WO2011065559A1 - 不要信号判別装置、不要信号判別方法、不要信号判別プログラム、gnss受信装置および移動端末 - Google Patents
不要信号判別装置、不要信号判別方法、不要信号判別プログラム、gnss受信装置および移動端末 Download PDFInfo
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- WO2011065559A1 WO2011065559A1 PCT/JP2010/071330 JP2010071330W WO2011065559A1 WO 2011065559 A1 WO2011065559 A1 WO 2011065559A1 JP 2010071330 W JP2010071330 W JP 2010071330W WO 2011065559 A1 WO2011065559 A1 WO 2011065559A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/21—Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/22—Multipath-related issues
Definitions
- the present invention relates to an unnecessary signal discriminating apparatus that discriminates an unnecessary signal included in a received signal, and a GNSS receiving apparatus that includes the unnecessary signal discriminating apparatus and acquires a desired positioning signal included in the received signal.
- GNSS systems such as GPS and Galileo
- positioning signals from a plurality of GNSS satellites are received, and the positioning signals are demodulated and used for positioning and the like.
- Patent Document 2 determines that an unnecessary signal is present when the number of spectrum peaks of the received signal is detected to be a predetermined value or more.
- the identification is simply performed by the CN of the received signal, but if it exceeds the CN, the signal is adopted as a positioning signal. Therefore, an interference wave caused by a communication signal other than the target system, There is a possibility that an unnecessary signal due to multipath or even cross-correlation is erroneously captured as a positioning signal.
- Patent Document 2 can determine that there is an unnecessary signal, but cannot determine the type of unnecessary signal as described above.
- the present invention relates to an unnecessary signal discriminating apparatus for discriminating an unnecessary signal from a received signal including a target signal code-modulated with a predetermined spreading code.
- the unnecessary signal discriminating apparatus includes a correlation data string acquisition unit and a discrimination unit.
- the correlation data string acquisition unit acquires a correlation data string on the code phase axis and a correlation data string on the frequency axis from the correlation data between the replica code for the spreading code and the received signal.
- the discriminating unit discriminates an unnecessary signal based on the correlation data string on the code phase axis and the correlation data string on the frequency axis.
- the correlation data string acquisition unit stores the correlation data for a predetermined time, and converts the stored correlation data into data in the frequency domain, whereby the correlation data string on the code phase axis and the frequency axis Get correlation data string.
- the present invention also relates to an unnecessary signal determining method and an unnecessary signal determining program for determining an unnecessary signal from a received signal including a target signal code-modulated with a predetermined spreading code.
- the unnecessary signal determination method and the unnecessary signal determination program acquire a correlation data string on the code phase axis and a correlation data string on the frequency axis from the correlation data between the replica code for the spreading code and the received signal. Then, the unnecessary signal determination method and the unnecessary signal determination program determine an unnecessary signal based on the correlation data string on the code phase axis and the correlation data string on the frequency axis.
- the target signal (FIG.
- the difference between the reference signal and the unnecessary signal (see FIGS. 4B to 4D) is used.
- the unnecessary signal is discriminated by obtaining the above-mentioned biaxial characteristics of the correlation data of the received signal, that is, the correlation data string on the code phase axis and the correlation data string on the frequency axis.
- the discriminating unit of the unnecessary signal discriminating apparatus of the present invention stores in advance, as reference characteristics, a correlation data string on the code phase axis and a correlation data string on the frequency axis of correlation data obtained by correlating the target signal with a replica code. .
- the discriminating unit compares the reference characteristic with the correlation data string on the code phase axis of the correlation data obtained by correlating the received signal with the replica code and the actual measurement characteristic based on the correlation data string on the frequency axis, and generates an unnecessary signal. Determine.
- the discriminating unit of the unnecessary signal discriminating apparatus of the present invention corrects the correlation data of the reference characteristic or the actually measured characteristic so that the peak levels of the correlation data in the reference characteristic and the actually measured characteristic coincide with each other, and after the correction
- the unnecessary signal is discriminated by calculating the similarity in the code phase axis and the frequency axis using the above characteristics.
- the similarity is specifically composed of a difference value between the corrected characteristics.
- the result of observing the correlation data of the target signal along the two axes of the code phase axis and the frequency axis is acquired in advance as a reference characteristic. Then, the measured characteristic based on the correlation data of the received signal is compared with the reference characteristic, and if the similarity is not higher than a predetermined level, it is determined that the received signal is an unnecessary signal. By comparing such measured characteristics with reference characteristics, unnecessary signals can be accurately determined. And by performing discrimination based on such similarity, it is possible to suppress the influence due to the change in the C / N of the received signal, and to accurately discriminate unnecessary signals. In particular, if the similarity is calculated and determined after matching the peak levels of the reference characteristics and measured characteristics, the influence of the level of the received signal itself and the setting level of the reference characteristics can be suppressed. Can be determined.
- the discriminating unit of the unnecessary signal discriminating apparatus of the present invention uses both the similarity on the frequency axis and the similarity on the code phase axis to change the type of the unnecessary signal to multipath, cross-correlation, and interference wave. judge.
- the discriminating unit of the unnecessary signal discriminating apparatus of the present invention based on the number of peak levels of the correlation data on the code phase axis and the number of peak levels of the correlation data on the frequency axis and the positional relationship between the peaks, Discriminate between interference, multipath, and cross-correlation.
- This configuration shows a method for discriminating unnecessary signals when the above-described similarity is not used.
- unnecessary signals such as multipaths, cross-correlation, and interference waves have correlation data string characteristics different from the target signal on the frequency axis and code phase axis. Specifically, the number of peaks and the positional relationship between the peaks are different. Furthermore, the characteristics of the correlation data string are different even among multipaths, cross-correlation, and interference waves. Therefore, it is also possible to determine the unnecessary signal and the type of the unnecessary signal by using such a difference in the characteristics of the correlation data string.
- the present invention also relates to a GNSS receiver that receives a positioning signal using a positioning signal transmitted from a GNSS satellite as a target signal.
- the demodulator of the GNSS receiver has the above-described unnecessary signal discriminating device, tracks the target signal discriminated by the unnecessary signal discriminating device, and demodulates the target signal.
- a GNSS receiving device including the above-described unnecessary signal discriminating device is shown. And this GNSS receiver can demodulate only the received signal determined as the target signal by having the above-mentioned unnecessary signal discriminating device.
- the demodulator of the GNSS receiver of the present invention continues the discrimination process between the target signal and the unnecessary signal until the target signal is captured and tracked.
- loop processing is performed so that the target signal can be acquired while executing the above-described unnecessary signal discrimination processing. This makes it possible to capture and track the required number of target signals more reliably without capturing and tracking unnecessary signals.
- the present invention also relates to a mobile terminal equipped with the above-described GNSS receiver.
- the mobile terminal includes a positioning calculation unit that measures the position of the mobile device using the target signal acquired by the GNSS receiving device.
- interference waves, multipaths, and cross-correlation in the received signal can be accurately determined with respect to the target signal.
- only the positioning signal that is the target signal included in the received signal can be captured and tracked more reliably.
- the GNSS receiver is simply described as an example.
- various mobile terminals for example, mobile phones
- the following acquisition method and configuration can also be applied to telephones, car navigation devices, PNDs, cameras, watches, and the like.
- FIG. 1 is a block diagram showing a main configuration of a GNSS receiver 100 including a demodulator 13 having an unnecessary signal discriminating apparatus 300 according to this embodiment.
- the GNSS receiver 100 includes a positioning signal receiving antenna 11, an RF processing unit 12, a demodulation unit 13, and a positioning calculation unit 14.
- the positioning signal receiving antenna 11 receives a positioning radio wave signal transmitted from a positioning satellite such as a GPS satellite or a Galileo satellite.
- a radio wave signal for positioning (hereinafter referred to as “positioning signal”) is a signal obtained by spectrum-spreading a carrier wave having a predetermined single frequency using a spreading code and a navigation message set for each positioning satellite.
- the received signal does not necessarily contain only the positioning signal, it contains various unnecessary signals with the positioning signal, or contains only unnecessary signals, and includes more significant signals. Sometimes it is not.
- the positioning signal receiving antenna 11 converts the received signal into electrical signal conversion and outputs it to the RF processing unit 12.
- the RF processing unit 12 down-converts the frequency of the received signal, generates a correlated signal including an intermediate frequency signal and a baseband signal having a predetermined frequency, and supplies the correlated signal to the demodulation unit 13.
- the demodulator 13 includes an unnecessary signal discriminating device 300 as shown in FIG.
- the unnecessary signal discriminating apparatus 300 calculates the frequency spectrum and code phase spectrum of the correlation data sequence based on the correlation data sequence in which the correlation data obtained by the code correlation process is sequentially stored over a predetermined time.
- the unnecessary signal discriminating apparatus 300 discriminates an unnecessary signal included in the correlated signal based on the received signal from these spectra. Then, based on the determination result, the demodulation unit 13 captures and tracks a received signal having a significant level that is not determined as an unnecessary signal as a positioning signal (target signal), and despreads the received signal.
- the basic acquisition processing of the code phase and the basic tracking loop processing of the code phase and the carry phase can use known ones, and the description thereof is omitted.
- the demodulator 13 When successful in steady tracking, the demodulator 13 provides the positioning calculator 14 with data obtained by despreading using the obtained code phase and carrier frequency information, and the pseudo distance calculated from the code phase and carrier frequency information. .
- the demodulator 13 continuously performs acquisition and tracking including such unnecessary signal discrimination processing so that the number of positioning signals necessary for positioning can be constantly tracked.
- the positioning calculation unit 14 acquires a navigation message based on the despread signal on which the navigation message from the demodulation unit 13 is superimposed.
- the positioning calculation unit 14 performs a positioning calculation based on the navigation message, the pseudo distance from the demodulation unit 13, the carrier frequency information, and the like, and calculates the position of the positioning device.
- the GNSS receiver 100 performs capture and tracking using a received signal having a significant level that has not been determined as an unnecessary signal, so that accurate demodulation can be performed.
- a highly accurate positioning result can be obtained from such an accurate demodulation result.
- a highly accurate positioning result can be constantly obtained.
- FIG. 2 is a block diagram showing the main configuration of the unnecessary signal discriminating apparatus 300.
- the unnecessary signal discriminating apparatus 300 includes a code generator 30, a code delay unit 31, correlators 321 to 32n, buffers 331 to 33n, FFT processing units 341 to 34n, and a discriminating unit 35.
- “n” indicates the number of channels that can be processed in parallel corresponding to the number of positioning satellites that can be captured and tracked as a device, and is a predetermined positive number.
- the code generator 30, the code delay unit 31, and the correlators 321 to 32n are used at the time of the code capturing process and the code tracking process. Further, the correlators 321 to 32n, the buffers 331 to 33n, and the FFT processing units 341 to 34n correspond to the “correlation data string acquisition unit” of the present invention.
- the code generator 30 generates a replica code for the spreading code assigned to each positioning satellite at a designated timing if it is acquired, and outputs it to the code delay unit 31.
- the code generator 30 generates the replica code based on the code phase information set by the code NCO (not shown) based on the tracking result of the code tracking loop (not shown) at the time of tracking, and sends it to the code delay unit 31. Output.
- the code delay unit 31 shifts the replica code for each channel to each correlator 321 to 32n for each predetermined sampling timing while shifting the code for each predetermined code phase amount.
- the correlators 321 to 32n generate correlation data by multiplying the correlated signal based on the received signal and the replica code, and output the correlation data to the buffers 331 to 33n, respectively. For example, the correlator 321 multiplies the correlated signal and the first replica code to generate first correlation data, and outputs the first correlation data to the buffer 331. Similarly, the correlator 322 multiplies the correlated signal and the second replica code to generate second correlation data, and outputs the second correlation data to the buffer 332. Correlators 333 to 33n also perform similar correlation processing.
- the buffers 331 to 33n sequentially store the input correlation data along the time axis, and output 2 m pieces (m is a predetermined positive number) to the FFT processing units 341 to 34n at predetermined timings.
- the buffer 331 sequentially stores the first correlation data and outputs 2 m pieces of data to the FFT processing unit 341.
- the buffers 332 to 33n execute similar buffer processing.
- the buffers 331 to 33n output the correlation data string to the determination unit 35 together with the FFT processes 341 to 34n.
- the FFT processing units 341 to 34n perform FFT (Fast Fourier Transform) processing using the sequence of correlation data input along the time axis input from the buffers 331 to 33n, and obtain the frequency spectrum and code phase spectrum of the correlation data. To do.
- the FFT processes 341 to 34n output the acquired frequency spectrum and code phase spectrum to the determination unit 35.
- the FFT process 341 obtains a first frequency spectrum and a code phase spectrum by performing an FFT process on the first correlation data string, and outputs the first frequency spectrum and the code phase spectrum to the determination unit 35.
- the same frequency conversion processing is executed for the FFT processing 342 to 34n.
- a frequency spectrum may be acquired using simple DFT (discrete Fourier transform) processing, wavelet transform processing, or the like. .
- the discriminating unit 35 discriminates an unnecessary signal based on the frequency spectrum and code phase spectrum of the correlation data from the FFT processes 341 to 34n.
- FIG. 3 is a flowchart showing an unnecessary signal determination processing flow.
- FIG. 4 is a diagram illustrating a characteristic example representing the characteristic on the code phase axis and the characteristic on the frequency axis of the correlation data string based on the target signal and the correlation data based on the unnecessary signal.
- 4A shows the correlation data of the target signal
- FIG. 4B shows the correlation data of the interference wave of the unnecessary signal
- FIG. 4C shows the multipath correlation data of the unnecessary signal
- FIG. (D) shows correlation data of unnecessary signal cross-correlation.
- FIGS. 4A to 4D show the characteristics of the correlation data string along one axis of the code phase axis and the frequency axis, and the correlation data string over two axes orthogonal to the code phase axis and the frequency axis.
- the characteristics of The characteristics of the correlation data string on the code phase axis shown in FIGS. 4A to 4D indicate a specific frequency, and the characteristics of the correlation data string on the frequency axis indicate a specific one.
- One code phase is shown.
- processing for one channel for example, a system passing through the correlator 321, the buffer 331, and the FFT processing unit 341 will be described. It is executed for the following channels.
- the determination unit 35 acquires the correlation data string on the code phase axis and the correlation data string on the frequency axis, that is, the code phase spectrum and frequency spectrum of the correlation data (S101).
- the determining unit 35 determines whether or not the correlation data string in the two-dimensional region obtained from the code phase axis and the frequency axis is equal to or greater than the threshold Th (S101 ⁇ S102).
- the determination unit 35 determines that the received signal is not significant during the period of these correlation data strings (S120). This is because a positioning signal that can reliably execute acquisition and tracking processing needs to exceed a threshold Th set in a two-dimensional region as shown in FIG. In other words, if it is determined that the correlation data signal exceeds the threshold value Th and is not an unnecessary signal as described below, the capture and tracking process can be executed reliably.
- the determination unit 35 detects a significant peak on the frequency axis for each code phase that is correlation data equal to or greater than the threshold Th. Then, the determination unit 103 detects whether there is a significant peak at a location where the correlation level is high on the code phase axis at the peak frequency (S103). Note that the notable peak indicates that the correlation data has a local maximum value greater than or equal to a predetermined level difference with respect to the phase region before and after the code phase axis, and the determination unit 35 performs a differentiation process on the characteristics of the code phase axis. By performing the above, it is possible to detect the maximum value and obtain a remarkable peak.
- the discriminating unit 35 determines that the frequency is an interference wave (S140). This is based on the characteristics of the interference wave.
- an interference wave for example, a communication signal of another communication system can be considered. As shown in FIG. 4B, a peak appears at the frequency position of the communication signal on the frequency axis, but the target on the code phase axis. The level of the correlation data with the spreading code of the positioning signal to be constantly increased, and no significant peak appears.
- the determination unit 35 detects a prominent peak on the code phase axis (S104: Yes), it similarly determines the interference wave for another frequency at which the level of the correlation data equal to or higher than the threshold Th is detected. It performs (S105: No-> S103).
- the determination unit 35 determines the interference wave for all frequencies for which the level of the correlation data equal to or greater than the threshold Th is detected (S105: Yes)
- the determination unit 35 performs the determination for all the frequencies within the determination range and for all the code phase shifts. It is determined whether the number of peaks is one.
- the determining unit 35 determines that the peak is due to a significant positioning signal (S106: Yes).
- the determination unit 35 proceeds to a flow for determining the type of unnecessary signal from the positional relationship between the peaks on the code phase axis and the frequency axis and the number of peaks ( S106: No).
- the determination unit 35 determines that the path is multipath. (S161). This is based on multipath characteristics. Multipath is caused not only by a positioning signal from a single positioning satellite being directly received, but also by being reflected on a building or the like and received with a delay. Therefore, in multipath, as shown in FIG. 4C, the same code phase does not appear on a single frequency axis, and two correlation data level peaks appear at positions close to the code phase axis. Arise.
- the determination unit 35 may have three peaks on the code phase axis, each of the three peaks may exist independently with a certain code phase difference, and the number of peaks on the frequency axis may be three. If (S160: No), it is determined that cross-correlation occurs (S162). This is based on the characteristics of cross correlation. Cross-correlation is caused by receiving a positioning signal from a satellite different from the target positioning satellite. That is, since a plurality of codes are received by receiving positioning signals from a plurality of positioning satellites, peaks on the code phase axis appear independently. Further, since the positioning satellites are at different positions with respect to the GNSS signal receiving apparatus 100 and are moving at different relative speeds, the Doppler frequency is different for each positioning satellite. Thereby, a plurality of peaks also appear on the frequency axis.
- the determination unit 35 when the unintentional received signal, unnecessary signal, and significant positioning signal are determined, and when the unnecessary signal is determined to be interference wave, multipath, and cross-correlation, the determination unit 35 outputs the determination result to the demodulation unit 13. (S108).
- the demodulator 13 performs reception signal acquisition and tracking processing according to the determination result.
- an unnecessary signal can be determined for a significant positioning signal. At this time, since it does not depend solely on the C / N of the received signal, it can be reliably determined even if the level of the unnecessary signal is high.
- the configuration and processing of the present embodiment it is possible to accurately determine whether the unnecessary signal is a disturbance wave, multipath, or cross-correlation as well as a category of unnecessary signal. it can.
- FIG. 5 is a flowchart showing an unnecessary signal determination processing flow of the present embodiment.
- FIG. 6 is a diagram for explaining a comparison process between the reference characteristic and the actual measurement characteristic.
- FIG. 6A shows the relationship between the reference characteristic before correction of the reference characteristic and the actual measurement characteristic on the code phase axis and the frequency axis.
- FIG. 6B shows the relationship between the reference characteristic after correction of the reference characteristic (reference characteristic after correction) and the measured characteristic on the code phase axis and the frequency axis.
- the unnecessary signal discriminating apparatus stores, as reference characteristics, a correlation data string in a two-dimensional region of a code phase axis and a frequency axis corresponding to a target positioning signal obtained by correlating a replica code in advance. .
- the reference characteristics are set and stored for each positioning satellite, and the following processing is performed for each reference satellite corresponding to each positioning satellite. To be executed.
- the discriminating unit 35 acquires a correlation data string on the code phase axis and a correlation data string (measured characteristic) on the frequency axis obtained by correlation processing between the received signal and the replica code (S201).
- the determination unit 35 determines whether or not the peak level is equal to or higher than the threshold Th with respect to the correlation data string (measured characteristics) in the two-dimensional region between the code phase axis and the frequency axis based on the received signal (S201 ⁇ S202).
- the determination unit 35 determines that the correlation data string is not a significant reception signal but an inadvertent reception signal (S220).
- the determination unit 35 determines that the peak level of the actual measurement characteristic is equal to or greater than the threshold Th (S202: Yes)
- the correlation data string of the actual measurement characteristic acquired from the received signal and a reference based on the previously stored positioning signal Compare with the correlation data string of the characteristic.
- the determination unit 35 first performs level matching correction between the actually measured characteristic and the reference characteristic. Specifically, the determination unit 35 acquires the peak level of the reference characteristic and the peak level of the actual measurement characteristic on the code phase axis, and as shown in FIG. Then, the level of each correlation data of the reference characteristic is corrected (S203). In this description, the level of the reference characteristic is corrected, but it can be dealt with by correcting the measured characteristic.
- the discriminating unit 35 compares the two-dimensional correlation data of the measured characteristics with the two-dimensional correlation data of the reference characteristics after level correction (hereinafter referred to as “corrected reference characteristics”) and is similar.
- the degree is calculated (S204 ⁇ S205).
- this comparison method for example, cross-correlation processing between the measured characteristic and the corrected reference characteristic, or comparison based on a difference value or ratio between frequency correlation data at each code phase in the measured characteristic and the corrected reference characteristic It may be a value.
- the similarity is calculated based on an average value or a variance (standard deviation) of the difference values between the respective correlation data.
- the similarity is set to be higher as the average value of the difference values is closer to “0” and the variance and the standard deviation are higher.
- the determining unit 35 determines that the received signal to be determined is a positioning signal if the similarity is equal to or greater than a previously stored determination threshold (S206: Yes). On the other hand, if the two-dimensional similarity is less than the threshold, the determination unit 35 determines that the signal is an unnecessary signal (S206: No ⁇ S260).
- the determination unit 35 calculates a one-dimensional similarity in units of frequency axis and code phase axis.
- the similarity in each axis unit may be calculated at the same time as the above-described two-dimensional similarity is calculated.
- the discriminating unit 35 detects the type of unnecessary signal based on the similarity on the frequency axis and the similarity on the code phase axis (S261).
- the interference wave has the characteristics shown in FIG. 4B, the characteristics shown in FIG. 4A showing the positioning signal are completely different on the code phase axis and have no similarity at all. Furthermore, since the peak frequency is different on the frequency axis, there is almost no similarity. For this reason, when the similarity on the frequency axis and the code phase axis is low, especially when the similarity on the code phase axis is significantly low, it can be determined as an interference wave.
- the multipath has the characteristics shown by the solid line in FIG. 4C and FIG. 6, the characteristics in FIG. 4A showing the positioning signal are similar in the frequency axis, and the similarity in the frequency axis is determined by the positioning. It is almost the same as the signal.
- the code phase axis has two adjacent peaks, the characteristic differs from that of the positioning signal, and the similarity on the code phase axis is slightly lower than that of the positioning signal.
- the similarity on the frequency axis is equal to or higher than the threshold and is as high as that of the positioning signal, and the similarity on the code phase axis is low in a predetermined range, that is, low compared to the positioning signal, the level of similarity decrease If there is little, it can be determined as multipath.
- cross-correlation has the characteristics shown in FIG. 4 (D)
- the characteristics shown in FIG. 4 (A) showing the positioning signal are low in similarity on both the frequency axis and the code phase axis. More specifically, in cross correlation, since there are three adjacent peaks on the frequency axis, the similarity on the frequency axis is slightly lower than the positioning signal. On the other hand, since the code phase axis has three independent peaks at positions separated from the axis, the degree of similarity is further reduced as compared with the case of multipath.
- a first frequency axis threshold and a second frequency axis threshold lower than the first frequency axis threshold are set.
- the threshold for the first frequency axis is calculated in advance as a similarity in the case of multipath and a similarity in the case of cross-correlation, and is set to a predetermined value between these similarities.
- the second frequency axis threshold value is set to a predetermined value between the similarities in the case of cross-correlation and the similarity in the case of interference waves.
- the threshold value on the first code phase axis is calculated in advance for the similarity in the case of multipath, the similarity in the case of being a positioning signal, and a predetermined value between these similarities Set to.
- the threshold value of the second code phase axis is set to a predetermined value between these similarities after calculating the similarity in the case of multipath and the similarity in the case of cross-correlation. Furthermore, the threshold value of the third code phase axis is set to a predetermined value between the similarities in the case of cross-correlation and the similarity in the case of interference waves.
- the similarity on the frequency axis and the similarity on the code phase axis are compared with each threshold value, and the multipath, cross-correlation, or interference wave is determined based on the level relationship with respect to each threshold value.
- the judging unit 35 obtains the judgment result as in the first embodiment. 13 (S207).
- the demodulator 13 performs reception signal acquisition and tracking processing according to the determination result.
- FIG. 7A is a diagram illustrating a state in which the above-described reference characteristic is stored as two-dimensional correlation data of two orthogonal axes of the code phase axis and the frequency axis
- FIG. 7B is a reception including the above-described multipath. It is a figure which shows the two-dimensional correlation data of the measured characteristic of a signal.
- FIG. 7C is a diagram showing two-dimensional correlation data of the corrected reference characteristic
- FIG. 7D is a diagram showing two-dimensional data of a difference result between the actually measured characteristic and the corrected reference characteristic.
- Such two-dimensional data is sampled at a predetermined frequency interval on the low frequency side and the high frequency side with the frequency of the target signal as f00 with one axis as the frequency axis, and replicated with respect to the target signal with the other axis as the code phase axis.
- This is data obtained by sampling at a predetermined code phase difference interval on the side where the code phase advances and the side where the code phase advances, assuming c00 as the code timing at which an ideal correlation peak is obtained when the code is correlated.
- the determination unit 35 obtains the reference characteristics shown in FIG. The level of the entire two-dimensional correlation data of the reference characteristic so that the correlation value of the frequency f00 and code phase c00 of the two-dimensional correlation data matches the correlation value of the frequency f00 and code phase c00 of the two-dimensional correlation data of the measured characteristics. Correct. Thereby, the determination unit 35 acquires the two-dimensional correlation data of the corrected reference characteristic as shown in FIG.
- the discriminating unit 35 uses the two-dimensional correlation data of the actually measured characteristics shown in FIG. 7B and the two-dimensional correlation data of the corrected reference characteristics shown in FIG.
- the data level is differentiated for each element data, and two-dimensional correlation data having a difference value as shown in FIG. 7D is calculated.
- the determination unit 35 determines whether the received signal corresponding to the actual measurement characteristic is the target signal or not from the two-dimensional data of the difference value. Specifically, if the received signal is a target signal, ideally, the level of all element data of the two-dimensional data of the difference value is “0”. Therefore, the determination unit 35 acquires the total value or average value of the element data levels of the two-dimensional data of the difference value, and if the total value or average value is less than a predetermined threshold value close to “0”, the target signal and If it is determined that the signal is equal to or greater than a predetermined threshold value, the signal is determined to be an unnecessary signal. At this time, the determination unit 35 may calculate variance and standard deviation and include them in the determination criterion.
- the determination unit 35 calculates a total value or an average value of the difference values for each frequency (for example, f01 or f20 in FIG. 7), or performs a difference for each code phase (for example, c10 or c02 in FIG. 7).
- the type of unnecessary signal is determined by calculating a total value or an average value of the values. For example, in the case of multipath, as shown in FIG. 6B and FIG. 7B, different characteristics are generated with respect to the code phase axis, and a region where the difference value increases on the side where the code phase is delayed occurs. Therefore, if the average value or the total value of the difference values for each code phase is calculated, data that is equal to or greater than the threshold appears on the code phase delay side. The determination unit 35 detects this to determine that the unnecessary signal is multipath.
- an unnecessary signal can also be determined by comparing with a preset reference characteristic. If the method of this embodiment is used, it is possible to determine an unnecessary signal based on similarity without depending on a change in reception level.
- the difference value is used as the similarity, but any calculation value that can detect a difference between two correlation data may be used, and a division value or the like may be used.
- the cross-correlation is determined after the multi-path is determined.
- the order may be reversed.
- the method of frequency conversion of the result of correlation processing between the replica code and the received signal is shown.
- the received signal is decomposed into a plurality of frequency band components, even if each frequency component and the replica code are subjected to correlation processing, it is possible to obtain interphase data by two axes of the code axis and the frequency axis as described above. it can.
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Abstract
Description
GNSS受信装置100は、測位信号受信アンテナ11、RF処理部12、復調部13、測位演算部14を備える。
本実施形態の不要信号判別装置は、判別部35の判別処理が異なるのみで、他の構成は第1の実施形態と同じであるので、必要箇所についてのみ説明する。
図5は、本実施形態の不要信号判別処理フローを示すフローチャートである。
図6は、基準特性と実測特性との比較処理を説明するための図であり、図6(A)が基準特性補正前の基準特性と実測特性とのコード位相軸および周波数軸での関係を示し、図6(B)が基準特性補正後の基準特性(補正後基準特性)と実測特性とのコード位相軸および周波数軸での関係を示す。
Claims (24)
- 所定の拡散コードでコード変調された目的信号を含む受信信号から不要信号を判別する不要信号判別装置であって、
前記拡散コードに対するレプリカコードと前記受信信号との相関データから、コード位相軸における相関データ列と周波数軸における相関データ列を取得する相関データ列取得部と、
前記コード位相軸における相関データ列と前記周波数軸における相関データ列とに基づいて前記不要信号を判別する判別部と、
を備えた不要信号判別装置。 - 請求項1に記載の不要信号判別装置であって、
前記相関データ列取得部は、前記相関データを所定時間に亘り記憶し、該記憶した相関データを周波数領域のデータに変換することで、前記コード位相軸における相関データ列と前記周波数軸における相関データ列とを取得する、不要信号判別装置。 - 請求項1または請求項2に記載の不要信号判別装置であって、
前記判別部は、
前記目的信号を前記レプリカコードで相関処理した相関データのコード位相軸における相関データ列と周波数軸における相関データ列とを基準特性として予め記憶しており、
該基準特性と、前記受信信号を前記レプリカコードで相関処理した相関データの前記コード位相軸における相関データ列および前記周波数軸における相関データ列に基づく実測特性と、を比較して前記不要信号を判別する、不要信号判別装置。 - 請求項3に記載の不要信号判別装置であって、
前記判別部は、前記基準特性と前記実測特性とにおける相関データのピークレベルを一致させるように、前記基準特性もしくは前記実測特性の相関データを補正し、補正後の特性を用いて前記コード位相軸および前記周波数軸における類似度を算出することで、前記不要信号を判別する、不要信号判別装置。 - 請求項4に記載の不要信号判別装置であって、
前記判別部は、
周波数軸での類似度とコード位相軸での類似度の双方を用いて、前記不要信号の種類を、マルチパス、クロスコリレーション、妨害波に判定する、不要信号判別装置。 - 請求項4または請求項5に記載の不要信号判別装置であって、
前記判別部は、前記類似度として、前記補正後の特性間の差分値を算出する、不要信号判別装置。 - 請求項1に記載の不要信号判別装置であって、
前記判別部は、
前記コード位相軸における相関データのピークレベルの個数および前記周波数軸における相関データのピークレベルの個数およびピーク間の位置関係に基づいて、前記不要信号を、妨害波、マルチパス、またはクロスコリレーションのいずれかに判別する、不要信号判別装置。 - 所定の拡散コードでコード変調された目的信号を含む受信信号から不要信号を判別する不要信号判別方法であって、
前記拡散コードに対するレプリカコードと前記受信信号との相関データから、コード位相軸における相関データ列と周波数軸における相関データ列を取得する工程と、
前記コード位相軸における相関データ列と前記周波数軸における相関データ列とに基づいて前記不要信号を判別する工程と、
を有する不要信号判別方法。 - 請求項8に記載の不要信号判別方法であって、
前記相関データ列を取得する工程は、前記相関データを所定時間に亘り記憶し、該記憶した相関データを周波数領域のデータに変換することで、前記コード位相軸における相関データ列と前記周波数軸における相関データ列とを取得する、不要信号判別方法。 - 請求項8または請求項9に記載の不要信号判別方法であって、
前記不要信号を判別する工程は、
前記目的信号を前記レプリカコードで相関処理した相関データのコード位相軸における相関データ列と周波数軸における相関データ列とを基準特性として予め記憶しており、
該基準特性と、前記受信信号を前記レプリカコードで相関処理した相関データの前記コード位相軸における相関データ列および前記周波数軸における相関データ列に基づく実測特性と、を比較して前記不要信号を判別する、不要信号判別方法。 - 請求項10に記載の不要信号判別方法であって、
前記不要信号を判別する工程は、前記基準特性と前記実測特性とのコード位相軸でのピークレベルを一致させるように、前記基準特性もしくは前記実測特性の相関データを補正し、補正後の特性を用いて前記コード位相軸および前記周波数軸における類似度を算出することで、前記不要信号を判別する、不要信号判別方法。 - 請求項11に記載の不要信号判別方法であって、
前記不要信号を判別する工程は、周波数軸での類似度とコード位相軸での類似度の双方を用いて、前記不要信号の種類を、マルチパス、クロスコリレーション、妨害波に判定する、不要信号判別方法。 - 請求項11または請求項12に記載の不要信号判別方法であって、
前記不要信号を判別する工程は、前記類似度として、前記補正後の特性間の差分値を算出する、不要信号判別方法。 - 請求項8に記載の不要信号判別方法であって、
前記不要信号を判別する工程は、前記コード位相軸における相関データのピークレベルの個数および前記周波数軸における相関データのピークレベルの個数およびピーク間の位置関係に基づいて、前記不要信号を、妨害波、マルチパス、またはクロスコリレーションのいずれかに判別する、不要信号判別方法。 - 所定の拡散コードでコード変調された目的信号を含む受信信号から不要信号を判別するための不要信号判別プログラムであって、
前記拡散コードに対するレプリカコードと前記受信信号との相関データから、コード位相軸における相関データ列と周波数軸における相関データ列を取得する処理と、
前記コード位相軸における相関データ列と前記周波数軸における相関データ列とに基づいて前記不要信号を判別する処理と、
を含む不要信号判別プログラム。 - 請求項15に記載の不要信号判別プログラムであって、
前記相関データ列を取得する処理は、前記相関データを所定時間に亘り記憶し、該記憶した相関データを周波数領域のデータに変換することで、前記コード位相軸における相関データ列と前記周波数軸における相関データ列とを取得する、不要信号判別プログラム。 - 請求項15または請求項16に記載の不要信号判別プログラムであって、
前記不要信号を判別する処理は、
前記目的信号を前記レプリカコードで相関処理した相関データのコード位相軸における相関データ列と周波数軸における相関データ列とを基準特性として予め記憶しており、
該基準特性と、前記受信信号を前記レプリカコードで相関処理した相関データの前記コード位相軸における相関データ列および前記周波数軸における相関データ列に基づく実測特性と、を比較して前記不要信号を判別する、不要信号判別プログラム。 - 請求項17に記載の不要信号判別プログラムであって、
前記不要信号を判別する処理は、前記基準特性と前記実測特性とのコード位相軸でのピークレベルを一致させるように、前記基準特性もしくは前記実測特性の相関データを補正し、補正後の特性を用いて前記コード位相軸および前記周波数軸における類似度を算出することで、前記不要信号を判別する、不要信号判別プログラム。 - 請求項18に記載の不要信号判別プログラムであって、
前記不要信号を判別する処理は、周波数軸での類似度とコード位相軸での類似度の双方を用いて、前記不要信号の種類を、マルチパス、クロスコリレーション、妨害波に判定する、不要信号判別プログラム。 - 請求項18または請求項19に記載の不要信号判別プログラムであって、
前記不要信号を判別する処理は、前記類似度として、前記補正後の特性間の差分値を算出する、不要信号判別プログラム。 - 請求項15に記載の不要信号判別プログラムであって、
前記不要信号を判別するプログラムは、前記コード位相軸における相関データのピークレベルの個数および前記周波数軸における相関データのピークレベルの個数およびピーク間の位置関係に基づいて、前記不要信号を、妨害波、マルチパス、またはクロスコリレーションのいずれかに判別する、不要信号判別プログラム。 - 前記目的信号としてGNSS衛星から送信される測位信号を用い、当該測位信号を受信するGNSS受信装置であって、
請求項1乃至請求項7のいずれかに記載の不要信号判別装置を有し、該不要信号判別装置で判別した前記目的信号を追尾して該目的信号の復調を行う復調部を備えたGNSS受信装置。 - 請求項22に記載のGNSS受信装置であって、
前記復調部は、前記目的信号が捕捉、追尾されるまでは、該目的信号と前記不要信号との判別処理を継続する、GNSS受信装置。 - 自装置位置を利用するアプリケーションを実行する移動端末であって、
請求項22または請求項23に記載のGNSS受信装置を備え、
該GNSS受信装置で取得した前記目的信号を用いて、自装置位置を測位する測位演算部を、備えた移動端末。
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