JP2007263598A - Apparatus and method for controlling time correction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To speedily and highly accurately correct time through the use of time information included in GPS signals. <P>SOLUTION: When it is determined that predetermined codes (for example, a synchronization preamble code at the head of TLM and a two-bit code at the end of HOW) included in subframes constituting navigation messages by received GPS signals match each other or that a code of satellite health conditions SVhealth match a predetermined reference code, a CPU 8 provided for a GPS receiving device corrects time through the use of time information in subframes which have been determined as matching. Alternately, when it is determined that a code of range-finding accuracy URA does not match a predetermined reference code, the CPU 8 corrects time through the use of time information in subframes which have been determined as not matching. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a time correction control device and a time correction control method for correcting time using time information of a GPS signal.

  Currently, in each country (for example, Japan, the United States, the United Kingdom, Germany, etc.), a time code, that is, a long-wave standard radio wave with a time code (hereinafter simply referred to as “standard radio wave”) is transmitted. In Japan (Japan), standard radio waves of 40 kHz and 60 kHz, which are amplitude-modulated with a standard time code of a predetermined format, are transmitted from two transmitting stations (Fukushima Prefecture and Saga Prefecture). This time code is transmitted in a frame of one cycle of 60 seconds every time the minute digit of the correct time is updated, that is, every minute. There is known a time information receiving device called a so-called radio clock that receives this time code and thereby corrects time data (hereinafter referred to as “internal time” as appropriate) of a clock circuit.

A conventional time information receiving apparatus receives a time code at a fixed number of times such as 3 times continuously at a fixed time such as 3 am, and corrects the internal time (see, for example, Patent Document 1). By acquiring the time code for three times and correcting the internal time, it is possible to improve the accuracy of time correction as compared with the case of performing the time code for one time.
JP-A-7-198878 JP-A-8-15463

  However, in the above prior art, in order to accurately correct the internal time, it may take about 10 minutes from the start of reception of the standard time information.

On the other hand, in a GPS (Global Positioning System) signal, a HOW (handover word) including time information is included in each subframe and is transmitted from each GPS satellite every 6 seconds.
Therefore, if a method of correcting the internal time using the time information of the GPS signal is taken, the time required for the time correction can be shortened. For example, Patent Document 2 describes a time correction device for a clock that corrects internal time using time information of a GPS signal.
However, some technique is required to accurately correct the internal time. In addition, a technique that does not prolong the time correction processing as much as possible is desirable.

  The present invention has been made in view of the above problems in the prior art, and not only can the time be corrected quickly and accurately using the time information included in the GPS signal, but also the power consumption can be reduced. It is an object of the present invention to provide a time correction control device and a time correction control method capable of achieving the above.

The invention according to claim 1 for solving the above-described problem is a receiving means for receiving a GPS signal (for example, the antenna and the tuner circuit unit 2 in FIG. 1);
Discriminating means for discriminating whether or not a predetermined code included in a subframe constituting a navigation message based on a GPS signal received by the receiving means matches a predetermined reference code (for example, FIG. CPU8; S4, S5 in FIG. 9; T3 in FIG.
Time correction control means (for example, the CPU 8 in FIG. 1; S6 in FIG. 9 and FIG. 10) for correcting the time using the time information in the subframe determined to be the same by the determination means;
A time correction control device comprising:

The invention according to claim 2 is a receiving means for receiving a GPS signal (for example, the antenna 1 and the tuner circuit unit 2 in FIG. 1);
The synchronization preamble code at the head of the telemetry word and the code of the last 2 bits of the handover word included in the subframe constituting the navigation message by the GPS signal received by the receiving means are each one of a predetermined reference code and a predetermined reference code. Discrimination means (eg, CPU 8 in FIG. 1; S4 and S5 in FIG. 9) for discriminating whether or not
Time correction control means (for example, CPU 8 in FIG. 1; S6 in FIG. 9) for correcting the time using the time information in the handover word determined to be the same by the determination means;
A time correction control device comprising:

The invention described in claim 3 is a receiving means for receiving GPS signals (for example, the antenna 1 and the tuner circuit unit 2 in FIG. 1);
Discriminating means (for example, CPU 8 in FIG. 1) for discriminating whether the code of the satellite health state included in the subframe constituting the navigation message based on the GPS signal received by the receiving means matches a predetermined reference code. ; T3 in FIG. 10;
Time correction control means (for example, CPU 8 in FIG. 1; S6 in FIG. 10) for correcting the time using the time information in the subframe determined to be the same by the determination means;
A time correction control device comprising:

The invention according to claim 4 is a receiving means for receiving a GPS signal (for example, the antenna 1 and the tuner circuit section 2 in FIG. 1);
Discriminating means (for example, CPU 8 in FIG. 1) for discriminating whether or not the ranging accuracy code included in the subframe constituting the navigation message based on the GPS signal received by the receiving means matches a predetermined reference code. ; T4 in FIG.
Time correction control means (for example, the CPU 8 in FIG. 1; S6 in FIG. 10) for correcting the time using the time information in the subframe determined to be inconsistent by the determination means;
A time correction control device comprising:

  According to a fifth aspect of the present invention, when the time is adjusted by the control of the time adjustment control means, the reception means prohibits the reception operation of the GPS signal by the reception means until a predetermined time elapses. The time correction control device according to any one of claims 1 to 4, further comprising operation prohibition control means (for example, a CPU 8 in FIG. 1; S7 to S9 in FIGS. 9 and 10). It is.

The invention according to claim 6 is a reception step of receiving a GPS signal (for example, S1 in FIGS. 9 and 10),
A determination step for determining whether or not a predetermined code included in a subframe constituting the navigation message based on the GPS signal received in the reception step matches a predetermined reference code (for example, FIG. S4, S5; T3 in FIG.
A time correction control step (for example, S6 in FIG. 9; S6 in FIG. 10) for correcting the time using the time information in the subframe determined to be coincident in the determination step;
A time correction control method characterized by comprising:

The invention according to claim 7 is a reception step of receiving a GPS signal (for example, S1 in FIG. 9);
A reference preamble code in which a synchronization preamble code at the beginning of a telemetry word and a code of the last 2 bits of a handover word included in a subframe constituting a navigation message by a GPS signal received by the reception step are respectively determined in advance. A determination step (for example, S4 and S5 in FIG. 9) for determining whether they match,
A time correction control step (for example, S6 in FIG. 9) that corrects the time using the time information TOW in the handover word that is determined to match by the determination step;
A time correction control method characterized by comprising:

The invention according to claim 8 is a reception step of receiving a GPS signal (for example, S1 in FIG. 10),
A determination step (for example, T3 in FIG. 10) for determining whether the code of the satellite health state included in the subframe constituting the navigation message based on the GPS signal received by the reception step matches a predetermined reference code. )When,
A time correction control step (S6 in FIG. 10) that corrects the time using the time information in the subframe determined to match by the determination step;
A time correction control method characterized by comprising:

The invention according to claim 9 is a reception step of receiving a GPS signal (for example, S1 in FIG. 10);
A determination step (for example, T4 in FIG. 10) for determining whether a code for ranging accuracy included in a subframe constituting a navigation message based on the GPS signal received in the reception step matches a predetermined reference code. )When,
A time correction control step (S6 in FIG. 10) for correcting the time using the time information in the subframe determined to be inconsistent by the determination step;
A time correction control method characterized by comprising:

  According to a tenth aspect of the present invention, when the time is corrected by the control of the time correction control step, the reception of prohibiting the reception operation of the GPS signal by the reception step until a predetermined time elapses. The time correction control method according to any one of claims 6 to 9, further comprising an operation prohibition control step (for example, S7 to S9 in FIGS. 9 and 10).

The invention described in claim 11 is a receiving means for receiving a GPS signal (for example, the antenna of FIG. 1, the tuner circuit unit 2),
A discriminating unit (for example, discriminating whether or not the same time information is normal with reference to other predetermined information other than the time information in the subframe constituting the navigation message by the GPS signal received by the receiving unit) 1; S4, S5 in FIG. 9; T3, T4 in FIG.
If it is determined that the time information is normal by this determination means, the time correction control means (for example, the CPU 8 in FIG. 1; FIG. 9, FIG. 10) that corrects the time using the time information in the subframe. S6)
A time correction control device comprising:

The invention described in claim 12 is the time correction control device according to claim 11,
The other predetermined information is at least one information of a synchronization preamble code at the beginning of the telemetry word, a 2-bit code at the end of the handover word, a satellite health condition code, and a ranging accuracy code. There is a time correction control device characterized by that.

The invention according to claim 13 is a reception step of receiving a GPS signal (for example, S1 in FIGS. 9 and 10),
A determination step (for example, determining whether the time information is normal by referring to other predetermined information other than the time information in the subframe constituting the navigation message by the GPS signal received by the reception step) , S4 and S5 in FIG. 9; T3 and T4 in FIG.
If it is determined in this determination step that the time information is normal, a time correction control step (for example, S6 in FIG. 9; S6 in FIG. 10) for correcting the time using the time information in the subframe; ,
A time correction control method characterized by comprising:

The invention according to claim 14 is the time correction control method according to claim 13,
The other predetermined information is at least one information of a synchronization preamble code at the beginning of the telemetry word, a 2-bit code at the end of the handover word, a satellite health condition code, and a ranging accuracy code. It is a time correction control method characterized by being.

According to the present invention, by referring to other predetermined information other than the time information in the subframe constituting the received navigation message and determining whether or not the same time information is normal, If it is determined that the time information is normal, the time is corrected using the time information in the subframe.
For example, reference is made to the synchronization preamble code at the beginning of the telemetry word, the code of the last 2 bits of the handover word, the code of the satellite health status, the code of the ranging accuracy, and the like.
When the synchronization preamble code at the beginning of the telemetry word, the last two bits of the handover word, and the satellite health code are determined to match a predetermined reference code, the sub-code determined to match. The time is corrected using the time information in the frame. Alternatively, when it is determined that the distance measurement accuracy code included in the subframes constituting the navigation message does not match a predetermined reference code, the time information in the subframe determined not to match is used. Correct the time.
Therefore, the reliability that the time information in the subframe is normal through conditions such as that the predetermined code has not changed, the health condition is good, and the distance measurement accuracy is high. Can be improved. In addition, since the subframe including the time information is transmitted once every 6 seconds, not only can the time be corrected quickly and accurately, but also the power consumption can be reduced. is there.
Since each subframe includes a telemetry word and a handover word, according to the invention described in claim 2 or 7, the time can be corrected theoretically in 6 seconds.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a GPS receiver (with a time display function) according to the present embodiment.

  As shown in FIG. 1, the GPS receiver according to this embodiment is mounted on, for example, a wristwatch type GPS terminal, and includes an antenna 1, a tuner circuit unit 2, a signal processing circuit unit 4, and a CPU (Central Processing Unit). 8, clock circuit unit 9, oscillation circuit unit 10, input unit 11, display output unit 12, display unit 13, ROM (Read only memory) 14, RAM (Random Access memory) 15, and power supply circuit unit 16 The

Here, the outline of GPS will be described.
[System overview]
A part in the outer space of the entire GPS system is called a space segment, a ground part is called a control segment, and a user receiver is called a user segment. GPS satellites belong to the space segment. The GPS satellite is not a geostationary satellite, but orbits the altitude of 20,000 km and changes its position with respect to the earth. The space and control segments are developed and operated by the US military, but the user segment must be designed and manufactured by the user. Therefore, the specification of the signal transmitted from the GPS satellite is defined in detail and the document is made public. This document is named an interface control document (abbreviated as ICD). The version of this ICD has been updated, for example, GPS-ICD-200.

Currently, wireless signals are transmitted from 28 aircraft. The frequency of the radio signal transmitted by the GPS satellite is basically 1575.42 MHz (name: L1 wave), and a signal called C / A code (coarse / acquisition code) for commercial use is put on this frequency. Yes.
By this signal, data called a navigation message in the format shown in FIG. 2 is described and transmitted. The navigation message includes trajectory information, time information, and the like. The data rate of the navigation message is 50 bps.

  One cycle of the navigation message is called in units of frames, and has the structure shown in FIG. One frame is 1500 bits, and it takes 30 seconds to transmit it. The frame is composed of five subframes (each 300 bits), and transmission is started in order from subframe 1. When transmission of subframe 5 is completed, transmission returns to transmission of subframe 1 again.

[Navigation message]
FIG. 2B and FIG. 3 are simplified configuration diagrams of subframes.
Of the five subframes, subframes 1 to 3 include clock correction information and orbit information (ephemeris) of the transmitting satellite itself (see FIG. 3). For subframes 4 and 5, all satellites transmit the same contents, and the contents are rough orbit information (almanac) and ionospheric correction information of all GPS satellites (up to 32 satellites) in orbit ( However, since they have a large amount of data, they are further divided into pages and accommodated in subframes. That is, as shown in FIG. 2 (a), the data transmitted in the subframes 4 and 5 are divided into pages 1 to 25, and the contents of different pages are sent in order for each frame. It takes 25 frames to transmit all page contents, and it takes 12 minutes and 30 seconds to get all the navigation message information.

  The inside of the subframe is divided into units called words as shown in FIGS. One word is 30 bits, and one subframe corresponds to 10 words. Each word is composed of a 24-bit data portion and 6 bits for parity check. At the beginning of each subframe, a TLM (telemetry) word and then a HOW (handover) word are described. The TLM word contains a synchronization pattern, and the HOW word contains GPS signal time information.

  The time in the GPS signal is managed in units of one week. The beginning of the week is 0:00 on every Sunday (24 o'clock on Saturday), and the time is expressed by the elapsed time (TOW (time of week)). The HOW word contains a number representing this elapsed time in units of 1.5 seconds, giving the receiver a clue to know the current time. Each week is numbered, and the week starting on January 6, 1980, 00:00:00 is week number 0. From this point, the week number is incremented by 1 every week. For example, the week number of the week starting on October 10, 2004 is 1292.

  The navigation message is shared and accommodated in the five subframes. Hereinafter, some items will be described, but the details can be understood by referring to GPS-ICD-200 or the like.

  Subframe 1 of the navigation message contains a numerical value representing the state of the satellite itself that is transmitting the message and a clock correction coefficient. FIG. 4 shows a list showing the contents of subframe 1. As shown in FIG. 4, following the first TLM word and HOW word, the above-described words of week number WN (week number), ranging accuracy URA, and satellite health state SVhealth are described.

Ranging accuracy URA is a rough standard of ranging accuracy when a pseudo-range (a distance between a GPS satellite and a receiver measured by adding an error due to advance of a receiver clock) is measured by the satellite. In the case of, it means that something is wrong.
The satellite health state SVhealth is a code indicating the state of the satellite, and when it is other than 0, it indicates that there is some abnormality.

  The subframes 2 and 3 store the orbit information of each satellite (refer to GPS-ICD-200 for details). Such orbit information is called ephemeris, and the position of the GPS satellite at an arbitrary time can be calculated.

  The rough orbit information for all GPS satellites is called almanac, and is contained in pages 2-5 and 7-10 of subframe 4 and pages 1-24 of subframe 5. There are 32 GPS satellites in 32 pages in total. Corresponding to FIG. 5 shows a list showing the contents of the almanac. A TLM word and a HOW word are described at the head of the subframe.

  The ionosphere distributed at an altitude of 100 km or more has a function of delaying radio waves, and information for correcting the delay amount is contained in page 18 of subframe 4. FIG. 5 shows a list showing the contents of the page 18 of the subframe 4. Again, a TLM word and a HOW word are described at the head of the subframe.

FIG. 7 shows a configuration diagram of the TLM word and the HOW word.
As shown in FIG. 7, the first 8 bits of the TLM word are a synchronization preamble, the first 17 bits of the HOW word are the above-mentioned TOW (time of week), and the 20-22 bits are a subframe ID.

[Search for navigation messages and subframes]
The decoding of the navigation message begins with finding the head of the subframe. Although the synchronization preamble is always <10001011> and the last two bits of HOW are always <00>, it should be noted that the polarity of the word may be reversed. Therefore, subframes are searched for by correlating one bit at a time. The code to be synchronized with the preamble is <1-1-1-11-111>, which is correlated with the navigation message of ± 1. Since it is not known whether the polarity is correct, the synchronization result may be ± 8. Once there is a preamble that is synchronized, the preamble should exist even 300 bits ahead. If not, the initial synchronization is not due to the preamble.

The subframe search is performed in the following order on the program.
(1) Find the preamble from the first 360 bits.
(2) Once the preamble is found, it is confirmed whether it is synchronized even 300 bits ahead and 600 bits ahead.
(3) If not synchronized, move to other data, and if synchronized, determine that the preambles of the three subframes have been confirmed.
(4) Check whether the sum of the last 2 bits (29th bit and 30th bit) of HOW is +2 or -2. If the sum is +2, the polarity of the word is inverted, so it is corrected by multiplying by -1, and if the sum is -2, it is determined that the polarity is normal.
(5) Check the subframe ID.
Thereafter, a parity check using parity bits is performed, and the navigation message is decoded.

[Transition of receiver and measurement error]
The initial receiver with which GPS was developed had only one channel of receiving circuit, and could not receive signals from many satellites simultaneously. Accordingly, reception and ranging processing are performed while sequentially switching the satellites, and the satellites have caused measurement errors due to movement of the receivers, fluctuations in measurement conditions, and the like. Nowadays, a receiver usually has a receiving circuit of about 8 to 12 channels, and there are many 16-channel products. Most or all of the GPS satellites in the sky can be processed at the same time, and variations in measurement error due to sequential measurement are not a problem.
(End of GPS overview)

The tuner circuit unit 2 according to the present embodiment captures radio waves transmitted from GPS satellites via the antenna 1. The signal processing circuit unit 4 simultaneously decodes a plurality of GPS signals from GPS satellites, reads them as navigation messages, and outputs them to the CPU 8. CPU8 which acquired the navigation message performs the program read from ROM14, calculates each value contained in a navigation message, and preserve | saves the calculation result with RAM15 in RAM15. The timing circuit unit 9 measures time based on the frequency output from the oscillation circuit unit 10. For example, a value indicating the current time recorded in units of one second is output from the timing circuit unit 9 to the CPU 8. The CPU 8 outputs a value indicating the current time to the display unit 13 via the display output unit 14. The display unit 13 displays the time.
The input unit 11 inputs operation input information from the user and information from another computer or storage medium to the CPU. The power supply unit 16 includes a power source such as a battery, and supplies power to each unit.

In order to implement the time correction control of this embodiment, it is sufficient to read a necessary part in the navigation message described by the GPS signal from at least one GPS satellite.
As shown in FIG. 8 (a1), in the RAM 15, a synchronization preamble code storage area 15a1 for storing the synchronization preamble code at the head of the TLM word for each subframe included in the navigation message of a certain GPS satellite, A tail code storage area 15a2 for storing the last 2 bits of the HOW word and a TOW storage area 15a3 for storing TOW (time of week) in the HOW word are provided.
As shown in FIG. 8 (a2), the ROM 14 is provided with a reference code A storage area 14a1 in which the reference code A is stored and a reference code B storage area 14a2 in which the reference code B is stored. The reference code A is <10001011> and the reference code B is <00>.

  Next, time correction control according to the present embodiment will be described along a series of processing flows. FIG. 9 is a flowchart of time correction control according to the present embodiment.

The CPU 8 performs the first time correction based on the time correction control program (including the reference code A and the reference code B) read from the ROM 14.
First, the CPU 8 issues a command to the tuner circuit unit 2 and the signal processing circuit unit 4. The tuner circuit unit 2 starts receiving the GPS signal captured by the antenna 1 in accordance with this command (step S1). The signal processing circuit unit 4 decodes the received GPS signal, acquires a navigation message, and outputs the acquired navigation message to the CPU 8. The CPU 8 searches for the subframe from the navigation message, and if the subframe can be captured (YES in step S2), the captured subframe is stored in the synchronous preamble code storage area 15a1 and the last bit code storage area 15a2 of the RAM 15. The synchronization preamble code at the beginning of the TLM word of the frame and the last code at the end of the HOW word are stored (step S3). Here, the subframe to be captured may be any of the subframes 1 to 5.

  Next, the CPU 8 determines whether or not the TLM leading synchronization preamble code stored in the RAM 15 matches the reference code A <10001011> (step S4).

If it is determined in step S4 that they match (YES in step S4), it is determined whether or not the last two bits of the HOW stored in the RAM 15 match <00> of the reference code B ( Step S5).
If the CPU 8 determines that they do not match in step S4 (NO in step S4), the process returns to step S2.

If it is determined in step S5 that they match (YES in step S5), the CPU 8 corrects the time of the time measuring circuit unit 9 using the TOW (time information) stored in the RAM 15, and the time measuring circuit unit 9 measures the time. The time is displayed as the current time on the display unit 13 (step S6).
If the CPU 8 determines that they do not match in step S5 (NO in step S5), the process returns to step S2.

Next, the CPU 8 ends the reception of the GPS signal (step S7), and instructs the time counter of the time measuring circuit section 9 to start time counting (step S8). If the CPU 8 determines that a predetermined time (for example, 24 hours) has elapsed (YES in step S9), the CPU 8 returns to step S1 and executes time correction control again (steps S1 to S6).
As described above, immediately after the time of the time measuring circuit unit 9 is corrected, the reception of the GPS signal is immediately terminated, and from this point in time until a predetermined time (for example, 24 hours) elapses, the power source unit 16 receives the tuner. Since power supply to the circuit unit 2 and the signal processing circuit unit 4 is stopped, power consumption can be reduced accordingly.

When the synchronization preamble code at the beginning of the TLM and the last two bits of the handover word HOW do not match the reference codes A and B, there is a relatively high possibility that the TOW between them is not correctly read.
However, according to the first embodiment described above, the synchronization preamble code at the beginning of the TLM and the last two bits of the handover word HOW coincide with the reference codes A and B, respectively. Since the time adjustment control is performed using the TOW, highly accurate time adjustment can be performed, and since one subframe can be received in 6 seconds, the time can be adjusted in about 6 seconds.
Regardless of the above embodiment, only one of the coincidence determination between the synchronization preamble code and the reference code A and the coincidence determination between the last 2 bits of the handover word HOW and the reference code B is performed. It is also possible to carry out the matching determination.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 8 (b1) shows the stored contents of the RAM according to this embodiment. FIG. 8 (b2) shows reference codes C and D stored in the ROM according to the present embodiment. The present embodiment is different from the first embodiment in that the determination is made using the satellite health condition code and the ranging accuracy code. The configuration of the GPS receiver is the same as that shown in FIG.

As shown in FIG. 8 (b1), the RAM 15 stores a satellite health state storage area 15a4 for storing a satellite health state SVhealth and a ranging accuracy URA for each subframe 1 included in a navigation message of a certain GPS satellite. A distance measuring accuracy storage area 15a5 and a TOW (time of week) TOW storage area 15a6 in the HOW word are provided.
As shown in FIG. 8 (b2), the ROM 14 is provided with a reference code C storage area 14a4 in which the reference code C is stored and a reference code D storage area 14a5 in which the reference code D is stored. The reference code C is <0> and the reference code D is <15>.

  Next, time correction control according to the present embodiment will be described along a series of processing flows. FIG. 10 is a flowchart of time correction control according to the present embodiment.

The CPU 8 performs the first time correction based on the time correction control program (including the reference code C and the reference code D) read from the ROM 14.
First, as in the case of the embodiment shown in FIG. 9, the CPU 8 issues a command to the tuner circuit unit 2 and the signal processing circuit unit 4. The tuner circuit unit 2 starts receiving a GPS signal (step S1). The signal processing circuit unit 4 decodes the received GPS signal, acquires a navigation message, and outputs it to the CPU 8. The CPU 8 searches for the subframe from the navigation message, and if the subframe 1 can be captured (YES in step T1), the satellite health state storage area 15a4, the ranging accuracy storage area 15a5, and the TOW storage area of the RAM 15 In 15a6, the satellite health state SVhealth, ranging accuracy URA, and TOW of the captured subframe 1 are stored (step T2).

  Next, the CPU 8 determines whether or not the code of the satellite health state SVhealth stored in the RAM 15 matches the reference code C <0> (step T3).

If it is determined in step T3 that they match (YES in step T3), it is determined whether or not the code of the distance measurement accuracy URA stored in the RAM 15 matches <15> of the reference code D (step T4). .
If the CPU 8 determines that they do not match at step T3 (NO at step T3), the process returns to step T1.

If it is determined in step T4 that they do not match (NO in step T4), the CPU 8 corrects the time of the time measuring circuit unit 9 using the TOW (time information) stored in the RAM 15, and the time measuring circuit unit 9 measures the time. The time is displayed as the current time on the display unit 13 (step S6).
If the CPU 8 determines that they match in step T4 (YES in step T4), the process returns to step T1.

Next, the CPU 8 ends the reception of the GPS signal (step S7) and instructs the counter of the time measuring circuit unit 9 to start the time count (step S8). When the CPU 8 determines that a predetermined time (for example, 24 hours) has elapsed (YES in step S9), the CPU 8 returns to step S1 and executes time correction control again (steps S1 to S6).
As described above, immediately after the time of the time measuring circuit unit 9 is corrected, the reception of the GPS signal is immediately terminated, and from this point in time until a predetermined time (for example, 24 hours) elapses, the power source unit 16 receives the tuner. Since power supply to the circuit unit 2 and the signal processing circuit unit 4 is stopped, power consumption can be reduced accordingly.

The satellite health state SVhealth is a code indicating the state of the satellite, and when it is other than 0, it indicates that there is some abnormality. The distance measurement accuracy URA is a measure of the distance measurement accuracy when the pseudo-range is measured by the satellite, and in the case of 15, it means that there is some abnormality.
However, according to the second embodiment described above, it is necessary that the code of the satellite health state SVhealth matches the reference code C, and that the code of the ranging accuracy URA does not match the reference code D. As described above, since the time correction control is performed using the TOW included in the subframe, the time can be adjusted with high accuracy.

Regardless of the above embodiment, only one of the determination using the satellite health state SVhealth and the determination using the ranging accuracy URA may be performed.
In the former case, if it is determined in step T3 that they match (YES in step T3), step T4 is omitted and the process proceeds to step S6. In step T2, at least satellite health state SVhealth and TOW of subframe 1 are stored in RAM 15.
In the latter case, at least the ranging accuracy URA and TOW of the sub-frame 1 are stored in the RAM 15 in step T2, and the processing contents are transferred to step T4 with step T3 omitted.

  In the second embodiment described above, subframe 1 is captured. However, since satellite health state SVhealth is also included in the almanac, sub-frame 1 and subframe 1 can be used for determination using satellite health state SVhealth. The pages 2 to 5 and 7 to 10 of the frame 4 and the pages 1 to 24 of the subframe 5 can be captured.

  In the above embodiment, the timing circuit unit 9 and the display unit 13 are provided, but this is not provided, and the timing circuit unit and the display unit are provided in any hardware such as an external display device or a computer. The present invention may be implemented as a GPS receiver that corrects the current time of the external timing circuit unit and displays and outputs the corrected current time on the display unit.

It is a block diagram of the GPS receiver which concerns on 1st and 2nd embodiment of this invention. It is a schematic block diagram which shows the data structure of a navigation message. It is a schematic block diagram of each sub-frame contained in a navigation message. It is a list which shows the content of the sub-frame 1 contained in a navigation message. It is a table | surface which shows the content of the almanac contained in a navigation message. It is a list which shows the content of the page 18 of the sub-frame 4 contained in a navigation message. It is a block diagram of the TLM word and HOW word contained in each sub-frame. (a1) is a diagram showing contents stored in the RAM according to the first embodiment of the present invention, (a2) is a diagram showing contents stored in the ROM, and (b1) is a second embodiment of the present invention. The figure which shows the content memorize | stored in RAM which concerns, (b2) is a figure which shows the content memorize | stored in ROM. It is a flowchart of the time correction control which concerns on 1st Embodiment of this invention. It is a flowchart of time correction control concerning a 2nd embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuner circuit part 4 Signal processing circuit part 7 Memory 8 CPU (discriminating means, time correction control means)
9 Clocking circuit unit 10 Oscillating circuit unit 11 Input unit 12 Display output unit 13 Display unit

Claims (14)

Receiving means for receiving GPS signals;
A discriminating means for discriminating whether or not a predetermined code included in a subframe constituting the navigation message by the GPS signal received by the receiving means matches a predetermined reference code;
Time correction control means for correcting the time using the time information in the subframe determined to match by the determination means;
A time correction control device comprising: Receiving means for receiving GPS signals;
The reference preamble code in which the synchronization preamble code at the beginning of the telemetry word and the code of the last 2 bits of the handover word included in the subframe constituting the navigation message by the GPS signal received by the receiving means are respectively determined in advance. A discriminating means for discriminating whether or not they match,
Time correction control means for correcting the time using the time information in the handover word determined to match by the determination means;
A time correction control device comprising: Receiving means for receiving GPS signals;
A discriminating means for discriminating whether or not the code of the satellite health state included in the subframe constituting the navigation message by the GPS signal received by the receiving means matches a predetermined reference code;
Time correction control means for correcting the time using the time information in the subframe determined to match by the determination means;
A time correction control device comprising: Receiving means for receiving GPS signals;
Discrimination means for discriminating whether the code of ranging accuracy included in the subframe constituting the navigation message by the GPS signal received by the receiving means matches a predetermined reference code;
Time correction control means for correcting the time using the time information in the subframe determined to be inconsistent by the determination means;
A time correction control device comprising:   When the time is corrected by the control of the time correction control means, further comprising a reception operation prohibition control means for prohibiting the reception operation of the GPS signal by the reception means until a predetermined time elapses. The time correction control device according to any one of claims 1 to 4, wherein A receiving step for receiving a GPS signal;
A determination step of determining whether a predetermined code included in a subframe constituting the navigation message by the GPS signal received by the reception step matches a predetermined reference code;
A time correction control step of correcting the time using the time information in the subframe determined to match by the determination step;
A time correction control method comprising: A receiving step for receiving a GPS signal;
A reference preamble code in which the synchronization preamble code at the beginning of the telemetry word and the code of the last 2 bits of the handover word included in the subframe constituting the navigation message by the GPS signal received by this reception step are respectively determined in advance. A determining step for determining whether they match, and
A time correction control step of correcting the time using the time information in the handover word determined to match by the determination step;
A time correction control method comprising: A receiving step for receiving a GPS signal;
A determination step of determining whether the code of the satellite health state included in the subframe constituting the navigation message by the GPS signal received by the reception step matches a predetermined reference code;
A time correction control step of correcting the time using the time information in the subframe determined to match by the determination step;
A time correction control method comprising: A receiving step for receiving a GPS signal;
A determination step of determining whether a code of ranging accuracy included in a subframe constituting the navigation message by the GPS signal received by the reception step matches a predetermined reference code;
A time correction control step of correcting the time using the time information in the subframe determined to be inconsistent by the determination step;
A time correction control method comprising:   When the time is corrected by the control of the time correction control step, a reception operation prohibition control step for prohibiting the reception operation of the GPS signal by the reception step until a predetermined time elapses is further provided. The time correction control method according to any one of claims 6 to 9, wherein the time correction control method is provided. Receiving means for receiving GPS signals;
Determining means for determining whether or not the time information is normal with reference to other predetermined information other than the time information in the subframe constituting the navigation message by the GPS signal received by the receiving means;
If it is determined by the determination means that the time information is normal, time correction control means for correcting the time using the time information in the subframe;
A time correction control device comprising: The time correction control device according to claim 11,
The other predetermined information is at least one information of a synchronization preamble code at the beginning of the telemetry word, a 2-bit code at the end of the handover word, a satellite health condition code, and a ranging accuracy code. There is a time correction control device. A receiving step for receiving a GPS signal;
A determination step of determining whether the time information is normal with reference to other predetermined information other than the time information in the subframe constituting the navigation message by the GPS signal received by the reception step;
If it is determined that the time information is normal by this determination step, a time correction control step of correcting the time using the time information in the subframe;
A time correction control method comprising: The time correction control method according to claim 13,
The other predetermined information is at least one information of a synchronization preamble code at the beginning of the telemetry word, a 2-bit code at the end of the handover word, a satellite health condition code, and a ranging accuracy code. A time correction control method characterized by:

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