JPH0634738A - GPS receiver - Google Patents

Abstract

(57) [Summary] [Purpose] Shorten the time required to start positioning for the first time. [Configuration] In addition to a first satellite selection prohibited range 200 that is a low elevation angle range, a second satellite selection prohibited range 400 that is a high elevation angle range is set. Second satellite selection prohibited range 400
Is set by detecting the maximum elevation angle of the receivable GPS satellites, and the range is updated and set appropriately by test reception or the like. [Effect] When a signal from a GPS satellite with a high elevation angle is always blocked, the GPS satellite with a high elevation angle is not a target for priority selection and search, and the time required to start positioning for the first time is shortened. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to GPS (Global Position
ioning System) receiver, and more particularly to its satellite selection system.

[0002]

2. Description of the Related Art GPS transmits a signal from a predetermined number of GPS satellites launched in an orbit around the earth, and a GPS receiver on a mobile body receives this signal,
This is a system for measuring the position, speed, etc. of the moving body.
In the GPS receiver, four GPS satellites are used for three-dimensional measurement (three-dimensional positioning) of the position, speed, etc. of the moving body, and three GPS satellites for two-dimensional measurement (two-dimensional positioning). Need to receive signals from.

FIG. 6 shows a schematic structure of a GPS receiver. The GPS receiver receives the signal transmitted from the GPS satellite by the antenna 10 and outputs the received signal to the RF.
The signal is amplified by the amplifier circuit 12, and further converted to an intermediate frequency by the frequency conversion / amplification circuit 14.

The signal converted into the intermediate frequency by the frequency conversion / amplification circuit 14 is supplied to the carrier synchronization / code synchronization circuit 16. Carrier synchronization / code synchronization circuit 16
Is the phase synchronization between the carrier of the output signal of the frequency conversion / amplification circuit 14 and the output of the built-in carrier oscillator,
Also, the PN relating to the output signal of the frequency conversion / amplification circuit 14
The code (pseudo noise code) and the output of the built-in code oscillator are synchronized in phase. Among these functions, the carrier synchronization function captures the signal from the GPS satellite, and the code synchronization function despreads the signal from the GPS satellite.

The decoding unit 18 demodulates and decodes the received signal from the GPS satellite input via the carrier synchronization / code synchronization circuit 16. The GPS satellite transmits a signal with a predetermined frame structure, and by demodulating and decoding the received signal from the GPS satellite, data such as almanac data and ephemeris data can be obtained. The alnamac data is orbital history data, and is data including rough orbital information of each GPS satellite. Ephemeris data is orbital data, which is orbital information of GPS satellites related to transmission. The almanac data is stored in the almanac memory 20, and the ephemeris data is stored in the ephemeris memory 22.
Respectively stored in.

When performing positioning calculation in the GPS receiver, it is necessary to receive signals from 3 to 4 GPS satellites as described above. Some GPS satellites are invisible from the current position of the moving body, and the positioning accuracy differs depending on which combination of GPS satellites is used for positioning calculation. The satellite selection unit 24 selects and determines a combination of 3 to 4 GPS satellites used for positioning calculation by a predetermined algorithm, controls the operation of the carrier synchronization / code synchronization circuit 16 based on the selection result, and the positioning calculation unit 24. 26 to control the operation. At that time, the satellite selection unit 24 uses the almanac data on the almanac memory 20 and the approximate position (estimated position) and time of the moving body input from the estimated position input unit 28.

The positioning calculation unit 26 calculates the position, speed, etc. of the moving body based on the pseudo range and the ephemeris data of the GPS satellites related to the combination selected by the satellite selection unit 24 (positioning calculation). This calculation is performed according to a predetermined algorithm. Here, the pseudo distance means a distance obtained by adding a clock offset of the GPS receiver and the like to the radio wave propagation distance from the GPS satellite to the GPS receiver. The pseudo distance is obtained by obtaining satellite time (time when a signal is transmitted from a GPS satellite) from the phase information of code synchronization in the carrier synchronization / code synchronization circuit 16 and comparing it with the time of the GPS receiver by the built-in clock. be able to. The ephemeris data is read from the ephemeris memory 22. Ephemeris data is GPS
Since the orbit of the satellite is shown, the position of the moving body can be obtained by using it together with the pseudo range. The position and the like obtained by the positioning calculation are output for display, recording and the like.

FIG. 7 shows a flow of operations particularly related to satellite selection among the general positioning operations of the GPS receiver described above. As shown in this figure, the satellite selection unit 24 first determines whether or not the estimated position and time are stored (100), and if not, waits for an input from the estimated position input unit 28. (102). If the estimated position and the time are stored, the satellite selection unit 24 proceeds to the operation after step 104. When the estimated position and time are input from the estimated position input unit 28, the satellite selection unit 24 stores the information and moves to the operation in step 104 and thereafter.

There are various conventional setting methods for the satellite selection standard. For example, if the number of satellites that can be received simultaneously is large, the receivable satellites are sequentially set from satellites with a high elevation angle among the visible satellites obtained by calculation. Accuracy index DO
In many cases, a good combination of P (Dilution Of Precision) is determined. In any case, high elevation satellites are important for 3D positioning. In step 104, it is determined whether or not the preferential satellite selection is necessary. If not, the satellite selection unit 24 selects the GPS from outside the predetermined satellite selection prohibited range.
A satellite combination is selected (106). The satellite selection prohibition range is usually set to an elevation angle range of 5 ° to 15 ° or less, that is, a range in which signals from GPS satellites are easily shielded at low elevation angles. The satellite selection unit 24 causes the carrier synchronization / code synchronization circuit 16 to capture the GPS satellites associated with the selected combination, and tracks the captured GPS satellites (10
8). Furthermore, regarding GPS satellites that are tracking, positioning calculation (1
10) is performed as described above. The satellite selection unit 24 appropriately determines whether or not the combination of GPS satellites needs to be updated (112), and if so, executes the satellite selection operation.

If it is determined in step 104 that priority satellite selection is required, step 114 is executed instead of step 106. In step 114, the satellite selection unit 24 determines that the GPS is outside the satellite selection prohibited range.
Among the satellites, 3 to 4 satellites including high-elevation-angle GPS satellites, which can expect stable signal strength and stable reception, are selected.
By doing so, the time required to start the first positioning can be shortened.

That is, the oscillation frequency of the carrier oscillator mounted on the GPS receiver is accurate because the atomic clock is used, but the oscillation frequency of the carrier oscillator mounted on the GPS receiver has some error. There is. Therefore,
When the signal from the GPS satellite is captured by the carrier synchronization / code synchronization circuit 16, the carrier code is usually synchronized with respect to one GPS satellite, and the carrier frequency error with respect to other GPS satellites is estimated based on the result. I am trying to do it. At that time, the first G to be captured
If the PS satellites can be acquired properly, that is, quickly and reliably, the time until the first positioning is started can be shortened. Conventionally, it is determined that priority satellite selection is necessary immediately after power-on or when a long time has passed since the last positioning (1
04), a GPS satellite with a high elevation angle, which has strong signal strength and is expected to be stably received, was selected as a satellite for priority selection (114).

[0012]

However, when the signal from the GPS satellite of high elevation angle is always blocked,
If such a GPS satellite is selected as the GPS satellite related to the priority selection, it takes a long time to start the first positioning.

Further, when the satellite to be received is selected again after the positioning is steadily started, it is always attempted to capture the signal without knowing that the satellite signal is blocked. Positioning interruption may occur. this is,
In particular, the number of GPS satellites that can be received is 3 required for positioning calculation.
It tends to occur when there is not enough room for 4 to 4.

The present invention has been made to solve the above problems, and the first positioning is performed even in an application in which a signal from a GPS satellite having a high elevation angle is always blocked. It is an object of the present invention to provide a GPS receiver with good performance that can reduce the time required for the process.

[0015]

In order to achieve such an object, the GPS receiver of the present invention has a range in which an elevation angle from a moving body is a predetermined value or less (hereinafter referred to as a first satellite selection prohibition range). ), The range in which the elevation angle is greater than or equal to a predetermined value (hereinafter referred to as the second satellite selection prohibited range) is set as the satellite selection prohibited range, and positioning calculation is performed from the satellite selection range other than the satellite selection prohibited range. It is characterized in that a combination of GPS satellites to be used is selected.

[0016] The claim 2 is a GP capable of receiving a signal.
It is characterized in that a boundary between the second satellite selection prohibited range and the satellite selection range is set based on the elevation angle of the S satellite.

[0017]

In the present invention, the high elevation range is added to the satellite selection prohibited range. Therefore, when the signal from the GPS satellite with a high elevation angle is always blocked, the GPS satellite is not selected, so that the time required for the first positioning is shortened and the performance deterioration of the positioning time is prevented. It

In the second aspect, the boundary between the second satellite selection prohibited range and the satellite selection range is set. That is, the boundary is learned and adaptively updated based on the elevation angle of the receivable GPS satellite. This allows the satellite selection range to be maintained almost always at an appropriate level.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those shown in FIGS. 6 and 7 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows a GP according to the first embodiment of the present invention.
Among the operations of the S receiver, the flow of operations related to satellite selection is shown. Since the present invention can be implemented by a GPS receiver having a device configuration as shown in FIG.
A case where the operation of FIG. 1 is implemented by the configuration shown in FIG. 6 will be described.

In the operation of this embodiment, steps 106 and 114 in the conventional example are replaced by 106a and 114a, respectively.
The operation is replaced with. In step 106a, the GPS satellites used for the positioning calculation are selected and captured from the area other than the first satellite selection prohibited range. In step 114a, G used for positioning calculation is selected from areas other than the first satellite selection prohibited range and the second satellite selection prohibited range.
PS satellites are selected and acquired.

The first satellite selection prohibited range is 20 in FIG.
It is in the low elevation range as seen from the GPS receiver 300, as indicated by 0. That is, it is a satellite selection prohibited range in the conventional example, for example, an elevation angle range of 5 ° to 15 ° or less. Also, the second satellite selection prohibited range is 4 in FIG.
As shown as 00, it is a range of high elevation angle viewed from the GPS receiver 300. Whether or not the range of elevation angles is the second satellite selection prohibited range 400 is determined according to the usage mode of the GPS receiver. Further, this boundary angle is appropriately updated as described later.

A situation in which the GPS receiver 300 of this embodiment has an advantage occurs, for example, when the GPS receiver is mounted as a position sensor on an observation balloon or the like. As shown in FIG. 3, when the GPS receiver 300 is suspended below the balloon 500, the GPS satellites in the high elevation range as well as the low elevation range are blocked by the balloon 500 and disappear. In the present embodiment, when executing the prioritized satellite selection, the GPS satellites of high elevation angle blocked by the balloon 500 are excluded from the selection target,
Therefore, it is characterized by shortening the time until the first positioning and the search time when the GPS satellite mask is used.

FIG. 4 shows the flow of the setting operation of the second satellite selection prohibited range 400 in this embodiment. This operation is executed before the operation of FIG. 1 is performed or when a predetermined time has elapsed after the start of positioning.

The satellite selection unit 24 displays a predetermined time T from the present time.
The elevation angle and time of the GPS satellite received within 1 are stored (600). G with multiple receive channels, for example
In the PS device configuration, the elevation angle and the time of the GPS satellite received by each channel are stored, and the predetermined time T1 is stored.
Erase the previously stored contents. Furthermore, the satellite selection unit 24
Determines whether the second satellite selection prohibited range 400 has already been set (602), and if not set, detects the maximum elevation angle from the stored elevation angles of the GPS satellites (604). Then, thereafter, for a predetermined time T2, the range above the detected maximum elevation angle is set as the second satellite selection prohibited range 400.

In addition, the second satellite selection prohibition range 40 has already been reached.
If 0 is set, steps 602 to 60
Go to 4. In step 604, it is determined whether or not the current number of receiving satellites is the maximum receivable number. The maximum receivable number is, for example, the first satellite selection prohibited range 2
The number of GPS satellites belonging to a range other than 00 and within the maximum receivable number. As a result of the determination, when the current number of receiving satellites is the maximum receivable number, the satellite selecting unit 24 maintains the second satellite selection prohibited range 400 as it is, and when the current number of receiving satellites is not the maximum receivable number. Then, steps 606 and 608 are executed.

At step 606, the satellite selector 2
The carrier synchronization / code synchronization circuit 16 causes the second
The GPS satellites belonging to the satellite selection prohibition range 400 are acquired on a trial basis. If the acquisition is successful, the satellite selection unit 24
Stores the elevation angle and time of the GPS satellite (60
8). After that, when the process proceeds to step 604, step 6
Since the elevation angle stored in 08 is included in the target of maximum elevation angle detection, the range of the second satellite selection prohibition range 400 is expanded.

Such range expansion occurs, for example, when the shape of the balloon 500 contracts after a long flight. Therefore, according to the present embodiment, in such a case, the second
The satellite selection prohibition range 400 can be set learning adaptively.

FIG. 5 shows a GP according to the second embodiment of the present invention.
The flow of the operation of the S receiver, particularly the operation of setting the second satellite selection prohibited range 400 is shown. In this embodiment, steps 600, 604 and 60 of the first embodiment.
Instead of 8, 600a, 604a and 608a are executed.

The difference between these steps and that of the first embodiment is that the azimuth in addition to the elevation angle is used for setting the second satellite selection prohibited range 400. That is, by detecting the maximum elevation angle that demarcates the second satellite selection prohibited range 400 in association with the azimuth and setting the range 400, a more flexible setting of the second satellite selection prohibited range 400 becomes possible. ing.

The configuration of the present invention is not limited to the device configuration shown in FIG. In addition, GP of high elevation
The application is not limited to balloons and the like as long as the signal from the S satellite is blocked.

[0032]

As described above, according to the present invention,
Since the range in which the elevation angle from the moving body is a predetermined value or more is added to the satellite selection prohibition range as the second satellite selection prohibition range, even if the signal from the high elevation angle GPS satellite is always blocked, The time required for positioning can be shortened, and a high-performance GPS receiver can be obtained.

Further, according to the second aspect, the boundary between the second satellite selection prohibited range and the satellite selection range is set based on the elevation angle of the GPS satellite capable of receiving the signal. Therefore, the satellite selection range is almost always appropriate. Can be maintained at

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation flow of a GPS receiver according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the meaning of first and second satellite selection prohibited ranges in this embodiment.

FIG. 3 is a diagram showing an example of application of this embodiment.

FIG. 4 is a flowchart showing a flow of a setting operation of a second satellite selection prohibited range in this embodiment.

FIG. 5 is a flowchart showing the flow of the operation of the GPS receiver according to the second embodiment of the present invention, particularly the operation of setting the second satellite selection prohibited range.

FIG. 6 is a block diagram showing an example of a device configuration of a GPS receiver.

FIG. 7 is a flowchart showing an operation flow of a GPS receiver according to a conventional example.

[Explanation of symbols]

 24 satellite selection unit 26 positioning calculation unit 200 first satellite selection prohibited range 300 GPS receiver 400 second satellite selection prohibited range

Claims (2)

[Claims] 1. Receiving means for receiving a signal from a GPS satellite, which includes ephemeris data indicating the orbit of the GPS satellite and almanac data indicating the approximate orbit of each GPS satellite, and the almanac data and the approximate current position of a mobile body to be mounted. And GPS used for positioning calculation based on time information
A satellite selection means for selecting a combination of satellites; and a positioning calculation means for performing a positioning calculation using pseudoranges and ephemeris data of GPS satellites related to the combination,
In a GPS receiver that obtains the current position of a mobile body to be mounted by positioning calculation, the satellite selection means sets a first satellite selection prohibited range in which the elevation angle from the mobile body is a predetermined value or less and the elevation angle is a predetermined value or more. A GPS receiver characterized by selecting a combination of GPS satellites used for positioning calculation from a satellite selection range that is a range other than the second satellite selection prohibited range. 2. The GPS receiver according to claim 1, wherein the satellite selection means sets a boundary between the second satellite selection prohibited range and the satellite selection range based on an elevation angle of a GPS satellite capable of receiving a signal. And GPS receiver.