Underground space pseudolite dual-frequency positioning system

Abstract

This invention relates to a pseudosatellite dual-frequency positioning system for underground space, belonging to the field of pseudosatellite positioning technology. The system includes a dual-frequency signal unit, a two-point coordination unit, a clock calibration unit, and a positioning calculation unit. The dual-frequency signal unit generates and processes dual-frequency signals based on the signal format of a satellite navigation system, generating a homogeneous dual-frequency coded signal. The two-point coordination unit performs noise reduction and multipath suppression processing, power adaptation, and transmission on this signal, generating a dual-frequency split-radius navigation signal. The clock calibration unit performs clock synchronization calibration in conjunction with an external time reference, generating a clock-synchronized navigation signal. The positioning calculation unit extracts and calculates pseudorange, generating an underground space positioning calculation signal. This invention is adaptable to the complex environment of underground spaces, achieving underground space positioning through the collaborative work of each unit.

Description

Technical Field

[0001] This invention belongs to the field of pseudo-satellite positioning technology, specifically relating to an underground space pseudo-satellite dual-frequency positioning system. Background Technology

[0002] As my country's underground space development and utilization enters a stage of large-scale and diversified development, the construction scale of various enclosed underground spaces such as tunnels, subways, mines, underground utility tunnels, and underground complexes continues to expand, and application scenarios are constantly expanding. Various scenarios, including safety management, personnel navigation, equipment monitoring, and emergency rescue in underground spaces, all place urgent demands on positioning technology. In underground mining, real-time positioning of workers and mining equipment is a core prerequisite for ensuring production safety and improving operational efficiency. During subway and tunnel construction and operation, the positioning accuracy of construction personnel and maintenance equipment directly affects construction safety and operational stability. In underground utility tunnel maintenance, accurate positioning of inspection personnel and pipeline equipment enables rapid troubleshooting of pipeline faults and improves maintenance efficiency. However, conventional satellite navigation systems rely on space-based satellite signal transmission, which is easily blocked by underground enclosed structures, rock layers, walls, etc., and cannot penetrate the complex underground medium to reach the interior of underground spaces. This makes underground spaces a "blind spot" for satellite navigation and positioning. Conventional satellite navigation technology cannot meet the positioning needs of underground spaces. Against this background, pseudo-satellite positioning technology, as a ground-based positioning technology that simulates satellite navigation signals, has become a core technical path to solve the positioning problem in underground spaces due to its advantages of being able to be deployed autonomously, having controllable signal coverage, and not being affected by obstruction. It has been widely used in the research and practice of various underground positioning scenarios.

[0003] Although pseudosatellite positioning technology provides a feasible solution for positioning in underground spaces, existing pseudosatellite positioning systems still suffer from numerous insurmountable technical defects in practical applications in complex underground environments. These defects result in positioning accuracy, stability, and versatility failing to meet actual application requirements. Specifically: Weak anti-interference capability: Traditional pseudosatellite positioning systems often use single-frequency signals for positioning. However, the complex internal structure of underground spaces, with walls, rock layers, pipes, and other obstacles easily generating multipath reflections, creates strong multipath interference. Single-frequency signals struggle to distinguish between direct and reflected signals, easily leading to positioning drift and excessive errors, severely impacting positioning reliability. Poor terminal compatibility: Some pseudosatellite systems use custom signal formats that are incompatible with ordinary commercial GNSS receivers, requiring hardware modifications or replacement with dedicated terminals, significantly increasing application costs and limiting large-scale deployment. Insufficient clock synchronization accuracy: Clock synchronization is a core prerequisite for pseudosatellite positioning systems. Existing pseudosatellite systems often employ internal self-synchronization, lacking a unified external high-precision time reference, making them susceptible to changes in underground environmental temperature and electromagnetic interference. Interference and other factors can easily cause clock shifts, leading to significant synchronization deviations in signals transmitted by different pseudosatellites and further exacerbating positioning errors. Uneven signal coverage is also a concern, as the varying medium distribution and structure across different areas of underground space result in significant differences in signal attenuation characteristics. Traditional pseudosatellite systems use fixed signal radiation methods and are not designed to adapt to these attenuation differences, leading to situations where some areas have excessively strong signals while others have weak or no signals, failing to achieve uniform coverage across the entire underground space. Furthermore, the application of dual-frequency signals is often inappropriate. Some pseudosatellite systems attempting to use dual-frequency signals have not clearly defined their technical purpose, simply superimposing them without leveraging the advantages of the absence of ionospheric interference in underground space. This not only increases system complexity and cost but also fails to effectively improve positioning performance, resulting in significant technical redundancy. Finally, insufficient positioning accuracy is another issue. Existing systems have simplistic pseudorange data preprocessing procedures that are not optimized for the susceptibility of pseudorange data to interference and anomalies in underground space. Moreover, the calculation process does not fully utilize the coordinate advantages of the pseudosatellites themselves, leading to insufficient accuracy and stability in the calculation results.

[0004] To address the shortcomings of existing pseudosatellite positioning systems, the industry has made numerous attempts at improvement. For example, some solutions have tried to optimize the anti-interference algorithm for single-frequency signals, but these still cannot fundamentally solve the impact of multipath interference on positioning accuracy. Some solutions have attempted to improve compatibility by using dedicated terminals, but the application cost remains too high. Some solutions have tried to optimize the internal clock calibration mechanism, but without introducing an external unified high-precision time reference, the clock synchronization accuracy still cannot meet the requirements of high-precision positioning. Other solutions have tried to adjust the signal radiation power, but without considering the attenuation characteristics of underground spaces for zoned adaptation, they cannot achieve uniform coverage across the entire area. These improvements have failed to comprehensively solve the core defects of existing technologies, cannot simultaneously meet the requirements of positioning accuracy, stability, versatility, and cost control, and are difficult to adapt to the complex application scenarios of various underground spaces. Therefore, there is a need for a pseudosatellite dual-frequency positioning system that can adapt to the complex environment of underground spaces, effectively suppress multipath interference, has high clock synchronization accuracy, good terminal compatibility, uniform signal coverage, and can reasonably utilize the advantages of dual-frequency signals, providing reliable positioning accuracy. This system would comprehensively solve the positioning problems in underground spaces, promote the upgrading of underground space positioning technology, and meet the actual positioning needs of various underground scenarios. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides an underground space pseudo-satellite dual-frequency positioning system.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] An underground space pseudo-satellite dual-frequency positioning system includes: a dual-frequency signal unit, a dual-point coordination unit, a clock calibration unit, and a positioning calculation unit;

[0008] The dual-frequency signal unit generates a basic navigation signal based on the same satellite navigation system signal format, splits it into two types of frequency signals, and performs encoding initialization processing. These two types of frequency signals are then connected to the encoding link, synchronously generating encoding sequences, performing encoding timing calibration, and checking encoding consistency to generate a homogeneous dual-frequency encoded signal. This homogeneous dual-frequency encoded signal is an intermediate signal generated by the dual-frequency signal unit in the system. First, a basic navigation signal compatible with the target satellite navigation system (such as BeiDou or GPS) format is generated. Then, this signal is split into two types of frequency signals with different technical applications (one focusing on multipath interference resistance, and the other focusing on frequency division multiple access transmission). After unified encoding initialization configuration, these two types of frequency signals are connected to the same encoding link, synchronously generating encoding sequences and performing timing calibration. Finally, encoding consistency verification ensures that the two types of signals are homogeneous and synchronized. This signal is the basis for subsequent processing.

[0009] The dual-point collaborative unit performs noise reduction and multipath suppression processing on the homogeneous dual-frequency coded signal. Based on the differences in signal transmission attenuation characteristics in the underground space, it divides the transmission area and generates a feed power reference for the homogeneous dual-frequency coded signal. After dynamically adapting and adjusting the feed power of the homogeneous dual-frequency coded signal, it calibrates the branched feed channels and then performs branched feeds, transmitting the signal through a radiating component to generate a dual-frequency split-radiation navigation signal. The dual-frequency split-radiation navigation signal is the signal processed and ultimately transmitted by the dual-point collaborative unit. Noise reduction and multipath suppression processing of the homogeneous dual-frequency coded signal improves signal purity. Then, the system divides the transmission area based on the signal attenuation characteristics and multipath interference intensity of different areas in the underground space and generates a feed power reference for each area. Next, the feed power of the signal is dynamically adapted and adjusted based on actual monitoring data, and the branched feed channels are calibrated. Finally, the processed signal is transmitted through a radiating component (such as a leaky cable or directional antenna) to form a navigation signal that can be used for positioning, namely the dual-frequency split-radiation navigation signal.

[0010] The clock calibration unit initiates clock reference initialization and synchronizes with an external time reference. Based on the clock data of the external time reference, the co-source dual-frequency coded signal, and the dual-frequency radiating navigation signal, it calculates clock deviation data. Based on the clock deviation data, it dynamically adjusts calibration parameters, calculates the calibrated deviation value, compares the deviation value with preset synchronization requirements, and generates a clock synchronization navigation signal. The clock synchronization navigation signal is a time-synchronized signal output by the clock calibration unit. The system initiates clock reference initialization and synchronizes with an external unified high-precision time reference (such as BeiDou time synchronization or an atomic clock). Then, it collects clock data from the external reference, the co-source dual-frequency coded signal, and the dual-frequency radiating navigation signal in real time, and calculates clock deviation data. Based on this deviation data, it dynamically adjusts calibration parameters and calculates the residual deviation after calibration, comparing it with preset synchronization requirements. When the deviation meets the requirements, the final generated signal is the clock synchronization navigation signal. This signal ensures that the signals emitted by all pseudo-satellites in the entire system are strictly synchronized in time, which is a prerequisite for high-precision positioning calculations.

[0011] The positioning and calculation unit performs noise reduction, jitter reduction, and anti-multipath filtering on the clock synchronization navigation signal, extracts multiple pseudorange observations and performs pseudorange difference preprocessing, and then connects the pseudorange difference data to the calculation link after regularizing and sorting it. Combined with the pseudosatellite's own ground coordinates, it performs position calculation operations to generate underground space positioning and calculation signals.

[0012] Specifically, the process of generating the basic navigation signal includes: designing pseudo-satellite signal compatibility based on the signal format specifications of the target satellite navigation system, generating navigation messages, initiating the basic navigation signal generation operation step by step, generating the baseband signal corresponding to the navigation message, and then modulating the baseband signal to generate the basic navigation signal.

[0013] Specifically, the encoding initialization process includes: generating the frequency range, frequency stability, and signal amplitude differences of the two types of frequency signals based on their frequency characteristics; setting a unified encoding initialization benchmark in conjunction with the encoding specifications of the target satellite navigation system and the pseudo-satellite positioning requirements; configuring encoding parameters for the two types of frequency signals respectively; adjusting the encoding parameters; and initializing the starting benchmark, timing benchmark, encoding length, and encoding rate of the encoding sequence.

[0014] Specifically, the specific process of generating the encoded sequence includes: first, preprocessing the two types of frequency signals after encoding initialization to filter out spurious interference, and adding anti-multipath preprocessing for the anti-multipath frequency signals; connecting the two types of frequency signals after preprocessing to the same encoding link, and generating encoding sequence generation parameters based on preset encoding rules and compatibility requirements of the target satellite navigation system; starting the encoding sequence generation operation for the two types of frequency signals, acquiring the encoding timing data of the two types of frequency signals, recording the generation nodes and timing information of the encoding sequence, comparing and analyzing the encoding timing differences of the two types of signals, and identifying timing deviation nodes and the degree of deviation; for deviation nodes, timing correction of the deviation signal according to the preset timing synchronization standard.

[0015] Specifically, the coding consistency verification process includes: based on the coding sequence, coding parameters and timing feature data after coding of the two types of frequency signals, and combined with the technical uses of the two types of frequency signals, a consistency judgment standard is preset; the coding sequences of the two types of frequency signals are compared one by one according to the judgment standard to verify the timing synchronization; inconsistent coding segments are marked, and the coding operation is restarted in combination with the differences in the uses of the two types of frequency signals.

[0016] Specifically, the noise reduction and anti-multipath processing process includes: capturing spurious interference signals and multipath interference signals in the same-source dual-frequency coded signal, performing layered processing on the same-source dual-frequency coded signal, initiating a large-amplitude spurious interference filtering operation to filter out spurious interference components, initiating a multipath interference suppression operation to specifically suppress multipath interference signals, and initiating a small-amplitude spurious interference filtering operation to filter out residual spurious signals and signal noise.

[0017] Specifically, the process of generating the feed power reference includes: based on the differences in signal transmission attenuation characteristics and multipath interference intensity in different underground areas, and combined with the structural distribution of underground space, areas whose signal transmission attenuation characteristics and multipath interference intensity differences meet a preset threshold are divided into the same signal transmission area; for each transmission area, based on the attenuation degree, attenuation law and multipath interference intensity, and combined with the transmission requirements, signal coverage requirements and the differences in the uses of the same source dual-frequency coded signal, the feed power reference for the corresponding area is generated.

[0018] Specifically, the process of dynamically adapting and adjusting the feed power of the co-source dual-frequency coded signal includes: acquiring the actual transmission power data, signal coverage data, and multipath interference suppression effect data of the co-source dual-frequency coded signal in the transmission area, comparing them with the preset feed power benchmark of the corresponding area, and generating the step size, adjustment frequency, and adjustment direction of the power adjustment based on the degree of deviation and the cause of deviation.

[0019] Specifically, the clock reference initialization process includes: initiating the clock reference initialization operation based on an external time reference, synchronizing and calibrating the system clock reference with the external time reference, collecting the operating data of the system clock reference and the external time reference through the clock reference monitoring link, and completing the clock reference initialization.

[0020] Specifically, the process of calculating clock deviation data includes: acquiring real-time clock data of an external time reference, a dual-frequency coded signal from the same source, and a dual-frequency radiating navigation signal; generating clock phase and frequency characteristics of the two types of signals, the dual-frequency coded signal from the same source and the dual-frequency radiating navigation signal; comparing them with the external time reference and eliminating abnormal and invalid data; using the external time reference as a reference, recording the clock nodes of the two types of signals; calculating the clock difference between the two types of signals and the external reference, and the clock difference between the two types of signals, respectively, to generate an initial set of clock difference values; filtering the initial set of difference values, eliminating instantaneous abnormal and abrupt difference values, statistically analyzing the effective difference values, and generating clock deviation data for the two types of signals.

[0021] Specifically, the noise reduction, jitter reduction, and anti-multipath filtering processes include: activating the signal monitoring link to acquire spurious interference, instantaneous jitter, and residual multipath interference signals, and generating interference and jitter characteristics; combining the targeted processing rules preset for the two types of frequency signals, initiating a filtering operation on the clock synchronization navigation signal to filter out spurious interference components; activating the jitter suppression link to suppress instantaneous jitter and stabilize the amplitude and timing of the signal; and activating anti-multipath filtering to filter out residual multipath interference signals.

[0022] Specifically, the location calculation operation includes: extracting multiple pseudorange observations from the clock-synchronized navigation signal; identifying and removing abnormal pseudorange data by comparing with a preset pseudorange difference preprocessing standard; marking missing pseudorange data nodes; supplementing the missing pseudorange data; normalizing all pseudorange data and synchronizing it with the pseudosatellite's own ground coordinates to access the calculation link; performing the location calculation operation using the least squares method; calculating the three-dimensional position of the underground space and the receiver clock error; completing the positioning calculation operation; and generating the underground space positioning calculation signal.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention is adapted to the enclosed environment of underground spaces, overcoming the limitation of conventional satellite navigation signals in penetrating underground structures, and achieving full-area positioning in underground spaces, meeting the positioning needs of various underground spaces such as tunnels, subways, and mines. The rational application of dual-frequency signals clarifies the technical uses of the two frequency points, improving the system's resistance to multipath interference and the stability of signal transmission. Simultaneously, frequency division multiple access (FDMA) optimizes signal transmission efficiency, avoiding the weakness of single-frequency signals in resisting interference. Compared to traditional single-frequency pseudo-satellite positioning systems, positioning accuracy is improved.

[0025] The dual-frequency signal unit adopts a satellite navigation system signal format compatible design, eliminating the need for hardware modifications to ordinary commercial GNSS receivers, reducing system application costs, improving system versatility and scalability, and facilitating large-scale engineering applications. The clock calibration unit connects to an external unified high-precision time reference, solving the core problem of insufficient clock synchronization accuracy in existing pseudo-satellite systems. Through synchronization with the external time reference and closed-loop calibration, it ensures clock synchronization for various navigation signals, reducing the impact of clock deviations on positioning accuracy and improving positioning stability. The dual-point coordination unit divides the transmission area based on the signal transmission attenuation characteristics and multipath interference intensity in underground space, dynamically adjusting the feed power to achieve precise signal coverage. Simultaneously, through noise reduction, anti-multipath processing, and channel calibration, it suppresses multipath interference and stray interference in underground space, ensuring signal purity and providing reliable assurance for subsequent positioning calculations. The positioning calculation unit optimizes the positioning calculation process by combining pseudorange difference preprocessing, least squares calculation, and the pseudo-satellite's own ground coordinates. This effectively removes abnormal data, supplements missing data, and improves calculation accuracy. It also calculates the user's three-dimensional position and receiver clock error, further ensuring the accuracy and reliability of the positioning results. Attached Figure Description

[0026] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0027] Figure 1 This is a system architecture diagram of a pseudo-satellite dual-frequency positioning system for underground space according to the present invention;

[0028] Figure 2 This is the timing diagram for global clock synchronization in this invention;

[0029] Figure 3 This is a data flow diagram for the positioning calculation in this invention. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0031] Please see Figures 1-3A pseudo-satellite dual-frequency positioning system for underground space includes: a dual-frequency signal unit, a dual-point coordination unit, a clock calibration unit, and a positioning calculation unit;

[0032] The dual-frequency signal unit generates a basic navigation signal based on the same satellite navigation system signal format, splits it into two types of frequency signals, and performs encoding initialization processing; the two types of frequency signals are connected to the encoding link, and the encoding sequence generation, encoding timing calibration and encoding consistency verification are completed synchronously to generate a co-source dual-frequency encoded signal;

[0033] The dual-point collaborative unit performs noise reduction and anti-multipath processing on the co-source dual-frequency coded signal, divides the transmission area based on the difference in signal transmission attenuation characteristics in underground space, and generates a feed power reference for the co-source dual-frequency coded signal; after dynamically adapting and adjusting the feed power of the co-source dual-frequency coded signal, the split feed channel is calibrated and then split-feeded and transmitted through the radiation component to generate a dual-frequency split-radiation navigation signal;

[0034] The clock calibration unit initiates clock reference initialization and synchronizes with an external time reference. Based on the clock data of the external time reference, the same-source dual-frequency coded signal, and the dual-frequency split-radius navigation signal, it calculates clock deviation data. Based on the clock deviation data, it dynamically adjusts calibration parameters, calculates the calibrated deviation value, compares the deviation value with the preset synchronization requirements, and generates a clock synchronization navigation signal.

[0035] The positioning and calculation unit performs noise reduction, jitter reduction, and anti-multipath filtering on the clock synchronization navigation signal, extracts multiple pseudorange observations and performs pseudorange difference preprocessing, and then connects the pseudorange difference data to the calculation link after regularizing and sorting it. Combined with the pseudosatellite's own ground coordinates, it performs position calculation operations to generate underground space positioning and calculation signals.

[0036] Specifically, the process of generating the basic navigation signal includes: first, clarifying the signal format specifications of the target satellite navigation system, including encoding methods, navigation message structure, signal modulation methods, and timing requirements; then, designing pseudo-satellite signal compatibility based on these specifications to ensure that the generated navigation signal can be recognized by ordinary commercial GNSS receivers; subsequently, autonomously generating a navigation message, which includes the pseudo-satellite's precisely measured ground coordinates, system operating parameters, and purpose identifiers for the two types of frequency signals, ensuring that the message format is compatible with the target satellite navigation system and that the information is complete; and finally, based on the compatibility design and the navigation message, starting the basic navigation signal generation process step by step. The navigation signal generation process begins by generating the baseband signal corresponding to the navigation message, then modulating the baseband signal to generate the basic navigation signal. After generating the basic navigation signal, its signal format, encoding method, navigation message content, and modulation parameters are verified one by one. The compatibility with the target satellite navigation system signal format is compared one by one, incompatible parameter items are identified, and the parameters are adjusted and corrected accordingly. After the correction is completed, verification data is collected again, and the signal compatibility and message integrity are compared. The verification, correction, and re-verification steps are repeatedly executed until the basic navigation signal format is compatible and the navigation message is complete and accurate, finally generating the basic navigation signal.

[0037] Specifically, the encoding initialization process includes: capturing the frequency characteristics of two types of frequency signals, clarifying the division of labor between the two types of frequency signals (one type focuses on resisting multipath interference in underground space, and the other type focuses on frequency division multiple access transmission), analyzing the frequency range, frequency stability, and signal amplitude differences of the two types of frequency signals, setting a unified encoding initialization benchmark based on the encoding specifications of the target satellite navigation system and the pseudo-satellite positioning requirements, and clarifying the configuration range and timing benchmark requirements of the encoding parameters; configuring the encoding parameters for the two types of frequency signals respectively, adjusting the encoding parameters according to their respective technical applications, and initializing the encoding one by one. The sequence's starting reference, timing reference, coding length, and coding rate are set to ensure that the coding parameter configuration directions for the two types of frequency signals are consistent and suitable for their respective uses. After configuration, the initialized coding parameters are fully verified, and problems such as inconsistent coding references, parameter configurations exceeding the preset range, timing reference deviations, and parameter mismatches with the intended use are checked one by one. For each problem found, the coding parameters are adjusted and corrected. After adjustment, the parameter consistency, timing uniformity, and suitability for the intended use are verified again until the coding initialization parameters for the two types of frequency signals are unified, the references are consistent, and the parameters are suitable for their respective technical uses, thus completing the coding initialization process.

[0038] Specifically, the process of generating the encoded sequence includes: preprocessing the two types of frequency signals after encoding initialization to filter out small-amplitude spurious interference mixed in the signals; adding additional anti-multipath preprocessing for the frequency signals that focus on anti-multipath to ensure that the signal purity and anti-interference capability meet the encoding requirements; then synchronously connecting the two types of frequency signals after preprocessing to the same encoding link; setting unified encoding sequence generation parameters based on preset encoding rules and compatibility requirements of the target satellite navigation system; clarifying the generation rhythm and timing synchronization standard of the encoding sequence; and adjusting the encoding sequence generation details according to the differences in the uses of the two types of frequency signals. The process involves: synchronously initiating the encoding sequence generation operation for two types of frequency signals, capturing the encoding timing data of the two types of frequency signals in real time, recording the generation nodes and timing information of the encoding sequence one by one, comparing and analyzing the encoding timing differences between the two types of signals, accurately identifying timing deviation nodes and the degree of deviation; for the identified deviation nodes, timing correction of the deviation signals is performed according to the timing synchronization standard, and the encoding rhythm of the two types of signals is adjusted synchronously to avoid new timing deviations caused by correcting a single signal, while also taking into account the application compatibility of the two types of frequency signals; after correction, the encoding timing is continuously monitored, and the encoding progress and timing consistency of the two types of signals are compared in real time.

[0039] Specifically, the coding consistency verification process includes: extracting the complete coding sequences, coding parameters, and timing feature data of the two types of frequency signals after coding; clarifying the core verification points of coding consistency; and setting a unified consistency judgment standard covering coding sequences, coding parameters, timing features, and application adaptability, based on the technical applications of the two types of frequency signals. Then, the coding sequences of the two types of signals are compared one by one according to the judgment standard, and differences in sequence segments are checked segment by segment. The coding parameters of the two types of signals are compared to confirm that the parameter configurations are completely consistent and adapted to their respective applications. The timing features of the two types of signals are analyzed to verify timing synchronization. After identifying inconsistent coding segments, parameter deviations, timing deviations, and insufficient application adaptability, inconsistent coding segments are marked. The coding operation of the segment is restarted based on the application differences of the two types of frequency signals, and the deviation parameters, timing deviations, and application adaptability issues are corrected in a targeted manner. After recoding and correction, a comprehensive consistency verification is performed on the two types of signals again. The steps of comparison, marking, correction, and verification are repeated until the coding sequences, coding parameters, and timing features of the two types of frequency signals are consistent, thus completing the coding consistency verification.

[0040] Specifically, the noise reduction and multipath suppression process includes: interfacing with co-source dual-frequency coded signals, clarifying the differences in application between the two types of frequency signals, capturing spurious interference signals and multipath interference signals in the signals in real time, analyzing the sources, characteristics, and amplitude ranges of spurious interference and multipath interference, summarizing the signal characteristics of different types of interference, distinguishing between large-amplitude spurious interference and small-amplitude spurious interference, and focusing on analyzing the propagation path and timing characteristics of multipath interference; based on the interference characteristics and the applications of the two types of frequency signals, setting targeted noise reduction and multipath suppression rules, clarifying the filtering methods for different types of spurious interference, the suppression methods for multipath interference, and parameter settings, and applying enhanced multipath suppression processing to frequency signals that emphasize multipath suppression. The process involves layering the co-source dual-frequency coded signals, initiating a large-amplitude spurious interference filtering operation to remove large-amplitude spurious interference components according to preset rules, followed by a multipath interference suppression operation to specifically suppress multipath interference signals, and finally a small-amplitude spurious interference filtering operation to remove residual small-amplitude spurious signals and signal noise. During processing, signal changes are monitored in real time to ensure that the effective components of the co-source dual-frequency coded signals are not damaged, while also considering the applicability of the two types of frequency signals. Signal characteristic data is continuously collected, and the signal purity and anti-interference capability before and after processing are compared until there is no obvious spurious interference or multipath interference in the signal, and the signal purity meets the requirements for subsequent processing, thus completing noise reduction and anti-multipath processing.

[0041] Specifically, the process of generating the feed power reference includes: conducting zoned detection of the underground space, deploying detection nodes at different locations and areas within the underground space, collecting signal transmission attenuation data and multipath interference intensity data from each detection node, and recording the attenuation degree, attenuation pattern, and multipath interference distribution characteristics at each location; analyzing the data from all detection nodes, identifying differences in signal transmission attenuation characteristics and multipath interference intensity in different areas, and, based on the structural distribution of the underground space, dividing areas with similar attenuation characteristics and multipath interference intensity into the same signal transmission area, thus defining the boundary range of each transmission area; and analyzing the attenuation degree, attenuation pattern, and multipath interference in each transmission area. In terms of strength, considering the transmission requirements, signal coverage requirements, and differences in the uses of the two types of frequency signals, a preliminary feed power reference is set for the corresponding region. For frequency signals that emphasize multipath resistance, the feed power reference for the corresponding region is appropriately increased to enhance its multipath resistance capability. The rationality of the power reference for each region is verified, and the compatibility of the power reference with the region's attenuation characteristics and multipath interference intensity is analyzed. It is determined whether the power reference can meet the requirements of signal coverage, transmission stability, and multipath resistance. Unreasonable power references are adjusted and corrected until the power reference for each region can adapt to the environmental characteristics of the corresponding region and the uses of the two types of frequency signals, thus completing the generation of the feed power reference.

[0042] Specifically, the process of dynamically adapting and adjusting the feed power of the dual-frequency coded signal includes: deploying power monitoring nodes and multipath interference monitoring nodes in each signal transmission area; collecting real-time data on the actual transmission power, signal coverage, and multipath interference suppression effect of the dual-frequency coded signal in each transmission area; recording the power changes and interference suppression effect changes in each area; comparing the collected actual transmission power with the preset feed power benchmark for the corresponding area one by one; combining the signal coverage effect and multipath interference suppression effect to identify the power deviation; analyzing the cause of the deviation; distinguishing whether the deviation is caused by changes in regional attenuation characteristics, changes in multipath interference intensity, or deviation during power transmission; and adjusting the power based on the degree of deviation and the deviation... Based on the reasons and the differences in the uses of the two types of frequency signals, a dynamic adjustment scheme was set up, clarifying the step size, adjustment frequency, and adjustment direction of power adjustment. For frequency signals that focus on multipath suppression, the power parameters were adjusted first to ensure their interference suppression effect. After the adjustment was completed, the actual transmission power, signal coverage, and interference suppression effect data of each area were collected again, and compared and verified with the power reference, coverage requirements, and interference suppression requirements to determine whether the deviation was eliminated and whether each indicator met the standards. If the standards were not met, the adjustment scheme was optimized, and the steps of collection, comparison, analysis, adjustment, and verification were repeatedly executed until the actual transmission power of each area matched the power reference of the corresponding area, the signal coverage was complete, and the multipath interference suppression effect met the standards, thus completing the dynamic power adaptation adjustment.

[0043] Specifically, the clock reference initialization process includes: accessing an external unified high-precision time reference, which is either a BeiDou time reference or an atomic clock reference, ensuring that all pseudosatellite systems access the same time reference and addressing the core requirement of pseudosatellite clock synchronization; setting a unified clock reference standard for the system based on the navigation and positioning accuracy requirements of the entire positioning system, clarifying the accuracy requirements, stability requirements, and timing start standard of the clock reference, ensuring synchronization with the external unified time reference; initiating the clock reference initialization operation, configuring the core parameters of the clock reference, including clock frequency, timing start point, calibration accuracy, etc., and synchronizing and calibrating the system clock reference with the external unified high-precision time reference to ensure clock reference synchronization. The starting point and frequency are completely consistent with the external time reference. After initialization, a comprehensive accuracy verification of the clock reference is performed, the clock reference monitoring link is started, and the operating data of the system clock reference and the external time reference are continuously collected to investigate problems such as clock reference offset, parameter configuration deviation, unstable operation, and asynchrony with the external time reference. The causes of the problems found are analyzed one by one, the clock reference parameters are adjusted and corrected in a targeted manner, and the clock reference is re-synchronized and calibrated with the external time reference. After adjustment, the accuracy verification is started again, and the stability, accuracy, and synchronization with the external time reference are continuously monitored until the clock reference is accurate, stable, fully meets the preset standards, and is synchronized with the external unified time reference, thus completing the clock reference initialization.

[0044] Specifically, the process for calculating clock deviation data includes: activating the clock data synchronization acquisition link to synchronously acquire real-time clock data from an external unified high-precision time reference, real-time clock data from a dual-frequency coded signal originating from the same source, and real-time clock data from a dual-frequency radiating navigation signal; clarifying the acquisition frequency and acquisition nodes for the three types of clock data to ensure the synchronous and complete acquisition of data; preprocessing the acquired three types of clock data, analyzing the clock phase and clock frequency characteristics of the dual-frequency coded signal originating from the same source and the dual-frequency radiating navigation signal; performing a preliminary comparison between the clock data of the two types of signals and the clock data from the external unified time reference, and eliminating abnormal and invalid data generated during the acquisition process; based on the preprocessed valid clock data, using the external unified time reference as... Based on the reference standard, the clock nodes of the co-source dual-frequency coded signal and the dual-frequency split-radius navigation signal are recorded one by one. The clock difference between the two types of signals and the external time reference is calculated separately, and the clock difference between the two types of signals is also calculated to form an initial clock difference set. The initial clock difference set is then filtered to remove instantaneous abnormal differences and abrupt differences, retaining valid clock differences that conform to normal variation patterns. The valid clock differences are statistically verified to analyze the variation pattern and range of clock deviations, clarify the stability of the deviations and the links that cause the deviations, and distinguish whether the deviations are caused by the signal generation or transmission links. Finally, the clock deviation data of the two types of signals are determined to provide a basis for subsequent calibration operations and ensure that the two types of signals are synchronized with the external unified time reference after calibration.

[0045] Specifically, the noise reduction, jitter removal, and anti-multipath filtering processes include: aligning with the clock synchronization navigation signal, clarifying the differences in application between the two types of frequency signals, activating the signal monitoring link, capturing spurious interference components, instantaneous jitter signals, and residual multipath interference signals in the signal in real time, analyzing the characteristics of spurious interference, instantaneous jitter, and multipath interference, distinguishing different types of interference and jitter, and focusing on analyzing the timing characteristics of residual multipath interference; based on the interference and jitter characteristics, and combined with the differences in application between the two types of frequency signals, setting targeted noise reduction, jitter removal, and anti-multipath filtering rules, clarifying the noise reduction filtering method, jitter removal suppression parameters, and multipath filtering parameter settings, and adopting enhanced multipath filtering rules for frequency signals that emphasize anti-multipath filtering; first, the clock... The synchronous navigation signal undergoes noise reduction processing. A filtering operation is initiated according to preset rules to specifically remove stray interference components from the signal. After noise reduction, the denoised signal is then subjected to jitter suppression processing. A jitter suppression link is activated to suppress instantaneous jitter and stabilize the signal amplitude and timing. After jitter suppression, an anti-multipath filtering operation is initiated to specifically remove residual multipath interference signals and enhance the effective signal components. Throughout the processing, signal stability, purity, and anti-interference capability are continuously monitored. Signal amplitude and timing data are collected, and the differences between the signal before and after processing are compared until the signal is stable, free of stray interference, instantaneous jitter, and multipath interference. The signal purity and stability meet the requirements for subsequent pseudorange extraction and calculation, thus completing the noise reduction, jitter suppression, and anti-multipath filtering processing.

[0046] Specifically, the location calculation operation includes: extracting multiple pseudorange observations from the processed clock synchronization navigation signal; sorting out the acquisition nodes and data formats of the pseudorange observations to ensure that the number of extracted pseudorange observations meets the positioning calculation requirements and that the data is complete and without missing data. The pseudorange observations include at least four sets, used to calculate the user's three-dimensional position and clock difference; setting pseudorange difference preprocessing standards based on the positioning calculation accuracy requirements, clarifying the effective range, allowable deviation range, and data integrity and consistency requirements of the pseudorange data; screening the extracted pseudorange observations one by one, identifying and removing abnormal pseudorange data that exceeds the effective range or the allowable deviation range according to the preprocessing standards, and marking missing pseudorange data nodes; and further processing the pseudorange data. Missing pseudorange data is supplemented appropriately. Combining the variation patterns of surrounding effective pseudorange data and the pseudosatellite's own ground coordinates, an appropriate supplementation method is used to fill in the missing data, ensuring data continuity and consistency. After supplementation, the distribution patterns of pseudorange data are analyzed, all pseudorange data are normalized, minor deviations in the data are eliminated, and the data format is adjusted. The normalized pseudorange difference data and the pseudosatellite's own precise ground coordinates are synchronously connected to the calculation link. The least squares method is used to perform position calculation operations, simultaneously calculating the user's three-dimensional position in underground space and receiver clock error. After the calculation is completed, the accuracy of the calculation results is verified to ensure that the calculation results meet the preset accuracy requirements, thus completing the pseudorange difference preprocessing and positioning calculation related operations.

[0047] This embodiment is based on an underground space pseudo-satellite dual-frequency positioning system (including dual-frequency signal unit, dual-point coordination unit, clock calibration unit, and positioning calculation unit), combined with a leaky cable deployment mode (suitable for long-distance linear underground space) and a dual-antenna beam-through deployment mode (suitable for medium and short-distance underground space).

[0048] I. System Deployment (Two Modes, Sharing Core Unit)

[0049] The core unit composition and working logic of the two deployment modes are completely identical. Only the radiation components and signal transmission adaptation parameters of the dual-point collaborative unit are adjusted, as follows:

[0050] (a) Leaky cable deployment mode (suitable for long-distance linear scenarios such as tunnels and underground utility tunnels)

[0051] A leaky cable (hereinafter referred to as "leaky cable") is laid along the direction of the target underground space. The total length of the leaky cable is set as parameter L. The outer conductor has periodic slots for uniform signal radiation. A first radiation node (end A) and a second radiation node (end B) are set at both ends of the leaky cable, and signal injection devices are deployed at both ends. Both ends A and B are connected to an external unified high-precision time reference (denoted as T0, which can be selected from Beidou time service or atomic clock reference) to ensure signal clock synchronization. Signal monitoring nodes are set up along the leaky cable to collect signal strength, interference parameter β and attenuation parameter α. The user terminal adopts a common commercial GNSS terminal, which can be adapted by software upgrade only, without the need for hardware modification.

[0052] Unit correspondence: The dual-frequency signal unit is integrated into the signal injection devices at ends A and B to complete the generation and encoding of dual-frequency signals; the dual-point collaborative unit consists of a leaky cable, a signal injection device, a monitoring node, and a power adjustment module, and is responsible for signal noise reduction, anti-multipath, power adaptation, and radiation; the clock calibration unit is deployed at both ends of the synchronization control module and connects to T0 to complete clock synchronization; the positioning calculation unit is integrated into the user terminal to complete signal processing and positioning calculation.

[0053] (ii) Dual-antenna beam-through deployment mode (suitable for short-to-medium distance scenarios such as underground pedestrian passages and small utility tunnels)

[0054] Directional antennas are deployed at two relatively preset locations (point A and point B) in the target space, facing each other and spaced apart by parameter L. Signal generators are deployed at points A and B and electrically connected to the corresponding antennas. Both ends are connected to a time reference T0 to ensure clock synchronization. Monitoring nodes are set up next to the antennas to collect signal strength and interference data. The user terminal is consistent with the leaky cable mode, requiring no hardware modification.

[0055] Unit correspondence: The dual-frequency signal unit is integrated into the signal generators at both ends; the dual-point collaborative unit consists of a directional antenna, a signal generator, a monitoring node, and a power adjustment module; the deployment and working logic of the clock calibration unit and the positioning calculation unit are completely consistent with the leaky cable mode.

[0056] II. Specific work process (both modes are applicable, but the radiation links differ)

[0057] (a) Dual-frequency signal unit

[0058] 1. Basic navigation signal generation: Based on the target satellite navigation system signal format compatibility design, basic navigation signals are generated, and the precise coordinates (X1,Y1,Z1) and (X2,Y2,Z2) of nodes A and B and deployment mode adaptation parameters are written into the message; two types of frequency signals f1 (focusing on anti-multipath) and f2 (focusing on frequency division multiple access) are generated.

[0059] 2. Encoding initialization and sequence generation: Set a unified encoding initialization benchmark K, configure the f1 and f2 encoding parameters, initialize the encoding sequence benchmark and timing; after preprocessing, connect to the same encoding link, generate the encoding sequence synchronously, and calibrate the timing deviation Δτ to ensure timing alignment.

[0060] 3. Encoding consistency verification and signal allocation: Compare the encoding sequences, parameters and timing of f1 and f2, mark and correct inconsistent parts until they are completely consistent, and generate dual-frequency encoded signals from the same source; A end is connected to f1 and B end is connected to f2 to ensure that the signals are from the same source and synchronized.

[0061] (ii) Two-point collaborative unit

[0062] 1. Noise Reduction and Multipath Reduction: Captures spurious and multipath interference in the signal, filters out large spurious noise in layers, suppresses multipath interference, and filters out small spurious noise to ensure signal purity.

[0063] 2. Power Reference Generation and Dynamic Adjustment: Based on the α and β parameters collected by the monitoring nodes, the transmission area is divided, and a power reference P0 (with the f1 power reference appropriately increased) is generated for each area. The actual power P is compared with P0, and the power step size ΔP1 and frequency f are adjusted according to the deviation ΔP. a This ensures uniform signal coverage.

[0064] 3. Signal radiation (points of difference):

[0065] (1) Leaky cable mode: The processed signal is injected into the leaky cable at both ends. The signal propagation speed is v (proportional coefficient k=v / c, c is the speed of light). It is uniformly radiated through the slot to form a dual-frequency split-radiation navigation signal.

[0066] (2) Dual antenna mode: signals are transmitted through directional antennas at both ends, and the propagation speed is equal to c (k=1). The power is adjusted to make the signal strength in the coverage area equal. Beamforming is used to suppress multipath and form a coverage signal.

[0067] (iii) Clock calibration unit

[0068] 1. Clock reference initialization: Connect to T0, configure clock parameters, calibrate the system clocks T1 and T2 at both ends, and ensure that the clock deviations ΔT1 and ΔT2 are less than the preset threshold T. max .

[0069] 2. Clock Deviation Calculation: Synchronously acquire T0 and clock data T from both ends of the signal. 11 T 22 Remove outlier data and calculate ΔT 10 =T 11 -T0, ΔT 20 =T 22 -T0, ΔT 12 =T 11 -T 22 After filtering, the clock deviation data ΔT is obtained.

[0070] 3. Synchronous calibration: Adjust the calibration parameters according to ΔT, calculate the post-calibration deviation ΔT′, if ΔT′≤T max Generate a clock synchronization navigation signal; otherwise, repeat the calibration until the target is met.

[0071] (iv) Location Solving Unit

[0072] Integrated into the user terminal, it completes signal preprocessing, pseudorange extraction, pseudorange difference preprocessing, and position calculation. The calculation logic is consistent in both modes, with only the propagation speed parameter being different.

[0073] III. Location Solution

[0074] (I) Calculation premises and parameter definitions

[0075] 1. Given fixed parameters: node spacing L; coordinates of nodes A and B (X1, Y1, Z1) and (X2, Y2, Z2); time base T0; synchronization threshold T. max Speed ​​of light c; Leaky cable mode with additional known v and k = v / c; Dual antenna mode with k = 1; Pseudorange deviation allowable range Δρ max ; Solution accuracy threshold Δd max .

[0076] 2. Measurement parameters: Pseudorange observations ρ1 (from user to point A), ρ2 (from user to point B); Clock deviation ΔT (ΔT≤T) max (This can be ignored).

[0077] 3. Parameters to be solved: User coordinates (X,Y,Z); actual distances d1 (from user to end A / point A), d2 (from user to end B / point B); pseudorange difference Δρ; scaling factor λ.

[0078] 4. Geometric relationship: The user is located along the line connecting the two nodes, d1+d2=L.

[0079] (II) Step 1: Pseudo-distance difference preprocessing and calculation

[0080] 1. Pseudorange preprocessing: Filter ρ1 and ρ2, and discard those exceeding Δρ. max Abnormal data is filled in, missing data is filled in, and after normalization, effective pseudo-distances ρ1′ and ρ2′ are obtained.

[0081] 2. Calculation of pseudo-distance difference: Δρ=ρ1′-ρ2′ (ignore the influence of ΔT).

[0082] 3. Correction of pseudorange versus actual distance correlation:

[0083] (1) Leaky cable mode: ρ1′=(d1×c) / v, ρ2′=(d2×c) / v=(L-d1)×c / v; Substituting ρ1′ and ρ2′ into the pseudo-distance difference formula Δρ=ρ1′-ρ2′, we can simplify to get: Δρ=[d1×c / v-(L-d1)×c / v]=[c×(2d1-L)] / v; Combining the proportionality coefficient k=v / c, we can further simplify to get: Δρ=(2d1-L) / k, and after rearranging, we can solve for the actual distance d1: d1=(Δρ×k+L) / 2; Then, according to the geometric relationship d1+d2=L, we can get d2=L-d1=(L-Δρ×k) / 2.

[0084] (2) Dual antenna mode: Since the signal propagation speed is equal to the speed of light c, i.e. k=1, there is no speed deviation between the pseudorange and the actual distance. We can directly correlate them to get: ρ1′=d1, ρ2′=d2=L-d1; Substituting into the pseudorange difference formula Δρ=ρ1′-ρ2′, we can simplify to get: Δρ=d1-(L-d1)=2d1-L; After simplification, we can solve for the actual distance d1: d1=(Δρ+L) / 2, and similarly we can get d2=L-d1=(L-Δρ) / 2.

[0085] (III) Second step: Verification and correction of actual distance

[0086] 1. Reasonableness verification: According to the boundary constraints of the underground space, the actual distance must satisfy 0≤d1≤L and 0≤d2≤L. If the calculated d1 and d2 exceed this range, it is determined that there is missing abnormal data in the pseudorange preprocessing. Return to the first step to re-screen, supplement and normalize the pseudorange until d1 and d2 meet the constraint conditions.

[0087] 2. Interference Correction: Based on the interference parameter β collected by the monitoring node, interference compensation is performed on d1 and d2. The correction formula is d1′=d1×(1-β) and d2′=d2×(1-β), where β is the interference attenuation coefficient (0≤β<1), which is used to offset the influence of multipath interference and stray interference on the actual distance calculation and ensure the accuracy of distance data.

[0088] (iv) Step 3: User coordinate calculation

[0089] Based on the known coordinates (X1, Y1, Z1) and (X2, Y2, Z2) of nodes A and B, and the corrected actual distances d1′ and d2′, the user coordinates (X, Y, Z) are calculated using the least squares method, as follows:

[0090] 1. Establish the distance equation: The distance equation from the user to node A is √[(X-X1)]. 2 +(Y-Y1) 2 +(Z-Z1) 2 ]=d1′; The distance equation from the user to node B is √[(X-X2)] 2 +(Y-Y2) 2 +(Z-Z2) 2 ]=d2′.

[0091] 2. Linearization of equations: Perform Taylor expansion on the two distance equations respectively, ignore higher-order infinitesimal terms, and transform them into a system of linear equations; let the user's initial iteration coordinates be (X0, Y0, Z0) (the coordinates of the midpoint of the line connecting nodes A and B can be selected as the initial values, i.e., X0=(X1+X2) / 2, Y0=(Y1+Y2) / 2, Z0=(Z1+Z2) / 2), and the iteration correction is (ΔX, ΔY, ΔZ), then X=X0+ΔX, Y=Y0+ΔY, Z=Z0+ΔZ.

[0092] 3. Substitution and Expansion Simplification: Substitute X = X0 + ΔX, Y = Y0 + ΔY, and Z = Z0 + ΔZ into the distance equation, and after Taylor expansion and simplification, obtain the system of linear equations:

[0093] a1×ΔX+b1×ΔY+c1×ΔZ=l1;

[0094] a²×ΔX + b²×ΔY + c²×ΔZ = l²;

[0095] Where the coefficients are a1=(X0-X1) / d1′0, b1=(Y0-Y1) / d1′0, and c1=(Z0-Z1) / d1′0 (d1′0 is the distance from the initial coordinates to node A, d1′0=√[(X0-X1)]). 2 +(Y0-Y1) 2 +(Z0-Z1) 2 ]);

[0096] Coefficients a2=(X0-X2) / d2′0, b2=(Y0-Y2) / d2′0, c2=(Z0-Z2) / d2′0 (d2′0 is the distance from the initial coordinates to node B, d2′0=√[(X0-X2)]) 2 +(Y0-Y2) 2 +(Z0-Z2) 2 ]);

[0097] The constant terms are l1 = d1′ - d1′0 and l2 = d2′ - d2′0.

[0098] 4. Solving the system of equations: The above linear system of equations is solved by the least squares method to obtain the iterative correction amount (ΔX, ΔY, ΔZ), and the user coordinates are updated as (X1, Y1, Z1) = (X0 + ΔX, Y0 + ΔY, Z0 + ΔZ).

[0099] 5. Iterative convergence criterion: Calculate the deviation Δd between the coordinates of the current iteration and the coordinates of the previous iteration = √(ΔX). 2 +ΔY 2 +ΔZ 2 If Δd≤Δd max If the preset solution accuracy threshold is met, the iteration converges and the current coordinates become the user's final coordinates (X,Y,Z); otherwise, the current iteration coordinates are used as the new initial coordinates, and the above linearization, solution, and update steps are repeated until the iteration converges.

[0100] (v) Step 4: Verification of solution accuracy

[0101] 1. Accuracy Verification Calculation: Substitute the calculated user coordinates (X,Y,Z) into the distance equations of nodes A and B to calculate the theoretical pseudoranges ρ1″ ​​and ρ2″, i.e., ρ1″=√[(X-X1)]. 2 +(Y-Y1) 2 +(Z-Z1) 2 ]、ρ2″=√[(X-X2) 2 +(Y-Y2) 2 +(Z-Z2) 2 ]; Calculate the deviation between the theoretical pseudorange and the effective pseudorange Δρ1=|ρ1″-ρ1′|, Δρ2=|ρ2″-ρ2′|.

[0102] 2. Verification and Handling: If Δρ1≤Δρ max And Δρ2≤Δρ max If the solution result is deemed satisfactory, an underground space positioning solution signal is generated, and the user coordinates (X, Y, Z) are output. If any deviation exceeds the allowable range, the solution accuracy is deemed unsatisfactory. The process returns to the first step to re-perform pseudo-distance difference preprocessing, and then re-executes the distance calculation, coordinate solution, and accuracy verification steps until the solution result meets the preset accuracy requirements.

[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A pseudo-satellite dual-frequency positioning system for underground space, characterized in that, include: Dual-frequency signal unit, dual-point coordination unit, clock calibration unit, and positioning calculation unit; The dual-frequency signal unit generates a basic navigation signal, which is then split into two types of frequency signals: one type focuses on resisting multipath interference, and the other type focuses on frequency division multiple access transmission. After the two types of frequency signals undergo encoding initialization processing, they are connected to the encoding link, and the encoding sequence generation, encoding timing calibration, and encoding consistency verification are completed synchronously to generate a dual-frequency encoded signal from the same source. The dual-point collaborative unit performs noise reduction and anti-multipath processing on the co-source dual-frequency coded signal. Based on the differences in signal transmission attenuation characteristics and multipath interference intensity in different underground areas, and combined with the structural distribution of the underground space, areas where the differences in signal transmission attenuation characteristics and multipath interference intensity meet a preset threshold are divided into the same signal transmission area. For each transmission area, based on the attenuation degree, attenuation law, and multipath interference intensity, and combined with the transmission requirements, signal coverage requirements, and differences in the uses of the co-source dual-frequency coded signal, a corresponding feed power benchmark is generated. The feed power is dynamically adapted and adjusted to obtain the actual transmission power data, signal coverage data, and multipath interference suppression effect data of the co-source dual-frequency coded signal in the transmission area. This data is compared with the preset feed power benchmark for the corresponding area. Based on the degree of deviation and the cause of deviation, the step size, adjustment frequency, and adjustment direction of the feed power adjustment are generated. After the feed channels are calibrated, they are fed separately and transmitted through the radiating components to generate dual-frequency split-radiation navigation signals; The clock calibration unit initiates clock reference initialization and synchronizes with an external time reference, calculates clock deviation data, dynamically adjusts calibration parameters, and generates a clock synchronization navigation signal. The positioning and calculation unit performs noise reduction, jitter reduction, and anti-multipath filtering on the clock synchronization navigation signal, extracts multiple pseudorange observations and performs pseudorange difference preprocessing, and then connects the pseudorange difference data to the calculation link after regularizing and sorting it. Combined with the pseudosatellite's own ground coordinates, it performs position calculation operations to generate underground space positioning and calculation signals.

2. The system of claim 1, wherein, The specific process for generating the basic navigation signal includes: Based on the signal format specifications of the target satellite navigation system, a pseudo-satellite signal compatibility design is carried out to generate navigation messages. The basic navigation signal generation operation is initiated step by step to generate the baseband signal corresponding to the navigation message. Then, the baseband signal is modulated to generate the basic navigation signal.

3. The system of claim 1, wherein, The specific process of the encoding initialization process includes: Based on the frequency characteristics of the two types of frequency signals, the frequency range, frequency stability, and signal amplitude differences of the two types of frequency signals are generated. In combination with the coding specifications of the target satellite navigation system and the pseudo-satellite positioning requirements, a unified coding initialization benchmark is set. The coding parameters of the two types of frequency signals are configured, the coding parameters are adjusted, and the starting benchmark, timing benchmark, coding length, and coding rate of the coding sequence are initialized.

4. The system of claim 1, wherein, The specific process of generating the encoded sequence includes: First, the two types of frequency signals after encoding initialization are preprocessed to filter out spurious interference. For frequency signals resistant to multipath, anti-multipath preprocessing is added. The two types of preprocessed frequency signals are then connected to the same encoding link. Based on preset encoding rules and compatibility requirements of the target satellite navigation system, encoding sequence generation parameters are generated. The encoding sequence generation operation for the two types of frequency signals is initiated, and the encoding timing data of the two types of frequency signals is obtained. The generation nodes and timing information of the encoding sequence are recorded. The encoding timing differences between the two types of signals are compared and analyzed to identify timing deviation nodes and the degree of deviation. For deviation nodes, the timing correction of the deviation signal is performed according to the preset timing synchronization standard.

5. The system of claim 1, wherein, The specific process of the encoding consistency verification includes: Based on the encoded sequences, encoding parameters, and timing characteristic data of the two types of frequency signals, and considering the technical applications of the two types of frequency signals, a consistency judgment standard is preset; the encoded sequences of the two types of frequency signals are compared one by one according to the judgment standard to verify the timing synchronization; inconsistent encoded segments are marked, and the encoding operation is restarted based on the differences in applications of the two types of frequency signals.

6. The system of claim 1, wherein, The specific process of noise reduction and anti-multipath processing includes: Capture spurious and multipath interference signals in the same-source dual-frequency coded signal, perform layered processing on the same-source dual-frequency coded signal, initiate large-amplitude spurious interference filtering operation to filter out spurious interference components, initiate multipath interference suppression operation to specifically suppress multipath interference signals, and initiate small-amplitude spurious interference filtering operation to filter out residual spurious signals and signal noise.

7. The system of claim 1, wherein, The specific process for initializing the clock reference includes: Based on an external time reference, the clock reference initialization operation is initiated to synchronize and calibrate the system clock reference with the external time reference. Through the clock reference monitoring link, the operating data of the system clock reference and the external time reference are collected to complete the clock reference initialization.

8. The system of claim 1, wherein, The specific process for calculating the clock offset data includes: Real-time clock data of an external time reference, a dual-frequency coded signal from the same source, and a dual-frequency radiating navigation signal are acquired. The clock phase and frequency characteristics of the two types of signals are generated and compared with the external time reference to eliminate abnormal and invalid data. Using the external time reference as a reference, the clock nodes of the two types of signals are recorded, and the clock differences between the two types of signals and the external reference, as well as the clock differences between the two types of signals, are calculated to generate an initial set of clock differences. The initial set of differences is filtered to eliminate instantaneous abnormal and abrupt differences, and the effective differences are statistically analyzed to generate clock deviation data for the two types of signals.

9. The system of claim 1, wherein, The specific processes of noise reduction, jitter reduction, and anti-multipath filtering include: The signal monitoring link is activated to acquire spurious interference, instantaneous jitter, and residual multipath interference signals, generating interference and jitter characteristics. Based on the pre-set targeted processing rules for the two types of frequency signals, a filtering operation is initiated on the clock synchronization navigation signal to filter out spurious interference components. The jitter suppression link is activated to suppress instantaneous jitter and stabilize the amplitude and timing of the signal. The anti-multipath filtering operation is activated to filter out residual multipath interference signals.

10. The system of claim 1, wherein, The specific process of the location calculation operation includes: Multiple pseudorange observations are extracted from the clock-synchronized navigation signal. Abnormal pseudorange data are identified and removed by comparing with the preset pseudorange difference preprocessing standard, and missing pseudorange data nodes are marked. The missing pseudorange data is supplemented, and after normalizing all pseudorange data, it is synchronized with the pseudosatellite's own ground coordinates and connected to the solution link. The least squares method is used to perform the position solution operation, calculate the three-dimensional position of the underground space and the receiver clock difference, complete the positioning solution operation, and generate the underground space positioning solution signal.

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