A system and method for identifying satellite spoofing signals based on physical characteristics of OCXO

Abstract

The application discloses a system and method for identifying satellite spoofing signals based on physical characteristics of OCXO, comprising: an OCXO module for providing a square wave of a set frequency and transmitting to a FPGA minimum system module; the FPGA minimum system module is used for receiving the square wave signal transmitted by the OCXO module, performing frequency multiplication on the signal, counting the number of square waves between each second pulse, counting the total number of square waves in a set time node, and transmitting the counting result to an ARM minimum system module; the ARM minimum system module obtains the OCXO curve about the number of square waves in a time node through a curve fitting method; and a receiving module is used for receiving GPS satellite signals or Beidou satellite signals and providing second pulse signals for the FPGA minimum system module. The method of the application is not limited by GPS satellite signals or Beidou satellite signals, can judge whether any satellite signal is spoofed, the judgment process is simple, and the judgment result is accurate and reliable.

Description

Technical Field

[0001] This invention relates to the field of power system time synchronization technology, and in particular to a system and method for identifying satellite spoofing signals based on the physical characteristics of OCXO. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] The Global Positioning System (GPS), as a commonly used global satellite navigation system, has been widely applied in fields such as civil aviation, transportation, power systems, and the financial system. As a result, the security of satellite positioning signal transmission has become increasingly important.

[0004] Satellite signals can be subject to various forms of human interference as they propagate through space. For example, deceptive jamming uses interference signals that are identical or similar to the satellite signal to mislead satellite receivers. Deceptive jamming is highly covert and poses a significant threat to specific users.

[0005] In existing technologies, most methods use the "BeiDou in-situ hardening method" to identify satellite spoofing signals. This method uses the BeiDou satellite signal as a reference to determine whether the GPS signal is interfered with or spoofed, and can effectively provide GPS signal interference and spoofing alarms. However, this method is based on the BeiDou signal, and if the BeiDou signal is interfered with or spoofed, it cannot make an accurate judgment. Therefore, the method has certain limitations. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a system and method for identifying satellite spoofing signals based on the physical characteristics of a temperature-controlled crystal oscillator (OCXO). Leveraging the continuous curve characteristic of the OCXO, the frequency changes of the OCXO are monitored in real time. If the curve remains continuous without any step changes, the satellite signal is considered normal. Conversely, if the curve becomes discontinuous and a step change occurs, a spoofing signal has been received.

[0007] In some implementations, the following technical solutions are adopted:

[0008] A system for identifying satellite spoofing signals based on the physical characteristics of OCXOs, comprising:

[0009] The OCXO module is used to provide a square wave of a set frequency and transmit it to the FPGA minimum system module.

[0010] The FPGA minimum system module is used to receive the square wave signal sent by the OCXO module, perform frequency multiplication on the signal, count the number of square waves between each second pulse, and count the total number of square waves within a set time node, and transmit the counting result to the ARM minimum system module.

[0011] The ARM minimum system module obtains the OCXO curve related to the number of square waves within a time node through curve fitting.

[0012] The receiving module is used to receive GPS satellite signals or BeiDou satellite signals and transmit the received signals to the ARM minimum system module, while providing a second pulse signal to the FPGA minimum system module.

[0013] It also includes a judgment module, which is used to determine whether there is a satellite spoofing signal based on whether the fitted OCXO curve is continuous.

[0014] If the OCXO curve obtained by fitting the ARM minimum system module is continuous, it indicates that the GPS satellite or Beidou satellite has not received a spoofing signal.

[0015] If the OCXO curve obtained by fitting the ARM minimum system module has a discontinuity, it indicates that the GPS satellite or BeiDou satellite is being interfered with by spoofing signals at the discontinuity location.

[0016] In other embodiments, the following technical solutions are adopted:

[0017] A satellite signal security isolation device includes: the above-mentioned system for identifying satellite spoofing signals based on the physical characteristics of OCXO.

[0018] In other embodiments, the following technical solutions are adopted:

[0019] A method for identifying satellite spoofing signals based on the physical characteristics of OCXOs includes:

[0020] Receive the square wave signal sent by the OCXO module, perform frequency multiplication on the signal, count the number of square waves between each second pulse, set the number of second pulses included in a time node, and count the total number of square waves in a time node.

[0021] Discrete data on the number of square waves received per second pulse within a given time point are obtained by statistical analysis. The data is then fitted to obtain the OCXO curve.

[0022] Determine if there is a break in the OCXO curve. If so, it indicates that the GPS or BeiDou satellites are being interfered with by deceptive signals at the break location.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) Based on the characteristic that the curve of OCXO is continuous, this invention monitors the frequency change of OCXO in real time. If the curve is continuous and no step occurs, it indicates that the satellite signal is normal. If the curve is discontinuous and a step occurs, it indicates that a deception signal has been received.

[0025] The method of this invention is not limited by GPS satellite signals or BeiDou satellite signals, and can determine whether any satellite signal has been spoofed. The judgment process is simple and the judgment result is accurate and reliable.

[0026] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system structure for identifying satellite spoofing signals based on the physical characteristics of OCXO in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the curve obtained from a normal satellite signal in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the curve obtained after the satellite signal is subjected to deceptive interference in an embodiment of the present invention;

[0030] Figure 4 This is a flowchart of a method for identifying satellite spoofing signals based on the physical characteristics of OCXO in an embodiment of the present invention. Detailed Implementation

[0031] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] 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 scope of exemplary embodiments according to the invention. 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.

[0033] Terminology Explanation:

[0034] OCXO Curve: Assuming the oscillation frequency of the oven-controlled crystal oscillator is 10MHz, a 100MHz square wave is obtained by multiplying the frequency by 10 using the FPGA, which serves as the clock source for FPGA counting. When receiving satellite signals, the satellite signal module sends a second pulse every second. The number of counts during each second pulse is calculated, and then every 1000 seconds is taken as one x-axis unit, with the y-axis representing the number of counts per 1000 seconds, thus yielding the OCXO curve.

[0035] Example 1

[0036] In one or more embodiments, a system for identifying satellite spoofing signals based on the physical characteristics of an OCXO is disclosed, combined with... Figure 1 Specifically, it includes:

[0037] (1) OCXO module, used to provide a square wave of a set frequency and transmit it to the FPGA minimum system module;

[0038] A temperature-controlled crystal oscillator (OCXO) is a crystal oscillator that uses a temperature-controlled bath to keep the temperature of the quartz crystal resonator in the crystal oscillator constant, minimizing the change in the oscillator output frequency caused by changes in ambient temperature. It consists of a temperature-controlled bath control circuit and an oscillator circuit, providing a stable output frequency.

[0039] (2) FPGA minimum system module, used to receive the square wave signal sent by the OCXO module, perform frequency multiplication on the signal, count the number of square waves between each second pulse, set the number of second pulses contained in a time node, count the total number of square waves in a time node, and transmit the counting result to the ARM minimum system module.

[0040] The minimum system module of an FPGA includes an FPGA chip, as well as components such as a crystal oscillator, debug / download interface, and power supply to ensure the normal operation of the FPGA chip.

[0041] (3) The ARM minimum system module obtains the OCXO curve with respect to the number of square waves within a time node by curve fitting method;

[0042] The minimum system module of ARM includes the ARM chip and components such as crystal oscillators (system crystal oscillator and RTC crystal oscillator), debug and download interface, and RTC power supply to ensure the normal operation of the ARM chip.

[0043] (4) Receiver module, used to receive GPS satellite signals or Beidou satellite signals (signals mainly include position signals and time signals), and transmit the received signals to the ARM minimum system module, while providing the FPGA minimum system module with a pulse-per-second (1PPS) signal.

[0044] The receiving module in this embodiment includes:

[0045] The GPS module is an integrated circuit that combines an RF chip, a baseband chip, and a core CPU, along with related peripheral circuits. It is used to receive GPS satellite signals, transmit data to the ARM minimum system module via a serial port, and provide a 1PPS signal to the FPGA minimum system module.

[0046] The Beidou module is an integrated circuit that integrates an RF chip, a baseband chip, and a core CPU, along with related peripheral circuits. It is used to receive Beidou satellite signals, transmit data to the ARM minimum system module via a serial port, and provide 1PPS signals to the FPGA minimum system module.

[0047] (5) Judgment module, used to determine whether there is a satellite spoofing signal based on whether the fitted OCXO curve is continuous.

[0048] If the OCXO curve obtained by fitting the ARM minimum system module is continuous, it indicates that the GPS or BeiDou satellites have not received spoofing signals. If the OCXO curve obtained by fitting the ARM minimum system module has discontinuities, it indicates that the GPS or BeiDou satellites are interfered with by spoofing signals at the discontinuity locations.

[0049] (6) Display module, which is connected to the ARM minimum system module. The display module is used to display the OCXO curve, GPS information, Beidou information and other data obtained by fitting the ARM minimum system module.

[0050] (7) Antenna and feeder system module: GPS antenna and Beidou antenna respectively receive satellite signals and transmit them to FPGA minimum system module through feeder.

[0051] In this embodiment, the OCXO module can output a 10MHz square wave to the FPGA, generate a 100MHz square wave by multiplying the frequency by 10 using a frequency multiplier, count the number of square waves between each 1PPS, count the total number of square waves with 1000 PPS as a time node, and transmit the data to the ARM to draw the OCXO curve.

[0052] A series of discrete data are obtained through sampling and statistics. The curve trend is obtained through curve fitting, and the graph is plotted. The least squares method can be used to fit the curve.

[0053] When the system starts working, it needs to be powered on and maintained in a normal signal environment for a period of time to form a normal curve. Calculations will yield a curve with the horizontal axis representing 1000 seconds and the vertical axis representing the number of counts. The curve will initially show jitter, then smooth out the remaining area continuously. When a deception signal arrives, the count will fluctuate significantly during the first interval, then stabilize, creating a clear discontinuity in the curve. The appearance of this discontinuity indicates that the system has been deceiving the system.

[0054] In this embodiment, based on the continuous curve of the OCXO, the frequency change of the OCXO can be monitored in real time to determine whether it is being interfered with by a deceptive signal.

[0055] When the satellite is not being deceived, after the OCXO module has warmed up, the count value every 1000 seconds is close to the same, and the curve is basically a branch parallel to the x-axis.

[0056] When a satellite is interfered with by deceptive signals, the following situations may occur:

[0057] (1) The deceptive signal has altered the year, month, day, hour, minute, and second. This is easy to determine; you can see it directly in the serial port data. This kind of deception is unlikely to exist.

[0058] (2) If the deception signal is significantly delayed or significantly ahead of the normal time source, and then remains unchanged, then at least 1 second of the count will increase or decrease by a large value during the 1000 seconds when the deception signal arrives, and then remain stable. At this time, the curve will show a clear discontinuity.

[0059] (3) If the deception signal is slightly delayed or slightly ahead of the normal time source and then remains unchanged, but cannot be determined from the curve, this kind of deception has no practical significance and cannot interfere with the normal operation of the time synchronization system.

[0060] Figure 2 The OCXO curve is obtained by fitting a normal satellite signal. The horizontal axis of the curve is in units of 1000s, and the vertical axis is in units of counts. The curve has jitter in the early stage and then smooths out the area. It is continuous and tends to be stable.

[0061] Figure 3 The curve is obtained after the satellite signal is subjected to deception interference. The horizontal axis of the curve is in units of 1000s, and the vertical axis is in units of counts. When there is no deception interference, the curve is still continuous. When the deception signal arrives, the count will change significantly in the first interval, and then tend to stabilize, forming a clear discontinuity in the curve. When a discontinuity appears, it can be judged that the satellite signal has been deceiving.

[0062] Example 2

[0063] In one or more embodiments, a satellite signal security isolation device is disclosed, including: the system for identifying satellite spoofing signals based on the physical characteristics of OCXO as described in Embodiment 1.

[0064] Example 3

[0065] In one or more embodiments, a method for identifying satellite spoofing signals based on the physical characteristics of an OCXO is disclosed, combined with... Figure 4 Specifically, it includes the following process:

[0066] (1) The OCXO module sends a square wave signal with a stable output frequency (e.g., 10MHz);

[0067] The FPGA minimum system module receives the square wave signal sent by the OCXO module, performs frequency multiplication on the signal (for example, by multiplying the frequency by 10 to generate a 100MHz square wave), counts the number of square waves between each second pulse, sets the number of second pulses included in a time node (for example, taking 1000 PPS as a time node), and counts the total number of square waves in a time node.

[0068] (2) The ARM minimum system module statistically obtains discrete data of the number of square waves received per second pulse within a time node, and fits the data to obtain the OCXO curve.

[0069] (3) Determine whether there is a fault in the OCXO curve. If there is, it indicates that the GPS satellite or Beidou satellite is interfered with by a deceptive signal at the fault location.

[0070] (4) Output and display the judgment result.

[0071] The specific implementation of the above process is the same as in Example 1, and will not be described in detail again.

[0072] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A system for identifying satellite spoofing signals based on the physical characteristics of an OCXO, characterized in that, include: The OCXO module is used to provide a square wave of a set frequency and transmit it to the FPGA minimum system module. The FPGA minimum system module is used to receive the square wave signal sent by the OCXO module, perform frequency multiplication on the signal, count the number of square waves between each second pulse, and count the total number of square waves within a set time node, and transmit the counting result to the ARM minimum system module. The ARM minimum system module obtains the OCXO curve related to the number of square waves within a time node through curve fitting. The receiving module is used to receive GPS satellite signals or Beidou satellite signals and transmit the received signals to the ARM minimum system module, while providing a second pulse signal to the FPGA minimum system module. The judgment module is used to determine whether there is a satellite spoofing signal based on whether the fitted OCXO curve is continuous. If the OCXO curve obtained by fitting the ARM minimum system module is continuous, it indicates that the GPS satellite or Beidou satellite has not received a spoofing signal. If the OCXO curve obtained by fitting the ARM minimum system module has a discontinuity, it indicates that the GPS satellite or BeiDou satellite is being interfered with by spoofing signals at the discontinuity location.

2. The system for identifying satellite spoofing signals based on the physical characteristics of OCXO as described in claim 1, characterized in that, Also includes: The display module is connected to the ARM minimum system module and is used to display the OCXO curve obtained by fitting the ARM minimum system module.

3. The system for identifying satellite spoofing signals based on the physical characteristics of OCXO as described in claim 1, characterized in that, A time point consists of a set number of second pulses.

4. A satellite signal security isolation device, characterized in that, include: The system for identifying satellite spoofing signals based on the physical characteristics of OCXO as described in any one of claims 1-3.

5. A method for identifying satellite spoofing signals based on the physical characteristics of an OCXO, characterized in that, The system for identifying satellite spoofing signals based on the physical characteristics of OCXO as described in any one of claims 1-3 includes: Receive the square wave signal sent by the OCXO module, perform frequency multiplication on the signal, count the number of square waves between each second pulse, set the number of second pulses included in a time node, and count the total number of square waves in a time node. Discrete data on the number of square waves received per second pulse within a given time point are obtained by statistical analysis. The data is then fitted to obtain the OCXO curve. Determine if there is a break in the OCXO curve. If so, it indicates that the GPS or BeiDou satellites are being interfered with by deceptive signals at the break location.

Images