JP2020201282A - Navigation satellite system receiver, navigation satellite signal processing method, and program - Google Patents

Abstract

To provide a navigation satellite system receiver with which it is possible to realize high-accuracy time synchronization or positioning even in an environment where a navigation satellite signal receive state is not good.SOLUTION: A navigation satellite system receiver comprises: a navigation satellite signal receive unit 2 for calculating a received position and received time on the basis of the navigation satellite signals simultaneously received from four or more navigation satellites; and a control unit 4 for exercising control so as to calculate the initial value of received position and the trajectory position of each navigation satellite on the basis of each navigation satellite signal, calculate the arrival time of each navigation satellite signal on the basis of the calculated received position and trajectory position and the time information included in each navigation satellite signal, extract a navigation satellite signal on the basis of the calculated arrival time, calculate the received position on the basis of the extracted navigation satellite signal, recursively perform a process of calculating the arrival time and a process of extracting the navigation satellite signal using the calculated received position, and perform a positioning process or a time synchronization process on the basis of the navigation satellite signal extracted at termination of the recursion.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for realizing highly accurate time synchronization and positioning even in an environment in which a navigation satellite signal cannot always be received as a visible satellite signal in a navigation satellite system.

GPS (Global Positioning System) and all other means to realize highly accurate time (timing) synchronization between base stations, which is required for Time Division Duplex (TDD) mobile communication systems. The use of the Global Navigation Satellite System (GNSS) is expanding. The GNSS satellite (navigation satellite) is equipped with a highly accurate atomic clock synchronized with Coordinated Universal Time (UTC), and transmits navigation satellite signals synchronized with this by radio waves, but at any point on the earth. By receiving the navigation satellite signal, it becomes possible to synchronize the time with UTC with high accuracy.

Since the navigation satellite signal transmitted from the navigation satellite causes a propagation delay before reaching the reception point, the signals of at least four navigation satellites are simultaneously received in order to correct the delay time, and the signal reception position 3 It is necessary to specify four parameters of the three-dimensional coordinate information (x, y, z) and the time difference (Δt) between the satellite and the receiver clock. In the case of GPS, more than 24 navigation satellites are operated in six semi-synchronous orbits with a cycle of about 12 hours, and of these, in order to constantly realize positioning and time synchronization. It is necessary to select an environment that can constantly capture at least four navigation satellites.

When using GNSS for the purpose of highly accurate time synchronization, the cause is that the line-of-sight space of the navigation satellite signal around the antenna that receives the navigation satellite signal (hereinafter referred to as the navigation satellite antenna) is blocked by buildings, trees, etc. Therefore, the number of satellite (hereinafter, visible satellite) signals that can be received as a direct wave may be limited. In general, base stations for mobile communication systems tend to be installed at higher densities in urban areas where traffic demand is high, but in urban areas, areas where four or more navigation satellite signals can always be captured as direct waves are limited. Will be done. Therefore, it is difficult to constantly capture a sufficient number of navigation satellite signals as direct waves, and it is a problem to realize highly accurate and stable time synchronization even in an environment where the reception state of navigation satellite signals is not good. It has become.

When performing positioning using a navigation satellite signal or time synchronization with a navigation satellite signal, it is accurate to select an open reception environment that can receive more visible satellite signals received as direct waves. It is effective in improving. Furthermore, it is expected that the accuracy of positioning and time will be further improved if the visible satellites are evenly distributed over the sky. An index called DOP (Dilution Of Precision) is often used as an index showing the deterioration of accuracy due to the bias of the satellite arrangement in the sky.

Other factors that affect the accuracy of positioning and time synchronization using navigation satellite signals are reflected waves and diffracted waves (so-called multi) generated by reflection and diffraction of navigation satellite signals by structures and the ground around the reception position. (Pass signal) reception can be mentioned.

FIG. 13 shows a schematic diagram for explaining the generation state of the multipath signal. As shown in FIG. 13, the multipath signal of a case with a direct wave (multipath signal of a visible satellite signal) and a case without a direct wave (a satellite that cannot be received as a direct wave (hereinafter, invisible satellite)) is a multipath signal. ) There are types. Regarding the former, in the normal case where the reception strength of the direct wave is larger than the reception strength of the multipath signal, measures to effectively reduce the influence of the multipath signal by the correlation signal processing in the navigation satellite signal receiver have been studied so far. (See Non-Patent Document 1). On the other hand, regarding the latter multipath signal of an invisible satellite that does not involve a direct wave, it is difficult to remove the influence unless the navigation satellite signal is used for positioning and time synchronization, so positioning accuracy and time synchronization accuracy. Has a large effect on.

14 and 15 show an example of the reception status of the multipath signal. As a result of installing GPS satellite antennas in an environment surrounded by buildings as shown in FIG. 14 and receiving GPS satellite signals, as shown in the upper part of FIG. 15, it opens on the sky image at the GPS satellite antenna installation position. In addition to the visible satellite signals located in space (# 6, # 9 in the example of FIG. 15), many of the invisible satellite signals shielded by the structure (# 2, # 3, # 5 in the example of FIG. 15) It was confirmed that # 7, # 12, # 17, # 19, # 23, # 25) were received as multipath signals. In addition, as shown in the lower part of FIG. 15, the reception characteristics of GPS satellite signals over time are also received assuming open sky rather than the number of visible satellites obtained by simulation from an open space considering the structure around the GPS antenna. A number of GPS satellite signals close to the number of satellites was received. Here, "open sky" means an open reception environment in the sky with no surrounding obstacles.

The multipath signal has a longer propagation path length than the direct wave and reaches the navigation satellite antenna with a propagation delay. The larger the distance from the navigation satellite antenna to the reflection point, the larger the propagation delay time difference of the reflected wave with respect to the direct wave, and the larger the measurement error of the pseudo distance. Here, the pseudo distance refers to the distance obtained by multiplying the difference between the time when the navigation satellite signal is transmitted and the time when the navigation satellite signal receiver receives the navigation satellite signal by the speed of light. If the measurement error of the pseudo distance becomes large, the time synchronization accuracy and the positioning accuracy deteriorate.

16 shows the difference between the time obtained by receiving the GPS satellite signal in the environment where the multipath signals of FIGS. 14 and 15 are generated and the time obtained by receiving the GPS satellite signal in the nearby open sky environment (time error). The configuration of the experimental system used to measure is shown. The GPS satellite signals received in each environment are input to two GPS receivers of the same model, and the phase difference of the 1PPS (Pulse Per Second) signal, which is the timing output signal of the generated time information, is measured as a time error. It was measured over time with a device. By this method, the degree of deterioration of the time synchronization accuracy due to the reception of the multipath signal can be quantitatively measured. As a result, as shown in FIG. 17, the time generated from the GPS satellite signal received in the environment where the multipath signal is generated is 250 ns or more at the maximum with respect to the time generated from the GPS satellite signal received in the open sky environment. It was confirmed that it would be delayed.

As explained above, in order to improve the accuracy of time synchronization and positioning by navigation satellite signals in a non-ideal reception environment where the surroundings of the reception position are blocked by structures, visible satellite signals in dispersed positions in the sky It is necessary to receive as much as possible and effectively eliminate the influence of the multipath signal.

In order to receive more visible satellite signals located in the open space above the sky, in addition to selecting the open reception position in the open space as much as possible, the use called multi-GNSS that uses multiple navigation satellite systems together. The form is valid.

On the other hand, various methods have been studied so far as methods for reducing the influence of multipath signals.

When the multipath signal is reflected by a building or the like, the rotation direction of the circularly polarized wave characteristic of the navigation satellite signal is reversed. By utilizing the inversion of the circularly polarized wave characteristic due to this reflection and providing the navigation satellite antenna with an isolation characteristic depending on the circularly polarized wave characteristic, the signal intensity of the reflected wave reflected odd times can be attenuated. In addition, the vertical directivity of the navigation satellite antenna can attenuate the signal strength of the reflected wave from the ground or a low elevation angle. The above is one of the methods for reducing the influence of the multipath signal by the navigation satellite antenna.

On the other hand, as a method of reducing the influence of the multi-pass signal realized in the navigation satellite signal receiving device, positioning is performed by the reception strength of the received navigation satellite signal and the signal-to-noise ratio (SNR). A method of relatively weighting the navigation satellite signal used for time synchronization, or a method used for positioning and time synchronization based on the reception strength of the received navigation satellite signal and the signal-to-noise ratio (SNR) threshold. A method of selecting satellite signals can be mentioned. The latter method is called an SNR mask. When the navigation satellite signal is reflected and diffracted by the building around the reception position, the signal strength is attenuated according to the material and reflection of the building and the angle of diffraction, so the visible satellite signal received as a direct wave is reflected and diffracted. It is expected that the signal-to-noise ratio (SNR) is relatively large compared to the invisible satellite signal accompanied by. By selecting or weighting the navigation satellite signal based on the signal-to-noise ratio (SNR) of the navigation satellite signal received there, the contribution of the visible satellite signal in positioning and time synchronization is enhanced, and the accuracy is improved. There is expected. FIG. 17 shows the result of measuring the time synchronization accuracy when the navigation satellite signal is selected by the threshold value of CNR (Carrier-To-Noise Ratio), which is one of the indicators of the signal-to-noise ratio (SNR). In the measurement of FIG. 17, as a result of selecting a GPS satellite signal having a CNR of 35 dB-Hz or more from the received GPS satellite signal and generating the time, it was confirmed that the time error was significantly improved to 100 ns or less.

A method for reducing the influence of the second multipath signal realized in the navigation satellite signal receiver will be described. As shown in FIG. 18, since the height of the structure around the navigation satellite antenna that reflects and diffracts the navigation satellite signal is finite, the ease of receiving the multipath signal depends on the elevation angle of the navigation satellite signal. Since the navigation satellite signal with a large elevation angle with respect to the distance between the building and the installation position of the navigation satellite antenna is reflected at a small reflection angle on the vertical wall surface of the building, the reflected signal propagates toward the ground and the navigation satellite antenna. Does not reach. On the other hand, since the navigation satellite signal with a small elevation angle has a large reflection angle on the wall surface in the vertical direction of the building, there is a high possibility that the reflected wave with a large propagation delay time difference will reach the navigation satellite antenna as compared with the direct wave. Therefore, by filtering the navigation satellite signal by the threshold value of the elevation angle and using the navigation satellite signal with a large elevation angle for positioning and time synchronization, the visible satellite signal and the invisible satellite signal with a small propagation delay are preferentially selected and multi. It is expected to reduce the influence of the pass signal. This method is called an elevation mask. FIG. 19 shows the results of measuring the time synchronization accuracy when GPS satellite signals are selected according to the threshold value of the elevation angle in the reception environment of FIG. As shown in FIG. 19, it was confirmed that the time error was improved as the elevation threshold was increased.

The third method of reducing the influence of the multipath signal realized in the navigation satellite signal receiver is to preliminarily perform positioning / time synchronization calculation using a combination of navigation satellite signals of a subset of the received navigation satellite signals. This is a method of selecting navigation satellite signals by statistical processing. In the air control system, etc., in order to guarantee the integrity of the navigation satellite system, a method called RAIM (Receiver Autonomous Integrity Monitoring) that detects navigation satellite signals that are not in a normal operating state by such statistical signal processing and detection are performed in addition to exclusion. A method called FDE (Fault Detection and Exclusion) is used. The visible satellite signal is preferentially selected by the same statistical processing focusing on the fact that the multipath signal arrives behind the navigation satellite antenna with respect to the direct wave, and propagates when the number of visible satellites is less than four. A method for improving the time synchronization accuracy by a method of complementarily selecting an invisible satellite signal having a small delay time has been studied (see Non-Patent Document 2).

Nobuaki Kubo, "Reduction of multipath error in GPS positioning and possibility of high-precision positioning", Dissertation, Tokyokaiyo University, 2005 Masashi Yoshida et al., "Improvement of GNSS time synchronization accuracy by reducing the influence of multipath signals of invisible satellites", National Conference of Positioning Navigation Society, 2017

The following points can be mentioned as problems in the conventional method for reducing the deterioration of accuracy due to the influence of the invisible satellite signal in the positioning and time synchronization by the navigation satellite signal.

(1) Method of selecting a navigation satellite signal in a navigation satellite signal receiver (1-1) Method using an elevation angle mask A navigation satellite used for positioning and time synchronization based on a threshold value set for the elevation angle of the navigation satellite signal. The method using an elevation mask to select a signal is highly effective when the open space is close to a circular shape centered on the zenith, but in other general reception environments, the positioning and time synchronization accuracy are improved. It may also eliminate visible satellite signals that contribute to. For example, in the reception environment of FIG. 19, when the elevation threshold is set to 40 degrees, the visible satellite signal located in the open space on the east side is excluded. For this reason, the navigation satellite signal used for positioning and time synchronization may not be properly selected. In addition, when the threshold setting value is strict (when the threshold elevation angle is large), there is a possibility that the number of navigation satellite signals required for positioning and time synchronization cannot be temporarily secured. On the other hand, if the threshold value is loose (the threshold elevation angle is small), the invisible satellite signal received as a multipath signal without direct waves cannot be sufficiently excluded, and the accuracy may deteriorate. There is.

(1-2) Method using SNR mask The method using the SNR mask, which sets threshold values for the received signal strength and signal-to-noise ratio of the received navigation satellite signal and selects the navigation satellite signal used for positioning and time synchronization, is optimal. The threshold value depends on the reception characteristics of the navigation satellite antenna, the installation environment of the navigation satellite antenna, the sensitivity of the navigation satellite signal receiver, the elevation angle of the navigation satellite, the superposition of interference signals, and the like. In particular, the interference signal may fluctuate the signal-to-noise ratio of the navigation satellite signal over time. The interference signal is assumed to be a jamming signal intentionally transmitted for the purpose of interfering with the reception of the navigation satellite signal, a signal used in mobile communication, etc., but the positional relationship between the interference signal source and the navigation satellite antenna and the interference signal When the intensity itself fluctuates with time, the signal-to-noise ratio of the navigation satellite signal fluctuates with time.

In the SNR mask method, when the threshold setting value is strict (when the threshold such as received signal strength and signal-to-noise ratio is large), it is necessary for positioning and time synchronization in the time zone when the number of visible satellite signals that can be received is small. There is a possibility that a large number of navigation satellite signals cannot be temporarily secured. On the other hand, when the threshold value is loose (when the threshold value such as received signal strength or signal-to-noise ratio is small), the invisible satellite signal received as a multipath signal without direct waves can be sufficiently excluded. It cannot be done and the accuracy may deteriorate.

As described above, in the method using the SNR mask, it is not always easy to set the optimum threshold value in consideration of the possibility that the level of the superimposed interference signal fluctuates with time, and it is not always easy to set the optimum threshold value for positioning and time synchronization. In some cases, it was not possible to correctly select the navigation satellite signal that was suitable for use and the navigation satellite signal that was not suitable for use.

(2) A method of receiving a navigation satellite signal in the navigation satellite signal receiver and then performing correction processing (2-1) A method of weighting based on SNR Depending on the received signal strength and signal-to-noise ratio of the received navigation satellite signal, etc. In the method of weighting the navigation satellite signals used for positioning and time synchronization during signal processing, the signals are received as multi-pass signals without direct waves, rather than the number of visible satellite signals that can be received as direct waves. When the number of invisible satellite signals is larger, the contribution of the invisible satellite signals may be relatively large, and as a result, deterioration of accuracy may not be avoided.

(2-2) Weighting method based on elevation angle In the method of weighting satellites with a large elevation angle, which are likely to be received as visible satellites, the number of satellites with a large elevation angle decreases depending on the temporal position of the satellites. However, the contribution of the invisible satellite signal may be relatively large, and as a result, deterioration of accuracy may not be avoided.

(3) Method of attenuating a navigation satellite signal that is inappropriate for use at a navigation satellite antenna (3-1) Method by polarization isolation Utilizing the fact that the rotation direction of the circularly polarized light of the reflected signal is reversed, a circle This is a method of attenuating the signal strength of a navigation satellite signal reflected an odd number of times by a navigation satellite antenna having an isolation characteristic depending on polarization. With this method, it is possible to attenuate the reception strength of the multipath signal to some extent, but it is possible to receive a signal with a strength higher than the reception sensitivity of the navigation satellite signal receiver, and the influence of the multipath signal cannot be eliminated. There is sex. For a signal that is reflected twice more, the rotation direction is further reversed and returned to the original state, so that no attenuation can be obtained. Therefore, it may not be possible to sufficiently eliminate signals that are not suitable for use in positioning and time synchronization.

(3-2) Method using a directional antenna This is a method of attenuating reflected waves from the ground or a low elevation angle by the directivity in the vertical upward direction of the navigation satellite antenna. Similar to the above, this method can attenuate the received signal strength of the reflected wave to some extent, but may not sufficiently eliminate signals that are not suitable for use.

(4) Method of selecting satellites by statistical processing The multi-GNSS usage pattern is effective in improving accuracy because a larger number of visible satellites can be secured, but the method of selecting satellites by statistical processing is effective. There is a problem that the signal processing load increases exponentially as the number of received navigation satellite signals increases. For this reason, there are cases where the calculation for satellite selection cannot be performed due to the limitation of the signal processing resource of the GNSS receiver, or the calculation time is required and the satellite selection cannot be performed in a timely manner.

As described above, in the prior arts (1) to (4), it is not possible to correctly select a navigation satellite signal suitable for use in realizing highly accurate time synchronization or positioning and a navigation satellite signal that is not suitable for use. There was something.

The present invention has been made in view of the above problems, and the reception state of the navigation satellite signal in which the open space for receiving the navigation satellite signal is limited and the invisible satellite signal is received as a multipath signal without a direct wave. It is an object of the present invention to provide a navigation satellite system receiver capable of realizing highly accurate time synchronization or positioning even in an environment where the above conditions are not good.

In order to achieve the above object, the present invention relates to four or more navigation satellite system receivers that perform at least one of positioning processing or time synchronization processing with the navigation satellite based on navigation satellite signals received from a plurality of navigation satellites. The navigation satellite signal receiver that calculates the reception position and reception time based on the navigation satellite signals received simultaneously from the navigation satellites of, and the initial value of the reception position based on each navigation satellite signal from four or more navigation satellites that can be received simultaneously. And the orbital position of each navigation satellite is calculated, the arrival time of each navigation satellite signal is calculated based on the calculated reception position and orbit position and the time information included in each navigation satellite signal, and the navigation satellite signal is calculated based on the calculated arrival time. Is extracted, the reception position is calculated based on the extracted navigation satellite signal, and the calculation process of the arrival time, the extraction process of the navigation satellite signal, and the calculation process of the reception position are recursively performed using the calculated reception position. It is characterized in that it is provided with a control unit that controls to perform positioning processing or time synchronization processing based on the navigation satellite signal extracted at the end of recurrence.

According to the present invention, it is possible to correctly select a navigation satellite signal suitable for use in time synchronization and positioning and a navigation satellite signal not suitable for use. For this reason, the open space for receiving the navigation satellite signal is limited, and the invisible satellite signal is received as a multipath signal without direct waves, and the time is highly accurate even in an environment where the reception state of the navigation satellite signal is not good. The effect of realizing synchronization and positioning is expected.

The following effects can be expected in a form in which positioning and time synchronization are performed simultaneously using four or more navigation satellite signals.

(A) In order to selectively select visible satellites and invisible satellites with smaller propagation delay as necessary without depending on the number of visible satellites in the reception environment, the optimum navigation satellite signal in the reception environment and reception time is dynamically selected. Moreover, by selecting it adaptively, the effect of realizing highly accurate time synchronization and positioning is expected.

(B) It is expected that the influence of the multipath signal is effectively eliminated without depending on the reception characteristics of the navigation satellite antenna and the performance of the navigation satellite signal receiver.

(C) By appropriately setting the parameter values according to the reception environment, not only a poor reception environment that receives a large number of multipath signals of invisible satellites with a small number of visible satellites, but also any environment including an open sky reception environment. It is expected to have the effect of stably realizing highly accurate time synchronization and positioning in the reception environment.

(D) In the present invention, in order to select at least four or more navigation satellite signals to be used for time synchronization and positioning from the received navigation satellite signals, the received signal strength, signal-to-noise ratio and elevation angle of the received navigation satellite signals are selected. There is no risk that the required number of navigation satellites cannot be secured, which has been a problem in the conventional method of setting a threshold value such as, and selecting a navigation satellite signal to be used for positioning and time synchronization.

(E) In the present invention, since it is not necessary to implement circularly polarized isolation characteristics and vertical directivity in the navigation satellite antenna, it is possible to reduce the cost of the navigation satellite antenna as a secondary effect. ..

Configuration diagram showing an example of a time synchronization device Graph showing the relationship between the tolerance value and the time synchronization accuracy Configuration diagram showing the time accuracy measurement system in the open sky reception environment Measurement result of time accuracy with respect to margin of error value in open sky reception environment Status of GPS satellite signals used for tolerance values in an open sky reception environment Measurement result of time accuracy for tolerance value in multipath reception environment Status of GPS satellite signals used with the satellite selection algorithm disabled in a multipath reception environment Status of GPS satellite signals used with the satellite selection algorithm enabled in a multipath reception environment The figure explaining the reception state of the GPS satellite signal in the open sky reception environment The figure explaining the reception state of the GPS satellite signal in the multipath reception environment. The figure explaining the relationship between the number of navigation satellite signals exceeding the CNR threshold and the margin of error value. Measurement result of positioning accuracy in multipath reception environment Schematic diagram explaining the generation status of multipath signals Diagram illustrating an environment for receiving multipath signals The figure explaining the reception situation of a multipath signal Configuration diagram showing the time accuracy measurement system in a multipath reception environment Measurement results of deterioration of time accuracy in multipath reception environment and improvement effect by SNR mask Schematic diagram showing the relationship between the elevation angle of a navigation satellite and the reflected wave Measurement results of deterioration of time accuracy in multipath reception environment and improvement effect by elevation mask

FIG. 1 shows the configuration of the entire system including the navigation satellite system receiver according to the embodiment of the present invention. In this system, a time synchronization device will be described as an example of a navigation satellite system receiver. This system includes a navigation satellite antenna 1, a navigation satellite signal reception unit 2, a time information generation unit 3, a control unit 4, and a setting unit 5. The mounting form of the time synchronization device does not matter, and it may be mounted by installing a program on the computer, or it may be mounted as a dedicated hard air device.

The navigation satellite antenna 1 is an antenna for receiving a navigation satellite signal. The navigation satellite signal receiving unit 2 is a functional unit that receives a plurality of navigation satellite signals, calculates time information at the receiving position, and outputs the time information to the time information generation unit 3. The time information generation unit 3 is a functional unit that generates time information and outputs it to the outside. The control unit 4 is a functional unit for controlling the navigation satellite signal reception unit and the time information generation unit. The setting unit 5 is a functional unit for setting various parameters of the system. The configuration and operation of each functional unit will be described in detail below.

The navigation satellite antenna 1 is connected to the navigation satellite signal receiving unit 2 by a coaxial cable or the like, and transmits the received navigation satellite signal to the navigation satellite signal receiving unit 2.

The navigation satellite signal receiving unit 2 simultaneously receives the signals of at least four navigation satellites, and receives the three-dimensional coordinate information (x, y, z) of the signal reception position and the time information received from the navigation satellites of the navigation satellite. The four parameters of the reception time information (t) corrected based on the propagation delay time from the position to the reception point are specified by calculation.

Further, the navigation satellite signal receiving unit 2 corrects the transmission delay time of the transmission line such as the coaxial cable between the navigation satellite antenna 1 and the navigation satellite signal receiving unit 2, and generates time information at the installation position of the navigation satellite antenna 1. To do.

The navigation satellite signal receiving unit 2 outputs the time information synchronized with the navigation satellite thus generated and the information about the navigation satellite used to the time information generation unit 3 and the control unit 4. As an example of time information, a timing signal in a signal format such as 1PPS (Pulse Per Second) synchronized with a navigation satellite signal and information on absolute time such as time and seconds (ToD: Time of the Day) are notified. Timecode data in a format such as NMEA0183 is used. Further, as information on the navigation satellite, the navigation satellite system type, satellite number, orientation, elevation angle, CNR, etc. in a format such as NMEA 0183 are used. On the other hand, the selection of the navigation satellite signal used for positioning and time synchronization by the navigation satellite signal receiving unit 2 is based on the instruction of the control unit 4.

The navigation satellite signal receiving unit 2 may be installed inside the device, or may use a navigation satellite signal receiving device placed outside the device. The navigation satellite signal receiving unit 2 can store the reception position information calculated by positioning with the navigation satellite signal. In that case, if it is assumed that the position of the navigation satellite antenna 1 does not move, then if at least one navigation satellite signal is received, the time synchronization can be continuously performed. It should be noted that continuous time synchronization using the stored reception position information and at least one navigation satellite signal is referred to as "position fixed mode".

The time information generation unit 3 is a functional unit that is responsible for generating time information synchronized with the navigation satellite signal, and is a predetermined standard time based on the time information supplied from the navigation satellite signal reception unit 2, which is described above. Generates a time signal synchronized with UTC. Specifically, the time information generation unit 3 is equipped with a reference frequency oscillator and a phase-locked loop (PLL) internally, and is dependent on the 1PPS signal supplied from the navigation satellite signal reception unit 2. At the same time as synchronizing the timing, time information consistent with the absolute time based on the ToD information supplied from the navigation satellite signal receiving unit 2 is generated. When the signal from the navigation satellite signal receiving unit 2 is interrupted, the time information generation unit 3 can maintain and continue the generation of the time information by self-propelling (holdover) with the reference frequency oscillator.

Further, the time information generation unit 3 plays a role of supplying time information to a device (timed synchronization device) outside the device that performs time synchronization. As the time information used at this time, in addition to the above 1PPS / ToD, the PTP (Precision Time Protocol) protocol defined in IEEE (Institute of Electrical and Electronics Engineers) 1588 version 2 is used, and Ethernet (registered trademark) is used. ), Etc., the time information may be supplied via the packet communication interface.

The control unit 4 controls the navigation satellite signal reception unit 2 and the time information generation unit 3 and receives the navigation satellite signal in order to realize an algorithm for generating time information described later based on the parameter information input to the setting unit 5. Processing such as comparison of time information output from part 2 and extraction of navigation satellites is performed.

The setting unit 5 sets various parameters necessary for the operation of the system from the outside. The parameters to be set include the correction value of the transmission delay time that occurs in the transmission line such as the coaxial cable that connects the navigation satellite antenna 1 and the navigation satellite signal receiver 2, the type of navigation satellite signal to be used, and the time zone of the navigation satellite signal reception position. It also includes setting parameters for realizing an algorithm for generating positioning information and time information, which will be described later.

The present invention provides highly accurate time information and highly accurate position with little error from the time of the navigation satellite system when the invisible satellite signal is received as a multipath signal (reflected wave, diffracted wave) without a direct wave. Concers about navigation satellite system receivers that generate information. The operation algorithm will be described below.

First, as a prerequisite, a visible satellite signal (direct wave signal or a multipath signal accompanied by a direct wave) and an invisible satellite signal (direct) in an environment where a structure that blocks the propagation of the navigation satellite signal exists around the navigation satellite antenna 1. Regardless of (multipath signal without waves), it shall be possible to receive signals from four or more navigation satellites. Further, it is unknown whether the received navigation satellite signal is a visible satellite signal or an invisible satellite signal.

Under the above preconditions, the navigation satellite to be used for positioning and time synchronization is selected from the received navigation satellite signals according to the following procedure to improve the positioning and time accuracy. Here, improving the positioning accuracy means reducing the difference between the true value of the coordinates of the receiving position of the navigation satellite signal by the navigation satellite antenna 1 and the coordinates of the positioning result. Improving the time accuracy means reducing the difference from the time generated by the visible satellite signal received in the open sky environment at the receiving position of the navigation satellite signal by the navigation satellite antenna 1. The control unit 4 controls the navigation satellite signal receiving unit 2 and the time information generating unit 3 based on the set values of the parameters set in the setting unit 5 to generate the time information according to the procedure.

The procedure consists of the following procedure (A) initial coordinate value determination procedure and procedure (B) satellite selection / time synchronization procedure. The procedure (A) is a procedure from the start of receiving the navigation satellite signal to the determination of the initial coordinate value, and the procedure (B) is a procedure of selecting the navigation satellite signal and performing positioning and time synchronization. In the processing according to the procedures (A) and (B), since the reception position of the time synchronization device is estimated, it is called "position estimation mode".

Procedure (A)
(A) Of the n navigation satellite signals received after the predetermined reception time set in advance in the setting unit 5 after the time synchronization device is activated, the signal-to-noise ratio (SNR) threshold value set in advance in the setting unit 5. Select navigation satellite signals that exceed. Here, CNR can be used as one of the indicators of SNR. If the number of selected satellites is less than 4, the navigation satellite signal is selected from the satellites having a large CNR in addition to the satellites selected so that the total number of satellites is 4. Here, the reception time is set so that the time synchronization device captures the navigation satellite signal and acquires the orbit information of the satellite, that is, the position information of the navigation satellite from the navigation satellite signal. In the case of GPS, there are two types of satellite orbit data: Almanac data, which is the approximate orbit data of all GPS satellites in operation, and Ephemeris data, which is the precise orbit data of each satellite. Each can be obtained from the navigation message included in the navigation satellite signal, but it takes 12 minutes and 30 seconds to obtain the almanac data. However, the navigation satellite signal with a large CNR is received promptly after activation by an operation called random search, and the orbit data of the satellite can be acquired as ephemeris data from the navigation message of the satellite. Therefore, even if the reception time is set to be shorter than the time required to acquire the almanac data, the operation is not necessarily hindered. In addition to acquiring satellite orbit information from navigation messages, a method of acquiring satellite orbit information from a SUPL (Secure User Plane Location) server via a mobile network using the Assisted GNSS method, or a method of acquiring orbit information published on the Internet. There is also. The following is an example of a site that publishes orbit information of navigation satellites.
URL: http://sys.qzss.go.jp/dod/archives/pnt.html
(B) Positioning is performed using the navigation satellite signal selected in (a) above, and the result is used as the initial coordinate value.

Procedure (B)
(A) Based on the initial coordinate value calculated in the procedure (A), the arrival time at the position of the initial coordinate value is calculated from the position of each of the received n navigation satellites and the time of the navigation satellite signal.
(B) The earliest time T ₀ among the n arrival times calculated in (a) above is determined.
(C) Next, the reference time of T ₀ + dT ₁ is set by the permissible error value dT ₁ set in advance in the setting unit 5.
(D) Of the n arrival times calculated in (a) above, a navigation satellite signal earlier than T ₀ + dT ₁ is extracted.
(E) When the number of navigation satellite signals extracted in (d) above is 4 or more, positioning is performed using the extracted navigation satellite signals and the initial coordinate values in (a) above are updated.
(F) During the coordinate value update period set in advance in the setting unit 5, the above steps (a) to (e) are repeated. That is, recursive processing is performed in which the position information is used as a parameter and the end condition is the processing time.
(G) Positioning and time synchronization are performed using the navigation satellite signal extracted in (f) above, and the obtained time information is used as the time information generated by the received navigation satellite signal.

In the present invention, the following procedures (B') and (B ") may be performed instead of the above procedure (B). The procedures (B') and (B") will be described in detail below.

Procedure (B')
(A) Based on the initial coordinate value calculated in the procedure (A), the arrival time at the position of the initial coordinate value is calculated from the position of each of the received n navigation satellites and the time of the navigation satellite signal.
(B) For each of the nCm combinations of m (however, n> m) of the received n navigation satellites, the average of the arrival times at the positions of the initial coordinate values calculated in (a) above. Calculate the value.
(C) The earliest time T ₀ among the average values of nCm arrival times calculated in (a) above is determined.
(D) Next, the reference time of T ₀ + dT ₂ is set by the permissible error value dT ₂ set in advance in the setting unit 5.
(E) Of the n arrival times calculated in (a) above, a navigation satellite signal earlier than T ₀ + dT ₂ is extracted.
(F) When the number of navigation satellite signals extracted in (e) is 4 or more, positioning is performed using the extracted navigation satellite signal, and the initial coordinate values in (a) above are updated.
(G) During the coordinate value update period set in advance in the setting unit 5, the above (a) to (f) are repeated. That is, recursive processing is performed in which the position information is used as a parameter and the end condition is the processing time.
(H) Positioning and time synchronization are performed using the navigation satellite signal extracted in (g) above, and the obtained time information is used as the time information generated by the received navigation satellite signal.

Procedure (B ")
(A) Based on the initial coordinate value calculated in the procedure (A), the arrival time at the position of the initial coordinate value is calculated from the position of each of the received n navigation satellites and the time of the navigation satellite signal.
(B) For each of the nCm combinations of m (however, n> m) of the received n navigation satellites, the average of the arrival times at the positions of the initial coordinate values calculated in (a) above. Calculate the value.
(C) The earliest time T ₀ among the average values of nCm arrival times calculated in (a) above is determined.
(D) Next, the reference time of T ₀ + dT ₃ is set by the permissible error value dT ₃ set in advance in the setting unit 5.
(E) Of the average value of the arrival times of nCm combinations calculated in (a) above, the navigation satellite signal included in the combination earlier than T ₀ + dT ₃ is extracted.
(F) Positioning is performed using the navigation satellite signal extracted in (e) above, and the initial coordinate values in (a) above are updated.
(G) During the coordinate value update period set in advance in the setting unit 5, the above (a) to (f) are repeated. That is, recursive processing is performed in which the position information is used as a parameter and the end condition is the processing time.
(H) Positioning and time synchronization are performed using the navigation satellite signal extracted in (g) above, and the obtained time information is used as the time information generated by the received navigation satellite signal.

The above margin of error value dT (dT ₁ in procedure (B), dT _{2 in} procedure (B'), dT _{3 in} procedure (B ")) is a parameter set by the setting unit 5. It should be noted that 0 may be set as the permissible error value dT. The method for determining the permissible error value dT will be described later.

The reason why the time synchronization accuracy is improved in each case of the number of visible satellite signals received in each procedure will be described below.

A satellite related to a navigation satellite signal whose reception intensity or CNR threshold value exceeds a predetermined threshold value is likely to be a visible satellite. If the CNR is received above 40 dB-Hz, the navigation satellite signal is likely to be a visible satellite signal. Therefore, in the procedure (A), it is preferable to use a value of 40 dB-Hz as the CNR threshold value. If the number of satellites exceeding the CNR threshold is less than 4, the navigation satellite signals are selected in descending order of CNR, and the number is set to 4. The navigation satellite signals selected in the procedure (A) in this way are expected to contain a large amount of visible satellite signals, and as a result, all the navigation satellites received by the error of the initial coordinate values calculated in the procedure (A). It is expected to be small compared to the error of the coordinate values calculated using the signal.

Next, in the procedure (B), a navigation satellite signal having an earlier arrival time is selected with respect to the initial coordinate value calculated in the procedure (A). The navigation satellite signal selected in this way is likely to be a visible satellite or an invisible satellite with a small propagation delay. When the number of selected navigation satellite signals is four or more, it is expected that the error of the initial coordinate value will be reduced because the positioning calculation is performed and the initial coordinate value calculated in the procedure (A) is updated. By repeating (a) to (e) during the coordinate value update period preset in step (B), the error of the initial coordinate value is gradually reduced, and the navigation satellite signal selected based on this is a visible satellite. Alternatively, it is expected that the accuracy of an invisible satellite with a small propagation delay will be improved.

In step (B), the earliest time T ₀ out of n arrival times is determined based on the initial coordinate values calculated in step (A), whereas in step (B') and step (B "), the procedure Based on the initial coordinate values calculated in (A), the time T ₀ is calculated from the earliest time among the average values of the nCm arrival times. In the procedure (B), an unexpected measurement error may occur at T ₀ . However, in the procedure (B') and the procedure (B "), T ₀ is calculated based on the arrival times of a plurality of navigation satellite signals, so that the influence of measurement fluctuations and the like can be eliminated.

Next, the method for determining the tolerance value dT will be described in detail.

The optimum value of the set value of the permissible error value dT differs depending on the reception state of the navigation satellite signal. In an open skies reception environment, many visible satellite signals are received, but in that case, receiving as many navigation satellite signals as possible evenly distributed in the sky reduces the DOP value and improves accuracy. It is valid. For that purpose, it is necessary to set a relatively large value as the value of the margin of error value dT and select as many visible satellite signals as possible. Since the arrival time of the visible satellite signal has a small delay from the reference time T ₀ , it is considered possible to select all the visible satellite signals by setting the permissible error value dT to about 20 ns. On the other hand, if the tolerance value dT is 0 or 20 ns or less, it may not be possible to select all visible satellite signals.

On the other hand, in a multipath reception environment where the number of visible satellite signals is 4 or less, it is expected to select a navigation satellite signal that achieves the highest accuracy, including the visible satellite signal when the margin of error value dT is 0. However, as the value of the margin of error value dT increases, there is a concern that the positioning / time synchronization accuracy may deteriorate as a result of the selection of many invisible satellite signals. That is, it is desirable that the value of the margin of error value dT is small.

FIG. 2 is a schematic diagram showing the relationship between the set value of the tolerance value dT and the time synchronization accuracy. In the open sky reception environment, the larger the setting value of the tolerance value dT, the smaller the time error that is the deviation from the true value of the time. In the multipath reception environment, the larger the setting value of the tolerance value dT, the smaller the time error. Indicates that the number will increase. In FIG. 2, the case where the number of visible satellites is 8 or more is defined as the “open sky reception environment”, and the case where the number of visible satellites is 4 or less is defined as the “multipath reception environment”.

The evaluation result when the permissible error value dT is fixed by using the time synchronization apparatus which concerns on the said Embodiment is shown. FIG. 3 shows the configuration of the experimental system used to measure the time error caused by the set value of the tolerance value dT in the open sky environment. GPS receiver # 1 that generates a reference signal (1PPS signal and 10MHz clock signal) as a reference signal does not perform satellite selection. On the other hand, the GPS receiver # 2 uses the procedure (B') according to the above embodiment, sets m to 4, and then selects a satellite by setting the tolerance value dT (dT ₂ ). The evaluation index is the measured time error value.

FIG. 4 shows the measurement result of the time error when the navigation satellite signal is selected with the tolerance value dT set to 0 ns, 10 ns, and 20 ns in the open sky environment. Further, FIG. 5 shows the software for observing the status of the navigation satellite signal received and used (selected) at the epoch (time) when the margin of error value dT is set to 0 ns and 10 ns in the open sky environment. It is a partial screen copy. The hatches attached to the circles indicating the navigation satellites in FIG. 5 indicate that the navigation satellite signals from the navigation satellites are received but not used (selected).

As shown in FIG. 4, when the value of the permissible error value dT was set to 0 ns, the time error increased by about 30 ns as compared with the case where the value of the permissible error value dT was set to 10 ns and 20 ns. Further, as shown in FIG. 5, when the value of the permissible error value dT is set to 0 ns, four satellites are used, whereas when the value of the permissible error value dT is set to 10 ns, the satellites are used. The same satellite was used as if no selection was made. That is, it was confirmed that in the open sky reception environment, when the dT value was set to 10 ns, as a result of selecting more visible satellite signals, the DOP value decreased and the time synchronization accuracy was improved.

FIG. 6 shows the results of measuring time errors using the measurement system of FIG. 16 in the multipath reception environment shown in FIGS. 14 and 15. Using procedure (B'), m was set to 4. When the allowable error value dT (dT ₂ ) is set to 20 ns, the maximum time error reaches about 60 ns, whereas when the allowable error value dT is set to 0 ns and 5 ns, the time is reached. It was confirmed that the maximum value of the error was reduced to about 20 ns.

7 and 8 are screen copies of software for observing the reception state of navigation satellite signals, FIG. 7 shows the satellite selection algorithm of the present invention as a comparison target, and FIG. 8 uses the satellite selection algorithm of the present invention. An example of the reception status and the usage (selection) status of the GPS satellite signal is shown.

As shown in FIG. 7, when satellite selection is not performed, many invisible satellite signals are estimated in addition to the GPS satellite signals estimated to be the visible satellite signals of Nos. 01, 11, 17, 19, and 23. GPS satellite signal is selected. On the other hand, as shown in FIG. 8, when the satellite is selected with the margin of error value dT set to 5 ns, the GPS satellite signal estimated to be a visible satellite signal is selected. As a result of effectively eliminating the invisible satellite signal by the satellite selection algorithm of the present invention in this way, it is considered that the time synchronization accuracy is improved.

As shown in the above results, the margin of error value dT is preferably determined according to the reception environment of the navigation satellite signal. Specifically, it is preferable that the tolerance value dT is increased as the reception environment is closer to the open sky environment, and the tolerance value dT is decreased as the reception environment is closer to the multipath environment. In other words, it is preferable that the larger the number of visible satellites, the larger the permissible error value dT, and the smaller the number of visible satellites, the smaller the permissible error value dT.

As for the actual reception environment of satellite signals, various reception environments are assumed, from a so-called open sky state in which no structure exists around the navigation satellite antenna to a reception environment in which the visible satellite signal is zero. As a method of optimizing the set value of the error tolerance dT according to the reception environment, it is considered that the method of referring to the reception state (CNR) of the navigation satellite signal received in the procedure (A) is effective. That is, based on the CNR, when there are many navigation satellite signals with a large CNR, it is estimated that the reception environment is closer to open skies, in other words, it is estimated that the number of visible satellites is large, and the error tolerance dT is a large value. Set to. On the contrary, when these navigation satellite signals are small, it is estimated that the reception environment is closer to the multipath environment, in other words, the number of visible satellites is estimated to be small, and the error tolerance dT is set to 0 or a small value. Set.

Specifically, it is conceivable to determine the value of the error tolerance dT based on the number of navigation satellite signals exceeding the CNR threshold set in the procedure (A). Since it is highly probable that a satellite related to a navigation satellite signal whose CNR threshold value exceeds a predetermined threshold value is a visible satellite, it is estimated that the number of navigation satellite signals is the number of visible satellites.

A specific example in which the CNR threshold value is set in advance and the value of the error tolerance dT is set based on the number of navigation satellite signals exceeding the CNR threshold value will be described with reference to FIGS. 9, 10 and 11.

9 and 10 are screen copies of software for observing the reception state of GPS satellite signals with respect to the reception environment. FIG. 9 shows the observation in the open sky reception environment, and FIG. 10 shows the observation in the multipath reception environment. An example of the reception status of GPS satellite signals is shown. In FIGS. 9 and 10, when the CNR threshold was set to 40 dB-Hz, the number of GPS satellite signals exceeding the CNR threshold was 11 in FIG. 9 and 4 in FIG.

An example of setting the tolerance value dT based on the CNR of the received navigation satellite signal will be described with reference to FIG. In a specific example of the present embodiment, the function is set so that the permissible error value dT increases as the number of navigation satellite signals exceeding the CNR threshold increases. FIG. 11 is a diagram showing a function for obtaining the tolerance value dT set for the number of navigation satellite signals exceeding the CNR threshold value. In the example of FIG. 11, when the number of navigation satellite signals exceeding the CNR threshold is 4 or less, the margin of error value dT is set to linearly increase from 0 ns to 5 ns, and the number of navigation satellite signals exceeding the CNR threshold is 4 to 10. In the section up to, the margin of error value dT is set to linearly increase from 5 ns to 20 ns, and when the number of navigation satellite signals exceeding the CNR threshold is 10 or more, the margin of error value dT is set to 20 ns. The setting examples shown in FIGS. 9 to 11 are not limited to this, and the CNR threshold value, the allowable error value dT value based on the CNR of the received navigation satellite signal, and the CNR threshold value in the function of FIG. 11 can be set. For the constants (4 and 10) for the number of signals exceeding the CNR threshold and the function for obtaining the permissible error value dT to be set for the number of navigation satellite signals exceeding the CNR threshold, use an appropriate value or an appropriate function formula based on experiments or the like. It can be set in advance. The index used to estimate the reception environment, that is, the index used to estimate the number of visible satellites, includes the CNR, which is one of the SNR indexes, and the reception status of navigation satellite signals such as the SNR itself and the reception strength. Other indicators can be used to represent.

The roles of each functional unit in carrying out the above procedure are as follows.

Based on the instruction from the control unit 4, the navigation satellite signal receiving unit 2 performs positioning and time synchronization using the designated navigation satellite signal among the received navigation satellite signals, and the time information and the navigation satellite obtained as a result. The signal information is output to the time information generation unit 3 and the control unit 4. The time information generation unit 3 generates and outputs time information based on the time information output from the navigation satellite signal reception unit 2, the navigation satellite signal information, and the parameter values input from the control unit 4. The control unit 4 creates a table of combinations of navigation satellite signals based on the information of the received navigation satellite signal output from the navigation satellite signal reception unit 2 and the setting information of the parameters input to the setting unit 5, and navigates. Instruct the satellite signal receiving unit 2 to perform positioning and time synchronization. Furthermore, the time information obtained from the navigation satellite signal receiver 2 is compared and the navigation satellites are extracted for each combination of navigation satellite signals, and finally the navigation satellite is designated for the navigation satellite signal receiver 2 and the time information is given. Instruct positioning and time synchronization for obtaining time information to be output to the generation unit 3. In this extraction process, the permissible error value dT calculated by the reception strength or CNR of the navigation satellite signal received by the navigation satellite signal reception unit 2 and the setting information such as the threshold value input to the setting unit 5 is used. Further, the control unit 4 outputs the parameter setting information input to the setting unit 5 to the navigation satellite signal receiving unit 2 and the time information generating unit 3.

As is clear from comparing the experimental results of FIG. 6 with that of FIG. 17, in the present invention, the navigation satellite signal suitable for use in time synchronization does not depend on the reception characteristics of the navigation satellite antenna and the performance of the navigation satellite signal receiver. By selecting, the effect of effectively eliminating the influence of the multipath signal of the invisible satellite signal and improving the time synchronization accuracy can be expected.

Further, as shown by the experimental results of FIGS. 4 and 6, high time synchronization accuracy can be realized by appropriately setting the parameter values according to the reception environment.

In the present invention, since the navigation satellite signal to be used for time synchronization is selected in the navigation satellite signal receiver, it is not necessary to implement circularly polarized wave isolation or vertical isolation in the navigation satellite antenna. It is possible to reduce the cost.

As described above, according to the present invention, it does not depend on the reception environment of the navigation satellite signal, that is, even if the reception environment is not good, that is, the required number of visible satellite signals cannot be temporarily captured, or the open sky. It is possible to generate highly accurate time information synchronized with the navigation satellite signal even in a good reception environment.

In addition, the average value of the arrival times of nCm combinations is calculated in the above procedures (B') and (B "), but the positioning / time using the combination of navigation satellite signals that is a subset of the conventional received navigation satellite signals. Because the amount of calculation is much smaller than the method of performing synchronous calculation in advance and selecting navigation satellite signals by statistical processing, due to the limitation of signal processing resources in the navigation satellite system receiver, satellite selection It is unlikely that there will be a problem that the calculation of is not possible, or that the calculation time is required and satellite selection cannot be performed in a timely manner.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited thereto. For example, the time synchronization device according to the above embodiment has a form in which a position estimation mode that does not require position information of the receiving position is implemented, but the position estimation mode is first activated, and then the position is fixed based on the derived position. It may be an operation to shift to the mode. As an example of the opportunity to shift to the fixed position mode, the difference between the position calculated last time and the position calculated this time is compared with a predetermined threshold value, and the state of the time-dependent fluctuation of the derived position, in other words, the convergence of the derived position. An algorithm that determines the transition based on the situation can be considered.

Further, in the above embodiment, all of the received n navigation satellite signals are processed targets (step (a), procedure (B') and step (B ") of the above procedure (B)). A) (Refer to (b)), in order to reduce the calculation process, the present invention may be applied after selecting a predetermined number of navigation satellite signals by masking processing such as an elevation angle mask or a CNR mask.

Further, in the above embodiment, the processing time is based on whether or not the processing time is equal to or less than a predetermined threshold value as the end condition in the recursive processing of the above procedures (B), (B') and (B "), but other It may be an end condition. For example, any one of a condition comparing the number of recurrences and a predetermined threshold value, a condition comparing the difference between the previously calculated position and the position calculated this time and the predetermined threshold value, or , These may be any combination of conditions comparing the processing time with a predetermined threshold value.

Further, in the above embodiment, the position of the navigation satellite antenna is fixed, but the present invention can be applied even in the form of moving the navigation satellite antenna. In this case, the update frequency of the output in the position estimation mode is improved as necessary.

Further, in the above-described embodiment, one navigation satellite system is used, but the present invention can also be applied to a so-called multi-GNSS usage mode in which a plurality of navigation satellite systems are used in combination. In this case, the number of visible satellite signals is increased, so that the accuracy is expected to be improved. As the combination target, not only the Global Navigation Satellite System (GNSS) but also the Regional Navigation Satellite System (RNSS) system can be used. Global navigation satellite systems include GPS, GLONASS, Galileo, and Beido, and regional navigation satellite systems include QZSS. When combining a plurality of navigation satellite systems, the time offset between the navigation satellite systems may be reflected, and the permissible error value dT may be set to a different value for each navigation satellite system.

Further, in the above embodiment, the time synchronization device has been described as an example of the navigation satellite system receiving device, but the present invention can be applied to the positioning device to improve the positioning accuracy. That is, the navigation satellite signal selection algorithm used for generating the time information in the above-mentioned time synchronization device can be applied to the generation of the received position information. In this case, the reception position information obtained as a result of the positioning in step (g) of the above-mentioned procedure (B) or step (c) of steps (B') and (B ") may be output. That is, this positioning device. In the configuration of the above-mentioned synchronization device, includes the navigation satellite antenna 1, the navigation satellite signal receiving unit 2, the control unit 4, and the setting unit 5, and the above-mentioned procedure (step (g) of the above-mentioned procedure (B)). Alternatively, the reception position information obtained by positioning with the navigation satellite signal receiving unit 2 in step (c) of steps (B') and (B ") may be output. The navigation satellite signal receiving unit 2 outputs the information. In order to output the reception position information in a predetermined format and timing, a reception position information output unit may be further provided.

FIG. 12 shows the results of measuring the positioning accuracy in the multipath reception environment shown in FIGS. 14 and 15 using the positioning device according to the above embodiment. Using procedure (B'), m was set to 4. It was confirmed that when the value of the permissible error value dT (dT ₂ ) was set to 5 ns, the positioning accuracy was significantly improved as compared with the case where satellite selection was not performed.

1 ... Navigation satellite antenna 2 ... Navigation satellite signal reception unit 3 ... Time information generation unit 4 ... Control unit 5 ... Setting unit

Claims (6)

In a navigation satellite system receiver that performs at least one of positioning processing or time synchronization processing with the navigation satellite based on navigation satellite signals received from a plurality of navigation satellites.
A navigation satellite signal receiver that calculates the reception position and reception time based on navigation satellite signals received from four or more navigation satellites at the same time.
The initial value of the reception position and the orbital position of each navigation satellite are calculated based on each navigation satellite signal from four or more navigation satellites that can be received simultaneously, and the calculated reception position and orbital position and the time included in each navigation satellite signal are included. The arrival time of each navigation satellite signal is calculated based on the information, the navigation satellite signal is extracted based on the calculated arrival time, the reception position is calculated based on the extracted navigation satellite signal, and the arrival time is used using the calculated reception position. Control to recursively perform the calculation process of the navigation satellite signal, the extraction process of the navigation satellite signal, and the calculation process of the reception position, and perform the positioning process or the time synchronization process based on the extracted navigation satellite signal at the end of the recurrence. A navigation satellite system receiver characterized by having a unit. The navigation satellite system receiving device according to claim 1, wherein the processing time of the recursive processing is included as a parameter of the end condition of the recursive processing. The navigation satellite system receiving device according to claim 1 or 2, wherein the control unit extracts a navigation satellite signal whose arrival time is earlier than the time obtained by adding a tolerance value to the earliest arrival time. The navigation satellite system receiving device according to claim 3, wherein the tolerance value is determined based on a reception state of a navigation satellite signal. In a navigation satellite signal processing method in a navigation satellite system receiver that performs at least one of positioning processing or time synchronization processing with the navigation satellite based on navigation satellite signals received from a plurality of navigation satellites.
The navigation satellite system receiver includes a navigation satellite signal receiver that calculates the reception position and reception time based on navigation satellite signals received from four or more navigation satellites at the same time, and a control unit that controls the navigation satellite signal receiver. Prepare,
In the navigation satellite signal processing method, the control unit
Steps to calculate the initial value of the reception position and the orbital position of each navigation satellite based on each navigation satellite signal from four or more navigation satellites that can be received simultaneously, and
A step of calculating the arrival time of each navigation satellite signal based on the calculated reception position and orbit position and the time information included in each navigation satellite signal, and
Steps to extract navigation satellite signals based on the calculated arrival time,
Steps to calculate the reception position based on the extracted navigation satellite signal,
A step of recursively performing the arrival time calculation step, the navigation satellite signal extraction step, and the reception position calculation step using the calculated reception position, and
A navigation satellite signal processing method in a navigation satellite system receiver, characterized in that it includes a step of controlling positioning processing or time synchronization processing based on the navigation satellite signal extracted at the end of recurrence. A navigation satellite signal processing program comprising a computer functioning as each part of the navigation satellite system receiving device according to any one of claims 1 to 4.