JP5446062B2 - Search range update method, terminal device control program, recording medium, and terminal device - Google Patents

Description

The present invention relates to a satellite signal search range update method, a terminal device control program, a recording medium, and a terminal device in a terminal device capable of performing positioning using an SPS (Satellite Positioning System).

Conventionally, SPS, for example, GPS (Global Positioning Sys)
tem) has been put to practical use (for example, Patent Document 1).
The GPS receiver receives, for example, signals from four GPS satellites located in the sky (hereinafter referred to as satellite signals), and each satellite signal is transmitted from each GPS satellite (hereinafter also simply referred to as “satellite”). The distance between each GPS satellite and the GPS receiver (hereinafter referred to as “pseudo-range”) is obtained by the difference between the measured time and the time when the GPS receiver is reached (hereinafter referred to as “delay time”). .
The GPS receiver uses the position of each GPS satellite in the satellite orbit and the above pseudorange to
The positioning result of the current position of the S receiver is calculated. The satellite signal is C / A (Co
ares / Acquisition) code, navigation message, and other information.

The GPS receiver can also calculate the above-mentioned pseudo distance by using the code phase of the C / A code carried on the satellite signal. This C / A code is 1.023Mb
This is a signal having a bit rate of ps and a bit length of 1,023 bits (= 1 msec = 300 km). If the initial position of the GPS receiver is known within an error range of 150 km,
Since it is possible to estimate how many C / A codes exist with the PS receiver, C / A
The pseudo distance can be calculated using the fractional part of the code (code phase).
In order to receive the satellite signal, the GPS receiver calculates the search center frequency in consideration of the carrier frequency of the satellite signal and the Doppler shift due to the relative movement between each satellite and the GPS receiver. Then, a search band (hereinafter referred to as “search range”) having a certain width around the search center frequency is determined.
The GPS receiver uses a clock from an internal reference oscillator (hereinafter referred to as “local oscillator”) to downconvert the frequency of the received satellite signal.
However, drift occurs in the local oscillator. Drift is a change in oscillation frequency due to a temperature change.
If the reception frequency after down-conversion falls outside the search range due to drift of the local oscillator, the search may become inefficient or cannot be performed.

On the other hand, a technique has been proposed in which a highly accurate reference frequency is acquired from a communication base station or the like and the reference frequency is used for determining a search range (for example, Patent Document 2, Patent Document 3, and Patent Document). 4).
However, the reference frequency acquired from a communication base station or the like is usually lower than the accuracy of the carrier frequency of the satellite signal, even if the accuracy is high. For this reason, the drift calculated using the reference frequency has a problem that the error range must be set wide, and the search range is widened by the error range.
Note that drift and drift error (drift error) are different concepts. That is,
Drift is a deviation of the oscillation frequency due to temperature change and is a kind of error, but the calculated drift itself also has an error.

In addition, a technique for determining a search range according to the magnitude of the offset (drift) of the oscillator at the previous positioning has been proposed (for example, Patent Document 5). Since the drift during positioning is calculated as a result of synchronizing with the carrier frequency of the satellite signal with extremely high accuracy, the accuracy is high and the error is small.
However, if the search range is determined using the drift calculated at the time of positioning, the reception frequency may be out of the search range between one positioning and the next positioning. In particular, in the temperature region where the fluctuation of drift is large, there is a greater possibility that the reception frequency is out of the search range between positioning.

JP 2000-131415 A (FIG. 1 etc.) Special Table 2000-506348 JP 2002-228737 A Japanese National Patent Publication No. 11-513787 JP-A-5-256926

Therefore, the present invention restricts the search range from being widened by using the drift calculated using the reference frequency, and the received frequency is searched by drift fluctuation during the calculation of the drift by receiving the satellite signal. It is an object of the present invention to provide a search range update method, a terminal device control program, a recording medium, and a terminal device, which can shorten the duration of a state out of range.

According to the first aspect of the present invention, there is provided a method for updating a search range of a satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of SPS satellites, and uses a reference frequency to locally A first drift calculating step for continuously calculating the first drift of the oscillator, a search range calculating step for calculating a search range of the satellite signal using the first drift, and a reception frequency of the satellite signal are used. A second drift calculating step of calculating a second drift of the local oscillator, a basic updating step of updating the search range using the second drift, and an error of the first drift being an error of the second drift An intermediate update that updates the search range using the first drift during the second drift calculation even if it is greater than the error Is achieved by the method of updating the search range characterized by having a step, the.

According to the configuration of the first invention, the search range can be updated using the first drift during the second drift calculation. That is, during the second drift calculation, it is possible to shorten the duration of the state where the reception frequency is out of the search range due to drift fluctuation during positioning.
Further, the intermediate update step is performed only during the second drift calculation.
This means that the basic update step is performed when the second drift is calculated. Here, the error of the second drift is usually smaller than the error of the first drift.
For this reason, it can restrict | limit that a search range becomes wide by utilizing the drift calculated using the reference frequency.
This limits the search range from being widened by using the drift calculated using the reference frequency, while the received frequency deviates from the search range due to drift fluctuations during satellite signal reception and drift calculation. The duration of the state can be shortened.

According to a second aspect of the invention, in the configuration of the first aspect of the invention, the intermediate update step is performed when a fluctuation amount of the first drift is larger than an error of the second drift. This is a range update method.

In the second update step, the search range is updated using the second drift. The center frequency of the search range is defined based on the second drift, and the bandwidth of the search range is defined based on the error of the second drift.
Even if the error of the first drift is usually larger than the error of the second drift, the fluctuation amount of the first drift has a certain reliability. The fact that the fluctuation amount of the first drift is larger than the error of the second drift means that the reception frequency may be out of the search range due to the drift fluctuation.
In this regard, according to the configuration of the second invention, the intermediate update step is performed when the fluctuation amount of the first drift is larger than the error of the second drift. It is possible to shorten the duration of the disengaged state.

A third aspect of the invention is the search range updating method according to the second aspect of the invention, wherein the fluctuation amount of the first drift is calculated by a fluctuation rate of the first drift and an elapsed time.

According to a fourth aspect of the present invention, in the configuration of the first aspect, the intermediate update step is based on a timing at which the reception frequency of the satellite signal deviates from the search range updated in the basic update step due to drift of the local oscillator. The search range updating method is characterized in that the search range is updated.

According to the configuration of the fourth aspect of the invention, the number of times the intermediate update step is performed can be reduced, and for example, battery consumption of the portable terminal device can be saved.

According to a fifth invention, in the configuration of the fourth invention, the timing is calculated from a calculation time of the second drift, an error of the second drift, and a variation rate of the first drift. This is a search range update method.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the intermediate update step is performed when a variation rate of the first drift is not within a predetermined allowable range. This is a search range update method characterized by the above.

According to the configuration of the sixth aspect of the invention, the forced update step is not performed as long as the fluctuation rate of the first drift is within a predetermined allowable range, so that the battery consumption of the terminal device can be saved. it can.

According to a seventh aspect of the invention, in the configuration of the sixth aspect of the invention, the allowable range is defined based on an approximate calculation interval of the second drift and an error of the second drift. It is an update method.

According to the configuration of the seventh invention, the allowable range is an approximate calculation interval of the second drift, and
Since the second drift error is defined based on the error of the second drift, as long as the fluctuation rate of the first drift is within a predetermined allowable range, the reception frequency can be set to the search range without performing the intermediate update step. Never go out of the way.

According to an eighth aspect of the present invention, there is provided a method for updating a search range of a satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of SPS satellites according to an eighth invention, using a reference frequency. A first drift calculating step of continuously calculating the first drift of the local oscillator, a search range calculating step of calculating a search range of the satellite signal using the first drift, and reception of the satellite signal A second drift calculating step of calculating a second drift of the local oscillator using a frequency; a basic updating step of updating the search range using the second drift; and an error of the first drift Even if the error is larger than the error of 2 drifts, the search range is calculated using the first drift during the second drift calculation. An intermediate update step of the new to be achieved by the control program of the terminal device, characterized in that for the execution.

According to the ninth aspect of the present invention, there is provided a method for updating a search range of a satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of SPS satellites according to the ninth invention, using a reference frequency. A first drift calculating step of continuously calculating the first drift of the local oscillator, a search range calculating step of calculating a search range of the satellite signal using the first drift, and reception of the satellite signal A second drift calculating step of calculating a second drift of the local oscillator using a frequency; a basic updating step of updating the search range using the second drift; and an error of the first drift Even if the error is larger than the error of 2 drifts, the search range is calculated using the first drift during the second drift calculation. An intermediate update step of the new to be achieved by the computer-readable recording medium a control program of the terminal device, characterized in that for the execution.

According to the tenth aspect of the present invention, there is provided a terminal device that performs positioning by receiving satellite signals from a plurality of SPS satellites, and continuously calculates a first drift of a local oscillator using a reference frequency. First drift calculating means, search range calculating means for calculating a search range of the satellite signal using the first drift, and second drift of the local oscillator using the reception frequency of the satellite signal. Even if the second drift calculating means for calculating, the basic updating means for updating the search range using the second drift, and the error of the first drift is larger than the error of the second drift, And intermediate update means for updating the search range using the first drift during the second drift calculation.

According to the configuration of the tenth invention, similarly to the configuration of the first invention, the satellite signal is received while restricting the search range from being widened by using the drift calculated using the reference frequency. Thus, the duration of the state where the reception frequency is out of the search range due to drift fluctuation during calculation of the drift can be shortened.

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 signals S1 to S4 from GPS satellites 12a to 12d. The terminal 20 is an example of a terminal device.
GPS satellites are also simply called satellites.
The terminal 20 can receive and communicate with the communication signal CS from the communication base station 40. And it can communicate with another terminal (not shown) via the communication base station 40.
In this specification, it is assumed that the accuracy of the carrier frequency of the communication signal CS is kept constant.

The GPS satellites 12a and the like are examples of SPS satellites, and the signal S1 and the like are examples of satellite signals.
The signal S1 includes a C / A code. The C / A code is a pseudo noise code (hereinafter referred to as PN (Psu
edo random noise code). This C / A
The code 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 is composed of 1,023 chips. The terminal 20 performs positioning of the current position using this C / A code.

The terminal 20 is, for example, a mobile phone, PHS (Personal Handy-phone).
System), PDA (Personal Digital Assistance)
₎ Etc., but is not limited thereto.
The SPS is not limited to GPS, but may be, for example, Galileo or a quasi-zenith satellite.

FIG. 2 is a conceptual diagram illustrating an example of a positioning method.
FIG. 2 shows a positioning method using the code phase.
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. The ephemeris is information indicating a precise orbit of the GPS satellite 12a. 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. The length of the C / A code is 300 kilometers (k
m), the position error of the initial position Q0 needs to be within 150 kilometers (km).

Then, the terminal 20 performs correlation processing while changing the code phase and search frequency of the replica C / A code of the terminal 20. This correlation process includes a coherent process and an incoherent process which will be described later.
The code phase having the maximum correlation integrated value is the code phase of the code fraction part C / Aa.

3 and 4 are explanatory diagrams 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.
For example, as shown in FIG. 3A, if the coherent time is 5 msec, 5 mse.
A correlation value between the C / A code and the replica C / A code integrated synchronously at time c 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.
As shown in FIG. 3B, the code phase C corresponding to the maximum value Pmax of the correlation integrated value P
P1 is the code phase of the code phase fraction part C / Aa (see FIG. 2).

As shown in FIG. 4A, the terminal 20 performs a correlation process by dividing one chip of the C / A code at, for example, equal intervals. One chip of the C / A code is divided into, for example, 32 equal parts. That is, the correlation process is performed at a phase width (phase width W1) interval of 1/32 chips.
As shown in FIG. 4 (b), the terminal 20, for example, from the first chip of the C / A code to the first,
Search up to 023 chips.
At this time, the terminal 20 searches for the signal S1 and the like at a frequency having a predetermined width around the search center frequency A. For example, from a frequency of (A-100) kHz to (A + 100) k
The signal S1 and the like are searched for the frequency range of Hz at a frequency step of 20 Hz.

In general, the GPS receiver calculates the search center frequency A by adding a Doppler shift (predicted Doppler frequency) H2 to the transmission frequency H1 from the GPS satellite 12a or the like and further adding a drift DR. The transmission frequency H1 from the GPS satellite 12a or the like is known, for example, 1
, 575.42 MHz. The drift DR is a change in the oscillation frequency of the reference oscillator of the GPS receiver due to a temperature change.
The Doppler shift is caused by relative movement between each GPS satellite 12a and the like and the GPS receiver. The GPS receiver 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 by the ephemeris. Then, based on the line-of-sight speed, an expected Doppler frequency H2 is calculated.
The GPS receiver calculates a search center frequency A for each GPS satellite 12a and the like.

(Main hardware configuration of terminal 20)
FIG. 5 is a schematic diagram showing the main hardware configuration of the terminal 20.
As shown in FIG. 5, the terminal 20 has a computer, and the computer is connected to the bus 2.
2
The bus 22 includes a CPU (Central Processing Unit) 24.
The storage device 26 is connected. The storage device 26 is, for example, a RAM (Random Ac
access memory) and ROM (read only memory).

The bus 22 includes an input device 28 for receiving various information and commands, a power supply device 30, a communication device 32 for transmitting and receiving communication signals to and from the communication base station 40, a GPS satellite 12a, and the like. A GPS device 34 for receiving the signal S1 and the like and a display device 36 for displaying various information are connected.
The communication device 32 is a VCO (Voltage Controlled Oscillat).
or) 32a. While the communication device 32 is communicating with the base station 40, the frequency of the VCO 32a is corrected using the carrier frequency of the communication signal CS from the base station 40. V
The frequency of CO32a can be corrected, for example, by the method described in Japanese translation of PCT publication No. 2000-506348.
For this reason, the frequency of the VCO 32a has the same accuracy as the carrier frequency of the communication signal CS.
The terminal 20 uses the frequency of the VCO 32a as the reference frequency Hr.
The GPS device 34 includes a local oscillator 34a. The local oscillator 34 a is, for example, a TCXO (Temperature Compe) for generating a reference clock for the GPS device 34.
sated Xtal Oscillator).
A clock 38 is connected to the bus 22.

(About main software configuration of terminal 20)
FIG. 6 is a schematic diagram illustrating a main software configuration of the terminal 20.
As shown in FIG. 6, the terminal 20 includes a control unit 100 that controls each unit, a communication unit 102 that corresponds to the communication device 32 in FIG. 5, a GPS unit 104 that corresponds to the GPS device 34, and a display unit that corresponds to the display device 36. 106, a time measuring unit 108 corresponding 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. 6, the terminal 20 stores satellite orbit information 152 in the second storage unit 150. The satellite orbit information 152 includes an Almanac 152a indicating a general orbit of all GPS satellites 12a and the like, and an ephemeris 152b indicating a precise orbit of each GPS satellite 12a and the like. The terminal 20 acquires the almanac 152a and the ephemeris 152b by receiving and decoding the signal S1 and the like from the GPS satellite 12a and the like.
The terminal 20 uses the satellite orbit information 152 for positioning based on the signal S1 and the like.

As illustrated in FIG. 6, the terminal 20 stores initial position information 154 in the second storage unit 150. The initial position information 154 is information indicating the initial position P0. The initial position P0 is, for example, a positioning position at the previous positioning.

As illustrated in FIG. 6, the terminal 20 stores the observable satellite calculation program 1 in the first storage unit 110.
12 is stored. The observable satellite calculation program 112 is configured so that each control unit 100 can observe each G that can be observed at the current time measured by the time measuring unit 108 with reference to the almanac 152a.
This is a program for calculating the PS satellite 12a and the like.
Specifically, based on the almanac 152a, the control unit 100 calculates GPS satellites 12a and the like that can be observed at the current time with the initial position P0 as a reference.
The control unit 100 stores the observable satellite information 158 indicating the calculated GPS satellite 12 a and the like in the second storage unit 150.

As illustrated in FIG. 6, the terminal 20 stores the first drift calculation program 1 in the first storage unit 110.
14 is stored. In the first drift calculation program 114, the control unit 100 uses the carrier frequency of the communication signal CS as the reference frequency Hr, and the local oscillator 34a (see FIG. 5).
It is a program for calculating the drift of. The drift calculated using the reference frequency Hr is called a first drift df1. That is, the first drift calculation program 114 and the control unit 100 function as first drift calculation means.
The frequency of the local oscillator 34a is referred to as a positioning side reference frequency Hg.

FIG. 7 is an explanatory diagram of the first drift calculation program 114.
For example, as shown in Equation 2, the control unit 100 can generate a reference frequency Hr and a positioning-side reference frequency Hg.
The first drift df1 is calculated by Expression 2 that divides the difference by the reference frequency Hr.

The control unit 100 stores the first drift information 160 indicating the calculated first drift df <b> 1 in the second storage unit 150.
The controller 100 calculates the first drift df1 at predetermined time intervals during positioning. Here, positioning is synonymous with the operation of the GPS device 34.
The error of the first drift df1 (hereinafter “drift error α1”) is a fixed value. The drift error α1 is a value obtained in the development stage of the terminal 20. First drift information 16
0 includes a drift error α1.

As illustrated in FIG. 6, the terminal 20 stores a first search range calculation program 116 in the first storage unit 110. The first search range calculation program 116 is controlled by the control unit 100.
This is a program for calculating the search range of each signal S1 etc. using the first drift df1. That is, the first search range calculation program 116 and the control unit 100 function as first search range calculation means.
After calculating the first search range SR1 for the first time, the control unit 100 calculates the first search range SR1 only when the search range is updated using the first drift df1 by the search range update program 122 described later. It is supposed to be.

FIG. 8 is an explanatory diagram of the first search range calculation program 116.
For each GPS satellite 12a, etc., the control unit 100, as shown in Equation 3, has a frequency obtained by multiplying the transmission frequency H1, the Doppler shift H2, the first drift df1 of the signal S1, etc. by the frequency conversion coefficient a, and The first search range SR1 is calculated based on the drift error α1.

The control unit 100 includes first search range information 162 indicating the calculated first search range SR1.
Is stored in the second storage unit 150.

As shown in FIG. 6, the terminal 20 stores the second drift calculation program 1 in the first storage unit 110.
18 is stored. The second drift calculation program 118 is transmitted from the control unit 100 to the signal S1.
This is a program for calculating the drift of the local oscillator 34a (see FIG. 5) using the reception frequency Hst. The drift calculated using the reception frequency Hst is referred to as a second drift df2. That is, the second drift calculation program 118 and the control unit 100 are the second
It functions as a drift calculation means.

FIG. 9 is an explanatory diagram of the second drift calculation program 118.
The control unit 100 calculates the second drift df2 using the strong signal of the strong satellite among the received signals S1 and the like. For example, a satellite corresponding to a signal intensity of minus (−) 150 dBm or more is a strong satellite.
First, as shown in Expression 4, the control unit 100 calculates the expected reception frequency Hest based on the transmission frequency H1 such as the signal S1 and the Doppler shift H2.
Subsequently, as shown in Equation 5, the control unit 100 receives the reception frequency Hst and the expected reception frequency He.
The second drift df2 is calculated by calculating the difference from st.
The control unit 100 stores the second drift information 164 indicating the calculated second drift df2 in the second storage unit 150.
The control unit 100 also calculates the second drift df2 when the positioning calculation converges even when the signal from the strong satellite cannot be received. In this case, the control unit 100 calculates a difference between the reception frequency Hst and the expected reception frequency Hest for each of the plurality of satellites used for the converged positioning calculation, and calculates an average value of the plurality of differences. The average value of the plurality of differences is the second drift df
2.
The control unit 100 calculates the second drift df2 when a signal from a strong satellite is received or when the positioning calculation converges. The time interval for calculating the second drift df2 is not necessarily constant, and is usually longer than the time interval for calculating the first drift df1.

The error of the second drift df2 (hereinafter referred to as “drift error α2”) is a fixed value.
The drift error α2 is a value obtained in the development stage of the terminal 20. Drift error α
2 is smaller than the drift error α1.
This is because the accuracy of the expected reception frequency Hest is higher than the accuracy of the reference frequency Hr.
The second drift information 164 includes a drift error α2.

As illustrated in FIG. 6, the terminal 20 stores a second search range calculation program 120 in the first storage unit 110. The second search range calculation program 120 is controlled by the control unit 100.
This is a program for calculating the search range of each signal S1 and the like using the second drift df2. That is, the second search range calculation program 120 and the control unit 100 function as second search range calculation means. In addition, the control unit 100 may update the already calculated search range using the second drift df2. Therefore, the second search range calculation program 120 and the control unit 100 also function as basic update means.

FIG. 10 is an explanatory diagram of the second search range calculation program 120.
For each GPS satellite 12a or the like, the control unit 100 determines the second search range SR2 based on the transmission frequency H1, the Doppler shift H2, the second drift df2, and the drift error α2 of the signal S1 or the like as shown in Expression 6. Is calculated.

The control unit 100 performs second search range information 166 indicating the calculated second search range SR2.
Is stored in the second storage unit 150.

As illustrated in FIG. 6, the terminal 20 stores the search range update program 1 in the first storage unit 110.
22 is stored. The search range update program 122 is a program for the control unit 100 to update the search range using the first drift df1 or the second drift df2. The search range update program 122 and the control unit 100 function as intermediate update means.

11 to 18 are explanatory diagrams of the search range update program 122. FIG.
As illustrated in FIG. 11, when the new second drift df2 is calculated, the control unit 100 updates the search range using the second drift df2. That is, the control unit 10
0 always calculates the second search range SR2 when the second drift df2 is calculated,
The second search range SR2 is set as a new search range. The search range update using the second drift df2 is referred to as basic update.
However, when the condition described below is satisfied, the search range is updated using the first drift df1 while the second drift df2 is calculated and the second search range is updated.

As illustrated in FIG. 12, the control unit 100 uses Equation 7 to calculate the fluctuation amount Δd of the drift df1.
f1 is calculated. Specifically, the control unit 100 first calculates the first drift df1 (0
) And the first drift df1 (t) calculated at time t, the fluctuation amount Δdf1
Is calculated. The fluctuation amount Δdf1 is a cumulative value (or total amount) of fluctuation amounts of drift since the first drift df1 was first calculated.
Then, the control unit 100 determines that the fluctuation amount Δdf1 is a drift error α2 of the second drift df2.
Or greater than that.
If the control unit 100 determines that the fluctuation amount Δdf1 is larger than the drift error α2, the control unit 100 calculates the first search range SR1 using the first drift df1 and sets it as a new search range. Update of the search range using the first drift df1 is called intermediate update.
The condition that the fluctuation amount Δdf1 is larger than the drift error α2 is referred to as an intermediate update execution condition.

Unlike the present embodiment, the control unit 100 may calculate the fluctuation rate of the first drift df1, and may calculate the fluctuation amount Δdf1 based on the fluctuation rate and the elapsed time. Further, the variation rate may be updated at a predetermined time interval.

The advantages of the search range update method will be described below with reference to FIGS.
As shown in FIG. 13, the reception frequency (reception frequency down-converted inside the terminal 20) varies with time. This is because the temperature rises and the drift of the local oscillator 34a fluctuates as time elapses from the activation of the GPS device 34.
In FIG. 13 and the like, for convenience of explanation, the change of the reception frequency is shown linearly, but actually, it does not necessarily change linearly.

As shown in FIG. 14, it is assumed that the first drift df1 is calculated and the first search range SR1 is set at time t1. Then, the second drift df2 is calculated at time t3,
It is assumed that the second search range SR2 is calculated and set as a new search range.
Then, it is assumed that the next calculation of the second drift df2 is time t7.
In this case, depending on the drift fluctuation amount, the reception frequency goes out of the search range SR2 set at time t3.
In the example of FIG. 14, the reception frequency is out of the search range SR2 at time t4.5. For this reason, the signal S1 or the like cannot be received from the time t4.5 to the time t7.

On the other hand, as shown in FIG. 15, when the fluctuation amount of the reception frequency is small, the reception frequency does not go out of the search range SR2 until the next calculation of the second drift df2.
Whether or not the reception frequency goes out of the search range SR2 is defined until the next calculation of the second drift df2 by the amount of fluctuation of the reception frequency, that is, the amount of fluctuation of the local oscillator 34a.

Note that, as shown in FIG. 16, the actual fluctuation of the reception frequency varies in a curved manner. If a certain time elapses from the GPS device 34, the temperature change is also reduced, so that the drift fluctuation is also reduced and the reception frequency fluctuation is also reduced.

As illustrated in FIG. 17, when the control unit 100 determines that the fluctuation amount Δdf1 is larger than the drift error α2, for example, the control unit 100 calculates the first search range SR1 at time t5,
Use a new search range.
Thereby, the state where the reception frequency goes out of the search range is eliminated.

As shown in FIG. 18, the shorter the calculation time interval of the first drift df1, the earlier the state where the reception frequency goes out of the search range is resolved.

As illustrated in FIG. 6, the terminal 20 stores a positioning program 124 in the first storage unit 110. The positioning program 124 is a program for the control unit 100 to measure the current position and calculate the positioning position P1 using the signal S1 and the like.

The control unit 100 stores positioning position information 168 indicating the positioning position P1 in the second storage unit 150.

As illustrated in FIG. 6, the terminal 20 stores the positioning position output program 126 in the first storage unit 110.
Is stored.
The positioning position output program 126 is a program for the control unit 100 to display the positioning position P1 on the display device 36.

The terminal 20 is configured as described above.
The terminal 20 can update the search range with the first drift df1 while calculating the second drift df2. That is, during the calculation of the second drift df2, it is possible to shorten the duration of the state where the reception frequency is out of the search range due to drift fluctuation during reception of a signal from a strong satellite.
The search range is updated by the first drift df1 only during the calculation of the second drift df2. This is because when a new second drift df2 is calculated,
This means that the search range is updated by the second drift df2. Here, the drift error α2 of the second drift df2 is smaller than the drift error α1 of the first drift df1.
For this reason, it is possible to restrict the search range from being widened by using the first drift df1 calculated using the reference frequency Hr.
Accordingly, the duration of the state in which the reception frequency is out of the search range due to drift fluctuation during the calculation of the second drift df2 is shortened while limiting the search range from being widened by using the first drift df1. be able to.

In addition, the search range is updated by the first drift df1 because the first drift fluctuation amount Δdf
This is performed when 1 is larger than the drift error α2 of the second drift df2.

When the search range is updated using the second drift df2, the center frequency of the search range is defined based on the second drift df2, and the bandwidth of the search range is the second drift df.
2 is defined based on a drift error α2.
The drift error α1 of the first drift df1 is usually larger than the drift error α2 of the second drift df2, but the fluctuation amount Δdf1 of the first drift df1 is measured by measuring the second drift df2 at the same time. It is thought that it is the same as that.
The fact that the fluctuation amount Δdf1 of the first drift df1 is larger than the drift error α2 of the second drift df2 means that the reception frequency may be out of the search range due to drift fluctuation.
In this respect, since the terminal 20 is performed when the fluctuation amount Δdf1 of the first drift df1 is larger than the drift error α2 of the second drift df2, the terminal 20 shortens the duration of the state where the reception frequency is out of the search range. Can do.

The above is the configuration of the terminal 20 of the present embodiment. Hereinafter, an example of the operation will be mainly described with reference to FIG.
FIG. 19 is a schematic flowchart showing an operation example of the terminal 20 of the present embodiment.

First, when starting the GPS device 34, the terminal 20 calculates a first drift df1 (step ST1 in FIG. 19). This step ST1 is an example of a first drift calculation step. Note that the terminal 20 continuously performs step ST1 while the GPS device 34 is in operation.
Subsequently, the terminal 20 calculates the first search range SR1 using the first drift df1 (step ST2). This step ST2 is an example of a search range calculation step.

Subsequently, the terminal 20 starts searching and tracking (step ST3). In addition,
The terminal 20 first searches each satellite 12a and the like, and starts tracking the satellite for which the search has been completed.
And the terminal 20 continues search and tracking (step ST4). Terminal 2
0 continues the search for satellites for which the search has not been completed, and continues tracking for satellites for which the search has been completed.

Subsequently, the terminal 20 determines whether a strong satellite has been received or the positioning calculation has converged (step ST5).
If the terminal 20 determines in step ST5 that it has not received a strong satellite and the positioning calculation has not converged, the process returns to step ST4.
On the other hand, in step ST5, if the terminal 20 receives a strong satellite or determines that the positioning calculation has converged, the second drift df2 is calculated (step ST6).
). This step ST6 is an example of a second drift calculating step.

Subsequently, the terminal 20 calculates the second search range SR2 using the second drift df2 (step ST7 in FIG. 20). Step ST7 is an example of a second update step.
Subsequently, the terminal 20 continues searching and tracking (step ST8).

Subsequently, the terminal 20 determines whether or not the intermediate update execution condition is satisfied (step ST9).
. Specifically, the terminal 20 determines whether or not the fluctuation amount Δdf1 is larger than the drift error α2.
In step ST9, when the terminal 20 determines that the intermediate update execution condition is satisfied, the terminal 20 updates the search range using the first drift df1 (step ST1).
0). This step ST10 is an example of an intermediate update step.

Subsequently, the terminal 20 determines whether or not the positioning is completed (step ST11), and ends if the positioning is completed. If the positioning is not completed, step ST4 and subsequent steps are repeated.

In step ST9 described above, when the terminal 20 determines that the intermediate update execution condition is not satisfied, the terminal 20 waits for calculation of a new second drift df2 and updates the search range using the second drift df2 ( Step ST12).

Through the above steps, while limiting the search range to be widened by using the first drift df1, the duration of the state where the reception frequency deviates from the search range due to drift fluctuation during the calculation of the second drift df2 is shortened. Can be

(Second Embodiment)
Next, a second embodiment will be described.
Since the configuration of the terminal 20A in the second embodiment is similar to that of the terminal 20 in the first embodiment, the common parts are denoted by the same reference numerals, the description thereof will be omitted, and the following differences will be described. The explanation will be focused on.

FIG. 21 is a schematic diagram illustrating a main software configuration of the terminal 20A.
As illustrated in FIG. 21, the terminal 20 </ b> A stores a second search range invalid time calculation program 128 in the first storage unit 110.

FIG. 22 is an explanatory diagram of the second search range invalid time calculation program 128.
The control unit 100 calculates time t (x), which is a timing at which the reception frequency of the signal S1 and the like deviates from the search range updated by the second drift df2 due to drift of the local oscillator 34a, using Equation 8.
Specifically, it is calculated from the previous calculation time (t) of the second drift df2, the drift error α2 of the second drift df2, and the fluctuation rate dfratio of the first drift df1.
The fluctuation rate dfratio is, for example, the difference between the first drift df1 (t) at time (t) and the first drift df1 (t + 1) at time (t + 1) from time (t) to time (
It is calculated by dividing by the elapsed time Δt to t + 1).

As illustrated in FIG. 21, the terminal 20A stores a search range update program 122A in the first storage unit 110. The search range update program 122A is controlled by the control unit 100.
This is a program for calculating the first search range SR1 with the first drift df1 calculated immediately before the time t (x) to obtain a new search range.

23 and 24 are explanatory diagrams of the search range update program 122A.
As illustrated in FIG. 23, the control unit 100 updates the search range before the reception frequency is out of the search range.
Thereby, as shown in FIG. 24, it is possible to prevent the reception frequency from deviating from the search range.

Also, as shown in FIG. 23, the control unit 100 updates the search range with the first drift df1 when the variation rate dfratio is not within the threshold γ.
And the control part 100 stops calculation of the 1st drift df1 for a fixed period, when the fluctuation rate dfratio is less than threshold value (gamma).
The threshold γ is defined by the approximate calculation interval Δtdf2 of the second drift df2 and the drift error α2 of the second drift df2. The calculation interval Δtdf2 is, for example, an average time at the previous positioning.
If the variation rate dfratio is within the threshold γ, the reception frequency will not deviate from the search range during the calculation of the second drift df2. Therefore, the signal S1 and the like can be received using the second search range SR2 whose bandwidth is narrower than the first search range SR1. Since the calculation of the first drift df1 is stopped, for example, battery consumption of the portable terminal device can be saved.

(About programs and computer-readable recording media)
A terminal device control program for causing a computer to execute the first drift calculation step, the search range calculation step, the second drift calculation step, the basic update step, the intermediate update step, and the like of the above-described operation example. it can.
Moreover, it can also be set as the computer-readable recording medium etc. which recorded the control program etc. of such a terminal device.

A program storage medium used for installing the control program of the terminal device in the computer and making it executable by the computer is, for example, a flexible disk such as a floppy (registered trademark), a CD-ROM (Compact Disc).
Read Only Memory), CD-R (Compact Disc-Rec)
ordable), CD-RW (Compact Disc-Rewriteable),
Not only a package medium such as a DVD (Digital Versatile Disc) but also a semiconductor memory, a magnetic disk, or a magneto-optical disk in which a program is temporarily or permanently stored can be realized.

  The present invention is not limited to the above-described embodiment.

It is the schematic which shows the terminal etc. of embodiment of this invention. It is a conceptual diagram which shows an example of a positioning method. It is explanatory drawing of a correlation process. It is explanatory drawing of a correlation process. It is the schematic which shows the main hardware constitutions of a terminal. It is the schematic which shows the main software structures of a terminal. It is explanatory drawing of a 1st drift calculation program. It is explanatory drawing of a 1st search range calculation program. It is explanatory drawing of a 2nd drift calculation program. It is explanatory drawing of the 2nd search range calculation program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update 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. It is the schematic which shows the main software structures of a terminal. It is explanatory drawing of the 2nd search range invalid time calculation program. It is explanatory drawing of a search range update program. It is explanatory drawing of a search range update program.

Explanation of symbols

12a, 12b, 12c, 12d ... GPS satellites, 20 ... terminals, 112 ... observable satellite calculation program, 114 ... first drift calculation program, 116 ... first search range calculation program, 118... Second drift calculation program, 120.
-Second search range calculation program, 122, 122A ... search range update program

Claims (8)

A method of updating a search range of the satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of positioning satellites,
A first drift calculating step of calculating a first drift of the local oscillator at a first time interval using a reference frequency received from the base station;
A second drift calculating step of calculating a second drift of the local oscillator at a second time interval using a reception frequency of the satellite signal;
Calculating a variation amount of the first drift;
Comparing a variation amount of the first drift with a second drift error value corresponding to an error included in the second drift;
Updating the search range using the first drift when the variation amount of the first drift is larger than the second drift error value;
A search range update method characterized by comprising:   The search range update method according to claim 1, wherein the first time interval is shorter than the second time interval. The variation amount of the first drift, the search according to any one of claims 1 or 2, characterized in that it is calculated by accumulating the change amounts of the first drift in said first time interval Range update method.   The search range update method according to claim 1, wherein the second drift error value is a predetermined constant. Calculating a variation amount of the second drift;
Comparing the variation amount of the first drift with the variation amount of the second drift;
Stopping the calculation of the first drift over a predetermined period when the fluctuation amount of the first drift is smaller than the fluctuation amount of the second drift, and updating the search range using the second drift; and ,
The search range update method according to claim 1, further comprising: A method of updating a search range of the satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of positioning satellites in a computer,
A first drift calculating step of calculating a first drift of the local oscillator at a first time interval using a reference frequency received from the base station;
A second drift calculating step of calculating a second drift of the local oscillator at a second time interval using a reception frequency of the satellite signal;
Calculating a variation amount of the first drift;
Comparing the variation amount of the first drift with a second drift error value that is an error included in the second drift;
Updating the search range using the first drift when the variation amount of the first drift is larger than the second drift error value;
A control program for a terminal device, characterized in that A method of updating a search range of the satellite signal in a terminal device that performs positioning by receiving satellite signals from a plurality of positioning satellites on a computer,
A first drift calculating step of calculating a first drift of the local oscillator at a first time interval using a reference frequency received from the base station;
A second drift calculating step of calculating a second drift of the local oscillator at a second time interval using a reception frequency of the satellite signal;
Calculating a variation amount of the first drift;
Comparing the variation amount of the first drift with a second drift error value that is an error included in the second drift;
Updating the search range using the first drift when the variation amount of the first drift is larger than the second drift error value;
A computer-readable recording medium on which a control program for a terminal device is recorded. A terminal device that performs positioning by receiving satellite signals from a plurality of positioning satellites,
First drift calculating means for calculating a first drift of the local oscillator at a first time interval using a reference frequency received from the base station;
Second drift calculating means for calculating a second drift of the local oscillator at a second time interval using a reception frequency of the satellite signal;
First drift fluctuation amount calculating means for calculating the fluctuation amount of the first drift;
A comparison means for comparing a fluctuation amount of the first drift with a second drift error value that is an error included in the second drift;
Search range updating means for updating the search range using the first drift when the fluctuation amount of the first drift is larger than the second drift error value;
The terminal device characterized by having.

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