JP2007292698A - Positioning device, method of controlling positioning device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning device or the like that can position accurately after verifying precision of a phase of a positioning foundation sign under a weak electric field in which signal intensity is weak. <P>SOLUTION: The positioning device 20 for positioning a current position by receiving the positioning foundation sign from a transmitting source comprises: a phase calculation means for calculating the phase of the positioning foundation sign by performing correlation processing of a replica positioning foundation sign generated by the positioning device 20 and the positioning foundation sign; a prediction phase calculation means for calculating a prediction phase by predicting a current phase based on the phase during prior positioning, Doppler shift of frequency of an electric wave mounting the positioning foundation sign, and an elapsed time from the prior positioning time; a phase difference evaluation means for determining whether the phase difference between the current phase and the prediction phase is within a previously specified phase difference allowable range; and a positioning means for positioning the current position by using the phase within the phase difference allowable change. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positioning device that uses radio waves from a transmission source, a positioning device control method, a control program therefor, and a recording medium.

Conventionally, a positioning system that measures the current position of a GPS receiver by using, for example, a GPS (Global Positioning System) that is a satellite navigation system has been put into practical use.
This GPS receiver uses radio waves from GPS satellites (hereinafter referred to as satellite radio waves) based on navigation messages (including approximate satellite orbit information: almanac, precision satellite orbit information: ephemeris, etc.) indicating the orbits of GPS satellites. A C / A (Clear and Acquisition or Coarse and Access) code, which is one of pseudo noise codes (hereinafter referred to as PN (Psuedo random noise code) codes), is received. The C / A code is a code that is the basis of positioning.
The GPS receiver specifies the GPS satellite from which the C / A code is transmitted, and, for example, based on the phase (code phase) of the C / A code, receives the GPS satellite and the GPS reception. The distance of the machine (pseudo distance) is calculated. Then, the GPS receiver measures the position of the GPS receiver based on the pseudoranges of three or more GPS satellites and the position of each GPS satellite on the satellite orbit. For example, the C / A code has a bit rate of 1.023 Mbps and the code length is 1,023 chips. Therefore, it can be considered that the C / A code runs side by side at intervals of about 300 kilometers (km), which is the distance traveled by radio waves in 1 millisecond (ms). Therefore, by calculating the number of C / A codes between the GPS satellite and the GPS receiver from the position of the GPS satellite on the satellite orbit and the approximate position of the GPS receiver, the pseudo distance is calculated. Can do. More specifically, one period (1,023 chips) of the C / A code (the integer part of the C / A code) is calculated, and the phase of the C / A code (the fractional part of the C / A code) is calculated. If specified, the pseudo distance can be calculated. Here, the integer part of the C / A code can be estimated if the approximate position of the GPS receiver has a certain accuracy, for example, within 150 km. For this reason, the GPS receiver can calculate the pseudorange by specifying the phase of the C / A code.
The GPS receiver, for example, calculates the correlation between the received C / A code and the replica C / A code generated inside the GPS receiver and integrates the C / A code when the correlation integrated value reaches a certain level. Specify the phase of the code. At this time, the GPS receiver performs correlation processing while shifting the phase and frequency of the replica C / A code.
However, if the radio wave intensity of the satellite radio wave carrying the C / A code is weak, sufficient signal intensity cannot be obtained, and it becomes difficult to specify the phase of the C / A code.
On the other hand, a technique has been proposed in which results of processing received signal segments are combined coherently (synchronously) continuously until a threshold signal-to-noise ratio (SNR) is achieved (for example, Patent Documents). 1).
Japanese translation of PCT publication No. 2004-501352

However, since the GPS satellite and the GPS receiver move relative to each other, the arrival frequency of the satellite radio wave reaching the GPS receiver changes due to the Doppler shift.
Here, when the signal strength is weak, it may be difficult to synchronize the synchronization frequency on the GPS receiver side with the arrival frequency that continuously changes.
When the synchronization frequency on the GPS receiver side deviates from the arrival frequency, even if the correlation integrated value reaches a certain level, the accuracy of the phase of the C / A code at that time deteriorates. For this reason, when positioning is performed using the phase, there is a problem that the accuracy of the positioning position may deteriorate.

  Accordingly, the present invention provides a positioning device, a positioning device control method, a control program thereof, and a recording method capable of accurately positioning after verifying the accuracy of the phase of the positioning basic code in a weak electric field with weak radio field strength. The purpose is to provide a medium.

  According to the first invention, the object is a positioning device that measures a current position based on a positioning basic code from a transmission source, and includes a replica positioning basic code generated by the positioning device and the positioning basic code. Phase calculating means for calculating the phase of the positioning basic code by performing correlation processing, the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the elapsed time from the previous positioning Based on the predicted phase calculation means for calculating the predicted phase by predicting the current phase, and determining whether or not the phase difference between the current phase and the predicted phase is within a predefined phase difference tolerance range. This is achieved by a positioning device comprising: phase difference evaluation means; and positioning means for positioning a current position using the phase corresponding to the phase difference within the phase difference tolerance range.

According to the configuration of the first aspect of the invention, since the positioning device has the phase difference evaluation means, it can determine whether or not the phase difference is within the phase difference allowable range. That is, the positioning device can verify the accuracy of the phase.
Further, since the positioning device has the positioning means, the current position can be measured using the phase corresponding to the phase difference within the phase difference allowable range.
As a result, the positioning device can accurately measure the position of the positioning basic code after verifying the accuracy of the phase of the positioning basic code under a weak electric field with weak radio field intensity.

  According to a second invention, in the configuration of the first invention, a reception frequency specifying means for specifying a reception frequency when receiving a radio wave carrying the positioning basic code, the reception frequency at the time of previous positioning, and the current reception A frequency difference evaluation means for determining whether or not a frequency difference from a frequency is within a predetermined frequency difference allowable range; and a phase of the positioning basic code corresponding to the frequency difference outside the frequency difference allowable range is excluded from positioning. And a phase exclusion means.

According to the configuration of the second invention, since the positioning device has the phase exclusion means, the phase of the positioning basic code corresponding to the frequency difference outside the allowable frequency difference range can be excluded from positioning. .
This means that the positioning device can verify not only the accuracy of the phase of the positioning basic code but also the accuracy of the reception frequency when the phase is calculated. The higher the accuracy of the reception frequency, the higher the accuracy of the phase.
As a result, the positioning device can perform positioning more accurately after verifying the phase accuracy of the positioning basic code in a weak electric field with weak radio field intensity.

  According to a third aspect of the present invention, in any one of the first and second aspects, the phase calculating unit calculates the phase using a plurality of frequency sequences, and the phase difference An evaluation means is a positioning device characterized by determining whether or not the phase calculated in the frequency sequence having the highest signal strength of the positioning basic code is within the phase difference tolerance range. is there.

According to the configuration of the third invention, the phase calculating means is configured to calculate the phase using a plurality of frequency sequences. The accuracy of the reception frequency of any one of the frequency sequences should be higher than the accuracy of the reception frequency of the other frequency sequences. For this reason, the positioning device is highly likely to be able to calculate the phase at the highly accurate reception frequency.
Here, in general, it can be estimated that the accuracy of the reception frequency in the frequency series having the highest signal strength is the most reliable. For this reason, in general, it can be estimated that the phase calculated in the frequency sequence having the highest signal strength is higher in accuracy than the phases of the other frequency sequences.
However, particularly under a weak electric field, the accuracy of the reception frequency in the frequency series having the highest signal strength is not always the highest in reliability.
In this regard, according to the configuration of the third invention, the accuracy of the phase calculated in the frequency sequence having the largest signal strength of the positioning basic code can be verified and excluded from positioning. It is possible to prevent calculation of a positioning position with low accuracy under a weak weak electric field.

  According to a fourth invention, in the configuration of the third invention, the plurality of frequency sequences are separated from each other by a predetermined frequency interval, and the allowable frequency difference range is defined by a threshold value less than the frequency interval. This is a positioning device.

According to the configuration of the fourth invention, when the frequency sequence having the largest signal strength is switched, the phase at that time can be excluded from positioning. This means that the frequency sequence having the largest signal strength is a condition for using the phase for positioning.
As a result, the phase calculated in the frequency sequence that best follows the Doppler shift of the frequency of the radio wave reaching the positioning device can be used for positioning. Therefore, it is possible to measure the position with higher accuracy.

A fifth invention is a positioning device according to any one of the first to fourth inventions, wherein the transmission source is an SPS (Satellite Positioning System) satellite.

According to the sixth aspect of the present invention, the positioning device that measures the current position based on the positioning basic code from the transmission source performs correlation processing between the replica positioning basic code generated by the positioning device and the positioning basic code. Performing a phase calculation step of calculating the phase of the positioning basic code by performing the positioning, the positioning device, the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and from the previous positioning A predicted phase calculating step for calculating a predicted phase by predicting the current phase based on the elapsed time of the phase, and the positioning device accepts a phase difference that the phase difference between the current phase and the predicted phase is predetermined. A phase difference evaluation step for determining whether or not the phase difference is within a range; and a positioning step in which the positioning device measures the current position using the phase corresponding to the phase difference within the phase difference tolerance range. You Is achieved by the control method of the positioning apparatus, characterized in that.

  According to the seventh aspect of the present invention, there is provided a positioning device for positioning a current position on the basis of a positioning basic code from a transmission source, a replica positioning basic code generated by the positioning device, and the positioning basic code. A phase calculating step for calculating the phase of the positioning basic code by performing correlation processing of the positioning, the positioning device, the phase at the time of the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the previous time Based on the elapsed time from the time of positioning, a predicted phase calculating step for calculating the predicted phase by predicting the current phase, and the positioning device defines a phase difference between the current phase and the predicted phase in advance. A phase difference evaluation step for determining whether or not the phase difference is within an allowable range; and a positioning step in which the positioning device measures the current position using the phase corresponding to the phase difference within the phase difference allowable range. Tsu and up, the achieved by a control program for the positioning apparatus, characterized in that to the effective.

According to an eighth aspect of the present invention, there is provided a positioning device for positioning a current position based on a positioning basic code from a transmission source, a replica positioning basic code generated by the positioning device, and the positioning basic code according to an eighth invention. A phase calculating step for calculating the phase of the positioning basic code by performing correlation processing of the positioning, the positioning device, the phase at the time of the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, A predicted phase calculating step for calculating a predicted phase by predicting the current phase based on an elapsed time from the positioning; and the positioning device defines a phase difference between the current phase and the predicted phase in advance. A phase difference evaluation step for determining whether or not the phase difference is within an allowable range; and a positioning step in which the positioning device measures the current position using the phase corresponding to the phase difference within the phase difference allowable range. Tsu and up, is accomplished by a computer-readable recording medium a control program of the positioning device, characterized in that for effective the.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

FIG. 1 is a schematic diagram illustrating a terminal 20 and the like according to the embodiment of this invention.
As shown in FIG. 1, the terminal 20 is a positioning satellite such as, for example, GPS (Global Positioning System) satellites 12a, 12b, 12c, 12d, 12e, 12f, 12g, and 12h from radio waves S1, S2, S3, S4. S5, S6, S7 and S8 can be received. The GPS satellite 12a or the like is an example of a transmission source. The source may be any SPS (Satellite Positioning System) satellite, and is not limited to a GPS satellite.
Various codes (codes) are carried on the radio wave S1 and the like. One of them is the C / A code Sca. The C / A code Sca is a signal having a bit rate of 1.023 Mbps and a bit length of 1,023 bits (= 1 msec). The C / A code Sca is composed of 1,023 chips. The terminal 20 is an example of a positioning device that measures the current position, and performs positioning of the current position using the C / A code. This C / A code Sca is an example of a positioning basic code.

  Moreover, there are almanac Sal and ephemeris Seh as information put on the radio wave S1 and the like. Almanac Sal is information indicating the approximate satellite orbit of all the GPS satellites 12a and the like, and Ephemeris Seh is information indicating the precise satellite orbit of each of the GPS satellites 12a and the like. Almanac Sal and Ephemeris Seh are collectively called navigation messages.

  The terminal 20 can determine the current position by specifying the phases of C / A codes from, for example, three or more different GPS satellites 12a.

FIG. 2 is a conceptual diagram illustrating an example of a positioning method.
As shown in FIG. 2, for example, it can be considered that C / A codes are continuously arranged between the GPS satellite 12 a and the terminal 20. Since the distance between the GPS satellite 12a and the terminal 20 is not necessarily an integer multiple of the length of the C / A code (300 kilometers (km)), the code fractional part C / Aa exists. That is, between the GPS satellite 12a and the terminal 20, there are a part that is an integral multiple of the C / A code and a fractional part. The total length of the integral multiple of the C / A code and the fractional part is the pseudorange. The terminal 20 performs positioning using pseudoranges for three or more GPS satellites 12a and the like.
In this specification, the fractional part C / Aa of the C / A code is called a code phase. For example, the code phase can be indicated by the number of the 1023 chip of the C / A code, or can be indicated in terms of distance. When calculating the pseudo distance, the code phase is converted into a distance.

The position of the GPS satellite 12a in the orbit can be calculated using the ephemeris Seh. For example, if a distance between the position of the GPS satellite 12a in the orbit and an initial position Q0 described later is calculated, a portion that is an integral multiple of the C / A code can be specified. Since the length of the C / A code is 300 kilometers (km), the position error of the initial position Q0 needs to be within 150 kilometers (km).

Then, as shown in FIG. 2, the correlation process is performed while moving the phase of the replica C / A code in the direction of the arrow X1, for example. At this time, the terminal 20 performs correlation processing while changing the synchronization frequency. This correlation process includes a coherent process and an incoherent process which will be described later.
The phase at which the correlation integrated value is maximized is the code fraction C / Aa.
Note that, unlike the present embodiment, the terminal 20 may perform positioning using, for example, radio waves from a mobile phone communication base station. Further, unlike the present embodiment, the terminal 20 may perform positioning by receiving radio waves from a LAN (Local Area Network).

FIG. 3 is an explanatory diagram of the correlation processing.
Coherent is a process for correlating the C / A code received by the terminal 20 and the replica C / A code. The replica C / A code is a code generated by the terminal 20. The replica C / A code is an example of a replica positioning basic code.
For example, as shown in FIG. 3, if the coherent time is 10 msec, a correlation value between the C / A code and the replica C / A code that are synchronously integrated in the time of 10 msec is calculated. As a result of the coherent processing, a correlated phase (code phase) and a correlation value are output.
Incoherent is a process of calculating a correlation integrated value (incoherent value) by integrating the correlation values of coherent results.
As a result of the correlation process, the code phase output by the coherent process and the correlation integrated value are output.

FIG. 4 is a diagram illustrating an example of the relationship between the correlation integrated value and the code phase.
The code phase CP1 corresponding to the maximum correlation integrated value Pmax in FIG. 4 is the code phase of the replica C / A code, that is, the code phase of the C / A code.
Then, for example, the terminal 20 sets the correlation integrated value having the smaller correlation integrated value in the code phase separated by a half chip from the code phase CP1 as the noise integrated correlation value Pnoise.
The terminal 20 defines the value obtained by dividing the difference between Pmax and Pnoise by Pmax as the signal strength XPR. The signal strength XPR is an example of signal strength.
Then, when the XPR is, for example, 0.2 or more, the terminal 20 sets the code phase CP1 as a code phase candidate to be used for positioning. Hereinafter, this code phase is referred to as a “candidate code phase”. The candidate code phase is a candidate used for positioning, and the terminal 20 is not always used for positioning.

5 and 6 are diagrams showing an example of the relationship between the candidate code phase and the passage of time.
FIG. 5 shows a state where the GPS satellite 12a is approaching the terminal 20, for example.
When the GPS satellite 12a approaches the terminal 20, the distance between the GPS satellite 12a and the terminal 20 becomes short, so that the candidate code phase C1 approaches 0 with time.
Also, the synchronization frequency F1 is set to increase with time. This is to cope with an increase in the arrival frequency when the radio wave S1 reaches the terminal 20 due to the Doppler shift caused by the GPS satellite 12a approaching the terminal 20.

The terminal 20 uses, for example, three frequency sequences F1, F2, and F3 as shown in FIG. 6 in order to efficiently synchronize with the changing arrival frequency. The frequency series F1 and the like are examples of frequency series. The frequency series F1 and F2 are separated by a frequency width of 50 hertz (Hz). Further, the frequency series F1 and F3 are separated by a frequency width of 50 hertz (Hz). The frequency interval of 50 hertz (Hz) is defined in advance. That is, the frequency interval of 50 hertz (Hz) is an example of the frequency interval. This frequency interval is defined within a frequency search step interval in the correlation processing performed by the terminal 20. For example, if the frequency search step interval is 100 hertz (Hz) (see FIG. 11B), the frequency search is defined to be less than 100 hertz (Hz).
Note that there may be a plurality of frequency series F1 and the like, and unlike this embodiment, for example, four or more may be used.
As shown in FIG. 6, each frequency series F <b> 1 and the like are set so as to change with the passage of time in anticipation of the Doppler shift of the arrival frequency.
Any one of the frequency series F1 and the like should follow the Doppler shift of the arrival frequency with the highest accuracy.

In the frequency series F1, the code phase C1 is calculated. Then, the code phase C2 is calculated in the frequency series F2. Then, the code phase C3 is calculated in the frequency sequence F3.
Thus, although the three code phases C1 and the like are calculated in parallel, it can be assumed that the candidate code phase calculated with the highest signal strength XPR has the highest reliability.
However, the frequency series F1 or the like having the highest XPR is not always maintained. For example, as shown in FIG. 6, for example, the XPR of the candidate code phase C1 calculated in the frequency sequence F1 is highest between the times t1 and t2, and is calculated in the frequency sequence F2 between the times t2 and t3. The candidate code phase C2 has the highest XPR.
Since the frequency of each frequency sequence F1 or the like is changed based on the expected Doppler shift, the candidate code phase calculated in any one frequency sequence is continuously calculated in another frequency sequence. Should be more accurate than the candidate code phase. In other words, for example, the frequency series F1 should keep following the actual arrival frequency with the highest accuracy as compared with the other frequency series F2 and F3.
For this reason, when the frequency sequence changes with the passage of time, the candidate code phase calculated with a high XPR is not always the highest in accuracy.
In this regard, the terminal 20 can perform positioning with high accuracy after verifying the accuracy of the candidate code phase under the weak electric field by the following hardware configuration and software configuration.

(Main hardware configuration of terminal 20)
FIG. 7 is a schematic diagram showing a main hardware configuration of the terminal 20.
As illustrated in FIG. 7, the terminal 20 includes a computer, and the computer includes a bus 22. A CPU (Central Processing Unit) 24, a storage device 26, and the like are connected to the bus 22. The storage device 26 is, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), or the like.
In addition, an input device 28, a power supply device 30, a GPS device 32, a display device 34, a communication device 36, and a clock 38 are connected to the bus 22.

(About the configuration of the GPS device 32)
FIG. 3 is a schematic diagram showing the configuration of the GPS device 32.
As shown in FIG. 3, the GPS device 32 includes an RF unit 32a and a baseband unit 32b.
The RF unit 32a receives the radio wave S1 and the like with the antenna 33a. Then, the LNA 33b as an amplifier amplifies a signal such as a C / A code carried on the radio wave S1. Then, the mixer 33c down-converts the signal frequency. Then, the quadrature (IQ) detector 33d performs IQ separation on the signal. Subsequently, the A / D converters 33e1 and 33e2 are configured to convert the IQ-separated signals into digital signals, respectively.

  The baseband unit 32b is configured to receive a signal converted into a digital signal from the RF unit 32a, sample and accumulate the signal, and correlate with the C / A code held by the baseband unit 32b. Has been. The baseband unit 32b has, for example, 128 correlators (not shown) and accumulators (not shown), and can perform correlation processing at 128 phases simultaneously. The correlator is configured to perform the above-described coherent processing. The accumulator is configured to perform the incoherent process described above.

(About main software configuration of terminal 20)
FIG. 9 is a schematic diagram illustrating a main software configuration of the terminal 20.
As illustrated in FIG. 9, the terminal 20 includes a control unit 100 that controls each unit, a GPS unit 102 that corresponds to the GPS device 32 in FIG. 7, a clock unit 104 that corresponds to the clock 38, and the like.
The terminal 20 also includes a first storage unit 110 that stores various programs and a second storage unit 150 that stores various information.

As illustrated in FIG. 9, the terminal 20 stores a navigation message 152 in the second storage unit 150. The navigation message 152 includes an almanac 152a and an ephemeris 152b.
The terminal 20 uses the almanac 152a and the ephemeris 152b for positioning.

  As illustrated in FIG. 9, the terminal 20 stores initial position information 154 in the second storage unit 150. The initial position Q0 is, for example, the previous positioning position.

As illustrated in FIG. 9, the terminal 20 stores an observable satellite calculation program 112 in the first storage unit 110. The observable satellite calculation program 112 is a program for the control unit 100 to calculate the observable GPS satellites 12a and the like with reference to the initial position Q0 indicated by the initial position information 154.
Specifically, the control unit 100 refers to the almanac 152a to determine the GPS satellites 12a and the like that can be observed at the current time measured by the time measuring unit 104. The control unit 100 stores observable satellite information 156 indicating the observable GPS satellites 12 a and the like (hereinafter referred to as “observable satellites”) in the second storage unit 150. In the present embodiment, the observable satellites are GPS satellites 12a to 12h (see FIGS. 1 and 9).

As illustrated in FIG. 9, the terminal 20 stores an estimated frequency calculation program 114 in the first storage unit 110. The estimated frequency calculation program 114 is a program for the control unit 100 to estimate the reception frequency of the radio wave S1 or the like from the GPS satellite 12a or the like.
This reception frequency is an arrival frequency when the radio wave S1 reaches the terminal 20. More specifically, this reception frequency is an intermediate (IF) frequency when the radio wave S1 reaches the terminal 20 and is further down-converted in the terminal 20.

FIG. 10 is an explanatory diagram of the estimated frequency calculation program 114.
As shown in FIG. 10, the control unit 100 calculates the estimated frequency A by adding the Doppler shift H2 to the transmission frequency H1 from the GPS satellite 12a or the like. The transmission frequency H1 from the GPS satellite 12a or the like is known, for example, 1,575.42 MHz.
The Doppler shift H <b> 2 is caused by relative movement between each GPS satellite 12 a and the terminal 20. The control unit 100 calculates the line-of-sight speed (speed relative to the direction of the terminal 20) of each GPS satellite 12a and the like at the current time based on the ephemeris 152b and the initial position Q0. Then, the Doppler shift H2 is calculated based on the line-of-sight speed.
The control unit 100 calculates the estimated frequency A for each GPS satellite 12a that is an observable satellite.
The estimated frequency A includes an error corresponding to a drift of the clock (reference oscillator: not shown) of the terminal 20. Drift is a change in oscillation frequency due to a temperature change.
For this reason, the control unit 100 searches for the radio wave S1 and the like at a frequency having a predetermined width with the estimated frequency A as the center. For example, the radio wave S1 and the like are searched for at a frequency of every 100 Hz in a frequency range from (A-100) kHz to (A + 100) kHz.

  As illustrated in FIG. 9, the terminal 20 stores a measurement calculation program 116 in the first storage unit 110. The measurement calculation program 116 performs a correlation process between the C / A code received from the GPS satellite 12a and the like by the control unit 100 and the replica C / A code generated by the terminal 20, so that the maximum correlation integrated value Pmax, noise Is a program for calculating a measurement including a correlation integrated value Pnoise, a candidate code phase, and a reception frequency. The measurement calculation program 116 and the control unit 100 are an example of a phase calculation unit and an example of a reception frequency specifying unit.

FIG. 11 is an explanatory diagram of the measurement calculation program 116.
As shown in FIG. 11A, the control unit 100 performs correlation processing by dividing one chip of the C / A code, for example, at equal intervals by the baseband unit 32b. One chip of the C / A code is divided into, for example, 32 equal parts. That is, the correlation processing is performed at the phase width (first phase width W1) interval of 1/32 chips. And the phase of 1st phase width W1 space | interval when the control part 100 performs a correlation process is called 1st sampling phase SC1.
The first phase width W1 is defined as a phase width that can detect the maximum correlation value Pmax when the signal intensity when the radio wave S1 or the like reaches the terminal 20 is −155 dBm or more. It has been clarified by simulation that the maximum correlation value Pmax can be detected even with a weak electric field if the signal intensity is −155 dBm or more if the phase width is 1/32 chip.

As shown in FIG. 11B, the control unit 100 performs correlation processing while shifting the frequency range of ± 100 kHz around the estimated frequency A by the first phase width w1. At this time, correlation processing is performed while shifting the frequency by 100 Hz.
As shown in FIG. 11C, the baseband unit 32b outputs the correlation value integration P corresponding to the phases C1 to C64 for two chips. Each of the phases C1 to C64 is the first sampling phase SC1.

Based on the measurement calculation program 116, the control unit 100 searches, for example, from the first chip to the 1,023 chip of the C / A code.
The control unit 100 calculates XPR based on Pmax and Pnoise, and sets the code phase CP1, the reception frequency f1, Pmax1, and Pnoise1 corresponding to the state with the largest XPR as the current measurement information 160. The code phase CP1, the reception frequency f1, Pmax1, and Pnoise1 are collectively referred to as measurement. The terminal 20 calculates a measurement for each GPS satellite 12a and the like.
The code phase CP1 is converted into a distance. As described above, since the code length of the C / A code is, for example, 300 kilometers (km), the code phase that is a fractional part of the C / A code can also be converted into a distance.

The control unit 100 calculates a measurement for each of, for example, six GPS satellites 12a among the observable satellites. Note that a measurement for the same GPS satellite 12a or the like is called a corresponding measurement. For example, the code phase CP1 for the GPS satellite 12a and the frequency f1 for the GPS satellite 12a are the corresponding measurements. The frequency f1 is a reception frequency when the radio wave S1 from the GPS satellite 12a is received.
Unlike this embodiment, a narrow correlator (see, for example, Japanese Patent Laid-Open No. 2000-31163) may be employed as a correlation processing method.

As illustrated in FIG. 9, the terminal 20 stores a measurement storage program 118 in the first storage unit 110. The measurement storage program 118 is a program for the control unit 100 to store the measurement in the second storage unit 150.
The control unit 100 stores the new measurement as the current measurement information 160 in the second storage unit 150 and stores the existing current measurement information 160 as the previous measurement information 162 in the second storage unit 150. The previous measurement information 162 includes a code phase CP0, frequencies f0, Pmax0, and Pnoise0 at the time of previous positioning.

As illustrated in FIG. 9, the terminal 20 stores a frequency evaluation program 120 in the first storage unit 110. The frequency evaluation program 120 is a program for the control unit 100 to determine whether or not the frequency difference between the reception frequency f0 at the previous positioning and the reception frequency f1 at the current positioning is within the frequency threshold α. The range within the frequency threshold α is defined in advance by a threshold less than the frequency interval of the frequency series F1, F2, and F3. As described above, when the frequency interval is 50 hertz (Hz), the frequency threshold value α is, for example, 30 hertz (Hz).
The frequency evaluation program 120 and the control unit 100 described above are examples of frequency difference evaluation means. The range within the frequency threshold value α is an example within the frequency difference allowable range defined in advance.

As illustrated in FIG. 9, the terminal 20 stores a prediction code phase calculation program 122 in the first storage unit 110. In the prediction code phase calculation program 122, the control unit 100 predicts the current phase based on the code phase CP0 at the previous positioning, the Doppler shift of the radio wave S1 and the elapsed time dt from the previous positioning. This is a program for calculating a prediction code phase Cpe. The prediction code phase CPe is an example of a prediction phase. The prediction code phase calculation program 122 and the control unit 100 are an example of a prediction phase calculation unit.
Note that the prediction code phase Cpe is converted into a distance.

FIG. 12 is an explanatory diagram of the prediction code phase calculation program 122.
As illustrated in FIG. 12, the control unit 100 calculates the prediction code phase CPe using Equation 1, for example.
As shown in Equation 1, the control unit 100 subtracts, for example, a value obtained by multiplying the relative movement speed of the GPS satellite 12a and the terminal 20 by the elapsed time dt from the previous positioning from the code phase CP0 at the previous positioning. To calculate the prediction code phase CPe.
In Equation 1, the prediction code phase CPe and the previous code phase CP0 are converted into distances.

  Here, the radio waves S1 and the like propagate at the speed of light. Therefore, by dividing the speed of light by the transmission frequency H1 such as the radio wave S1, an approximate speed corresponding to a Doppler shift of 1 hertz (Hz) can be calculated. That is, a Doppler shift of plus (+) 1 hertz (Hz) means that the GPS satellite 12a is approaching the terminal 20 at a speed of 0.19 meters per second (m / s). For this reason, the prediction code phase CPe is shorter than the code phase CP0 at the time of the previous positioning. Here, the Doppler shift is, for example, the difference between the frequency f0 at the previous positioning and the transmission frequency H1.

On the other hand, the fact that the Doppler shift is minus (−) 1 hertz (Hz) means that the GPS satellite 12a is moving away from the terminal 20 at a speed of 0.19 meters per second (m / s). For this reason, the prediction code phase CPe is longer than the code phase CP0 at the previous positioning.
Equation 1 is satisfied under the condition that the elapsed time from the previous positioning is short. In other words, Equation 1 holds as long as the relationship between the code phase and the elapsed time can be shown as a straight line on the graph.
Also, unlike the present embodiment, the average value of the difference between the frequency f0 at the previous positioning and the transmission frequency H1 and the difference between the frequency f1 at the current positioning and the transmission frequency H1 may be used as the Doppler shift. . As a result, the prediction code phase CPe can be calculated more accurately.

  The control unit 100 stores prediction code phase information 164 indicating the calculated prediction code phase Cpe in the second storage unit 150.

As illustrated in FIG. 9, the terminal 20 stores a code phase evaluation program 124 in the first storage unit 110. The code phase evaluation program 124 allows the control unit 100 to determine whether or not the code phase difference between the current code phase CP1 and the predicted code phase CPe is less than or equal to the code phase threshold β (hereinafter referred to as “threshold β”). It is a program. The range below the threshold β is an example within the phase difference allowable range. The code phase evaluation program 124 and the control unit 100 are an example of a phase difference evaluation unit.
The threshold value β is defined in advance. The threshold value β is, for example, 80 meters (m).
The control unit 100 sets the code phase CP1 determined to be a frequency difference equal to or less than the threshold value α by the frequency evaluation program 120 described above as a determination target based on the code phase evaluation program 124.

As illustrated in FIG. 9, the terminal 20 stores a positioning use code phase determination program 126 in the first storage unit 110. In the positioning use code phase determination program 126, the control unit 100 determines the code phase CP1 and the like of the GPS satellite 12a that has a frequency difference within the frequency threshold α and is a code phase difference equal to or less than the threshold β. It is a program for determining as phase CP1f.
The code phase CP1 or the like of the GPS satellite 12a or the like corresponding to the frequency difference that is not within the frequency threshold value α is not determined as the positioning use code phase CP1f, and is excluded from the positioning. The code phase CP1 corresponding to the frequency difference within the frequency threshold α and corresponding to the code phase difference equal to or less than the threshold β is used for positioning. That is, the positioning use code phase determination program 126 and the control unit 100 are examples of phase exclusion means.
In the present embodiment, the positioning use code phase CP1f is, for example, CP1fa, CP1fb, CP1fc, and CP1fd corresponding to the GPS satellites 12a, 12b, 12c, and 12d, respectively.
The control unit 100 stores the positioning use code phase information 166 indicating the positioning use code phase CP1f in the second storage unit 150.

As illustrated in FIG. 9, the terminal 20 stores a positioning program 128 in the first storage unit 110. The positioning program 128 is a program for the control unit 100 to measure the current position using the positioning use code phase CP1f. The positioning program 128 and the control unit 100 are examples of positioning means.
The positioning use code phase CP1f is the code phase CP1 or the like within the above-described threshold β. That is, positioning the current position using the positioning use code phase CP1f is synonymous with positioning the current position using the code phase CP1 or the like within the threshold β.
When there are three or more positioning use code phases CP1f, the control unit 100 uses the positioning use code phases CP1f to measure the current position and calculates a positioning position Q1.
The control unit 100 stores positioning position information 168 indicating the calculated positioning position Q1 in the second storage unit 150.

  As illustrated in FIG. 9, the terminal 20 stores a positioning position output program 130 in the first storage unit 110. The positioning position output program 130 is a program for the control unit 100 to display the positioning position Q1 on the display device 34 (see FIG. 7).

The terminal 20 is configured as described above.
The terminal 20 can determine whether or not the code phase difference between the current code phase CP1 and the predicted code phase CPe is equal to or less than a predetermined threshold value β. For this reason, the terminal 20 can verify the accuracy of the code phase CP1.
Further, the terminal 20 can determine the current position using the code phase CP1 corresponding to the code phase difference equal to or less than the threshold value β.
Thereby, the terminal 20 can perform positioning with high accuracy in a weak electric field with weak signal strength after verifying the accuracy of the code phase of the positioning basic code.

Further, the terminal 20 can exclude the code phase CP1 corresponding to the frequency f1 outside the range within the frequency threshold α from the positioning.
This means that the terminal 20 can verify not only the accuracy of the code phase CP1 of the C / A code but also the accuracy of the reception frequency f1 when the code phase CP1 is calculated.
Accordingly, the terminal 20 can perform positioning with higher accuracy after verifying the accuracy of the code phase of the positioning basic code under a weak electric field with a weak signal strength.

The above is the configuration of the terminal 20 according to the present embodiment. Hereinafter, an example of the operation will be described mainly using FIG.
FIG. 13 is a schematic flowchart showing an operation example of the terminal 20.

First, the terminal 20 receives the radio wave S1 and calculates the measurement (step ST1 in FIG. 13). This step ST1 is an example of a phase calculation step.
Subsequently, the terminal 20 stores the measurement (step ST2).
Subsequently, the terminal 20 determines whether or not the absolute value of the frequency difference between the current frequency f1 and the previous frequency f0 is equal to or less than the frequency threshold value α (step ST3).

  The terminal 20 does not use the code phase CP1 corresponding to the frequency difference determined not to be equal to or less than the frequency threshold α in step ST3 for positioning (step ST9). That is, the positioning use code phase CP1f is not set.

  On the other hand, for the code phase CP1 corresponding to the frequency difference determined to be equal to or less than the frequency threshold value α in step ST3, the corresponding prediction code phase CPe is calculated (step ST4). This step ST4 is an example of a predicted phase calculating step.

Subsequently, the terminal 20 determines whether or not the absolute value of the code phase difference between the code phase CP1 and the prediction code phase CPe is equal to or less than a threshold value β (step ST5). This step ST5 is an example of a phase evaluation step. The terminal 20 sets the code phase CP1 determined that the absolute value of the code phase difference is equal to or less than the threshold value β as the positioning use code phase CP1f.
Subsequently, the terminal 20 determines whether or not there are three or more positioning use code phases CP1f (step ST6).
In step ST6, when the terminal 20 determines that the positioning use code phase CP1f is less than three, since the positioning is impossible, the terminal 20 is terminated without positioning.

On the other hand, if the terminal 20 determines in step ST6 that there are three or more positioning use code phases CP1f, the terminal 20 performs positioning using the positioning use code phase CP1f (step ST7). This step ST7 is an example of a positioning step.
Subsequently, the terminal 20 outputs a positioning position Q1 (see FIG. 9) (step ST8).

  Through the above steps, the terminal 20 can perform positioning with high accuracy after verifying the accuracy of the phase of the positioning basic code under a weak electric field with weak signal strength.

  The present invention is not limited to the embodiments described above.

It is the schematic which shows the terminal etc. of embodiment of this invention. It is a conceptual diagram which shows the positioning method. It is explanatory drawing of a correlation process. It is a figure which shows an example of the relationship between a correlation integrated value and a code phase. It is a figure which shows an example of the relationship between a candidate code phase and time passage. It is a figure which shows an example of the relationship between a candidate code phase and time passage. It is the schematic which shows the main hardware constitutions of a terminal. It is the schematic which shows an example of a structure of a GPS apparatus. It is the schematic which shows the main software structures of a terminal. It is explanatory drawing of an estimated frequency calculation program. It is explanatory drawing of a measurement calculation program. It is explanatory drawing of a prediction code phase calculation program. It is a schematic flowchart which shows the operation example of a terminal.

Explanation of symbols

  12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h ... GPS satellite, 20 ... terminal, 32 ... GPS device, 112 ... observable satellite calculation program, 114 ... estimated frequency Calculation program 116 ... Measurement calculation program 118 ... Measurement storage program 120 ... Frequency evaluation program 122 ... Prediction code phase calculation program 124 ... Code phase evaluation program 126 ... Positioning use code phase determination program, 128 ... positioning program, 130 ... positioning position output program

Claims (8)

A positioning device that measures a current position based on a positioning basic code from a transmission source,
Phase calculating means for calculating a phase of the positioning basic code by performing a correlation process between the replica positioning basic code generated by the positioning device and the positioning basic code;
Predicted phase that predicts the current phase based on the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the elapsed time since the previous positioning A calculation means;
A phase difference evaluation means for determining whether or not a phase difference between the current phase and the predicted phase is within a predefined phase difference tolerance range;
Positioning means for positioning the current position using the phase corresponding to the phase difference within the phase difference tolerance;
A positioning device comprising: A receiving frequency specifying means for specifying a receiving frequency when receiving a radio wave carrying the positioning basic code;
A frequency difference evaluation means for determining whether or not a frequency difference between the reception frequency at the time of previous positioning and the current reception frequency is within a predetermined frequency difference tolerance range;
Phase exclusion means for eliminating the phase of the positioning basic code corresponding to the frequency difference outside the frequency difference allowable range from positioning;
The positioning device according to claim 1, comprising: The phase calculation means includes
It is configured to calculate the phase using a plurality of frequency series,
The phase difference evaluation means includes
3. The configuration according to claim 1, wherein the phase calculated in the frequency series having the highest signal strength of the positioning basic code is configured to determine whether or not the phase difference is within an allowable range. A positioning device according to any one of the above. The plurality of frequency sequences are:
Are separated from each other by a predetermined frequency interval,
The positioning device according to claim 3, wherein the frequency difference allowable range is defined by a threshold value less than the frequency interval.   The positioning device according to any one of claims 1 to 4, wherein the transmission source is an SPS (Satellite Positioning System) satellite. A positioning device that measures the current position based on a positioning basic code from a transmission source calculates a phase of the positioning basic code by performing a correlation process between the replica positioning basic code generated by the positioning device and the positioning basic code. A phase calculation step;
The positioning device predicts the current phase based on the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the elapsed time from the previous positioning. A predicted phase calculating step for calculating
A phase difference evaluation step in which the positioning device determines whether or not a phase difference between the current phase and the predicted phase is within a predefined phase difference tolerance;
A positioning step in which the positioning device measures a current position using the phase corresponding to the phase difference within the phase difference tolerance;
A method for controlling a positioning device, comprising: On the computer,
A positioning device that measures the current position based on a positioning basic code from a transmission source calculates a phase of the positioning basic code by performing a correlation process between the replica positioning basic code generated by the positioning device and the positioning basic code. A phase calculation step;
The positioning device predicts the current phase based on the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the elapsed time from the previous positioning. A predicted phase calculating step for calculating
A phase difference evaluation step in which the positioning device determines whether or not a phase difference between the current phase and the predicted phase is within a predefined phase difference tolerance;
A positioning step in which the positioning device measures a current position using the phase corresponding to the phase difference within the phase difference tolerance;
A control program for a positioning device, characterized in that On the computer,
A positioning device that measures the current position based on a positioning basic code from a transmission source calculates a phase of the positioning basic code by performing a correlation process between the replica positioning basic code generated by the positioning device and the positioning basic code. A phase calculation step;
The positioning device predicts the current phase based on the phase at the previous positioning, the Doppler shift of the frequency of the radio wave carrying the positioning basic code, and the elapsed time from the previous positioning. A predicted phase calculating step for calculating
A phase difference evaluation step in which the positioning device determines whether or not a phase difference between the current phase and the predicted phase is within a predefined phase difference tolerance;
A positioning step in which the positioning device measures a current position using the phase corresponding to the phase difference within the phase difference tolerance;
The computer-readable recording medium which recorded the control program of the positioning apparatus characterized by making said effective.

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