Navigation signal broadcasting system based on microwave bidirectional time synchronization technology

Abstract

The invention discloses a navigation signal broadcasting system based on a microwave two-way time synchronization technology, which belongs to the field of navigation positioning communication and comprises at least four ground station units arranged in a coverage area, and each unit comprises a ground station host, a timing system receiving and transmitting antenna and a navigation signal transmitting antenna. The timing receiving and transmitting antenna establishes a bidirectional microwave link between a master station and a slave station, a ground station host realizes inter-station time synchronization and pseudo-range measurement through the link by adopting a bidirectional one-way pseudo-range measurement technology, generates a navigation message based on a synchronization result, and broadcasts the navigation message through the navigation signal transmitting antenna after modulation. And the navigation terminal in the area can still realize positioning when the satellite signal is unavailable. The ground station host adopts a modular portable design, and has high environmental adaptability. According to the invention, the problem that the terminal cannot be positioned in a satellite signal rejection environment is solved, and the independent, reliable and rapidly deployable regional navigation capability is provided.

Description

Technical Field

[0001] This invention belongs to the field of navigation, positioning and communication technology, and in particular relates to a navigation signal broadcasting system based on microwave two-way time synchronization technology. Background Technology

[0002] Global Navigation Satellite System (GNSS) is currently the most widely used navigation and positioning technology. It involves deploying multiple satellites in Earth orbit, continuously transmitting radio signals containing time information back to the ground. User receiving equipment receives signals from at least four satellites, calculates the distance to each satellite using the time difference of signal propagation, and then uses the triangulation principle to calculate its own position, velocity, and time. This technology has been successfully implemented in systems such as the US GPS, Russia's GLONASS, Europe's Galileo, and China's BeiDou. It provides continuous, real-time, and accurate positioning services for numerous fields worldwide, including engineering surveying, transportation, resource exploration, and daily navigation, offering significant advantages such as wide coverage, high positioning accuracy, and ease of use.

[0003] However, existing GNSS technology still has significant limitations in practical applications: its positioning function relies entirely on the reliable reception of satellite signals. When users are in environments where satellite signals are blocked, attenuated, or intentionally interfered with, such as indoors, underground, canyons, densely populated urban areas, or war zones affected by electromagnetic countermeasures, satellite signals may not provide effective coverage or may be denied, causing navigation terminals to lose their positioning capabilities due to insufficient satellite signal reception. Especially in high-reliability scenarios such as military applications, equipment will be unable to perform accurate navigation and positioning when satellite signals fail, severely restricting its combat effectiveness and mission execution. Therefore, existing technologies lack effective means to provide high-precision positioning services to terminals even when satellite signals are unavailable. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a navigation signal broadcasting system based on microwave two-way time synchronization technology, thereby resolving the issues present in the prior art.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a navigation signal broadcasting system based on microwave two-way time synchronization technology, comprising at least four ground station units deployed within the coverage area, wherein each ground station unit includes a master station and at least three slave stations; Each of the ground station units includes a ground station host, a timing transceiver antenna, and a navigation signal transmitting antenna; The time synchronization transceiver antenna is used to establish a two-way microwave link between the master station and the slave station. The ground station host uses the two-way microwave link to achieve inter-station time synchronization and measure inter-station pseudorange through two-way single-way pseudorange measurement technology. The ground station host is also used to generate navigation messages based on time synchronization results, and modulate the navigation messages into navigation signals and broadcast them via the navigation signal transmitting antenna so that navigation terminals in the coverage area can receive the navigation signals for positioning.

[0006] Preferably, the ground station host is a modular portable host with a split-cavity structure, which integrates a time-tracking navigation baseband module, a clock module, and a power amplifier module.

[0007] Preferably, the clock module is connected to the time-system navigation baseband module and is used to provide the time-system navigation baseband module with a reference clock signal and a second pulse signal.

[0008] Preferably, the timing navigation baseband module is configured to: multiply the reference clock signal to obtain a sampling clock, and sample the rising edge of the second pulse signal to determine the integer second of the navigation signal transmission.

[0009] Preferably, the timing navigation baseband module is connected to the power amplifier module and is used to output the modulated intermediate frequency signal and control signal to the power amplifier module. The power amplifier module amplifies the intermediate frequency signal and outputs it to the navigation signal transmitting antenna.

[0010] Preferably, the outer casing of the ground station host is made of rust-proof aluminum and is equipped with dustproof, waterproof, heat dissipation and electromagnetic shielding structures.

[0011] Preferably, the external interface of the ground station host meets the IP68 protection level requirements.

[0012] Preferably, a lightning protection device is provided at the navigation signal transmitting antenna.

[0013] Preferably, the timing navigation baseband module is further configured to control the navigation signal to perform frequency hopping at the exact second of transmission according to a pre-stored frequency hopping pattern.

[0014] Preferably, the bidirectional one-way pseudorange measurement technology is implemented in the following way: the master station and the slave station respectively transmit forward ranging signals and reverse ranging signals based on their own clocks, and measure the time delay. and The delay and They respectively satisfy the following relations: ; ; Where D is the actual distance between the master station and the slave station. Main station latency For station delay, For the speed of light, t 12 To account for the one-way propagation delay from the station, t 21 The latency of one-way propagation from the main station. There is a clock difference between the ranging signal frames sent by both parties.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: This invention constructs a satellite-independent ground navigation signal broadcasting network through a technical solution that includes "at least four ground station units deployed within the coverage area," "the ground station host uses bidirectional single-way pseudorange measurement technology via the bidirectional microwave link to achieve inter-station time synchronization and measure inter-station pseudorange," and "the navigation message is modulated into a navigation signal and broadcast via the navigation signal transmitting antenna." This system does not rely on external satellite signals and can autonomously generate and broadcast GNSS-like navigation signals in areas where satellite signals cannot cover or are interfered with, enabling navigation terminals in that area to regain high-precision positioning capabilities.

[0016] This invention achieves inter-station time synchronization through the ground station host using bidirectional single-way pseudorange measurement technology via the bidirectional microwave link. This technology effectively eliminates the effects of inter-station clock differences and equipment delays, thus achieving nanosecond-level time synchronization accuracy. Furthermore, this invention ensures the uniformity of the broadcast signal time reference across all stations, a prerequisite for accurate ranging and positioning by the terminal. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a block diagram of the ground station unit composition according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the system networking operation according to an embodiment of the present invention; Figure 3 This is a schematic diagram of bidirectional one-way pseudorange measurement according to an embodiment of the present invention; Figure 4 A timing diagram is generated for the launch time in an embodiment of the present invention; Figure 5 This is a block diagram illustrating the principle of local carrier implementation in an embodiment of the present invention. Figure 6 This is a block diagram of the ground station host product according to an embodiment of the present invention; Figure 7 This is a block diagram of the motherboard components according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the ground station host structure according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the rear panel of the ground station host according to an embodiment of the present invention. Detailed Implementation

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0020] The technical terms used in the following embodiments will be explained first.

[0021] A GNSS system consists of three parts: satellites, a ground monitoring segment, and user receiving equipment. Satellites transmit radio frequency signals in Earth orbit, and receivers receive these signals and calculate the time difference between their arrival and departure times to determine the user's location.

[0022] 1) Distance measurement The signals transmitted by satellites contain the time of transmission. Upon receiving the signal, the receiver compares the transmission time with the current time. Since electromagnetic waves travel at approximately 300,000 kilometers per second, the distance between the receiver and the satellite can be calculated. For example, if the signal transmission took 0.1 seconds, the distance would be 30,000 kilometers.

[0023] 2) Triangulation Satellite positioning works on the principle of triangulation. When a signal is received from one satellite, an arc can be drawn on the Earth's surface to determine the receiver's location. When a signal is received from a second satellite, another arc can be drawn; the intersection of the two arcs is the receiver's location. When a signal is received from a third satellite, the receiver's exact location can be determined.

[0024] 3) Clock synchronization To ensure measurement accuracy, a fourth satellite is needed for clock synchronization. Slight differences between the satellite and receiver clocks can lead to measurement errors. By introducing a fourth satellite, algorithms can be used to guarantee the clock synchronization of the positioning system.

[0025] Example 1 This embodiment provides a navigation signal broadcasting system based on microwave two-way time synchronization technology, including at least four ground station units deployed in the coverage area, wherein each ground station unit includes one master station and at least three slave stations; like Figure 1 As shown, each of the ground station units includes a ground station host, a timing transceiver antenna, and a navigation signal transmitting antenna; The time synchronization transceiver antenna is used to establish a two-way microwave link between the master station and the slave station. The ground station host uses the two-way microwave link to achieve inter-station time synchronization and measure inter-station pseudorange through two-way single-way pseudorange measurement technology. Furthermore, the timing navigation baseband module is also configured to control the navigation signal to perform frequency hopping at the exact second of transmission according to a pre-stored frequency hopping pattern.

[0026] Specifically, the timing transceiver antenna serves as a bridge for communication between nodes, capable of receiving and transmitting 1020MHz / 1120MHz signals (customizable).

[0027] The ground station host is also used to generate navigation messages based on time synchronization results, and modulate the navigation messages into navigation signals and broadcast them via the navigation signal transmitting antenna so that navigation terminals in the coverage area can receive the navigation signals for positioning.

[0028] Furthermore, the ground station host is a modular portable host with a split cavity structure, which integrates a time-tracking navigation baseband module, a clock module, and a power amplifier module.

[0029] Furthermore, the clock module is connected to the time-system navigation baseband module and is used to provide the time-system navigation baseband module with a reference clock signal and a second pulse signal.

[0030] Furthermore, the timing navigation baseband module is configured to: multiply the reference clock signal to obtain a sampling clock, and sample the rising edge of the second pulse signal to determine the integer second of the navigation signal transmission.

[0031] Furthermore, the timing navigation baseband module is connected to the power amplifier module and is used to output the modulated intermediate frequency signal and control signal to the power amplifier module. The power amplifier module amplifies the intermediate frequency signal and outputs it to the navigation signal transmitting antenna.

[0032] Furthermore, the outer casing of the ground station host is made of rust-proof aluminum and is equipped with dustproof, waterproof, heat dissipation and electromagnetic shielding structures.

[0033] Furthermore, the external interface of the ground station host meets the IP68 protection level requirements.

[0034] Specifically, the main functions of the ground station host are as follows: after downconverting the signal received by the radio frequency front-end to the analog intermediate frequency, the signal is bandpass sampled and the intermediate frequency digital signal is output and sent to the baseband unit SOC processor for signal processing; and the digital QPSK baseband modulation signal generated by the baseband unit SOC processor is orthogonally upconverted to the radio frequency signal.

[0035] In this embodiment, the ground station system consists of four or more ground station units (six stations are used as an example in this case). One ground station unit serves as the master station and five ground station units serve as slave stations. The master station and slave stations establish a microwave link to achieve communication, time and frequency synchronization, and relative distance measurement. Then, navigation signals are broadcast according to a specific signal system, so that navigation terminals within a certain range can receive the broadcast navigation signals and complete the normal positioning function. The system operation diagram is shown in Figure 2.

[0036] pass Figure 2 It is known that the master and slave ground stations are deployed within a 50km range (the power amplifier can be selected according to the area to be covered by the user). After time synchronization is completed, they broadcast specific navigation signals to the navigation terminal, so that the navigation terminal can receive the navigation signals broadcast by the ground station during flight.

[0037] The main workflow of the ground station system is as follows: (1) Link establishment phase: The master station and the slave station each send wireless signals according to their own time stamps to try to establish a link. If they cannot establish a link, they continue to try to establish a link. (2) Link stabilization phase: After the master station and slave station establish a stable bidirectional microwave link, the slave station adjusts its local time in real time by comparing the time difference obtained, so as to achieve relative time synchronization between stations; (3) Signal processing stage: After the inter-station time synchronization, the precise pseudorange between each station is actually measured through the microwave link and packaged according to the relevant protocol.

[0038] (4) Broadcast signal stage: The baseband signal processing module sends the packaged data to the power amplifier module, and after signal amplification, it is broadcast to the navigation terminal through the transmitting antenna at the agreed frequency.

[0039] In this embodiment, the time synchronization function is designed as follows: The ground station employs Dual One-way Range (DOWR) technology, a widely used ranging-time comparison method in modern aerospace telemetry and control. In this method, two ground stations obtain their relative pseudoranges through pseudocode and carrier phase measurements. Clock errors are eliminated through bidirectional measurement, enabling inter-station ranging, time synchronization, and data exchange. The principle of Dual One-way Range (DOWR) is as follows: Figure 3 As shown.

[0040] In the diagram above, the master station and the slave station transmit forward ranging signals and reverse ranging signals respectively, using their own clocks as a reference. Due to the time discrepancy between the two stations, there is a clock difference between the ranging signal frames transmitted by them. At the main station, the time delay between the frame synchronization of the forward ranging signal and the frame synchronization of the reverse ranging signal can be obtained by capturing and tracking the reverse ranging signal. This delay includes not only the electromagnetic wave propagation delay between the antennas of the slave station and the master station, but also... In addition, it also includes the latency of the station's launch equipment. The main station's receiving equipment latency and the clock difference between the secondary station and the primary station The relationship is as follows: (1) Similarly, the time delay can be measured from the slave station. The time relationship: (2) The actual distance and clock difference between the master station and the slave station can be obtained from the above two formulas. (3) (4) set up , ,but (5) (6) Where D is the actual distance between the master station and the slave station. Main station latency For station delay, For the speed of light, t 12 To account for the one-way propagation delay from the station, t 21 The latency of one-way propagation from the main station. There is a clock difference between the ranging signal frames sent by both parties.

[0041] In operation, the measurement and data exchange processes for the master station and the slave station are identical. Taking the slave station as an example, it utilizes the pseudorange measurement value received at the moment of receiving the master station's transmission frame header (in practice, the local delay measurement value measured by the slave station is used). Substitute the calculated distance into equation (1), and simultaneously substitute the pseudorange data (calculated from the local delay measurement value T1 measured by the master station) within the service segment of the received master station transmission frame into equation (2). Equations (5) and (6) give the formulas for calculating the distance between the master station and the slave station and the clock difference between the master station and the slave station.

[0042] In the measurement, and The data can be extracted from the code tracking rings of both the master and slave stations and embedded into the service segment data area of ​​the transmission frame, and then sent to the other station via a bidirectional link; the one-way propagation delay t 12 and t 21 It can be obtained through calibration, and thus accurate distance and time comparison measurement values ​​can be obtained through bidirectional one-way pseudorange measurement. The clock difference and clock drift values ​​obtained by the slave station through calculation (the principle is similar) can be adjusted in real time to make the slave station's frequency standard subjugate to the master station's frequency standard, thereby achieving phase relative synchronization of 1PPS (pulses per second).

[0043] In this embodiment, the navigation signal broadcasting design is as follows: Navigation broadcasting baseband signal processing is completed on the timing navigation baseband module. The module's 10MHz clock is multiplied to 250MHz, and then the rising edge of the module's output at 1PPS is sampled as the integer second of the navigation broadcasting signal. The timing sequence is as follows: Figure 4 As shown.

[0044] The data frames of the navigation broadcast signal from the ground station are fed to the ground station via a serial port. After receiving the data frames, the PS software of the intermediate frequency module at the ground station writes them into the data memory of the baseband PL via the bus. Starting from the transmission time, the PL reads the baseband data, performs parallel-to-serial conversion, and outputs data bits at a rate of one data bit per 5ms.

[0045] The local pseudocode has a code rate of 10 Mcps and a code period length of 10,000 chips. The pseudocode generation is strictly synchronized with the baseband data output. The pseudocode and data are XORed to achieve baseband data spread spectrum.

[0046] The local carrier is implemented using DDFS (Direct Digital Frequency synthesizer, hereinafter referred to as DDS) to generate the local carrier and achieve frequency hopping within 100MHz. The block diagram of the local carrier implementation is as follows. Figure 5 As shown.

[0047] The specific format and parameter design of the frequency hopping pattern are provided by the user. After the ground station is powered on, the frequency hopping pattern for the local task can be initialized and added via the host computer. After receiving the frequency hopping pattern data, the PS software stores it in the local Flash and then writes it into the PL's RAM via the bus.

[0048] The timing of the frequency hopping control unit is aligned with the transmit pulse timing, then frequency hopping time slots are generated, the frequency hopping sequence is read from RAM, and then the frequency control word for the next frequency hopping time slot is calculated.

[0049] In this embodiment, the effective range: the geometric layout constraint of the ground station is the effective range of the ground station, that is, the effective range between each station and the effective range of navigation signal broadcast transmission. Both are closely related to the selected power amplifier module. If the effective range is long and the coverage area is large, a high-power power amplifier module is selected; if the effective range is short and the coverage area is small, a low-power power amplifier module can be selected.

[0050] Based on the user's actual needs, perform link budgeting and select the appropriate power amplifier module. Common navigation signal coverage distances range from 5km to 800km.

[0051] In this embodiment, the product form is as follows: The ground station system is designed with practical usage scenarios in mind, featuring a highly integrated, miniaturized, and portable design. Specifically, the ground station main unit adopts a split-cavity design, primarily composed of a time synchronization and navigation baseband module, a clock module, power amplifier modules (including power amplifier 1 and power amplifier 2), a power supply module, a fan, and structural components. Figure 6 As shown above, the miniaturized design of the ground station main unit makes it easy for users to move, thus greatly improving the system's mobility.

[0052] The core component of the ground station host is the time synchronization and navigation baseband module. Its main time synchronization and navigation signal broadcasting functions are implemented by the time synchronization and navigation baseband module, which will be explained in detail here.

[0053] The timing navigation baseband module hardware mainly consists of an intermediate frequency processing unit, a clock management unit, a baseband unit, a recording unit, a power supply unit, and an interface unit. The motherboard block diagram is shown below. Figure 7 As shown.

[0054] The ground station main unit structure is made of corrosion-resistant 5A06 rust-proof aluminum. The design fully considers dustproof, waterproof, heat dissipation and shielding performance, and has been specifically designed to ensure the reliability of the product in actual use environment.

[0055] Since the ground station operates outdoors, high requirements are placed on dust protection and heat dissipation. Therefore, specific requirements need to be placed on the structural design, with dedicated dust protection and heat dissipation features. This heat dissipation design will utilize air-cooling technology to reduce the temperature of the power amplifier when it becomes too high. A schematic diagram of the ground station's main unit structure is shown below. Figure 8 As shown.

[0056] For operator convenience, the ground station features clearly defined interfaces and panel labels. A diagram of the main unit's rear panel is shown below. Figure 9 As shown. (Through) Figure 9 It is evident that the risk of human error was fully considered during the design of the ground station host interface. All connectors are inconsistent to prevent personnel from plugging them in backwards, which could lead to equipment damage or test abnormalities.

[0057] Furthermore, a lightning protection device is installed at the navigation signal transmitting antenna.

[0058] Specifically, the navigation signal transmitting antenna transmits the 2GHz frequency band (customizable) navigation signal output by the power amplifier to the navigation terminal.

[0059] The ground station's main unit structure was designed with the actual operating environment in mind. The internal components are shielded, and the surface is coated with protective paint. All connectors and switches used meet IP68 waterproof requirements. Lightning protection is incorporated into the transmitting antenna, providing protection against lightning, moisture, rain, mold, shock, dust, rodent bites, insects, and sunlight. It also meets requirements for protection against mold, salt spray, and humidity.

[0060] The innovation of this embodiment lies in its miniaturized design that highly integrates time synchronization and navigation signal broadcasting functions.

[0061] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A navigation signal broadcasting system based on microwave two-way time synchronization technology, characterized in that, It includes at least four ground station units deployed within the coverage area, each ground station unit comprising one master station and at least three slave stations; Each of the ground station units includes a ground station host, a timing transceiver antenna, and a navigation signal transmitting antenna; The time synchronization transceiver antenna is used to establish a two-way microwave link between the master station and the slave station. The ground station host uses the two-way microwave link to achieve inter-station time synchronization and measure inter-station pseudorange through two-way single-way pseudorange measurement technology. The ground station host is also used to generate navigation messages based on time synchronization results, and modulate the navigation messages into navigation signals and broadcast them via the navigation signal transmitting antenna so that navigation terminals in the coverage area can receive the navigation signals for positioning.

2. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 1, characterized in that, The ground station host is a modular portable host with a split cavity structure, which integrates a time-tracking navigation baseband module, a clock module, and a power amplifier module.

3. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 2, characterized in that, The clock module is connected to the time-system navigation baseband module and is used to provide the time-system navigation baseband module with a reference clock signal and a second pulse signal.

4. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 3, characterized in that, The timing navigation baseband module is configured to: multiply the reference clock signal to obtain a sampling clock, and sample the rising edge of the second pulse signal to determine the integer second of the navigation signal transmission.

5. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 2, characterized in that, The timing navigation baseband module is connected to the power amplifier module and is used to output the modulated intermediate frequency signal and control signal to the power amplifier module. The power amplifier module amplifies the intermediate frequency signal and outputs it to the navigation signal transmitting antenna.

6. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 2, characterized in that, The outer casing of the ground station host is made of rust-proof aluminum and is equipped with dustproof, waterproof, heat dissipation and electromagnetic shielding structures.

7. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 6, characterized in that, The external interface of the ground station host meets the IP68 protection level requirements.

8. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 1, characterized in that, A lightning protection device is installed at the navigation signal transmitting antenna.

9. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 4, characterized in that, The timing navigation baseband module is further configured to control the navigation signal to perform frequency hopping at the exact second of transmission according to a pre-stored frequency hopping pattern.

10. The navigation signal broadcasting system based on microwave two-way time synchronization technology according to claim 1, characterized in that, The bidirectional single-way pseudorange measurement technology is implemented in the following way: the master station and the slave station respectively transmit forward ranging signals and reverse ranging signals based on their own clocks, and measure the time delay. and The delay and They respectively satisfy the following relations: ； ； Where D is the actual distance between the master station and the slave station. Main station latency For station delay, For the speed of light, t 12 To account for the one-way propagation delay from the station, t 21 The latency of one-way propagation from the main station. There is a clock difference between the ranging signal frames sent by both parties.

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