JP3512068B2 - Time synchronization method and GPS receiver in positioning system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
(Global Positioning System
In m), the present invention relates to a time synchronization method suitable for application when time synchronization of radio waves from GPS satellites and a GPS receiving apparatus applying the method are applied.

[0002]

2. Description of the Related Art In a GPS system for measuring the position of a moving body using a plurality of artificial satellites, a spread spectrum modulation system is used as a modulation system for signal radio waves from the satellites. For example, in the case of a consumer GPS receiver, positioning calculation is performed by receiving a spread spectrum signal radio wave called a C / A code (Corse Acquisition code) from a GPS satellite (Navstar).

The code of the PN sequence of the C / A code is different for each satellite, but which satellite uses which PN sequence code can be detected in advance by the GPS receiver. . In addition, the navigation message as described later allows the GPS receiver to know from which satellite the signal can be received at that point and at that time. Therefore, for example, in the case of three-dimensional positioning, the GPS receiver receives radio waves from four or more satellites that can be acquired at that point and at that time, performs spectrum despreading, performs positioning calculation, and calculates the position of the user's own position. To ask for.

The C / A code has a transmission signal speed of 1.02.
3MHz PN (Pseudorandom Noise)
e; pseudo random noise) sequence code, for example, a Gold code, and this PN sequence code is shown in FIG.
As shown in 0 (A), 1023 chips are repeated for one cycle (hence, 1 cycle = 1 millisecond).

Then, as shown in FIG. 10B, 1 bit of the satellite signal data is transmitted for 20 cycles of the code of the PN sequence, that is, in units of 20 milliseconds. That is, the data transmission rate is 50 bps. The 1023 chips for one period of the code of the PN sequence are inverted when the bit is "1" and when it is "0".

As shown in FIG. 10C, in GPS,
One word is formed by 30 bits (600 milliseconds).
Then, as shown in FIG. 10 (D), in 10 words, 1
A subframe (6 seconds) is formed. As shown in FIG. 10 (E), a preamble that always has a prescribed bit pattern is inserted in the first word of one subframe even when the data is updated, and the data is transmitted after this preamble. Is coming.

Further, one frame (30 seconds) is formed by 5 subframes. And the navigation message is
The data is transmitted in data units of this one frame. This one
The first three subframes of the frame data are satellite-specific information called ephemeris information. This information includes parameters for determining the orbit of the satellite and the time when the signal is transmitted from the satellite.

That is, TOW (Time O) is set in the second word of the three subframes of the ephemeris information.
It contains information from the beginning of the week called f Week). Therefore, the TOW of each subframe is 6
The information is updated every second.

All GPS satellites have atomic clocks,
The common time information is used, and the signal transmission time from the satellite is set to 1 second of the atomic clock. The PN code of the satellite is supposed to be synchronized with the atomic clock.

The orbit information of the ephemeris information is updated every several hours, but it is the same information until the update. However, the orbital information of the ephemeris information is
By storing this in the memory of the GPS receiver, the same information can be used accurately for several hours. In addition, the transmission time of the signal from the satellite is
Updated every 1 second.

The navigation messages of the remaining two subframes of the data of one frame are common information transmitted from all satellites called almanac information. This almanac information requires 25 frames to acquire all the information, and includes approximate position information of each satellite and information indicating which satellite is available. This almanac information is updated every few months, but remains the same until the update. However, by keeping this almanac information in the memory of the GPS receiver, the same information can be used accurately for several months.

Upon receiving the GPS satellite signal,
First, by using the same PN sequence code as the C / A code used in the GPS satellite to be received prepared for the receiver, the C / A code is phase-synchronized with the signal from the GPS satellite. , Spectrum despread. When the phase is synchronized with the C / A code and despreading is performed, the bits are detected and the navigation message can be acquired from the GPS satellite signal.

By the way, in order to perform positioning calculation by the GPS receiver, it is necessary to obtain the distance between the satellite and the receiver.
That is, the GPS receiver measures the time (a signal arrival time) until a signal transmitted from a satellite at a certain time reaches the GPS receiver, and measures the speed of light (3 × 10
⁸ m / s) to calculate the distance.

In order to measure the signal arrival time, it is necessary to measure two types of time by finely synchronizing the signals from the satellites. One is C / A
1 of spreading code obtained by phase synchronization with code
The time information is equal to or less than the cycle, that is, 1 millisecond or less. The other is time information of one cycle or more of the spread code, that is, one millisecond or more.

The time information of 1 millisecond or less is obtained as the timing at which the GPS satellite signal is captured by synchronizing the phase of the C / A code. That is, the satellite spread code (PN
Code) is synchronized with the atomic clock, so if the GPS receiver is phase-synchronized with the PN code, that is, the C / A code is synchronized, the arrival time of the radio wave from the satellite is 1 millisecond or less. Information will be obtained.

However, only by synchronizing the C / A code, time information of 1 millisecond or less can be obtained, and time information of 1 millisecond or more cannot be obtained. Therefore, time information of 1 millisecond or more is required. Conventionally, the time information of 1 millisecond or more is obtained by acquiring the navigation message included in the signal from the GPS satellite. That is, the time information of 1 millisecond or more is obtained by performing phase synchronization with the preamble pattern in the navigation message and confirming the phase synchronization timing by referring to TOW.

[0017]

The problem of the above-mentioned conventional method of time synchronization is that the preamble and TOW information for obtaining time information of 1 millisecond or more are subframe units, that is, once every 6 seconds. The only thing you can get is. Moreover, in order to prevent accidental lock, information such as preamble is
Normally, it is desirable to check the data twice or more. Therefore, the time required from the state in which the signal from the satellite is synchronized with the C / A code to the final time synchronization is G
Even if the clock information of the PS receiver is valid, it takes 6 seconds or more.

For this reason, when trying to reduce the time required from power-on to the start of positioning calculation, this portion becomes a bottleneck. Further, when it is assumed that the GPS positioning system is mounted on a portable device or the like, power saving becomes a problem, but as described above, in the conventional technique, it takes time to start positioning calculation, and thus power saving is required. It was not enough.

In view of the above points, it is an object of the present invention to provide a time synchronization method capable of shortening the time required from the power-on of a GPS receiver to the time synchronization.

[0020]

In order to solve the above-mentioned problems, a time synchronization method according to the invention of claim 1 detects the synchronization timing of a spread code of a spread spectrum signal from a GPS satellite to detect the time synchronization. For detecting a time component of one cycle or less of the spreading code for the purpose of: and after the synchronization of the spreading code is completed in the first step, the time information of the boundary of one cycle of the spreading code is set to G.
Second detection by the time information available to the PS receiver
And the time information at the boundary of one cycle of the spread code detected in the second step, the known orbit information of the GPS satellite, and the approximate position of the GPS receiver. GPS of radio waves from
A third step of detecting a time component of one or more cycles of the spreading code for the time synchronization based on the time information obtained by the difference with the arrival time to reception.

According to the first aspect of the invention, the time component of 1 msec or less, which is one period of the spread code, is obtained by synchronizing the C / A code as in the conventional case, but 1 msec. For the above time components, 1 of the spreading code
The time at the boundary of the cycle is detected from the time information that the GPS receiver can obtain. In this case, the time information that can be obtained by the GPS receiver can be time-synchronized with sufficient accuracy if it has an accuracy of 500 microseconds or less, and 3-4 satellites can be processed in the same manner as described above. The positioning calculation can be started by synchronizing the time.

Therefore, according to the invention of claim 1, it is not necessary to check the preamble and TOW of the navigation message as in the conventional GPS positioning system, so that the time required for time synchronization can be greatly shortened. .

Further, the time synchronization method according to the invention of claim 3 detects the synchronization timing of the spread code of the spread spectrum signal from the GPS satellite to detect the time of one cycle or less of the spread code for time synchronization. The first step of detecting a component and, after the synchronization of the spread code is completed in the first step, the time information of the bit boundary of the spread spectrum demodulated data is detected by the time information available to the GPS receiver. Second step, time information of the boundary between the bits detected in the second step, known orbit information of the GPS satellite, and the GPS
A third step of detecting a time component of one or more cycles of the spread code based on time information obtained by a difference between an approximate position of the receiver and an arrival time of the radio wave from the GPS satellite to the GPS reception. And are provided.

According to the invention of claim 3 , the time component of 1 millisecond or less is obtained by synchronizing the C / A code as in the conventional case, but the time component of 1 millisecond or more is obtained. The time at the bit boundary, which is 20 cycles of the spread code, is detected from the time information that can be obtained by the GPS receiver. In this case, the time information obtained by the GPS receiver can be time-synchronized with sufficient accuracy if the accuracy is 10 milliseconds or less, and the time information can be 3-4.
By positioning the satellites in the same manner as described above, the positioning calculation can be started.

Therefore, according to the invention of claim 3 , it is not necessary to check the preamble and TOW of the navigation message as in the conventional GPS positioning system, and therefore the time required for time synchronization can be greatly reduced. At the same time, the accuracy of the time information required by the GPS receiver may be lower than that of the first aspect.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a time synchronizing method in a positioning system according to the present invention and a GPS receiving apparatus using the same will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a system configuration of an embodiment of a GPS receiving apparatus of the present invention.

In FIG. 1, the antenna unit 1 is a GP.
The S satellite signal or the like is received, and the received signal is supplied to the high frequency signal processing unit (abbreviated as RF unit) 2. The RF unit 2 frequency-converts the received signal into an intermediate frequency signal of several MHz to several tens of MHz, and outputs the intermediate frequency signal to the demodulation / calculation unit 3. The demodulation / arithmetic unit 3 synchronizes the C / A code,
The demodulation (spectrum despreading) process is performed, time synchronization is performed, and positioning calculation is executed.

The clock unit 4 holds / updates clock information for the positioning calculation in the demodulation / calculation unit 3. A highly accurate timepiece unit 4 is used in this embodiment. If the accuracy is not sufficient, the communication unit 7 described later acquires accurate clock information from the outside through the antenna 8,
Thereby, the time accuracy of the clock unit 4 may be regularly calibrated.

A radio timepiece may be used instead of the timepiece unit 4. That is, a receiving unit for receiving the information of the radio clock may be provided, and the information of the received time may be used instead of the time information of the clock unit 4.

The demodulation / arithmetic unit 3 also stores in the storage unit 5 ephemeris information and almanac information obtained by demodulating the received signal. In addition, the receiver of this embodiment uses the GPS information for ephemeris information and almanac information.
It can be acquired from outside the satellite, and an antenna 8 and a communication unit 7 are provided for that purpose. The input / output unit 6 is for outputting the result or the like obtained by the positioning calculation or for fetching necessary information.

In the demodulation / arithmetic unit 3, the time component of 1 millisecond or less of the time synchronization is obtained by synchronizing the C / A code of the spread spectrum signal radio wave from the satellite in the same manner as in the conventional case. . However, for example, when the power is turned on or when the time synchronization is resynchronized from a state where the time synchronization is largely deviated, the time information of the specific data is accurately calculated for the time component of 1 millisecond or more. The time information of the clock unit 4 is used for acquisition, and the preamble and TOW of the navigation message are not used as in the conventional case. The outline of this time synchronization method will be described below.

Radio waves from the satellite are transmitted according to the GPS clock (atomic clock), for example, as shown in FIG. As shown in FIG. 2B, this transmitted radio wave is received by the GPS receiver after the arrival time Δta.

In FIGS. 2A and 2B, the arrival time Δta is shown on the basis of the time point of the beginning of the subframe. However, even if the time point of the beginning of the subframe is unknown, the boundary of specific data, For example, if the time at the boundary of one cycle, the boundary of bits, the boundary of words, etc. of the spread code is accurately known, and the time of that boundary is the epoch of what word, what bit, and epoch of the subframe, This is equivalent to detecting the time point at the beginning of the subframe.

Therefore, in this embodiment, the time of the boundary of specific data, for example, the boundary of one cycle of the spreading code, the boundary of the bit, the boundary of the word, etc. is accurately detected from the clock unit 4, and the time of the boundary is detected. By recognizing what epoch of which bit of which word of the subframe is
Even if the preamble or TOW in the navigation message is not checked, the time component of 1 millisecond or more is known and the time is synchronized.

The number of words, bits and epochs of the subframe at the boundary can be obtained as follows.

From the orbital data of the satellite stored in the storage unit of the GPS receiver and the approximate position of the GPS receiver, the approximate arrival time Δta of the radio wave from the satellite can be known. Therefore, when this arrival time ta is subtracted from the reception time (clock section 4) of the radio wave in the GPS receiver, it becomes approximately equal to the time point at the beginning of the subframe of the information from the satellite.

Therefore, the arrival time Δ from the time at the boundary point
When ta is subtracted, the time of the subtraction result is as shown in FIG.
As shown in, the information is the time when Δtb has elapsed from the beginning of the subframe. By calculating the time of this subtraction result by replacing it with a clock of a bit or a spread code, it is possible to know what word, bit, and epoch of the subframe is the word.

Therefore, if the clock information of the GPS receiver holds the accuracy of a predetermined accuracy with respect to the GPS clock at the boundary time, after the C / A code synchronization is completed,
By obtaining the time at the boundary of specific data from the clock information, time synchronization can be achieved without checking the preamble or TOW in the navigation message.

By the way, the boundary of one cycle of the spread code can be easily detected. Further, the bit boundary can be detected by detecting the inversion of the spread code for each cycle. However, it is difficult to detect word boundaries because the content of each word is different. The same applies to the boundary between subframes. Therefore, in the embodiment described below,
The boundary of one cycle of the spread code and the boundary of bits are used.

As described above, when the C / A code from the satellite is synchronized, the C / A code has a period of 1 millisecond, so that the time component of 1 millisecond or less The arrival time of radio waves from the satellite will be known. In other words, when synchronization is achieved, the amount of deviation (how many chips is deviated) of the spread code (PN code) from the reference phase at the time of synchronization is 1 mm of the arrival time of radio waves from the satellite to the receiver. It is a time component of the order of seconds or less. This is no different from the conventional method.

In the time synchronization method of this embodiment, as described above, the GPS receiver incorporates a highly accurate clock section, or the GPS receiver provides more accurate time information such as a radio clock. , To be able to obtain from outside.

In the above description, in order to detect the boundary of one cycle of the spread code, it is necessary to accurately detect the boundary with an error of the order of 500 μsec. Further, in order to detect the bit boundary, it is sufficient that the boundary can be accurately detected with an error of the order of 10 milliseconds. There are two embodiments, as described below, depending on the difference in accuracy of the time information that can be used by this GPS receiver.

The problem of accuracy of time information will be described.

Now, the difference between the time data available to the GPS receiver and the correct time data is Δt1. Also, FIG.
As shown in, the approximate position of the GPS receiver is (ux1, uy
1, uz1), the exact position of the GPS receiver (ux, uy, u
z), the position of the satellite at time t is (stx, sty, stz
), When the position of the satellite when the radio wave received by the receiver is transmitted at time t is (sx, sy, sz) and the speed of light is c, the calculated radio wave from the satellite to the GPS receiver From FIG. 3, the error Δt2 of the propagation time is Δt2 = | ((sx−ux) ² + (sy−uy) ² + (sz−uz)
² ) ^1/2 − ((stx −ux1) ² + (sty −uy1) ² + (s
tz −uz1) ² ) ^1/2 | / c.

The error E which is a problem as the time information is E =
Since Δt1 + Δt2, how to obtain the time component of 1 millisecond or more differs depending on the value of the error E of the time information that can be used by the GPS receiver.

[First Embodiment] In the first embodiment, time information of 1 millisecond or more for time synchronization is a PN code which is a spreading code, that is, a C / A code of 1. It is obtained from the time information at the boundary of the cycle of 1023 chips. In this case, the accuracy of the time information that can be used by the GPS receiver needs to be E = Δt1 + Δt2 <500 μsec. Here, the clock unit 4 is assumed to satisfy this condition.

FIG. 4 is a block diagram for time synchronization of the demodulation / calculation unit 3 of FIG. 1 in the case of the first embodiment. In this, some or all of the blocks can be configured by a microcomputer.

That is, the intermediate frequency signal from the RF unit 2 is supplied to the despreading unit 31. In the despreading unit 31, P
A PN code for despreading is supplied from a C / A code synchronization detection unit 33 including an N code generator. And C / A
The code synchronization detection unit 33 controls the generation phase of the PN code based on the correlation detection information from the despreading unit 31, and the C / A
Sync detection with code is performed. Then, the phase of the PN code is locked to the synchronized phase.

When the C / A code synchronization is completed, the despreading unit 31 demodulates and obtains the GPS satellite signal that has been spread spectrum modulated, and this is obtained.
2 is supplied.

The data decoding unit 32 decodes and outputs the ephemeris information and the almanac information. Information on these navigation messages is stored in, for example, the storage unit 5 and is also supplied to the positioning calculation unit 35.

Further, the C / A code synchronization detection unit 33 uses the C
A signal Lt indicating the timing at which the / A code is synchronized is supplied to the time synchronization detector 34. Further, in this embodiment, the C / A code synchronization detection unit 33 supplies the signal Ps indicating the boundary of one cycle of the PN code to the time synchronization detection unit 34.

The time synchronization detector 34 obtains time information of 1 millisecond or less for time synchronization from the signal Lt indicating the timing at which the C / A codes are synchronized. The time synchronization detection unit 34 also obtains time information of 1 millisecond or more for time synchronization based on the signal Ps indicating the boundary of one cycle of the PN code after the completion of the C / A code synchronization, and performs the positioning calculation. Time synchronization for.

FIG. 5 is a flow chart showing the flow of processing performed by the time synchronization detecting section 34.

That is, first, the time synchronization detector 34 determines whether or not the synchronization of the C / A code is completed, based on whether or not the signal Lt is obtained (step S10).
1). When it is determined that the C / A code synchronization is completed, a time component of 1 millisecond or less for time synchronization is obtained (step S102).

Next, one cycle of the PN code is completed, and PN
Wait for the boundary of the code cycle (step S10
3), the fact that the boundary of the cycle of the PN code is reached
After confirming with the signal Ps indicating the boundary of one cycle of the code,
The time ts at that time is detected from the time information of the clock unit 4 (step S104).

Then, as described above, the radio wave propagation time, which is the approximate arrival time of the radio wave from the satellite, is subtracted from the time ts at that time, and the result of the subtraction is rounded to the digit of 100 μs. , Obtaining time information of 1 millisecond or more for time synchronization. Then, time synchronization is obtained from the time information, and the result is sent to the positioning calculation unit 35 (step S105).

[0058] In this case, the radio wave propagation time, which is a radio wave arrival time from the satellite, the following ^{formula, ((stx -ux1) 2 +} (sty -uy1) 2 + (stz -uz1
) ² ) ^1/2 / c.

With the above, the time synchronization processing in the time synchronization detector 34 is completed.

The positioning calculator 35 calculates the distance between the satellite and the GPS receiver based on the above-mentioned time synchronization information. That is, the number required for the positioning calculation (usually three when performing two-dimensional positioning, four when performing three-dimensional positioning)
When the above-mentioned time synchronization is taken for the satellites and the distances between the respective satellites and the GPS receiver are calculated, the positioning calculation is executed and the result is output.

As described above, in this embodiment,
When the synchronization of the C / A code is completed and thereafter the boundary of one cycle of the PN code is detected, the time synchronization as the preprocessing of the positioning calculation can be achieved and the positioning calculation can be performed. Compared to a method using a preamble or TOW that can be obtained only in units of seconds , the time required to obtain the position can be shortened, which contributes to power saving.

For example, when the GPS receiver is driven intermittently as shown in FIG. 6, the conventional receiver takes a long time to obtain the position, and power consumption becomes a problem. In the case of the present invention, the time until the position is obtained is shortened as described above, and it is possible to reduce the power consumption of the hatched portion in the conventional power consumption in FIG.

Further, the power consumption of the GPS receiver can be reduced in this way, and the waiting time is reduced and the user's stress is reduced by shortening the time for the user to know the position. can do.

Further, since the battery capacity required for driving the GPS receiver can be reduced by the power saving, it is possible, for example, to apply to a micro-positioning / precision time measuring device such as a wrist watch type as shown in FIG. It can be applied.

[Second Embodiment] In the second embodiment, time information of 1 millisecond or more for time synchronization is obtained from time information at a boundary between bits of spread spectrum demodulated data. . In the second embodiment, the accuracy of the time information that can be used by the GPS receiver needs to be E = Δt1 + Δt2 <10 milliseconds. In this example, it is assumed that the clock unit 4 satisfies this condition.

FIG. 8 is a block diagram for time synchronization of the demodulation / calculation unit 3 of FIG. 1 in the case of the second embodiment. Similar to the first embodiment, this is one in which some or all of the blocks can be configured by a microcomputer. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, a bit boundary detecting section 36 is provided. The bit boundary detection unit 36 is supplied with the data subjected to spread spectrum demodulation from the despreading unit 31 and the information Ps indicating the boundary of the cycle of the PN code from the C / A code synchronization detection unit 33.

In the bit boundary detecting section 36, as shown in FIG. 10, the bits correspond to 20 periods of the PN code,
By utilizing the fact that the phase of the C / A code is inverted between when the bit is “0” and when it is “1”, the bit boundary is detected and the timing of the detected bit boundary is determined. The signal Bs shown is supplied to the time synchronization detection unit 37.

As in the case of the first embodiment, the C / A code synchronization detection unit 33 supplies the time synchronization detection unit 37 with a signal Lt indicating the timing at which the C / A code is synchronized. To be done.

The time synchronization detecting section 37 obtains time information of 1 millisecond or less for time synchronization from the signal Lt indicating the timing when the C / A code is synchronized. The time synchronization detection unit 37 also obtains time information of 1 millisecond or more for time synchronization based on the signal Bs indicating a bit boundary after the completion of C / A code synchronization, and the time synchronization for positioning calculation is performed. I take the.

FIG. 9 is a flow chart showing the flow of processing performed by the time synchronization detecting section 37.

That is, first, the time synchronization detector 37 determines whether or not the synchronization of the C / A code is completed, based on whether or not the signal Lt is obtained (step S20).
1). When it is determined that the C / A code synchronization is completed, a time component of 1 millisecond or less for time synchronization is obtained (step S202).

Next, the process waits until the bit boundary is detected (step S203).
When confirmed by the signal Bs indicating the boundary between the bits, the time ts at that time is detected from the time information of the clock unit 4 (step S204).

Then, as described above, the radio wave propagation time, which is the approximate arrival time of the radio wave from the satellite, is subtracted from the time ts at that time, and the time of the subtraction result is Δt1.
A time that is a multiple of 20 milliseconds is created by adding or subtracting a time error smaller than + Δt2. As a result, time information of 1 millisecond or more for time synchronization is obtained. Then, time synchronization is obtained from the time information, and the result is sent to the positioning calculation unit 35 (step S20).
5). This is the end of the time synchronization processing in the time synchronization detection unit 37.

The positioning calculator 35 calculates the distance between the satellite and the GPS receiver based on the above-mentioned time synchronization information. Then, when the distances to the GPS receivers are calculated for the respective number of satellites required for the positioning calculation (usually three when performing two-dimensional positioning and four when performing three-dimensional positioning), Perform positioning calculation and output the result.

As described above, in this embodiment,
When the synchronization of the C / A code is completed and then the bit boundary is detected, the time synchronization as the preprocessing of the positioning calculation can be achieved and the positioning calculation can be performed. Like the embodiment, in comparison with the method of using the Never preamble and TOW obtained only by the conventional 6 seconds,
The time required to obtain the position can be shortened, which contributes to power saving.

[0077] In the case of the second embodiment, the time accuracy of the clock unit of the GPS receiver is required, as compared with the case of the first embodiment, than may be lower, watches It is possible to use a cheap and simple structure for the part,
The application to the wristwatch type device of FIG. 7 described above becomes easier.

In the two embodiments described above, the positioning calculation unit 35 detects the preamble of the navigation message and the TOW in the same manner as in the conventional case while the synchronization is stable, and the time synchronization is performed. The time information of 1 millisecond or more is acquired, and the time calculation is performed using the time information to perform the positioning calculation.

However, for time information of 1 millisecond or more for time synchronization, the preamble and TOW are not used.
Of course, it may be obtained always based on the time at the boundary of one cycle of the PN code or the time at the boundary of bits.

[0080]

As described above, according to the present invention, the time until the time synchronization as the preprocessing for positioning calculation can be achieved can be greatly shortened. That is, according to the present invention, the time required until the start of positioning calculation can be significantly reduced.

As described above, by shortening the time until the position measurement after the power is turned on, the driving time of the GPS receiver required for the position measurement is reduced, which contributes to the power saving. Further, since the time until the position measurement is shortened after the power is turned on, the stress on the user who uses the position measurement function can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of an embodiment of a GPS receiving device according to the present invention.

FIG. 2 is a diagram for explaining an embodiment of a time synchronization method according to the present invention.

FIG. 3 is a diagram used for explaining an embodiment of a time synchronization method according to the present invention.

FIG. 4 is a block diagram of an essential part of the first embodiment of the time synchronization method according to the present invention.

FIG. 5 is a flowchart for explaining the first embodiment of the time synchronization method according to the present invention.

FIG. 6 is a diagram showing the power saving performance of the GPS receiver according to the present invention in comparison with the conventional one.

FIG. 7 is a diagram showing an application example of the GPS receiver according to the present invention.

FIG. 8 is a block diagram of an essential part of a second embodiment of a time synchronization method according to the present invention.

FIG. 9 is a flowchart for explaining a second embodiment of the time synchronization method according to the present invention.

FIG. 10 is a diagram for explaining the structure of a GPS satellite signal.

[Explanation of symbols]

1 ... GPS antenna, 2 ... High frequency signal processing unit, 3 ... Demodulation / arithmetic unit, 4 ... Clock unit, 5 ... Storage unit, 6 ... Input / output unit, 7
... communication section, 8 ... communication antenna, 31 ... despreading section, 32 ...
Data decoding unit, 33 ... C / A code synchronization detecting unit, 3
4, 37 ... Time synchronization detection unit, 35 ... Positioning calculation unit, 36 ...
Bit boundary detector

Continuation of the front page (56) Reference JP 10-170626 (JP, A) JP 7-280912 (JP, A) JP 11-125666 (JP, A) JP 5-150031 (JP , A) JP-A-9-119973 (JP, A) JP-A-10-48316 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S 5 / 00-5 / 14

Claims (8)

(57) [Claims] 1. A first step of detecting a time component of one cycle or less of the spread code for time synchronization by detecting a synchronization timing of a spread code of a spread spectrum signal from a GPS satellite. After the synchronization of the spreading code is completed in one step,
A second step of detecting the time information of the boundary of one cycle of the spread code based on the time information available to the GPS receiver; and the time information of the boundary of the one cycle of the spread code detected in the second step. And the time information obtained by the difference between the known orbit information of the GPS satellite and the arrival time of the radio wave from the GPS satellite to the GPS reception, which is obtained from the approximate position of the GPS receiver. And a third step of detecting a time component of one period or more of the spread code for the time synchronization method in the positioning system. 2. In the third step, time information of a boundary of one cycle of the spread code detected in the second step, known orbit information of the GPS satellite, and an approximate value of the GPS receiver. By rounding off the digit of 100 μsec of the value of the time information obtained by the difference between the arrival time to the GPS reception of the radio wave from the GPS satellite obtained from the position and the spreading code for the time synchronization. The time synchronization method in the positioning system according to claim 1, wherein a time component of one cycle or more is detected. 3. A first step of detecting a time component of one cycle or less of the spread code for time synchronization by detecting a synchronization timing of the spread code of a spread spectrum signal from a GPS satellite, After the synchronization of the spreading code is completed in one step,
A second step of detecting the time information of the bit boundary of the spread spectrum demodulated data by the time information available to the GPS receiver; and the time information of the bit boundary detected in the second step, Known orbit information of the GPS satellite and the GP
The GPS obtained from the approximate position of the S receiver
A third step of detecting a time component of one or more cycles of the spread code based on time information obtained from a difference between the arrival time of a radio wave from a satellite and the GPS reception; Time synchronization method. 4. In the third step, time information of a bit boundary of the data detected in the second step, known orbit information of the GPS satellite, and an approximate position of the GPS receiver. The time information obtained by the difference between the arrival time of the radio wave from the GPS satellite to the GPS reception obtained from the
Detecting a time component of one or more cycles of the spreading code for the time synchronization by adding or subtracting a time error smaller than the sum of the error of the propagation time from the S satellite to the GPS receiver. The time synchronization method in the positioning system according to claim 3, characterized in that. 5. A receiving means for receiving radio waves from GPS satellites, a storage means for storing at least orbit information of the GPS satellites, and a spread code synchronization for spread spectrum signal radio waves received by the receiving means. Spreading code synchronization detecting means for detecting, clock means for providing time information, and the synchronization time point detected by the spreading code synchronization detecting means as a time component of one cycle or less of the spreading code for time synchronization, After the synchronization of the spreading code is completed, the time information of the boundary of one cycle of the spreading code is acquired from the clock means, and the time information of the boundary, the known orbit information of the GPS satellite, and the GPS receiver are acquired. The time synchronization obtained by the time information obtained from the difference between the approximate position and the arrival time of the radio wave from the GPS satellite to the GPS reception is obtained. A time synchronization detecting means for obtaining a time component of one period or more of the spreading code for obtaining the time synchronization. 6. The time synchronization detecting means includes time information at a boundary of one cycle of the spread code and the GPS.
The value of the time information obtained by the difference between the arrival time of the radio wave from the GPS satellite to the GPS reception, which is obtained from the known orbit information of the satellite and the approximate position of the GPS receiver, is rounded to the nearest 100 μsec. The GPS receiver according to claim 5, wherein a time component of one period or more of the spread code for the time synchronization is detected by performing the above. 7. Receiving means for receiving radio waves from GPS satellites, storage means for storing at least orbit information of the GPS satellites, and synchronization of spread codes for spread spectrum signal radio waves received by the receiving means. Spread code synchronization detecting means for detecting, clock means for providing time information, bit boundary detecting means for detecting a boundary between bits of information from the GPS satellites, and synchronization time point detected by the spreading code synchronization detecting means. The time information of one cycle or less of the spread code for time synchronization is obtained, and the time information of the bit boundary detected by the bit boundary detection unit is obtained from the clock means, and the time information of the boundary and the Known orbit information of GPS satellites and G
The GP obtained from the approximate position of the PS receiver
Time synchronization detection for obtaining the time synchronization by obtaining a time component of one period or more of the spreading code for the time synchronization based on the time information obtained by the difference between the arrival time of the radio wave from the S satellite and the GPS reception. And a GPS receiver. 8. The time synchronization detecting means, time information of a bit boundary detected by the bit boundary detecting section, known orbit information of the GPS satellite, and the GPS.
The time information obtained by the difference between the approximate position of the receiver and the arrival time of the radio wave from the GPS satellite to the GPS reception includes the time information usable by the GPS receiver and the accurate time information. By adding or subtracting a time error that is smaller than the sum of the difference between the time difference and the error in the propagation time from the GPS satellite to the GPS receiver, to obtain a time component of one or more cycles of the spreading code for the time synchronization. The GPS receiver according to claim 7, which detects.