described in any one of claims 1-9, characterized in that, include: In response to the remote control or teleading command data generated by the ground control center, the command data is encapsulated into a data frame containing the target address and check code, and forward error correction coding and repetition coding are performed to obtain the bit stream to be modulated; The bit stream to be modulated is mapped into symbols, and each symbol is modulated using linear frequency modulation spread spectrum to generate an ultra-narrowband CSS baseband signal. The ultra-narrowband CSS baseband signal is then upconverted to the satellite uplink frequency band to obtain an uplink radio frequency signal, which is then amplified and transmitted to a geostationary meteorological satellite. The onboard transparent transponder receives the uplink radio frequency signal and amplifies it with low noise. After low noise amplification, it is downconverted to intermediate frequency and then upconverted to satellite downlink broadcast frequency band to obtain satellite downlink broadcast radio frequency signal. After high power amplification, it is broadcast to the ground coverage area. The onboard transparent transponder does not demodulate, decode or store the signal throughout the entire process. The ground receiving terminal receives the satellite downlink broadcast radio frequency signal, performs low-noise amplification and down-conversion processing to obtain a down-converted signal, and processes the down-converted signal using positive and negative sweep frequency reference signals matched with the transmitter, despreads the down-converted signal into a narrowband pulse signal and demodulates the soft decision bit stream. The soft-decision bitstream is subjected to duplicate code merging and forward error correction decoding. The decoded data frames are then checked and address authenticated to recover the remote control or teleadjustment command data. The recovered command data is converted into control signals that can be recognized by the controlled device and output to the connected controlled device to perform the corresponding operation.

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