JP2002131410A - Gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power consumption in power source by shortening TTFF. SOLUTION: In parallel to signal reception and position measurement operation, the information on position and the like of a visible satellite is introduced and preserved (100A and 102A). Only when the period of power-off is short enough (112 and 114), the information is used (100B and 102B) immediately after a power-on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention selects a plurality of positioning satellites in a number of positioning satellites existing in orbit around the earth, and selects a number of positioning satellites equal to or more than the number required for positioning, and determines a current position based on signals received from the positioning satellites. And a GPS receiver for performing positioning calculation for deriving a moving speed and the like. It should be noted that “GPS” in this application is a GPS operated by the United States.
(Global Positioning System) and other types of GNSS (Global Navigation Satellite S) based on the same principle.
system or GNSS with various differentials or arguments.

[0002]

2. Description of the Related Art A GPS receiver receives signals indicating a detailed orbit, a signal transmission time, and the like from a plurality of positioning satellites existing in orbit around the earth, and based on the received signals, the GPS receiver.
This device derives the current position, moving speed, etc. of the receiver.
The GPS receiver is a positioning device having high positioning accuracy, and at the same time, is a positioning device that is much smaller and cheaper to manufacture than conventional positioning devices. Therefore, the GPS receiver is mounted on a moving body such as a vehicle for navigation. Various types and types that are carried by humans during outdoor activities have been developed. Generally, a GPS receiver of a type mounted on a mobile object or carried by a person is required to be driven by a limited power source such as a battery, and to be power-saving. A typical technique for saving power of a GPS receiver is a technique called intermittent reception or intermittent positioning. This method performs signal reception and positioning calculation from positioning satellites at predetermined time intervals or as necessary, and at other times, cuts off power supply to various circuits in the GPS receiver, cuts clock, and reduces frequency. This is a method of suppressing power consumption in those circuits.

FIG. 1 shows a schematic configuration of a GPS receiver.
The GPS receiver shown in FIG. 1 converts a signal received from a positioning satellite by an antenna 10 into a frequency conversion unit 14 using a carrier (local oscillation signal) supplied from a carrier generation unit 12.
The received signal after down-conversion is correlated by the correlator 18 using the pseudo-noise code from the code generator 16, and as a result, the orbit data is demodulated by the demodulator 20 from the spectrum-spread signal. Etc. are demodulated. The processing control unit 22 includes the carrier generation unit 1
2 and the frequency and phase of the carrier and pseudo-noise code in the code generator 16 to synchronize the carrier and pseudo-noise code with the received signal.
A demodulation output from 0 is input, and a well-known positioning operation is performed based on the demodulation output and the above-mentioned information on synchronization control, for example, a code phase. The power control unit 24 is a circuit that controls power supply to each component circuit in the GPS receiver.
GPS that performs intermittent reception intermittent positioning by power supply control
In the receiver, the power control unit 24 is the processing control unit 2
The power cutoff control is executed under the status of the positioning calculation and time management in 2.

FIG. 2 shows the flow of operation of a conventional GPS receiver, particularly the flow of operation immediately after power is turned on.
As shown in this figure, a conventional GPS receiver generally includes:
The satellite selection was executed immediately after the power was turned on (100). That is, although many positioning satellites are launched in orbit around the earth, positioning satellites at visible positions (azimuth and elevation) from the current position of the GPS receiver, that is, visible satellites, are some of the many positioning satellites. Therefore, it is necessary to identify a visible satellite first before executing the positioning calculation. In addition, when performing a positioning operation, it is necessary in principle to acquire a predetermined number or more of visible satellites. When the number of visible satellites is equal to or greater than the number required for the positioning calculation, it is desirable to select, from those visible satellites, those that are considered to provide relatively high positioning accuracy, for example. Therefore, in step 100 in FIG. 2, ephemeris information previously stored in or around the processing control unit 22 or previously collected from any positioning satellite,
Based on a real-time clock (RTC) generated in or around the processing control unit 22 and giving the current date and time, and a rough GPS receiver position given as a result of the previous positioning or as an initial setting item from the user. , The processing control unit 22 determines the position (azimuth and elevation) of each positioning satellite as viewed from the GPS receiver at the current date and time, and based on the result, detects a visible satellite from the positioning satellites, and Select more than the required number of visible satellites to use for positioning from among them.

[0005] The processing control unit 22 receives and demodulates the signal from the visible satellite selected in step 100,
It controls the carrier generator 12 and the code generator 16.
That is, the processing control unit 22 controls the Doppler shift appearing in the carrier component of the received signal through the operation of controlling the frequency of the carrier output from the carrier generating unit 12 so that the frequency is synchronized with the received signal from the positioning satellite. From the frequency control information for the carrier generator 12 (10
2) The code generator 16 generates a pseudo-noise code corresponding to the selected visible satellite from the code generator 16 so that the received signal is spectrum despread by the pseudo-noise code.
6, the information related to the pseudorange from the visible satellite to the GPS receiver is collected (104), and the information demodulated by the demodulation unit 20, that is, the details of the selected visible satellite are collected. Orbit data indicating the orbit, information indicating the transmission time of the signal, and the like are collected (106). The processing control unit 22 executes the positioning calculation based on the information thus obtained (108). For example, the current position of the GPS receiver is obtained based on the orbit data, the pseudo distance, and the current date and time, or the moving speed and direction of the GPS receiver are obtained from the detected Doppler shift or the temporal change of the obtained current position.

[0006]

As described above, in positioning in the GPS receiver, it is necessary to select a number of positioning satellites, that is, visible satellites at positions visible from the current position of the GPS receiver, in a number equal to or more than the number required for positioning calculation. It is essential.
Whether or not an arbitrary positioning satellite is visible is determined by the relative positional relationship between the positioning satellite and the GPS receiver, and the relative positional relationship is determined with the passage of time (that is, movement of the GPS receiver and positioning). (With the orbit of the satellite). Therefore, for example, when the power of the GPS receiver is turned on after being turned off for several days, the relative positional relationship described above should have changed greatly while the power is off.
Therefore, in the conventional GPS receiver, immediately after the GPS receiver is turned on, the derivation of the visible satellite value and the selection of the visible satellite based on the result are always executed.

However, since the derivation of the visible satellite value and the like require power and time, the process of deriving the visible satellite value immediately after the power is turned on requires a longer battery life and TTFF (TFF).
It can be said that this is one factor that hinders shortening of imeTo First Fix). SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and the power consumption of the power supply can be reduced by omitting the derivation of a visible satellite value or the like immediately after the power is turned on again under specific conditions. The purpose is to reduce the suppression TTFF.

[0008]

In order to achieve the above object, the present invention provides (1) information on the orbit from a positioning satellite in orbit around the earth and information on the collected information and time. The position of the positioning satellite is obtained based on the obtained position, and a predetermined number or more of visible satellites to be used for positioning are selected from the positioning satellites based on the obtained position, a signal is received from the selected visible satellite, and positioning is performed by a predetermined positioning operation based on the signal. In the GPS receiver that derives the result, (2) in parallel with the signal reception and the positioning calculation, the visible satellite value information that can be used for selecting or capturing a visible satellite including the information on the position of the positioning satellite is derived as stored data. (3) data storage means for storing stored data in association with the derivation date and time; and (4) visible satellites for selecting visible satellites. Whether to derive the information anew or to use the stored data as visible satellite value information, comprising: a stored data availability determining unit that determines by comparing the derived date and time and the current date and time associated with the stored data, (5) A visible satellite is selected according to the result of this determination.

The basic point of view in the present invention is as follows.
The point is that the relative positional relationship between the positioning satellite and the GPS receiver changes over time. In other words, whether or not the visible satellite value information derived at a certain point in time can be used as the visible satellite value information at the time of the immediate positioning calculation and satellite selection for that purpose is determined by the derivation date of the visible satellite value information. And the current date and time. Therefore, in the GPS receiver according to the present invention, first, the visible satellite value information is derived in parallel with the signal reception and the positioning calculation, and is stored as storage data in association with the derived date and time. Further, at a later time (for example, immediately after the power is turned on), it is determined whether or not the stored data can be used as visible satellite value information based on the derived date and time of the stored data and the current date and time.

If it is determined that the satellite cannot be used, a visible satellite is selected using newly derived visible satellite value information, similarly to a conventional GPS receiver. by this,
It is possible to cope with a change in the relative positional relationship due to a long-time power-off or the like. Conversely, if it is determined that the visible satellite can be used, the visible satellite is selected using the visible satellite value information given as the stored data, and the visible satellite is selected using the newly derived visible satellite value information. In comparison with the case, at least the process of deriving the visible satellite value information can be omitted. That is, power consumption and TTFF can be reduced.

It is determined that the visible satellite can be selected using the stored data as the visible satellite value information because, for example, a predetermined time or more is determined from the derivation date and time associated with the stored data to the current date and time. Is not passed. That is, when the power is turned off for a short time (several minutes to several tens of minutes) due to the intermittent reception intermittent positioning operation, the stored data is used as visible satellite value information without any particular trouble or deterioration in accuracy. be able to.

Further, the derivation of the stored data is executed at a predetermined frequency (for example, at one-hour intervals), and the results are stored in the data storage means in a plurality of ways in association with the respective derivations on a date basis. , A table of visible satellite value information versus derivation date and time can be constructed. The period that the positioning satellites orbit the earth along each orbit is constant,
Therefore, the position of each positioning satellite viewed from an arbitrary point on the earth periodically repeats a specific pattern, so the above table is constructed in parallel with signal reception and positioning calculation,
By using this table immediately after power-on or the like, it is possible to omit derivation of visible satellite value information. More specifically, whether or not stored data that can be used as visible satellite value information at this time is included in the plurality of types of stored data on the data storage unit is determined by the orbiting cycle of each positioning satellite, The determination can be made based on the data derivation date and time and the current date and time. If it is determined that it is included, the stored data is used as visible satellite value information for selecting a visible satellite or the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the present invention can be carried out with the apparatus configuration shown in FIG. 1, and for the purpose of simplifying the description, the following description assumes the apparatus configuration in FIG. 1. Also,
Parts similar or corresponding to those in the conventional procedure shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. Procedures common to the embodiments are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 3 shows a GP according to the first embodiment of the present invention.
5 shows a flow of operation of the S receiver, particularly, a flow of operation immediately after power-on. This operation is executed in response to an operation of a power switch (not shown) or the like, and is executed at a predetermined frequency in conjunction with intermittent reception intermittent positioning according to a signal from the power control unit 24.

In the procedure shown in FIG. 1, the processing control section 22 executes Steps 100A and 102A in parallel with Steps 104 to 108 in the form of a background job or the like executed using idle time. Step 1
00A determines the position (azimuth and elevation) of each positioning satellite, especially the visible satellite, at the time of execution based on the collected orbit or ephemeris data, the current date and time given by the RTC, the current position obtained in step 108, and the like. Step 102A is a step of detecting the Doppler shift appearing in the carrier component in the received signal based on the frequency control information on the carrier control unit 12. The information obtained by executing steps 100A and 102A, that is, the visible satellite value information, is at least associated with the date and time when the information was derived before the power was turned off due to the operation of the power switch or the intermittent control, The data is stored in a nonvolatile memory or the like provided in or around the processing control unit 22 (110).

The visible satellite value information, that is, the stored data, stored in this manner is used according to the situation immediately after the power supply to each circuit in the GPS receiver is turned on by operating the power switch or intermittent control. . That is, the processing control unit 2
2 is R from the derivation date and time associated with the stored data.
If the elapsed time up to the current date and time given by TC or the like exceeds a predetermined valid time (112, 114),
Derivation of the position of each positioning satellite, selection of visible satellites, and detection of Doppler shift are performed in the same manner as in the conventional procedure shown in FIG. 2 (100, 102). If it is within the valid time (1
12, 114), since the stored data can be regarded as relatively new information, that is, information that is new enough to be used for selecting a visible satellite, satellite selection is performed using the stored data as visible satellite value information (12, 114). 100B, 102
B). In the procedure shown in FIG. 3, since the effective time for the position of the positioning satellite (azimuth and elevation) and the effective time for Doppler shift are separately set, the steps related to the use of the stored data are the same as steps 112 and the like. It is divided into step 114 and the like.

Therefore, in this embodiment, if the period during which the power is off is shorter than the valid time (for example, if the power is off due to intermittent reception intermittent positioning), the visible satellites in steps 100 and 102 Since the recalculation of the value is not performed, the time (TTF) required after the power is turned on until the processing control unit 22 outputs the positioning result to the display unit or the like.
F) is shortened, and the power supply power required for re-derivation of the visible satellite value is saved. In other words, it is possible to obtain a GPS receiver suitable for carrying, which has a long battery and can quickly obtain a positioning result.

FIG. 4 shows a GP according to a second embodiment of the present invention.
The operation of the S receiver will be described. The operation shown in this figure is an operation executed immediately after the power is turned on under the operation of the power switch or the intermittent control, similarly to the operation shown in FIG. This embodiment is the second
A major difference from the embodiment is that steps 100A and 102A are executed at a predetermined frequency or more (for example, at intervals shorter than one hour), and the result is stored in a non-volatile memory provided in or around the processing control unit 22. It is to store in association with the derivation date and time, and particularly to construct and store a table of derivation date and time vs. stored data (110A). Immediately after the power is turned on, the processing control unit 22 obtains the current date and time from the RTC or the like (112A), checks whether or not there is stored data that can be used as visible satellite value information at the current date and time (112B). If is stored in the table, the satellite selection is executed using this (100C), and otherwise, steps 100 and 102 are executed.

In this embodiment, attention is paid to the fact that the positioning satellite orbits the orbit of the earth at a predetermined cycle, and therefore, the position of each positioning satellite viewed from an arbitrary point on the earth is changed every predetermined time. To repeat a specific pattern. Specifically, in the GPS operated by the United States, since the orbiting cycle of the positioning satellite with respect to the earth's surface is about 23 hours and 56 minutes, if the visible satellite value information is derived and stored in about 1 hour intervals,
Derivation of visible satellite value information immediately after power-on can be omitted. That is, in step 112B, it is determined whether or not stored data having a derived date and time whose difference from the current date and time is substantially equal to a natural number multiple of the orbiting cycle of the positioning satellite exists on the table. Only when there is, it is determined that there is stored data that can be used as visible satellite value information, and the stored data is specified. In step 100C, the stored data is used. Even in this case, the effects of reducing the power consumption of the power supply and shortening the TTFF can be obtained.

It should be noted that "substantially equal" is described in step 100B in the description of step 112B.
This is to the effect that there may be an error that does not hinder the execution of C, that is, to provide an allowable range. The visible satellite value information to which the present invention can be applied includes, for example, the position (azimuth and elevation) of each positioning satellite, the Doppler shift appearing in the carrier component, the position of the GPS receiver at the time of the last positioning, Health information about each positioning satellite, an error index for each positioning satellite, and the like can be listed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example configuration of a GPS receiver.

FIG. 2 is a flowchart showing a conventional procedure.

FIG. 3 is a flowchart illustrating a procedure according to the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a procedure according to a second embodiment of the present invention.

[Explanation of symbols]

 22 processing control unit, 24 power supply control unit.

Claims (4)

[Claims] An information on the orbit is collected from a positioning satellite in an orbit around the earth, a position of the positioning satellite is obtained based on the collected information and information on time, and a positioning is selected from the positioning satellites based on the obtained position. In a GPS receiver that selects a predetermined number or more of visible satellites to be used and derives a positioning result by receiving a signal from the selected visible satellite and performing a predetermined positioning operation based on the signal, in parallel with the signal reception and the positioning operation, Stored data deriving means for deriving visible satellite value information that can be used for selection or acquisition of visible satellites including information on the position of a positioning satellite as stored data, and data storing means for storing the stored data in association with the derivation date and time. Whether to derive the visible satellite value information again or to use stored data as visible satellite value information when selecting visible satellites And a storage data availability determining means for determining by comparing the derived date and time associated with the stored data with the current date and time, and selecting a visible satellite according to the result of the determination. . 2. The GPS receiver according to claim 1, wherein the storage data availability determining means determines whether the storage data is visible or not only when a predetermined time has not elapsed from a derivation date and time associated with the storage data. A GPS receiver which determines to use as value information. 3. The GPS receiver according to claim 1, wherein the stored data deriving means derives the stored data at a predetermined frequency, and the data storing means determines a plurality of stored data having different derivation dates and times as the derivation date and time. The stored data availability determination means determines whether or not the stored data that can be used as visible satellite value information at present is included in the plurality of types of stored data on the data storage means. A GPS receiver which determines based on the orbital cycle of the satellite, the derivation date and time of each stored data and the current date and time, and determines that the stored data is used as visible satellite value information when it is determined that the data is included. Machine. 4. The GPS according to claim 1, wherein:
A GP comprising: an intermittent operation control means for intermittently executing the operation of the GPS receiver including the positioning operation.
S receiver.