JP2006317225A - Satellite radio waves receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a satellite radio waves receiver which can reduce positioning time at a cold start. <P>SOLUTION: The satellite radio waves receiver for receiving radio waves radiated from a satellite of a positioning system comprises a quasi-zenith satellite search means for searching for a quasi-zenith satellite and a non-quasi-zenith satellite search means for searching for a non-quasi-zenith satellite after searching for the quasi-zenith satellite by the quasi-zenith satellite search means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a satellite radio wave receiver, and more particularly to a satellite radio wave receiver that receives radio waves radiated from a satellite of a positioning system.

  As a positioning system that receives a signal radio wave from a satellite and measures its own position, there is a system using a GPS (Global Positioning System) satellite, a GLONASS (Global Navigation Satellite System) satellite, or the like.

  For example, in Patent Document 1, GPS satellite information that can be used for positioning is grasped at a reference station, and the GPS satellite information is transmitted to a quasi-zenith satellite. Further, it is described that the quasi-zenith satellite transmits the GPS satellite information to the mobile terminal, thereby speeding up and increasing the efficiency of the process at the cold start of the mobile terminal device.

Further, in Patent Document 2, when all GPS satellite radio waves become unreceivable, the search range of the reception frequency of the satellite radio waves is divided into a plurality of frequency bands, and each channel is allocated to search for a predetermined elevation position. Thus, it is described that the search range is narrow and the re-acquisition time is shortened.
JP 2004-28593 A Japanese Examined Patent Publication No. 7-48076

  In the technology described in Patent Document 1, since the quasi-zenith satellite is used as a relay means for information transmission on the premise of communication from the reference station to the mobile terminal device, there is a problem that the cost of the reference station and communication equipment increases. there were.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a satellite radio wave receiver that can shorten the time required for positioning (TTFF: Time To First Fix) at a cold start.

The satellite radio wave receiver of the present invention is a satellite radio wave receiver that receives radio waves radiated from a satellite of a positioning system.
A quasi-zenith satellite search means for searching for a quasi-zenith satellite;
By having a non-quasi-zenith satellite search means for searching for a non-quasi-zenith satellite after the search of the quasi-zenith satellite by the quasi-zenith satellite search means,
The frequency search time of the quasi-zenith satellite can be shortened, and thereby the time required for positioning at the cold start can be shortened.

  Further, the quasi-zenith satellite search means of the satellite radio wave receiver can end the search for the quasi-zenith satellite when it successfully searches for one quasi-zenith satellite.

Further, the quasi-zenith satellite search means of the satellite radio wave receiver searches for all quasi-zenith satellites,
When the number of quasi-zenith satellites is four or more, all the quasi-zenith satellites existing near the zenith can be searched, and the time required for positioning can be further shortened.

In addition, the satellite radio wave receiver has a zenith satellite position information storage means for storing the order of searching for the quasi-zenith satellite according to the time zone,
The quasi-zenith satellite search means obtains the search order of the quasi-zenith satellite according to the current time from the zenith satellite position information storage means, and searches for the quasi-zenith satellite,
The time required for satellite search of the quasi-zenith satellite can be reduced, and the time required for positioning can be further reduced.

  According to the present invention, it is possible to reduce the time required for positioning at a cold start.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is a geodetic system using a quasi-zenith satellite that Japan plans to launch in the future. Here, the quasi-zenith satellite is a satellite in which at least one aircraft is always arranged near the zenith in the service area. The signal radio wave from the quasi-zenith satellite is less likely to be blocked even in the valleys of the building, so it is advantageous for use in a positioning system.

  There are various studies on the number of quasi-zenith satellites, but one study includes three. In this case, the elevation angle that can be serviced by the quasi-zenith satellite is 70 degrees in the main areas of Japan and 60 degrees or more in the entire area of Japan, which is very large compared to GPS satellites and the like.

  FIG. 1 shows a block diagram of an embodiment of the satellite radio wave receiver of the present invention. In the figure, an antenna 11 receives a signal radio wave from a satellite and supplies it to an RF unit 12. The RF unit 12 down-converts the received signal and supplies it to the acquisition unit 13 as an intermediate frequency signal.

  The acquisition unit 13 searches for the satellite from which the signal is received by synchronizing the C / A code, and notifies the tracking unit 14 of the C / A code and synchronization timing of the synchronized satellite. The tracking unit 14 reproduces the navigation message of each satellite from the intermediate frequency signal supplied from the RF unit 12 based on the C / A code and the synchronization timing of each satellite notified from the acquisition unit 13, and the signal of each satellite. Keep tracking exactly.

  FIG. 2 shows a block diagram of an embodiment of a GPS satellite and a quasi-zenith satellite. In the figure, a navigation message generator 20 generates a navigation message of ± 1 signal indicating satellite orbit information, clock information, etc., and supplies it to a multiplier 21. The carrier wave generator 22 generates a carrier wave having a predetermined frequency (1.57542 GHz in the case of GPS) and supplies the carrier wave to the multiplier 21.

  The multiplication unit 21 performs PSK modulation by multiplying the navigation message and the carrier wave, and the obtained modulated wave is supplied to the multiplication unit 23. The C / A code generator 24 generates a C / A code, which is a periodic ± 1 signal unique to each satellite, and supplies it to the multiplier 23. The multiplication unit 23 performs code spreading by multiplying the modulated wave and the C / A code. The spread signal obtained here is radiated as radio waves.

FIG. 3 shows a block diagram of an embodiment of the acquisition unit 13 of the satellite radio wave receiver of the present invention. In the figure, an intermediate frequency signal output from the RF unit 12 is input to a terminal 30 and supplied to a multiplication unit 31. The carrier wave generation unit 32 generates a carrier wave having a frequency obtained by adding the Doppler frequency f _dr to the intermediate frequency f _{if under} the control of the control unit 33 and supplies the carrier wave to the multiplication unit 31.

  The multiplier 31 performs PSK demodulation by multiplying the intermediate frequency signal and the carrier wave, and supplies the obtained demodulated signal to the matched filter 34. The matched filter 34 generates a copy of the C / A code of each satellite under the control of the control unit 33, and performs a search process for synchronizing the copy of the C / A code of each satellite with the C / A code in the demodulated signal. .

  When the copy of the C / A code is synchronized with the C / A code in the demodulated signal, the matched filter 34 generates a signal representing the synchronization timing and supplies it to the subsequent tracking unit 14 together with the synchronized copy of the C / A code.

Here, in the acquisition unit 13, it is first necessary to determine which satellite is to be searched (satellite search). Further, since the Doppler frequency f _dr due to the radio wave being emitted while the satellite is moving is unknown, it is necessary to search for this (frequency search).

In the case of a GPS satellite, since the elevation angle of the satellite is low, the Doppler frequency f _dr covers a range of ± 5 kHz. Normally, in the frequency search, since the Doppler frequency f _dr is changed in units of 0.5 kHz and repeated until the C / A code is synchronized, this frequency search requires a long time.

  By the way, the Doppler frequency included in the satellite signal decreases as the elevation angle of the satellite increases. The elevation angle of the quasi-zenith satellite is 70 degrees in the main areas of Japan and 60 degrees or more in the whole area of Japan, which is much larger than that of GPS satellites. Therefore, the Doppler frequency of the quasi-zenith satellite is smaller than that of the GPS satellite.

  FIG. 4 shows the relationship (calculation example) between the elevation angle of the quasi-zenith satellite and the Doppler frequency of the quasi-zenith satellite. As is apparent from this figure, the Doppler frequency of the quasi-zenith satellite is about ± 1200 Hz or less throughout Japan, and is about ± 800 Hz or less in the main areas of Japan. This is considerably smaller than the GPS satellite Doppler frequency of ± 5 kHz or less. The present invention utilizes this property to speed up the search process.

<First Embodiment>
FIG. 5 shows a flowchart of a first embodiment of search processing executed by the control unit 33 of the satellite radio wave receiver of the present invention at a cold start. Here, the Doppler frequency of the quasi-zenith satellite in the main region of Japan is ± 800 Hz, and in order to search this range every 400 Hz in order from the lowest Doppler frequency, f _dr (1) = 0 {Hz], f _{In the} control unit 33, _dr (2) = 400 {Hz], f _dr (3) = − 400 {Hz], f _dr (4) = 800 {Hz], f _dr (1) = − 800 {Hz] It is set in advance in the memory.

Further, the number of quasi-zenith satellites is represented by i _qz (where i _qz is 1, 2, 3), and the total number of quasi-zenith satellites i _qzmax (= 3) and the number of searches for the Doppler frequency i _drmax (= 5) are controlled. It is set in advance in the internal memory of the unit 33.

In the figure, the number of the quasi-zenith satellite to be searched is set to 1 in i _qz in step S101, and 1 is set to the index i _dr of the Doppler frequency in step S102.

Next, in step S103, the carrier wave generation unit 32 is caused to generate a frequency obtained by adding the Doppler frequency f _dr (i _dr ) to the intermediate frequency f _if of the quasi-zenith satellite. In addition, the matched filter 34 is instructed to replicate the C / A code of the _iqz- th quasi-zenith satellite, and the synchronization phase for detecting the coincidence between the C / A code replication and the C / A code in the demodulated signal. Make a search.

  Next, it is determined whether or not the C / A code is synchronized in step S104. If the synchronization is established, the process proceeds to step S105. If the synchronization is not established, the process proceeds to step S107.

If synchronization is established, the matched filter 34 is caused to output a C / A code copy of the synchronized _iqz quasi-zenith satellite and a synchronization timing signal to the tracking unit 14 in step S105. Thereafter, in step S106, a search is made for a non-quasi-zenith satellite, that is, a satellite other than the quasi-zenith satellite (for example, a GPS satellite). The search for non-quasi-zenith satellites such as GPS satellites is conventional.

If synchronization is not _{achieved in} step S104, it is determined in step S107 whether or not the index i _dr matches the search number i _{drmax. If} they do not match, the index i _dr is incremented by 1 in step S109 and the process proceeds to step S103. Steps S103 and S104 are repeated.

On the other hand, the process proceeds to step S108 if the index _{i dr} matches the search number _{i DRmax} in step S107, quasi number _{i qz} zenith satellite to determine whether to match the total number _{i Qzmax} of QZSS, mismatch In step S110, the number i _qz is incremented by 1 and the process proceeds to step S102, and steps S102, S103, S104, S105 or S107 and 109 are repeated.

If the quasi-zenith satellite number i _qz matches the total number of quasi-zenith satellites i _{qzmax in} step S108, the process proceeds to step S106 to search for satellites other than the quasi-zenith satellite.

  In this way, it is possible to shorten the frequency search time of the quasi-zenith satellite, thereby shortening the time required for positioning at the cold start.

Second Embodiment
In the first embodiment, when a search for one quasi-zenith satellite is successful, the process immediately proceeds to a search for GPS satellites other than the quasi-zenith satellite. However, if the number of quasi-zenith satellites is 4 or more, there may be a plurality of quasi-zenith satellites near the zenith depending on the orbit. It is an embodiment.

FIG. 6 shows a flowchart of a second embodiment of search processing executed by the control unit 33 of the satellite radio wave receiver of the present invention at a cold start. Here, the Doppler frequency of the quasi-zenith satellite in the main region of Japan is ± 800 Hz, and in order to search this range every 400 Hz in order from the lowest Doppler frequency, f _dr (1) = 0 {Hz], f _{In the} control unit 33, _dr (2) = 400 {Hz], f _dr (3) = − 400 {Hz], f _dr (4) = 800 {Hz], f _dr (1) = − 800 {Hz] It is set in advance in the memory.

The number of the quasi-zenith satellite is represented by i _qz (where i _qz is 1, 2, 3... N), the total number of quasi-zenith satellites i _qzmax (= n), and the number of searches for the Doppler frequency i _drmax (= 5). Is set in advance in the built-in memory of the control unit 33.

In the figure, the number of the quasi-zenith satellite to be searched is set to 1 in i _qz in step S201, and 1 is set to the index i _dr of the Doppler frequency in step S202.

Next, in step S203, the carrier wave generation unit 32 is caused to generate a frequency obtained by adding the Doppler frequency f _dr (i _dr ) to the intermediate frequency f _if of the quasi-zenith satellite. In addition, the matched filter 34 is instructed to replicate the C / A code of the _iqz- th quasi-zenith satellite, and the synchronization phase for detecting the coincidence between the C / A code replication and the C / A code in the demodulated signal. Make a search.

  Next, in step S204, it is determined whether or not the C / A code is synchronized. If synchronized, the process proceeds to step S205. If not synchronized, the process proceeds to step S207.

When the synchronization is established, the matched filter 34 is caused to output the C / A code copy of the synchronized _iqz quasi-zenith satellite and the synchronization timing signal to the tracking unit 14 in step S205. Thereafter, the process proceeds to step S208.

If synchronization is not _{achieved in} step S204, it is determined in step S207 whether or not the index i _dr matches the search number i _{drmax. If} they do not match, the index i _dr is incremented by 1 in step S209 and the process proceeds to step S203. Steps S203 and S204 are repeated.

On the other hand, if the index i _dr matches the search number i _drmax in step S207, the process proceeds to step S208.

In step S208, the number _{i qz} of QZSS, it is determined whether or not to match the total number _{i Qzmax} quasi-zenith satellite, the process proceeds to step S202 to increment the case of disagreement in step S210 the number _{i qz} only 1, step S202, S203, S204, S205 or S207 and S209 are repeated.

If the quasi-zenith satellite number i _qz matches the total number of quasi-zenith satellites i _{qzmax in} step S208, the process proceeds to step S206 to search for a non-quasi-zenith satellite, that is, a satellite other than the quasi-zenith satellite. The search for non-quasi-zenith satellites such as GPS satellites is conventional.

  In this way, when the number of quasi-zenith satellites is 4 or more, all quasi-zenith satellites existing near the zenith can be searched, and positioning can be performed if at least three satellites can be captured. Can be further shortened.

<Third Embodiment>
In the first and second embodiments described above, the order in which the quasi-zenith satellites are searched is not particularly mentioned. However, if the number of quasi-zenith satellites and the operation method such as orbits are known, it is possible to predict which quasi-zenith satellites can be captured at a cold start. When each quasi-zenith satellite makes one round of the earth in 8 hours, a zenith satellite position information storage unit shown in FIG. 7 in which the time zone and the search order of the quasi-zenith satellite are registered in advance is provided in the control unit 33. The search order is an order that is highly likely to exist in the sky in each time zone.

  The search time can be further shortened by referring to the zenith satellite position information storage unit in FIG. 7 at the time when the cold start is performed. For example, when a cold start is performed at time 1:30, the second row of the zenith satellite table is referenced, and the search is performed in the order of the quasi-zenith satellites B, C, and A.

FIG. 8 shows a flowchart of a third embodiment of search processing executed by the control unit 33 of the satellite radio wave receiver of the present invention at a cold start. Here, the Doppler frequency of the quasi-zenith satellite in the main region of Japan is ± 800 Hz, and in order to search this range every 400 Hz in order from the lowest Doppler frequency, f _dr (1) = 0 {Hz], f _{In the} control unit 33, _dr (2) = 400 {Hz], f _dr (3) = − 400 {Hz], f _dr (4) = 800 {Hz], f _dr (1) = − 800 {Hz] It is set in advance in the memory.

The number of the quasi-zenith satellite is represented by i _qz (where i _qz is 1, 2, 3... N), the total number of quasi-zenith satellites i _qzmax (= n), and the number of searches for the Doppler frequency i _drmax (= 5). Is set in advance in the built-in memory of the control unit 33.

  In the figure, in step S301, using the current time, the zenith satellite position information storage unit in FIG. 7 is referred to obtain the quasi-zenith satellite search order, and in step S302, this is determined in the quasi-zenith satellite search order.

Next, in step S311, the number of the quasi-zenith satellite to be searched is set to 1 in i _qz , and in step S312, 1 is set to the index i _dr of the Doppler frequency.

Next, in step S313, the carrier wave generation unit 32 generates a frequency obtained by adding the Doppler frequency f _dr (i _dr ) to the intermediate frequency f _if of the quasi-zenith satellite. In addition, the matched filter 34 is instructed to replicate the C / A code of the _iqz- th quasi-zenith satellite, and the synchronization phase for detecting the coincidence between the C / A code replication and the C / A code in the demodulated signal. Make a search.

  Next, in step S314, it is determined whether or not the C / A code is synchronized. If synchronized, the process proceeds to step S315, and if not synchronized, the process proceeds to step S317.

When synchronization is established, the matched filter 34 is caused to output a C / A code copy of the synchronized _iqz quasi-zenith satellite and a synchronization timing signal to the tracking unit 14 in step S315. Thereafter, the process proceeds to step S318.

If synchronization is not established in step S314, it is determined in step S317 whether or not the index i _dr matches the search number i _{drmax. If} they do not match, the index i _dr is incremented by 1 in step S319 and the process proceeds to step S313. Steps S313 and S314 are repeated.

On the other hand, if the index i _dr matches the search number i _drmax in step S317, the process proceeds to step S318.

In step S318, the number _{i qz} of QZSS, it is determined whether or not to match the total number _{i Qzmax} quasi-zenith satellite, the process proceeds to step S312 to increment the case of disagreement in step S320 the number _{i qz} only 1, step S312, S313, S314, S315 or S317 and S319 are repeated.

If number i _qz of QZSS matches the total number i _Qzmax of QZSS in step S318 advances to step S316, performs the search of the non-non-QZSS That QZSS satellites. The search for non-quasi-zenith satellites such as GPS satellites is conventional.

  In this way, it is possible to shorten the time required for satellite search of the quasi-zenith satellite and further reduce the time required for positioning.

  In the third embodiment, the zenith satellite position information storage unit of FIG. 7 is applied to the second embodiment. Similarly, the zenith satellite position information storage unit of FIG. 7 is applied to the first embodiment, and Steps S301 and S302 may be executed before step S101 in FIG.

  Steps S101 to S105, S107 to S110, Steps S201 to S205, S207 to S210, or Steps S301 to S315, and S317 to S320 correspond to the quasi-zenith satellite search means described in the claims, and Steps S106, S206, and S316 are not. It corresponds to the quasi-zenith satellite search means, and the zenith satellite position information storage unit corresponds to the zenith satellite position information storage means.

It is a block diagram of one embodiment of a satellite radio wave receiver of the present invention. 2 is a block diagram of one embodiment of a GPS satellite and a quasi-zenith satellite. FIG. It is a block diagram of one Embodiment of the acquisition part of the satellite radio wave receiver of this invention. It is a figure which shows the relationship between the elevation angle of a quasi-zenith satellite, and the Doppler frequency of a quasi-zenith satellite. It is a flowchart of 1st Embodiment of the search process which the control part of the satellite radio wave receiver of this invention performs at the time of a cold start. It is a flowchart of 2nd Embodiment of the search process which the control part of the satellite radio wave receiver of this invention performs at the time of a cold start. It is a figure which shows the content of the zenith satellite position information storage part. It is a flowchart of 3rd Embodiment of the search process which the control part of the satellite radio wave receiver of this invention performs at the time of a cold start.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Antenna 12 RF part 13 Acquisition part 14 Tracking part 20 Navigation message generation part 21,23,31 Multiplication part 22,32 Carrier wave generation part 24 C / A code generation part 34 Matched filter

Claims (4)

In satellite radio receivers that receive radio waves emitted from positioning system satellites,
A quasi-zenith satellite search means for searching for a quasi-zenith satellite;
A satellite radio wave receiver having non-quasi-zenith satellite search means for searching for a non-quasi-zenith satellite after the quasi-zenith satellite search by the quasi-zenith satellite search means. The satellite radio wave receiver according to claim 1,
The quasi-zenith satellite search means terminates the quasi-zenith satellite search upon successful search of one quasi-zenith satellite. The satellite radio wave receiver according to claim 1,
The quasi-zenith satellite search means searches for all quasi-zenith satellites. The satellite radio wave receiver according to claim 2 or 3,
Zenith satellite position information storage means storing the order of searching the quasi-zenith satellite according to the time zone,
The quasi-zenith satellite search means obtains a search order of quasi-zenith satellites according to the current time from the zenith satellite position information storage means, and searches for a quasi-zenith satellite.

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