JP2001272450A - Current position detecting device using gps - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current position detecting device, using GPS, which can computes the current position with high precision by excluding the influence of what is called a multipath wave. SOLUTION: The radio wave propagation environment at the current position is decided and when a multipath frequency generation area is decided, position measurement computation is carried out by using only receive signals of sufficiently high signal levels from GPS satellites to exclude receive waves due to multipath waves which are generally low in signal levels from the position measurement computation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Pos
The present invention relates to a current position detection device that receives a radio wave from a satellite (hereinafter, referred to as a GPS satellite) in a itioning system to determine a current position.

[0002]

2. Description of the Related Art GPS is a kind of hyperbolic navigation, and it orbits a medium orbit at an altitude of about 20,000 km.
This system receives radio waves from some of the S satellites, analyzes the information contained in the received signal to determine the propagation delay time of the received signal, and calculates the current position of the GPS receiver on the ground.

In general, a current position detecting device using a GPS includes a receiving antenna, a high-frequency signal receiving unit, a plurality of received signal processing units, a positioning calculation unit, and a display unit. That is, radio waves from a plurality of GPS satellites are received by a receiving antenna, amplified, tuned, and detected by a high-frequency signal receiving unit, and then supplied to a plurality of received signal processing units. The reason why there are a plurality of signal processing units is that it is necessary to simultaneously process signals from a plurality of satellites when performing a positioning calculation for calculating the current position based on the principle of hyperbolic navigation, and each signal processing unit has a different satellite. The received signal is demodulated and data received from each satellite is supplied to the positioning calculation unit. The positioning calculation unit determines, based on the received data, the phase of the reference signal inside the device and the phase of the signal received from each satellite, that is, the propagation time of radio waves, and determines the distance (pseudo-distance) between the device and each satellite. Is calculated to calculate the current position of the device.

The current position obtained by the positioning calculation unit is, for example,
The information is combined with the map information stored in a memory formed of a recording medium such as a CD-ROM, and is displayed on a display unit having a display panel such as a liquid crystal display or an EL display.

[0005]

A current position detecting device using GPS receives a radio wave (hereinafter, referred to as a direct wave) directly arriving from a GPS satellite and performs positioning calculation. However, depending on the environment in which the device is placed. May receive not only direct waves, but also radio waves (hereinafter referred to as multipath waves) that reach the device after radio waves from satellites are reflected by obstacles such as buildings and terrain. The multipath wave has the same frequency and the information contained in the radio wave as the direct wave due to the modulation at the time of transmission,
Since the propagation paths of the direct wave and the radio wave are different, the phase is different from that of the direct wave.

Therefore, when the current position detecting device receives a multipath wave and performs positioning calculation using the multipath wave, the result of the early / late phase determination of the phase of the received signal and the reference signal inside the device is different from that of the direct wave. Error occurs in the calculation of the pseudo distance to the satellite.
As a result, the positioning accuracy of the current position is reduced and an incorrect current position is displayed on the device, and the reliability of the current position detection device is lost.

Conventionally, in a current position detecting device using GPS, in order to eliminate the influence of such multipath waves, Japanese Patent Application Laid-Open Nos. 11-83979 and 11-11890.
Various methods have been proposed in Japanese Patent Publication No. 3 and the like. However, since the method is complicated and the positioning calculation is performed on the assumption that a multipath wave is received, an error in the positioning calculation due to the influence of the multipath wave is proposed. Was difficult to reduce.

The present invention has been made to correct such inconvenience, and eliminates the influence of the multipath wave in the positioning calculation by eliminating the received data obtained by demodulating the multipath wave in the positioning calculation. An object of the present invention is to provide a GPS-based current position detecting device that enables positioning.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a plurality of GPS systems.
What is claimed is: 1. A current position detecting device for receiving a radio wave from a satellite to determine a current position, comprising: a plurality of signal processing units for processing a received signal from said GPS satellite; and a signal level mask among output signals from said signal processing unit. Signal selection means for selecting only those having a signal level exceeding the value, positioning calculation means for calculating the current position using the output signal selected by the signal selection means, and determining the radio wave propagation environment around the current position Environment determining means, wherein the signal selecting means increases the signal level mask value when the environment determining means determines that there are many multipath signals around the current position.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a configuration of a current position detecting device using GPS according to the present invention. In FIG. 1, a receiving antenna 17 is an ultra-compact high-gain planar antenna such as a helical antenna or a dielectric antenna, and receives a radio wave transmitted from a GPS satellite.

The high-frequency signal receiving section 16 includes the receiving antenna 1
7 amplifies, tunes, and detects the received radio wave, extracts a desired received signal, and supplies it to each signal processing unit. Each of the signal processing units 15A to 15C demodulates a received signal from a different satellite, and obtains information signal data from each GPS satellite included in the received signal and a level of each received signal. Is supplied to the positioning calculation unit 14. The provision of a plurality of signal processing units is necessary to supply information signal data from a plurality of different satellites to the positioning calculation unit 14 at the same time in order to perform positioning calculation for current position detection based on the principle of hyperbolic navigation. Because there is. Therefore, the number of signal processing units in the present invention is not limited to three,
The positioning accuracy can be improved by increasing the number.

The positioning calculation unit 14 uses the information signal data from a plurality of different satellites supplied from the signal processing units 15A to 15C to calculate a pseudo distance to obtain the distance between the apparatus and each satellite, and to calculate the result. The positioning calculation for calculating the current position of the present apparatus is performed using the apparatus. The multipath wave determination unit 18 uses the output signals of the signal processing units 15A to 15C to multiply a currently received radio wave from a GPS satellite by a conventionally known multipath wave detection method. Whether or not a path wave is included is detected, and a radio wave propagation environment around the current position of the device is determined.

The database attribute judging section 19 is a database used in a navigation system using the current position detecting device. For example, the map attribute information is stored in a storage medium such as a CD-ROM. The attribute is also stored, and the radio wave propagation environment around the current position of the apparatus is determined using the attribute of the database.

The mobile phone base station attribute determining unit 20 determines a radio wave propagation environment around the apparatus using a mobile phone terminal (not shown) provided in the apparatus. Specifically, when the mobile phone terminal moves, it utilizes the communication for location registration with the nearest mobile phone base station, and determines the radio wave propagation environment around the current position of the device from the attributes of the base station. I do. In the present embodiment, the determination units 18 to 20 which are the determination means for determining the radio wave propagation environment around the current position do not necessarily need to include all of them. It is possible to select the judging means to be provided in consideration of the above. That is, if it is intended to eliminate the influence of multipath wave reception as much as possible and to perform high-precision positioning calculation, it should have all of the determination means. At least one of the determination means may be selected and provided.

The system control unit 10 is mainly composed of a microcomputer and controls the operation of the entire apparatus. For example, the system control unit 10 executes a main routine stored in the memory unit 11 step by step in synchronization with a built-in clock. I do. The memory unit 11 has a normal ROM (Read Only Memory).
y) and RAM (Random Access Memory), when displaying the current position calculated by the positioning calculation, and when determining the radio wave propagation environment around the current position by the database attribute determination unit 19, such as map information. A drive-type recording medium such as a CD-ROM storing a database is included.

The display unit 12 and the operation unit 13 are provided on, for example, a console panel in a vehicle cabin. The display unit 12 is a liquid crystal display or a light emitting diode for displaying map information including the state of the apparatus and the current position. Consisting of
The operation unit 13 includes a keyboard or a group of switches for inputting various operation commands to the device. The operation process in the positioning mode of the device shown in FIG. 1 will be described below.

The system control unit 10 interrupts a positioning mode operation processing subroutine shown in FIG. 2 into a main routine that is always executed in synchronization with a built-in clock, for example, and executes it at predetermined intervals. System control unit 10
According to step 10 of the subroutine, the GPS
Each signal processing unit 15 performs processing of a signal received from a satellite.
A to 15C. The GPS signal reception processing is a fusion of not only software processing but also processing operations of each hardware device in the apparatus, and the outline thereof is as described below.

That is, a radio wave transmitted from a GPS satellite is received by an antenna 17, amplified, tuned, and detected by a high-frequency signal receiving unit 16, and then transmitted to each signal processing unit 15 A.
To 15C. GPS satellites are equipped with a cesium atomic clock, and each satellite creates transmission data by encoding its time information and orbital position information with a special code. Then, PSK or QPSK is added to the transmission data.
After performing narrow-band digital modulation such as, and further performing spread modulation on the modulation output using a different PN code (Pseudorandom Noise Code: pseudo-white noise code) for each satellite, and then using a carrier of 1575.42 MHz Send.

For this reason, each of the signal processing units 15A to 15C receiving the supply of the detection signal from the high-frequency signal receiving unit 16
Despreads the detection signal using a PN code corresponding to each satellite and demodulates transmission data from each satellite.
In terms of time series, one signal processing unit demodulates a signal received from one satellite at one time. Therefore, the apparatus configuration shown in FIG. 1 can simultaneously demodulate received signals from three different satellites, and each signal processing unit supplies these demodulated data to the positioning calculation unit 14. Further, the signal processing units 15A to 15C also supply the value of the signal level of the received signal to the positioning calculation unit 14 as one of the information received from each satellite.

The above is the GPS in step 10 of FIG.
It is an outline of a signal reception process. On the other hand, the demodulated data of the GPS reception signals from the signal processing units 15A to 15C are also supplied to the multipath wave determination unit 18. Multipath wave judgment unit 1
Reference numeral 8 uses the fact that the frequency of the actual received radio wave from the satellite changes due to the Doppler effect due to the movement of the GPS satellite or the apparatus, and determines whether the received radio wave includes a multipath wave.

That is, the multipath wave judgment unit 18 receives only direct waves from GPS satellites by using the moving speed of the present device obtained by dead reckoning means (not shown) provided in a vehicle equipped with the present device. Then, the Doppler shift amount of the reception frequency when it is assumed to be calculated is calculated. Next, the signal processing unit 1
The Doppler shift amount of the reception frequency of the radio wave actually received is calculated based on the reception signal demodulation data from each satellite supplied from 5A to 15C. The judging unit 18 compares the two, and if the difference is large, judges that the multipath wave is included in the received radio wave, and determines that the multipath wave is present in the received radio wave by the judgment flag ( (Not shown)
Is set.

If the flag has been set, the system controller 10 proceeds to step 15; otherwise, the system controller 10 proceeds to step 12 (step 11). In step 12, the database attribute determining unit 19
Using the GPS reception data supplied from the signal processing units 15A to 15C, based on the current position of the apparatus calculated by the positioning calculation unit 14, a database relating to map information stored in the CD-ROM of the memory unit 11 is searched. . Thereby, the database attribute determining unit 19 determines whether or not the current position is registered in the map information database as a so-called multipath frequent area having a topographical attribute where multipath waves are likely to occur.

It should be noted that the topographical attribute in which multipath waves are likely to be generated can be theoretically inferred from the existence of mountains, hills and large-scale buildings, or the results of radio wave propagation measurement tests actually performed. This can be registered in advance in the database relating to the map information in the memory unit 11. If the current position of the present apparatus has been registered in the map information database, the database attribute determining unit 19 determines that the vicinity of the current position is a multipath frequent area, and the presence of the multipath wave is possible. Set a flag that indicates gender.

If the flag has been set, the system control unit 10 proceeds to step 15, and if not, proceeds to step 13. Immediately after the operation of the device starts, or immediately after a vehicle equipped with the device enters a multipath wave frequent area, a multipath wave reception elimination function to be described later sufficiently functions in the positioning calculation of the positioning calculation unit 14. You may not. In such a case, the positioning calculation unit 14
The calculated current position may have been calculated using a received radio wave including a multipath wave, and it cannot be denied that the positioning accuracy of the current position is reduced. However, in the database relating to the map information, the multipath frequent areas are registered as areas having a certain size. For this reason, even if the accuracy of the current position calculation by the positioning calculation unit 14 is slightly lowered, there is no practical problem in determining whether or not the present device has entered the multipath frequent area.

In step 13, it is determined whether or not the vicinity of the current position of the apparatus is a multipath frequent area by utilizing the fact that the mobile phone terminal automatically communicates with the nearest mobile phone base station for location registration. . In other words, when the present device moves within the service area of the mobile phone system, the mobile phone terminal (not shown) attached to the device moves for a predetermined distance or every time a predetermined time elapses. Automatically communicates with the mobile phone base station for location registration. On this occasion,
The mobile phone terminal supplies data of the base station with which the communication has been performed to the mobile phone base station attribute determining unit 20.

If the base station is a station located in an urban area, the determination unit 20 determines that the radio wave propagation environment around the current position of the apparatus is a frequent multipath area, and a flag (see FIG. (Not shown). If the flag is set, the system control unit 10 proceeds to step 1
The process proceeds to step S5, and if not set, proceeds to step S14.

Even if the mobile phone base station is located in an urban area and the surrounding area is a frequent multipath area due to the influence of an urban building, it is strictly speaking that it is a situation around the base station and a situation immediately adjacent to the present apparatus. It may not be possible. However, in general, a cellular phone system employs a small zone method in which a service area of a base station is divided by a cell having a diameter of several km or less, so that a state of a space having a certain size such as a radio wave propagation environment is grasped. In this case, there is no problem in approximating the situation in the vicinity of the apparatus with the situation in the vicinity of the base station.

Since the judgments from step 11 to step 13 are for obtaining the logical sum regarding the existence of the multipath wave, they need not always be performed in the order shown in FIG. 2 and can be performed in any order. When the present apparatus does not include all of the determination units 18 to 20, only the processing steps for the currently provided determination unit need be performed. If the flag (not shown) indicating the possibility of the existence of the multipath wave has not been set in all the determinations in the above processing steps, the system control unit 10 causes the positioning calculation unit 14 to perform the subsequent calculation processing. _PTH1 [dBm], which is a normal signal level mask value, is set as the threshold value of the received signal level used at this time (step 14).

On the other hand, as is apparent from the above processing flowchart, if the flag indicating the presence of the multipath wave is set in any of the determinations in steps 11 to 13, the system control unit 10 proceeds to step 1
In step 5, _PTH2 [dBm], which is a signal level mask value for a multipath frequent area, is set as the reception signal level threshold. In the present invention, P
_TH1 [dBm] <P _TH2 [dBm].

After setting the reception signal level mask value in step 14 or step 15, the system control unit 10 instructs the positioning calculation unit 14 to perform pseudo distance calculation or positioning calculation, and performs positioning calculation. The unit 14 includes the signal processing unit 1
The subsequent calculation process is started using the GPS reception data supplied from 5A to 15C (step 16). The positioning calculation unit 14 does not use the received data from all the satellites when performing the calculation process, but selects only the signal whose signal level exceeds the signal level mask value, and receives the signal. Perform calculations using the data. This is because the weaker the signal level of the received signal, the higher the possibility that an error has occurred in the data due to disturbances such as noise and fading, and the signal reception may be interrupted frequently. This is because the calculation accuracy decreases when the positioning calculation is performed.

That is, in a normal radio wave propagation area, calculation is performed using only received signal data having a level _{exceeding the} signal level mask value P _TH1 [dBm], and in a multi-path frequent area, the signal level mask value P _TH2 is calculated. The calculation is performed using only the received signal data of the level exceeding [dBm]. As described above, the signal level mask value has a relationship of P _TH1 [dBm] <P _TH2 [dBm]. Therefore, the positioning calculation unit 14 performs the positioning calculation using only the received signal having a higher signal level in the multipath frequent area as compared with the normal radio wave propagation area.

By the way, as shown in FIG. 3, the reception signal level of the direct wave with respect to the reception radio wave from the GPS satellite is P _D [dB].
m], when the reception signal level of the multipath waves and P _M [dBm], in general, P _D> P _M becomes relation is established. This is because in the case of a multipath wave, when a radio wave from a satellite is reflected on an obstacle such as a building or a hill, attenuation occurs due to absorption or scattering of the radio wave. That is, a multipath wave generated in a multipath frequent area is compared with a direct wave propagating along the same propagation path from a GPS satellite to the vicinity of the present apparatus.
The signal level value will always be low.

Therefore, as described above, the signal level mask value P _TH2 [dBm] in the multipath frequent area can be set higher than the signal level mask value P _TH1 [dBm] in the normal radio wave propagation area. For example, positioning calculation can be performed even in a multipath frequent area by eliminating multipath waves.
Also, since radio waves from GPS satellites at a low elevation angle as viewed from this device have a longer radio wave propagation distance than radio waves from satellites at a high elevation angle, even if they arrive directly at this device, their signal The level drops. Therefore, in the present invention, the signal level mask value P
_TH1 [dBm] is set lower than the signal level mask value P _TH2 [dBm] in the area where frequent multipaths occur. In areas where the radio wave propagation environment is favorable, radio waves from GPS satellites at low elevation angles can be effectively used for positioning calculation. Can be used.

[0034]

As described above in detail, according to the present invention, the GP
In the current position detecting device using the S satellite, the effect of so-called multipath waves can be effectively eliminated, and extremely high-accuracy positioning calculation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a current position detection device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a positioning mode operation of a current position in the apparatus of FIG. 1;

FIG. 3 is a schematic diagram showing a relationship between signal levels of a direct wave from a GPS satellite and a multipath wave.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 System control part 11 Memory part 12 Display part 13 Operation part 14 Positioning calculation part 15A, 15B, 15C Signal processing part 16 High frequency signal receiving part 17 Receiving antenna 18 Multipath wave judgment part 19 Database attribute judgment part 20 Cell phone base station attribute Judgment unit

Continued on the front page (72) Inventor Isao Endo 25-1, Nishimachi, Yamada-ji, Kawagoe-shi, Saitama Prefecture Pioneer Corporation Inside the Kawagoe Plant (72) Inventor Toshiya Ozaki ▼ 25-1, Nishimachi, Yamada-ji, Kawagoe-shi, Saitama Pioneer F-term in Kawagoe Factory Co., Ltd. (reference) 2F029 AA02 AB07 AC02 AC14 AC20 AD01 5H180 AA01 BB05 BB13 CC12 EE02 FF05 FF22 FF27 FF40 5J062 AA02 AA11 BB01 CC07 DD02 DD13 DD15 EE01 EE03 FF01 FF04 GG02 EE02 9

Claims (3)

[Claims] 1. A current position detecting device for receiving a radio wave from a plurality of GPS satellites to obtain a current position, comprising: a plurality of signal processing units for processing signals received from the GPS satellites; Signal selection means for selecting only those signal levels that exceed the signal level mask value among the output signals of the above, positioning calculation means for calculating the current position using the output signal selected by the signal selection means, current position Environment determining means for determining a surrounding radio wave propagation environment, wherein the signal selecting means increases the signal level mask value when the environment determining means determines that there are many multipath signals around a current position. A current position detecting device, characterized in that: 2. The environment determining means holds map information data accompanied by multipath signal frequently occurring area information, and compares the map information data with the current position to determine the radio wave propagation environment. Determining means, and a second determining means for receiving the signal from the mobile phone base station to determine the radio wave propagation environment based on the attribute of the base station,
And a third determination unit that determines the radio wave propagation environment by detecting a multipath signal using output signals from the plurality of signal processing units. 2. The current position detecting device according to 1. 3. The environment determination means according to claim 1, wherein
3. The current position detecting device according to claim 2, further comprising at least two of the determination means, and determining the radio wave propagation environment from a logical sum of the two determination results.