Satellite positioning receiver

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 is particularly used for positioning calculation in a SPS receiver. The present invention relates to a pseudo-distance generation processing method.

Positioning devices that use SPS, such as GPS (Global Positioning System), are used in many devices such as car navigation systems and mobile phones for self-position calculation (see, for example, Patent Document 1). In mobile phones, etc., it is necessary to immediately calculate the self-position in response to a request from the user, so assist information is given to the mobile phone via the base station of the mobile phone to significantly reduce the positioning calculation time. A process called GPS (Assisted GPS) is performed.

However, if there is no means to transmit such assist information to the positioning terminal, it usually takes about 30 seconds to several minutes to start the positioning calculation, and efforts are being made to reduce this time to the theoretical limit. It is done by each manufacturer.

Time To First Fix, hereinafter abbreviated as TTFF. The time it takes to get the first position coordinates after turning on the receiver. ) Is lengthened in two main reasons, one is that it takes time to capture the positioning signal, and the other is that it takes time to acquire the satellite orbit parameters. Regarding the former, it is possible to shorten 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. Regarding the latter, it is the time required to acquire the satellite orbit parameter called Ephemeris obtained by decoding the navigation message after capturing the positioning signal, which currently takes about 18 to 30 seconds after capturing the signal. There is. Although the time required 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 the ephemeris broadcast from satellites (hereinafter referred to as "broadcast ephemeris"). Since it is possible to predict up to about a week ahead without much difference from the accuracy of "), it is possible to significantly shorten TTFF by using this. This predicted ephemeris is called Extended Ephemeris.

Infrastructure development is progressing, and an environment where it is easy to acquire information from wireless networks other than mobile phones is being prepared, so even if it is not possible to acquire all of the time, position, and ephemeris information in advance like assisted GPS, of these It is thought that the number of situations in which only Ephemeris can be acquired in advance will increase.

In this way, by shortening or reducing the signal acquisition time and ephemeris acquisition time, which were the main factors that made TTFF longer, the next important issue is to shorten the time required for other processing. Is becoming.

<p><patcit num="1"><text>Special Table 2007-504731</text></patcit></p>

<p><nplcit num="1"><text>European GNSS (Galileo) Open Service Signal In Space Interface Control Document, Issue 1</text></nplcit></p>

<p> As mentioned above, as infrastructure development progresses, the time required for signal acquisition and the time required for acquiring ephemeris, which used to be the main factors that lengthen TTFF, are shortened or reduced to zero, which reduces the time required for other processing. Shortening is becoming the next important issue.</p><p> The present invention has been made to solve such a problem, and is a satellite positioning receiver that aims to shorten the time until the pseudo distance generation is started in the reception of the positioning signal and further shorten the TTFF. The purpose is to obtain (receiver for SPS).</p>

<p> The present invention comprises a receiving antenna for SPS that receives RF signals from a plurality of satellites, and a front that performs front-end processing including amplification processing, filtering processing, and A / D conversion processing on the received RF signals. Pseudo-distance calculation and positioning based on the end means, the baseband processing means that obtains the signal propagation time by performing signal acquisition and tracking processing on the digital signal obtained by the front-end processing, and the signal propagation time. The baseband processing means includes a navigation calculation means for performing the calculation, and the baseband processing means includes the navigation included in the RF signal for the reference satellite whose SPS system time is obtained from the navigation message first among the plurality of satellites. The feature is that the signal propagation time is calculated by acquiring the time from the message, and for other satellites, the code phase difference between that satellite and the reference satellite is obtained, and the signal propagation time is calculated from the code phase difference. It is a satellite positioning receiver (receiver for SPS).</p>

<p> The present invention comprises a receiving antenna for SPS that receives RF signals from a plurality of satellites, and a front that performs front-end processing including amplification processing, filtering processing, and A / D conversion processing on the received RF signals. Pseudo-distance calculation and positioning based on the end means, the baseband processing means that obtains the signal propagation time by performing signal acquisition and tracking processing on the digital signal obtained by the front-end processing, and the signal propagation time. The baseband processing means is provided with a navigation calculation means for performing calculation, and among the plurality of satellites, the reference satellite whose SPS system time is obtained from the navigation message first is the navigation included in the RF signal. The feature is that the signal propagation time is calculated by acquiring the time from the message, and for other satellites, the code phase difference between that satellite and the reference satellite is obtained, and the signal propagation time is calculated from the code phase difference. Since it is a satellite positioning receiver (receiver for SPS), it has the effect of shortening the time until the pseudo distance generation is started in receiving the positioning signal and further shortening the TTFF.</p>

<figref num="1">It is a block diagram which showed the basic structure of the receiver for SPS which concerns on this invention.</figref><figref num="2">It is a block diagram which showed the basic structure of the receiver for SPS which concerns on this invention in the form of obtaining the ephemeris from an external network.</figref><figref num="3">It is a block diagram which showed the basic structure of the receiver for SPS which concerns on this invention in the form which obtains the ephemeris from the extended ephemeris calculation part.</figref><figref num="4">It is a block diagram which showed the structure of the baseband processing part provided in the receiver for SPS shown in FIGS. 1 to 3.</figref><figref num="5">It is a flow chart which showed the operation of the satellite signal tracking channel by the conventional method in the baseband processing part provided in the receiver for SPS shown in FIGS. 1 to 3.</figref><figref num="6">It is a flow chart which showed the operation of the satellite signal tracking channel until the start of pseudo-distance generation in this invention in the baseband processing part provided in the receiver for SPS shown in FIGS. 1 to 3.</figref><figref num="7">It is explanatory drawing which showed an example of the relationship between a code phase and a signal propagation time.</figref><figref num="8">It is explanatory drawing which showed another example of the relationship between a code phase and a signal propagation time.</figref>

FIG. 1 is a configuration diagram showing a basic configuration of a receiver for SPS 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, the RF front-end unit 2 performs front-end processing on the RF signal received from the satellite by the SPS receiving antenna 1. This front-end processing includes amplification processing, filtering 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 to obtain navigation data including ephemeris data and signal propagation time. Based on the result, the navigation calculation unit 4 generates observation raw data such as pseudo-distance, Doppler, and carrier phase, and also performs positioning calculation processing to calculate its own position and speed.

However, the effectiveness of the present invention can be particularly realized by the user of the receiver for SPS when the ephemeris can be obtained in advance from the communication network or the extended ephemeris can be used, and in such a case, the present invention of the present invention can be realized. The embodiments have the configurations shown in FIGS. 2 and 3, respectively.

FIG. 2 shows a configuration in which the navigation calculation unit 4 acquires the broadcast ephemeris or the 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 in FIG.

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

In any of the configurations shown in FIGS. 1 to 3, the baseband processing unit 3 incorporates a plurality of signal receiving channels 31 corresponding to the maximum number of satellites to be received, as shown in FIG. .. In order for each signal reception channel 31 to calculate the signal propagation time between the SPS satellite and the receiver for SPS, it is necessary not only to calculate the code phase, but also to synchronize the bits with the navigation message and obtain the time corresponding to the bits. It becomes. FIG. 5 shows a flow chart showing the operation of the satellite signal tracking channel by 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 FIGS. 1 to 3 is input to the baseband processing unit 3, first, in step S1, the baseband processing unit 3 signals the digital sampling data. Performs acquisition processing 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 those digital sampling data is completed, and if the acquisition processing is not completed, continues the processing of step S1. When the capture process is completed, the process proceeds to step S3. In step S3, the baseband processing unit 3 performs pull-in processing to substantially match the frequency of the captured signal with the frequency of the locally generated signal used for signal tracking processing. After the pull-in process is completed, in step S4, the baseband processing unit 3 performs the tracking process. In the tracking process, first, the bit synchronization process is performed in step S11 to recognize the bit position of the navigation data included in the received wave so that the bit of the received data can be extracted. After performing the bit synchronization processing, in step S12, each signal receiving channel 31 decodes the navigation message included in the signal and outputs the navigation data. Next, in step S13, the SPS system time corresponding to the signal is acquired from the navigation data obtained in step S12. Further, 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 appropriately set in the receiver for SPS. ..

At this time, the code phase of step S14 can be acquired immediately after the pull-in process of step S3, but the time of step S13 can be acquired, for example, in the case of GALILEO's E1 or E5-B navigation message (I / NAV). Due to its specifications, it takes up to 22 seconds. The 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 required when performing a general positioning calculation process performed using observation values of four or more satellites. Time matters.

Therefore, in the following embodiments 1 to 3 of the present invention, a pseudo distance is generated to shorten the time required for time acquisition when performing a general positioning calculation process performed using observation values of four or more satellites. The processing method and the receiver for SPS using it are shown.

When performing code positioning by pseudo distance using SPS, if a code with a long code length such as GALILEO's Tiered Code is used, each signal reception channel 31 of the positioning signal independently acquires the time corresponding to the received signal. The relative signal propagation time difference can be calculated without it. In the following embodiments 1 to 3, the relative signal propagation time difference is calculated so that the time until the start of positioning can be shortened as much as possible and the positioning calculation can be started in a shorter time (TTFF). Can be shortened).

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

However, in the case of GALILEO, there is a signal component such as E1 in which a Tiered Code on which a Secondary Code is superimposed is used, and the maximum code length is 100 [msec]. Normally, the arrival time difference of the positioning signal is within 30 [msec], so if the code phase obtained by using the Tiered Code is correctly interpreted, the signal propagation time difference of each satellite, that is, the pseudo distance difference can be calculated. This means that the pseudo distances of all satellites can be calculated by performing the above-mentioned "acquisition of transmission time" for only one satellite.

As described above, in the present invention, the time until the start of the pseudo-distance calculation is shortened and the time required for the start of positioning is shortened by using the Tiered Code which is not originally intended for calculating the pseudo-distance difference.

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

In FIG. 6, it is assumed that the code period of the code used for signal acquisition and tracking is sufficiently long (described later), and the code called Tiered Code of GALILEO corresponds to this. 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 of the reference satellite is signaled in step S20 of FIG. 6 without calculating the signal propagation time using the time acquired by its own signal receiving channel 31. It has a feature of acquiring the code phase of the reference satellite and the signal propagation time from the reception channel 31 and calculating the signal propagation time of the received signal. However, also in this embodiment as well, only for the reference satellite, the time is acquired from the navigation message by the conventional method shown in FIG. 5 to generate a pseudo distance, and for the other satellites, FIG. 6 The signal propagation time is calculated from the code phase difference between the satellite and the reference satellite by the method shown in.

In the conventional method of FIG. 5, in each signal receiving 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 is obtained. The signal propagation time is calculated based on the time acquired in step S13 using the phase and the receiver time set in the receiver (step S15). Here, the receiver time is a time appropriately set based on the time acquired by the signal reception channel 31 of the reference satellite, etc., and does not necessarily have to be accurate, and an error of about 10 [msec] is allowed. Will be done. Normally, the range of possible values of the signal propagation time is determined according to the altitude to be used, so that 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, each signal receiving channel 31 acquires navigation data such as the time corresponding to the signal from the navigation message included in the signal, but the time is the signal propagation time as in the method of FIG. Not required for calculation (step S20). Instead, the code phase and signal propagation time of the reference satellite are obtained, and the code phase calculated in step S14 is used to calculate the signal propagation time of the received signal from satellites other than the reference satellite ( Step S20). As a result, the signal propagation time calculation can be started without waiting for the completion of the time acquisition process (step S13) in FIG. It has the effect of shortening.

Now, the code phase of a certain signal reception channel 31 is set to φ_c[chip], set the code phase of the reference satellite to φ_{c, r}[chip], set the code length of the code used for tracking to L_c[chip], code cycle T_c[s], the signal propagation time of the reference satellite is Δt_rIf [s], the signal propagation time of satellite k Δt_k[s] is expressed as follows.

<maths num="1"><img file="JP2011237333A_D0001.tif" /></maths>

However, in the first embodiment, the code cycle T_cIs 0.1 [s] and the code phase φ_cThe time conversion value of [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 shown in the example of FIG. 7, when the time-converted values of the code phases of A, B, C, D, and E are all within the width of 40 [msec], the larger the code phase, the longer the signal propagation time. Is large, so N = 0 in the above equation (1). On the other hand, as shown in the example of FIG. 8, the code phase is L._cWhen the code phase is divided into small and large code phases with / 2 as the boundary and the total of the code phase distribution sections of both is within 40 [msec], the signal propagation times of D and E are A, B, and C. Since it is smaller than the signal propagation time of, it is necessary to determine N by the positional relationship of the code phase with the reference satellite. For example, if the reference satellite is A, B, or C, Δt other than the reference satellite._A, Δt_B, Δt_CIn the calculation of, N = 0, but Δt_D, Δt_EIn the calculation of, N = -1. If the reference satellite is either D or E, Δt other than the reference satellite_D, Δt_EIn the calculation of, N = 0, but Δt_A, Δt_B, Δt_CIn the calculation of, N = + 1. Even if the number of observation satellites is different from the example in Fig. 8, N can be determined by the same logic. In cases other than the above (Figs. 7 and 8), the observed values include abnormal values, so the observed results are rejected.

In order to determine N by the condition 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 [ The difference between [s] and the longest arrival time [s] is (2 + α) times the code length [s] or less. α should be 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 by using, for example, a Tiered Code obtained by superimposing a Primary Code and a Secondary Code on signal components called E1-C, E5a-Q, and E5b-Q among the positioning signals of GALILEO. , The code length is 0.1 [s] (see Non-Patent Document 1). Therefore, when α = 0.5, the difference between the shortest arrival time and the longest arrival time of the positioning signal may be 0.04 [s] or less. .. The positional relationship between the Earth, the SPS satellite, and the SPS receiver requires conditions for the SPS receiver to satisfy this condition. In the case of GALILEO, the altitude of the SPS receiver should be approximately 1600 [km] or less. Can be calculated.

The signal propagation time obtained by the above equation (1) becomes a pseudo distance by multiplying the speed of light c = 2.979792458e + 8 [m / s], and normally, if observation values of 4 satellites or more are obtained, autonomous positioning calculation is performed. It can be performed.

Once the signal propagation time of each satellite can be calculated by the equation (1), the signal propagation time of each satellite can be calculated by the following equation without using the observed value of the reference satellite.

<maths num="2"><img file="JP2011237333A_D0002.tif" /></maths>

In equation (2), N_TIs a code ambiguity in observations using Tiered Code and is always an integer value, R_c[s] is a fraction of the distance. Δt in Eq. (1) according to the observed value at a certain moment_kIf is determined, R is determined by equation (2)._cThe absolute value of is T_cInteger value N to be less than_TTo determine. N_TAnd R_cOnce determined, the code phase φ of each satellite will be observed from the next observation._cYou can update the observations using only.

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

As described above, according to the first embodiment, the reference satellite whose SPS system time is first acquired from the navigation data among the plurality of satellites is subjected to the pseudo-distance generation by the conventional method. For satellites other than the above, by calculating the signal propagation time from the code phase difference between the satellite and the reference satellite, the effect of significantly shortening the time required to start pseudo-distance generation can be obtained. In addition, even if the observation of the reference satellite is interrupted, the effect of shortening the time required to start the pseudo-distance generation of the newly started satellite will continue.

Embodiment 2. The present embodiment is basically the same as the first embodiment, but 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 primary code is used at the time of signal acquisition, and when the signal acquisition is completed, a method of shifting to the tiered code from that point is used. 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 by inspecting 25 types of code timings after capturing the signal by the Primary Code. In signal acquisition, the processing after the transition to Tiered Code is exactly the same as in the first embodiment.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and further, in the present embodiment, the primary code is used at the time of signal acquisition, and the signal acquisition is completed. Then, since the transition to Tiered Code is performed from that point, the time required for searching for the code phase can be shortened as compared with the case where signal acquisition is performed using Tiered Code with a long code length.

Embodiment 3. This embodiment is also basically the same as that of the first embodiment, but since it is not necessary to continue using the Tiered Code after the code phase difference with the reference satellite is found by the Tiered Code, in the present embodiment, it is not necessary to continue using the Tiered Code. After the code phase difference with the reference satellite is found, the code tracking process using the Primary Code will be started. This can be done by the signal propagation time Δt according to Eq. (2) in the positioning by Tiered Code._kWhen is calculated, the so-called code ambiguity is solved, so the code ambiguity can also be determined for the code phase according to the Primary Code, and the signal propagation time Δt_kIs possible. This is explained using the following equation.

<maths num="3"><img file="JP2011237333A_D0003.tif" /></maths>

First, at a certain observation timing, the code phase φ according to the Tiered Code_cCode phase φ by [chip] and Primary Code_cpGet [chip] at the same time. At this time, Δt according to Eq. (2)_kIs determined, so the integer code ambiguity N in equation (3)_PAnd the constant R_cpBy determining, it is possible to shift to the observation value generation using the Primary Code according to Eq. (3). Here, the code length of Primary Code is L_cp[chip], set the code cycle of Primary Code to T_cpIt was set to [s]. Code Ambiguity N_PAnd the constant R_cpIs determined by the constant R in Eq. (2)._cSimilar to R_cpThe absolute value of is T_cpInteger N to be less than_PJust decide.

As described above, according to the third embodiment, the same effect as that of the first embodiment can be obtained, and further, in the present embodiment, the code phase difference from the reference satellite is obtained by the Tiered Code. After that, since the transition to Primary Code is performed, the time required for tracking processing can be shortened compared to the case where tracking processing is performed using Tiered Code with a long code length, and tracking for high mobility movements can be performed. The processing capacity can be increased.

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

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

1 SPS receiving antenna, 2 RF front end, 3 baseband processing, 4 navigation calculator, 5 communication equipment, 6 extended ephemeris calculator, 31 signal receiving channels.