Inter-satellite microwave measurement communication link signal generation and link establishment method

Abstract

The application discloses a kind of inter-satellite microwave measurement communication link signal generation and chain building method, comprising: generating transmitting signal based on direct sequence spread spectrum mode, and transmitting signal is divided into mutually orthogonal I branch and Q branch, and the spread spectrum code sequence of different length is modulated to two branches respectively;I branch is used as measurement branch, fixed modulation long code is used and binary offset subcarrier modulation mode is used, and measurement data frame with fixed frame length and information rate is loaded on I branch;Q branch is set to pilot mode or communication mode, short spread spectrum code is modulated in pilot mode and no data is loaded, long spread spectrum code is modulated in communication mode and communication data with configurable information rate is loaded;The start bit of spread spectrum code period of I branch and Q branch is aligned with the start bit of data frame header to the local maintained second pulse, and the generation of inter-satellite microwave measurement communication link transmitting signal is completed.The application can realize acquisition complexity and pseudo-range measurement accuracy under the condition of given bandwidth.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and in particular to a method for generating and establishing inter-satellite microwave measurement and communication link signals. Background Technology

[0002] With the vigorous development of various aerospace engineering applications and space science exploration missions, the number of spacecraft in orbit will continue to grow rapidly. To reduce satellites' dependence on ground-based telemetry and control equipment, space-based autonomous orbit determination has become an inevitable trend. Generally speaking, my country's BeiDou Global Navigation Satellite System, as well as GNSS systems such as GPS, GLONASS, and Galileo, serve as space-based spatiotemporal reference infrastructure, and their broadcast signals can meet the positioning and timing needs of most spacecraft. However, for high-orbit or deep-space application scenarios, the autonomous navigation needs of spacecraft cannot be well met by GNSS systems. In addition, with the on-orbit engineering application of high-performance atomic clocks, it is necessary to conduct on-orbit atomic clock performance evaluation and transmit high-precision time and frequency performance externally, requiring the construction of inter-satellite two-way time and frequency comparison links. Against this backdrop, inter-satellite microwave measurement and communication links will continue to play an important role.

[0003] Currently, inter-satellite microwave measurement and communication links mainly adopt a two-way one-way measurement mode. Satellites, based on their own maintained time references, transmit microwave signals to each other to obtain their respective pseudorange and carrier phase measurement information. By combining the measurement information from both sides and subtracting the influence of other spatial effects, distance and clock bias are decoupled. The transmitted signal is a direct sequence spread spectrum signal, typically a QPSK modulated signal. One path is mainly used for ranging and exchanging measurement information, while the other path is used for inter-satellite communication.

[0004] The relatively large radial velocities and accelerations between satellites, coupled with the high Ka-band carrier frequencies used to improve antenna gain, result in inter-satellite microwave measurement and communication links facing Doppler fluctuations on the order of MHz and Doppler change rates on the order of kHz / s, posing challenges to receiver acquisition and processing. To address this challenge, two main approaches exist in signal processing and link establishment: one is to rely on externally provided dynamic auxiliary information to reduce the Doppler search range, and the other is to use shorter period spreading codes to reduce the code phase search range. However, the former relies on auxiliary information, reducing system reliability, while the latter, using short codes, introduces near-far effects and complex data bit synchronization issues. Furthermore, to reduce signal acquisition complexity, the traditional BPSK spreading modulation scheme is currently widely used, but this is not optimal for pseudorange measurement accuracy. Summary of the Invention

[0005] To address the aforementioned issues, this invention proposes a method for generating and establishing inter-satellite microwave measurement and communication links. By employing code length switching and data modulation switching mechanisms, it resolves the contradiction between acquisition computing resource consumption and code isolation during system operation. Furthermore, it improves pseudorange measurement accuracy by optimizing the spread spectrum modulation method of the measurement branch. Through the signaling interaction mechanism of the measurement branch, it enables on-demand switching of the signal system and allows the link layer to autonomously complete the closed-loop control of the link establishment process.

[0006] The technical solution adopted in this invention is as follows: A method for generating signals for an inter-satellite microwave measurement and communication link includes: The transmitted signal is generated based on the direct sequence spread spectrum method and divided into mutually orthogonal I-branch and Q-branch. Spread code sequences of different lengths are modulated onto the two branches respectively. The I branch is used as the measurement branch, with a fixed modulation long code and a binary offset subcarrier modulation method. Measurement data frames with fixed frame length and information rate are loaded on the I branch. Set the Q branch to pilot mode or communication mode. In pilot mode, a short spreading code is modulated and no data is loaded. In communication mode, a long spreading code is modulated and communication data with a configurable information rate is loaded. Align the start bit of the spreading code period of both the I and Q branches with the start bit of the data frame header to the locally maintained second pulse to complete the generation of the transmission signal for the inter-satellite microwave measurement and communication link.

[0007] Furthermore, the step of modulating the two branches with spreading code sequences of different lengths includes: setting two types of spreading code sequences, short spreading code and long spreading code, with the I branch fixedly modulating the long spreading code, and the Q branch modulating the short spreading code in pilot mode or the long spreading code in communication mode.

[0008] Furthermore, the measurement data frame loaded on the I branch includes: a field characterizing the locking state of the I branch received by the local satellite, a field characterizing the carrier-to-noise ratio of the I branch received by the local satellite, a field characterizing the signal mode of the Q branch currently transmitted by the local satellite, and a field characterizing the transmission rate level of the Q branch currently transmitted by the local satellite.

[0009] Furthermore, the Q branch employs binary phase shift keying spread spectrum modulation in both pilot mode and communication mode for signal modulation.

[0010] A method for establishing an inter-satellite microwave measurement and communication link includes: In the initial state of link establishment, the Q branch of the satellite transmitting to the receiving satellite is in pilot mode, and the orthogonal I and Q branch signals are used. After the receiving satellite captures and stably tracks the Q-branch pilot mode signal transmitted by the initiating satellite, it performs synchronization and tracking of the I-branch signal and feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite. Based on the feedback information from the receiving satellite, the initiating satellite switches its own transmitted Q branch to communication mode and configures the corresponding transmission rate, while updating the relevant Q branch information in the I branch measurement data frame. The receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite, completes the reception and demodulation of I and Q-branch signals, and establishes an inter-satellite microwave measurement and communication link.

[0011] Furthermore, after the receiving satellite captures the Q-branch pilot mode signal transmitted by the initiating satellite, it first performs traction and tracking operations on the signal; after the parameters of the tracking loop converge, it enters a stable tracking state of the Q-branch pilot mode signal, and then performs synchronization and tracking operations on the I-branch signal.

[0012] Furthermore, when the receiving satellite performs the synchronization operation on the I-branch signal, it first completes the code phase probe and determination of the I-branch, and then performs bit synchronization and frame synchronization of the I-branch signal; after completing the synchronization and tracking of the I-branch signal, it then feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite.

[0013] Furthermore, the receiving star feeds back the locking status and carrier-to-noise ratio information of the I branch to the initiating star through the measurement data frames of the I branch in the orthogonal I and Q branches transmitted by itself, and the locking status includes two status indicators: unlocked and locked.

[0014] Furthermore, based on the feedback information from the receiving satellite, the initiating satellite switches its own transmitted Q-branch to communication mode and configures the corresponding transmission rate. At the same time, it updates the relevant Q-branch information in the I-branch measurement data frame, including: the initiating satellite matches and configures the corresponding transmission rate level in the Q-branch communication mode according to the specific value of the I-branch carrier-to-noise ratio fed back by the receiving satellite, and writes the updated Q-branch signal mode and transmission rate level information into its own transmitted I-branch measurement data frame to complete the information update.

[0015] Furthermore, the receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite to complete the reception and demodulation of I and Q-branch signals. This includes: after adjusting the receiving parameters based on the Q-branch related information in the updated I-branch measurement data frame from the initiating satellite, the receiving satellite uses its own tracking loop for the I-branch signal from the initiating satellite as an aid to receive and demodulate the Q-branch communication mode signal after the initiating satellite has switched.

[0016] The beneficial effects of this invention are as follows: 1. In this invention, since short code signals only appear in the initial acquisition stage, and long codes are used thereafter, a balance is achieved between the complexity of initial signal acquisition and the isolation between different users in the inter-satellite link establishment scenario. This invention introduces the BOC modulation method used in modern GNSS signals into the inter-satellite link measurement branch, thereby significantly improving the pseudorange measurement accuracy without increasing hardware specifications such as transmit power and bandwidth. The inter-satellite link transmitter and receiver use information exchange in the I branch to automatically complete the step-by-step synchronization from coarse to fine, signal mode switching and communication rate negotiation, and no ground manual intervention is required in the link establishment process.

[0017] 2. In the initial link establishment stage of this invention, the Q branch is in pilot mode. The short code mode reduces the receiver's code phase search range to 1 / 10 of that of the long code. After disabling data modulation, at least half of the acquisition time can be saved, reducing the total acquisition time to 1 / 20 of that in communication mode. After acquisition, the Q branch switches to long code, which can improve the code isolation by about 7dB, thereby reducing the interference of strong signals on other potential link establishment objects within the beam. The I branch, as the signal measurement branch, uses BOC modulation to make full use of RF bandwidth resources and improve pseudorange measurement accuracy. Compared with BPSK modulation, the pseudorange measurement accuracy is expected to be equivalently improved by 8dB. Attached Figure Description

[0018] Figure 1 This is a flowchart of the inter-satellite microwave measurement and communication link establishment method according to Embodiment 2 of the present invention.

[0019] Figure 2 This is a schematic diagram of the I-branch message frame in Embodiment 2 of the present invention.

[0020] Figure 3 This is a spectrum diagram of the I and Q branches of the present invention, according to Embodiment 2 of the present invention. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] Example 1 This embodiment provides a method for generating signals for an inter-satellite microwave measurement and communication link, including: The transmitted signal is generated based on the direct sequence spread spectrum method and divided into mutually orthogonal I-branch and Q-branch. Spread code sequences of different lengths are modulated onto the two branches respectively. The I branch is used as the measurement branch, with a fixed modulation long code and a binary offset subcarrier modulation method. Measurement data frames with fixed frame length and information rate are loaded on the I branch. Set the Q branch to pilot mode or communication mode. In pilot mode, a short spreading code is modulated and no data is loaded. In communication mode, a long spreading code is modulated and communication data with a configurable information rate is loaded. Align the start bit of the spreading code period of both the I and Q branches with the start bit of the data frame header to the locally maintained second pulse to complete the generation of the transmission signal for the inter-satellite microwave measurement and communication link.

[0023] It should be noted that this method achieves integrated signal design for inter-satellite measurement and communication through functional differentiation of orthogonal branches. The long spreading code combined with binary offset subcarrier modulation effectively improves the measurement accuracy of the measurement branch. The dual-mode design of the Q branch takes into account both the signal acquisition requirements in the early stage of link establishment and the communication transmission requirements after link establishment. The precise alignment of the second pulse ensures the synchronization of the I and Q signals, improving the consistency and stability of inter-satellite signal transmission.

[0024] Preferably, the two branches are modulated with spreading code sequences of different lengths, including setting two types of spreading code sequences: short spreading code and long spreading code. The I branch is fixed to modulate the long spreading code, while the Q branch modulates the short spreading code in pilot mode or the long spreading code in communication mode.

[0025] Specifically, the spreading code sequence is first divided into two levels: short spreading code and long spreading code. Then, the corresponding spreading code is assigned and modulated according to the functional positioning of the I and Q branches. The long spreading code is fixedly assigned to the measurement-dedicated I branch. For the Q branch, the spreading code is switched and modulated according to its actual working mode. When the Q branch is in pilot mode, the short spreading code is modulated for it, and when the Q branch switches to communication mode, the long spreading code is modulated for it.

[0026] It should be noted that the design of two spread spectrum codes avoids the increased signal modulation complexity caused by too many spread spectrum code types. Combined with the targeted code length matching of the branch functions, the long spread spectrum code of the measurement branch ensures the accuracy and anti-interference of measurement data transmission, the short spread spectrum code of the pilot mode effectively reduces the difficulty of signal acquisition, and the long spread spectrum code of the communication mode improves the reliability of communication data transmission, realizing the rational use of code length resources.

[0027] Preferably, the measurement data frame loaded on the I branch includes: a field characterizing the locking state of the I branch received by the local satellite, a field characterizing the carrier-to-noise ratio of the I branch received by the local satellite, a field characterizing the signal mode of the Q branch currently being transmitted by the local satellite, and a field characterizing the transmission rate level of the Q branch currently being transmitted by the local satellite.

[0028] Specifically, when designing the structure of the I-branch measurement data frame, multiple information fields are preset within the frame. Some of these fields are used to characterize the satellite's reception status of the I-branch signal of the link establishment target, specifically including the lock status field and the carrier-to-noise ratio field. The remaining fields are used to characterize the working status of the satellite's own Q-branch transmission, specifically including the signal mode field and the transmission rate level field. The fields are integrated in an orderly manner according to the preset frame structure. After the measurement data frame is constructed, it is loaded into the I-branch and transmitted synchronously with the measurement branch signal.

[0029] It should be noted that by integrating key interactive information for inter-satellite link establishment through measurement data frames, both parties can achieve accurate feedback on status and parameters through measurement branches, eliminating the need to build a dedicated feedback signaling link. This simplifies the structure of inter-satellite signaling interaction, improves the efficiency and relevance of information transmission during link establishment, and the clear division of each field allows both parties to quickly parse effective information, reducing the time spent on information processing.

[0030] Preferably, the Q branch employs binary phase-shift keying (BPSK) spread spectrum modulation for signal modulation in both pilot and communication modes. Specifically, when designing the spread spectrum modulation for the Q branch, its modulation method is uniformly set to binary phase-shift keying. When the Q branch operates in pilot mode, this modulation method is used to process the signal after completing short spreading code modulation. When the Q branch switches to communication mode, after completing long spreading code modulation and loading communication data, this modulation method is still used for further signal processing, ensuring the consistency of the modulation method across different operating modes of the branch throughout the entire process.

[0031] It should be noted that unifying the modulation methods of different modes of the Q branch avoids the increased complexity of modulation and demodulation caused by changes in modulation methods during mode switching, reduces the signal processing difficulty and equipment resource consumption at the receiver, and the binary phase shift keying modulation method adapts to the wireless transmission requirements of inter-satellite links, which can ensure the signal transmission stability of different modes of the Q branch and improve the demodulation success rate of the signal.

[0032] This embodiment also provides a method for establishing an inter-satellite microwave measurement and communication link, including: In the initial state of link establishment, the Q branch of the satellite transmitting to the receiving satellite is in pilot mode, and the orthogonal I and Q branch signals are used. After the receiving satellite captures and stably tracks the Q-branch pilot mode signal transmitted by the initiating satellite, it performs synchronization and tracking of the I-branch signal and feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite. Based on the feedback information from the receiving satellite, the initiating satellite switches its own transmitted Q branch to communication mode and configures the corresponding transmission rate, while updating the relevant Q branch information in the I branch measurement data frame. The receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite, completes the reception and demodulation of I and Q-branch signals, and establishes an inter-satellite microwave measurement and communication link.

[0033] It should be noted that this link establishment method is based on the aforementioned signal generation method to build the link establishment process, making the signal system highly compatible with the link establishment steps. It relies on the Q-branch pilot mode to achieve rapid signal acquisition and tracking, effectively reducing the signal processing difficulty in the early stage of link establishment. The link establishment parameters are fed back and updated through the measurement branch, realizing the coordinated advancement of measurement function and link establishment process. This allows the link establishment process to be dynamically adjusted according to the actual signal reception status, greatly improving the success rate and stability of inter-satellite link establishment.

[0034] Preferably, after receiving the Q-branch pilot mode signal transmitted by the satellite, the signal is first pulled and tracked; after the parameters of the tracking loop converge, the Q-branch pilot mode signal is entered into a stable tracking state, and then the synchronization and tracking operation of the I-branch signal is performed.

[0035] Specifically, after the receiving satellite acquires the Q-branch pilot mode signal transmitted by the initiating satellite through the signal acquisition module, it immediately starts the traction and tracking module to perform traction operation on the signal, gradually guiding the signal tracking loop to converge. At the same time, it monitors the changes of various parameters of the tracking loop in real time. When the loop parameters reach the convergence state, it is determined that the Q-branch pilot mode signal has entered a stable tracking state. At this time, the synchronization and tracking related operations of the I-branch signal transmitted by the initiating satellite are started.

[0036] It should be noted that by performing a step-by-step operation of first traction tracking and then stable tracking, the tracking accuracy of the receiving satellite for the Q-branch pilot mode signal is guaranteed, allowing the Q-branch to form a stable signal reference. This provides a reliable foundation for the subsequent synchronization and tracking of the I-branch signal, avoids the synchronization failure problem caused by directly operating the I-branch signal, and effectively improves the success rate of I-branch signal synchronization and tracking.

[0037] Preferably, when the receiving satellite performs synchronization operation on the I-branch signal, it first completes the code phase probe and determination of the I-branch, and then performs bit synchronization and frame synchronization of the I-branch signal; after completing the synchronization and tracking of the I-branch signal, it then feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite.

[0038] Specifically, when the receiving satellite performs I-branch signal synchronization operation based on the stably tracked Q-branch signal, it first performs multiple rounds of code phase probing on the long spreading code of the I-branch. The accurate code phase is determined by the probing results to complete the code phase synchronization. Then, it continues to perform bit synchronization operation on the I-branch signal to achieve precise alignment at the signal bit level. Next, it performs frame synchronization operation to ensure that the measurement data frames of the receiving end and the transmitting end are precisely synchronized. After completing the full-process synchronization of the I-branch signal, it continues to track the signal. After the tracking state is stable, it feeds back the locking status of the I-branch signal and carrier-to-noise ratio related information to the initiating satellite.

[0039] It should be noted that the step-by-step synchronization operation effectively solves the problem of multiple possible code phases caused by the long spreading code of the I branch, gradually improving the synchronization accuracy of the I branch signal and making the signal tracking more stable after synchronization. At the same time, the status feedback is performed after the synchronization tracking is completed, avoiding the deviation of the feedback information due to the instability of the signal status, ensuring the accuracy of the feedback information, and providing a reliable basis for the subsequent parameter adjustment of the initiating satellite.

[0040] Preferably, the receiving satellite feeds back the locking status and carrier-to-noise ratio information of the I branch of the initiating satellite, including the measurement data frames of the I branch in the orthogonal I and Q branches transmitted by itself, and feeds back the locking status and carrier-to-noise ratio information of the I branch of the initiating satellite to the initiating satellite. The locking status includes two status indicators: unlocked and locked.

[0041] Specifically, after the receiving satellite completes the synchronization and tracking of the I-branch signal of the initiating satellite, it writes the locking status flag and carrier-to-noise ratio related data of the initiating satellite's I-branch signal into the corresponding field of its own transmitted I-branch measurement data frame according to the actual signal reception status. The locking status is set with only two flags: unlocked and locked. The corresponding flag is selected and written according to the actual reception result. Then, the I-branch measurement data frame loaded with the feedback information is transmitted to the initiating satellite along with its own I-branch signal to complete the transmission of the feedback information.

[0042] It should be noted that by using the measurement data frames of the measurement branch to complete the feedback information transmission, there is no need to build an additional feedback signaling link, which further simplifies the signal transmission architecture for inter-satellite link establishment, reduces the hardware and software resource consumption of the equipment, and the simplified identification of the lock status allows the initiating satellite to quickly parse the receiving status, improving the information exchange efficiency during the link establishment process. The accurate feedback of the carrier-to-noise ratio data provides key data support for the initiating satellite's transmission rate configuration.

[0043] Preferably, the initiating satellite switches its own transmitted Q-branch to communication mode and configures the corresponding transmission rate based on the feedback information from the receiving satellite. At the same time, it updates the relevant information of the Q-branch in the I-branch measurement data frame. This includes the initiating satellite matching and configuring the corresponding transmission rate level in the Q-branch communication mode based on the specific value of the I-branch carrier-to-noise ratio fed back by the receiving satellite. The updated Q-branch signal mode and transmission rate level information are then written into the I-branch measurement data frame it transmits to complete the information update.

[0044] Specifically, the initiating satellite receives and parses the specific carrier-to-noise ratio (CNR) value of the I-branch fed back by the receiving satellite. Based on the pre-set CNR and transmit rate level matching rules of the inter-satellite link transmission characteristics, it matches and configures the corresponding transmit rate level for the Q-branch communication mode. At the same time, it accurately writes the signal mode after its own Q-branch switching and the configured transmit rate level information into the corresponding fields of the I-branch measurement data frame it transmits, completing the update of the Q-branch related information in the measurement data frame. Then, it transmits the updated I-branch signal to the receiving satellite.

[0045] It should be noted that the transmission rate of the Q-branch is dynamically configured according to the actual carrier-to-noise ratio, so that the transmission rate is adapted to the actual transmission status of the inter-satellite link. This avoids the problems of low transmission efficiency or high bit error rate caused by fixed rate, and improves the reliability and efficiency of communication data transmission. At the same time, the updated information is written into the measurement data frame, which ensures the relevance and accuracy of information transmission, allowing the receiving satellite to quickly obtain the latest operating parameters of the Q-branch and reduce the time spent on parameter parsing.

[0046] Preferably, the receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite to complete the reception and demodulation of I and Q-branch signals. This includes the receiving satellite adjusting its receiving parameters based on the Q-branch related information in the updated I-branch measurement data frame from the initiating satellite, and then using its own tracking loop for the I-branch signal from the initiating satellite as an aid to receive and demodulate the Q-branch communication mode signal after the initiating satellite has switched.

[0047] Specifically, the receiving satellite captures and parses the updated I-branch measurement data frames from the initiating satellite, accurately extracting the signal mode and transmission rate level information of the Q-branch. Based on this information, it adjusts its own receiving and demodulation parameters to match the signal characteristics of the Q-branch communication mode. When receiving and demodulating the Q-branch communication mode signal, it calls its own tracking loop for the I-branch signal of the initiating satellite as an aid, relying on the stable tracking state of the tracking loop to improve the receiving and demodulation accuracy of the Q-branch signal.

[0048] It should be noted that by using the stable tracking loop of the I branch to assist the demodulation of the Q branch, the signal reference role of the measurement branch is fully utilized, effectively improving the demodulation success rate and accuracy of the Q branch communication mode signal. At the same time, the receiving parameters are adjusted according to the actual Q branch parameters to ensure a high degree of matching between the parameters of the receiving end and the transmitting end, thus guaranteeing the transmission quality of the inter-satellite communication link. This enables the measurement branch and the communication branch to work together, improving the overall performance of the inter-satellite microwave measurement and communication link.

[0049] Example 2 This embodiment provides a signaling system for on-demand switching of pilot signals and communication branches, and presents a receiver-guided link establishment process and a handshake mechanism between the transmitter and receiver. The signaling system proposed in this embodiment has the following characteristics: 1) The transmitted signal adopts the direct sequence spread spectrum signal system, which is divided into two mutually orthogonal components, I and Q, which are modulated with different spreading code sequences respectively; 2) The spreading code length is divided into two levels, one level is a short code (e.g., length is 1023), and the other level is a long code (e.g., length is 10230). 3) The I branch is used as the measurement component. The spreading code is a fixed long code, and the modulation method is BOC modulation. That is, a binary offset subcarrier is modulated on the basis of the traditional BPSK system to achieve higher pseudorange measurement accuracy. 4) I-branch modulation measurement data frame, with fixed frame length and information rate. The measurement data frame contains fields characterizing the locking state and carrier-to-noise ratio of the I-branch of the local satellite receiving the link establishment object, as well as fields characterizing the current transmission Q-branch signal mode and Q-branch transmission rate level of the local satellite. 5) The Q branch can operate in pilot mode or communication mode. When in pilot mode, no data modulation is performed and short code is used for spreading. When in communication mode, communication data modulation is performed, the information rate level can be configured, and long code is used for spreading. 6) Whether the Q-branch is used as a communication component or a pilot component, the spread spectrum modulation method is BPSK; 7) When the transmitter generates I and Q signals, the start bit of the spreading code period and the start bit of the data frame header of the two signals are aligned with the locally maintained second pulse.

[0050] In this embodiment, a frequency-division full-duplex two-way one-way measurement system is adopted between satellites. Assuming the two satellites to be linked are denoted as Satellite A and Satellite B, two-way link establishment needs to be completed simultaneously: A transmitting and B receiving, and B transmitting and A receiving. Considering the symmetry of the two-way link, without loss of generality, the link establishment process for A transmitting and B receiving is detailed below. The process for B transmitting and A receiving is similar, only in the opposite direction. The link establishment process is as follows: Figure 1 As shown, the main steps include: 1) Satellite A transmits microwave measurement signals to Satellite B in accordance with the signal system described above. Initially, the Q branch of the transmission is in pilot mode, and the field in the I branch message transmitted by Satellite B that represents the locking status of its own reception of the I branch signal of Satellite A is set to "unlocked". 2) Satellite B captures the Q-branch pilot mode signal transmitted by Satellite A. Compared with the Q-branch communication mode and the I-branch signal, this mode has a shorter code length and no data modulation or subcarrier modulation, which significantly reduces the complexity of signal acquisition. 3) After B satellite completes the acquisition of the Q branch signal, it performs traction and tracking of the Q branch pilot mode signal. After the loop parameters converge, it enters a stable tracking state. 4) After satellite B stabilizes its tracking of the Q branch signal, it synchronizes the I branch BOC modulated signal. Since the I branch code period is longer, there are multiple possibilities for its code phase. First, it is necessary to complete the trial of the I branch code phase and complete the determination of the I branch code phase. 5) After determining the phase of the I-branch code, satellite B switches from tracking the Q-branch signal to tracking the I-branch signal. After completing the bit synchronization and frame synchronization of the I-branch signal, the field in the transmitted I-branch message that represents the locking status of its own received A-satellite I-branch signal is set to "locked". The carrier-to-noise ratio of the received A-satellite I-branch signal is given in the I-branch message. 6) After receiving the lock status flag from the I branch of satellite B, satellite A switches the mode of its own transmitted Q branch signal to communication mode, sets the Q branch transmission communication rate level according to the received carrier-to-noise ratio fed back by satellite B, and updates the fields in the I branch transmission message that represent the current Q branch signal mode and Q branch communication rate level accordingly. 7) Satellite B receives the Q branch operating mode and communication rate level information given by Satellite A's I branch message, adjusts the receiving parameters, and uses the I branch tracking loop to assist the Q branch in receiving and demodulating data according to the corresponding communication rate level, thus completing the stable link establishment of the I and Q signals transmitted by Satellite A and received by Satellite B.

[0051] Example 3 This embodiment designs a deep-space inter-satellite link signal system based on Embodiment 2. The I branch uses BOC(10,5), meaning a spreading code rate of 5.115 Mcps and a subcarrier frequency of 10.23 MHz. The Q branch uses BPSK(5) modulation, meaning a spreading code rate of 5.115 Mcps and no subcarrier modulation. The pilot mode of the Q branch uses a short code with a length of 1023 bits and a code period of 0.2 ms. The communication mode of the Q branch and the I branch use a long code with a length of 10230 bits and a code period of 2 ms. The message information rate of the I branch is 250 bps, which, after channel coding, results in a symbol rate of 500 sps. Therefore, one data modulation symbol corresponds exactly to one code period.

[0052] Table 1 - Signal System Parameters for Implementation Examples

[0053] Figure 2 An example of the I-branch message arrangement scheme is given, which reserves fields representing the transmit signal mode and rate level of the Q-branch of the local satellite, as well as the lock-in status and carrier-to-noise ratio of the I-branch of the receiving link establishment target, thereby enabling support for Figure 1 The chain-building interaction process is given.

[0054] Figure 3 The normalized spectra of the I and Q branches are given. It can be seen that the I branch uses BOC modulation and has more high-frequency signal components, thus achieving higher pseudorange measurement accuracy.

[0055] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

[0056] It should be noted that, for the sake of simplicity, the foregoing method embodiments are described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

Claims

1. A method for generating signals for an inter-satellite microwave measurement and communication link, characterized in that, include: The transmitted signal is generated based on the direct sequence spread spectrum method, and the transmitted signal is divided into mutually orthogonal I-branch and Q-branch. The two branches are modulated with spreading code sequences of different lengths respectively. The I branch is used as the measurement branch, with a fixed modulation long code and a binary offset subcarrier modulation method. Measurement data frames with fixed frame length and information rate are loaded on the I branch. Set the Q branch to pilot mode or communication mode. In pilot mode, a short spreading code is modulated and no data is loaded. In communication mode, a long spreading code is modulated and communication data with a configurable information rate is loaded. Align the start bit of the spreading code period of both the I and Q branches with the start bit of the data frame header to the locally maintained second pulse to complete the generation of the transmission signal for the inter-satellite microwave measurement and communication link.

2. The method for generating inter-satellite microwave measurement and communication link signals according to claim 1, characterized in that, The method of modulating the two branches with different lengths of spreading code sequences includes: setting two types of spreading code sequences, short spreading code and long spreading code, with the I branch fixed to modulate the long spreading code, and the Q branch modulating the short spreading code in pilot mode or the long spreading code in communication mode.

3. The method for generating inter-satellite microwave measurement and communication link signals according to claim 1, characterized in that, The measurement data frame loaded on the I branch includes: a field characterizing the locking state of the I branch received by the local satellite, a field characterizing the carrier-to-noise ratio of the I branch received by the local satellite, a field characterizing the signal mode of the Q branch currently being transmitted by the local satellite, and a field characterizing the transmission rate level of the Q branch currently being transmitted by the local satellite.

4. The method for generating inter-satellite microwave measurement and communication link signals according to claim 1, characterized in that, The Q branch uses binary phase shift keying spread spectrum modulation for signal modulation in both pilot mode and communication mode.

5. A method for establishing an inter-satellite microwave measurement and communication link, using the inter-satellite microwave measurement and communication link signal generation method as described in claim 1, characterized in that, The chain establishment method includes: In the initial state of link establishment, the Q branch of the satellite transmitting to the receiving satellite is in pilot mode, and the orthogonal I and Q branch signals are used. After the receiving satellite captures and stably tracks the Q-branch pilot mode signal transmitted by the initiating satellite, it performs synchronization and tracking of the I-branch signal and feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite. Based on the feedback information from the receiving satellite, the initiating satellite switches its own transmitted Q branch to communication mode and configures the corresponding transmission rate, while updating the relevant Q branch information in the I branch measurement data frame. The receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite, completes the reception and demodulation of I and Q-branch signals, and establishes an inter-satellite microwave measurement and communication link.

6. The method for establishing an inter-satellite microwave measurement and communication link according to claim 5, characterized in that, After the receiving satellite captures the Q-branch pilot mode signal transmitted by the initiating satellite, it first performs traction and tracking operations on the signal; after the parameters of the tracking loop converge, it enters a stable tracking state of the Q-branch pilot mode signal, and then performs synchronization and tracking operations on the I-branch signal.

7. The method for establishing an inter-satellite microwave measurement and communication link according to claim 5, characterized in that, When the receiving satellite performs the synchronization operation on the I-branch signal, it first completes the code phase probe and determination of the I-branch, and then performs bit synchronization and frame synchronization of the I-branch signal. After completing the synchronization and tracking of the I-branch signal, it feeds back the locking status and carrier-to-noise ratio information of the I-branch to the initiating satellite.

8. The method for establishing an inter-satellite microwave measurement and communication link according to claim 5, characterized in that, The receiving satellite feeds back the locking status and carrier-to-noise ratio information of the I branch to the initiating satellite through the measurement data frames of the I branch in the orthogonal I and Q branches transmitted by itself, and the locking status includes two status indicators: unlocked and locked.

9. The method for establishing an inter-satellite microwave measurement and communication link according to claim 5, characterized in that, The initiating satellite switches its own Q-branch to communication mode and configures the corresponding transmission rate based on the feedback information from the receiving satellite. At the same time, it updates the relevant Q-branch information in the I-branch measurement data frame, including: the initiating satellite matches and configures the corresponding transmission rate level in the Q-branch communication mode based on the specific value of the I-branch carrier-to-noise ratio fed back by the receiving satellite, and writes the updated Q-branch signal mode and transmission rate level information into the I-branch measurement data frame it transmits to complete the information update.

10. The method for establishing an inter-satellite microwave measurement and communication link according to claim 5, characterized in that, The receiving satellite adjusts its receiving parameters based on the updated I-branch information from the initiating satellite to complete the reception and demodulation of I and Q-branch signals. This includes: after adjusting the receiving parameters based on the Q-branch related information in the updated I-branch measurement data frame from the initiating satellite, the receiving satellite uses its own tracking loop for the I-branch signal from the initiating satellite as an aid to receive and demodulate the Q-branch communication mode signal after the initiating satellite has switched.

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