JP3338845B2 - Diversity receiving GPS receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Positioning Sys- tem) for receiving radio waves transmitted from a plurality of artificial satellites and calculating a current position based on the received signals.
tem) The present invention relates to a receiver, and more particularly, to a diversity receiver GPS receiver having a plurality of receiving antennas.

[0002]

2. Description of the Related Art In recent years, a GPS positioning system has attracted attention as a navigation system for a moving body such as a vehicle or a ship. The GPS system receives radio waves from three or more satellites in a two-dimensional position and four or more satellites in a three-dimensional position, out of radio waves from more than twenty satellites orbiting the earth. Then, based on the received data, the distance between each satellite and the moving object equipped with the system is calculated, and the current position of the moving object, that is, the user, is calculated from the calculated distance.

[0003] In the GPS system, it is necessary to receive radio waves from satellites. However, in places where the view of the sky is poor such as urban areas or mountainous areas, radio waves from satellites are blocked.
There is a problem that the required number of satellites (three or four) cannot be received, and the positioning accuracy is deteriorated, or in the worst case, the positioning becomes impossible.

As a technique for compensating for this problem, a diversity receiver as shown in FIG. 5 has been conventionally proposed. In FIG. 5, la and lb are receiving antennas, 2 is an RF receiving unit that demodulates a received RF signal and outputs demodulated data, 3 is a calculating unit that calculates its current position based on the demodulated data, and 4 is a receiving antenna. a switching unit 5 for selectively switching the received signals from la and lb, a switching control unit 5 for performing antenna switching control based on the received signal level obtained by the RF receiving unit 2, and a switching unit 6 obtained by the arithmetic unit 3. This is a display unit that displays the current position on a map, for example.

In this configuration, two receiving antennas 1
a and 1b are installed so that the reception signal levels of both antennas are uncorrelated, for example, they are arranged at the front and rear of the vehicle. In the RF receiving unit 2, the antenna la or l
b, demodulates the received signal and sends it out to the arithmetic unit 3, detects the level of the received signal, and switches the switching control unit 5.
To send to. In the switching control unit 5, two antennas la and l are set based on the reception signal level transmitted from the RF reception unit 2.
The switching unit 4 is controlled so as to select the antenna having the higher received signal level among b. The arithmetic unit 3 includes the RF receiving unit 2
Calculates its current position based on the demodulated data obtained in
The current position of the player is displayed on the display unit 6 on a map or the like.

[0006]

SUMMARY OF THE INVENTION However, GPS
The cause of the positioning error in the receiver is related not only to the received signal level but also to the arrangement of the receiving satellite. For this reason, when the selection is made based on the received signal level only, when the received signal levels of both antennas are equal to or higher than a certain value, switching is performed while observing the received signal level, and only satellites arranged so that the positioning error becomes large are acquired. There is a disadvantage that an antenna that is not selected is selected, and good antenna switching is not performed in order to improve the positioning accuracy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a diversity receiving GPS receiver for switching an antenna capable of receiving a satellite so as to minimize a positioning error. To provide.

[0008]

According to a first aspect of the present invention, there is provided a diversity receiving GPS receiver for selecting a plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, and selecting a receiving signal at these receiving antennas. a switching unit that switches a manner, an RF receiver for demodulating the received signal selected in the switching unit, based on the demodulated signal data of the RF receiver, as well as calculating the current position of the self, received by one antenna Positioning accuracy reduction rate based on
(DOP) and receive with another antenna
The operation unit that calculates the DOP also based on the signals of the satellite groups that have been compared with the DOP calculated by the operation unit
The best characteristics can be obtained among the reception conditions of the antenna
To select the antenna to receive the satellite constellation signal
A diversity control device including a switching control unit for switching a switching unit; and a display unit for displaying a current position calculated by the calculation unit.
A GPS receiver, wherein the switching control unit comprises:
When the accuracy decrease rate (DOP) is larger than a predetermined threshold
Is the smaller DOP with reference to the DOP from the arithmetic unit
While the switching unit is switched at a time, the rate of decrease in positioning accuracy increases.
If the received signal level from the RF
Switch to the higher received signal level
It is characterized in that it is configured as follows.

In the GPS, the positioning accuracy greatly changes depending on the arrangement of satellites. It is DOP (Determination of positioning accuracy) that determines the quality of the satellite constellation, and the positioning error is DO.
It increases in proportion to the value of P. That is, if an antenna that receives a combination of satellites having a small DOP value can be selected, the positioning accuracy can be improved. According to the configuration of the first aspect, each of the plurality of receiving antennas receives a signal transmitted from a plurality of satellites. The signals received by these receiving antennas are selectively connected in the switching unit. The received signal is guided to the RF receiving unit and demodulated in the RF receiving unit. This demodulated signal includes the orbit data of the satellite, the data transmission time, and the like. Next, the demodulated data is input to the arithmetic unit. The calculation unit calculates the current position based on the demodulated data, calculates the positioning accuracy decrease rate (DOP) of the currently selected satellite group, and sends it to the control unit. The control unit compares the value of the positioning accuracy decrease rate (DOP) with a predetermined threshold value. When the value is larger than the threshold value, the control unit controls the switching unit to switch the receiving antenna. Continue to use the currently selected receive antenna. The current position information obtained in this way is guided to the display unit and displayed in a form that is easy for the user to understand (for example, on a map). Even if the reception system including the RF reception unit and the calculation unit is one system, it is possible to perform good reception in an area where reception conditions are poor.

A diversity receiving GPS receiver according to a second aspect of the present invention includes a plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, and a plurality of receiving antennas respectively connected to the receiving antennas for demodulating the received signals. An RF receiving unit, a plurality of arithmetic units connected to each of the RF receiving units, respectively, for calculating a current position of the mobile station based on demodulated signal data and calculating a positioning accuracy decrease rate (DOP); A switching unit for selectively switching the calculation result of the calculation unit;
A display unit for displaying a current position based on a calculation result of the calculation unit selected by the switching unit; and a predetermined threshold for a rate of decrease in positioning accuracy for each receiving antenna calculated by the calculation unit.
If the value is larger than the value, switch the switching unit to reduce the positioning accuracy
Is smaller than a predetermined threshold value,
Switching of the switching unit with reference to the received signal level
And a switching control unit configured as described above.

In short, a receiving antenna capable of receiving a group of satellites having the best characteristics is selected from among the receiving states of the receiving antennas that change moment by moment depending on the surrounding conditions, and the receiving condition of the radio wave from the satellite is poor. Good positioning can be performed at a place.

[0012] Diversity receiver GPS receiver of claim 3 according to the present invention, in the above Symbol claim 2, the switching control unit, when positioning accuracy decrease rate (DOP) is greater than the predetermined threshold the arithmetic unit While the switching unit is switched to the smaller DOP with reference to the DOP from the above, when the rate of decrease in the positioning system is smaller than the threshold value, the switching is switched to the higher received signal level with reference to the received signal level from the RF receiver. Characterized in that it is configured to perform When the rate of decrease in positioning accuracy (DOP) is larger than a predetermined threshold, the receiving antenna is switched. When the rate is smaller than the threshold, the received signal level from the RF receiver is referred to. The antenna with the higher level is selected, and in the case of one receiving system, the current antenna is maintained when the level is larger than the level threshold, and the antenna is switched when the level is smaller than the threshold. Not only judgment based on the rate of decrease in positioning accuracy, but also the level of the received signal is observed, so that finer control can be performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a diversity receiving GPS receiver according to the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a first embodiment. The first embodiment is according to claim 2. For convenience, claim 2 will be described first.

In the figure, la and 1b are GPS satellites (GPS:
Receiving antennas for receiving radio waves from the Global Positioning System), 2a and 2b are receiving antennas 1a,
RF receivers 3a, 3b for individually demodulating the received signals from 1b and outputting received data such as satellite orbit information and time information.
Calculates its own current position based on the information of the received data from each of the RF receivers 2a and 2b, and decreases the positioning accuracy decrease rate (PDOP: Position Dilution of Prediction) due to the satellite position.
4 is a switching unit for selectively switching the connection state between the calculation units 3a and 3b and the display unit 6, and 5 is a positioning accuracy reduction rate (P) from each of the calculation units 3a and 3b.
DOP), and controls the switching of the switching unit 4 by switching. The switching control unit 6 displays its current position based on the positioning result selected by the switching unit 4 on a map or in a latitude / longitude display by text or the like. This is a display unit that displays on the screen in a form that is easy for the user to understand.

Here, the receiving antennas 1a and 1b are installed apart from each other, for example, on a dashboard and a rear tray of the vehicle so that the two antennas have no correlation and the receiving states are different. The received signals are sent to the RF receivers 2a and 2b, respectively.

The RF receivers 2a and 2b are multi-channel RF receivers that can simultaneously demodulate radio waves from four or more satellites, and can simultaneously demodulate radio waves from, for example, five satellites. This is a 5-channel RF receiver. Four of the five channels demodulate the radio waves of the satellites used for calculating the current position, and the remaining one channel tracks the other satellites.

The received data demodulated in this way is sent to arithmetic units 3a and 3b. The arithmetic units 3a and 3b first calculate PDOP (positioning accuracy reduction rate due to satellite position) based on the demodulated data.

The calculation of PDOP is performed as follows. Matrix A,

[0020]

(Equation 1)

Is defined. Where α, β, γ are

[0022]

(Equation 2)

## EQU1 ## Here, (x _i , y _i , z _i ) represents the position of the i-th satellite, and (x ′, y ′, z ′) represents the coordinates of the positioning point (current position: unknown) at (x ₀ , y). _0, z ₀₎
Are the corrected coordinates when R _i ′ is the corrected distance from each satellite to the positioning point. If A ^-1 is an inverse matrix of the matrix A, and A ^T is a transposed matrix obtained by exchanging the rows and columns of the matrix A, a weight coefficient matrix (A ^T · A) ^-1 is given.

[0024]

(Equation 3)

## EQU1 ## Then, the positioning accuracy decrease rate PDOP (P represents the position in Position) due to the satellite position is

[0026]

(Equation 4)

## EQU1 ##

In place of PDOP, GDOP (geometric positioning accuracy reduction rate) or TDO given as follows:
P (positioning accuracy decrease rate with time) may be used.

[0029]

(Equation 5)

[0030]

(Equation 6)

Here, a ₄₄ represents a time element. PDO
Which of P, GDOP, and TDOP is adopted is arbitrary, and there is no special difference. PDOP is sufficient for measuring the three-dimensional position of a moving object such as a vehicle.

Now, the calculation of the PDOP (positioning accuracy reduction rate depending on the satellite position) is based on a combination of four satellites having the highest PDOP in the satellite group when five or more satellites can be acquired. Calculation. When three or four satellites can be captured, the PDOP in this combination is used. When the number of satellites that can be captured is less than three, PDOP cannot be calculated, so that the maximum value is set. The PDOP value thus calculated is sent to the switching control unit 5. If three or more satellites have been captured, the current position of the satellite is calculated using the received data of the combination of satellites at the time when the PDOP was calculated. The data of the current position is sent to the switching unit 4.

The switching control unit 5 compares the PDOPs calculated by the calculation units 3a and 3b. Here, if the value of PDOP obtained by the first calculation unit 3a is smaller, the switching unit 4
Is switched to the side that receives the data of the first arithmetic unit 3a, and if the value of the PDOP obtained by the second arithmetic unit 3b is smaller, the switching unit 4 is switched to the side that receives the data of the second arithmetic unit 3b. . If both values are the same, no switching is performed. The data of the current position selected by the switching unit 4 is sent to the display unit 6.

The display unit 8 displays the current position on the map on the screen. By doing so, it is possible to satisfactorily perform GPS positioning even in an urban area or a mountainous area where reception conditions are poor.

[Second Embodiment] FIG. 2 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a second embodiment. The second embodiment is according to claim 1. In the figure, components having the same reference numerals as those in FIG. 1 indicate components having the same functions. 2 is an RF receiver, 3
Is an operation unit. The receiving antennas 1a and 1b are provided so that the two antennas are uncorrelated as in the first embodiment. Now, for example, it is assumed that the switching unit 4 is connected to the receiving antenna la. Then, the receiving antenna 1
The received signal received at a is transmitted to the RF receiving unit 2.
The RF receiving unit 2 performs demodulation based on the received signal and sends received data to the arithmetic unit 3. The calculation unit 3 calculates PDOP (positioning accuracy reduction rate due to satellite position) from the received data. Similarly to the first embodiment, when the number of satellites that can be received is less than three, the maximum value is obtained. When the number of satellites that can be captured is three to four, the maximum value of the satellite is obtained. When the number of PDOPs by combination is five or more, the PDOP in the optimum combination of four satellites is calculated from the values and transmitted to the switching control unit 5. Further, based on the data of the satellite group at this time, the current position of the satellite is calculated and output to the display unit 6 to be displayed on the screen. The switching control unit 5 includes:
A predetermined threshold is set in advance. When the value of the PDOP obtained by the arithmetic unit 3 is larger than the threshold value, the switching unit 4 is controlled to switch from the state where the receiving antenna 1a is selected to the state where the receiving antenna 1b is selected.

On the other hand, when it is below the threshold, the receiving antenna 1a currently used is continuously used. By doing so, even in a single reception system including the RF reception unit and the calculation unit, good reception can be performed in an area where reception conditions are poor.

[Third Embodiment] FIG. 3 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a third embodiment. In the figure, the same reference numerals as those in FIG. 1 indicate that they have the same function or equivalent function. Here, the receiving antennas 1a and 1b are provided so as to be uncorrelated with each other as in the first and second embodiments. The received signals are demodulated by the RF receivers 2a and 2b, respectively, and the calculators 3a and 3b calculate PDOP (rate of decrease in positioning accuracy due to satellite position) and calculate their own current position.

In the third embodiment, the switching control unit 5 includes, in addition to the PDOPs from the calculating units 3a and 3b, the RF receiving units 2a and 2b.
The received signal level in 2b is also input. The received signal level is output for each channel. For example, if five satellites are captured by the receiver 2a, the received signal levels for five satellites are input. For these inputs, the value of the PDOP is first referenced. The switching control unit 5 includes a PD
The threshold value for the OP is held. When the threshold value is larger than the threshold value, the PDDP
Switch to the one where is smaller.

On the other hand, when the PDOP (rate of decrease in positioning accuracy due to the satellite position) is smaller than the threshold, the received signal level is referred to. The reception invitation level first takes the minimum value in each system (for example, 5 in the RF receiver 2a).
If a satellite has been captured, the received signal level of the satellite with the lowest received level among the five satellites is determined). Then, by comparing the minimum signal levels of the two systems of the RF receiving unit 2a and the RF receiving unit 2b, the switching unit 4 is switched to the receiving antenna having the higher received signal level. By controlling in this way, the PDO can be used when the satellite capture situation is poor due to shielding.
By performing the switching based on the P and the switching based on the received signal level when the satellite capturing situation is good to some extent, the GPS positioning can be favorably performed in any receiving situation.

[Fourth Embodiment] FIG. 4 is a block diagram showing an electrical configuration of a diversity receiving GPS receiver according to a fourth embodiment. The two receiving antennas 1a and 1b are installed so as to be uncorrelated with each other. Now, it is assumed that the receiving antenna 1a is selected by the switching unit 4, for example. Then, the received signal received by the receiving antenna 1a is input to the RF receiving unit 2. The RF receiving section 2 demodulates the received signal and sends the received signal level of each satellite received at this time to the switching control section 5. The demodulated data is sent to the arithmetic unit 3 where the PDOP (positioning accuracy reduction rate due to the satellite position) is calculated, and its current position is calculated and displayed on the display unit 6.

The switching control unit 5 first refers to the value of PDOP. When the PDOP is larger than the threshold value held in advance, the switching unit 4 is controlled and the receiving antenna 1a is controlled.
Is switched from the selected state to the selected state of the receiving antenna 1b. When PDOP is smaller than the threshold, the received signal level is referred to.

When the received signal level is larger than the threshold value held in advance, the current reception antenna la is held. Conversely, when the received signal level is smaller than the threshold value, the previous switching content is referred to. If the previous switching is based on PDOP, the currently used receiving antenna is retained, and if the switching is performed due to a decrease in the received signal level, the other receiving antenna is switched. Such control is performed, and if the receiving antenna is switched, the switching content is held. By repeating such control, it is possible to select a receiving antenna that always obtains good characteristics and perform positioning calculation. Since DOP is used as a DOP, PDOP (positioning accuracy reduction rate based on satellite position) is used. GDOP (geometric positioning accuracy reduction rate) and TDOP (time-based positioning accuracy reduction rate)
Other DOP values may be used. Further, although the reception system including the RF reception unit and the calculation unit has been described as one system or two systems, it is needless to say that the present invention may be applied to three or more reception systems.

The second and fourth embodiments have a single receiving system composed of the RF receiving unit 2 and the arithmetic unit 3, so that the configuration is simpler than the other third and fourth embodiments, and cost is reduced. But it is advantageous. It is also advantageous in reducing the size.

[0044]

As described above, by using the diversity reception as described above, the satellite is shielded in a city area, a mountain area, or the like, and the GPS is used.
Even in locations where positioning is likely to be difficult, select a reception antenna with good characteristics for reception or a reception antenna that can receive satellites with a small positioning error among multiple reception antennas installed on the moving object Since the GPS radio wave is received by this receiving antenna, the time rate at which reception is not possible can be reduced, and the positioning accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of a diversity reception GPS receiver according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating an electrical configuration of a diversity reception GPS receiver according to a second embodiment.

FIG. 3 is a block diagram illustrating an electrical configuration of a diversity reception GPS receiver according to a third embodiment.

FIG. 4 is a block diagram illustrating an electrical configuration of a diversity reception GPS receiver according to a fourth embodiment.

FIG. 5 is a block diagram showing an electrical configuration of a conventional diversity receiver GPS receiver.

[Explanation of symbols]

 la, lb receiving antenna 2, 2a, 2b RF receiving unit 3, 3a, 3b calculating unit 4, switching unit 5, switching control unit 6, display unit

Continuation of the front page (56) References JP-A-6-265625 (JP, A) JP-A-4-15586 (JP, A) JP-A-62-267677 (JP, A) JP-A-62-267899 (JP) , A) Shigetoshi Higashi, Tomio Yasuda, Basics and Applications of GPS << 2 >> Current Status and Issues of Automotive GPS, Measurement and Control, Japan, Society of Instrument and Control Engineers, Japan, August 10, 1994, Volume 33 No. 8, p. 691-699 Steven M .; Chamberley air, COMBINED GPS / GLONASS NAVIGATION, IEEE National Telesystems Conference, USA, IEEE, 1991, Vol. 205-210 (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S 5/00-5/14 G01C 21/00-21/24 G01C 23/00-25/00 H04B 7/14-7 / 195 H04B 7/22-7/26 H04Q 7/00-7/38

Claims (3)

(57) [Claims] 1. A plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, a switching unit for selectively switching received signals at these receiving antennas, and a demodulation of the received signal selected by the switching unit. RF
A receiving unit, based on demodulated signal data of the RF receiving unit, calculates its own current position, and calculates a positioning accuracy decrease rate (DOP) based on a satellite group signal received by one antenna .
The satellite constellation signal received by another antenna.
The DOP calculated by the calculation unit is compared with the DOP calculated by the calculation unit,
Satellites that provide the best characteristics among tena reception conditions
Switch to select the antenna to receive the group of signals
A switching control unit for switching the parts, a diversity receiver GPS receiver with a display unit for displaying the calculated current position by the computing unit, the switching control unit, positioning accuracy decrease rate (DOP) is given of
When the value is larger than the threshold value, the DOP from the operation unit is referred to.
Switch the switching unit to a smaller DOP
On the other hand, when the rate of decrease in positioning accuracy is smaller than the threshold, RF
Refer to the received signal level from the receiver to receive signal level
The diversity receiving GPS receiver is configured to perform switching to one having a larger value . 2. A plurality of receiving antennas for receiving signals transmitted from a plurality of satellites, a plurality of RF receiving units respectively connected to the receiving antennas and demodulating a received signal, and A plurality of operation units connected to each other for calculating the current position of the mobile station based on the demodulated signal data and calculating a positioning accuracy decrease rate (DOP); and a switching unit for selectively switching operation results of the plurality of operation units. A display unit that displays the current position based on a calculation result of the calculation unit selected by the switching unit; and a positioning accuracy reduction rate for each reception antenna calculated by the calculation unit that exceeds a predetermined threshold. A switching control unit configured to switch the switching unit when it is larger, and to switch the switching unit by referring to the signal level received from the RF receiving unit when the rate of decrease in positioning accuracy is smaller than a predetermined threshold value. Diversity receiver GPS receiver, characterized in that a part. 3. The switching control unit according to claim 1, wherein the positioning accuracy reduction rate (DO)
While when P) is greater than the predetermined threshold to switch the switching unit towards DOP is less with reference to the DOP from the arithmetic unit, from the RF receiver when the positioning accuracy decrease rate is smaller than the threshold diversity receiver GPS receiver according that it is configured to perform switching by referring to the received signal level in the larger received signal level 請 Motomeko 2 you characterized.