Positioning device and positioning method

Abstract

A positioning device according to the present invention comprises a spectrum generation unit, a peak level detection unit, and a determination unit. The spectrum generation unit generates a frequency spectrum of a reception signal. The peak level detection unit detects a peak level of a jamming detection target frequency band in the frequency spectrum. The determination unit compares a first jamming signal threshold value with the peak level to determine a first jamming signal of a continuous wave.

Description

Positioning apparatus and positioning method

[0001] The present invention relates to detection of jamming signals.

[0002] Patent Document 1 describes a method of detecting a noise floor level of a received signal, and identifying a channel having a signal level greater than a preset noise floor threshold as a channel having interference.

[0003] Japanese Translation of PCT International Application Publication No. 2011-521258

[0004] However, with the method described in Patent Document 1, it has not been possible to reliably detect jamming signals.

[0005] Accordingly, an object of the present invention is to reliably detect jamming signals.

[0006] A positioning apparatus according to an embodiment of the present invention comprises a spectrum generation unit, a peak level detection unit, and a determination unit. The spectrum generation unit generates a frequency spectrum of a received signal. The peak level detection unit detects a peak level in a jamming detection target frequency band in the frequency spectrum. The determination unit compares a first jamming signal threshold with the peak level to determine a continuous-wave first jamming signal.

[0007] With this configuration, a continuous-wave jamming signal whose signal level is concentrated in a narrow frequency band can be reliably detected.

[0008] A positioning apparatus according to an embodiment of the present invention comprises a spectrum generation unit, a level difference calculation unit, a level difference integration unit, and a determination unit. The spectrum generation unit generates a frequency spectrum of a received signal. The level difference calculation unit calculates a level difference between a spectrum level for each of a plurality of frequency components and a reference level in a jamming detection target frequency band. The level difference integration unit integrates the level differences of the plurality of frequency components. The determination unit compares a second jamming signal threshold with the integrated value of the level differences to determine a frequency-spread or frequency-modulated second jamming signal.

[0009] With this configuration, a frequency-spread or frequency-modulated jamming signal whose signal level spreads over a predetermined frequency band can be reliably detected.

[0010] A positioning device according to one embodiment of this invention comprises a spectrum generation unit, a peak level detection unit, a first determination unit, and an integrated determination unit. The spectrum generation unit generates the frequency spectrum of the received signal. The peak level detection unit detects the peak level of the frequency band targeted for jamming detection in the frequency spectrum. The first determination unit compares the first jamming signal threshold with the peak level to determine the first jamming signal of a continuous wave. The integrated determination unit comprehensively determines whether or not a jamming signal has been received based on the determination result of the first jamming signal and the determination result of the second jamming signal.

[0011] This configuration allows for a comprehensive determination of whether or not a jamming signal has been received, encompassing both continuous wave jamming signals where the signal level is concentrated in a narrow frequency band and spread frequency or frequency-modulated jamming signals where the signal level is spread across a predetermined frequency band.

[0012] Furthermore, in a positioning device according to one embodiment of this invention, the first determination unit sets a first jamming signal threshold based on the noise floor level. The first determination unit updates the first jamming signal threshold based on the noise floor level at each preset update timing.

[0013] In this configuration, the threshold value for the first jamming signal can be appropriately updated according to the reception conditions.

[0014] Furthermore, in a positioning device according to one embodiment of this invention, the second determination unit sets a second jamming signal threshold based on the noise floor of the jamming detection target frequency band. The second determination unit updates the second jamming signal threshold at each preset update timing based on the noise floor level at that update timing.

[0015] In this configuration, the threshold value for the first jamming signal can be appropriately updated according to the reception conditions.

[0016] Furthermore, in a positioning device according to one embodiment of this invention, the second determination unit calculates the level difference between the noise floor level of the jamming detection target frequency band at the update timing and the noise floor level to which the already set second jamming signal threshold is set. Based on the level difference, the second determination unit decides whether or not to update the second jamming signal threshold.

[0017] In this configuration, the threshold for the second jamming signal can be appropriately updated when necessary, based on changes in the noise floor level.

[0018] Furthermore, in a positioning device according to one embodiment of this invention, the second determination unit determines whether or not to update the second jamming signal threshold based on whether or not the navigation message of the received signal has been acquired.

[0019] In this configuration, the second jamming signal threshold is updated when navigation messages are received, i.e., when positioning signals are received successfully. This allows the second jamming signal threshold to be updated when it is appropriate.

[0020] Furthermore, in a positioning device according to one embodiment of this invention, the second determination unit sets a second jamming signal threshold for each frequency band of the positioning signal.

[0021] In this configuration, it is possible to determine whether or not a jamming signal has been received for each type of positioning signal.

[0022] Furthermore, in a positioning device according to one embodiment of this invention, the second determination unit sets a lower threshold value for the cumulative value, and the second determination unit compares the cumulative value with the lower threshold value to determine a reception abnormality.

[0023] This configuration allows for more reliable detection of reception anomalies in positioning signals, as well as anomalies in the antenna connection system and RF.

[0024] Furthermore, in a positioning device according to one embodiment of this invention, the spectrum generation unit generates a frequency spectrum at the time of initial positioning. The second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning. The second determination unit compares the reference level with a preset upper threshold value and determines the possibility of a second jamming signal.

[0025] In this configuration, the possibility of receiving a second jamming signal can be determined based on the level of the frequency spectrum during initial positioning.

[0026] Furthermore, in a positioning device according to one embodiment of this invention, the spectrum generation unit generates the frequency spectrum at the time of initial positioning. The second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning. The second determination unit compares the reference level with a preset lower threshold and determines the possibility of reception abnormality.

[0027] In this configuration, the possibility of reception anomalies can be determined based on the frequency spectrum level during initial positioning.

[0028] Furthermore, in a positioning device according to one embodiment of this invention, the determination unit includes a noise floor setting unit that sets the noise floor level used for setting the threshold for the second jamming signal. The noise floor setting unit sets the noise floor level based on temperature.

[0029] In this configuration, a second jamming signal threshold is set according to the temperature of the positioning device. Therefore, the accuracy of determining the second jamming signal is improved.

[0030] Furthermore, a positioning device according to one embodiment of this invention includes a positioning calculation unit that performs positioning calculations using the positioning signal in the received signal.

[0031] In this configuration, positioning calculations can be performed using a legitimate positioning signal that is not affected by jamming signals, resulting in higher positioning accuracy.

[0032] Furthermore, a positioning device according to one embodiment of this invention includes a reference signal generation unit that generates a reference frequency signal or a timing signal using the positioning signal in the received signal.

[0033] In this configuration, a reference frequency signal or timing signal can be generated using a regular positioning signal that is not affected by jamming signals, thereby improving the timing accuracy of the signal.

[0034] Figure 1 is a functional block diagram showing an example of the configuration of a positioning device according to an embodiment of the present invention. Figure 2 is a functional block diagram showing a configuration for realizing a first example of spoofing signal detection processing. Figure 3 is a flowchart showing a first example of processing to detect a spoofing signal using pseudo-distance. Figure 4 is a table showing an example of the correction residual of a received signal including a spoofing signal and a normal positioning signal. Figure 5 is a flowchart showing a second example of processing to detect a spoofing signal using pseudo-distance. Figure 6 is a flowchart showing a first example of processing to detect a spoofing signal using Doppler frequency. Figure 7 is a functional block diagram showing a configuration for realizing a second example of spoofing signal detection processing. Figure 8 is a flowchart showing an example of processing to detect a spoofing signal using pseudo-distance and signal level. Figure 9 is a functional block diagram showing a configuration for realizing a third example of spoofing signal detection processing. Figure 10 is a flowchart showing an example of processing to detect a spoofing signal using pseudo-distance and a clock bias calculated in initial positioning. Figure 11 is a functional block diagram showing a configuration for realizing a first example of setting and canceling spoofing alert mode. Figure 12 is a flowchart showing an example of the process for starting the spoofing alert mode. Figure 13 is a flowchart showing the first example of the process for deactivating the spoofing alert mode. Figure 14 is a flowchart showing the second example of the process for deactivating the spoofing alert mode. Figure 15 is a flowchart showing the third example of the process for deactivating the spoofing alert mode. Figure 16 is a flowchart showing the fourth example of the process for deactivating the spoofing alert mode. Figure 17 is a flowchart showing the fifth example of the process for deactivating the spoofing alert mode. Figure 18 is a flowchart showing the sixth example of the process for deactivating the spoofing alert mode. Figure 19 is a functional block diagram showing the configuration for realizing the first example of the NMA authentication setting and notification process. Figure 20 is a table showing the types of authentication statuses and the contents of each status. Figures 21(A), 21(B), and 21(C) are diagrams showing specific examples of the NMA authentication process. Figure 22 is a flowchart showing the first example of the process for setting the NMA authentication status to the unauthenticated state.Figures 23(A) and 23(B) are diagrams showing an example of the state transition of the authentication status corresponding to Figure 22. Figure 24 is a flowchart showing a second example of the process of setting the NMA authentication status to an unauthenticated state. Figures 25(A) and 25(B) are diagrams showing an example of the state transition of the authentication status corresponding to Figure 24. Figure 26 is a flowchart showing the process when NMA authentication cannot be performed within the threshold time. Figure 27 is a flowchart showing the process when NMA authentication cannot be updated within the threshold time. Figure 28 is a functional block diagram showing an example of the configuration of the jamming detection unit according to an embodiment of the present invention. Figure 29 is a diagram showing the determination concept of the first jamming signal. Figure 30 is a flowchart showing an example of the determination process of the first jamming signal. Figure 31 is a flowchart showing an example of the update process of the threshold for the first jamming signal. Figures 32(A) and 32(B) are diagrams showing the determination concept of the second jamming signal. Figure 33 is a flowchart showing a first example of the determination process of the second jamming signal. Figure 34 is a flowchart showing a second example of the determination process of the second jamming signal. Figure 35 is a flowchart showing a third example of the second jamming signal determination process. Figure 36 is a flowchart showing a first example of the reference level update process for the second jamming signal. Figure 37 is a flowchart showing a second example of the reference level update process for the second jamming signal. Figure 38 is a functional block diagram showing an example of the configuration of a jamming determination unit equipped with a temperature compensation function for the noise floor level. Figure 39 is a flowchart showing an example of the setting process for the first temperature-sensitive noise floor level. Figure 40 is a flowchart showing an example of the setting process for the second temperature-sensitive noise floor level.

[0035] A positioning device and positioning method according to an embodiment of the present invention will be described with reference to the figures. Figure 1 is a functional block diagram showing an example of the configuration of a positioning device according to an embodiment of the present invention.

[0036] (Configuration of positioning device 10) As shown in Figure 1, the positioning device 10 includes a signal processing unit 20 and an antenna ANT. The signal processing unit 20 includes an input stage processing unit 201, a capture and tracking unit 21, a positioning signal observation unit 22, a demodulation unit 23, an authentication unit 24, a spoofing detection unit 30, a jamming detection unit 41, a warning mode setting unit 42, a reception state detection unit 50, a positioning calculation unit 60, a reference signal generation unit 70, an authentication state setting unit 80, and an output unit 90. The positioning device 10 is configured using a program for executing the following processes, a storage medium for storing the program, and an arithmetic processing unit such as a CPU for executing the program. An antenna ANT is connected to the signal processing unit 20.

[0037] The positioning device 10 is used for positioning using GNSS (Global Navigation Satellite System) and for generating a reference frequency signal. GNSS is a system that uses positioning signals broadcast from positioning satellites to perform positioning and generate a reference frequency signal, and examples include GPS, QZSS, Galileo, GLONASS, and BeiDou.

[0038] The antenna (ANT) receives positioning signals from multiple positioning satellites. These positioning signals are composed of different specifications depending on the type of positioning system (e.g., GPS, QZSS, Galileo, GLONASS, BeiDou, etc.). The specifications of the positioning signals for each system are known, and a detailed explanation is omitted here.

[0039] Basically, positioning signals are constructed by spreading a carrier signal of a predetermined frequency using a spreading code unique to the positioning satellite. Furthermore, navigation messages specific to each positioning satellite (e.g., ephemeris information, almanac information) are superimposed on the positioning signal.

[0040] Furthermore, NMA (Navigation Message Authentication) data is superimposed on the positioning signals of certain positioning systems. For example, NMA data is superimposed on the positioning signals of QZSS and Galileo, while it is not superimposed on the positioning signals of other positioning systems.

[0041] Here, if a spoofing signal or jamming signal exists, antenna ANT also receives the spoofing signal or jamming signal.

[0042] Antenna ANT outputs a received signal (hereinafter referred to as the received signal) to input stage processing section 201 of signal processing section 20.

[0043] Input stage processing section 201 performs signal processing such as filtering processing and gain adjustment on the received signal. Input stage processing section 201 outputs the received signal after signal processing to acquisition and tracking section 21, jamming detection section 41, and reception state detection section 50.

[0044] Acquisition and tracking section 21 acquires and tracks the received signal. Acquisition and tracking section 21 outputs the code phase and carrier phase obtained through acquisition and tracking to positioning signal observation section 22.

[0045] Positioning signal observation section 22 calculates a pseudo range (code pseudo range) ρ based on the code phase. Positioning signal observation section 22 calculates Doppler frequency Δf based on the carrier phase. Positioning signal observation section 22 outputs the pseudo range ρ and Doppler frequency Δf to spoofing detection section 30 and positioning calculation section 60.

[0046] Demodulation section 23 demodulates a navigation message based on the waveform of the received signal tracked by acquisition and tracking section 21. Demodulation section 23 outputs the demodulated navigation message to authentication section 24 and positioning calculation section 60.

[0047] Demodulation section 23 demodulates NMA data based on the waveform of the received signal tracked by acquisition and tracking section 21. Demodulation section 23 outputs the NMA data to authentication section 24.

[0048] Authentication section 24 performs NMA authentication on the received signal based on the navigation message and the NMA data. Authentication section 24 outputs the NMA authentication result to spoofing detection section 30 and authentication state setting section 80.

[0049] The spoofing detection unit 30 uses the NMA authentication result, pseudo-distance ρ, and Doppler frequency Δf to detect whether the received signal is a spoofing signal. A specific example of the spoofing signal detection process in the spoofing detection unit 30 will be described later. The spoofing detection unit 30 outputs the spoofing signal detection result to the positioning calculation unit 60.

[0050] The jamming detection unit 41 detects the presence or absence of a jamming signal using the signal level of the received signal, etc. A specific example of the jamming signal detection process in the jamming detection unit 41 will be described later. The jamming detection unit 41 outputs the jamming detection result to the alert mode setting unit 42.

[0051] The alert mode setting unit 42 sets the spoofing alert mode based on the jamming detection result. A specific example of the processing of the alert mode setting unit 42 will be described later. The alert mode setting unit 42 outputs the set spoofing alert mode to the demodulation unit 23 and the positioning calculation unit 60.

[0052] The reception state detection unit 50 detects the reception state based on the signal level of the received signal. Specifically, the reception state detection unit 50 detects the signal level of the received signal. The reception state detection unit 50 has a state detection threshold set in advance. The state detection threshold is set, for example, based on the signal level at which each positioning signal in the received signal can no longer be demodulated. If the signal level of the received signal is lower than the state detection threshold, the reception state detection unit 50 detects that the reception state has deteriorated. On the other hand, if the signal level of the received signal is equal to or greater than the state detection threshold, the reception state detection unit 50 detects that the reception state has not deteriorated (the reception state is good). The reception state detection unit 50 outputs the reception state detection result to the authentication state setting unit 80.

[0053] The positioning calculation unit 60 positions the positioning device 10 based on at least one of the pseudo-distance ρ and the Doppler frequency Δf. For example, the positioning calculation unit 60 uses at least the pseudo-distance ρ when calculating position and at least the Doppler frequency Δf when calculating velocity.

[0054] The positioning calculation unit 60 performs positioning based on the detection result of the spoofing signal. Specifically, when the positioning calculation unit 60 detects a spoofing signal, it excludes the spoofing signal and the information obtained from the spoofing signal in the received signal from the positioning calculation and performs positioning using the remaining regular positioning signal. If no spoofing signal is detected, the positioning calculation unit 60 performs positioning using the received signal (regular positioning signal).

[0055] Furthermore, the positioning calculation unit 60 also calculates the clock bias of the positioning device 10 during the positioning calculation.

[0056] The reference signal generation unit 70 generates a reference frequency signal, timing signal, etc., that are highly synchronized with the GNSS time, based on the clock bias calculated by the positioning calculation unit 60.

[0057] The authentication status setting unit 80 sets the authentication status of NMA authentication based on the NMA authentication result from the authentication unit 24, the reception status detection result from the reception status detection unit 50, etc. A specific example of the processing of the authentication status setting unit 80 will be described later.

[0058] The output unit 90 consists of an interface for external connection. The output unit 90 outputs the positioning calculation result, reference frequency signal, timing signal, and NMA authentication status to an external device.

[0059] The positioning device 10 may also include a notification unit. The notification unit consists of, for example, a display, a speaker, etc. The notification unit notifies the positioning calculation result, time information, and NMA authentication status.

[0060] (Spoofing Signal Detection 1) Figure 2 is a functional block diagram showing the configuration for realizing a first example of spoofing signal detection processing. As shown in Figure 2, the spoofing detection unit 30 includes a residual calculation unit 31, a residual difference calculation unit 32, and a determination unit 33. The residual calculation unit 31 corresponds to the "comparison value calculation unit," and the residual difference calculation unit 32 corresponds to the "comparison value difference calculation unit."

[0061] The residual calculation unit 31 calculates the residual between the observed value and the calculated value based on the NMA-certified positioning signal (reference residual), and the residual between the observed value and the calculated value based on the received signal that is the target of detection of the spoofing signal (comparison residual).

[0062] The residual difference calculation unit 32 calculates the difference (residual difference) between the reference residual and the comparison residual.

[0063] The determination unit 33 has pre-set threshold values ​​for detecting spoofing signals.

[0064] The determination unit 33 determines that the received signal corresponding to the comparison residual is a spoofing signal if the absolute value of the residual difference is greater than the threshold for spoofing detection.

[0065] The determination unit 33 determines that if the absolute value of the residual difference is less than or equal to the threshold for detecting spoofing, the received signal corresponding to the residual being compared is not a spoofing signal. In other words, if the absolute value of the residual difference is less than or equal to the threshold for detecting spoofing, the determination unit 33 determines that the received signal corresponding to the residual being compared is a legitimate positioning signal.

[0066] (Spoofing signal detection process 1 using pseudo-distance ρ) Figure 3 is a flowchart showing the first example of a process for detecting a spoofing signal using pseudo-distance.

[0067] The acquisition and tracking unit 21 acquires and tracks the received signal (S101). The demodulation unit 23 determines whether the received signal is subject to NMA authentication (S102). Whether or not it is subject to NMA authentication can be identified, for example, by the positioning system to which the positioning signal belongs. Since it is known which positioning signal the tracked received signal corresponds to at the time the received signal is acquired and tracked, it is possible to identify whether or not each received signal is subject to NMA authentication.

[0068] The demodulation unit 23 demodulates the navigation message and NMA data (S103) if the received signal is subject to NMA authentication (S102: YES). If the NMA data cannot be demodulated, the received signal is not used as a positioning signal for the spoofing determination criteria.

[0069] The authentication unit 24 performs NMA authentication using the navigation message and NMA data (S104). If NMA authentication is not possible, the received signal is not used as a positioning signal for the spoofing determination criteria.

[0070] The residual calculation unit 31 obtains the position coordinates of the positioning satellite from the navigation message of the NMA-certified positioning signal. The residual calculation unit 31 calculates the geometric distance (reference geometric distance) between the current position of the device and the position of the positioning satellite. If the positioning device 10 is a fixed station (fixed position coordinates), the current position of the device uses these fixed position coordinates. If the user knows, the position can be set by operation input, or even when performing positioning calculations, it only needs to be done once because there is no change in position. On the other hand, if the positioning device 10 is a mobile station (variable position coordinates), the current position of the device can use the position coordinates that were determined immediately before using a regular positioning signal.

[0071] The residual calculation unit 31 calculates the residual (reference pseudo-distance residual) between the pseudo-distance ρ observed by the positioning signal observation unit 22 and the calculated reference geometric distance (S105).

[0072] If the received signal is not subject to NMA authentication (S102: NO), the demodulation unit 23 demodulates the navigation message (S106).

[0073] The residual calculation unit 31 obtains the position coordinates of the positioning satellite from the navigation message demodulated in step S106. The residual calculation unit 31 calculates the current position of the device, the position of the positioning satellite, and the geometric distance (geometric distance to be determined).

[0074] The residual calculation unit 31 calculates the residual between the pseudo-distance ρ observed by the positioning signal observation unit 22 and the geometric distance to be determined (determined pseudo-distance residual) (S107).

[0075] The residual difference calculation unit 32 corrects the pseudo-distance residual to be judged based on the reference pseudo-distance residual (S108). More specifically, the residual difference calculation unit 32 corrects the pseudo-distance residual to be judged by setting the reference pseudo-distance residual to 0.

[0076] If the positioning signal being evaluated is a legitimate positioning signal, the pseudo-distance residual of the evaluated signal will be approximately the same as the reference pseudo-distance residual. On the other hand, if the positioning signal being evaluated is a spoofing signal, the pseudo-distance residual of the evaluated signal will be a value that is significantly different from the reference pseudo-distance residual.

[0077] Figure 4 is a table showing an example of the correction residuals of a received signal containing a spoofing signal and a legitimate positioning signal. LPRc corresponds to the correction residual. In Figure 4, SVID 19GAL is an NMA-certified positioning signal. As shown in Figure 4, SVID 32GPS and SVID 14GPS have correction residuals that are far from zero. Such received signals are spoofing signals, not legitimate positioning signals.

[0078] On the other hand, for example, SVID 3GAL and SVID 2GPS have correction residuals that are not far from zero. Such received signals are legitimate positioning signals.

[0079] Therefore, it is possible to determine whether or not a signal is spoofing using the corrected pseudo-distance residual (corrected residual) of the target of the determination.

[0080] The determination unit 33 stores in advance the detection threshold for spoofing signals. If the correction residual is greater than the detection threshold for spoofing signals (S109: YES), the determination unit 33 determines that the received signal used to calculate the correction residual is a spoofing signal (S110). If the correction residual is less than or equal to the detection threshold for spoofing signals (S109: NO), the determination unit 33 determines that the received signal used to calculate the correction residual is not a spoofing signal (S111).

[0081] By performing this process, the spoofing detection unit 30 can detect a spoofing signal. In this case, the spoofing detection unit 30 uses a pseudo-distance obtained by a simpler calculation, rather than using PVT values ​​obtained by multiple positioning measurements performed with different satellite combinations. As a result, the positioning device 10 can reduce the computational load required to detect the spoofing signal.

[0082] Furthermore, by using pseudo-distance, the positioning device 10 can detect a spoofing signal by using only the received signal targeted for detection and the NMA-certified positioning signal. In other words, while using PVT values ​​requires at least four NMA-certified positioning signals, the positioning device 10 can detect a spoofing signal by using only one NMA-certified positioning signal, by preparing location information in advance and using only pseudo-distance separately for determination.

[0083] Furthermore, the positioning device 10 can detect spoofing signals before initial positioning by using pseudo-distance. As a result, for example, the positioning device 10 can exclude spoofing signals from the initial positioning stage and perform positioning using only highly reliable positioning signals (regular positioning signals).

[0084] Furthermore, by using a corrected residual that sets the reference pseudo-distance residual to zero, it becomes easier to set the detection threshold.

[0085] (Spoofing signal detection process 2 using pseudo-distance ρ) Figure 5 is a flowchart of a second example of a process for detecting a spoofing signal using pseudo-distance. The flowchart in Figure 5 is the same as the flowchart in Figure 3 up to the calculation of the reference pseudo-distance residual and the calculation of the judgment pseudo-distance residual, so the explanation of the similar parts will be omitted.

[0086] The residual difference calculation unit 32 calculates the difference (residual difference) between the reference pseudo-distance residual and the pseudo-distance residual to be judged (S108A).

[0087] If the positioning signal being evaluated is a legitimate positioning signal, the pseudo-distance residual of the signal being evaluated will be approximately the same as the reference pseudo-distance residual, and the residual difference will approach zero. On the other hand, if the positioning signal being evaluated is a spoofing signal, the pseudo-distance residual of the signal being evaluated will be a value that is significantly different from the reference pseudo-distance residual, and the absolute value of the residual difference will be a large value. Therefore, it is possible to determine whether or not a signal is a spoofing signal using the residual difference.

[0088] The determination unit 33 stores a detection threshold for spoofing signals in advance. If the absolute value of the residual difference is greater than the detection threshold for spoofing signals (S109A: YES), the determination unit 33 determines that the received signal used to calculate the residual difference is a spoofing signal (S110A). If the absolute value of the residual difference is less than or equal to the detection threshold for spoofing signals (S109A: NO), the determination unit 33 determines that the received signal used to calculate the residual difference is not a spoofing signal (S111A).

[0089] (Detection of spoofing signals using Doppler frequency Δf) Figure 6 is a flowchart of the first example of a process for detecting spoofing signals using the Doppler frequency. The flowchart in Figure 6 is the same as the flowchart in Figure 3 up to the demodulation of the navigation message and NMA data, and the calculation of NMA authentication, so the explanation of the similar parts will be omitted.

[0090] The residual calculation unit 31 obtains the position coordinates of the positioning satellite at multiple time points from the navigation message of the NMA-certified positioning signal. The residual calculation unit 31 calculates the Doppler frequency (reference Doppler frequency) of the NMA-certified positioning signal based on the change in the geometric distance between the current position of the device and the position of the positioning satellite.

[0091] The residual calculation unit 31 calculates the residual (reference Doppler frequency residual) between the Doppler frequency Δf observed by the positioning signal observation unit 22 and the calculated reference Doppler frequency (S105B).

[0092] The residual calculation unit 31 obtains the position coordinates of the positioning satellite at multiple time points from the navigation message demodulated in step S106B using the positioning signal to be detected as a spoofing signal. The residual calculation unit 31 calculates the (Doppler frequency to be determined) based on the change in the geometric distance between the current position of the device and the position of the positioning satellite.

[0093] The residual calculation unit 31 calculates the residual between the Doppler frequency Δf observed by the positioning signal observation unit 22 and the Doppler frequency to be determined (residual of the Doppler frequency to be determined) (S107B).

[0094] The residual difference calculation unit 32 corrects the Doppler frequency residual to be judged based on the reference Doppler frequency residual (S108B). More specifically, the residual difference calculation unit 32 corrects the Doppler frequency residual to be judged by setting the reference Doppler frequency residual to 0.

[0095] If the positioning signal being evaluated is a legitimate positioning signal, the Doppler frequency residual of the evaluated signal will be approximately the same as the reference Doppler frequency residual. On the other hand, if the positioning signal being evaluated is a spoofing signal, the Doppler frequency residual of the evaluated signal will be a value that is significantly different from the reference Doppler frequency residual.

[0096] Therefore, it is possible to determine whether or not a signal is spoofing using the corrected Doppler frequency residual (corrected residual).

[0097] The determination unit 33 stores in advance the detection threshold for spoofing signals. If the correction residual is greater than the detection threshold for spoofing signals (S109B: YES), the determination unit 33 determines that the received signal used to calculate the correction residual is a spoofing signal (S110B). If the correction residual is less than or equal to the detection threshold for spoofing signals (S109B: NO), the determination unit 33 determines that the received signal used to calculate the correction residual is not a spoofing signal (S111B).

[0098] By performing this process, the spoofing detection unit 30 can detect a spoofing signal. In this case, the spoofing detection unit 30 uses a pseudo-distance obtained by a simpler calculation, rather than using the PVT value obtained by positioning. As a result, the positioning device 10 can reduce the computational load required to detect the spoofing signal.

[0099] Furthermore, by using the Doppler frequency, the positioning device 10 can detect spoofing signals by using only the received signal that is the target of detection and the NMA-certified positioning signal.

[0100] Furthermore, the positioning device 10 can detect spoofing signals before initial positioning by using Doppler frequencies. This allows the positioning device 10 to exclude spoofing signals from the initial positioning stage and perform positioning using only highly reliable positioning signals (regular positioning signals).

[0101] Furthermore, the positioning device 10 can also detect a spoofing signal using the absolute value of the difference (residual difference) between the Doppler frequency residual to be judged and the reference Doppler frequency residual, similar to the process shown in Figure 5.

[0102] (Spoofing Signal Detection 2) Figure 7 is a functional block diagram showing the configuration for realizing a second example of spoofing signal detection processing. Figure 8 is a flowchart showing an example of processing for detecting a spoofing signal using pseudo-distance and signal level.

[0103] As shown in Figure 7, the spoofing detection unit 30A differs from the spoofing detection unit 30 shown in Figure 2 in that it includes a signal level detection unit 34 and a target signal selection unit 35. Below, the differences between the spoofing detection unit 30A and the spoofing detection unit 30 will be specifically explained using Figures 7 and 8, while explanations of similar parts will be omitted.

[0104] The signal level detection unit 34 detects the signal level of the captured and tracked received signal (S121).

[0105] The target signal selection unit 35 selects received signals to be detected as spoofing signals based on their signal levels. Specifically, the target signal selection unit 35 has pre-set selection thresholds. If the signal level is below the selection threshold (S122: YES), the target signal selection unit 35 excludes received signals with this signal level from being detected as spoofing signals (S123).

[0106] If the target signal selection unit 35 finds that the signal level is equal to or greater than the selection threshold (S122: NO), it performs the above-mentioned processing, such as demodulating the navigation message and demodulating the NMA data.

[0107] In this way, by excluding signals with low signal levels from the detection target for spoofing signals, the spoofing detection unit 30A can suppress the false detection of multipath signals and the like as spoofing signals.

[0108] Furthermore, this configuration and processing can be applied not only when using pseudo-distance but also when using Doppler frequency.

[0109] (Detection of Spoofing Signal 3) Figure 9 is a functional block diagram showing the configuration for realizing a third example of the spoofing signal detection process. Figure 10 is a flowchart showing an example of the process of detecting a spoofing signal using the pseudo-distance and the clock bias calculated by initial positioning. In the following, the differences between the spoofing detection unit 30B and the spoofing detection unit 30 will be specifically explained using Figures 9 and 10, and explanations of similar parts will be omitted.

[0110] The acquisition and tracking unit 21 acquires and tracks the received signal (S101). The demodulation unit 23 selects from the tracked received signal a received signal (positioning signal) on which to broadcast (superimpose) NMA data (S131).

[0111] The demodulation unit 23 demodulates the navigation message and NMA data from the selected positioning signal (S103). The authentication unit 24 performs NMA authentication using the demodulated navigation message and NMA data (S104).

[0112] The positioning calculation unit 60 performs initial positioning including positioning signals from NMA-certified positioning satellites (certified satellites) (S132). In initial positioning, the positioning calculation unit 60 calculates the clock bias of the positioning device 10 (S133).

[0113] The positioning signal observation unit 22 performs clock bias correction and recalculates the pseudo-distance ρ. The residual calculation unit 31 calculates the residual between the recalculated pseudo-distance ρ and the above-mentioned reference pseudo-distance (reference pseudo-distance residual) (S105C).

[0114] The determination unit 33B stores a threshold for determining clock bias abnormalities. If the reference pseudo-distance residual is greater than the threshold for determining clock bias abnormalities (S134: YES), the determination unit 33B determines that the clock bias calculated in the initial positioning was abnormal (S135).

[0115] The clock bias is a common factor for all received signals used in initial positioning. Furthermore, NMA-certified positioning signals can be determined not to be spoofing signals. Therefore, if the clock bias calculated during initial positioning is abnormal, there is a very high probability that spoofing signals are present in received signals other than the NMA-certified positioning signals used in initial positioning.

[0116] Using this concept, when the determination unit 33B detects a clock bias anomaly, it determines that the unauthenticated received signals other than the NMA-authenticated positioning signal used in the initial positioning contain a spoofing signal (S136).

[0117] On the other hand, if the reference pseudo-distance residual is less than or equal to the threshold for determining a clock bias anomaly (S134: NO), the determination unit 33B determines that the unauthenticated received signal used for initial positioning does not contain a spoofing signal (S137).

[0118] With this configuration and processing, the positioning device 10 can detect the spoofing signal.

[0119] Furthermore, if it is determined that the unauthenticated received signal used for initial positioning contains a spoofing signal, the spoofing signal can be further identified through the various other processes described above.

[0120] Furthermore, this configuration and processing can be applied not only when using pseudo-distance but also when using Doppler frequency.

[0121] Furthermore, the above-described process illustrates a configuration using one NMA-certified positioning signal. However, it is also possible to use multiple NMA-certified positioning signals. By using multiple NMA-certified positioning signals, the positioning device 10 can improve the detection accuracy of spoofing signals.

[0122] Furthermore, by being able to detect spoofing signals as described above, the positioning device 10 can suppress the adverse effects of spoofing signals on positioning. As a result, the positioning device 10 can achieve more accurate positioning. And by achieving more accurate positioning, the positioning device 10 can generate reference frequency signals and timing signals with high accuracy.

[0123] As described above, spoofing signals can have adverse effects if received and used by the positioning device 10. Therefore, setting a spoofing alert mode to prevent the use of spoofing signals is effective for stable positioning, reference frequency signal generation, and timing signal generation. Accordingly, the setting and deactivation of the spoofing alert mode will be explained next.

[0124] When the received signal is being tracked stably, the frequency bandwidth that changes during tracking by the acquisition and tracking unit 21 is narrow. On the other hand, if tracking is interrupted due to the reception of a jamming signal, the acquisition and tracking unit 21 sets a wider frequency bandwidth for reacquiring the received signal. This makes it easier to receive spoofing signals.

[0125] Therefore, when the positioning device 10 detects a jamming signal, it can suppress the effects of the spoofing signal by setting a spoofing alert mode for a predetermined frequency band that includes the jamming signal.

[0126] On the other hand, the positioning device 10 can prevent a shortage or reduction in the information and positioning signals used for positioning by not setting a spoofing alert mode for frequency bands where jamming signals are not detected. As a result, the positioning device 10 can suppress the adverse effects of spoofing signals on positioning while suppressing interruptions to positioning and deterioration of positioning accuracy. And by suppressing the deterioration of positioning accuracy, it can suppress the deterioration of the accuracy of the reference frequency signal and timing signal.

[0127] Figure 11 is a functional block diagram showing a configuration for realizing a first example of the setting and cancellation process of the spoofing alert mode. As shown in Figure 11, in the setting and cancellation process of the spoofing alert mode, the positioning device 10 includes at least a demodulation unit 23, an authentication unit 24, a spoofing detection unit 30, a jamming detection unit 41, an alert mode setting unit 42, and a positioning calculation unit 60.

[0128] (Setting up spoofing alert mode) Figure 12 is a flowchart showing an example of the process for starting spoofing alert mode.

[0129] The jamming detection unit 41 detects whether or not a jamming signal is included in the received signal (S201). In this case, the jamming detection unit 41 detects whether or not a jamming signal is included in each frequency band including the carrier frequency of each GNSS system.

[0130] The jamming detection unit 41 outputs the jamming signal detection result to the alert mode setting unit 42.

[0131] If a jamming signal is detected (S202: YES), the alarm mode setting unit 42 sets the spoofing alarm mode (S203). In this case, the alarm mode setting unit 42 sets the spoofing alarm mode for each frequency band in which the jamming signal is detected. For example, if the alarm mode setting unit 42 detects a jamming signal in the GPS L1 frequency band but does not detect a jamming signal in the L5 frequency band, it sets the spoofing alarm mode for the L1 frequency band and does not set the spoofing alarm mode for the L5 frequency band.

[0132] The alert mode setting unit 42 notifies the demodulation unit 23 and the positioning calculation unit 60 of the spoofing alert mode.

[0133] The demodulation unit 23 does not acquire information related to time acquisition and correction of the positioning device 10 (parameters such as TOW information, GGTO, and UTC parameters) from the received signal in the frequency band where the spoofing alert mode is set. Furthermore, the demodulation unit 23 does not acquire orbital information and health information (almanac) from the received signal in the said frequency band. In this case, the demodulation unit 23 continues to acquire ephemeris and NMA data from the received signal in the said frequency band.

[0134] The positioning calculation unit 60 does not use received signals in the frequency band where the spoofing alert mode is set for positioning calculations.

[0135] Meanwhile, the demodulation unit 23 acquires navigation messages from received signals in frequency bands where the spoofing warning mode is not set. The positioning calculation unit 60 sets the received signals in frequency bands where the spoofing warning mode is not set as candidates for positioning signals to be used in positioning calculations. At this time, the positioning calculation unit 60, for example, based on the spoofing signal detection result described above, determines from the candidates for positioning signals that the positioning signal is not a spoofing signal and uses the detected positioning signal for positioning calculations.

[0136] (Deactivating Spoofing Alert Mode) As described above, when spoofing alert mode is set, the number of received signals available for positioning decreases. Therefore, the alert mode setting unit 42 deactivates spoofing alert mode by performing the following processes. When the alert mode setting unit 42 notifies that spoofing alert mode has been deactivated, the demodulation unit 23 resumes acquiring information related to time acquisition and correction of the positioning device 10, as well as orbital information and health information. The positioning calculation unit 60 sets the received signals in the frequency band from which spoofing alert mode has been deactivated as candidates for positioning signals to be used in positioning calculations.

[0137] As a result, the positioning device 10 can suppress the undesirable decrease in the positioning signal used for positioning over a long period of time. Therefore, the positioning device 10 can continuously perform stable and highly accurate positioning. Furthermore, the positioning device 10 can maintain the accuracy of the reference frequency signal and timing signal.

[0138] (Spoofing Alert Mode Deactivation 1) Figure 13 is a flowchart showing the first example of the process for deactivating the spoofing alert mode.

[0139] While the spoofing warning mode is being set (S210), the demodulation unit 23 attempts to demodulate the navigation message of the received signal in the frequency band where the spoofing warning mode is set and to acquire the ephemeris.

[0140] If the demodulation unit 23 cannot acquire ephemeris (S211: NO), it outputs a result indicating that ephemeris could not be acquired to the alert mode setting unit 42. The alert mode setting unit 42 continues the spoofing alert mode.

[0141] The demodulation unit 23 can acquire ephemeris (S212: YES), but if it cannot acquire NMA data (S212: NO), it outputs a result indicating that NMA data could not be acquired to the alert mode setting unit 42. The alert mode setting unit 42 continues the spoofing alert mode.

[0142] The demodulation unit 23 can acquire ephemeris (S212: YES) and NMA data (S212: YES), but if NMA authentication is not possible (S213: NO), it outputs a result to the alarm mode setting unit 42 indicating that NMA authentication is not possible. The alarm mode setting unit 42 continues the spoofing alarm mode.

[0143] The demodulation unit 23 can acquire ephemeris (S212: YES), acquire NMA data (S212: YES), and if NMA authentication is performed (S213: YES), it will deactivate the spoofing alert mode for this NMA-authenticated positioning signal (S214).

[0144] (Spoofing Alert Mode Deactivation 2) Figure 14 is a flowchart showing a second example of the spoofing alert mode deactivation process.

[0145] While the spoofing warning mode is being set (S210), the demodulation unit 23 attempts to demodulate the navigation message of the received signal in the frequency band where the spoofing warning mode is set and to acquire the ephemeris.

[0146] If the demodulation unit 23 cannot acquire ephemeris (S221: NO), it outputs a result indicating that ephemeris could not be acquired to the alert mode setting unit 42. The alert mode setting unit 42 continues the spoofing alert mode.

[0147] If the demodulation unit 23 can acquire ephemeris (S221: YES), it outputs the acquired ephemeris to the alert mode setting unit 42.

[0148] The alert mode setting unit 42 stores the ephemeris (judgment criterion ephemeris) immediately before the spoofing alert mode is set. The alert mode setting unit 42 compares the ephemeris during the spoofing alert mode setting (the current ephemeris) with the judgment criterion ephemeris (S222).

[0149] The alert mode setting unit 42 continues to set the spoofing alert mode if the current ephemeris and the judgment criterion ephemeris are not the same (S223: NO).

[0150] The alert mode setting unit 42 cancels the spoofing alert mode (S224) if the current ephemeris and the judgment criterion ephemeris are the same (S223: YES).

[0151] (Spoofing Alert Mode Deactivation 3) Figure 15 is a flowchart showing a third example of the spoofing alert mode deactivation process.

[0152] While the spoofing warning mode is being set (S210), the demodulation unit 23 attempts to demodulate the navigation message of the received signal in the frequency band where the spoofing warning mode is set and to acquire the ephemeris.

[0153] If the demodulation unit 23 cannot acquire ephemeris (S221: NO), it outputs a result indicating that ephemeris could not be acquired to the alert mode setting unit 42. The alert mode setting unit 42 continues the spoofing alert mode.

[0154] If the demodulation unit 23 can acquire ephemeris (S221: YES), it outputs the acquired ephemeris to the alert mode setting unit 42.

[0155] The alert mode setting unit 42 stores the orbital information of the ephemeris (criteria ephemeris) immediately before the spoofing alert mode is set. The alert mode setting unit 42 acquires the orbital information of the ephemeris (the current ephemeris) for which the spoofing alert mode is set. The alert mode setting unit 42 compares the orbital information of the current ephemeris with the orbital information of the criteria ephemeris (S222A).

[0156] The alert mode setting unit 42 continues to set the spoofing alert mode if the difference between the orbit obtained from the orbit information of the current ephemeris and the orbit obtained from the orbit information of the judgment criterion ephemeris is greater than the threshold (S223A: NO).

[0157] The alert mode setting unit 42 cancels the spoofing alert mode (S224) if the difference between the launch obtained from the current ephemeris' orbital information and the launch obtained from the judgment criterion ephemeris's orbital information is below a threshold (S223A: YES).

[0158] (Spoofing Alert Mode Deactivation 4) Figure 16 is a flowchart showing the fourth example of the spoofing alert mode deactivation process.

[0159] While the spoofing alert mode is being set (S210), the positioning calculation unit 60 performs positioning including the positioning signals of the target satellites in spoofing alert mode and calculates a first positioning result (first positioning coordinates) (S231).

[0160] The positioning calculation unit 60 performs positioning using only the positioning signals of non-target satellites, without including the positioning signals of the target satellites in spoofing alert mode, and calculates a second positioning result (second positioning coordinates) (S232). The positioning calculation unit 60 outputs the first positioning result and the second positioning result to the alert mode setting unit 42.

[0161] The alert mode setting unit 42 calculates the difference between the first positioning coordinates and the second positioning coordinates (difference in positioning results). If the difference in positioning results is greater than the error threshold (S233: NO), the alert mode setting unit 42 continues to set the spoofing alert mode.

[0162] The alert mode setting unit 42 continues to calculate the difference in positioning results if the difference in positioning results is smaller than the error threshold (S233: YES). The alert mode setting unit 42 continues to set the spoofing alert mode if the duration of the state in which the difference in positioning results is smaller than the threshold does not reach the continuation threshold (S234: NO).

[0163] The alert mode setting unit 42 cancels the spoofing alert mode (S235) when the duration reaches the duration threshold (S234: YES).

[0164] (Spoofing Alert Mode Deactivation 5) Figure 17 is a flowchart showing the fifth example of the spoofing alert mode deactivation process.

[0165] During the setting of the spoofing alert mode (S210), the spoofing detection unit 30 detects the presence or absence of a spoofing signal by various methods, such as the method described above (S241). The spoofing detection unit 30 outputs the detection result of the presence or absence of a spoofing signal to the alert mode setting unit 42.

[0166] If a spoofing signal is detected (S242: NO), the alert mode setting unit 42 continues to set the spoofing alert mode.

[0167] The alert mode setting unit 42 continues to acquire the detection result for the presence or absence of a spoofing signal if there is no spoofing signal (S242: YES). The alert mode setting unit 42 continues to set the spoofing alert mode if the duration of time without a spoofing signal does not reach the continuation threshold (S243: NO). The continuation threshold is, for example, 3600 seconds, but is not limited to this and should be set based on the positioning stability required of the positioning device 10.

[0168] The alert mode setting unit 42 cancels the spoofing alert mode (S244) when the duration reaches the duration threshold (S243: YES).

[0169] (Spoofing Alert Mode Deactivation 6) Figure 18 is a flowchart showing the sixth example of the spoofing alert mode deactivation process.

[0170] During the setting of the spoofing alert mode (S210), the alert mode setting unit 42 starts timing from the start of the spoofing alert mode.

[0171] The alert mode setting unit 42 continues the spoofing alert mode setting if the duration of the spoofing alert mode has not reached the threshold (S251: NO). The duration threshold is, for example, 86,400 seconds, but is not limited to this, and should be set based on the positioning stability required of the positioning device 10.

[0172] The alert mode setting unit 42 cancels the spoofing alert mode (S252) when the duration reaches the duration threshold (S251: YES).

[0173] The NMA authentication results described above are important as an indicator of the reliability of positioning calculations for each received signal. Therefore, setting and notifying the NMA authentication status for each received signal is effective in performing positioning and generating reference frequency and timing signals. Accordingly, the setting and notification of the NMA authentication status will be described next.

[0174] Figure 19 is a functional block diagram showing a configuration for realizing a first example of NMA authentication setting and notification processing. As shown in Figure 19, in the NMA authentication setting and notification processing, the positioning device 10 includes at least a demodulation unit 23, an authentication unit 24, a reception state detection unit 50, and an authentication state setting unit 80.

[0175] (Types of Authentication Status) Figure 20 is a table showing the types of authentication statuses and the content of each status. As shown in Figure 20, the authentication status has three states: authenticated, unauthenticated, and unauthenticated. The authenticated state is the state in which the signal subject to NMA authentication (received signal) has been determined to be a legitimate positioning signal by NMA authentication. The unauthenticated state is the state in which the signal subject to NMA authentication has been determined to be a spoofing signal by NMA authentication. The unauthenticated state is the state that is neither authenticated nor unauthenticated.

[0176] (Specific examples of authentication methods) Figures 21(A), 21(B), and 21(C) show specific examples of NMA authentication processing. Figure 21(A) shows the state where NMA authentication was performed successfully (normal state). Figures 21(B) and 21(C) show the state where NMA authentication was not performed successfully (abnormal state).

[0177] In NMA authentication, an ephemeris and NMA data are used in pairs. Specifically, in a GNSS system equipped with NMA authentication, after a predetermined time has elapsed since the transmission of the ephemeris, the NMA data corresponding to this ephemeris is transmitted. The authentication unit 24 performs NMA authentication by comparing the received ephemeris and NMA data pairs.

[0178] The ephemeris is updated and transmitted at a predetermined time or at random intervals. When the ephemeris is updated, the corresponding NMA data is also updated and transmitted.

[0179] The authentication unit 24 receives and stores ephemeris and NMA data. When the authentication unit 24 receives updated ephemeris, it updates the stored ephemeris. In other words, the authentication unit 24 maintains the ephemeris stored at that time until it receives updated ephemeris.

[0180] Similarly, when the authentication unit 24 receives updated NMA data, it updates the NMA data it has stored. In other words, the authentication unit 24 maintains the NMA data it has stored at that time until it receives updated NMA data.

[0181] In such a GNSS system, NMA authentication is performed successfully in cases like the one shown in Figure 21(A).

[0182] As shown in Figure 21(A), after receiving the ephemeris EPH1 at time t1, the NMA data NMA1 is received after a predetermined time interval Δt.

[0183] The authentication unit 24 performs an NMA authentication determination using the ephemeris EPH1 and the NMA data NMA1 (authentication determination 1). The NMA data NMA1 is the NMA data corresponding to the ephemeris EPH1. Therefore, in this case, the authentication unit 24 determines that authentication is OK.

[0184] Subsequently, the ephemeris EPH1 is updated to ephemeris EPH2, and after receiving ephemeris EPH2 at time t2, NMA data NMA2 is received after a predetermined time interval Δt.

[0185] The authentication unit 24 uses the ephemeris EPH2 and the NMA data NMA2 to determine NMA authentication (authentication determination 2). The NMA data NMA2 is the NMA data corresponding to the ephemeris EPH2. Therefore, in this case, the authentication unit 24 determines that authentication is OK. This state corresponds to the authentication status.

[0186] By repeating this process without skipping any steps, NMA authentication can be continued.

[0187] On the other hand, NMA authentication fails to function properly, or in other words, NMA authentication is in an abnormal state, as shown in Figure 21(B) or Figure 21(C), for example.

[0188] Figure 21(B) shows the case where ephemeris EPH1 and its corresponding NMA data NMA1 are received at time t1, ephemeris EPH2 is not received at time t2, but its corresponding NMA data NMA2 is received.

[0189] In this case, for the pair of ephemeris EPH1 and NMA data NMA1 at time t1, the authentication unit 24 determines that authentication is OK. However, since ephemeris EPH2 at time t2 could not be received, but the corresponding NMA data NMA2 was received, the authentication unit 24 performs NMA authentication using ephemeris EPH1 and NMA data NMA2 and determines that authentication is NG. This state corresponds to the unauthenticated state.

[0190] Figure 21(C) shows the case where ephemeris EPH1 and its corresponding NMA data NMA1 are received at time t1, ephemeris EPH2 is received at time t2, but the corresponding NMA data NMA2 is not received.

[0191] In this case, for the pair of ephemeris EPH1 and NMA data NMA1 at time t1, the authentication unit 24 determines that authentication is OK. However, since ephemeris EPH2 at time t2 is received, but the corresponding NMA data NMA2 is not received, the authentication unit 24 performs NMA authentication using ephemeris EPH2 and NMA data NMA1, and determines that authentication is NG. This state corresponds to the unauthenticated state.

[0192] While performing this NMA authentication process, the positioning device 10 sets and notifies the authentication status as shown below.

[0193] (Process 1 to set to unauthenticated state) Figure 22 is a flowchart of the first example of the process to set the NMA authentication status to unauthenticated state. Figures 23(A) and 23(B) are diagrams showing an example of the state transition of the authentication status corresponding to Figure 22.

[0194] The authentication status has four states: authenticated, maintained, unauthenticated, and unauthenticated. The authenticated, unauthenticated, and unauthenticated states are as described above. The maintained state is the state in which the authentication status is maintained from the time authentication is determined to be OK until the next NMA authentication process is performed.

[0195] The authentication status setting unit 80 acquires the reception result from the reception status detection unit 50 when the device is in an authenticated state or an unauthenticated state (S300). The authentication status setting unit 80 maintains the authenticated status unless the device is in a reception failure state (S301: NO). The reception failure state includes the state in which the reception state described above has deteriorated and the state in which the received signal level cannot be obtained at all.

[0196] If the authentication status setting unit 80 is unable to receive data (S301: YES), it sets the authentication status to unauthenticated (S302).

[0197] For example, in Figure 23(A), authentication is periodically successful, and the authenticated state and the maintained authentication state are repeated. If reception fails, the authentication state setting unit 80 sets the state from the maintained authentication state (or authenticated state) to the unauthenticated state.

[0198] In the case of Figure 23(B), the unauthenticated state persists. If reception failure occurs, the authentication state setting unit 80 changes the state from unauthenticated to unauthenticated.

[0199] As a result, even if the reliability of the NMA authentication result becomes low due to the reception status, the positioning device 10 can suppress false authentication of either the authenticated or unauthenticated state and set it to the unauthenticated state. Therefore, the positioning device 10 can suppress notifying the user of an unreliable authentication status.

[0200] Furthermore, the authentication status setting unit 80 can measure the duration of the NMA's unauthenticated state and set the authentication status to unauthenticated if the duration of the unauthenticated state exceeds a threshold. This allows the positioning device 10 to revert to the unauthenticated state even if it is determined to be in an unauthenticated state by a data sequence transmitted during a period when the system does not transmit NMA data, or even if it continuously receives forged NMA data.

[0201] (Process 2 for setting to unauthenticated state) Figure 24 is a flowchart of a second example of the process for setting the NMA authentication status to unauthenticated state. Figures 25(A) and 25(B) are diagrams showing an example of the state transition of the authentication status corresponding to Figure 24.

[0202] The authentication status setting unit 80 performs timing in the authenticated or unauthenticated state (S300). The authentication status setting unit 80 maintains the authentication status until the scheduled time for ephemeris acquisition (S311: NO). If, at the scheduled time for ephemeris acquisition (S311: YES), and if there is no failure to acquire ephemeris (S312: NO), in other words, if ephemeris can be acquired, the authentication status 80 maintains the authentication status until the NMA authentication result for that time is obtained. The authentication status setting unit 80 obtains whether or not ephemeris has been acquired from the demodulation unit 23 and the authentication unit 24. If an authenticated or unauthenticated state is determined, the authentication status setting unit 80 sets the status to the determined authentication status.

[0203] The authentication status setting unit 80 sets the authentication status to unauthenticated (S313) if, at the scheduled time for acquiring ephemeris (S311: YES), it becomes impossible to acquire ephemeris (S312: YES), or in other words, if ephemeris cannot be acquired.

[0204] For example, in Figure 25(A), authentication is periodically successful, and the authenticated state and the maintained authentication state are repeated. If ephemeris acquisition becomes impossible, the authentication state setting unit 80 sets the state from the maintained authentication state (or authenticated state) to the unauthenticated state.

[0205] In the case of Figure 25(B), the unauthenticated state persists. If ephemeris acquisition becomes impossible, the authentication state setting unit 80 changes the state from unauthenticated to unauthenticated.

[0206] As a result, even if the reliability of the NMA authentication result becomes low due to the ephemeris acquisition status, the positioning device 10 can suppress false authentication of either the authenticated or unauthenticated state and set it to the unauthenticated state. Therefore, the positioning device 10 can suppress notifying the user of an unreliable authentication status.

[0207] (Processing when NMA authentication cannot be performed within the threshold time) Figure 26 is a flowchart showing the processing when NMA authentication cannot be performed within the threshold time.

[0208] When the authentication status setting unit 80 receives the acquisition of ephemeris from the demodulation unit 23 or the authentication unit 24 (S321), it starts timing (S322). When the authentication status setting unit 80 receives the completion of NMA authentication from the authentication unit 24 (S323), it detects the elapsed time since the acquisition of ephemeris (S324).

[0209] The authentication status setting unit 80 adopts the authentication result (S326) if the elapsed time is within the threshold time (S325: YES). In a GNSS system where the ephemeris is updated periodically, the threshold time can be set, for example, based on the update period of the ephemeris. Alternatively, in a GNSS system where the ephemeris is updated aperiodically, the threshold time can be set, for example, based on the shortest update interval in past ephemeris observation results.

[0210] If the elapsed time exceeds the threshold time (S325: NO), the authentication status setting unit 80 will not adopt the current authentication result and will maintain the authentication result adopted immediately before the current authentication (S327).

[0211] As a result, the positioning device 10 can suppress misidentification of the NMA in situations such as those shown in Figure 21(B), or in GNSS systems where the ephemeris update time is not precisely determined.

[0212] (Processing when NMA authentication cannot be renewed within the threshold time) Figure 27 is a flowchart showing the processing when NMA authentication cannot be renewed within the threshold time.

[0213] When the authentication status setting unit 80 receives an OK status for NMA authentication from the authentication unit 24 (S330), it starts timing (S331). When the authentication status setting unit 80 receives confirmation from the authentication unit 24 that a new NMA authentication has been completed (S332), it detects the elapsed time since the previous NMA authentication (S333).

[0214] If the elapsed time does not exceed the threshold time (S334: NO), the authentication status setting unit 80 determines that the newly NMA-authenticated received signal is a valid positioning signal (S336).

[0215] If the elapsed time exceeds the threshold time (S334: YES), the authentication status setting unit 80 determines that the newly NMA-authenticated received signal is a spoofing signal (S335).

[0216] As a result, the positioning device 10 can detect spoofing signals using specific bit sequences in systems that transmit specific bit sequences when not transmitting NMA data in an NMA authentication system, and exclude them from positioning calculations, etc.

[0217] Although the flowcharts for each process described above represent a single process, these processes are repeated. That is, even if the authentication status is set to unauthenticated in each process, if the reception status, ephemeris acquisition status, and NMA authentication are successfully restored, the authentication status will be set based on the authentication result.

[0218] (Jamming Detection Process) The jamming detection unit 41 detects jamming signals as follows. There are two types of jamming signals detected by the jamming detection unit 41. The first jamming signal is a jamming signal with a narrow frequency band (continuous wave jamming signal (CW jamming signal)). The second jamming signal is a jamming signal that has been spread and modulated over a wide frequency band. The spread and modulated jamming signal consists of a frequency-spread jamming signal and a frequency-modulated jamming signal. The frequency-spread jamming signal is a jamming signal in which the carrier signal frequency has been spread using a spreading code. The frequency-modulated jamming signal is a jamming signal in which the frequency of the carrier signal has been swept within a predetermined frequency band.

[0219] Figure 28 is a functional block diagram showing an example of the configuration of a jamming detection unit according to an embodiment of the present invention. As shown in Figure 28, the jamming detection unit 41 includes a spectrum generation unit 411, a peak level detection unit 412, a level difference calculation unit 413, a level difference integration unit 414, and a jamming determination unit 415. The jamming determination unit 415 includes a first determination unit 4151, a second determination unit 4152, and an integrated determination unit 4153.

[0220] The spectrum generation unit 411 generates the frequency spectrum of the received signal input from the input stage processing unit 201. The spectrum generation unit 411 outputs the frequency spectrum to the peak level detection unit 412 and the level difference calculation unit 413.

[0221] The peak level detection unit 412 detects the peak level of the frequency band targeted for jamming detection in the frequency spectrum. The peak level detection unit 412 outputs the peak level to the first determination unit 4151.

[0222] The level difference calculation unit 413 calculates the level difference between the spectral level of each of the multiple frequency components in the jamming detection target frequency band and a reference level. The reference level is set, for example, based on the noise floor level of the jamming detection target frequency band. The level difference calculation unit 413 outputs the level difference for each frequency component to the level difference integration unit 414.

[0223] The level difference integration unit 414 calculates a level difference integrated value by integrating the level differences of multiple frequency components in the frequency band targeted for jamming detection. The level difference integration unit 414 outputs the level difference integrated value to the second determination unit 4152.

[0224] The first determination unit 4151 compares the first jamming signal threshold with the peak level. The first jamming signal threshold is set, for example, based on the noise floor level of the frequency band to be jammed. The first jamming signal threshold may also be a fixed value set by an external input or the like.

[0225] The first determination unit 4151 determines that a signal is a first jamming signal if its peak level is higher than the threshold for the first jamming signal. The first determination unit 4151 outputs the determination result of the first jamming signal to the integrated determination unit 4153.

[0226] The second determination unit 4152 compares the second jamming signal threshold with the integrated level difference value. The second jamming signal threshold is set based on, for example, a combination of the gain value of the positioning device 10 and the noise floor level of the frequency band to be jammed.

[0227] The second determination unit 4152 determines that a signal is a second jamming signal if the accumulated level difference is higher than the threshold value for the second jamming signal. The second determination unit 4152 outputs the determination result for the second jamming signal to the integrated determination unit 4153.

[0228] The integrated determination unit 4153 performs a jamming determination as a jamming detection unit 41 based on the determination result of the first jamming signal and the determination result of the second jamming signal. Specifically, the integrated determination unit 4153 determines that a narrowband jamming signal has been detected if there is a first jamming signal and no second jamming signal. The integrated determination unit 4153 determines that a spread-modulated jamming signal has been detected if there is no first jamming signal and there is a second jamming signal. The integrated determination unit 4153 determines that a narrowband jamming signal and a spread-modulated jamming signal have been detected if there are both a first and a second jamming signal. The integrated determination unit 4153 determines that no jamming signal has been detected if there are neither a first nor a second jamming signal.

[0229] (Principle for Determining the First Jamming Signal) Figure 29 is a diagram illustrating the concept of determining the first jamming signal. As shown in Figure 29, since the first jamming signal is narrowband, a local level peak occurs at the frequency of the jamming signal. This peak level is significantly higher than the noise floor level.

[0230] The positioning signals of a GNSS system are either spread-coded signals or frequency-swept signals. Therefore, if the positioning signal is legitimate, localized peaks like those shown in Figure 29 do not usually occur.

[0231] Therefore, without the first jamming signal, no peaks higher than the threshold for the first jamming signal will occur. On the other hand, if the first jamming signal is present, a peak higher than the threshold for the first jamming signal will occur at the frequency of this first jamming signal.

[0232] The first determination unit 4151 determines the first jamming signal based on this principle.

[0233] (Determination process for the first jamming signal) Figure 30 is a flowchart showing an example of the determination process for the first jamming signal.

[0234] The spectrum generation unit 411 generates the frequency spectrum of the received signal in the frequency band to be detected for jamming. The frequency band to be detected for jamming can be any of the following: a predetermined frequency band centered on the frequency of each GNSS carrier signal, a frequency band used by each GNSS system, all frequency bands used by GNSS, or all frequency bands supported by the receiver (positioning device). By using a predetermined frequency band centered on the frequency of each GNSS carrier signal, jamming signals can be detected for each carrier signal frequency. By using the frequency band used by each GNSS system, jamming signals can be detected for each GNSS system. By using all frequency bands used by GNSS, jamming signals can be detected for the GNSS as a whole. Furthermore, by using all frequency bands supported by the receiver (positioning device), jamming signals can be detected in frequency bands other than those used by GNSS.

[0235] The peak level detection unit 412 detects the peak level in the frequency spectrum (S402).

[0236] The first determination unit 4151 compares the peak level with the first jamming signal threshold (CW threshold) (S403). The first jamming signal threshold is set to a level equal to the noise floor level + α (where α is a positive value). α can be set appropriately based on, for example, experimental results from simulating input of the first jamming signal, past observation results, etc. The first jamming signal threshold may also be a fixed value determined by an external input.

[0237] The first determination unit 4151 determines that there is a first jamming signal (CW jamming signal) if the peak level is higher than the threshold for the first jamming signal (S404: YES) (S405). The first determination unit 4151 determines that there is no first jamming signal (CW jamming signal) if the peak level is less than or equal to the threshold for the first jamming signal (S404: NO) (S406).

[0238] (Setting the threshold for the first jamming signal) The threshold for the first jamming signal may be a fixed value, but it can also be updated. The threshold at the beginning of the process is set, for example, based on the average value of the noise floor level before jamming detection is performed. This value can be set as the fixed value for the first jamming signal threshold.

[0239] Furthermore, if the antenna ANT and positioning device 10 are integrated, or if the connection system between the antenna ANT and positioning device 10 is known in advance, the reference noise floor level is known in advance. Therefore, the first jamming signal threshold can be set as a fixed value using the noise floor level known at the time of shipment.

[0240] Figure 31 is a flowchart showing an example of the process for updating the threshold for the first jamming signal.

[0241] When the timing for updating the first jamming signal threshold is reached, the spectrum generation unit 411 generates the frequency spectrum of the jamming detection target frequency band at that timing (S411). The update timing can be set, for example, in advance at a predetermined time or by manual input.

[0242] The first determination unit 4151 calculates the noise floor level of the frequency band to be detected for jamming (S412). Based on the noise floor level calculated in S412, the first determination unit 4151 updates the first jamming signal threshold (CW threshold) (S413). For example, the first determination unit 4151 updates the first jamming signal threshold (CW threshold) based on the average value of the noise floor level of the frequency band to be detected for jamming.

[0243] By performing this process, the threshold value for the first jamming signal can be dynamically set. This allows the first determination unit 4151 to set the threshold value for the first jamming signal (CW threshold value) according to the system gain of the positioning system (combination of antenna ANT and positioning device 10) at the time of detection of the first jamming signal. Therefore, the first determination unit 4151 can determine and detect the first jamming signal with high accuracy.

[0244] (Principle for Determining the Second Jamming Signal) Figures 32(A) and 32(B) illustrate the concept of determining the second jamming signal. Figure 32(A) shows the concept of setting the threshold for the second jamming signal, and represents the case when there is no jamming signal. Figure 32(B) illustrates the concept of determining the second jamming signal.

[0245] As shown in Figure 32(B), the second jamming signal is broadband, so it does not necessarily produce localized peaks like the first jamming signal. On the other hand, because the frequency of the second jamming signal is spread out, the average level of the noise floor in the frequency band targeted for jamming detection is higher (see frequency band FBL1).

[0246] Therefore, when the differences for each frequency component between the noise floor level when there is no second jamming signal (reference noise floor) and the noise floor level of the signal being judged are accumulated, the accumulated value when there is a second jamming signal is positive and large (see the accumulated value ΣΔP(L1) in Figure 32(B)), while the accumulated value when there is no second jamming signal is small (approaches 0).

[0247] The second determination unit 4152 determines the second jamming signal based on the difference in these accumulated values.

[0248] Furthermore, if the cumulative value becomes large and negative, it indicates that the received signal level is low, suggesting that an abnormality has occurred in the antenna connection system. The second determination unit 4152 determines the abnormality in the antenna connection system based on this principle.

[0249] (Second Jamming Signal Determination Process 1) Figure 33 is a flowchart showing a first example of the second jamming signal determination process.

[0250] The spectrum generation unit 411 generates the frequency spectrum at the time of initial positioning (see Figure 32(A)) (S501). The second determination unit 4152 calculates a reference level for the jamming detection target frequency band based on the frequency spectrum generated in S501 (S502). The reference level is calculated, for example, based on the average value of the noise floor level of the jamming detection target frequency band.

[0251] For example, referring to Figure 32(A), the average value of the noise floor level of the frequency band FBL1 (center frequency fL1) of the L1 signal is set as the reference level Lnf(L1) for the frequency band FBL1. Similarly, the average value of the noise floor of the frequency band FBL5 (center frequency fL5) of the L5 signal is set as the reference level Lnf(L5) for the frequency band FBL5.

[0252] Furthermore, the reference level can be, for example, the maximum, minimum, or midpoint of the noise floor.

[0253] The spectrum generation unit 411 generates the frequency spectrum at the time of jamming detection (see Figure 32(B)) (S503).

[0254] The second determination unit 4152 calculates the level difference between each frequency component of the jamming detection target frequency band and the reference level (S504). For example, referring to Figure 32(B), for the L1 signal, the level difference between each frequency component of the frequency band FBL1 and the reference level Lnf(L1) is calculated. For the L5 signal, the level difference between each frequency component of the frequency band FBL5 and the reference level Lnf(L5) is calculated.

[0255] The second determination unit 4152 integrates the level differences (S505). For example, referring to Figure 32(B), for the L1 signal, the level differences of multiple frequency components are integrated over the entire frequency band FBL1 to calculate the integrated value ΣΔP(L1). For the L5 signal, the level differences of multiple frequency components are integrated over the entire frequency band FBL5 to calculate the integrated value ΣΔP(L5).

[0256] The second determination unit 4152 determines that a jamming signal is present in the target frequency band if the accumulated value is higher than the upper threshold (positive value) (S506: YES) (S507). The upper threshold is set to the level of the noise floor at the time of initial positioning + β1 (β1 is a positive value). β1 can be set appropriately based on, for example, experimental results in which a second jamming signal is input, past observation results, etc.

[0257] For example, referring to the frequency band FBL1 of the L1 signal in Figure 32(B), if there is a second jamming signal, the integrated value ΣΔP(L1) is a large positive value. Therefore, the integrated value ΣΔP(L1) becomes higher than the upper threshold. As a result, the second determination unit 4152 can determine that there is a second jamming signal in the frequency band FBL1 of the L1 signal.

[0258] The second determination unit 4152 determines that there is an abnormality in the antenna connection system if the accumulated value is lower than the lower threshold (negative value) (S506: NO, S508: YES) (S509). The lower threshold is set to the level of the noise floor at the time of initial positioning + β2 (β2 is a negative value). β2 can be set appropriately based on, for example, the signal loss level when an abnormality in the antenna connection system or transmission system is simulated.

[0259] For example, referring to the frequency band FBL5 of the L5 signal in Figure 32(B), if there is an abnormality in the antenna connection system or transmission system, the integrated value ΣΔP(L2) will be negative and its absolute value will be large. Therefore, the integrated value ΣΔP(L2) will be lower than the lower threshold. As a result, the second determination unit 4152 can determine that there is an abnormality in the antenna connection system in the frequency band FBL5 of the L5 signal.

[0260] Furthermore, the second determination unit 4152 determines that there is no second jamming signal if the accumulated value is between the lower limit and the upper limit (S506: NO, S508: YES). In this case, it is preferable that the second determination unit 4152 detects that there are no abnormalities in the antenna connection system or the transmission system. That is, if it can detect that there are no abnormalities in the antenna connection system or the transmission system, the second determination unit 4152 can more reliably determine that there is no second jamming signal if the accumulated value is between the lower limit and the upper limit (S506: NO, S508: YES).

[0261] (Second Jamming Signal Detection Process 2) Figure 34 is a flowchart showing a second example of the second jamming signal detection process.

[0262] The spectrum generation unit 411 generates the frequency spectrum at the time of initial positioning (see Figure 32(A)) (S501). The second determination unit 4152 calculates a reference level for the jamming detection target frequency band based on the frequency spectrum generated in S501 (S502).

[0263] The second determination unit 4152 has pre-set upper and lower threshold values ​​for the reference level. The upper threshold value is set, for example, based on the upper limit of the system gain of the positioning system. The lower threshold value is set, for example, based on the lower limit of the system gain of the positioning system.

[0264] For example, referring to Figure 32(A), the second determination unit 4152 sets an upper threshold THH(L1) and a lower threshold THL(L1) for the frequency band FBL1. The second determination unit 4152 also sets an upper threshold THH(L5) and a lower threshold THL(L5) for the frequency band FBL5.

[0265] The second determination unit 4152 compares the reference level with the upper threshold. If the reference level is higher than the upper threshold (S523: YES), the second determination unit 4152 determines that there is a possibility of a second jamming signal (S524).

[0266] By performing this process, the second determination unit 4152 can determine that there is a possibility that the second jamming signal is present, even if the second jamming signal is present during the initial positioning.

[0267] The second determination unit 4152 determines that there is an abnormality in the antenna connection system (S526) if the reference level is below the upper threshold (S523: NO) and below the lower threshold (S525: YES).

[0268] (Second Jamming Signal Detection Process 3) Figure 35 is a flowchart of a third example of the second jamming signal detection process. The detection process in the third example differs from the detection process in that it can also detect RF anomalies. Therefore, the explanation of the process in the third example will only describe the parts that differ from the process in the second example.

[0269] The second determination unit 4152 determines that there is an RF abnormality (S532) if the reference level is below the upper threshold (S523: NO), below the lower threshold (S525: YES), and if it can determine that there is no abnormality in the antenna connection system (S531: YES). Whether or not there is an abnormality in the antenna connection system can be determined by separately checking the connection status, transmission system loss, etc.

[0270] Specifically, even if there are no abnormalities in the antenna connection system, if a high-level signal is detected in a frequency band different from the jamming detection target frequency band, the noise floor level of the jamming detection target frequency band may decrease. Such cases where a high-level signal exists in a frequency band different from the jamming detection target frequency band are considered RF abnormalities.

[0271] In such cases, by performing the processing shown in the third example in Figure 35, the second determination unit 4152 can determine whether or not there is a second jamming signal, whether or not there is an abnormality in the antenna connection system, and whether or not there is an RF abnormality.

[0272] Furthermore, in each of the above processes, if only the determination of the second jamming signal is required, the process using the lower threshold can be omitted.

[0273] (Reference level update process 1 for the second jamming signal) Figure 36 is a flowchart showing the first example of the reference level update process for the second jamming signal.

[0274] The second determination unit 4152 acquires the level of the received signal in the frequency band targeted for jamming detection (S541). The level of the received signal can be obtained, for example, from the reception status detection unit 50.

[0275] The second determination unit 4152 compares the signal level with the normal threshold. If the signal level is equal to or greater than the normal threshold (S542: YES), the second determination unit 4152 detects the noise floor level of the jamming detection target frequency band (S543). The normal threshold can be set appropriately based on the system gain of the positioning system, etc.

[0276] Furthermore, if the signal level is below the normal threshold (S542: NO), the second determination unit 4152 does not perform the reference level update process.

[0277] The second determination unit 4152 calculates the difference between the already set reference level and the noise floor level detected this time (S544).

[0278] If the difference is greater than the switching threshold (S545: YES), the second determination unit 4152 sets (updates) the level of the noise floor detected this time as the new reference level (S546). If the difference is less than or equal to the switching threshold (S545: NO), the second determination unit 4152 maintains the already set reference level (S547).

[0279] With this configuration, the second determination unit 4152 can appropriately update the reference level for determining the second jamming signal, even if there is a change in the system gain or the like.

[0280] (Reference level update process 2 for the second jamming signal) Figure 37 is a flowchart of the second example of the reference level update process for the second jamming signal. The second example of the reference level update process differs from the first example of the reference level update process in that it adds a determination based on the navigation message. Therefore, the explanation of the process in the second example of the reference level update process will only describe the parts that differ from the process in the first example of the reference level update process.

[0281] The second determination unit 4152 attempts to acquire a navigation message if the signal level is above the normal threshold (S542: YES). The second determination unit 4152 acquires a navigation message from, for example, the demodulation unit 23.

[0282] If the second determination unit 4152 can acquire a navigation message (S551: YES), it performs a reference level update process using the noise floor level from step S543 onwards.

[0283] The second determination unit 4152 does not perform the reference level update process if it cannot acquire a navigation message (S551: NO).

[0284] With this configuration, the second determination unit 4152 can update the reference level based on a regular positioning signal that has been demodulated from the navigation message.

[0285] (Method for setting the noise floor level for jamming signal detection) As described above, the jamming detection unit detects jamming signals based on the noise floor level. Therefore, the accuracy of setting the noise floor level affects the accuracy of jamming signal detection.

[0286] Therefore, it is preferable to set the noise floor level with temperature compensation as follows. Figure 38 is a functional block diagram showing an example of the configuration of a jamming detection unit equipped with a temperature compensation function for the noise floor level.

[0287] As shown in Figure 38, the jamming detection unit 415T differs from the jamming detection unit 415 shown in Figure 28 in that it includes a noise floor setting unit 4154. The other components of the jamming detection unit 415T are the same as those of the jamming detection unit 415, and a description of the similar parts will be omitted.

[0288] A temperature sensor ST is connected to the noise floor setting unit 4154.

[0289] The temperature sensor ST measures the temperature of the positioning device 10. In this case, it is preferable that the temperature sensor ST measures the temperature of the circuit elements (for example, semiconductor elements such as LNAs) that make up the input stage processing unit 201 and the reception state detection unit 50. The temperature sensor ST outputs the measured temperature to the noise floor setting unit 4154.

[0290] The noise floor setting unit 4154 sets the noise floor level based on the measured temperature. The noise floor setting unit 4154 outputs the set noise floor level to the second determination unit 4152. The second determination unit 4152 determines the second jamming signal based on the noise floor level set by the noise floor setting unit 4154.

[0291] (Setting process for the level of the first temperature-sensitive noise floor) Figure 39 is a flowchart showing an example of the setting process for the level of the first temperature-sensitive noise floor.

[0292] The noise floor setting unit 4154 acquires the temperature measured by the temperature sensor ST (S601).

[0293] The noise floor setting unit 4154 pre-stores the noise floor level of the positioning device 10 at a reference temperature (e.g., 25°C). The noise floor setting unit 4154 also pre-stores the temperature difference from the reference temperature and the relationship between the temperature difference and the correction value of the noise floor level.

[0294] The noise floor setting unit 4154 calculates the temperature difference between the measured temperature and the reference temperature (S611).

[0295] The noise floor setting unit 4154 calculates a correction value for the noise floor level according to the temperature difference (S612).

[0296] The noise floor setting unit 4154 corrects the noise floor level at the reference temperature using a correction value (S613). The noise floor setting unit 4154 outputs the corrected noise floor level.

[0297] (Setting the level of the second temperature-dependent noise floor) Figure 40 is a flowchart showing an example of the setting process for the level of the second temperature-dependent noise floor.

[0298] The noise floor setting unit 4154 acquires the temperature measured by the temperature sensor ST (S601).

[0299] The noise floor setting unit 4154 has a table pre-stored that shows the relationship between temperature and the noise floor level of the positioning device 10.

[0300] The noise floor setting unit 4154 refers to a table of relationships between temperature and noise floor level and extracts the noise floor level corresponding to the measured temperature (S621).

[0301] The noise floor setting unit 4154 sets the noise floor level extracted from the relationship table to the noise floor level for determining the jamming signal (S622). The noise floor setting unit 4154 outputs the set noise floor level.

[0302] By performing one of the above processes, the jamming detection unit 415T can appropriately set the noise floor level according to the temperature of the positioning device 10. As a result, the jamming detection unit 415T can determine the second jamming signal with high accuracy.

[0303] Furthermore, the noise floor level set in the noise floor setting unit 4154 can also be used in the determination of the first jamming signal in the first determination unit 4151.

[0304] Furthermore, the above-mentioned processes can be combined as appropriate, and each combination can produce different effects.

[0305] (1) A positioning device comprising: a spectrum generation unit that generates a frequency spectrum of a received signal; a peak level detection unit that detects the peak level of a frequency band to be detected for jamming in the frequency spectrum; and a determination unit that compares a first jamming signal threshold with the peak level to determine a first jamming signal of a continuous wave.

[0306] (2) A positioning device comprising: a spectrum generation unit that generates the frequency spectrum of a received signal; a level difference calculation unit that calculates the level difference between the spectral level and a reference level for each of a plurality of frequency components in the frequency band to be detected for jamming; a level difference integration unit that integrates the level differences of the plurality of frequency components; and a determination unit that compares a second jamming signal threshold with the integrated value of the level differences to determine a second jamming signal that is spread frequency or frequency modulated.

[0307] (3) A positioning device as described in (2), comprising: a peak level detection unit for detecting the peak level of a frequency band to be detected for jamming in a frequency spectrum; a first determination unit for determining a first continuous wave jamming signal by comparing a first jamming signal threshold with the peak level; and an integrated determination unit for comprehensively determining whether or not a jamming signal has been received based on the determination result of the first jamming signal and the determination result of the second jamming signal.

[0308] (4) A positioning device as described in (3), wherein the first determination unit sets the first jamming signal threshold based on the noise floor level, and updates the first jamming signal threshold based on the noise floor level at each preset update timing.

[0309] (5) A positioning device according to any one of (2) to (4), wherein the second determination unit sets the second jamming signal threshold based on the noise floor of the jamming detection target frequency band, and updates the second jamming signal threshold based on the noise floor level at each preset update timing.

[0310] (6) A positioning device according to any one of (2) to (5), wherein the second determination unit calculates the level difference between the level of the noise floor of the jamming detection target frequency band at the update timing and the level of the noise floor on which the second jamming signal threshold has already been set, and determines whether or not to update the second jamming signal threshold based on the level difference.

[0311] (7) A positioning device according to any one of (2) to (5), wherein the second determination unit determines whether or not to update the second jamming signal threshold based on whether or not the navigation message of the received signal has been acquired.

[0312] (8) A positioning device according to any one of (2) to (7), wherein the second determination unit sets the second jamming signal threshold for each frequency band of the positioning signal.

[0313] (9) A positioning device according to any one of (2) to (8), wherein the second determination unit sets a lower threshold for the cumulative value and determines a reception abnormality by comparing the cumulative value with the lower threshold.

[0314] (10) A positioning device according to any one of (2) to (9), wherein the spectrum generation unit generates a frequency spectrum at the time of initial positioning, the second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning, and determines the possibility of the second jamming signal by comparing the reference level with a preset upper threshold value.

[0315] (11) A positioning device according to any one of (2) to (10), wherein the spectrum generation unit generates a frequency spectrum at the time of initial positioning, the second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning, and determines the possibility of reception abnormality by comparing the reference level with a preset lower threshold.

[0316] (12) A positioning device according to any one of (2) to (11), wherein the determination unit includes a noise floor setting unit that sets the level of the noise floor used for setting the second jamming signal threshold, and the noise floor setting unit sets the level of the noise floor based on temperature.

[0317] (13) A positioning device according to any one of (1) to (12), comprising a positioning calculation unit that performs positioning calculations using the positioning signal in the received signal.

[0318] (14) A positioning device according to any one of (1) to (13), comprising a reference signal generating unit that generates a reference frequency signal or a timing signal using the positioning signal in the received signal. term

[0319] Not all objectives or effects / benefits can necessarily be achieved in accordance with any particular embodiment described herein. Therefore, for example, a person skilled in the art will realize that a particular embodiment may be configured to achieve or optimize one or more effects / benefits taught herein, without necessarily achieving other objectives or effects / benefits taught or suggested herein.

[0320] All processes described herein can be fully automated and implemented by software code modules executed by a computing system including one or more computers or processors. The code modules can be stored in any type of non-temporary computer-readable medium or other computer storage device. Some or all of these methods can be implemented in dedicated computer hardware.

[0321] It will be apparent from this disclosure that there are many other variations not described herein. For example, depending on the embodiment, any particular operation, event, or function of any of the algorithms described herein may be performed in different sequences, and may be added, merged, or excluded entirely (e.g., not all described actions or events are necessary for the execution of the algorithm). Furthermore, in certain embodiments, the operations or events may be performed in parallel rather than sequentially, for example, through multithreading, interrupt handling, or via multiple processors or processor cores, or on other parallel architectures. In addition, different tasks or processes may also be performed by different machines and / or computing systems that can work together.

[0322] Various exemplary logic blocks and modules described in relation to the embodiments disclosed herein can be implemented or executed by a machine such as a processor. The processor may be a microprocessor, but alternatively, the processor may be a controller, a microcontroller, or a state machine, or a combination thereof. The processor may include electrical circuits configured to process computer-executable instructions. In another embodiment, the processor may include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable device that performs logic operations without processing computer-executable instructions. The processor may also be implemented as a combination of computing devices, for example, a combination of a digital signal processor (digital signal processing device) and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. Although the description herein mainly concerns digital technology, the processor may also include mainly analog elements. For example, some or all of the signal processing algorithms described herein may be implemented by analog circuits or mixed analog and digital circuits. The computing environment may include, but is not limited to, any type of computer system based on a microprocessor, mainframe computer, digital signal processor, portable computing device, device controller, or in-device computing engine.

[0323] Unless otherwise specified, conditional language such as “can,” “could,” “will,” or “may” is understood to mean in the context of commonly used expressions to convey that a particular embodiment includes certain features, elements, and / or steps, but other embodiments do not. Thus, such conditional language does not generally mean that features, elements, and / or steps are any way required in one or more embodiments, or that one or more embodiments necessarily include logic for determining whether these features, elements, and / or steps are included in or performed in any particular embodiment.

[0324] Disjunctive language, such as the phrase "at least one of X, Y, and Z," is understood in contexts where it is commonly used to indicate that an item, term, etc., can be any one of X, Y, Z, or any combination thereof, unless otherwise specified (e.g., X, Y, Z). Therefore, such disjunctive language does not generally imply that a particular embodiment requires each of at least one of X, at least one of Y, or at least one of Z, each of which exists.

[0325] Any process description, element, or block in the flowcharts described herein and / or shown in the accompanying drawings should be understood as representing a potentially module, segment, or portion of code containing one or more executable instructions for implementing a particular logical function or element in the process. Alternative embodiments are included within the scope of the embodiments described herein, where elements or functions may be removed, performed in no particular order, substantially simultaneously or in reverse order, depending on the relevant functionality, as will be understood by those skilled in the art.

[0326] Unless otherwise explicitly stated, numerals such as “one” should generally be interpreted as including one or more described items. Thus, phrases such as “one device configured to do…” are intended to include one or more enumerated devices. Such one or more enumerated devices may also be collectively configured to perform the stated citation. For example, “a processor configured to perform A, B and C below” could include a first processor configured to perform A and a second processor configured to perform B and C. In addition, even if an enumeration of a specific number of the introduced embodiments is explicitly listed, a person skilled in the art should interpret such an enumeration as typically meaning at least the number listed (for example, a mere enumeration of “two enumerations” without other modifiers usually means at least two enumerations, or two or more enumerations).

[0327] In general, a person skilled in the art will find that the terms used herein are generally intended to be "non-limiting" terms (for example, the term "including" should be interpreted as "including, but at least," the term "having" should be interpreted as "having at least," and the term "including" should be interpreted as "including, but not limited to, the following").

[0328] For illustrative purposes, the term “horizontal” as used herein is defined as a plane parallel to the floor or surface of the area in which the system described is used, or the plane on which the method described is implemented, regardless of its direction. The term “floor” may be replaced with the terms “ground” or “water surface.” The term “vertical / perpendicular” refers to a direction perpendicular / perpendicular to the defined horizontal line. Terms such as “upper side,” “lower side,” “below,” “up,” “on the side,” “higher,” “lower,” “above,” and “below” are defined in relation to the horizontal plane.

[0329] As used herein, the terms “adhere,” “connect,” “pair,” and other related terms should be interpreted, unless otherwise noted, as including removable, movable, fixed, adjustable, and / or removable connections or linkages. Connections / linkages include direct connections and / or connections having an intermediate structure between the two components described.

[0330] Unless otherwise explicitly stated, the numbers preceded by terms such as “approximately,” “about,” and “substantially,” as used herein, include the enumerated numbers and represent quantities close to the stated quantities that further perform the desired function or achieve the desired result. For example, “approximately,” “about,” and “substantially,” unless otherwise explicitly stated, mean values ​​less than 10% of the stated numbers. Features of embodiments disclosed preceded by terms such as “approximately,” “about,” and “substantially,” as used herein, represent features with some variability that further perform the desired function or achieve the desired result with respect to that feature.

[0331] Many variations and modifications can be made to the embodiments described above, and these elements should be understood as being within other acceptable examples. All such modifications and variations are intended to be included within the scope of this disclosure and are protected by the following claims.

[0332] 10: Positioning device 20: Signal processing unit 21: Acquisition and tracking unit 22: Positioning signal observation unit 23: Demodulation unit 24: Authentication unit 30, 30A, 30B: Spoofing detection unit 31: Residual calculation unit 32: Residual difference calculation unit 33, 33B: Determination unit 34: Signal level detection unit 35: Target signal selection unit 41: Jamming detection unit 42: Warning mode setting unit 50: Reception status detection unit 60: Positioning calculation unit 70: Reference signal generation unit 80: Authentication status setting unit 90: Output unit 201: Input stage processing unit 411: Spectrum generation unit 412: Peak level detection unit 413: Level difference calculation unit 414: Level difference integration unit 415, 415T: Jamming determination unit 4151: First determination unit 4152: Second determination unit 4153: Integrated determination unit 4154: Noise floor setting unit ANT: Antenna

Claims

1. A positioning device comprising: a spectrum generation unit that generates a frequency spectrum of a received signal; a peak level detection unit that detects the peak level of the frequency band to be detected for jamming in the frequency spectrum; and a determination unit that compares a first jamming signal threshold with the peak level to determine a first jamming signal of a continuous wave.

2. A positioning device comprising: a spectrum generation unit for generating the frequency spectrum of a received signal; a level difference calculation unit for calculating the level difference between the spectral level and a reference level for each of a plurality of frequency components in the frequency band targeted for jamming detection; a level difference integration unit for integrating the level differences of the plurality of frequency components; and a determination unit for determining a second jamming signal that is spread frequency or frequency modulated by comparing a second jamming signal threshold with the integrated value of the level differences.

3. A positioning device according to claim 2, comprising: a peak level detection unit for detecting the peak level of a frequency band to be detected for jamming in a frequency spectrum; a first determination unit for determining a first continuous wave jamming signal by comparing a first jamming signal threshold with the peak level; and an integrated determination unit for comprehensively determining whether or not a jamming signal has been received based on the determination result of the first jamming signal and the determination result of the second jamming signal.

4. A positioning device according to claim 3, wherein the first determination unit sets the first jamming signal threshold based on the noise floor level, and updates the first jamming signal threshold based on the noise floor level at each preset update timing.

5. A positioning device according to claim 2, wherein the second determination unit sets a second jamming signal threshold based on the noise floor of the jamming detection target frequency band, and updates the second jamming signal threshold based on the noise floor level at each preset update timing.

6. A positioning device according to claim 2, wherein the second determination unit calculates the level difference between the noise floor level of the jamming detection target frequency band at the update timing and the noise floor level on which the second jamming signal threshold has already been set, and determines whether or not to update the second jamming signal threshold based on the level difference.

7. A positioning device according to claim 2, wherein the second determination unit determines whether or not to update the second jamming signal threshold based on whether or not the navigation message of the received signal has been acquired.

8. A positioning device according to claim 2, wherein the second determination unit sets the second jamming signal threshold for each frequency band of the positioning signal.

9. A positioning device according to claim 2, wherein the second determination unit sets a lower threshold for the cumulative value and determines a reception abnormality by comparing the cumulative value with the lower threshold.

10. A positioning device according to claim 2, wherein the spectrum generation unit generates a frequency spectrum at the time of initial positioning, the second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning, and determines the possibility of the second jamming signal by comparing the reference level with a preset upper threshold value.

11. A positioning device according to claim 2, wherein the spectrum generation unit generates a frequency spectrum at the time of initial positioning, the second determination unit calculates a reference level for the jamming detection target frequency band based on the frequency spectrum at the time of initial positioning, and determines the possibility of a reception abnormality by comparing the reference level with a preset lower threshold.

12. A positioning device according to claim 2, wherein the determination unit includes a noise floor setting unit that sets the level of the noise floor used for setting the second jamming signal threshold, and the noise floor setting unit sets the level of the noise floor based on temperature.

13. A positioning device according to claim 1, comprising a positioning calculation unit that performs positioning calculations using the positioning signal in the received signal.

14. A positioning device according to claim 1, comprising a reference signal generating unit that generates a reference frequency signal or a timing signal using the positioning signal in the received signal.

15. A positioning method comprising: generating a frequency spectrum of a received signal; detecting the peak level of the jamming detection target frequency band in the frequency spectrum; and comparing the first jamming signal threshold with the peak level to determine a first continuous wave jamming signal.

16. A positioning method comprising: generating the frequency spectrum of a received signal; calculating the level difference between the spectral level of each of several frequency components in the jamming detection target frequency band and a reference level; integrating the level differences of the several frequency components; and comparing the second jamming signal threshold with the integrated value of the level differences to determine a second jamming signal that is spread frequency or frequency modulated.

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