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WO2012105747A1 - Système, appareil et procédé d'élimination de brouillage dans un signal de navigation de système mondial de navigation par satellites (gnss) - Google Patents

Système, appareil et procédé d'élimination de brouillage dans un signal de navigation de système mondial de navigation par satellites (gnss) Download PDF

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Publication number
WO2012105747A1
WO2012105747A1 PCT/KR2011/009239 KR2011009239W WO2012105747A1 WO 2012105747 A1 WO2012105747 A1 WO 2012105747A1 KR 2011009239 W KR2011009239 W KR 2011009239W WO 2012105747 A1 WO2012105747 A1 WO 2012105747A1
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Prior art keywords
signal
interference
value
set value
serial signal
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PCT/KR2011/009239
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English (en)
Inventor
Juno Kim
Junseung BAE
Jongchul CHO
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Agency for Defence Development
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Agency for Defence Development
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Priority to EP11857847.5A priority Critical patent/EP2656108A4/fr
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/21—Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/421—Determining position by combining or switching between position solutions or signals derived from different satellite radio beacon positioning systems; by combining or switching between position solutions or signals derived from different modes of operation in a single system

Definitions

  • the present invention relates to a system, an apparatus and a method for removing interference in a navigation signal of a global navigation satellite system (GNSS), and more particularly, to a system, an apparatus and a method for removing interference in a navigation signal of a GNSS system which can simplify interference removing modules arranged discriminately according to GNSS modes.
  • GNSS global navigation satellite system
  • GNSS global navigation satellite system
  • GPS global navigation satellite system
  • GLONASS global navigation satellite system
  • GALILEO global navigation satellite system
  • the GNSS despite its use in a wide range of applications, is too susceptible to intentional or unintentional electromagnetic interference or jamming because of the signaling system open to public and weak receiving power lower than the receiver noise level. Persistent efforts have been made to overcome this problem.
  • a digital signal processor additionally provided as an interference removing module is normally used to eliminate narrow-band or partial-band interference prior to calculation of a pseudo distance to the GNSS satellite.
  • the digital signal processing technique applied to the digital signal processor comes in two classes: overlapped fast Fourier transform (OFFT) in frequency domain and adaptive transversal filter algorithm in time domain.
  • both OFFT and adaptive transversal filter algorithms exhibit excellent performance in dealing with static interference.
  • the OFFT shows good performance against partial-band interference such as FM inference or sweeping because of its rapid response.
  • partial-band interference such as FM inference or sweeping because of its rapid response.
  • Such an OFFT requires a large quantity of arithmetic logics for time-to-frequency conversion, scale conversion to calculate the noise level, and statistical processing.
  • the use of the OFFT, particularly in the GNSS receiver accompanies an increase in computational complexity and the quantity of the resource by the number of frequency bands (i.e., GNSS modes). For that reason, the conventional GNSS receivers primarily adopt the time-domain interference processing technique that needs relatively less resource.
  • the present invention provides a system for removing interference in a navigation signal of a global navigation satellite system (GNSS) that includes: a signal reception processor being arranged as many as a plurality of GNSS modes and converting a navigation signal received from navigation satellites through an antenna into an intermediate frequency (IF) signal in digital form according to the respective GNSS modes; an interference remover for processing the IF signal by time division to generate a single serial signal, removing interference from the serial signal, and then distributing the serial signal according to the respective GNSS modes; and a GNSS receiver for receiving and processing the distributed serial signal.
  • GNSS global navigation satellite system
  • an apparatus for removing interference in a navigation signal of a global navigation satellite system that includes: a serial signal generating portion for switching a digital intermediate frequency (IF) signal received in parallel according to respective GNSS modes in predetermined time intervals, to generate a serial signal through one second output terminal; an interference processing portion for removing interference equal to or greater than a set value from the serial signal; and a parallel signal generating portion for receiving the interference-removed serial signal, and switching the serial signal in the predetermined time intervals to generate a parallel signal through a fourth output terminal arranged according to the respective GNSS modes.
  • GNSS global navigation satellite system
  • the serial signal generating portion includes: an input buffer portion for receiving and storing the IF signal; and a first switching portion for switching between a first output terminal outputting the parallel IF signal stored in the input buffer portion and the second output terminal.
  • the parallel signal generating portion includes: an output buffer portion having the fourth output terminal and an input terminal corresponding to the fourth output terminal; and a second switching portion for switching between a third output terminal outputting the interference-removed serial signal of the interference processing portion and the input terminal.
  • the input buffer portion stores the IF signal for at least one period of the switching
  • the output buffer portion stores the switched signal of the second switching portion for at least one of the switching.
  • the interference processing portion includes: a signal converting portion for converting the serial signal generated from the serial signal generating portion from time domain to frequency domain; an interference removing portion for removing interference equal to or greater than a set value from the converted serial signal; and a signal inverse converting portion for converting the interference-removed serial signal from frequency domain to time domain.
  • the apparatus further includes a set value calculating portion for calculating the set value.
  • the interference removing portion includes: an absolute value calculating portion for calculating an absolute value of each sampling interval of the converted serial signal; a delaying portion for delaying the converted serial signal for a set value calculation time of the set value calculating portion; and an interference removal executing portion for comparing the absolute value and the set value, and removing the sampling interval of the delayed serial signal having the absolute value equal to or greater than the set value.
  • the removal of the sampling interval includes substituting any one of zero '0', a threshold, and a noise value for a value of the sampling interval.
  • the set value calculating portion includes: a bit converting portion for receiving the calculated absolute value, and having fewer bits than the bits for representing the absolute value; and a set value generating portion for calculating and generating the set value as the median in a frequency distribution of the output of the bit converting portion or the average of the output of the bit converting portion.
  • the set value generating portion includes: a histogram generating portion for generating a histogram in units of bits allocated according to the respective GNSS modes, the histogram having the output of the bit converting portion plotted on a horizontal axis, and the frequency of the output of the bit converting portion plotted on a vertical axis; and a median generating portion for calculating and generating the median as the output on the horizontal axis representing half the area of the histogram.
  • the histogram generating portion includes: a scale converting buffer for cumulatively increasing a value stored in an address corresponding to the output of the bit converting portion by 1 each time receiving the output value of the bit converting portion; and a cumulative value output portion for sequentially outputting the cumulative value along with the value of the address in order from least significant to most significant address, when the number of the outputs of the bit converting portion meets a sampling number of the unit of bits.
  • the median generating portion calculates and generates the median as the value of the address corresponding to the last input cumulative value, when the sum of the cumulative values meets half the sampling number of the unit of bits.
  • the set value generating portion further includes: a fourth switching portion for performing switching in the predetermined time intervals to output the generated median to a fifth output terminal arranged according to the respective GNSS modes; a set value buffer being connected to the fifth output terminal to receive and store the generated median; a multiplying portion for multiplying the stored median by a predetermined multiplier; and a fifth switching portion for switching the multiplied median in the predetermined time intervals to a single output terminal, and transferring the median to the interference removal executing portion.
  • a method for removing interference in a navigation signal of a global navigation satellite system that includes the steps of: switching a digital intermediate frequency (IF) signal received in parallel according to respective GNSS modes in predetermined time intervals to generate a single serial signal through a single second output terminal, and converting the serial signal of the second output terminal from time domain to frequency domain; removing interference equal to or greater than a set value from the converted serial signal; and inversely converting the interference-removed serial signal from frequency domain to time domain.
  • GNSS global navigation satellite system
  • the interference removing step includes the steps of: calculating an absolute value of each sampling interval of the converted serial signal; calculating the set value using the absolute value; delaying the converted serial signal for a set value calculation time of the set value calculating step; and comparing the absolute value and the set value, and removing the sampling interval of the delayed serial signal having the absolute value equal to or greater than the set value.
  • the set value calculating step includes generating the set value as the median of a frequency distribution of the absolute value or the average of the absolute value.
  • the set value calculating step includes the steps of: converting the absolute value to have fewer bits than the bits for representing an absolute value of the interference; and generating the set value as the median in a frequency distribution of the converted absolute value or the average of the converted absolute value.
  • the set value generating step includes the steps of: generating a histogram in units of bits allocated to the respective GNSS modes, the histogram having the converted absolute value plotted on a horizontal axis thereof, and the frequency of the converted absolute value on a vertical axis thereof; and calculating and generating the median as the absolute value on the horizontal axis representing half the area of the histogram.
  • the histogram generating step includes the steps of: cumulatively increasing a value stored in an address of a storing portion corresponding to the converted absolute value by 1 each time receiving the converted absolute value; and sequentially outputting the cumulative value along with the value of the address in order from least significant to most significant address, when the number of the input absolute value meets the unit of bits.
  • the median calculating and generating step includes: calculating and generating the median as the value of the address corresponding to the last input cumulative value, when the sum of the cumulative values meets half the unit of bits.
  • the above-described method for removing interference in a navigation signal of a GNSS system may be recorded on a computer-readable record medium in a program.
  • the system, the apparatus and the method for removing interference in a navigation signal of a GNSS system involves converting signals received in different GNSS modes into a time divided serial signal through a switching operation, and eliminating interference from the serial signal, thereby simplifying the construction of the interference removing device.
  • the present invention uses only one interference removing device, which is necessarily needed as many as the GNSS modes in the prior art.
  • the present invention can adopt a signal reception processor for converting navigation signals into digital intermediate frequency (IF) signals and a GNSS receiver according to the conventional method, and thus can use the conventional signal reception processor and GNSS receiver.
  • IF digital intermediate frequency
  • the present invention enhances productivity with a simple construction that uses buffers and switching elements.
  • the present invention can also show a reliable interference removal performance by calculating a set value for use in the interference removal process based on the received navigation signal.
  • the present invention provides a solution to process the removed interference as a threshold or noise value instead of zero 0, thereby acquiring signals more approximating the original signal.
  • the set value can be determined with reliability through a simple construction using a bit converting portion that has fewer bits than the bits needed for representing the absolute value of the interference.
  • the present invention can implement more rapid and accurate calculation of the set value by introducing the concept of histogram to compute the set value as the median in a frequency distribution of the absolute value.
  • FIG. 1 is a block diagram showing a system for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 2 is a block diagram showing an apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 3 is a schematic showing serial signals fed into the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 4 is a block diagram showing a preferred embodiment of an interference removing portion included in the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention
  • FIG. 5 is a block diagram showing a preferred embodiment of a set value calculating portion included in the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 6 is a schematic showing a histogram generated by a histogram generating portion included in the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 7 is a flow chart showing a method for removing interference in a navigation signal of a GNSS system according to the present invention.
  • FIG. 1 is a block diagram showing a system for removing interference in a navigation signal of a GNSS system according to the present invention.
  • the system for removing interference in a navigation signal of a GNSS system as shown in FIG. 1 includes: a signal reception processor 500 being arranged as many as a plurality of GNSS modes and converting navigation signals received from navigation satellites through an antenna 510 into digital IF (Intermediate Frequency) signals according to the respective GNSS modes; an interference remover 100 for processing the respective IF signals by time division to generate a single serial signal, removing interference from the serial signal, and then distributing the serial signal according to the respective GNSS modes; and a GNSS receiver 700 for receiving and processing the individual serial signal distributed.
  • a signal reception processor 500 being arranged as many as a plurality of GNSS modes and converting navigation signals received from navigation satellites through an antenna 510 into digital IF (Intermediate Frequency) signals according to the respective GNSS modes
  • an interference remover 100 for processing the respective IF signals by time division to generate a single serial signal, removing interference from the serial signal, and then distributing the serial signal according to the respective GN
  • GNSS Global navigation satellite system
  • GLONASS Global navigation satellite system
  • GALILEO Global navigation satellite system
  • the first navigation system is the United States’ global positioning system (GPS), which was initially designed for military purpose in 1978 by the United States Department of Defense and began to use 24 satellites orbiting the earth in 1995.
  • GPS global positioning system
  • the GPS system that was initially developed for the purpose of ballistic missile guidance extended its usage in a wide range of civil applications including automatic navigation systems equipped in aircrafts, vessels, land vehicles, etc., shortly after the Cold War ended.
  • GLONASS Global Navigation Satellite System
  • GALILEO Globalileo Project
  • the signal reception processor 500 is arranged as many as the GNSS modes that are received at the antenna 510.
  • the term “GNSS mode” as used herein refers to the above-mentioned GNSS system. Thus three signal reception processors are arranged in the case of using three systems of GPS, GLONASS and GALILEO altogether.
  • the GNSS mode can be defined by the frequency band used for a specific GNSS system.
  • the signal reception processor generates an input signal of a digital signal processor that digitally processes the interference of a jammer.
  • the signal reception processor may include an analog-to-digital converter (ADC) for converting analog signals received at the antenna into digital IF (Intermediate Frequency) signals, and a down converter.
  • ADC analog-to-digital converter
  • the interference remover 100 which is a device corresponding to the digital signal processor, performs time division process for the IF signals received from the respective signal reception processors to generate a single serial signal. Then the interference remover eliminates interference from the serial signal and distributes the serial signal according to the respective GNSS modes. In this manner, the interference remover can process all the GNSS modes with only one sub module that substantially removes interference.
  • the interference remover 100 may include switching elements and buffers.
  • the interference remover may also include an IF up converter in the case that the GNSS receiver does not include any other element for up-converting IF signals to the original navigation signal level. In this manner, the present invention can use the conventional GNSS receivers.
  • the GNSS receiver 700 is a receiver that provides not only the positioning information of aircrafts, vessels or land vehicles but also its own geographical information anywhere in the world with accuracy using a satellite network.
  • the GNSS receiver uses navigation signals received from four GNSS satellites to determine the current position. Normally, the current position information can be computed using navigation signals from three GNSS satellites through triangulation. But one more GNSS satellite is additionally needed to compute equations for minimizing errors caused by the difference in arrival time among the respective navigation signals and the internal processing time of the GNSS receiver.
  • the GNSS receiver includes an antenna, and a current position calculating portion for calculating a current position from the received navigation signals.
  • the antenna may be connected to the signal reception processor 500 to eliminate interference of a jammer, as specified in the present invention.
  • the outputs of the signal reception processor and the interference remover are arranged in parallel as many as the GNSS modes.
  • the interference remover converts the parallel signals from the signal reception processor into a serial signal, eliminates interference from the serial signal and then converts the serial signal back to parallel signals. In this manner, interference for all the GNSS modes can be eliminated with only one sub module that substantially removes the interference.
  • FIG. 2 is a block diagram showing an apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention as shown in FIG. 2 may be the interference remover 100 of FIG. 1.
  • the apparatus for removing interference in a navigation signal of a GNSS system includes: a serial signal generating portion 200 for switching digital IF signals received in parallel according to the respective GNSS modes at predetermined time intervals to generate a single serial signal through a single second output terminal; an interference processing portion 300 for removing interference equal to or greater than a set value from the serial signal; and a parallel signal generating portion 400 for receiving and switching the interference-removed serial signal at predetermined time intervals to generate parallel signals through fourth output terminals arranged according to the respective GNSS modes.
  • the serial signal generating portion 200 converts the digital IF signals received in parallel from the signal reception processor into a time divided serial signal, and outputs the serial signal through a single second output terminal.
  • the serial signal generating portion 200 may include: an input buffer portion 210 for receiving and storing the respective IF signals; and a first switching portion 230 for switching between first output terminals outputting in parallel the IF signals stored in the input buffer portion 210 and the second output terminal.
  • the input buffer portion 210 receives and stores the IF signals from the signal reception processor, in order to prevent erasing of the IF signals output through the output terminals other than the first output terminals switched by the first switching portion 230.
  • the input buffer portion 210 may include input buffers 211 as many as the GNSS modes. As the number of the GNSS modes is equal to the number of the output terminals of the signal reception processor, the input buffers is the same in number as the output terminals of the signal reception processor. Here, the output terminals of the input buffers constitute the first output terminals.
  • the input buffers that consist of Dual Port RAMs (DPRAMs) may implement both input and output operations simultaneously by separating input terminals from output terminals.
  • DPRAMs Dual Port RAMs
  • the first switching portion 230 switches from the single second output terminal to a plurality of the first output terminals to generate a single serial signal to one of the first output terminals.
  • the first switching portion performs switching at predetermined time intervals. In other words, the respective switching intervals are all the same in time interval.
  • the serial signal is formed in an order of an IF signal in GNSS mode 1, an IF signal in GNSS mode 2, an IF signal in GNSS mode 3, and an IF signal in GNSS mode 1, as illustrated in FIG. 3.
  • the predetermined time interval may be determined by the user.
  • the switching operation of the first switching portion is a sequential switching operation for the first output terminals, rather than a random switching operation. With three of the first output terminals used for two GNSS modes, only two of the first output terminals involve the switching operation.
  • the parallel signal generating portion 400 includes: an output buffer portion 410 having the fourth output terminals and input terminals corresponding to the respective fourth output terminals; and a second switching portion 430 for switching between a third output terminal outputting the interference?removed serial signal of the interference processing portion and the respective input terminals.
  • the output buffer portion 410 has the fourth output terminals as many as the GNSS modes.
  • the output buffer portion 410 may include output buffers 411 as many as the GNSS modes.
  • the output terminals of the output buffers may constitute the fourth output terminals.
  • the output buffer 411 stores only the signals of a same GNSS mode among the serial signals for which the interference-removing has been completed. Without output buffers, the output signal of the fourth output terminal corresponding to GNSS mode 1 may have intervals in FIG. 3 with t2 and t3 missed.
  • the output buffers move the IF signal of GNSS mode 1 in interval t4 to interval t2, generating the IF signal in a similar form (excepting the interference processing) as the output of the signal reception processor.
  • the output buffers consist of DPRAMs to implement both input and output operations simultaneously.
  • the second switching portion 430 switches between the third output terminal outputting the serial signal for which the interference are removed in the interference processing portion and the input terminals of the output buffer portion, to convert the serial signal into a parallel signal.
  • the third output terminal is the output terminal of the interference processing portion.
  • the interference processing portion is to process the serial signal, and thus the third output terminal may also consist of one terminal for the serial signal.
  • the output buffer portion includes output buffers as many as the GNSS modes, each output buffer having its own input terminal, so a plurality of input terminals are provided in the output buffer portion. Therefore, the second switching portion switches between the single third output terminal and a plurality of the input terminals of the output buffer portion. Through this switching process, the serial signal may be distributed to a plurality of the output buffers to generate a parallel signal.
  • the second switching portion is the same in switching time interval as the first switching portion.
  • the predetermined time interval for a switching operation in the second switching portion is equal to the predetermined time interval for a switching operation in the first switching portion.
  • the input buffer portion necessarily stores the respective IF signals for at least one period of the first switching operation, and the output buffer portion stores the switched signal of the second switching portion for at least one period of the second switching operation.
  • the interference processing portion 300 processes interference of the serial signal generated from the serial signal generating portion. More specifically, the interference processing portion analyzes the serial signal to remove a signal having a magnitude equal to or greater than a set value as an interference signal caused by a jammer.
  • the interference processing portion includes: a signal converting portion 310 for converting the serial signal generated from the serial signal generating portion from time domain to frequency domain; an interference removing portion 330 for removing interference equal to or greater than a set value from the converted serial signal; and a signal inverse converting portion 350 for converting the interference-removed serial signal from frequency domain to time domain.
  • the serial signal from the serial signal generating portion is a signal in the time domain.
  • the signal converting portion 310 converts the serial signal from time domain to frequency domain.
  • the signal converting portion 310 may include an FFT (Fast Fourier Transform) portion.
  • the signal inverse converting portion 350 receives the interference-removed serial signal from the interference removing portion 330 and converts the serial signal from frequency domain to time domain.
  • the signal inverse converting portion 350 may include an IFFT (Inverse Fast Fourier Transform) portion.
  • the interference removing portion 330 removes interference equal to or greater than a set value from the serial signal converted to the frequency domain by the signal converting portion.
  • the set value may be a value determined previously. Otherwise, the set value may be generated based on the serial signal in order to improve reliability of the inference removing process.
  • the interference processing portion may further include a set value calculating portion 370 for calculating the set value.
  • the interference removing portion and the set value calculating portion can be embodied in different constructions.
  • FIG. 4 is a block diagram showing an embodiment of the interference removing portion included in the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • the interference removing portion 330 as shown in FIG. 4 includes: an absolute value calculating portion 331 for calculating an absolute value for each sampling interval of the converted serial signal of the serial signal generating portion 200; a delaying portion 333 for delaying the converted serial signal for the set value calculation time of the set value calculating portion; and an interference removal executing portion 335 for comparing the absolute value and the set value calculated, and removing a sampling interval of the delayed serial signal of which the calculated absolute value is equal to or greater than the set value.
  • the interference removing portion as shown in FIG. 4 removes interference of a jammer using only the magnitude of each signal.
  • the absolute value calculating portion 331 just calculates the magnitude of the converted serial signal to give an absolute value as the result value.
  • the absolute value calculating portion computes the absolute value of each sampling interval (e.g., sampling intervals obtained by splitting each sampling interval t1, t2, t3 or t4 of Fig. 3) of the serial signal.
  • the delaying portion 333 delays the serial signal for the set value calculation time of the set value calculating portion. This process causes the interference removal executing portion to synchronize with the set value calculating portion.
  • the set value calculating portion computes the set value using the calculated absolute value of the absolute value calculating portion, or predetermines the set value by itself. In the former case, the set value calculating portion determines the set value as the average of the absolute value calculated by the absolute value calculating portion, or the median in a frequency distribution of the absolute value.
  • the delaying portion may further delay the serial signal for the absolute value (magnitude) calculation time of the absolute value calculating portion.
  • the interference removal executing portion 335 compares the absolute value and the set value calculated by the set value calculating portion, and removes a sampling interval of the serial signal of which the absolute value is equal to or greater than the set value. Such a sampling interval of the serial signal having the calculated absolute value equal to or greater than the set value presumably includes interference of a jammer. Thus the part of the serial signal considered as interference is eliminated through an operation of the interference removal executing portion.
  • Removing the part of the serial signal considered as interference that is, removing the sampling interval of the serial signal of which the absolute value calculated is equal to or greater than the set value can be implemented by substituting one of 0, threshold, and noise value for the value of the corresponding sampling interval. Setting the value of the sampling interval to zero 0 may simplify the processing. But the absolute value free from interference is rarely zero 0, so the removed sampling interval may not be the corresponding interval of the original navigation signal.
  • the threshold is the maximum allowable value of the navigation signal. Though relatively insignificant compared to interference, the threshold can also be used to simplify the processing, but the removed sampling interval may differ from the corresponding interval of the original navigation signal, as can be seen in the case of using zero 0.
  • the noise value is a signal value in a state that the navigation signal is mixed with a predictable normal noise when no interference exists.
  • the noise value is variable depending on the position of the antenna or the like.
  • the term “noise value” as used herein refers to the noise value or its average before or after the corresponding interval. Though the process is somewhat complicated to calculate the noise value, the noise value can be used to process the corresponding interval with a signal presumably considered as the corresponding interval of the original navigation signal.
  • FIG. 5 is a block diagram showing an embodiment of the set value calculating portion included in the apparatus for removing interference in a navigation signal of a GNSS system according to the present invention.
  • the set value calculating portion 370 shown in FIG. 5 includes: a bit converting portion 371 for receiving the calculated absolute value from the absolute value calculating portion 331, where the bit converting portion has fewer bits than the bits needed for representing the absolute value of interference; and a set value generating portion 380 for calculating a set value as the median in a frequency distribution of the output of the bit converting portion, or the average of the output of the bit converting portion.
  • the set value calculating portion 370 computes the set value as the average of the absolute value calculated by the absolute value calculating portion, or the median in a frequency distribution of the absolute value.
  • the bit converting portion 371 is employed to prevent these problems.
  • the bit converting portion 371 has fewer bits than the bits needed for representing the absolute value of interference.
  • the input of the bit converting portion is the absolute value of the serial signal computed by the absolute value calculating portion. Accordingly, the bit converting portion limits the absolute value of the interference included in the serial signal.
  • the absolute value is prevented from being used in the computation of the average or the median, thereby improving the reliability of the average and the median calculated.
  • only an 8?bit resource is used instead of a 10-bit or larger resource such as memory, buffer, etc. to represent the absolute value 1000 of the interference, thus enhancing productivity.
  • the bit converting portion can be adopted in this way on the ground that the absolute value of the sampling interval under the influence of interference by a jammer is several to several score times greater than the absolute value of a normal navigation signal. Therefore, it may not affect the normal navigation signal even though the absolute value is partially limited through the converting portion.
  • the number of bits of the bit converting portion is necessarily determined within a range that allows representation of the absolute value of the normal navigation signal.
  • the absolute value of which the number of bits is changed through the bit converting portion is used for the set value generating portion 380 to calculate the average of the absolute value or the median in the frequency distribution of the absolute value.
  • the average or the median thus calculated is used as the set value.
  • the set value generating portion 380 includes: a histogram generating portion 390 for generating a histogram in units of bits allocated according to the respective GNSS modes, where the histogram has the output of the bit converting portion plotted on the horizontal axis and the frequency of the output on the vertical axis; and a median generating portion 381 for calculating the median as the output on the horizontal axis representing half the area of the histogram.
  • the histogram generating portion 390 generates a histogram as depicted in FIG. 6.
  • the generation of a histogram may involve plotting a graph, or storing cumulative values according to the respective absolute values.
  • the median generating portion 381 calculates the median, and more specifically, determines the median as the output on the horizontal axis that represents half the area of the histogram. Half the area of the histogram is computed from the starting point of the horizontal axis in the histogram. Referring to FIG. 6, area a on the left side to the vertical dotted line is equal to area b on the right side, and the median is the value on the horizontal axis at which the horizontal axis intersects the dotted line.
  • the output of the bit converting portion fed into the histogram generating portion is a value obtained by processing a signal in different GNSS modes. It is contrary to the purpose of the median to use a value obtained by processing a signal in a plurality of GNSS modes in creation of the histogram. The reason is that the respective GNSS mode comes in different frequency bands and magnitudes; thus it deteriorates the reliability of the results when additionally using absolute values of other GNSS mode in generating a histogram of a specific GNSS mode.
  • the histogram generating portion generates a histogram in units of bits allocated according to the respective GNSS modes.
  • the unit of bits corresponds to, for example, each interval t1, t2, t3 or t4 in FIG. 3. All the intervals t1, t2, t3 and t4 may have the same unit of bits; thus each interval is, for example, 1024 bits. If the sampling interval is 16 bits as mentioned in regard to the interference removing portion, then the sampling number per interval is 64.
  • the histogram generating portion 390 includes: a scale converting buffer 391 for cumulatively increasing the value stored in an address corresponding to the output of the bit converting portion by 1 each time receiving the output of the bit converting portion; and a cumulative value output portion 393 for sequentially outputting the cumulative value along with the value of the address in order from least significant to most significant address, when the number of outputs of the bit converting portion meets the sampling number for the unit of bits.
  • the median generating portion 381 computes a median as the value of an address corresponding to the last cumulative value when the sum of the cumulative values meets half the sampling number for the unit of bits.
  • the scale converting buffer 391 has an address corresponding to the output of the bit converting portion.
  • the output of the bit converting portion is limited by the number of bits of the bit converting portion. For example, when the size of the bit converting portion is 8 bits, the scale converting buffer has addresses 0 to 255 that can be represented with 8 bits. If the unit of bits is 1024 bits and the sampling interval 16 bits, then the absolute value calculating portion converts 16-bit data representing the characteristics of a navigation signal into an appropriate unit of bits representing the absolute value.
  • the bit converting portion limits the appropriate unit of bits to 8 bits, and the scale converting buffer cumulatively increases by 1 the address value corresponding to the 8?bit output data of the bit converting portion, starting the address value from 0.
  • the output of the bit converting portion is given in the order of 100, 120, 101, 120, 120.
  • This procedure is carried out repeatedly as many times as the sampling number for the unit of bits, completing a histogram. Let the unit of bits be 1024 bits and the sampling interval 16 bits, for example; then the sampling number is 64.
  • the cumulative value output portion 393 sequentially outputs the cumulative values accumulated in the scale converting buffers along with the address values of the scale converting buffers in order from least significant to most significant address, when the number of outputs of the bit converting portion meets the sampling number for the unit of bits.
  • the histogram is considered as completed when the cumulative value output portion outputs the cumulative values in the scale converting buffers as many as the sampling number for the unit of bits.
  • the cumulative value output portion may include a third switching portion that is switched OFF when the number of outputs of the bit converting portion does not meet the sampling number for the unit of bits, and switched ON when the number of outputs of the bit converting portion meets the sampling number for the unit of bits.
  • each switching terminal of the third switching portion is the output terminal of the scale converting buffer and the input terminal of the median generating portion.
  • the median generating portion 381 can sequentially sum up the cumulative values received in order from least significant to most significant address in the complete histogram.
  • the median is computed as an address value corresponding to the last cumulative value when the sum meets half the sampling number for the unit of bits.
  • the case where ‘the sum meets half the sampling number for the unit of bits’ can be described as follows. Let the sampling number for the unit of bits be 64 (supposing that the size of the bit converting portion is 8 bits), for example; then the median is the address value when the sum is 32. The sum may exceed 32.
  • the cumulative values received are 1, 8, 5, 2, 3, 7, 5, 3,... for addresses 80, 90, 101, 106, 108, 110, 111, 120,..., respectively in order from least significant to most significant address.
  • the median generating portion checks on the cumulative value on the first address 80, where the cumulative value '1' does not reach 32; and then adds the cumulative value of '8' on address 90 to 1. The sum does not come to 32 yet again, and the median generating portion sums up the cumulative values, moving towards the most significant address.
  • the sum '34' is not the same as 32 but taken as the first sum value exceeding 32.
  • the set value determined and generated by the set value generating portion 380 as described above can be a set value in different GNSS modes.
  • the set value generating portion needs to manage the set values generated according to the respective GNSS modes in order to compare the set values of the set value generating portion with the absolute values in different GNSS modes.
  • the set value generating portion 380 further includes: a fourth switching portion 383 for performing a switching operation in the predetermined time intervals of the first switching portion to output the median to fifth output terminals provided according to the respective GNSS modes; a set value buffer 385 connected to the respective fifth output terminals to store the received median; a multiplying portion 387 for multiplying the stored median by a predetermined multiplier; and a fifth switching portion 389 for switching the multiplied median in the predetermined time intervals and transferring the median to the interference removal executing portion through a single output.
  • a fourth switching portion 383 for performing a switching operation in the predetermined time intervals of the first switching portion to output the median to fifth output terminals provided according to the respective GNSS modes
  • a set value buffer 385 connected to the respective fifth output terminals to store the received median
  • a multiplying portion 387 for multiplying the stored median by a predetermined multiplier
  • a fifth switching portion 389 for switching the multiplied median in the predetermined time intervals and transferring the median
  • the fourth switching portion 383 performs switching to connect the output of the average value generating portion having a single output terminal to the a plurality of input terminals of the set value buffer provided according to the respective GNSS modes. For this, the fourth switching portion has the fifth terminals as many as the input terminals of the set value buffer.
  • the set value buffer 385 stores the output signal of the median generating portion, that is, median.
  • the medians stored in the set value buffer are discriminated according to the respective GNSS modes, since the fourth switching portion performs switching in the same predetermined time intervals of the first switching portion.
  • the multiplying portion 387 multiplies the median stored in the set value buffer by a predetermined multiplier.
  • Using the median of the median generating portion as a set value that is compared with the absolute value may cause the interference removal executing portion to eliminate a significant number of the absolute values.
  • the median is multiplied by a predetermined multiplier.
  • This multiplication process is carried out on the ground that the navigation signal is susceptible to interference, namely, jamming signal but sturdy enough against prominent signals of a certain magnitude and that interference is several to several score times greater in magnitude than the navigation signal.
  • the multiplier used for the multiplication process may be determined by the respective GNSS modes and given in a defined range according to the respective GNSS modes. For example, the multiplier for the GPS mode may be selected in the range of 3 to 10.
  • the fifth switching portion serializes the medians of the respective set value buffers that are multiplied to match the absolute values.
  • FIG. 7 is a flow chart showing a method for removing interference in a navigation signal of a GNSS system according to the present invention.
  • the method for removing interference in a navigation signal of a GNSS system as illustrated in FIG. 7 can be described by way of the operation of the interference processing portion 300 that is included in the apparatus of FIG. 2 for removing interference in a navigation signal of a GNSS system.
  • the digital IF signals that are transmitted in parallel according to the respectively GNSS modes are switched in predetermined time intervals to generate a serial signal through one of second output terminals, and the serial signal is converted from time domain to frequency domain, in step S810. This operation is carried out by the signal converting portion 310.
  • Interference equal to or greater than a set value is removed from the converted serial signal, in step S820, through the interference removing portion 330.
  • the interference-removed serial signal is inverse-converted from frequency domain to time domain, in step S850, through the signal inverse converting portion 350.
  • the interference removing step S820 may include the following procedures:
  • the absolute values for the respective sampling intervals of the converted serial signal are calculated, in step S821, through the absolute value calculating portion 331. This operation makes it possible to eliminate interference just using the magnitude only.
  • the absolute values are used to calculate the set value, in step S830, through the set value calculating portion 370.
  • the converted serial signal is delayed for a set value calculation time in the step of calculating the set value, in step S825, through the delaying portion 333.
  • the output signal of the set value calculating portion can be synchronized with the serial signal.
  • the absolute value is compared with the calculated set value, and if the absolute value is equal to or greater than the set value, the sampling interval of the delayed serial signal having the absolute value is eliminated, in step S823, through the interference removal executing portion 335.
  • the set value can be determined as the median in a frequency distribution of the absolute value or the average of the absolute value.
  • the set value calculating step S830 includes: a step S831 of converting the absolute value to have fewer bits than the bits for representing the absolute value of the interference; and a step of generating the set value as the median in a frequency distribution of the converted absolute value or the average of the converted absolute value.
  • the bit converting portion 371 performs converts the absolute value, and the set value generating portion 380 generates the set value.
  • the histogram where the converted absolute value is plotted on the horizontal axis, and the frequency of the aconverted bsolute value on the vertical axis, is generated in units of bits allocated according to the respective GNSS modes, in step S840, through the histogram generating portion 390.
  • the absolute value on the horizontal axis representing half the area of the histogram is calculated and generated as the median, in step S833, through the median generating portion 381.
  • the step S840 of generating a histogram includes the following procedures.
  • the value stored in the address of the storing portion corresponding to the converted absolute value is cumulatively increased by 1, in step S841, through the scale converting buffer 391.
  • the cumulative values along with the values of the addresses are sequentially output in order from least significant to most significant address, in step S843, through the cumulative value output portion 393.
  • the median is calculated and generated as the value of an address corresponding to the last input cumulative value when the sum of the cumulative values meets half the unit of bits.
  • the method for removing interference in a navigation signal of a GNSS system according to the present invention as described above may be programmed on a computer-readable record medium.
  • the present invention is applicable to a system for removing jammer interference for the respective GNSS modes.
  • the present invention is preferably applied to a system that works on a plurality of GNSS modes.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Noise Elimination (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

L'invention porte sur un système, un appareil et un procédé d'élimination de brouillage dans un signal de navigation de système mondial de navigation par satellites (GNSS). Le système comprend : un processeur de réception de signal qui est agencé en nombre égal à celui d'une pluralité de modes GNSS et convertissant un signal de navigation reçu en provenance de satellites de navigation par l'intermédiaire d'une antenne en un signal à fréquence intermédiaire (IF) sous forme numérique conformément aux modes GNSS respectifs ; un éliminateur de brouillage pour traiter le signal IF afin de générer un signal série unique par répartition temporelle, éliminer un brouillage du signal série, et distribuer ensuite le signal série conformément aux modes GNSS respectifs ; et un récepteur GNSS pour recevoir et traiter le signal série distribué. Le système contribue à une amélioration de productivité par élimination de brouillage à l'aide d'un seul éliminateur de brouillage indépendamment du nombre de modes GNSS.
PCT/KR2011/009239 2011-01-31 2011-12-01 Système, appareil et procédé d'élimination de brouillage dans un signal de navigation de système mondial de navigation par satellites (gnss) Ceased WO2012105747A1 (fr)

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CN103630910A (zh) * 2013-12-13 2014-03-12 武汉大学 一种gnss接收机设备的抗干扰方法
CN105223590A (zh) * 2015-10-27 2016-01-06 国信军创(岳阳)六九零六科技有限公司 一种混合卫星导航抗干扰方法及装置
CN105549036A (zh) * 2016-01-07 2016-05-04 西安电子科技大学昆山创新研究院 一种导航卫星接收机窄带干扰抑制的算法
FR3111712A1 (fr) * 2020-06-22 2021-12-24 Safran Electronics & Defense Procédé de traitement d’un signal de radionavigation issu d’un satellite
EP4016133A1 (fr) * 2020-11-24 2022-06-22 Honeywell International Inc. Antibrouillage gnss utilisant l'annulation d'interférences
US11982751B2 (en) 2020-11-24 2024-05-14 Honeywell International Inc. GNSS anti-jamming using interference cancellation
CN120455215A (zh) * 2025-07-03 2025-08-08 北京李龚导航科技股份有限公司 一种时域干扰消除方法、装置、电子设备及存储介质

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CN104459723A (zh) * 2014-12-29 2015-03-25 哈尔滨工业大学 一种基于子空间投影的导航接收机欺骗式干扰消除方法
KR101871908B1 (ko) * 2016-12-01 2018-07-03 넵코어스 주식회사 위성 항법 시스템의 재밍 처리 장치 및 재밍 처리 방법
CN108008414A (zh) * 2017-12-29 2018-05-08 扬州宇安电子科技有限公司 一种定向电子干扰处置拦截系统

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CN103630910A (zh) * 2013-12-13 2014-03-12 武汉大学 一种gnss接收机设备的抗干扰方法
CN103630910B (zh) * 2013-12-13 2015-09-02 武汉大学 一种gnss接收机设备的抗干扰方法
CN105223590A (zh) * 2015-10-27 2016-01-06 国信军创(岳阳)六九零六科技有限公司 一种混合卫星导航抗干扰方法及装置
CN105549036A (zh) * 2016-01-07 2016-05-04 西安电子科技大学昆山创新研究院 一种导航卫星接收机窄带干扰抑制的算法
FR3111712A1 (fr) * 2020-06-22 2021-12-24 Safran Electronics & Defense Procédé de traitement d’un signal de radionavigation issu d’un satellite
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EP4016133A1 (fr) * 2020-11-24 2022-06-22 Honeywell International Inc. Antibrouillage gnss utilisant l'annulation d'interférences
US11982751B2 (en) 2020-11-24 2024-05-14 Honeywell International Inc. GNSS anti-jamming using interference cancellation
CN120455215A (zh) * 2025-07-03 2025-08-08 北京李龚导航科技股份有限公司 一种时域干扰消除方法、装置、电子设备及存储介质

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