JPH10253735A - Positioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the positioning accuracy significantly by eliminating the effect of multipath. SOLUTION: A GPS satellite delivers a right circularly polarized wave of carrier frequency and the polarizing direction of an antenna is turned by an antenna polarizing direction turning unit 3. Since a direct wave and the reflected wave of a left circularly polarized wave are subjected to frequency shift in different directions, a capturing/tracking frequency range is set around the shifting position of direct wave at a capturing/tracking frequency range converting section 24 such that a shifted wave deviates from that range thus preventing erroneous capturing/tracking of reflected wave and enhancing the positioning accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device using a signal from a GPS satellite, and more particularly to a receiving unit thereof.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a schematic configuration of a positioning device that performs a single positioning by a conventional pseudorange (correction) method.
1 indicates an antenna, and 2 indicates a receiving device. Radio waves from GPS satellites are received by the antenna 1 and transmitted to the receiving device 2 as signals. In the receiving device 2, the GPS receiver 21 receives a signal from the antenna 1, captures and tracks a carrier frequency using information such as almanac stored in the memory 23, and demodulates navigation data. Position calculation unit 22
And the position calculator 22 measures the current position of the antenna 1.

A major factor that deteriorates the positioning accuracy in such a positioning device is multipath. As is well known, multipath is a phenomenon in which, in addition to radio waves received directly from a satellite via an antenna, reflected waves reflected by buildings on the surface of the earth are received simultaneously with the direct waves. If it is strong, for example, it is difficult to distinguish the true code of the direct wave from that of the reflected wave, which leads to a pseudorange measurement error. Note that multipath affects the accuracy of positioning devices that use all types of GPS, and cannot be ignored even in single positioning.However, there is a particular problem in DGPS (differentialGPS) with high positioning accuracy and carrier phase DGPS that performs interference positioning. Become. For the method of obtaining a position using such GPS and the influence of multipath, for example, "GPS-accurate positioning system by satellite" and "GP
Basics of S Survey ".

Therefore, as a method of removing this multipath, an antenna having reduced sensitivity in the horizontal direction is conventionally used. A method has been considered in which a radio wave of a GPS satellite is right circularly polarized wave and a choke ring type antenna having high reception sensitivity for right circularly polarized wave is used.

[0005]

As described above, the conventional G
In a positioning device using a PS, the positioning accuracy deteriorates due to a measurement error caused by multipath. For example, in a pseudo-range (correction) DGPS, the positioning accuracy can be reduced to within 1 meter. Actually, the positioning accuracy is about several meters due to the influence of multipath. Also, when using an antenna with reduced horizontal sensitivity,
The sensitivity of receiving from low elevation satellites is sacrificed and the effective use of satellites is limited. Further, the choke ring type antenna is large and heavy in mechanical structure and expensive, so that it is currently used only at a reference station (known station) that provides a DGPS service and cannot be used for a small mobile station. Further, similarly, there is a problem that the reception sensitivity of radio waves from a low elevation angle is weak, and the effective use of satellites is limited.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a positioning device in which the influence of multipath is removed and positioning accuracy is greatly improved.

[0007]

SUMMARY OF THE INVENTION A positioning device according to the present invention comprises an antenna for receiving radio waves from GPS satellites, a polarization direction rotating device for rotating the polarization direction of the radio waves received by the antenna, A receiving device for processing and positioning the received signal, provided in this receiving device, the rotation information from the polarization direction rotation device, and the direct wave from the GPS satellites due to the rotation of the antenna in the polarization direction due to the almanac and the like. Calculate the shifted frequency position and capture around this position.
A tracking / frequency range setting means for setting a tracking frequency range is provided. The carrier frequency from the GPS satellite is right circular polarization, and the frequency shifts in a direction different from the direct wave and the reflected wave (reflected wave obtained by reflecting the direct wave once) by rotating the polarization direction of the antenna. Therefore, if the capture and tracking frequency range is set around the position where the direct wave shifts, the shifted reflected wave deviates from the capture and tracking frequency range, so that the reflected wave is not erroneously captured and tracked.

The antenna, which is disposed at a known point,
A known station device comprising a polarization direction rotating device and a receiving device provided with acquisition / tracking frequency range setting means, a reception device provided with the antenna, the polarization direction rotating device, and a capturing / tracking frequency range setting device at a positioning point. Equipped with a positioning station device composed of devices,
It is characterized in that the positioning station device performs positioning by DGPS using information transmitted from the known station device. D
Even when a GPS is configured, if both the known station device and the positioning station device are configured according to the present invention, the pseudorange correction information and the carrier frequency phase information obtained from the known station are also accurate, and the pseudorange (correction) method is used. Carrier phas in DGPS
e DGPS can also greatly improve the positioning accuracy.

Further, the polarization direction rotating device is characterized in that the polarization direction rotating device is configured to electronically rotate the polarization direction of a radio wave received by the antenna. By rotating the polarization direction electronically, the antenna and the polarization direction rotating device can be configured to be lightweight, small, and inexpensive, and can be easily implemented in mobile stations and the like in car navigation.

Further, the polarization direction rotating device is characterized in that it comprises a device for mechanically rotating the polarization direction of the radio wave received by the antenna. Depending on the type of the antenna, if it is difficult to rotate the polarization direction electronically, it can be similarly implemented as a device that rotates mechanically.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing an embodiment of the device configuration of the present invention, in which 1 is an antenna, 2 is a receiving device, and 3 is an antenna polarization direction rotating device. In the receiving device 2, reference numeral 21 denotes a GPS receiver,
Reference numeral 22 denotes a position calculation unit, 23 denotes a memory, and 24 denotes an acquisition / tracking frequency range conversion unit.

In the multipath, which is a cause of deterioration of the positioning accuracy of the GPS positioning apparatus, the direct wave and the reflected wave are received at the same time, and the reflected wave disturbs the waveform of the direct wave. It is sufficient to separate the direct wave from the reflected wave and take out only the direct wave. For this purpose, the difference between the properties of the direct wave and the reflected wave is used.

That is, the radio waves from the GPS satellites are right circularly polarized waves. The right circular polarization is to be left circular polarization once reflected. Normally, the intensity of the received electric field rapidly decreases with each reflection, so the problem with multipath is that the left circular polarization is reflected once. Therefore, in order to remove the influence of the multipath, the right circular polarization and the left circular polarization may be separated to capture and track only the right circular polarization. For this reason, in the present invention, the right circular polarization and the left circular polarization are shifted as much as possible in frequency, and the almanac stored in the memory of the normal receiver is usually used.
By setting the acquisition and tracking frequency ranges at positions where the right circular polarization is predicted to shift in frequency using (almanac) or the like, it is possible to adopt a configuration in which only the direct wave that is the right circular polarization is taken in as a signal.

For example, in the case of a modern antenna, 1958, antenna (lower volume), pp. 542 to 566 (JDKraus), in the case of an antenna receiving circularly polarized waves, when the polarization direction of the antenna is rotated,
It describes that the right circular polarization and the left circular polarization shift in frequency in different directions by the rotation frequency of the antenna. Mechanical rotation of the polarization direction can be easily done in all such antennas, and by electronically shifting the reception strength between vertical and horizontal polarization, many of these types of antennas can be used. The antenna can easily rotate the polarization direction electronically. Therefore, in the present embodiment, the antenna polarization direction rotating device 3 is provided, and the polarization direction of the antenna 1 is mechanically or electronically rotated to shift the frequencies of the right circular polarization and the left circular polarization in opposite directions. And separate.

On the other hand, in the receiving device, general orbit information of all satellites called almanac is usually stored in a memory 23 in order to quickly search for a receiving carrier frequency when capturing a GPS satellite signal. Receiver (Fig. 3
2)), based on this information, the approximate position of the antenna, and the approximate current time, the received carrier frequency is estimated, the estimated information 200 is input to the GPS receiver 21, and the search is performed around that frequency. The way has been taken.

In this embodiment, the estimated information 20
0 is input to the acquisition / tracking frequency range conversion unit 24, corrected by the antenna rotation direction and rotation frequency information 300 input from the antenna polarization direction rotation device 3, and corrected by GPS.
The GPS receiver 21 is provided with an acquisition / tracking frequency range setting means for searching around the frequency position where the direct wave is shifted and inputted to the receiver 21. Therefore, if the rotation frequency in the polarization direction is sufficiently increased, the frequency difference between the direct wave and the reflected wave can be increased, and the search is performed centering on the frequency range in which only the direct wave is shifted by the corrected information 201. It is possible to easily capture only the direct wave without erroneously capturing the reflected wave whose frequency deviates greatly.

In tracking, a bandwidth for tracking a received carrier frequency is usually designed to be several tens Hz or less. Therefore, by setting a sufficiently large rotation frequency in the antenna polarization direction, there is no erroneous tracking of the reflected wave. With the configuration and operation described above, the positioning device according to the present embodiment separates and removes reflected waves included in multipath, and enables highly accurate positioning using only direct waves.

FIG. 2 is a block diagram schematically showing the configuration of an apparatus according to another embodiment of the present invention.
Reference numerals a and 3a denote antennas, receivers, antenna polarization direction rotating devices, and antennas installed at known points A as known station devices, respectively.
Reference numerals b, 2b, and 3b denote an antenna, a receiving device, and an antenna polarization direction rotating device serving as a positioning station device of the positioning point B, respectively, and the antenna 1, the receiving device 2, and the antenna polarization direction rotating device 3 shown in FIG. It has a similar configuration. 4a indicates a known station information transmitter, and 4b indicates a known station information receiver.

In the above-described embodiment, an apparatus that performs single positioning by the pseudorange (correction) method has been described. However, a known station apparatus installed at a known point A has the same apparatus configuration as the configuration described in the above-described embodiment. By doing so, it is possible to separate and remove the reflected waves included in the multipath, transmit high-precision correction information using only direct waves to the positioning station apparatus, and perform high-precision positioning using DGPS. Note that D in this case
It is needless to say that the GPS may be a pseudo-range (correction) system, or may be a carrierphase DGPS that transmits the phase information of the carrier frequency from which the influence of the multipath has been removed and performs the interference positioning. DG
The positioning error of the PS is usually designed so that an error due to factors other than multipath such as thermal noise of a receiver is several tens of centimeters or less. If the configuration is such that the reflected wave included is separated / removed and the position is corrected using only the direct wave and the correction value is transmitted, high-precision correction can be performed, and positioning accuracy of 1 meter or less can be expected.

[0020]

According to the positioning apparatus of the present invention configured as described above, the influence of multipath can be eliminated and the positioning accuracy can be greatly improved. In particular, in the case where the polarization direction of the antenna is electronically rotated, the antenna can be made smaller and lighter in terms of mechanical structure, and can be realized at a lower price without sacrificing the receiving sensitivity from the low-elevation angle satellite. In the case of configuring the DGPS, even if the pseudo-range (correction) method is used, a positioning accuracy of 1 meter or less can be expected, and a car navigation apparatus or the like configured by a DGPS mobile station using a DGPS service that has recently begun. Has the effect of being particularly effective.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating an outline of a device configuration according to another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional positioning device of this type.

[Explanation of symbols]

 1, 1a, 1b Antenna 2, 2a, 2b Receiving device 3, 3a, 3b Antenna polarization direction rotation device 4a Known station information transmitter 4b Known station information receiver 21 GPS receiver 22 Position calculation unit 23 Memory 24 Capture / tracking Frequency range converter

Claims (4)

[Claims] An antenna for receiving a radio wave from a GPS satellite, a polarization direction rotating device for rotating a polarization direction of a radio wave received by the antenna, a receiving device for processing a signal received by the antenna and performing positioning. Provided in the receiving device, by using the rotation information from the polarization direction rotation device, almanac (almanac), etc., calculate the frequency position where the direct wave from the GPS satellite is shifted by the rotation of the antenna in the polarization direction. A positioning device comprising a capture / tracking frequency range setting means for setting a capturing / tracking frequency range centering on a position. 2. A known station device which is provided at a known point and comprises a receiving device provided with said antenna, a polarization direction rotating device, and an acquisition / tracking frequency range setting means. A positioning station device comprising a wave direction rotating device and a receiving device provided with an acquisition / tracking frequency range setting means is provided. The positioning station device uses DGPS (differential GPS) by using information transmitted from the known station device. A positioning device that performs positioning. 3. The polarization direction rotating device according to claim 1, wherein the polarization direction rotating device is configured to electronically rotate a polarization direction of a radio wave received by the antenna. Positioning device. 4. The apparatus according to claim 1, wherein the polarization direction rotating device is configured to mechanically rotate the polarization direction of a radio wave received by the antenna. Positioning device.