JP4595855B2 - POSITIONING DEVICE, POSITIONING DEVICE CONTROL METHOD, POSITIONING DEVICE CONTROL PROGRAM, COMPUTER-READABLE RECORDING MEDIUM CONTAINING POSITIONING DEVICE CONTROL PROGRAM - Google Patents

Description

  The present invention relates to a positioning device that uses radio waves from a positioning satellite, a positioning device control method, a positioning device control program, and a computer-readable recording medium that records the positioning device control program.

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 transmission time and reception time of the C / A code, the GPS satellite and the GPS reception are performed. The distance of the machine (pseudo distance) is calculated. 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 (Japanese Patent Laid-Open No. Hei 10-2010). No. 339772).
The GPS receiver performs code synchronization between the received C / A code and the C / A code of the replica that the GPS receiver has, and a phase indicating the maximum correlation value (hereinafter referred to as a code phase). Is calculated. The GPS receiver can calculate the above-mentioned pseudo distance by using this code phase.
Since the above-mentioned C / A code is carried on the satellite radio wave, in order to perform the above-described code synchronization accurately, the code synchronization, the carrier frequency (IF (intermediate) carrier frequency) of the received satellite radio wave, and GPS reception are required. It is necessary to synchronize the internal frequency of the machine (hereinafter referred to as “frequency synchronization”).
When the signal strength of the satellite radio wave is strong and, for example, a correlation result (coherent result) can be output every short time of 1 millisecond (ms), a PLL (Phase) for correcting the frequency based on the coherent result By configuring a “Locked Loop”, frequency synchronization can be performed (see, for example, paragraph 2003 of Japanese Patent Laid-Open No. 2003-98244).
However, when the strength of the satellite radio wave is weak, frequency synchronization by PLL cannot be performed, and code synchronization cannot be performed.
On the other hand, the expected IF carrier frequency is set in anticipation of the original IF carrier frequency, and the difference in signal level between a frequency higher and lower than the expected IF carrier frequency by a predetermined value is reduced, A technique for bringing the expected IF carrier frequency closer to the true IF carrier frequency has been proposed (for example, Patent Document 1).
JP 2003-255036 A

  In the above-described technique, it is necessary to appropriately determine the expected IF carrier frequency. However, when the signal strength of satellite radio waves is extremely weak, there is a problem that the expected IF carrier frequency may not be appropriately determined.

  Therefore, the present invention provides a positioning device, a positioning device control method, and a positioning device control that can perform positioning accurately without requiring an expected IF carrier frequency when the signal strength of satellite radio waves is extremely weak. It is an object of the present invention to provide a computer-readable recording medium that records a program and a control program for a positioning device.

  According to the first aspect of the present invention, there is provided a positioning device for positioning a current position using a positioning basic code placed on radio waves from a plurality of transmission sources, the replica generated by the positioning device. Peak frequency specifying means for specifying a peak frequency that is a reception frequency corresponding to a maximum value of a correlation value between the positioning basic code and the positioning basic code, a low frequency that is a frequency lower than the peak frequency, and a frequency that is lower than the peak frequency Corresponding to the peak frequency, reference frequency calculating means for calculating a high frequency that is a high frequency, the correlation value corresponding to the low frequency, the reference correlation value calculating means for calculating the correlation value corresponding to the high frequency The correlation value and the peak frequency, the correlation value and the low frequency corresponding to the low frequency, and the correlation value and the high frequency corresponding to the high frequency. And a corrected peak frequency calculating means for calculating the corrected peak frequency, and a radio wave receiving means for receiving the radio wave using the corrected peak frequency. Is done.

According to the configuration of the first invention, since the positioning device has the peak frequency specifying means, the peak frequency can be specified.
In addition, since the positioning device includes the corrected peak frequency calculation unit, the correlation value corresponding to the peak frequency and the first point defined by the peak frequency, the correlation value corresponding to the low frequency, and The corrected peak frequency can be calculated based on three points: the second point defined by the low frequency, the correlation value corresponding to the high frequency, and the third point defined by the high frequency.
When the phase of the replica positioning basic code is fixed, the graph showing the relationship between the correlation value and the reception frequency (IF carrier frequency) is theoretically an isosceles triangle with the point corresponding to the maximum value of the correlation value as a vertex. Draw. And the above-mentioned 1st point is located in the vertex vicinity, and the 2nd point and the 3rd point are each located in a different hypotenuse. Since one of the second point and the third point is located on the same hypotenuse as the first point, the slope of the hypotenuse can be specified. In an isosceles triangle, if the slope of one hypotenuse can be specified, the slope of the other hypotenuse can also be specified. The point where the two hypotenuses intersect is the vertex. The frequency corresponding to this apex is the above-described corrected peak frequency.
As described above, when the signal strength of the satellite radio wave is extremely weak, even if the expected IF carrier frequency cannot be appropriately determined, there is always one peak frequency. If the peak frequency is specified, the corrected peak frequency can be calculated by the corrected peak frequency calculation means without being restricted by the search width of the frequency search.
And since the said positioning apparatus has the said electromagnetic wave receiving means, it can receive the said electromagnetic wave using the said corrected peak frequency. For this reason, the correlation value can be calculated with high accuracy, and the current position can be calculated with high accuracy.
As a result, when the signal strength of the satellite radio wave is extremely weak, positioning can be performed with high accuracy without requiring the expected IF carrier frequency to be determined.

According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, there is provided reception frequency control means for controlling a reception frequency so that a coherent value between the replica positioning basic code and the positioning basic code is maximized. It is a positioning device.
It is.

According to the configuration of the second invention, since the positioning device has the reception frequency control means, the reception frequency is controlled so that the coherent value between the replica positioning basic code and the positioning basic code is maximized. be able to.
Thereby, when the signal intensity of the radio wave is within a predetermined intensity range, the reception frequency can be continuously brought close to the IF carrier frequency of the radio wave.

  According to a third aspect of the present invention, in the configuration of the second aspect of the invention, the corrected peak frequency calculation means and the reception frequency control means operate in parallel.

According to the configuration of the third invention, when the signal strength of the radio wave is larger than a predetermined strength, the reception frequency is controlled so that the coherent value between the replica positioning basic code and the positioning basic code is maximized. It can be performed. Further, when the signal intensity of the radio wave is smaller than a predetermined intensity, the radio wave can be received using the corrected peak frequency.
For this reason, it is possible to perform positioning continuously and accurately when the received intensity shifts from a state larger than a predetermined strength to a small state.

  A fourth invention is a positioning device according to any one of the first to third inventions, wherein the transmission source is a positioning satellite.

  According to the fifth aspect of the present invention, the positioning device for positioning the current position using the positioning basic code placed on the radio waves from the plurality of transmission sources is the replica positioning base generated by the positioning device. A peak frequency specifying step for specifying a peak frequency which is a reception frequency corresponding to a maximum value of a correlation value between a code and the positioning basic code, and a low frequency whose positioning device is a frequency lower than the peak frequency, and A reference frequency calculating step of calculating a high frequency that is higher than a peak frequency, and the positioning device calculates the correlation value corresponding to the low frequency and the correlation value corresponding to the high frequency. And calculating the correlation value and the peak frequency corresponding to the peak frequency, and the correlation value and the low frequency corresponding to the low frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency based on the number, the correlation value corresponding to the high frequency, and the high frequency, and the positioning device uses the corrected peak frequency. And a radio wave receiving step for receiving the radio wave.

  According to the configuration of the fifth invention, as in the configuration of the first invention, when the signal strength of the satellite radio wave is extremely weak, it is possible to perform positioning accurately without requiring the expected IF carrier frequency to be determined. it can.

  According to the sixth aspect of the present invention, the positioning device generates a positioning device for positioning the current position using a positioning basic code placed on radio waves from a plurality of transmission sources. A peak frequency specifying step for specifying a peak frequency which is a reception frequency corresponding to a maximum correlation value between a replica positioning basic code and the positioning basic code; and a low frequency at which the positioning device is a frequency lower than the peak frequency. A reference frequency calculating step for calculating a high frequency that is higher than the peak frequency, and the positioning device calculates the correlation value corresponding to the low frequency and the correlation value corresponding to the high frequency. A reference correlation value calculating step; and the positioning device includes the correlation value and the peak frequency corresponding to the peak frequency, and the phase corresponding to the low frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency based on the value and the low frequency, and the correlation value and the high frequency corresponding to the high frequency, and the positioning device includes the corrected peak frequency And a radio wave receiving step of receiving the radio wave, using a control program for a positioning device.

  According to the seventh aspect of the present invention, the positioning device generates a positioning device for positioning a current position using a positioning basic code placed on radio waves from a plurality of transmission sources. A peak frequency specifying step for specifying a peak frequency which is a reception frequency corresponding to a maximum correlation value between a replica positioning basic code and the positioning basic code; and a low frequency at which the positioning device is a frequency lower than the peak frequency. A reference frequency calculating step for calculating a high frequency that is higher than the peak frequency, and the positioning device calculates the correlation value corresponding to the low frequency and the correlation value corresponding to the high frequency. A reference correlation value calculating step; and the positioning device includes the correlation value and the peak frequency corresponding to the peak frequency, and the phase corresponding to the low frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency based on the value and the low frequency, and the correlation value and the high frequency corresponding to the high frequency, and the positioning device includes the corrected peak frequency And a radio wave receiving step of receiving the radio wave, using a computer-readable recording medium recording a control program for a positioning device.

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 can receive radio waves S1, S2, S3 and S4 from a plurality of positioning satellites, for example, GPS satellites 12a, 12b, 12c and 12d. The radio wave S1 and the like are examples of radio waves. The GPS satellite 12a or the like is an example of a transmission source.
Various codes (codes) are carried on the radio wave S1 and the like. One of them is a C / A code. This C / A code is composed of 1,023 chips. The C / A code is a signal having a bit rate of 1.023 Mbps and a bit length of 1,023 bits (= 1 msec). This C / A code is an example of a positioning basic code. The terminal 20 is an example of a positioning device that measures the current position.
The terminal 20 is mounted on the automobile 15 and measures the current position while moving as the automobile 15 moves.

For example, the terminal 20 can receive C / A codes from three or more different GPS satellites 12a and the like, and can determine the current position.
First, the terminal 20 specifies to which GPS satellite the received C / A code corresponds. Next, the terminal 20 calculates the phase of the received C / A code (hereinafter referred to as “code phase”) by correlation processing. Subsequently, the terminal 20 uses the code phase to calculate the distance between each GPS satellite 12a and the like and the terminal 20 (hereinafter referred to as a pseudo distance). Subsequently, the current position is calculated based on the position of each GPS satellite 12a or the like on the satellite orbit at the current time and the pseudo distance described above.
Since the C / A code is carried on the radio wave S1 or the like, if the reception frequency when the terminal 20 receives the radio wave S1 or the like is inaccurate, the accuracy of the code phase calculated by the correlation process also deteriorates. Since the GPS satellite 12a and the like are moving in the satellite orbit, this reception frequency continues to change. However, when the signal intensity of the radio wave S1 or the like is strong, frequency synchronization is performed by a PLL using the radio wave S1 or the like. We can continue to secure.
However, when the signal intensity of the radio wave S1 or the like is extremely weak, the PLL does not function effectively. Further, when the signal intensity of the radio wave S1 or the like is extremely weak, it is difficult to accurately predict the IF carrier frequency of the radio wave S1 or the like.
In this regard, as described below, the terminal 20 can accurately measure the current position without predicting the IF carrier frequency when the signal intensity of the radio wave S1 or the like is extremely weak. .

The terminal 20 is, for example, a mobile phone, a PHS (Personal Handy-phone System), a PDA (Personal Digital Assistance _), or the like, but is not limited thereto.
Further, the number of GPS satellites 12a and the like is not limited to four, but may be three or five or more.

(Main hardware configuration of terminal 20)
FIG. 2 is a schematic diagram showing a main hardware configuration of the terminal 20.
As shown in FIG. 2, the terminal 20 has a computer, and the computer has 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.
An external storage device 28 is connected to the bus 22. The external storage device 28 is, for example, an HDD (Hard Disc Drive).
In addition, a power supply device 30, an input device 32, a GPS device 34, a display device 47, and a clock 48 are connected to the bus 22.

(About the configuration of the GPS device 34)
FIG. 3 is a schematic diagram showing the configuration of the GPS device 34.
As shown in FIG. 3, the GPS device 34 includes an RF unit 35 and a baseband unit 36.
The RF unit 35 receives the radio wave S1 and the like with the antenna 35a. Then, the LNA 35b that is an amplifier amplifies a signal such as a C / A code carried on the radio wave S1. Then, the mixer 35c down-converts the frequency of the signal to an intermediate (IF) carrier frequency. A quadrature (IQ) detector 35d then IQ separates the signal. Subsequently, the AD converters 35e1 and 35e2 are configured to convert the IQ separated signals into digital signals, respectively.
The baseband unit 36 receives the IF carrier frequency signal converted from the RF unit 35 into a digital signal.
The correlation unit 37 of the baseband unit 36 performs, for example, synchronous integration of the input digital signal in a time of 10 milliseconds (ms), and performs coherent processing that correlates the integration result with the replica C / A code. . The correlation unit 37 includes an NCO 38, a code generator 39, and a correlator 40. The code generator 39 generates a replica C / A code at the timing of the clock generated by the NCO 38. The correlator 40 correlates the C / A code and the replica C / A code, specifies the phase, and calculates the correlation value. The correlation unit 37 can set the frequency and the phase of the replica C / A code.
The signal integrator 41 performs incoherence, which is a process of integrating the correlation values output from the correlation unit 37.
The code phase detector 42 detects the code phase from the output value of the correlation unit 37 and the output value from the signal integrator 41.

As described above, the correlation processing includes coherent and incoherent.
Coherent is a process in which the correlation unit 37 correlates the received C / A code and the replica C / A code.
For example, if the coherent time is 20 msec, a correlation value between the C / A code and the replica C / A code synchronously integrated in the time of 20 msec is calculated. As a result of the coherent processing, a correlated phase and a correlation value are output.
Incoherent is a process of calculating an incoherent value by accumulating correlation values of coherent results.
As a result of the correlation processing, the phase output by the coherent processing and the incoherent value are output. The correlation value P is an incoherent value.
When the signal intensity of the radio wave S1 or the like is sufficiently strong, the phase detector 43 can acquire the phase information from the correlator 40 and supply it to the NCO 38 to configure the PLL. As a result, a replica C / A code can be generated at a frequency synchronized with the IF carrier frequency. Specifically, the reception frequency is controlled so that the correlation value P is maximized.
The phase detector 43, the correlator 40, and the NCO 38 are examples of reception frequency control means.

(About main software configuration of terminal 20)
FIG. 4 is a schematic diagram showing a main software configuration of the terminal 20.
As shown in FIG. 4, the terminal 20 includes a control unit 100 that controls each unit, a GPS unit 102 that corresponds to the GPS device 34 in FIG. 2, a clock unit 104 that corresponds to the clock 48, and a first storage unit that stores various programs. 110, and a second storage unit 150 that stores various types of information.

As illustrated in FIG. 4, the terminal 20 stores satellite orbit information 152 in the second storage unit 150. The satellite orbit information 152 includes an almanac 152a and an ephemeris 152b. The almanac 152a is information indicating an approximate orbit of all the GPS satellites 12a and the like. The ephemeris 152b is information indicating a precise orbit of each GPS satellite 12a and the like.
The terminal 20 uses the almanac 152a and the ephemeris 152b for positioning.

  As illustrated in FIG. 4, the terminal 20 stores initial position information 154 in the second storage unit 150. The initial position information 154 is information indicating the current initial position P0 of the terminal 20. The initial position Q0 is, for example, a positioning position at the previous positioning.

As illustrated in FIG. 4, the terminal 20 stores an observable satellite calculation program 112 in the first storage unit 110. The observable satellite calculation program 112 refers to the almanac 152a and generates observable satellite information 156 indicating the GPS satellites 12a and the like that can be observed from the initial position Q0 at the current time measured by the timer unit 104. It is a program for.
The control unit 100 stores the generated observable satellite information 156 in the second storage unit 150.

  As illustrated in FIG. 4, the terminal 20 stores a first estimated frequency calculation program 114 in the first storage unit 110. The first estimated frequency calculation program 114 is a program for the control unit 100 to calculate a first estimated frequency A that is a predicted value of the IF carrier frequency for each radio wave S1 and the like. The first estimated frequency A is a predicted value of the IF carrier frequency of the radio wave S1 when the terminal 20 receives the radio wave S1 from the GPS satellite 12a at the current time, for example.

FIG. 5 is an explanatory diagram of the first estimated frequency calculation program 114.
As shown in FIG. 5, the first estimated frequency A is a frequency obtained by adding the Doppler shift H2 from the transmission frequency H1. The transmission frequency H1 is a known value determined by, for example, 1.5 GHz, which is a frequency when the radio wave S1 or the like is transmitted from the GPS satellite 12a or the like, and a down conversion rate by the mixer 35c. The Doppler shift H2 is a frequency shift caused by the relative movement of the GPS satellite 12a and the terminal 20 and the terminal 20, and is constantly changing. The Doppler shift H2 can be calculated from the initial position P0 of the terminal 20 and the ephemeris 152b.
The control unit 100 stores first estimated frequency information 158 indicating the first estimated frequency A in the second storage unit 150.

However, since the position of the terminal 20 is not the accurate current position but the initial position Q0, and the GPS satellite 12a and the terminal 20 always move relative to each other, the calculated Doppler shift H1 is a true Doppler shift. There is a possibility of deviation from the shift.
For this reason, the first estimated frequency A usually deviates from the true IF carrier frequency.

As illustrated in FIG. 4, the terminal 20 stores a first correlation program 116 in the first storage unit 110. The first correlation program 116 calculates a correlation value between the C / A code and the replica C / A code received by the control unit 100 from the GPS satellite 12a and the like, and further uses the phase of the C / A code (code phase). This is a program for calculating a certain first phase CP1.
The first phase CP1 is the phase of the C / A code and also the phase of the replica C / A code.

FIG. 6 is an explanatory diagram of the first correlation program 116.
As shown in FIG. 6A, the control unit 100 performs correlation processing by dividing one chip of the C / A code at, for example, equal intervals by the baseband unit. 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. The phase of the first phase width W1 interval when the control unit 100 performs the correlation process is referred to as a first 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 of the signal input to the antenna 35a 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. 6B, the control unit 100 performs correlation processing while changing the range of the estimated frequency A ± 100 kHz in units of 100 Hz. For each frequency, the code phase CP is varied with the first phase width W1, and the frequency and code phase for which the correlation maximum value Pmax can be calculated are specified.
At the start of positioning, the replica C / A code is varied from 0 to 1023 chips.
Then, once the code phase and frequency corresponding to the correlation maximum value Pmax are specified, the signal S1 and the like are thereafter narrowed in a range narrower than that at the start of positioning around the code phase and frequency corresponding to the correlation maximum value Pmax. Perform a search. For example, the control unit 100 searches for a phase range of ± 256 chips around the already calculated first positioning phase CP1. As for the frequency, a range of ± 1.0 kHz is searched in units of 100 Hz centering on the frequency corresponding to the maximum correlation value Pmax. This condition is called a first tracking condition.

As shown in FIG. 6C, the baseband unit 36 outputs a correlation value P corresponding to the phases C1 to C64 for two chips. Each of the phases C1 to C64 is the first sampling phase SC1.
The ratio of Pmax to Pnoise is called SNR. Pnoise is the signal level of environmental noise. Pmax is a signal level from the GPS satellite 12a or the like.
In a state where the signal intensity such as the signal S1 is weak, the SNR1 in FIG. 6C is relatively small.

The control unit 100 specifies the first phase CP1 corresponding to the correlation value Pmax.
The control unit 100 stores the first phase information 160 indicating the first phase CP1 in the second storage part 150.
The smaller the SNR1, the lower the accuracy of the first phase CP1.
Note that the operation of the terminal 20 based on the first correlation program 116 described above is referred to as a first correlation process.

  As illustrated in FIG. 4, the terminal 20 stores a first positioning program 118 in the first storage unit 110. The first positioning program 118 is a program for the control unit 100 to measure the current position and calculate the positioning position Q1 based on the first phase CP1 corresponding to three or more GPS satellites 12a and the like.

FIG. 7 is a conceptual diagram showing a positioning method.
As shown in FIG. 7, for example, it can be considered that a plurality of 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, there is a code fraction C / Aa. That is, between the GPS satellite 12a and the terminal 20, a portion that is an integral multiple of the C / A code (a portion where n C / A codes are arranged (n is an integer)) and a fraction portion (the code fraction C / Aa) exists. The total length of the integer multiple of the C / A code and the code fraction C / Aa is the pseudo distance. The terminal 20 performs positioning using this pseudo distance.
The position of the GPS satellite 12a in the orbit can be calculated using the ephemeris 152b. Then, by calculating the distance between the position of the GPS satellite 12a in the orbit and the initial position Q0, it is possible to specify a portion that is an integral multiple of the C / A code.
Then, as shown in FIG. 7, the correlation process is performed while moving the phase of the replica C / A code in the direction of the arrow X1, for example.
The phase with the maximum correlation value is the code fraction C / Aa. The code fraction C / Aa is the first phase CP1.

The control unit 100 calculates a pseudo distance between each GPS satellite 12a and the terminal 20 based on the first phase CP1 corresponding to three or more GPS satellites 12a and the like. Then, the position of each GPS satellite 12a or the like in the orbit is calculated by the epheris 152b. Then, based on the positions of the three or more GPS satellites 12a or the like in the orbit and the pseudo distance, the current position is measured and the positioning position Q1 is calculated.
The control unit 100 stores first positioning position information 162 indicating the positioning position Q1 in the second storage unit 150.

  As illustrated in FIG. 4, the terminal 20 stores a positioning position output program 120 in the first storage unit 110. The positioning position output program 120 is a program for the control unit 100 to display the positioning position Q1 or a positioning position Q2 described later on the display device 47.

As illustrated in FIG. 4, the terminal 20 stores a second correlation program 122 in the first storage unit 110. The second correlation program 122 is a program for the control unit 100 to perform correlation processing and calculate the correlation value P and the code phase CP.
The control unit 100 stores the correlation value P and the second correlation information 164 indicating the code phase CP in the second storage unit 150.

  As illustrated in FIG. 4, the terminal 20 stores a peak frequency specifying program 124 in the first storage unit 110. The peak frequency specifying program 124 and the control unit 100 are examples of peak frequency specifying means.

FIG. 8 is an explanatory diagram of the peak frequency specifying program 124.
As shown in FIG. 8, the control unit 100 specifies the frequency corresponding to the maximum correlation value Pmax as the peak frequency F0. The peak frequency F0 is an example of the peak frequency.
The peak frequency F0 is a result of the terminal 20 searching for a width of, for example, 100 Hz, and therefore, a maximum deviation of about 50 Hz from the true IF carrier frequency such as the received radio wave S1 occurs.
The control unit 100 stores peak frequency information 166 indicating the peak frequency F0 in the second storage unit 150.

As illustrated in FIG. 4, the terminal 20 stores a reference frequency calculation program 126 in the first storage unit 110. The reference frequency calculation program 126 and the control unit 100 are an example of a reference frequency calculation unit.
Based on the reference frequency calculation program 126, the control unit 100 calculates a frequency F1 that is 100 Hz lower than the peak frequency F0 and a frequency F2 that is 100 Hz higher than the peak frequency F0. The control unit 100 stores reference frequency information 168 indicating the frequency F1 and the frequency F2 in the second storage unit 150. The frequency F1 is an example of a low frequency. The frequency F2 is an example of a high frequency.
The frequency F1 and the frequency F1 are defined so that the frequency difference between the peak frequency F0 and the frequency F1 is equal to the frequency difference between the peak frequency F0 and the frequency F2. In the present embodiment, the frequency difference is set to 100 Hz.
Unlike this embodiment, the frequency difference is not limited to 100 Hz.

As illustrated in FIG. 4, the terminal 20 stores a reference correlation value calculation program 128 in the first storage unit 110. The reference correlation value calculation program 128 and the control unit 100 are an example of a reference correlation value calculation unit.
Based on the reference correlation value calculation program 128, the control unit 100 calculates a correlation value P1 corresponding to the frequency F1 and a correlation value P2 corresponding to the frequency F2. Specifically, the control unit 100 refers to the second correlation information 164 and calculates the correlation value P1 and the correlation value P2.
The control unit 100 stores reference correlation value information 170 indicating the correlation value P1 and the correlation value P2 in the second storage unit 150.

  As illustrated in FIG. 4, the terminal 20 stores a second estimated frequency calculation program 130 in the first storage unit 110. In the second estimated frequency calculation program 130, the control unit 100 uses the second estimated frequency based on the peak frequency F0 and the correlation peak value Pmax (P0), the frequency F1 and the correlation value P1, and the frequency F2 and the correlation value P2. This is a program for calculating Fr. The second estimated frequency Fr is an example of a corrected peak frequency. The second estimated frequency calculation program 130 and the control unit 100 are an example of a corrected peak frequency calculation unit.

9 and 10 are explanatory diagrams of the second estimated frequency calculation program 130. FIG.
The graph indicating the correlation value P and the frequency F draws an isosceles triangle as shown in FIGS.
As shown in FIGS. 9A and 10A, the point G0 is defined by the peak frequency F0 and the correlation peak value P0. The point G1 is defined by the frequency F1 and the correlation value P1. A point G2 is defined by the frequency F2 and the correlation value P2.

As shown in FIGS. 9A and 9B, when the correlation value P1 is smaller than the correlation value P2, the points G0 and G1 are on the same straight line with the slope a (a is a positive number). is there. A straight line connecting the points G0 and G1 is a straight line L1.
The point G2 is on a straight line having an inclination of -a. A straight line having an inclination of −a and passing through the point G2 is a straight line L2.
And the intersection of the straight line L1 and the straight line L2 is the vertex H of an isosceles triangle. The frequency corresponding to the vertex H is the second estimated frequency Fr. By solving the simultaneous equations 1 in FIG. 9B, the unknowns Fr, Pr and the slope a can be calculated.

As shown in FIGS. 10A and 10B, when the correlation value P1 is larger than the correlation value P2, the point G0 and the point G2 are on the same straight line with a slope −a (a is a positive number). It is in. A straight line connecting the points G0 and G2 is a straight line L2.
The point G1 is on a straight line having an inclination a. A straight line having an inclination a and passing through the point G1 is a straight line L1.
And the intersection of the straight line L1 and the straight line L2 is the vertex H of an isosceles triangle. The frequency corresponding to the vertex H is the second estimated frequency Fr. When the simultaneous equations 2 in FIG. 10B are solved, the unknowns Fr, Pr and the slope a can be calculated.

When the correlation value P1 is equal to the correlation value P2, the peak frequency F0 is the second estimated frequency Fr.
The control unit 100 stores second estimated frequency information 172 indicating the second estimated frequency Fr in the second storage unit 150.
The second estimated frequency Fr is highly accurate information because it is not limited to 100 Hz, which is the frequency F search step. That is, it is closer to the true IF carrier frequency than the peak frequency F0.

  As illustrated in FIG. 4, the terminal 20 stores a second phase determination program 132 in the first storage unit 110. The second phase determination program 132 is used when the control unit 100 receives the radio wave S1 and the like using the second estimated frequency Fr, performs correlation processing, and calculates a second phase CP2 for performing positioning. It is a program. The second phase determination program 132 and the control unit 100 are examples of radio wave receiving means.

FIG. 11 is an explanatory diagram of the second phase determination program 132.
SNR2 in the correlation graph of FIG. 11 is larger than SNR1 in the graph of FIG. This is because the second estimated frequency Fr is very close to the true IF carrier frequency.
Therefore, the second phase CP2, which is the phase corresponding to the maximum correlation value Pmax, is highly accurate phase information.
The control unit 100 stores second phase information 174 indicating the second phase CP2 in the second storage unit 150.
The operation of the terminal 20 based on the second correlation program 122, the peak frequency identification program 124, the reference frequency calculation program 126, the reference correlation value calculation program 128, the second estimated frequency calculation program 130, and the second phase determination program 132 described above is described. This is called two-correlation processing.

As illustrated in FIG. 4, the terminal 20 stores a second positioning program 134 in the first storage unit 110. The second positioning program 134 is a program for the control unit 100 to perform positioning using the second phase CP2 for three or more GPS satellites 12a and calculate the positioning position Q2.
The control unit 100 stores second positioning position information 176 indicating the positioning position Q2 in the second storage unit 150.

As illustrated in FIG. 4, the terminal 20 stores a signal strength evaluation program 136 in the first storage unit 110.
The signal strength evaluation program 136 is a program for evaluating the signal strength SP of the signal input to the antenna 35a. The signal strength SP of the signal input to the antenna 35a can be estimated from the correlation value.
For example, when the signal intensity SP is −138 dBm or more, the control unit 100 performs the first correlation process and calculates the positioning position Q1.
Then, when the signal strength SP is −142 dBm or less, the control unit 100 performs the second correlation process and calculates the positioning position Q2.
When the signal strength SP is greater than −142 dBm and less than −138 dBm, the control unit 100 performs the first correlation process and the second correlation process in parallel. Then, the control unit 100 calculates the positioning position Q1 using the first phase CP1.

The terminal 20 is configured as described above.
As described above, the terminal 20 can specify the peak frequency F0 (see FIG. 4).
Further, the terminal 20 can calculate the second estimated frequency Fr (see FIG. 4).
When the phase of the replica C / A code is fixed, the graph showing the relationship between the correlation value and the reception frequency (IF carrier frequency) has a point corresponding to the maximum value of the correlation value as shown in FIG. Draw an isosceles triangle. The point G0 corresponding to the peak frequency F0 is located near the apex H, and the points G1 and G2 corresponding to the frequencies F1 and F2 before and after the peak frequency F0 are located on different hypotenuses. Since either one of the point G1 and the point G2 is located on the same oblique side as the point G1, the slope a of the oblique side can be specified. In an isosceles triangle, if the slope of one hypotenuse can be specified, the slope of the other hypotenuse can also be specified. The point where the two hypotenuses intersect is the vertex H. The frequency corresponding to the vertex H is the above-described second estimated frequency Fr.
As described above, there is always one peak frequency F0 even when the expected IF carrier frequency cannot be determined when the signal intensity of the radio wave S1 or the like is extremely weak. If the peak frequency F0 is specified, the second estimated frequency Fr can be calculated.
Then, the terminal 20 can receive the radio wave S1 and the like using the second estimated frequency Fr. For this reason, the correlation value P can be calculated with high accuracy, and the current position can be calculated with high accuracy.
As a result, when the signal strength of the satellite radio wave is extremely weak, positioning can be performed with high accuracy without requiring the expected IF carrier frequency to be determined.

Also, the terminal 20 can control the reception frequency by using the PLL so that the coherent value between the replica C / A code and the received C / A code is maximized.
As a result, when the signal intensity of the radio wave S1 or the like is within a predetermined intensity range, the PLL can function effectively, and the reception frequency can be continuously brought close to the IF carrier frequency of the radio wave S1 or the like.

  In addition, when the signal intensity of the radio wave S1 or the like is within a predetermined range, the terminal 20 can perform the first correlation process and the second correlation process described above in parallel. For this reason, when the signal strength SP shifts from a state larger than a predetermined strength to a small state, positioning can be continuously performed with high accuracy.

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 FIGS. 12 and 13.
12 and 13 are schematic flowcharts showing an operation example of the terminal 20.

First, the terminal 20 calculates an estimated frequency A for each GPS satellite 12a and the like from the ephemeris 152b and the initial position Q0 (step ST1 in FIG. 12).
Subsequently, the terminal 20 performs a first correlation process (step ST2).

Subsequently, the terminal 20 determines the signal strength SP (step ST3).
If the terminal 20 determines in step ST3 that the signal strength SP is -138 dBm or more, the terminal 20 continues the first correlation process (step ST4A), measures the current position using the first phase CP1, and determines the positioning position. Q1 is calculated (step ST5A).
Subsequently, the terminal 20 outputs the positioning position Q1 (step ST6A).
Subsequently, the terminal 20 determines whether or not the positioning has reached the predetermined number of times of positioning, for example, 10 times (step ST7).
If the terminal 20 determines that positioning has reached the specified number of positioning times, the terminal 20 ends positioning.
If the terminal 20 determines that the positioning has not reached the specified number of positioning times, the terminal 20 performs step ST3 and subsequent steps.

If the terminal 20 determines in step ST3 that the signal strength SP is −142 dBm or less, the terminal 20 stops the first correlation process and performs the second correlation process (step ST4B).
In the second correlation process, the terminal 20 first specifies the peak frequency F0 (see FIG. 4) (step ST101 in FIG. 13). This step ST101 is an example of a peak frequency specifying step.
Subsequently, terminal 20 calculates frequencies F1 and F2 (see FIG. 4) (step ST102). This step ST102 is an example of a reference frequency calculation step.

Subsequently, the terminal 20 calculates correlation values P2 and P3 (see FIG. 4) (step ST103). This step ST103 is an example of a reference correlation value calculation step.
Subsequently, the terminal 20 calculates a second estimated frequency Fr (see FIG. 4) (step ST104). This step ST104 is an example of a corrected peak frequency calculating step.

Subsequently, the terminal 20 calculates the second phase CP2, measures the current position using the second phase CP2, and calculates the positioning position Q2 (step ST5B in FIG. 12).
Subsequently, the terminal 20 outputs the positioning position Q2 (step ST6B) and performs step ST7.

When determining that the signal strength SP is greater than −142 dBm and less than −138 dBm in step ST3, the terminal 20 performs the first correlation process and the second correlation process in parallel (step ST4C in FIG. 12).
Subsequently, the terminal 20 measures the current position using the first phase CP1, and calculates the positioning position Q1 (step ST5C).
Subsequently, the terminal 20 outputs the positioning position Q1 (step ST6C) and performs step ST7.
If the terminal 20 determines that the positioning has not reached the specified number of positioning times, the terminal 20 performs step ST3 and subsequent steps. In step ST3 again, when the terminal 20 determines that the signal strength SP is −138 dBm or less, the terminal 20 proceeds to step ST4B. Here, since the first correlation process and the second correlation process continue in parallel, the first correlation process can be stopped and the second correlation process can be performed immediately. This is because the second correlation process is not started after the PLL does not function in the first correlation process, but the signal intensity SP may be lowered to −142 dBm or less (the signal intensity SP is lower than the first correlation process). This means that the second correlation process is continued in a state greater than −142 dBm and less than −138 dBm). For this reason, since it is not necessary to newly search a wide range of frequencies and phases in the second correlation processing, step ST5B and the subsequent steps can be performed quickly.
In addition, the intermediate state (the state where the signal intensity SP is greater than −142 dBm and less than −138 dBm) is a state in which the signal intensity SP may be −138 dBm or more. By continuing the first correlation process in advance, when the signal intensity becomes −138 dBm or more, it is possible to immediately shift to a state in which only the first correlation process is performed.

  The present invention is not limited to the embodiments described above. Furthermore, the above-described embodiments may be combined with each other.

It is the schematic which shows the terminal etc. of embodiment of this invention. It is the schematic which shows the main hardware constitutions of a terminal. It is the schematic which shows the structure of a GPS apparatus. It is the schematic which shows the main software structures of a terminal. It is explanatory drawing of a 1st estimated frequency calculation program. It is explanatory drawing of a 1st correlation program. It is a conceptual diagram which shows the positioning method. It is explanatory drawing of a peak frequency specific program. It is explanatory drawing of the 2nd estimated frequency calculation program. It is explanatory drawing of the 2nd estimated frequency calculation program. It is explanatory drawing of a 2nd phase determination program. It is a schematic flowchart which shows the operation example of a terminal. It is a schematic flowchart which shows the operation example of a terminal.

Explanation of symbols

  12a, 12b, 12c, 12d ... GPS satellites, 20 ... terminal, 34 ... GPS device, 112 ... observable satellite calculation program, 114 ... first estimated frequency calculation program, 116 ... First correlation program 118 ... first positioning program 120 ... positioning position output program 122 ... second correlation program 124 ... peak frequency specifying program 126 ... reference frequency calculation program 128 ... Reference correlation value calculation program, 130 ... Second estimated frequency calculation program, 132 ... Second phase identification program, 134 ... Second positioning program, 136 ... Signal strength evaluation program

Claims (9)

A positioning device that measures a current position using a positioning basic code placed on radio waves from a plurality of transmission sources,
A peak frequency specifying means for specifying a peak frequency that is a reception frequency corresponding to a maximum value of a correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code;
A reference frequency calculating means for calculating a first frequency which is a predetermined number lower than the peak frequency and a second frequency which is a frequency higher than the peak frequency by the predetermined number ;
A reference correlation value calculating means for calculating a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
Based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, the second correlation value and the second frequency, a corrected peak frequency Corrected peak frequency calculating means for calculating
Radio wave receiving means for receiving the radio wave using the corrected peak frequency;
Have
The corrected peak frequency calculating means is
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
When the first correlation value is smaller than the second correlation value, the frequency corresponding to the intersection of the straight line passing through G1 and G0 and having a slope a and the straight line passing through G2 and the slope −a Is a peak frequency after correction. A positioning device that measures a current position using a positioning basic code placed on radio waves from a plurality of transmission sources,
A peak frequency specifying means for specifying a peak frequency that is a reception frequency corresponding to a maximum value of a correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code;
A reference frequency calculating means for calculating a first frequency which is a predetermined number lower than the peak frequency and a second frequency which is a frequency higher than the peak frequency by the predetermined number ;
A reference correlation value calculating means for calculating a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
Based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, the second correlation value and the second frequency, a corrected peak frequency Corrected peak frequency calculating means for calculating
Radio wave receiving means for receiving the radio wave using the corrected peak frequency;
Have
The corrected peak frequency calculating means is
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
When the first correlation value is larger than the second correlation value, the frequency corresponding to the intersection of the straight line passing through G2 and G0 and having the slope −a and passing through G1 and having the slope a. Is a peak frequency after correction.   The positioning apparatus according to claim 1, further comprising: a reception frequency control unit that controls a reception frequency so that a coherent value between the replica positioning basic code and the positioning basic code is maximized.   4. The positioning apparatus according to claim 3, wherein the corrected peak frequency calculation means and the reception frequency control means operate in parallel.   The positioning device according to any one of claims 1 to 4, wherein the transmission source is a positioning satellite. A positioning device that measures the current position using positioning basic codes placed on radio waves from a plurality of transmission sources has a maximum correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code. A peak frequency specifying step for specifying a peak frequency that is a reception frequency corresponding to the value;
A reference frequency calculating step in which the positioning device calculates a first frequency that is a predetermined number of frequencies lower than the peak frequency and a second frequency that is higher than the peak frequency by the predetermined number ;
A reference correlation value calculating step in which the positioning device calculates a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
The positioning device is based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, and the second correlation value and the second frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency;
A radio wave receiving step in which the positioning device receives the radio wave using the corrected peak frequency;
Have
The corrected peak frequency calculating step includes:
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
If the first correlation value is smaller than the second correlation value, the frequency corresponding to the intersection of the straight line passing through G1 and G0 and having a slope a and the straight line passing through G2 and the slope -a Is a corrected peak frequency, and a positioning apparatus control method. A positioning device that measures the current position using positioning basic codes placed on radio waves from a plurality of transmission sources has a maximum correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code. A peak frequency specifying step for specifying a peak frequency that is a reception frequency corresponding to the value;
A reference frequency calculating step in which the positioning device calculates a first frequency that is a predetermined number of frequencies lower than the peak frequency and a second frequency that is higher than the peak frequency by the predetermined number ;
A reference correlation value calculating step in which the positioning device calculates a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
The positioning device is based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, and the second correlation value and the second frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency;
A radio wave receiving step in which the positioning device receives the radio wave using the corrected peak frequency;
Have
The corrected peak frequency calculating step includes:
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
When the first correlation value is larger than the second correlation value, the frequency corresponding to the intersection of the straight line passing through G2 and G0 and having the slope −a and passing through G1 and having the slope a. Is a corrected peak frequency, and a positioning apparatus control method. On the computer,
A positioning device that measures the current position using positioning basic codes placed on radio waves from a plurality of transmission sources has a maximum correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code. A peak frequency specifying step for specifying a peak frequency that is a reception frequency corresponding to the value;
A reference frequency calculating step in which the positioning device calculates a first frequency that is a predetermined number of frequencies lower than the peak frequency and a second frequency that is higher than the peak frequency by the predetermined number ;
A reference correlation value calculating step in which the positioning device calculates a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
The positioning device is based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, and the second correlation value and the second frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency;
The positioning device is a radio wave receiving step of receiving the radio wave using the corrected peak frequency, and a positioning device control program for executing the program,
The corrected peak frequency calculating step includes:
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
If the first correlation value is smaller than the second correlation value, the frequency corresponding to the intersection of the straight line passing through G1 and G0 and having a slope a and the straight line passing through G2 and the slope -a Is a peak frequency after correction, a control program for a positioning device. On the computer,
A positioning device that measures the current position using positioning basic codes placed on radio waves from a plurality of transmission sources has a maximum correlation value between the replica positioning basic code generated by the positioning device and the positioning basic code. A peak frequency specifying step for specifying a peak frequency that is a reception frequency corresponding to the value;
A reference frequency calculating step in which the positioning device calculates a first frequency that is a predetermined number of frequencies lower than the peak frequency and a second frequency that is higher than the peak frequency by the predetermined number ;
A reference correlation value calculating step in which the positioning device calculates a first correlation value corresponding to the first frequency and a second correlation value corresponding to the second frequency;
The positioning device is based on the correlation value and the peak frequency corresponding to the peak frequency, the first correlation value and the first frequency, and the second correlation value and the second frequency. A corrected peak frequency calculating step for calculating a corrected peak frequency;
The positioning device is a radio wave receiving step of receiving the radio wave using the corrected peak frequency, and a positioning device control program for executing the program,
The corrected peak frequency calculating step includes:
In the graph showing the frequency on the first axis and the correlation value on the second axis orthogonal to the first axis,
A point indicating the correlation value and the peak frequency corresponding to the peak frequency is G0,
G1 is a point indicating the first correlation value and the first frequency,
G2 is a point indicating the second correlation value and the second frequency,
If
When the first correlation value is greater than the second correlation value, the frequency corresponding to the intersection of the straight line having the slope −a passing through G2 and G0 and the straight line having the slope a through G2. Is a peak frequency after correction, a control program for a positioning device.

Images