Method and system for calibrating very low frequency communication station broadcasting delay

Abstract

The application provides a very low frequency communication station broadcasting delay calibration method and system, comprising: erecting a very low frequency signal detection device at a distance from a communication station; the very low frequency signal detection device receives a very low frequency signal, calculates a signal propagation time delay difference by comparing with a self clock phase and considering a phase lag caused by the distance between the very low frequency signal detection device and the very low frequency communication station, and returns the signal propagation time delay difference to the very low frequency communication station; the very low frequency communication station modulates the signal propagation time delay difference into a very low frequency signal broadcasted by the very low frequency communication station, a user receives and demodulates the very low frequency signal of the very low frequency communication station, obtains a signal propagation time delay difference broadcasted by the very low frequency communication station and corresponding navigation observation, and inputs the signal propagation time delay difference into a navigation equation. The technical scheme of the application solves the technical problem that the very low frequency communication station broadcasted signal has a delay and is difficult to be applied to very low frequency navigation technology in the prior art.

Description

Technical Field

[0001] This invention relates to the field of very low frequency (VLF) navigation technology, and in particular to a method and system for calibrating the broadcast delay of a VLF communication station. Background Technology

[0002] Very low frequency (VLF) radio waves possess strong anti-jamming capabilities and long propagation distances, enabling regional anti-jamming VLF navigation technology that does not rely on satellites, thus addressing situations where navigation systems are denied access. The Defense Advanced Research Projects Agency (DARPA) has designated VLF navigation as one of its key development directions for the next decade. Currently, based on the STOIC (Spatial, Temporal, and Orientation Information in Contested Environments) project, a new generation of VLF navigation systems has been developed. At sea, VLF navigation technology has achieved a navigation accuracy of 40 meters, demonstrating its capabilities. Based on this, it is hoped that a new positioning, navigation, and timing (PNT) system with a positioning accuracy of 10 meters and an operating range of at least 10,000 km can be achieved in the future.

[0003] Very Low Frequency (VLF) navigation stations are the key hardware infrastructure for realizing VLF navigation technology. By receiving signals from multiple VLF navigation stations, VLF navigation and positioning can be achieved using the hyperbolic positioning principle. To achieve high-precision VLF navigation, stable phase references and phase synchronization between stations are typically required. These requirements result in high construction costs for VLF navigation stations, leading to a limited number of existing VLF navigation stations globally. In contrast, VLF communication stations have lower requirements for phase synchronization accuracy, significantly reducing construction costs, and are already widely deployed globally. However, existing VLF communication stations suffer from inconsistent signal transmission delays due to factors such as inconsistencies in equipment models and lack of inter-station phase synchronization. This issue introduces significant measurement errors when using VLF communication station signals for navigation, affecting positioning accuracy and making them unsuitable for navigation applications. Therefore, the development of VLF navigation is limited by the small number of stations and construction difficulties, hindering its widespread application and the formation of large-scale VLF navigation capabilities. Summary of the Invention

[0004] This invention provides a method and system for calibrating the broadcast delay of very low frequency (VLF) communication stations, which can solve the technical problem that the broadcast signals of VLF communication stations have a delay and are difficult to apply to VLF navigation technology in the prior art.

[0005] According to one aspect of the present invention, a method for calibrating the broadcast delay of a very low frequency (VLF) communication station is provided. The method includes: setting up a VLF signal detection device at a predetermined distance from the VLF communication station; the VLF detection device being used to monitor the VLF signal transmitted by the VLF communication station; synchronizing the VLF communication station and the VLF signal detection device via an optical fiber; and receiving the VLF signal transmitted by the VLF communication station via the VLF signal detection device, which then compares the phase of the signal with its own clock. Simultaneously considering the phase lag caused by the distance between the VLF signal detection equipment and the VLF communication station, the signal propagation delay difference of the VLF communication station is calculated and transmitted back to the VLF communication station. The VLF communication station modulates the signal propagation delay difference into its broadcast VLF signal, receives and demodulates the VLF signal from the VLF communication station, obtains the signal propagation delay difference broadcast by the VLF communication station and the corresponding navigation observations, and inputs the signal propagation delay difference into the navigation equation to complete the VLF communication station broadcast delay calibration.

[0006] Furthermore, the signal propagation delay difference τ can be calculated using τ = t2 - t1 - L / c, where t2 is the signal reception time of the very low frequency signal detection device, t1 is the signal generation time of the very low frequency communication station, L is the distance between the very low frequency communication station and the very low frequency signal detection device, and c is the speed of light.

[0007] According to another aspect of the present invention, a very low frequency (VLF) communication station broadcast delay calibration system is provided, which uses the VLF communication station broadcast delay calibration method described above to perform signal delay calibration.

[0008] Furthermore, the very low frequency (VLF) communication station broadcast delay calibration system includes a VLF communication station and a VLF signal detection device. The VLF communication station includes a time control module, a power control module, and a transmission module. The VLF signal detection device includes a receiving antenna and a signal processing module. The power control module is used to control the transmission power of the VLF signal. The transmission module is used to transmit the VLF signal. The receiving antenna is used to receive the VLF signal transmitted by the transmission module. The signal processing module is used to process the VLF signal to obtain the signal propagation delay difference. The time control module is used to receive the signal propagation delay difference.

[0009] The present invention provides a method for calibrating the broadcast delay of a very low frequency (VLF) communication station. This method involves setting up a VLF signal detection device near the VLF communication station to monitor the VLF signal transmitted by the station; analyzing the phase of the VLF signal received by the detection device and comparing it with the distance between the receiving device and the transmitting station to obtain the station's own signal propagation delay difference; then transmitting this signal propagation delay difference back to the VLF communication station, which modulates it into the broadcast navigation signal; the receiving user receives and demodulates the station's VLF signal to obtain the VLF station's broadcast delay and corresponding navigation observations; by inputting the broadcast delay as an error parameter into the corresponding navigation equation, and calibrating the effect of the broadcast delay through algorithm processing, high-precision navigation and positioning are achieved. Compared with existing technologies, the VLF communication station broadcast delay calibration method provided by this invention can monitor and correct the broadcast delay of VLF communication stations; it can eliminate the influence of VLF communication station broadcast delay and realize VLF navigation technology based on VLF communication stations; and it is simple and inexpensive to implement, making it easy to quickly promote and apply. Attached Figure Description

[0010] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0011] Figure 1 A schematic diagram illustrating the principle of a very low frequency communication station broadcast delay calibration method according to a specific embodiment of the present invention is shown. Detailed Implementation

[0012] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0014] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0015] like Figure 1 As shown in the figure, a method for calibrating the broadcast delay of a very low frequency (VLF) communication station is provided according to a specific embodiment of the present invention. The method includes: setting up a VLF signal detection device at a predetermined distance from the VLF communication station; the VLF detection device being used to monitor the VLF signal transmitted by the VLF communication station; synchronizing the VLF communication station and the VLF signal detection device via optical fiber to achieve signal clock synchronization; receiving the VLF signal transmitted by the VLF communication station via the VLF signal detection device, and the VLF signal detection device calibrating the signal by comparing its phase with its own clock. Yes, while considering the phase lag caused by the distance between the VLF signal detection equipment and the VLF communication station, the signal propagation delay difference of the VLF communication station is calculated and transmitted back to the VLF communication station. The VLF communication station modulates the signal propagation delay difference into its broadcast VLF signal, receives and demodulates the VLF signal received by the user, obtains the signal propagation delay difference broadcast by the VLF communication station and the corresponding navigation observations, and inputs the signal propagation delay difference into the navigation equation to complete the VLF communication station broadcast delay calibration.

[0016] This configuration provides a method for calibrating the broadcast delay of a Very Low Frequency (VLF) communication station. The method involves setting up a VLF signal detection device near the VLF communication station to monitor the VLF signals transmitted by the station; analyzing the phase of the VLF signals received by the detection device and comparing it with the distance between the receiving device and the transmitting station to obtain the station's own signal propagation delay difference; transmitting the signal propagation delay difference back via a wired method (such as a fiber optic link) and having the VLF communication station modulate it into its broadcast navigation signal; receiving users receive and demodulate the station's VLF signal to obtain the VLF station's broadcast delay and corresponding navigation observations; inputting the broadcast delay as an error parameter into the corresponding navigation equation; and calibrating the effect of the broadcast delay through algorithm processing to achieve high-precision navigation and positioning. Compared with existing technologies, the VLF communication station broadcast delay calibration method provided by this invention can monitor and correct the broadcast delay of VLF communication stations; it can eliminate the influence of VLF communication station broadcast delay and realize VLF navigation technology based on VLF communication stations; and it is simple and inexpensive to implement, making it easy to quickly promote and apply.

[0017] Furthermore, in this invention, the signal propagation delay difference τ can be calculated according to τ = t2 - t1 - L / c, where t2 is the signal reception time of the very low frequency signal detection device, t1 is the signal generation time of the very low frequency communication station, L is the distance between the very low frequency communication station and the very low frequency signal detection device, and c is the speed of light.

[0018] According to another aspect of the present invention, a very low frequency (VLF) communication station broadcast delay calibration system is provided, which uses the VLF communication station broadcast delay calibration method described above to perform signal delay calibration.

[0019] This configuration provides a Very Low Frequency (VLF) communication station broadcast delay calibration system. The system monitors the VLF signals transmitted by the VLF communication station by setting up VLF signal detection equipment near the station. It analyzes the phase of the VLF signals received by the detection equipment and compares this phase with the distance between the receiving equipment and the transmitting station to determine the station's own signal propagation delay difference. This difference is then transmitted back via a wired method (such as a fiber optic link) and modulated into the broadcast navigation signal by the VLF communication station. The receiving user receives and demodulates the station's VLF signal to obtain the VLF station broadcast delay and corresponding navigation observations. By inputting the broadcast delay as an error parameter into the corresponding navigation equation and using an algorithm to calibrate the effect of the broadcast delay, high-precision navigation and positioning are achieved. Compared with existing technologies, the VLF communication station broadcast delay calibration system provided by this invention can monitor and correct the broadcast delay of VLF communication stations; it can eliminate the influence of VLF communication station broadcast delay and realize VLF navigation technology based on VLF communication stations; and it is simple and inexpensive to implement, making it easy to quickly promote and apply.

[0020] Furthermore, in this invention, in order to achieve very low frequency (VLF) communication station broadcast delay calibration, the VLF communication station broadcast delay calibration system includes a VLF communication station and a VLF signal detection device. The VLF communication station includes a time control module, a power control module, and a transmission module. The VLF signal detection device includes a receiving antenna and a signal processing module. The power control module is used to control the transmission power of the VLF signal. The transmission module is used to transmit the VLF signal. The receiving antenna is used to receive the VLF signal transmitted by the transmission module. The signal processing module is used to process the VLF signal to obtain the signal propagation delay difference. The time control module is used to receive the signal propagation delay difference.

[0021] To gain a further understanding of the present invention, the following description is provided in conjunction with... Figure 1 The present invention provides a detailed description of the very low frequency communication station broadcast delay calibration method and system.

[0022] like Figure 1 As shown in the figure, a method for calibrating the transmission delay of a very low frequency (VLF) communication station is provided according to a specific embodiment of the present invention. By correcting the transmission delay of the VLF communication station with high precision, the phase accuracy of the VLF communication station is improved, making it applicable to VLF navigation technology. Based on the widespread deployment and relatively low cost of VLF communication stations, VLF navigation capability can be quickly formed, thus providing a new solution based on VLF communication stations for the difficulties in promoting and applying VLF navigation technology caused by the high construction cost and limited global deployment of VLF navigation stations.

[0023] The main solution of this technology is to monitor the broadcast delay of signal transmission near the transmitting end and synchronously transmit this delay back to the Very Low Frequency (VLF) communication station via an optical fiber link. The VLF communication station then modulates this delay into the navigation signal and broadcasts it to the user receiver. During positioning calculation, the receiver corrects the distance measurement value based on the received delay values ​​from different stations, eliminating the impact of broadcast delay errors caused by the transmitting base station equipment and improving positioning and navigation accuracy. The VLF station equipment broadcast delay self-calibration technology scheme is as follows: Figure 1 As shown.

[0024] A Very Low Frequency (VLF) communication station mainly consists of three modules: a time control module, a power control module, and a transmission module. The VLF signal detection equipment comprises a receiving antenna and a signal processing module. The time control module, power control module, and transmission module of the VLF communication station are synchronized with the detection end via optical fiber. The VLF signal transmitted by the VLF communication station is received by the VLF signal detection equipment. The equipment compares the signal phase with its own clock, taking into account the phase lag caused by the distance L between the receiver and the VLF communication station, to calculate the transmission delay of the transmitting station. This delay is then transmitted back to the time control module of the VLF communication station, modulated, and simultaneously transmitted by the VLF communication station. The signal is then received by the user terminal. By using the delay information as error input to the signal calculation algorithm, the VLF signal positioning calculation is corrected, thereby realizing VLF navigation and positioning technology based on the VLF communication station.

[0025] The specific calculation method for the delay is as follows: A Very Low Frequency (VLF) communication station generates a VLF navigation signal, which is then broadcast after a device delay time τ. A VLF signal detection device is set up at a distance L relative to the VLF communication station, with its receiving antenna fixed to receive the navigation signal broadcast by the VLF communication station. The VLF signal detection device and the VLF communication station are connected by optical fiber for time synchronization; the synchronization accuracy is negligible compared to the ranging error. The VLF signal detection device estimates the VLF communication station's device delay time τ by measuring the signal propagation delay difference and comparing it with the known distance L between the VLF signal detection device and the VLF communication station. Assuming the signal generation time at the VLF communication station is t1 and the signal reception time at the VLF signal detection device is t2, the specific algorithm formula is as follows:

[0026] τ=t2-t1-L / c

[0027] By transmitting the calculated delay τ back to the VLF communication station and transmitting it along with the VLF navigation signal via modulation, the receiving user can correct the navigation and positioning based on the delay τ, thereby achieving high-precision VLF navigation and positioning based on the VLF communication station signal.

[0028] The beneficial effects of this invention are: it can monitor and correct the broadcast delay of very low frequency (VLF) communication stations; it can eliminate the impact of VLF communication station broadcast delay and realize VLF navigation technology based on VLF communication stations; and it achieves simple and inexpensive hardware, which is convenient for rapid promotion and application.

[0029] Additional beneficial effects: Using very low frequency (VLF) communication stations to achieve VLF navigation helps reduce the application cost of VLF navigation technology; given the wide distribution of existing VLF communication stations globally, VLF navigation technology based on VLF communication stations can quickly form navigation capabilities in a short period of time without the need for large-scale time and effort to build infrastructure.

[0030] In summary, to address the problem of delays in VLF (Very Low Frequency) communication station broadcast signals hindering their application in VLF navigation technology, this invention proposes a VLF communication station broadcast delay calibration method. This method calibrates the transmission delay of VLF communication stations to a level that meets navigation requirements, thereby enabling the use of VLF communication stations for VLF navigation technology. This reduces reliance on VLF navigation stations and allows for the widespread adoption of VLF navigation technology through the globally distributed network of VLF communication stations.

[0031] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0032] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0033] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating broadcast delay at a very low frequency communication station, characterized in that, The very low frequency communication station broadcast delay calibration method includes: A very low frequency (VLF) signal detection device is installed at a set distance from the VLF communication station. The VLF detection device is used to monitor the VLF signals emitted by the VLF communication station. The very low frequency communication station and the very low frequency signal detection equipment are synchronized via optical fiber; The very low frequency (VLF) signal transmitted by the VLF communication station is received by the VLF signal detection device. The VLF signal detection device calculates the signal propagation delay difference of the VLF communication station by comparing the phase with its own clock and taking into account the phase lag caused by the distance between the VLF signal detection device and the VLF communication station. The signal propagation delay difference is then transmitted back to the VLF communication station. The very low frequency (VLF) communication station modulates the signal propagation delay difference into its broadcast VLF signal, receives and demodulates the VLF signal from the VLF communication station, obtains the signal propagation delay difference broadcast by the VLF communication station and the corresponding navigation observations, and inputs the signal propagation delay difference into the navigation equation to complete the VLF communication station broadcast delay calibration.

2. The very low frequency communication station broadcast delay calibration method according to claim 1, characterized in that, The signal propagation delay difference τ can be calculated according to τ=t2-t1-L / c, where t2 is the signal reception time of the very low frequency signal detection device, t1 is the signal generation time of the very low frequency communication station, L is the distance between the very low frequency communication station and the very low frequency signal detection device, and c is the speed of light.

3. A very low frequency communication station broadcast delay calibration system, characterized in that, The very low frequency (VLF) communication station broadcast delay calibration system uses the VLF communication station broadcast delay calibration method as described in claim 1 or 2 to perform signal delay calibration.

4. The very low frequency communication station broadcast delay calibration system according to claim 3, characterized in that, The very low frequency (VLF) communication station broadcast delay calibration system includes a VLF communication station and a VLF signal detection device. The VLF communication station includes a time control module, a power control module, and a transmission module. The VLF signal detection device includes a receiving antenna and a signal processing module. The power control module is used to control the transmission power of the VLF signal. The transmission module is used to transmit the VLF signal. The receiving antenna is used to receive the VLF signal transmitted by the transmission module. The signal processing module is used to process the VLF signal to obtain the signal propagation delay difference. The time control module is used to receive the signal propagation delay difference.

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