JP5650436B2 - Satellite positioning receiver - Google Patents

Description

  The present invention relates to a satellite positioning receiver (hereinafter referred to as an SPS receiver) used in a satellite positioning system (hereinafter abbreviated as SPS), and particularly used for positioning calculation in an SPS receiver. The present invention relates to a pseudo-range generation processing method.

  Positioning devices using SPS such as GPS (Global Positioning System) are employed in many devices such as car navigation systems and mobile phones and used for self-position calculation (see, for example, Patent Document 1). In mobile phones, etc., it is necessary to perform self-location calculations immediately in response to requests from users, so assist information is provided to mobile phones via mobile phone base stations to significantly reduce positioning calculation time. A process called GPS (Assisted GPS) is performed.

  However, when there is no means for transmitting such assist information to the positioning terminal, it usually takes about 30 seconds to several minutes to start the positioning calculation, and efforts to shorten this time to the theoretical limit are made on the receiver. It is done by manufacturers.

  There are two main factors that increase the time required to start positioning (Time To First Fix, hereinafter abbreviated as TTFF. The time it takes to get the first position coordinates after turning on the receiver). Positioning signal acquisition processing takes time, and the other is that it takes time to acquire satellite orbit parameters. With regard to the former, it is possible to reduce the time required for signal acquisition by installing a large number of correlators, and some commercially available products can acquire the signals of most visible satellites in a few seconds. The latter is the time required to acquire the satellite orbital parameter called Ephemeris obtained by decoding the navigation message after the positioning signal is acquired, which currently takes about 18 to 30 seconds after the signal acquisition. Yes. Although the time taken to acquire this ephemeris cannot be shortened by the usual method, in recent years, the technology for estimating future orbital parameters from old ephemeris data has advanced, and ephemeris broadcast from satellite (hereinafter referred to as “broadcast ephemeris”). It is possible to predict up to about a week ahead without much difference from the accuracy of "referred to"), so that it is possible to significantly reduce TTFF. This predicted ephemeris is called Extended Ephemeris.

  Since infrastructure development is progressing and an environment where it is easy to acquire information from wireless networks other than mobile phones is being prepared, even if it is not possible to acquire all of the time, position, and ephemeris information in advance, as with assist type GPS, Only the ephemeris can be acquired in advance.

  As described above, since the time required for signal acquisition and the time required for ephemeris acquisition, which have been the main causes of increasing TTFF in the past, are shortened or become zero, reduction of the time required for other processing is the next important issue. It is becoming.

Special table 2007-504731 gazette

European GNSS (Galileo) Open Service Signal In Space Interface Control Document, Issue 1

  As mentioned above, infrastructure development has progressed, and the time required for signal acquisition and the time required for ephemeris acquisition, which were the main causes of TTFF lengthening in the past, have been shortened or become zero, reducing the time required for other processing. Shortening is becoming the next important issue.

  The present invention has been made to solve such a problem, and a satellite positioning receiver for shortening the TTFF by shortening the time until pseudo-range generation is started in receiving a positioning signal. The purpose is to obtain (a receiver for SPS).

The present invention provides a reception antenna for SPS that receives RF signals from a plurality of satellites, and a front-end process that performs amplification processing, filtering processing, and A / D conversion processing on the received RF signals. End means, baseband processing means for obtaining a signal propagation time by performing signal acquisition and tracking processing on the digital signal obtained by the front end processing, and pseudorange calculation and positioning based on the signal propagation time. Navigation calculation means for performing calculation, and the baseband processing means uses Tiered Code of GALILEO, and the code length of the Tired Code is 2.5 times the difference between the shortest arrival time and the longest arrival time of the RF signal. greater, among the plurality of satellites, the reference satellite that was obtained originally SPS system time signal from the navigation data has been transmitted most is the SP Signal propagation time is calculated using system time, and for other satellites, the code phase difference between the satellite and the reference satellite is obtained, and the signal propagation time is calculated from the code phase difference. It is a positioning receiver (receiver for SPS).

The present invention provides a reception antenna for SPS that receives RF signals from a plurality of satellites, and a front-end process that performs amplification processing, filtering processing, and A / D conversion processing on the received RF signals. End means, baseband processing means for obtaining a signal propagation time by performing signal acquisition and tracking processing on the digital signal obtained by the front end processing, and pseudorange calculation and positioning based on the signal propagation time. Navigation calculation means for performing calculation, and the baseband processing means uses Tiered Code of GALILEO, and the code length of the Tired Code is 2.5 times the difference between the shortest arrival time and the longest arrival time of the RF signal. greater, among the plurality of satellites, the reference satellite that was obtained originally SPS system time signal from the navigation data has been transmitted most is the SP Signal propagation time is calculated using system time, and for other satellites, the code phase difference between the satellite and the reference satellite is obtained, and the signal propagation time is calculated from the code phase difference. Since it is a positioning receiver (receiver for SPS), in receiving a positioning signal, the time until pseudo-range generation is started is shortened, and the effect of further shortening TTFF is obtained.

It is the block diagram which showed the basic composition of the receiver for SPS which concerns on this invention. It is a block diagram which showed the fundamental structure of the receiver for SPS which concerns on this invention of the form which obtains ephemeris from an external network. It is the block diagram which showed the basic composition of the receiver for SPS which concerns on this invention of the form which obtains an ephemeris from an extended ephemeris calculation part. It is the block diagram which showed the structure of the baseband process part provided in the receiver for SPS shown in FIGS. It is the flowchart which showed the operation | movement of the satellite signal tracking channel by the conventional method in the baseband process part provided in the receiver for SPS shown in FIGS. It is the flowchart which showed the operation | movement of the satellite signal tracking channel until the pseudo-range generation start in this invention in the baseband process part provided in the receiver for SPS shown in FIGS. It is explanatory drawing which showed an example of the relationship between a code phase and signal propagation time. It is explanatory drawing which showed another example of the relationship between a code phase and signal propagation time.

  FIG. 1 is a configuration diagram showing a basic configuration of an SPS receiver according to the present invention. The basic configuration of the SPS receiver according to the present invention is as shown in FIG. 1 and is not particularly different from a general SPS receiver. First, front end processing is performed in the RF front end unit 2 on the RF signal received from the satellite by the SPS receiving antenna 1. This front-end processing includes amplification processing, filter processing, down-conversion processing (some methods do not down-convert), A / D (Analog to Digital) conversion processing, etc., but it is not always necessary to include all of them. It can be changed as appropriate. After the front end processing by the RF front end unit 2 is completed, the baseband processing unit 3 performs signal acquisition and tracking processing, and navigation data including ephemeris data and signal propagation time are obtained. Based on the result, the navigation calculation unit 4 generates raw observation data such as a pseudorange, Doppler, and carrier phase, and performs a positioning calculation process to calculate a self-position and a velocity.

  However, the effectiveness of the present invention can be realized especially by the user of the receiver for SPS when the ephemeris can be acquired in advance from the communication network or when the extended ephemeris can be used. The embodiments are configured as shown in FIGS. 2 and 3, respectively.

  FIG. 2 shows a configuration in the case where the navigation calculation unit 4 acquires a broadcast ephemeris or an extended ephemeris from the external communication network via the communication device 5 immediately before or at the start of positioning. Other configurations are the same as those in FIG.

  In FIG. 3, an extended ephemeris calculation unit 6 is provided that predicts ephemeris data at the current time based on ephemeris data included in the navigation data obtained by the baseband processing unit 3 during past reception processing. The navigation calculation unit 4 uses the extended ephemeris predicted by the extended ephemeris calculation unit 6. Other configurations are the same as those in FIG.

  1 to 3, the baseband processing unit 3 incorporates a plurality of signal reception channels 31 corresponding to the maximum number of satellites desired to be received, as shown in FIG. 4. . In order to calculate the signal propagation time between the SPS satellite and the SPS receiver by each signal reception channel 31, not only the code phase calculation but also the bit synchronization to the navigation message and the acquisition of the time corresponding to the bit are necessary. It becomes. FIG. 5 is a flowchart showing the operation of the satellite signal tracking channel according to the conventional method in the baseband processing unit 3.

  The method of FIG. 5 will be briefly described. When the digital sampling data from the RF front end unit 2 shown in FIG. 1 to FIG. 3 is input to the baseband processing unit 3, first, in step S1, the baseband processing unit 3 Acquisition processing is performed to identify which satellite signal is being received. Next, in step S2, the baseband processing unit 3 determines whether or not the signal acquisition processing of the digital sampling data is completed. If the acquisition processing is not completed, the baseband processing unit 3 continues the processing of step S1. When the capturing process is completed, the process proceeds to step S3. In step S <b> 3, the baseband processing unit 3 performs pull-in processing so that the frequency of the captured signal and the frequency of the locally generated signal used for the signal tracking processing are substantially matched. After the pull-in process is completed, in step S4, the baseband processing unit 3 performs a tracking process. In the tracking process, first, a bit synchronization process is performed in step S11 so that the bit position of the navigation data included in the received wave is recognized so that the bit of the received data can be extracted. After performing the bit synchronization processing, in each signal reception channel 31, the navigation message included in the signal is decoded and the navigation data is output in step S12. Next, in step S13, the SPS system time corresponding to the signal is acquired from the navigation data obtained in step S12. In step S14, the code phase is calculated. Next, in step S15, the signal propagation time of the received wave is calculated and output using the time acquired in step S13, the code phase calculated in step S14, and the receiver time set appropriately in the SPS receiver. .

  At this time, the code phase in step S14 can be obtained immediately after the pull-in process in step S3. However, the time in step S13 can be obtained in the case of, for example, a GALILEO E1 or E5-B navigation message (I / NAV). Because of its specifications, it takes about 22 seconds at the maximum. Acquisition of the time in step S13 is a process that must be performed individually for each signal reception channel 31, and this time acquisition is performed when performing a general positioning calculation process performed using observation values of four or more satellites. Time is a problem.

  Therefore, in the following first to third embodiments of the present invention, generation of a pseudo distance for shortening the time required for time acquisition when performing general positioning calculation processing using observation values of four or more satellites A processing method and an SPS receiver using the processing method will be described.

  When performing code positioning by pseudorange using SPS, if a code with a long code length such as Tiered Code of GALILEO is used, each signal receiving channel 31 of the positioning signal independently acquires the time corresponding to the received signal. Without it, the relative signal propagation time difference can be calculated. In the following first to third embodiments, by calculating the relative signal propagation time difference, the time to start positioning is shortened as much as possible, and positioning calculation can be started in a shorter time (TTFF Can be shortened).

  In order to generate the pseudo distance in the signal reception channel 31 of the positioning signal of each satellite, it is necessary to acquire the transmission time of the signal received in each signal reception channel 31. “Acquisition of transmission time” means that it is necessary to decode the navigation message in each signal reception channel 31 to extract time data. In the case of GALILEO's E1 public service, the time required to acquire time data is longer than that of the GPS L1 public service (C / A code), so the time required to start the positioning calculation can also be relatively long. There is sex.

  However, in the case of GALILEO, there are signal components using Tiered Code on which Secondary Code is superimposed including E1, and the code length is 100 [msec] at the maximum. Normally, the arrival time difference of positioning signals is within 30 [msec]. Therefore, if the code phase obtained using Tiered Code is correctly interpreted, the signal propagation time difference of each satellite, that is, the pseudorange difference can be calculated. This means that if the “acquisition of transmission time” is performed for only one satellite, the pseudoranges of all the satellites can be calculated.

  As described above, in the present invention, the Tiered Code that is not originally used for calculating the pseudorange difference is used to shorten the time until the pseudorange calculation is started and the time required until the positioning is started.

Embodiment 1 FIG.
FIG. 6 shows an operation flow in the baseband processing unit 3 according to the first embodiment of the present invention. In the process of FIG. 6, the processes from step S1 to S14 are basically the same as those in FIG. The difference between FIG. 6 and FIG. 5 is that in FIG. 6, the signal propagation time calculation of step S20 is performed instead of the signal propagation time calculation of step S15 of FIG. In step S15 in FIG. 5, the signal propagation time is calculated using the time acquired in its own signal reception channel 31, but in step S20 in FIG. 6, the signal of the reference satellite is not used. The code phase and signal propagation time of the reference satellite are acquired from the reception channel 31, and the signal propagation time of digital sampling data from other satellites is calculated. Here, a reference satellite is a satellite that can acquire a positioning signal and obtain the first transmission time from a navigation message among a plurality of satellites to be received. And

  In FIG. 6, it is assumed that the code period of a code used for signal acquisition and tracking is sufficiently long (described later), and this corresponds to a code called GALILEO Tiered Code. In the first embodiment of the present invention, it is assumed that a Tiered Code of 100 [msec] is used. In FIG. 6, as described above, as shown in FIG. 5, the signal propagation time is not calculated using the time acquired by its own signal reception channel 31, and in step S <b> 20 of FIG. There is a feature that the code phase of the reference satellite and the signal propagation time are obtained from the reception channel 31 and the signal propagation time of the received signal is calculated. However, also in the present embodiment, for the reference satellite only, the pseudo distance is generated by acquiring the time from the navigation message by the conventional method shown in FIG. 5, and for the other satellites, FIG. The signal propagation time is calculated from the code phase difference between the satellite and the reference satellite by the method shown in FIG.

  In the conventional method of FIG. 5, in each signal reception channel 31, the time corresponding to the signal is acquired from the navigation message included in the signal (step S13), the code phase is calculated (step S14), and the code Using the phase and the receiver time set in the receiver, the signal propagation time is calculated based on the time acquired in step S13 (step S15). Here, the receiver time is a time set appropriately based on the time acquired by the signal reception channel 31 of the reference satellite, etc., and is not necessarily accurate, and an error of about 10 [msec] is allowable. Is done. Usually, since the range of values that the signal propagation time can take is determined according to the altitude to be used, the signal propagation time is appropriately set so as not to deviate from the range.

  On the other hand, in the method of FIG. 6, in each signal reception channel 31, navigation data such as the time corresponding to the signal is acquired from the navigation message included in the signal, but the time is the signal propagation time as in the method of FIG. It is not necessary for the calculation (step S20). Instead, the code phase and signal propagation time of the reference satellite are acquired, and the signal propagation time of the received signal from other satellites other than the reference satellite is calculated using these and the code phase calculated in step S14 ( Step S20). Thereby, since the signal propagation time calculation can be started without waiting for the completion of the time acquisition process (step S13) in FIG. 6, the time until the calculation of the signal propagation time (corresponding to the pseudo distance if the speed of light is applied) is started. There is an effect that can be shortened.

Now, the code phase of a certain signal receiving channel 31 is φ _c [chip], the code phase of the reference satellite is φ _{c, r} [chip], the code length of the code used for tracking is L _c [chip], and the code period Is T _c [s], and the signal propagation time of the reference satellite is Δt _r [s], the signal propagation time Δt _k [s] of the satellite k is expressed as follows.

However, in the first embodiment, the code period T _c is 0.1 [s], and the time conversion value of the code phase φ _c [chip] is a value from 0 to 0.1 [s]. N is an integer of 0 or ± 1, and is determined as follows.

First, as in the example of FIG. 7, when the time converted values of the code phases A, B, C, D, and E are all within a width of 40 [msec], the signal propagation time increases as the code phase increases. In the above formula (1), N = 0. On the other hand, as shown in the example of FIG. 8, the code phase is divided into a small code phase and a large code phase with L _c / 2 as the boundary, and the total of both code phase distribution sections is within 40 [msec]. In this case, since the signal propagation times of D and E are shorter than the signal propagation times of A, B and C, it is necessary to determine N according to the positional relationship of the code phase with the reference satellite. For example, when the reference satellite is any one of A, B, and C, N = 0 in calculation of Δt _A , Δt _B , and Δt _C other than the reference satellite, but Δt _D and Δt _E are calculated. Then, N = −1. When the reference satellite is either D or E, N = 0 in the calculation of Δt _D and Δt _E other than the reference satellite, but in the calculation of Δt _A , Δt _B and Δt _C , N = + 1. Even if the number of observation satellites is different from the example of FIG. 8, N may be determined by the same logic. In cases other than the above (FIG. 7, FIG. 8), the observation value is rejected because the observation value includes an abnormal value.

  In order to determine N according to the conditions and determine the signal propagation time using the above equation (1), the code length must be long to some extent, and the condition is the shortest arrival time of the positioning signal [ (2 + α) times the difference between s] and the longest arrival time [s] is equal to or shorter than the code length [s]. α is preferably set to a value of about 0.5 in consideration of various errors and calculation certainty. The method of the present invention can be realized, for example, by using a Tiered Code obtained by superimposing a Primary Code and a Secondary Code in signal components called E1-C, E5a-Q, and E5b-Q among the positioning signals of GALILEO. Since the code length is 0.1 [s] (see Non-Patent Document 1), when α = 0.5, the difference between the shortest arrival time and the longest arrival time of the positioning signal is 0.04 [s]. ] What is necessary is as follows. The conditions for the SPS receiver to satisfy this condition are determined from the positional relationship between the earth, the SPS satellite, and the SPS receiver. In the case of GALILEO, the altitude of the SPS receiver should be about 1600 [km] or less. Can be calculated.

  The signal propagation time obtained by the above equation (1) becomes a pseudorange by multiplying by the speed of light c = 2.99792458e + 8 [m / s], and usually autonomous positioning calculation if observation values of 4 satellites or more are obtained. It can be performed.

  It should be noted that once the signal propagation time of each satellite can be calculated according to equation (1), the signal propagation time of each satellite can be calculated without using the observation value of the reference satellite according to the following equation.

In the expression (2), _NT is a code ambiguity in observation using Tiered Code, and is always an integer value, and R _c [s] is a fraction of the distance. If Δt _k is determined in equation (1) based on the observed value at a certain moment, integer value _NT is determined so that the absolute value of R _c is smaller than T _{c according} to equation (2). Once the N _T and R _c, from the following observations can be updated observations using only the code phase phi _c of each satellite.

  If it is possible to shift to observation value generation according to equation (2), observation values can be generated even if the observed satellite changes and the observation of the reference satellite is interrupted, and observation value generation according to equation (2) is performed. As a reference satellite, the observation value of the newly acquired satellite can be generated in a shorter time than the conventional method by the equation (1).

  As described above, according to the first embodiment, the pseudo-range generation is performed by the conventional method for the reference satellite that first obtains the SPS system time from the navigation data among a plurality of satellites. For other satellites, the signal propagation time is calculated from the code phase difference between the satellite and the reference satellite, so that the time required to start the pseudorange generation can be greatly shortened. Moreover, even if the observation of the reference satellite is interrupted, the effect of shortening the time required until the start of pseudo-range generation of the newly started observation continues.

Embodiment 2. FIG.
Although the present embodiment is basically the same as the first embodiment, if the Tiered Code is used at the time of signal acquisition, the code length of the Tiered Code is long, so that it takes time to search for the code phase. Therefore, in the present embodiment, in the case of GALILEO, a method is used in which a primary code is used at the time of signal acquisition, and when signal acquisition is completed, a transition to Tiered Code is performed from that point. For example, when the Primary Code has a length of 4 [msec] and the Secondary Code is 25 bits, the code phase of the Tiered Code can be obtained if 25 types of code timings are inspected after signal acquisition by the Primary Code. The processing after shifting to Tiered Code in signal acquisition is exactly the same as in the first embodiment.

  As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained. Further, in the present embodiment, the signal acquisition is completed by using the primary code at the time of signal acquisition. Then, since the transition to Tiered Code is made from that point, the time required to search for the code phase can be shortened compared to the case where signal acquisition is performed using a Tiered Code having a long code length.

Embodiment 3 FIG.
Although this embodiment is basically the same as the first embodiment, it is not necessary to continue using the Tiered Code after the code phase difference from the reference satellite is found by the Tiered Code. After the code phase difference from the reference satellite is found, the process proceeds to the code tracking process by the primary code. Can have such that, when the signal propagation time Delta] t _k by equation (2) in positioning by Tiered Code is be calculated, since a state of so-called code ambiguity is solved, the code phase by Primary Code It can also determine the code ambiguity respect, because it calculates the signal propagation time Delta] t _k. This is explained using the following equation:

First, at a certain observation timing, the code phase φ _c [chip] based on the Tiered Code and the code phase φ _cp [chip] based on the Primary Code are obtained simultaneously. At this time, since the Delta] t _k is determined by equation (2), the observed values with Primary Code according to equation (3) by determining the integer code ambiguities N _P and constant R _cp of formula (3) Can move to production. Here, the code length of the Primary Code is L _cp [chip], and the code period of the Primary Code is T _cp [s]. Method of determining the code ambiguity _{N P} and constant _{R cp} is the same as the constant R _c of the formula (2) _may be determined integer _{N P} so that the absolute value of _{R cp} is less than _{T cp.}

  As described above, according to the third embodiment, the same effects as those of the first embodiment can be obtained. Further, in the present embodiment, the code phase difference with the reference satellite is obtained by the Tiered Code. After that, since the transition to the Primary Code was made, the time required for the tracking process can be shortened compared to the case where the tracking process is performed using a long code length Tiered Code, and tracking for high maneuvering motion is possible. The processing capability can be increased.

  In the above description, the example in which the third embodiment is applied to the first embodiment has been described. However, the present invention is not limited thereto, and the third embodiment may be applied to the second embodiment.

  GALILEO in Europe is scheduled to be available as a full-spec system with FOC (Full Operational Capability) after 2013, and the method of the present invention will be utilized in GALILEO-compatible receivers. In addition to GALILEO, the present invention can be applied when all code lengths have a length that satisfies a certain condition as described above, such as GALILEO Tiered Code. Therefore, it will be used in various SPS receivers such as GPS positioning devices for mobile terminals, special SPS receivers for high-motion flying vehicles such as rockets and missiles, and SPS receivers for spacecraft. Is possible.

  1 SPS receiving antenna, 2 RF front end unit, 3 baseband processing unit, 4 navigation calculation unit, 5 communication device, 6 extended ephemeris calculation unit, 31 signal reception channel.

Claims (4)

An SPS receiving antenna for receiving RF signals from a plurality of satellites;
Front end means for performing front end processing including amplification processing, filtering processing, and A / D conversion processing on the received RF signal;
Baseband processing means for performing signal acquisition and tracking processing on the digital signal obtained by the front end processing to obtain a signal propagation time;
Navigation calculation means for performing pseudorange calculation and positioning calculation based on the signal propagation time, and
The baseband processing means is
Using GALILEO's Tiered Code, the code length of the Tiered Code is greater than 2.5 times the difference between the shortest arrival time and the longest arrival time of the RF signal,
For the reference satellite that obtained the SPS system time at which the signal was first transmitted from the navigation data among the plurality of satellites, the signal propagation time is calculated using the SPS system time,
For other satellites, a satellite positioning receiver characterized in that a code phase difference between the satellite and the reference satellite is obtained, and a signal propagation time is calculated from the code phase difference. The baseband processing means, using the Primary Code during signal acquisition, after the signal acquisition is completed satellite positioning receiver according to claim 1 which comprises using the Tiered Code. The baseband processing means uses the Tiered Code, obtains the code phase difference between the reference satellite, thereafter, using the Primary Code, according to claim 1, characterized in that the calculation of the signal propagation time Satellite positioning receiver described in 1. The baseband processing means, using the Primary Code during signal acquisition, after the signal acquisition is completed using the above Tiered Code, obtains the code phase difference between the reference satellite, thereafter, again, using the Primary Code, 3. The satellite positioning receiver according to claim 2, wherein a signal propagation time is calculated.

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