JP4177726B2 - Positioning system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positioning system such as a GPS (Global Positioning System), and a positioning signal transmission device and a positioning device used in this system.
[0002]
[Prior art]
In the existing GPS, positioning signals on which positioning data is superimposed include L1 wave band (center frequency 1575.42 MHz, bands 2.046 MHz and 20.46 MHz) and L2 wave band (center frequency 1227.6 MHz, band 20.46 MHz). Is used. At present, only the L1 wave band is open to the private sector.
[0003]
At the present time, an SOC (Single Offset Carrier) method is adopted as a modulation method for each waveband. Similarly, the pseudolite (Pseudo-Lite) as a GPS transmitter provided on the ground side also adopts the L1 wave band and the SOC system.
[0004]
By the way, a plan for promoting the modernization of GPS was proposed in the United States, which manages GPS satellites. Among them, it is planned to open not only the L1 frequency but also the L2 frequency to the private sector in the future. Furthermore, an L5 wave band (center frequency 1176.45 MHz, band 24 MHz) is newly provided, and it is being considered to open it to the private sector. In response to this, it is expected that a BOC (Binary Offset Carrier) method with higher data transmission efficiency will be adopted in the future in addition to the SOC method in the modulation method. The Gallieo satellite under consideration in Europe will adopt the BOC modulation scheme.
[0005]
Non-Patent Documents 1 and 2 below disclose related technologies. Non-Patent Document 1 discloses details regarding the SOC modulation method and the BOC modulation method. Non-Patent Document 2 discloses a configuration example of an apparatus that receives a signal of each of the above modulation schemes.
[0006]
[Non-Patent Document 1]
John W. Betz: "The Offset Carrier Modulation for GPS Modernization," ION-GPS99, Jan 1999.
[0007]
[Non-Patent Document 2]
Capt.Brian C. Barker, et.al: "Overview of the GPS M Code Signal," IOG-GPS2000, May 2000.
[0008]
[Problems to be solved by the invention]
As described above, it is considered to promote the modernization of GPS, and it is expected that the frequency band that can be used in the positioning signal and the modulation method will be expanded. A positioning signal transmitter and receiver that can be used in such future systems are not yet known. Furthermore, there is a possibility that positioning accuracy can be improved by combining a plurality of frequency bands and modulation methods, and a more reliable system can be provided.
The present invention has been made under the circumstances described above, and an object thereof is to provide a positioning system that can effectively use a plurality of frequency bands and has improved reliability.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a positioning system according to the present invention comprises a plurality of positioning signal transmitting devices that radiate positioning signals, and a positioning device that receives the positioning signals and obtains position information,
Each of the plurality of positioning signal transmitters modulates an SOC ( Single Offset Carrier ) with at least one of the L1, L2, and L5 wavebands using at least one of a C / A code and a P code. A positioning signal generating means for generating a maximum of 12 types of positioning signals by modulating with at least one of a modulation system and a BOC ( Binary Offset Carrier ) modulation system, and a positioning signal generated by the positioning signal generating means in space The positioning device includes: a receiving unit that receives each of the positioning signals individually radiated from the plurality of positioning signal transmitting devices; and a receiving unit that receives each positioning signal received by the receiving unit. Monitoring means for monitoring each state; and switching means for selectively switching and outputting a positioning signal whose reception state exceeds a certain threshold level; Positioning means for obtaining position information of the positioning device from the positioning signal output from the switching means, at least one of the plurality of positioning signal transmission devices being arranged in the troposphere, and another positioning signal transmission device Is characterized by a higher altitude than the ionosphere .
[0010]
By taking such means, not only the existing positioning signals in the L1 and L2 wavebands but also the positioning signals including the L5 waveband can be used. Furthermore, a positioning signal can be generated not only by SOC modulation but also by BOC modulation. Two types of codes, C / A code and P code, are known, and a maximum of 12 types of positioning signals can be used by combining three bands, two types of code, and two types of modulation. System can be operated.
[0011]
On the positioning device side, position information is calculated from each of these 12 types of positioning signals. For example, only a positioning signal having a good reception state is selectively used in a building shadow or in a place where conditions are not good. By doing so, it becomes possible to increase system tolerance. For this reason, it is possible to effectively use a plurality of frequency bands and to perform positioning with high reliability.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a system configuration diagram showing an embodiment of a positioning system according to the present invention. This system includes a GPS satellite 100, a pseudolite transmitter (PL transmitter) 200, and a receiver 300. The GPS satellite 100 and the PL transmitter 200 include a positioning signal in the L1 band (hereinafter referred to as L1 signal), a positioning signal in the L2 band (hereinafter referred to as L2 signal), and a positioning signal in the L5 band (hereinafter referred to as L5 signal). Send). The receiver 300 receives the L1 signal, the L2 signal, and the L5 signal, and calculates its own position information. In the present embodiment, the position of the PL transmitter 200 is fixed in the troposphere including the ground, and the installation position of the transmission antenna 201 is accurately measured in advance.
[0013]
The L1, L2 and L5 signals transmitted from the GPS satellite 100 and the PL transmitter 200 are modulated by the C / A code and the P code, respectively. As the modulation method, an SOC modulation method and a BOC modulation method are adopted. As a result, positioning signals that can be used in the present system can be provided with a maximum of 12 types from combinations of bands, codes, and modulation schemes.
[0014]
FIG. 2 is a block diagram showing an embodiment of the PL transmitter 200 of FIG. The PL transmitter 200 shown in FIG. 2 mixes the transmission modules 1 to 5 that generate different positioning signals, and the positioning signals generated by the transmission modules 1 to 5 and radiates them into the space via the antenna 201. And a mixer 6.
[0015]
The transmission module 1 includes signal generation units 1a and 1b. The signal generator 1a generates a first positioning signal by modulating a carrier wave in the L1 wave band with a C / A code using the SOC modulation method. The signal generation unit 1b generates a second positioning signal by modulating a carrier wave in the L1 wave band with a P code using an SOC modulation method. The first and second positioning signals are mixed by the mixer 1 c and radiated from the antenna 201 to the space via the mixer 6.
[0016]
The transmission module 2 includes signal generation units 2a and 2b. The signal generation unit 2a generates a third positioning signal by modulating a carrier wave in the L1 wave band with a C / A code using a BOC modulation method. The signal generation unit 2b generates a fourth positioning signal by modulating a carrier wave in the L1 wave band using a P code with a BOC modulation method. The third and fourth positioning signals are mixed by the mixer 2 c and radiated from the antenna 201 to the space via the mixer 6.
[0017]
The transmission module 3 includes signal generation units 3a and 3b. The signal generation unit 3a generates a fifth positioning signal by modulating a carrier wave in the L2 wave band with a C / A code using the SOC modulation method. The signal generation unit 3b generates a sixth positioning signal by modulating a carrier wave in the L2 waveband using the P code with the SOC modulation method. The fifth and sixth positioning signals are mixed by the mixer 3 c and radiated from the antenna 201 to the space via the mixer 6.
[0018]
The transmission module 4 includes signal generation units 4a and 4b. The signal generation unit 4a generates a seventh positioning signal by modulating a carrier wave in the L2 waveband with a C / A code using the BOC modulation method. The signal generation unit 4b generates an eighth positioning signal by modulating a carrier wave in the L2 waveband using a P code with a BOC modulation method. The seventh and eighth positioning signals are mixed by the mixer 4 c and radiated from the antenna 201 to the space via the mixer 6.
[0019]
The transmission module 5 includes signal generation units 5a and 5b. The signal generation unit 5a modulates the L5 waveband carrier wave with the C / A code and the P code by the SOC modulation method, and generates the ninth and tenth positioning signals. The signal generation unit 5b modulates a carrier wave in the L5 wave band with a C / A code and a P code according to the BOC modulation method, and generates eleventh and twelfth positioning signals. The ninth to twelfth positioning signals are mixed by the mixer 5 c and radiated from the antenna 201 to the space via the mixer 6.
[0020]
FIG. 3 is a block diagram showing a more detailed configuration of the signal generators 1a, 1b, 3a, 3b, and 5a of FIG. That is, FIG. 3 shows a configuration example of a signal generation unit that generates a positioning signal based on the SOC modulation method. In FIG. 3, for example, a 1.023 MHz clock corresponding to the L1 waveband is input to the frequency divider 11 and the multipliers 21 and 31, respectively. The frequency divider 11 divides the clock to the data message rate and supplies it to the data message generator 12. The data message generation unit 12 generates a data message including positioning data such as ephemeris, almanac data, and time data.
[0021]
The multiplier 21 multiplies the clock to the code rate fc and supplies it to the spreading code generator 22. The spreading code generator 22 generates a C / A or P spreading code corresponding to the code rate fc. This spreading code is multiplied by the data message by the mixer 41 to generate a spreading message. This spread message has a biphase waveform. The spread message having this waveform is shaped through the low-pass filter 50, and an SOC signal having a peak at the center of the band is generated. Note that f in the characteristics of the low-pass filter 50 is a carrier frequency, and B is a passband bandwidth.
[0022]
The multiplier 31 drives the oscillator 32 by multiplying the clock to the subcarrier frequency fs. The oscillator 32 generates a sine wave having a subcarrier frequency fs. This sine wave is multiplied by the SOC signal by the mixer 40, thereby generating a baseband LOC signal.
[0023]
FIG. 4 is a block diagram showing a more detailed configuration of the signal generators 2a, 2b, 4a, 4b, and 5b of FIG. 4 that are the same as those in FIG. 3 are denoted by the same reference numerals, and only different parts will be described here. That is, FIG. 4 shows a configuration example of a signal generation unit that generates a positioning signal based on the BOC modulation method. In FIG. 4, the spread message of the biphase waveform generated by the mixer 41 is supplied to the mixer 40 as it is and is multiplied by the sine wave of the subcarrier frequency fs. As a result, a baseband BOC signal having peaks at both ends of the band is generated. The baseband SOC signal and BOC signal generated in FIGS. 3 and 4 are radiated to space via a high-frequency circuit, a transmission amplifier, an RF filter, and the like (not shown).
[0024]
FIG. 5 is a block diagram showing a system code and SOC modulation system based on ICD-GPS-200C. In FIG. 5, the reset command generation unit 62 generates a reset command in accordance with the given remote command, and provides it to the Z counter 61 and the epoch reset unit 63. The epoch reset unit 63 provides reset information to the code generation units 65 and 68. Each of the code generators 65 and 68 generates a spread code by the method shown in FIGS. 3 and 4 based on the clock supplied from the oscillator 72.
[0025]
The spread code generated by the code generation unit 65 is given to the epoch detection unit 64 to detect epoch information. The detected epoch is given to the Z counter 61, and the Z-count value is detected. The detected epoch is given to the epoch reset unit 69 and reset.
[0026]
The spread code generated by the code generation unit 68 is selected by the code selection unit 67, added by the adder 66 with the spread code generated by the code generation unit 65, and provided to the clock recovery unit 71. The clock recovery unit 71 recovers the clock based on the clock supplied from the oscillator 72. The regenerated clock is supplied to the adder 75.
[0027]
The frequency divider 70 divides the clock supplied from the oscillator 72 by 1/10, generates a 1.023 MHz signal, and supplies it to the gold code generation unit 73. The gold code generation unit 73 generates a gold code and supplies it to the adder 74 and the epoch detection unit 77. The epoch detection unit 77 generates epoch information of 1 KHz from the gold code and supplies it to the frequency divider 76. The frequency divider 76 divides the epoch information by 1/20 and gives a 50 Hz signal to the data encoding unit 78. The data encoding unit 78 encodes the format data in accordance with the 50 Hz signal and gives it to the adders 74 and 75. The adder 74 adds the Gold code and the encoded data and outputs the result. The adder 75 adds the reproduction clock and the gold code and outputs the result. In accordance with such a method, a C / A code and a P code are generated in the PL transmitter 200 of FIG. 1, and positioning data is superimposed on these signals.
[0028]
FIG. 6 is a functional block diagram showing an embodiment of the receiver 300 of FIG. As described above, in this embodiment, the positioning signals in the L1, L2, and L5 wavebands that are SOC-modulated and BOC-modulated based on the C / A code and P-code are transmitted from the GPS satellite 100 and the PL transmitter 200 in FIG. Radiated. In FIG. 6, each positioning signal arriving at the antenna 301 is subjected to processing such as low noise amplification by the high frequency processing unit 302 and then input to correlation units 3031 to 303n provided corresponding to each positioning signal.
[0029]
The correlation units 3031 to 303n perform correlation processing on the respective positioning signals and detect positioning data included in the positioning signals. All or part of the detected positioning data is selectively given to the positioning processing unit 304 via the switching processing unit 305. The positioning processing unit 304 constantly monitors the reception status of each positioning data by the signal monitoring unit 304a, and for example, obtains a switching control signal so as to acquire only positioning data based on positioning signals whose reception status exceeds a certain threshold level. This is given to the switching processing unit 305. The switching processing unit 305 selects positioning data according to the switching control signal, and selectively provides positioning data based on the positioning signal in a good reception state to the positioning processing unit 304. The positioning processing unit 304 calculates its own position information from the given positioning data.
[0030]
As described above, in this embodiment, the GPS satellite 100 and the PL transmitter 200 modulate the carrier waves in the L1, L2, and L5 wavebands using the SOC modulation method and the BOC modulation method based on the C / A code and the P code. 12 types of positioning signals are generated and radiated into space. The receiver 300 receives the plurality of positioning signals, and the signal monitoring unit 304a monitors the reception state of the positioning signals in each wave band. Then, the position information of itself is calculated from the positioning data based on the positioning signal in a good reception state.
[0031]
Because of such a configuration, in addition to the L1 and L2 signals used in the existing system, and the positioning using only the C / A code and the SOC modulation method, a system that employs the L5 signal, the P code and the BOC modulation method. Can be built. As a result, the frequency band that can be used on the receiving side is remarkably increased, and it is possible to promote improvement in positioning accuracy by selecting a signal having a good reception state. In addition, positioning can be continued even if a signal that cannot be received due to some reason (entry into the shadow of a building, failure to capture GPS satellites and pseudolites, etc.) can be maintained, thus improving system reliability. Can do.
[0032]
Further, it is known that the L1 P code, the L2 P code, the C / A code, and the L5 code can perform positioning with higher accuracy than the existing L1 C / A code. In this embodiment, these signals are also transmitted from the pseudolite transmitter 200, and this also makes it possible to further improve the positioning accuracy.
[0033]
Furthermore, the existing differential GPS (DGPS) positioning method can also be extended using the system of this embodiment. That is, it is of course possible to correct the positioning data obtained by the system of the present embodiment by the DGPS method and calculate more accurate position information. Such an application is considered to be used for positioning systems using quasi-zenith satellites and wide-area reinforcement for aircraft. Therefore, the system of this embodiment is suitable for land movement, maritime movement, aeronautical movement field, surveying. Expected to be applied to a wide range of fields.
[0034]
In summary, according to the present embodiment, it is possible to provide a positioning system that can effectively use a plurality of frequency bands and has improved reliability.
[0035]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.
[0036]
【The invention's effect】
As described in detail above, according to the present invention, it is possible to provide a positioning signal transmission device, a positioning device, and a positioning system that can effectively use a plurality of frequency bands and have improved reliability.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing an embodiment of a positioning system according to the present invention.
FIG. 2 is a functional block diagram showing an embodiment of the PL transmitter 200 of FIG.
FIG. 3 is a block diagram showing a more detailed configuration of signal generators 1a, 1b, 3a, 3b, and 5a in FIG. 2;
4 is a block diagram showing a more detailed configuration of signal generators 2a, 2b, 4a, 4b, and 5b in FIG.
FIG. 5 is a block diagram showing a system code and SOC modulation system based on ICD-GPS-200C.
6 is a functional block diagram illustrating an embodiment of the receiver 300 of FIG.
[Explanation of symbols]
1 to 5: Transmission module, 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b ... Signal generation unit, 1c, 2c, 3c, 4c, 5c ... Mixer, 6 ... Mixer, 11 ... minute Circulator, 12 ... Data message generator, 21, 31 ... Multiplier, 22 ... Spreading code generator, 32 ... Oscillator, 40 ... Mixer, 41 ... Mixer, 50 ... Low pass filter, 61 ... Z counter, 62 ... Reset command Generating unit, 63 ... Epoch reset unit, 64 ... Epoch detecting unit, 65, 68 ... Code generating unit, 66 ... Adder, 67 ... Code selecting unit, 69 ... Epoch reset unit, 70, 76 ... Frequency divider, 71 ... Clock recovery unit 72 ... Oscillator 73 ... Gold code generation unit 74,75 ... Adder 77 ... Epoch detection unit 78 ... Data encoding unit 100 ... GPS satellite 200 ... Shoodora DOO transmitter 201 ... transmission antenna, 300 ... receiver, 301 ... antenna, 302 ... high frequency processing unit, 304 ... positioning processor, 304a ... signal monitoring unit, 305 ... switching unit, 3031～303N ... correlator

Claims (2)

A plurality of positioning signal transmitters that emit positioning signals;
A positioning device that receives the positioning signal and obtains position information;
Each of the plurality of positioning signal transmission devices,
The carrier wave of at least one of the L1, L2, and L5 wavebands is determined by the SOC ( Single offset carrier ) Modulation method and BOC ( Binary Offset Carrier ) Positioning signal generating means for generating a maximum of 12 types of positioning signals by modulating with at least one of the modulation systems;
A transmission unit that radiates the positioning signal generated by the positioning signal generation unit to space;
The positioning device is
Receiving means for receiving each of the positioning signals individually radiated from the plurality of positioning signal transmitters;
Monitoring means for monitoring each reception state of each positioning signal received by the receiving means;
Switching means for selectively switching and outputting a positioning signal whose reception state exceeds a certain threshold level;
Positioning means for obtaining position information of the positioning device from the positioning signal output from the switching means,
At least one of the plurality of positioning signal transmitters is disposed in the troposphere, and the other positioning signal transmitters are disposed at a higher altitude than the ionosphere. The positioning device is
Calculating means for calculating an ionospheric delay amount caused by the positioning signal passing through the ionosphere, using at least two of the positioning signals radiated from a positioning signal transmitter arranged at a higher altitude than the ionosphere; ,
The positioning system according to claim 1, further comprising a correction unit that corrects the position information based on the ionospheric delay amount calculated by the calculation unit.

Images