U.S. patent application number 11/480797 was filed with the patent office on 2008-09-25 for system for transmitting positioning signal.
This patent application is currently assigned to Funai Electric Co., Ltd.. Invention is credited to Ivan Petrovski, Hideyuki Torimoto.
Application Number | 20080231513 11/480797 |
Document ID | / |
Family ID | 36928345 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080231513 |
Kind Code |
A2 |
Torimoto; Hideyuki ; et
al. |
September 25, 2008 |
SYSTEM FOR TRANSMITTING POSITIONING SIGNAL
Abstract
A system for transmitting time-synchronized signals for
positioning is provided. The system for transmitting positioning
signals includes a transmitting apparatus mounted on artificial
satellite, a repeater mounted on an artificial satellite, and a
repeater mounted on an artificial satellite. Positional relation
among artificial satellites is specified beforehand. Transmitting
apparatus transmits a signal generated by encoding using a code
identifying itself. Repeater receives a signal from the
transmitting apparatus and transmits the signal. Repeater receives
a signal from the transmitting apparatus and transmits the signal.
The signals transmitted from the transmitting apparatus and
repeaters and are received by receiving apparatuses and having the
function of receiving the signals.
Inventors: |
Torimoto; Hideyuki; (Tokyo,
JP) ; Petrovski; Ivan; (Tokyo, JP) |
Correspondence
Address: |
OSHA LIANG L.L.P.
1221 MCKINNEY STREET
SUITE 2800
HOUSTON
TX
77010
UNITED STATES
713-228-8600
713-228-8778
docketing@oshaliang.com
|
Assignee: |
Funai Electric Co., Ltd.
7-1, Nakagaito 7-chome
Daito-Shi, Osaka
JP
574-0013
GNSS Technologies Inc.
4th Floor Matsuki Bldg. 6-12-5, Shinjuku, Shinjuku-ku
Tokyo
JP
160-0022
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070096985 A1 |
May 3, 2007 |
|
|
Family ID: |
36928345 |
Appl. No.: |
11/480797 |
Filed: |
July 3, 2006 |
Current U.S.
Class: |
342/453;
342/357.29; 342/357.48; 342/464 |
Current CPC
Class: |
G01S 5/0081 20130101;
G01S 19/46 20130101; G01S 19/11 20130101; G01S 19/428 20130101 |
Class at
Publication: |
342/453;
342/464 |
International
Class: |
G01S 3/02 20060101
G01S003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 2005 |
JP |
2005-196323 |
Claims
1. A system for transmitting a positioning signal to a receiving
apparatus configured to receive the positioning signal for
positioning the receiving apparatus, the system comprising: one
transmitting apparatus configured to transmit the positioning
signal; a plurality of relay apparatuses configured to relay the
positioning signal; and a supplying portion configured to supply
data specifying a positional relation between the transmitting
apparatus and each of the plurality of relay apparatuses to the
receiving apparatus; wherein said transmitting apparatus includes:
a time keeping portion keeping time, a storing portion storing data
as an object to be encoded, a generating portion configured to
generate the positioning signal containing the time, by encoding
data stored in the storing portion, using a code for identifying a
transmission apparatus of the positioning signal, and a
transmitting portion configured to transmit the positioning signal
generated by the generating portion; wherein each of the plurality
of relay apparatuses includes a receiving portion configured to
receive the positioning signal transmitted from the transmitting
apparatus, and a transmitting portion configured to transmit the
positioning signal received by the receiving portion; and wherein
the system comprises no more than one clock.
2. The system according to claim 1, wherein said supplying portion
includes an output portion configured to output said data
specifying the positional relation to said generating portion.
3. The system according to claim 1, wherein said supplying portion
includes a transmitting portion configured to transmit said data
specifying the positional relation through a path different from a
communication path of said transmitting apparatus.
4. The system according to claim 1, wherein said transmitting
apparatus and each of said plurality of relay apparatuses are
mounted on each of a plurality of artificial satellites.
5. The system according to claim 4, wherein at least one of said
plurality of artificial satellites stays space above a
predetermined region.
6. The system according to claim 4, wherein each of said artificial
satellites navigates maintaining a predetermined positional
relation between each of said plurality of artificial
satellites.
7. The system according to claim 4, wherein said generating portion
generates said positioning signal by encoding using a code for
identifying an artificial satellite on which said transmitting
apparatus is mounted.
8. The system according to claim 1, wherein said time keeping
portion is an atomic clock.
9. The system according to claim 1, wherein the transmitting
portion of said transmitting apparatus transmits said positioning
signal by wireless, and the receiving portion of said relay
apparatus receives said positioning signal by wireless.
10. The system according to claim 1, wherein the generating portion
of said transmitting apparatus generates said positioning signal by
encoding based on spread spectrum system.
11. The system according to claim 10, wherein said signal generated
by encoding has a period between one millisecond and one week.
12. The system according to claim 11, wherein said signal generated
by encoding has a period between one second and one hour.
13. The system according to claim 12, wherein said signal generated
by encoding has a period of at least one minute and within a
predetermined tolerable range.
14. The system according to claim 1, wherein the transmitting
portion of said relay apparatus transmits said positioning signal
without changing contents of the signal received by said receiving
portion.
15. The system according to claim 1, wherein said transmitting
apparatus further includes a receiving portion configured to
receive input of data as an object to be encoded.
16. The system according to claim 1, wherein said data as an object
to be encoded includes data for specifying position of said
transmitting apparatus.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a technique for
transmitting a signal for positioning. More specifically, the
present invention relates to system for transmitting synchronized
signals for positioning.
[0003] 2. Description of the Background Art
[0004] A method of positioning using a signal transmitted from a
satellite has been known. By way of example, a GPS (Global
Positioning System) signal transmitted from a GPS satellite is used
for positioning. More specifically, an apparatus receiving GPS
signals transmitted from three or more GPS satellites read data
contained in each of the signals, executes a predetermined
operation, and calculates positional information. Here, accuracy of
time data contained in the data determines the accuracy of
positional information, and therefore, a high-precision clock (for
example, an atomic clock) is mounted on each GPS satellite. It is
noted that the clocks must be synchronized with each other.
Therefore, in order to maintain synchronization between each of the
clocks mounted on GPS satellites, sometimes it becomes necessary to
correct time of a clock on a satellite using time information of a
master clock provided on the ground.
[0005] A system enabling positioning based on satellite signals,
that is, a so-called satellite positioning system may include, in
addition to GPS operated by the United States of America as
mentioned above, Galileo of which operation is under consideration
of the European Union, GLONASS (Global Navigation Satellite System)
operated by the Russian Federation and the like.
[0006] In the foregoing, conventional art related to the present
invention has been described based on general technical information
known to the applicant. To the best of applicant's memory, the
applicant does not have any information to be disclosed as prior
art, before the filing of this application.
[0007] When positional information is to be calculated using radio
signals as described above, the following problems arise. As it is
necessary to mount a high-precision clock on each satellite or a
ground-based transmitter as a pseudolite, the cost for building a
system for transmitting positioning signals increases.
SUMMARY OF THE INVENTION
[0008] The present invention was made to solve the above described
problems, and its object is to provide a system for transmitting
synchronized signals for positioning.
[0009] Another object of the present invention is to provide a
system for transmitting synchronized signals for positioning using
one clock in the system.
[0010] In order to attain the above described objects, according to
an aspect, the present invention provides a system for transmitting
a positioning signal to a receiving apparatus receiving the
positioning signal for positioning the receiving apparatus. The
system includes one transmitting apparatus transmitting the
positioning signal. The one transmitting apparatus includes time
keeping means for keeping time, storing means for storing data as
an object to be encoded, generating means for generating the
positioning signal containing the time, by encoding data stored in
the storing means, using a code for identifying a transmission
apparatus of the positioning signal, and transmitting means for
transmitting the positioning signal generated by the generating
means. The system further includes a plurality of relay apparatuses
relaying the positioning signal, and supplying means for supplying
data specifying positional relation between the transmitting
apparatus and each of the plurality of relay apparatuses to the
receiving apparatus. Each of the plurality of relay apparatuses
includes receiving means for receiving the signal transmitted from
the transmitting apparatus, and transmitting means for transmitting
the signal received by the receiving means.
[0011] Preferably, the supplying means includes output means for
outputting the data specifying the positional relation to the
generating means.
[0012] Preferably, the supplying means includes transmitting means
for transmitting the data specifying the positional relation
through a path different from a communication path of the
transmitting apparatus.
[0013] Preferably, the transmitting apparatus and each of the
plurality of relay apparatuses are mounted on each of a plurality
of artificial satellites.
[0014] Preferably, at least one of the plurality of artificial
satellites stays space above a predetermined region.
[0015] Preferably, each of the artificial satellites navigates
maintaining a predetermined positional relation between each of the
plurality of artificial satellites.
[0016] Preferably, the generating means generates the positioning
signal by encoding using a code for identifying an artificial
satellite on which the transmitting apparatus is mounted.
[0017] Preferably, the time keeping means is an atomic clock.
[0018] Preferably, the transmitting means of the transmitting
apparatus transmits the positioning signal by wireless. The
receiving means of the relay receives the positioning signal by
wireless.
[0019] Preferably, the generating means of the transmitting
apparatus generates the positioning signal by encoding based on
spread spectrum system.
[0020] Preferably, the signal generated by encoding has a period
between one millisecond and one week.
[0021] Preferably, the signal generated by encoding has a period
between one second and one hour.
[0022] Preferably, the signal generated by encoding has a period of
at least one minute and within a predetermined tolerable range.
[0023] Preferably, the transmitting means of the relay transmits
the signal without changing contents of the signal received by the
receiving means.
[0024] Preferably, the transmitting means of the relay transmits
the signal without changing time contained in the signal received
by the receiving means.
[0025] Preferably, the transmitting apparatus further includes
receiving means receiving input of data as an object to be
encoded.
[0026] Preferably, the data as an object to be encoded includes
data for specifying position of the transmitting apparatus.
Preferably the data can be transmitted by separate channels.
[0027] The foregoing and other objects, features, aspects and
advantages of the present invention will become more apparent from
the following detailed description of the present invention when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a schematic diagram representing a configuration
of a system transmitting a signal for positioning in accordance
with a first embodiment of the present invention.
[0029] FIG. 2 is a block diagram representing a hardware
configuration of a transmitting apparatus 200 constituting the
system in accordance with the first embodiment of the present
invention.
[0030] FIG. 3 is a block diagram representing a hardware
configuration of a repeater 300 constituting the system in
accordance with the first embodiment of the present invention.
[0031] FIG. 4 is a block diagram representing hardware
configuration of a GPS receiver 400 capable of receiving the signal
transmitted from the system in accordance with the first embodiment
of the present invention.
[0032] FIG. 5 schematically shows a structure of the signal from
the system for transmitting a signal for positioning in accordance
with the first embodiment of the present invention.
[0033] FIG. 6A represents the structure of the signal transmitted
by a transmitting apparatus 200.
[0034] FIG. 6B represents the structure of the signal transmitted
by a repeater 300-1.
[0035] FIG. 6C represents the structure of the signal transmitted
by a repeater 300-2.
[0036] FIG. 7 is a flow chart representing process steps for
transmitting the signal for positioning, executed by transmitting
apparatus 200.
[0037] FIG. 8 is a flow chart representing steps of a signal
relaying process executed by repeater 300.
[0038] FIG. 9 is a flow chart representing process steps executed
by GPS receiver 400 capable of receiving the signal transmitted
from the system in accordance with an embodiment of the present
invention.
[0039] FIG. 10 represents an exemplary configuration of the system
in accordance with a second embodiment of the present
invention.
[0040] FIG. 11 is a block diagram representing a hardware
configuration of a transmitting apparatus 1100 constituting the
system in accordance with the second embodiment of the present
invention.
[0041] FIG. 12 is a block diagram representing a hardware
configuration of a repeater constituting the system in accordance
with the second embodiment of the present invention.
[0042] FIG. 13 is a flow chart representing process steps executed
by transmitting apparatus 1100 in accordance with the second
embodiment of the present invention.
[0043] FIG. 14 is a flow chart representing process steps executed
by a repeater constituting the system in accordance with the second
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] In the following, embodiments of the present invention will
be described with reference to figures. In the following
description, same portions are denoted by the same reference
characters. They have the same names and functions. Therefore,
detailed description thereof will not be repeated.
[0045] Referring to FIG. 1, a system for transmitting a signal for
positioning (hereinafter referred to as a positioning signal) in
accordance with an embodiment of the present invention will be
described. FIG. 1 schematically shows the system's configuration.
Here in below for ease of description, terminologies used for a GPS
signal are used for illustration. The positioning signal, however,
is not limited to the GPS signal.
[0046] The system includes a transmitting apparatus 200 mounted on
an artificial satellite 102, a repeater 300-1 mounted on an
artificial satellite 104, and a repeater 300-2 mounted on an
artificial satellite 106. Positional relation between each of
artificial satellites 102, 104 and 106 is specified beforehand. By
way of example, the data representing the positional relation is
formed in advance at a base station on the ground that monitors
each artificial satellite. Here, the data may have, for example,
date and time related to the position at which each satellite
navigates. The data may be a navigation message including orbit
information (or ephemeris) used in the so-called GPS system.
[0047] Here, artificial satellites 102, 104 and 106 are, for
example, communication satellites, and they may be other
satellites. For instance, they may be satellites that constitute
the quasi-zenith system presently contemplated in Japan. At least
one of the satellites constituting this system navigates to be seen
near the zenith in Japan at any time, and therefore, the signal
from the satellite navigating near the zenith can readily be
received even at an urban area where a large number of tall
buildings stand. If any other system similar to the quasi-zenith
system is implemented in other country, the satellites may be the
ones that constitute the corresponding system.
[0048] Transmitting apparatus 200 transmits signals generated by
encoding, using a code for identifying itself Specifically,
transmitting apparatus 200 transmits signals Lqz(1), Lqz(2),
Lqz(3), Lqz(4) and Lqz(5). Frame structures of these signals will
be described in detail with reference to FIG. 5.
[0049] Repeater 300-1 receives the signal Lqz(1) transmitted from
transmitting apparatus 200, amplifies the signal and transmits the
result with higher transmission output. Specifically, repeater
300-1 transmits signal Lqz(11), Lqz(12) and Lqz(13), respectively.
Here, the signal Lqz(1) contains data for calculating position such
as time information or navigation message, as will be described
later, and such data are unchanged. The transmitted signals are
received by receiving apparatuses 400-2, 400-3 or an antenna 120
having a function of receiving the signals.
[0050] Repeater 300-2 receives the signal Lqz(2) transmitted from
transmitting apparatus 200, amplifies the signal and transmits the
result with higher transmission output. Specifically, repeater
300-1 transmits signals Lqz(21), Lqz(22) and Lqz(23), respectively.
Similar to the signals transmitted from repeater 300-1, the signals
transmitted from repeater 300-2 are also received by a receiving
apparatus having the receiving function. Though two repeaters are
shown in FIG. 1, the number of repeaters forming the system of the
present invention may be at least two, Preferably, the system
includes three repeaters.
[0051] Referring again to FIG. 1, on the ground, receiving
apparatuses 400-2 and 400-3 are provided. Receiving apparatus 400-2
is installed on a roof of a building 110, and is capable of
receiving signals transmitted from artificial satellites 102, 104
and 106, respectively. Further, antenna 120 is on a building 112.
Antenna 120 is capable of receiving signals transmitted from
artificial satellites 102, 104 and 106. Antenna 120 receives
signals Lqz(3), Lqz(11) and Lqz(21). The received signals are
transferred to relay apparatuses 130-1, 130-2, and 130-3 through a
cable. More apparatuses may be implemented in the building 110.
Each of the relay apparatuses 130-1, 130-2, 130-3 transmits the
signals to the inside of building 110. Receiving apparatus 400-1 is
capable of receiving signals Lqz(11), Lqz(21) and Lqz(3).
[0052] Referring to FIG. 2, transmitting apparatus 200 forming the
system in accordance with an embodiment of the present invention
will be described. FIG. 2 is a block diagram representing a
hardware configuration of transmitting apparatus 200.
[0053] Transmitting apparatus 200 includes a signal generating
circuit 210, a clock 220, an oscillator 230, a multiplier 240, an
up-converter 250, a transmitting portion 260 and an antenna 270.
Time data measured by clock 220 is input to signal generating
circuit 210. Signal generating circuit 210 generates a positioning
signal (for example, a GPS signal) based on the time data and
navigation message 214. Navigation message 214 is transmitted, for
example, from a base station (not shown) on the ground for the
satellite.
[0054] Signal generating circuit 210 generates the signal by
encoding based on, for example, spread spectrum communication
system. The signal output from signal generating circuit 210 is
input to multiplier 240. The signal output from oscillator 230 is
also input to multiplier 240. Multiplier 240 modulates the
positioning signal from signal generating circuit 210 by a carrier
wave from oscillator 230, and generates a signal of intermediate
frequency. The generated signal is input to up-converter 250.
[0055] Up-converter 250 increases the frequency of the intermediate
frequency signal output from multiplier 240 to a frequency for
transmission through the space, and outputs the up-converted signal
to transmitting portion 260. Transmitting portion 260 includes a
high-power amplifier (not shown), enhances the output for
transmitting the input signal, and transmits the signal with the
output thus enhanced. The signal is transmitted to the outer space
through antenna 270.
[0056] In the following, the GPS signal as an example of the
positioning signal will be described.
[0057] Assume that transmitting apparatus 200 is an apparatus for
transmitting the GPS signal. In that case, the signal from
transmitting apparatus 200 is encoded by spread spectrum system
using a C/A code (Coarse and Access Code) (also referred to as a
PRN (Pseudo Random Noise) code) consisting of a quasi-random
sequence that can identify the satellite. Here each C/A code (P
code) consists of 1024 bits. It should be noted that since the
positioning signal is modified from GPS signal in the embodiment
according to the invention, the transmitted signal is not
equivalent to the GPS signal in itself.
[0058] Referring to FIG. 3, a repeater constituting the system as a
relay apparatus in accordance with an embodiment of the present
invention will be described. FIG. 3 is a block diagram representing
a hardware configuration of repeater 300. Here, repeater 300
generally represents repeaters 300-1 and 300-2 shown in FIG. 1 as
well as other repeaters.
[0059] Repeater 300 includes an antenna 310, a low-noise amplifier
320, a transmitting portion 380 and an antenna 390. Antenna 310
receives a signal (for example, Lqz(1) and Lqz(2) shown in FIG. 1)
transmitted from transmitting apparatus 200. The received signal is
input to low-noise amplifier 320. Low-noise amplifier 320 amplifies
the input weak signal and outputs the same to transmitting portion
380. Transmitting portion 380 transfers the signal to antenna 390.
Antenna 390 outputs the signal from transmitting portion 380.
Specifically, repeater 300 transmits the signal received by antenna
310 again, with the contents unchanged. Therefore, when the signal
received by repeater 300 contains time information, for example,
the signal is output as it is with the information unchanged.
[0060] Antenna 310 may further have a driving apparatus (not shown)
such as an actuator for changing the direction of antenna 310, and
a controller (not shown) controlling the position of the driving
apparatus. In this case, as the position of the driving apparatus
is changed by controller, antenna 310 can more reliably receive the
radio wave transmitted from transmitting apparatus 200.
[0061] Referring to FIG. 4, a GPS receiver 400 that can receive the
signal transmitted from the system in accordance with an embodiment
of the present invention will be described. FIG. 4 is a block
diagram representing a hardware configuration of GPS receiver 400.
GPS receiver 400 is, by way of example, a dedicated apparatus for
positioning having the GPS function, a portable telephone having
the GPS function or the like.
[0062] GPS receiver 400 includes an antenna 402, a low-noise
amplifier 404, a down-converter 406, an intermediate amplifier 408,
a multiplier 410, a parallel correlator circuit 430, an oscillating
circuit 422, a CPU (Central Processing Unit) 450, a memory 460 and
a display 470. Memory 460 is implemented, for example, by a flash
memory, and stores externally input ephemeris and software for
executing an operation for specifying a position. The information
stored in memory 460 may be obtained through a communication
network such as the Internet, from an information provider or a
system developer that already have such information. Alternatively,
the information may be obtained from the GPS signal. More
specifically, when GPS receiver 400 is a portable telephone, by way
of example, the information may be stored by a user or manufacturer
of the telephone in GPS receiver 400.
[0063] The positioning signal is received by antenna 402. The
signal is input to low-noise amplifier 404. Low-noise amplifier 404
cuts the noise, filters and amplifies the signal, and outputs the
amplified signal to down-converter 406. Down-converter 406 converts
the signal to an intermediate frequency signal, and outputs the
result to intermediate amplifier 408. Intermediate amplifier 408
amplifies the input intermediate frequency signal and outputs the
result to multiplier 410.
[0064] From oscillating circuit 422, a signal having the frequency
(f.sub.IF+f.sub.D), that is, the frequency f.sub.IF of the
intermediate frequency signal shifted by Doppler frequency f.sub.D
calculated based on the ephemeris, is output. The signal having
this frequency is input to multiplier 410.
[0065] Multiplier 410 multiplies the signal of this frequency from
oscillating circuit 422 and the signal from intermediate amplifier
408. Thus, the intermediate frequency signal is converted to a
baseband signal.
[0066] The signal from multiplier 410 is input to parallel
correlator circuit 430. Parallel correlator circuit 430 includes a
plurality of correlators 432-1 to 432-n arranged parallel to each
other to enable simultaneous execution of a process for detecting
delay possibly experienced when the positioning signal propagates.
Each correlator is hardware-implemented. Respective correlators
correspond to the possible propagation delay time of positioning
signals from a plurality of artificial satellites 102, 104 and 106.
Therefore, after the signal mentioned above is input to parallel
correlator circuit 430, each correlator executes a process to
establish correlation with a locally generated PRN code, whereby
the propagation delay times of the positioning signals transmitted
from a plurality of satellites (corresponding to phase delay of the
signal from the locally generated PRN code) can be calculated in
parallel.
[0067] Here, the number of "possible propagation delay times of
positioning signals" will be described. Assume that two samples are
sampled per 1 chip (bit) of the PRN code. In one period of the PRN
code, there are 2046 samples, in other words, the number of
possible delay samples is 2046. Taking into consideration that the
PRN code is common, as shown in FIG. 1, the sample number is 2046
(possible delays per channel).times.2 channels (I and Q
components)=4092.
[0068] The output from parallel correlator circuit 430 is
accumulated, by way of example, over a plurality of PRN code
periods with phase aligned (in coherent manner) for in-phase
component (I component) and quadrature component (Q component)
period by period of the PRN code, by an integrator 434-1. Outputs
from respective integrators 434-1 to 434-n are each squared in an
operator (not shown), and an absolute value is taken out. The taken
outputs are accumulated by an accumulator (not shown) in a
non-coherent manner. After the accumulating process by the
accumulator, noise in the signals are suppressed, an output of a
correlator corresponding to the phase delay described above is
monitored as a peak, and stored in memory 460.
[0069] Specifically, in the example shown in FIG. 1, when
correlation is calculated by parallel correlator circuit 430 using
a common PRN code, it follows that signals from three artificial
satellites 102, 104 and 106 are calculated in parallel, and peaks
for respective signals are detected.
[0070] Phase delay of positional signals from specific artificial
satellites 102, 104 and 106, that is, propagation delay times of
positional signals can be known. Further, based on the information
stored in advance in memory 460, orbit information of each
artificial satellite can be obtained. Here, combinations of
satellite positions specified by the orbit information based on the
received signals are in finite number. Therefore, similar to a
conventional signal processing such as GPS signal processing, an
operation is possible to specify the position of GPS receiver 400.
This operation is executed, for example, by CPU 450.
[0071] Detailed operation of parallel correlator circuit 430 is as
follows. An IF input sample having an intermediate frequency is
multiplied with an output from a numerical control oscillator
(hereinafter denoted by NCO) in multiplier 410, and I component and
Q component are separated.
[0072] Thereafter, an output from multiplier 410 is re-sampled by a
re-sampler (not shown) at a sample rate appropriate for the
correlating process. The re-sampling rate is determined by a second
NCO (not shown). An output of the second NCO is programmed based on
a pseudo-distance expected in advance from the ephemeris and coarse
positional information of GPS receiver 400, for the incoming
signal.
[0073] An output of the re-sampler is input to correlators 432-1 to
432-n calculating convolution between the received positioning
signal and a set of reference waveforms (PRN codes) for artificial
satellites 102, 104 and 106 that are at visible positions. Each
channel includes a plurality of delay elements (not shown). An
operation logic block (not shown) calculates correlation between
the entire characteristic period of the input data and a full PRN
code sequence for a desired satellite. Here, the "entire
characteristic period (epoch)" refers to a period that corresponds
to one period of the PRN code, and when one period of a PRN code
consists of 1024 chips (bits) and there are two samples per one
chip, it corresponds to a period of 2046 samples.
[0074] In each clock period in which parallel correlator circuit
430 operates, a result of calculation of a new correlation value
for one specific delay time is generated and stored in memory 460.
Therefore, at the end of the entire characteristic period, memory
460 come to have a fill set of correlation results for all possible
delays stored therein. The sequence of correlation results
corresponds to convolution between the input signals and the
reference waveforms locally generated by the PRN code
generator.
[0075] Though a main frame of a GPS signal as one type of the
positioning signals has the period of 30 seconds, the delay time
from each satellite can be specified within, for example, 1 second,
because of such a configuration of parallel correlator circuit 430
as described above. Therefore, as compared with the method that
necessitates extraction of navigation message directly from the
received GPS signal, the position calculating process can be done
at a higher speed.
[0076] Referring again to FIG. 4, CPU 450 executes an operation for
specifying the position of receiving apparatus 400, based on the
information stored in memory 460 and on the information output from
parallel correlator circuit 430. This process is well known, and
therefore, description thereof will not be given here. Further, CPU
450 executes a process for generating data to display an image on
display 470. By way of example, this process is for generating data
for display based on the calculated positional information and
image data obtained separately. The data for display is stored in a
VRAM (Video Random Access Memory) (not shown). Display 470 displays
an image based on the data.
[0077] Referring to FIG. 5, a structure of the signal transmitted
from the system transmitting the positional signal in accordance
with the present embodiment will be described. FIG. 5 schematically
shows the structure of the GPS signal as one type of the
positioning signal.
[0078] The GPS signal transmitted from transmitting apparatus 200
includes 25 main frames. It takes 30 seconds to receive each frame.
Therefore, in order to receive all the frames, it takes 12 minutes
and 30 seconds. The main frame includes a navigation message. The
navigation message includes time correction data, almanac, orbit
information, ionosphere correction data and so on. The navigation
message is transmitted from a base station on the ground to, for
example, transmitting apparatus 200 mounted on artificial satellite
102. The transmission may be together with transmission of a signal
for correcting time of clock 220 provided on transmitting apparatus
200. Alternatively, the navigation message may be transmitted by
itself, as needed.
[0079] Mainframe 520 includes five sub-frames 521 to 525. The
fourth sub-frame 524 and the fifth sub-frame 525 each include 25
pages. A sub-frame includes 10 words in 6 seconds. The first word
includes a telemetry word (TLM). The second word is a hand-of-word
(HOW).
[0080] Referring to FIGS. 6A to 6C, a manner of positioning signal
transmission will be schematically described. FIG. 6A is an
illustration schematically showing the structure of the PRN code
transmitted by transmitting apparatus 200. FIG. 6B is an
illustration schematically showing the structure of the PRN code
transmitted by repeater 300-1. FIG. 6C is an illustration
schematically showing the structure of the PRN code transmitted by
repeater 300-2. For simplicity of description, here, an example
will be taken that includes four PRN codes. It should be noted that
the positioning signal is a combination of many PRN sequences.
[0081] As can be seen from FIG. 6A, when transmitting apparatus 200
transmits signals having four PRN codes accumulated, the signals
contain CODE 1, CODE 2, CODE3 and CODE4. At time point t(1),
transmitting apparatus 200 is transmitting a code, CODE1.
Thereafter, at time point t(2), transmitting apparatus 200 has
finished transmission of CODE2. At time point t(3), transmitting
apparatus 200 has finished transmission of CODE3. At time point
t(4), transmitting apparatus 200 has finished transmission of
CODE4. At time point t(5), transmitting apparatus 200 has finished
transmission of a new CODE1 included in the next code sequence.
[0082] In this case, repeater 300-1 receives the signal transmitted
from transmitting apparatus 200 after a delay time corresponding to
the distance determined by the positional relation between
transmitting apparatus 200 and repeater 300-1. Repeater 300-1
transmits the signal thus received after the delay time, and
therefore, the signal sequence transmitted by repeater 300-1 is
generated delayed from the signal sequence transmitted by
transmitting apparatus 200.
[0083] Specifically, as can be seen from FIG. 6B, at time point
t(1), repeater 300-1 has finished transmission of CODE4 that has
been transmitted in the past by transmitting apparatus 200. At time
point t(2), repeater 300-1 transmits, with a delay, CODE1 that has
been transmitted by transmitting apparatus at time t(1). Similarly,
repeater 300-1 finishes transmission of CODE2 at time point t(3).
Transmission of this signal by transmitting apparatus 200 has been
finished at time point t(2). Repeater 300-1 finishes transmission
of CODE3 at time point t(4). Transmission of this signal by
transmitting apparatus 200 has been finished at time point t(3).
Similarly, repeater 300-1 finishes transmission of CODE4 at time
point t(5). This signal has been transmitted by transmitting
apparatus 200 at time point t(4).
[0084] As can be seen from FIG. 6C, repeater 300-2 transmits the
signal received from transmitting apparatus 200 delayed from
transmission timings of transmitting apparatus 200 and repeater
300-1. For example, CODE1 that has been transmitted at time point
t(1) by transmitting apparatus 200 is finished by repeater 300-2 at
time point t(3).
[0085] In this manner, one same signal is output at different time
points from transmitting apparatus 200 and repeaters 300-1 and
300-2, respectively. Receiving apparatuses 400-2 and 400-3
receiving these signals execute a process for calculating the
positional information, using these signals as GPS signals
respectively transmitted from transmitting apparatus 200 and
repeaters 300-1 and 300-2. Here, the clock error included in the
signal (FIG. 6B) transmitted by repeater 300-1 and in the signal
(FIG. 6C) transmitted by repeater 300-2 is the same as the clock
error included in the signal (FIG. 6A) transmitted by transmitting
apparatus 200. Therefore, without an orbit error and a difference
in signal propagation errors, chunk signals are perfectly
synchronized. Each receiving apparatus can accurately calculate the
positional information, as will be described later. Further, as
shown in FIG. 3, it is unnecessary to provide a clock for obtaining
time information in repeaters 300-1 and 300-2. Therefore, time
correcting process becomes unnecessary for repeaters 300-1 and
300-2, making maintenance easier. Further, repeaters 300-1 and
300-2 can be formed easily at a lower cost than apparatuses that
need the clock.
[0086] Referring to FIG. 7, a control structure of transmitting
apparatus 200 will be described. FIG. 7 is a flow chart showing
process steps for transmitting the positioning signal, executed by
transmitting apparatus 200.
[0087] In step S710, signal generating circuit 210 of transmitting
apparatus 200 obtains time information from clock 220. In step
S720, signal generating circuit 210 generates a positioning signal
based on the time information and the navigation message.
[0088] In step S730, signal generating circuit 210 encodes the
signals using predetermined codes, and outputs the encoded signals
to multiplier 240. The codes with PRN are, by way of example, for
identifying artificial satellites 102, 104, 106 and possibly more
such as relay apparatuses 130-1, 130-2, 130-3, pseudolites or the
like. Objects identified by the codes depend on an orbit and code
chunks. The signal is modulated by multiplier 240 and output to
up-converter 250. Up-converter 250 converts the frequency of the
signal from multiplier 240 to a high frequency, and the converted
signal is input to transmitting portion 260.
[0089] In step S740, transmitting portion 260 converts the signal
output from up-converter 250 to a high output, and transmits the
converted signal. The length of the code transmitted in this manner
is, for example, from 1 mili-second to one week. Preferably, it is
between one second and one hour, for example, a few seconds to
several tens of seconds.
[0090] Referring to FIG. 8, a control structure of the repeater
constituting the system in accordance with an embodiment of the
present invention will be described. FIG. 8 is a flow chart showing
process steps executed by repeater 300 for transmitting
signals.
[0091] In step S810, repeater 300 receives a signal transmitted
from transmitting apparatus 200, through antenna 310. The signal is
input to low-noises amplifier 320, subjected to amplification, and
output to transmitting portion 380.
[0092] In step S820, transmitting portion 380 enhances the output
of the signal, and transmits the same as a high-output signal. The
signal is broadcast to the outer space, through antenna 390. In
this manner) repeater 300 outputs the signal received from
transmitting apparatus 200. Therefore, information (for example,
time information) included in the signal is unchanged.
[0093] In another aspect, repeaters 300-1 and 300-2 may add data
for identifying artificial satellites 104 and 106 on which the
repeaters are mounted, to the received signal. In this case, the
receiving apparatus receiving the signal from repeater 300 can
readily recognize that the signal is transmitted from artificial
satellite 104 or 106. Therefore, in the process for calculating
positional information by GPS receiver 400, the process for
specifying the source of the signal can be omitted. This enables
calculation of the position of receiving apparatus through the
conventionally used process for calculating positional information.
Thus, a receiving apparatus having a function of calculating
positional information may have a general configuration.
[0094] Referring to FIG. 9, a control structure of a receiving
apparatus that can receive the signal transmitted by the system in
accordance with an embodiment of the present invention will be
described. FIG. 9 is a flow chart representing process steps
executed by GPS receiver 400.
[0095] In step S910, GPS receiver 400 receives positioning signals
from artificial satellites 102, 104 and 106 through antenna 402. In
step S920, GPS receiver 400 specifies, based on the first received
signal, the artificial satellite that transmitted the signal. In
the example shown in FIG. 1, artificial satellite 102 is
specified.
[0096] In step S930, GPS receiver 400 calculates signal propagation
delay time based on the data representing position stored in memory
460 and on the received signals. Here, the data representing
position may be the one representing relative positions (such as
distance between each of the satellites) of artificial satellites
102, 104 and 106. When the position of any of the satellites can be
specified by the data, positions of other satellites can naturally
be specified.
[0097] Specifically, the positional relation between each of
transmitting apparatus 200 and repeaters 300-1 and 300-2 is known
beforehand, and therefore, when GPS receiver 400 receives a
plurality of signals having the same time information, it can
readily be specified that the source of the signals received
simultaneously is transmitting apparatus 200. The propagation delay
time of the GPS signal can be calculated when transmission
apparatus 200 is specified. Namely, time points at which one the
same signal is received differ, and hence, difference between
reception time points is calculated. Using this result, it is
possible to narrow the candidates of repeaters that can relay the
signal transmitted from transmitting apparatus 200. Thus, GPS
receiver 400 can specify a repeater as a transmission source of the
actually received signal by, for example, combining repeater
candidates.
[0098] In step S940, GPS receiver 400 calculates positional
information representing the position of GPS receiver 400, based on
the received signals and the calculated propagation delay time. In
step S950, GPS receiver 400 outputs the positional information to
display 470.
[0099] In this manner, according to the system transmitting a
positioning signal in accordance with the first embodiment of the
present invention, transmitting apparatus 200 transmits a signal
including time information. The transmitted signal is received by
GPS receiver 400 and repeaters 300-1 and 300-2. Repeaters 300-1 and
300-2 outputs the received signal. Here, the contents of time
information contained in the signal are unchanged. The signals
output from repeaters 300-1 and 300-2 are received by GPS receiver
400.
[0100] GPS receiver 400 holds, in advance, data representing
relation between transmitting apparatus 200 and the position of
each of the repeaters including repeaters 300-1 and 300-2.
Therefore, even when GPS receiver receives signals containing the
same time information a number of times, it is possible for GPS
receiver 400 to specify a repeater as the transmission source of
each signal, based on the data. Thus, GPS receiver 400 can
calculate information that represents the position of itself. Here,
the time information contained in each signal is generated based on
clock 220 mounted on transmitting apparatus 200, and therefore,
synchronization is established. Accordingly, GPS receiver 400
receives signals that are synchronized in time information, and
therefore, the positional information calculated from such signals
does not involve any time error.
[0101] Thus, a system transmitting synchronized signals for
positioning can be provided. Further, a system transmitting
synchronized signals for positioning can be provided using one
clock in the system.
Second Embodiment
[0102] In the following, a second embodiment of the present
invention will be described. The system for transmitting signals
for positioning in accordance with the present embodiment differs
from the system in accordance with the first embodiment in that the
system is built on the ground.
[0103] Referring to FIG. 10, the system of the present embodiment
will be described. FIG. 10 shows an exemplary configuration of the
system on the ground.
[0104] A transmitting apparatus 1100 transmitting a positioning
signal is mounted on a roof of a building 1000. On the roofs of
buildings 1010 and 1020, repeaters 1200-1 and 1200-2 capable of
transmitting positioning signals are mounted, respectively.
Repeaters 1200-1 and 1200-2 are connected to transmitting apparatus
1100 through a network 1030. Here, positional relation between
transmitting apparatus 1100 and repeaters 1200-1 and 1200-2 is
known beforehand. To network 1030, a base station server that can
provide data representing the positional relation, for example, is
connected. The network 1030 is, by way of example, the Internet.
However, it may be any private network.
[0105] When transmitting apparatus 1100 transmits a positioning
signal Lqz(1), the signal is transmitted by radio wave and
transferred to repeaters 1200-1 and 1200-2, through network 1030,
as shown in FIG. 10. For example, repeater 1200-1 receives the
signal from transmitting apparatus 1100, and transmits the signal
as Lqz(11) without any processing. Similarly, repeater 1200-2
receives signal Lqz(1) input from transmitting apparatus 1100 and
transmits the signal as Lqz(12). Therefore, from the view point of
PRN code, signals Lqz(1), Lqz(11) and Lqz(12) are the same
signal.
[0106] In such an environment, GPS receiver 400 receives three
signals as positioning signals, that is, Lqz(1), Lqz(11) and
Lqz(12). GPS receiver 400 can calculate positional information
based on respective received signals.
[0107] Referring to FIG. 11, transmitting apparatus 1100
constituting the system in accordance with the present embodiment
will be described. FIG. 11 is a block diagram representing a
hardware configuration of transmitting apparatus 1100.
[0108] Transmitting apparatus 1100 includes, in addition to the
configuration shown in FIG. 2, an output port 1110. Output port
1110 outputs a signal provided from signal generating circuit 210
to network 1030.
[0109] Referring to FIG. 12, configurations of repeaters 1200-1,
1200-2 constituting the system of the present embodiment will be
described. FIG. 12 is a block diagram representing a hardware
configuration of repeater 1200 implemented as repeaters 1200-1 and
1200-2.
[0110] Repeater 1200 includes an input port 1210, a multiplier
1220, an oscillator 1230, an up-converter 1240, and a transmitting
portion 380. Input port 1210 is connected, for example, to network
1030.
[0111] Input port 1210 outputs a signal input from network 1030 to
multiplier 1220. Oscillator 1230 generates the same frequency as
the carrier frequency of the signal transmitted from transmitting
apparatus 1100. The signal is output to multiplier 1220. Multiplier
1220 multiplies the signal Lqz(1) from input port 1210 by the
carrier wave from oscillator 1230, and generates a signal that
oscillates as a positioning signal. The signal is input to
up-converter 1240. Up-converter 1240 converts the frequency of this
signal to a high frequency, and outputs a high frequency signal to
transmitting portion 380. Transmitting portion 380 enhances the
output of the high frequency signal, and transmits the signal
through antenna 390. This signal corresponds to signals Lqz(11) and
Lqz(12) shown in FIG. 10.
[0112] Referring to FIG. 13, a control structure of transmitting
apparatus 1100 in accordance with the present embodiment will be
described. FIG. 13 is a flow chart representing process steps
executed by transmitting apparatus 1100. Process steps that are the
same as those of the first embodiment are denoted by the same step
numbers, and description thereof will not be repeated.
[0113] In step S1310, output port 1110 of transmitting apparatus
1100 outputs the positioning signal received from signal generating
circuit 210 to network 1030. The manner of communication here is
packet communication, though the manner is not limited thereto.
[0114] Referring to FIG. 14, control structures of repeaters 1200-1
and 1200-2 constituting the system of the present embodiment will
be described. FIG. 14 is a flow chart representing process steps
executed by each repeater for transmitting signals. In the
following, the process will be described as executed by repeater
1200.
[0115] In step S1410, repeater 1200 receives positioning signal
Lqz(1) from network 1030. In step S1420, repeater 1200 modulates,
in multiplier 1220, the received signal. In step 1430, repeater
1200 transmits the modulated signals (Lqz(11), Lqz(12)).
[0116] Thereafter, when the transmitted signal is received by GPS
receiver 400, GPS receiver 400 executes a process for calculating
the positional information, and the position of the receiver itself
is specified, as described in the first embodiment (FIG. 4).
[0117] As described above, in the system in accordance with the
second embodiment of the present invention, the signal transmitted
from transmitting apparatus 1100 sending the positional signal is
directly received as a radio wave by GPS receiver 400. The signal
is also transmitted through network 1030 to repeaters 1200-1 and
1200-2. Each repeater outputs the signal. Thus, GPS receiver 400
can receive signals provided from at least three portions. These
signals have the same time information. As the transmitting
apparatus 1100 and repeaters 1200-1 and 1200-2 are placed
beforehand on buildings 1000, 1010 and 1020, respectively,
positional relation therebetween is known. The data representing
the positional relation may be stored in advance in GPS receiver
400, or may be contained in the signal from transmitting apparatus
1100.
[0118] Receiving the positioning signals, GPS receiver 400 executes
the process for calculating the information representing position,
based on these signals. GPS receiver 400 can specify sources of
transmission based on the data representing the positional relation
between the sources of transmission. Thus, GPS receiver 400 can
readily specify the position of itself.
[0119] In the system in accordance with the present embodiment,
transmitting apparatus 1100 and repeaters 1200-1 and 1200-2 are
connected by network 1030. The manner of connection, however, is
not limited and, by way of example, repeaters 1200-1 and 1200-2 may
have a function of receiving radio waves. In that case, wireless
connection is established between each of transmitting apparatus
1100 and repeaters 1200-1 and 1200-2. Specifically, as in the first
embodiment, repeaters 1200-1 and 1200-2 can relay radio waves. This
eliminates engineering works to provide network 1030, and hence,
the system for transmitting positioning signals can be formed
quickly. Further, physical restriction related to the location of
installing network and the like can be eased, and hence, flexible
implementation of the system becomes possible. As a result, it
becomes possible to provide positional information over a wide
range to the user of GPS receiver 400.
[0120] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
[0121] The present invention is, when implemented in space,
applicable to a system including a plurality of artificial
satellites having an apparatus transmitting a signal for
positioning and an apparatus for sending the signal. The present
invention is, when implemented on the ground, applicable to a
system including a plurality of repeaters connected to a
communication network such as the Internet.
[0122] Although the present invention has been described and
illustrated in detail, it is clearly understood that the same is by
way of illustration and example only and is not to be taken by way
of limitation, the spirit and scope of the present invention being
limited only by the terms of the appended claims.
* * * * *