JP2011164088A - Method for tracking satellite signal, method for calculating position, device for tracking satellite signal and device for calculating position - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a new method for setting a loop bandwidth of a loop filter for tracking a satellite signal at an appropriate value. <P>SOLUTION: In a mobile phone 1, a state of movement is detected by IMU 60. Besides, an assumed maximum detection error of the IMU 60 is calculated by host CPU 30. Then, the loop bandwidth of a loop filter part of a loop circuit for tracking a GPS satellite signal received from a GPS satellite is set by the processing part 27 of a base band processing circuit part 20, using the result of detection of the IMU 60 and the assumed maximum detection error thereof. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a satellite signal tracking method, a position calculation method, a satellite signal tracking device, and a position calculation device.

  A GPS (Global Positioning System) is widely known as a positioning system using positioning signals, and is used in a position calculation device built in a mobile phone or a car navigation device. In the GPS, position calculation calculation for obtaining position coordinates and clock error of the position calculation device is performed based on information such as positions of a plurality of GPS satellites and pseudo distances from each GPS satellite to the position calculation device.

  A GPS satellite signal transmitted from a GPS satellite is modulated with a spreading code different for each GPS satellite called a CA (Coarse and Acquisition) code. In order to capture a GPS satellite signal from a weak received signal, the position calculation device performs a correlation operation between the received signal and a replica code that is a replica of the CA code, and calculates the GPS satellite signal based on the correlation value. To capture. Once the GPS satellite signal is successfully captured, the captured GPS satellite signal is tracked.

  Tracking of GPS satellite signals is performed by a carrier tracking loop circuit for tracking a carrier wave (carrier), a code tracking loop circuit for tracking the phase of a CA code, or the like (for example, Patent Document 1).

JP 2008-232761 A

  In a loop circuit, it is known that noise components are mixed in a signal due to various factors. In order to remove this noise component, the loop circuit is generally provided with a loop filter such as a low-pass filter.

  In particular, the resistance to jitter (shift in the time axis direction of the signal, phase fluctuation, and frequency fluctuation) is almost determined by the loop filter. If the loop bandwidth of the loop filter is narrowed, the tolerance to jitter will increase, but part of the signal component may be cut, resulting in poor signal tracking and capture in extreme cases. There is a problem that the GPS satellite signal that has been lost is easily lost. However, when the loop bandwidth is widened, the tolerance to jitter is lowered, and in an extreme case, the lock (tracking of the GPS satellite signal) may not be possible.

  Conventionally, when designing a loop filter, the loop bandwidth value is fixedly determined in consideration of the above-described balance, and the loop filter is configured. However, the jitter to be mixed may vary due to noise components such as thermal noise (thermal noise) and dynamic stress (dynamic stress). In particular, the dynamic stress can vary greatly depending on the movement status of the position calculation device. For this reason, when a fixed loop bandwidth is used, there may be a problem that the follow-up performance for tracking a GPS satellite signal is lowered.

  The present invention has been made in view of the above-described problems, and its object is to propose a new technique for setting the loop bandwidth of a loop filter for tracking satellite signals to an appropriate value. It is in.

  A first mode for solving the above problems is to detect a moving state, calculate an error of the detection, and a satellite signal received from a positioning satellite using the detection result and the error. And setting the loop bandwidth of a tracking filter that can be used for tracking and capable of changing the loop bandwidth.

  Further, as another form, a detection unit that detects a movement state, a detection result of the detection unit, and a detection error of the detection unit are used for tracking a satellite signal received from a positioning satellite, and a loop band You may comprise the satellite signal tracking apparatus provided with the setting part which sets the said loop bandwidth of the filter for tracking which can change a width | variety.

  According to the first form and the like, the movement state is detected. In addition, an error in detecting the movement state is calculated. Then, using the detection result and detection error of the movement status, the loop bandwidth of the tracking filter that is used for tracking the satellite signal received from the positioning satellite and that can change the loop bandwidth is set.

  As described above, the jitter of the loop circuit can vary greatly depending on the movement situation. Therefore, it is appropriate to set the loop bandwidth of the tracking filter using the detection result of the movement state. However, naturally the error may be included in the detection result of the movement state. Therefore, the loop bandwidth can be set to an appropriate value by setting the loop bandwidth in consideration of the detection error of the movement situation in addition to the detection result of the movement situation.

  Further, as a second mode, in the satellite signal tracking method according to the first mode, the movement state may be detected by using at least one of an acceleration sensor, a speed sensor, and a gyro sensor. Performing the calibration process on the output of any one of the sensors at the timing of calculating the error using the elapsed time from the execution of the calibration process. In addition, a satellite signal tracking method may be configured.

  According to the second embodiment, the calibration process for the output of any sensor is executed at a given timing using at least one of an acceleration sensor, a speed sensor, and a gyro sensor. Then, using the elapsed time since the execution of the calibration process, an error in detecting the movement state is calculated. By executing the calibration process, the movement state detection error can be reset. Further, by using the elapsed time since the execution of the calibration process, it is possible to easily determine the movement state detection error, which contributes to the appropriate setting of the loop bandwidth.

  Further, as a third mode, in the satellite signal tracking method according to the first or second mode, setting the loop bandwidth sets the loop bandwidth using a reception environment of the satellite signal. In addition, a satellite signal tracking method may be configured.

  According to the third embodiment, an appropriate loop bandwidth can be set according to the satellite signal reception environment.

  According to a fourth aspect, in the satellite signal tracking method according to any one of the first to third aspects, the loop band width is set by using the filter order of the tracking filter. A satellite signal tracking method including setting the width may be configured.

  According to the fourth embodiment, an appropriate loop bandwidth can be set according to the filter order of the tracking filter.

  Further, as a fifth mode, the satellite signal tracking method according to any one of the first to fourth modes is performed to track the satellite signal and to calculate a position using the tracked satellite signal. And a position calculation method including:

  According to the fifth embodiment, the position calculation accuracy can be improved by calculating the position using the satellite signal tracked by the satellite signal tracking method described above.

  Further, as a seventh form, from at least one of an acceleration sensor, a speed sensor, and a gyro sensor, a movement state detection unit that detects a movement state using an output of the at least one sensor, and a positioning satellite Of the tracking filter using the tracking filter that can be used to track the satellite signal and capable of changing the loop bandwidth, the detection result of the movement status detection unit, and the detection error of the movement status detection unit. You may comprise the position calculation apparatus provided with the setting part which sets a loop bandwidth, and the position calculation part which calculates a position using the satellite signal tracked by the said filter for tracking.

  According to the seventh aspect, the movement state is detected by the movement state detection unit using the output of at least one of the acceleration sensor, the speed sensor, and the gyro sensor. The loop bandwidth of the tracking filter that can be used to track the satellite signal from the positioning satellite and that can change the loop bandwidth uses the detection result of the movement status detection unit and the detection error of the movement status detection unit. Is set by the setting unit. Then, the position is calculated by the position calculation unit using the satellite signal tracked by the tracking filter. By such an action, the same effect as the above-described embodiment is exhibited.

The block diagram which shows an example of a function structure of a portable telephone. The block diagram which shows an example of the circuit structure of a baseband process circuit part. The figure which shows the correspondence of the order of a loop filter part, and the physical quantity for dynamic stress calculation. The figure which shows an example of the loop bandwidth characteristic of a thermal noise, a dynamic stress, and a total jitter. The flowchart which shows the flow of a main process. The flowchart which shows the flow of a baseband process. The flowchart which shows the flow of a carrier phase tracking loop bandwidth setting process. The figure which shows an example of the table structure of the table for signal strength determination.

  Hereinafter, an embodiment in which the present invention is applied to a mobile phone which is a kind of electronic apparatus including a satellite signal tracking device and a position calculation device will be described with reference to the drawings. Of course, embodiments to which the present invention can be applied are not limited to the embodiments described below.

1. Functional Configuration FIG. 1 is a block diagram showing a functional configuration of a mobile phone 1 according to this embodiment. The mobile phone 1 includes a GPS antenna 5, a GPS receiver 10, a host CPU (Central Processing Unit) 30, an operation unit 40, a display unit 50, an IMU (Inertial Measurement Unit) 60, and a mobile phone antenna. 70, a mobile phone wireless communication circuit unit 80, and a storage unit 90.

  The GPS antenna 5 is an antenna that receives an RF (Radio Frequency) signal including a GPS satellite signal transmitted from a GPS satellite that is a type of positioning satellite, and outputs a received signal to the GPS receiver 10. The GPS satellite signal is a 1.57542 [GHz] communication signal modulated by a CDMA (Code Division Multiple Access) system known as a spread spectrum system by a CA (Coarse and Acquisition) code which is a kind of spreading code. The CA code is a pseudo-random noise code having a repetition period of 1 ms with a code length of 1023 chips as 1 PN frame, and is different for each GPS satellite.

  The GPS receiving unit 10 is a position calculating circuit or a position calculating device that measures the position of the mobile phone 1 based on a signal output from the GPS antenna 5, and is a functional block corresponding to a so-called GPS receiving device. The GPS receiving unit 10 includes an RF receiving circuit unit 11 and a baseband processing circuit unit 20. The RF receiving circuit unit 11 and the baseband processing circuit unit 20 can be manufactured as separate LSIs (Large Scale Integration) or can be manufactured as one chip.

  The RF receiving circuit unit 11 is an RF signal receiving circuit. As a circuit configuration, for example, a receiving circuit that converts an RF signal output from the GPS antenna 5 into a digital signal by an A / D converter and processes the digital signal may be configured. Alternatively, the RF signal output from the GPS antenna 5 may be processed as an analog signal and finally A / D converted to output a digital signal to the baseband processing circuit unit 20.

  In the latter case, for example, the RF receiving circuit unit 11 can be configured as follows. That is, an oscillation signal for RF signal multiplication is generated by dividing or multiplying a predetermined oscillation signal. Then, by multiplying the generated oscillation signal by the RF signal output from the GPS antenna 5, the RF signal is down-converted to an intermediate frequency signal (hereinafter referred to as an "IF (Intermediate Frequency) signal"), After the IF signal is amplified, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 20.

  The baseband processing circuit unit 20 performs correlation processing or the like on the reception signal output from the RF reception circuit unit 11 to capture and track the GPS satellite signal, and satellite orbit data, time data, and the like extracted from the GPS satellite signal. Is a functional unit that calculates a position (position coordinates) of the mobile phone 1 by performing a predetermined position calculation calculation based on the above.

  The baseband processing circuit unit 20 is a satellite signal capturing device that captures GPS satellite signals from received signals, and is a satellite signal tracking device that tracks captured GPS satellite signals. Further, the position / velocity calculation calculation using the GPS satellite signal is performed to calculate the position and speed of the mobile phone 1.

  FIG. 2 is a diagram illustrating an example of a circuit configuration of the baseband processing circuit unit 20, and mainly describes circuit blocks according to the present embodiment. The baseband processing circuit unit 20 includes a carrier removal unit 21, a satellite signal acquisition unit 23, a satellite signal tracking unit 25, a processing unit 27, and a storage unit 29.

  The carrier removal unit 21 is a circuit unit that removes a carrier wave from the reception signal output from the RF reception circuit unit 11. For example, the carrier removal unit 21 includes a multiplication unit 211 and a carrier removal signal generation unit 213. The

  Multiplier 211 multiplies the received signal by the carrier removal signal generated by carrier removal signal generator 213 to remove the carrier from the received signal, and correlates the CA code (received CA code) included in the received signal. It is a multiplier that outputs to the processing unit 231.

  The carrier removal signal generator 213 is a circuit that generates a carrier removal signal that is a signal having the same frequency as the carrier signal of the GPS satellite signal. When the signal output from the RF receiving circuit unit 11 is an IF signal, the signal is generated using the IF frequency as a carrier frequency. In any case, this is a circuit for generating a carrier removal signal having the same frequency as that of the signal output from the RF receiving circuit unit 11.

  Hereinafter, the signal frequency output from the RF receiving circuit unit 11 is referred to as “carrier frequency” or “carrier frequency”, and the phase of the carrier (carrier wave) component of the signal output from the RF receiving circuit unit 11 is “carrier phase”. This will be explained.

  The carrier removal signal generator 213 generates the phase of the signal to be generated according to the carrier phase indication signal output from the carrier phase tracking loop filter unit 254 and the carrier frequency indication signal output from the carrier frequency tracking loop filter unit 256. The frequency is adjusted to generate a carrier removal signal, which is output to the multiplier 211.

  At this time, the carrier removal signal generator 213 generates a carrier removal signal in consideration of the Doppler frequency output from the Doppler calculator 275. The frequency at which the GPS receiving unit 10 receives the GPS satellite signal is 1.57542 [GHz], which is the specified carrier frequency of the GPS satellite signal, due to the influence of Doppler caused by the movement of the GPS satellite or the movement of the mobile phone 1. Does not necessarily match. Therefore, a carrier removal signal having a frequency in which the Doppler frequency is added to the specified carrier frequency is generated and output to the multiplier 211.

  The satellite signal acquisition unit 23 is a circuit unit that acquires a GPS satellite signal from the reception signal from which the carrier wave output from the multiplication unit 211 is removed. The satellite signal acquisition unit 23 includes a correlation processing unit 231 and a replica code generation unit 233. The

  The correlation processing unit 231 includes, for example, a correlator (correlator), and performs a correlation process between the replica code generated by the replica code generation unit 233 and the reception CA code output from the multiplication unit 211. It is. The correlation processing unit 231 integrates the correlation values over the correlation integration time output from the correlation integration time determination unit 271 and outputs the integration result to the processing unit 27.

  The replica code generating unit 233 is a circuit unit that generates a CA code replica code (CA code replica) that is a spreading code of a GPS satellite signal. The replica code generation unit 233 generates three types of replica codes, Early, Prompt, and Late, according to the code phase instruction signal output from the code tracking loop filter unit 252. Then, the generated three types of replica codes are output to the correlation processing unit 231.

  In the present embodiment, the correlation processing unit 231 performs correlation processing on each IQ component of the received signal with the replica code input from the replica code generating unit 233. The I component indicates the in-phase component (real part) of the received signal, and the Q component indicates the quadrature component (imaginary part) of the received signal. Since the replica code generation unit 233 outputs three types of replica codes, Early, Prompt, and Late, the correlation processing unit 231 performs correlation processing with the three types of replica codes for each IQ component of the received signal. .

  In addition, although illustration is abbreviate | omitted about the circuit block which isolate | separates IQ component (IQ isolation | separation) of a received signal, you may comprise a circuit block how. For example, when the received signal is down-converted to an IF signal in the RF receiving circuit unit 11, IQ separation may be performed by multiplying the received signal by a local oscillation signal having a phase difference of 90 degrees.

  The satellite signal tracking unit 25 is a circuit unit that tracks the GPS satellite signal captured by the satellite signal capturing unit 23, and includes a code phase difference calculation unit 251, a code tracking loop filter unit 252, and a carrier phase difference calculation unit 253. The carrier phase tracking loop filter unit 254, the carrier frequency difference calculation unit 255, and the carrier frequency tracking loop filter unit 256 are configured.

  The code phase difference calculation unit 251 is a phase comparator that calculates and outputs a phase difference between the phase of the received CA code and the phase of the replica code (hereinafter referred to as “code phase difference”). The code phase difference calculation unit 251 calculates the power for the Early code and the power for the Late code by using the IQ correlation value for the Early code output from the correlation processing unit 231 and the IQ correlation value for the Late code, respectively. . Then, using the calculated power, a code phase difference is calculated according to a known calculation method, a signal (voltage) corresponding to the calculated code phase difference is generated, and output to the code tracking loop filter unit 252.

  The code tracking loop filter unit 252 is configured to include, for example, a low-pass filter, and is designed so that the loop bandwidth, which is a parameter for determining the frequency band component of the signal to be passed, is variably set, that is, the loop bandwidth can be adjusted. Filter circuit. The code tracking loop filter unit 252 sets the loop bandwidth according to the loop bandwidth output from the loop bandwidth setting unit 273. That is, the loop bandwidth is changed according to the loop bandwidth output from the loop bandwidth setting unit 273. The high frequency component included in the signal corresponding to the code phase difference output from the code phase difference calculation unit 251 is cut and output to the replica code generation unit 233. The loop bandwidth of the code tracking loop filter unit 252 is illustrated and described as an appropriate “code tracking loop bandwidth”.

  Correlation processing unit 231 → code phase difference calculation unit 251 → code tracking loop filter unit 252 → replica code generation unit 233 → code phase known as a delay locked loop (DLL (Delay Locked Loop)) by a closed circuit of correlation processing unit 231 A loop circuit for tracking is formed.

  The carrier phase difference calculation unit 253 is a phase difference between the phase of the carrier component of the received signal and the phase of the carrier removal signal generated by the carrier removal signal generation unit 213 (hereinafter referred to as “carrier phase difference”). Is a phase comparator that calculates and outputs. The carrier phase difference calculation unit 253 uses the IQ correlation values for the Early, Prompt, and Late codes output from the correlation processing unit 231 to calculate the carrier phase difference according to a known calculation method. Then, a signal (voltage) corresponding to the calculated carrier phase difference is generated and output to the carrier phase tracking loop filter unit 254.

  The carrier phase tracking loop filter unit 254 sets the loop bandwidth according to the carrier phase tracking loop bandwidth output from the loop bandwidth setting unit 273. Then, similarly to the code tracking loop filter unit 252, the carrier phase tracking loop filter unit 254 cuts the high frequency component mixed in the signal corresponding to the carrier phase difference output from the carrier phase difference calculation unit 253 and removes the carrier. To the signal generator 213. The loop bandwidth of the carrier phase tracking loop filter unit 254 is illustrated and described as “carrier phase tracking loop bandwidth” as appropriate.

  Multiplier 211 → correlation processing unit 231 → carrier phase difference calculation unit 253 → carrier phase tracking loop filter unit 254 → carrier removal signal generation unit 213 → phase locked loop (PLL (Phase Locked Loop)) by closed circuit of multiplication unit 211 A loop circuit for tracking the carrier phase known as) is formed.

  The carrier frequency difference calculation unit 255 calculates and outputs the frequency difference between the carrier frequency and the frequency of the carrier removal signal generated by the carrier removal signal generation unit 213 (hereinafter referred to as “carrier frequency difference”). This is a frequency comparator. The carrier frequency difference calculation unit 255 calculates the carrier frequency difference according to a known calculation method using the IQ correlation values for the Early, Prompt, and Late codes output from the correlation processing unit 231. Then, a signal (voltage) corresponding to the calculated carrier frequency difference is generated and output to the carrier frequency tracking loop filter 256.

  The carrier frequency tracking loop filter unit 256 sets the loop bandwidth according to the carrier frequency tracking loop bandwidth output from the loop bandwidth setting unit 273. Then, similarly to the code tracking loop filter unit 252, the carrier frequency tracking loop filter unit 256 cuts a high frequency component included in the signal corresponding to the carrier frequency difference output from the carrier frequency difference calculation unit 255 and removes the carrier frequency. The signal is output to the signal generator 213. The loop bandwidth of the carrier frequency tracking loop filter unit 256 is illustrated and described as “carrier frequency tracking loop bandwidth” as appropriate.

  Multiplier 211 → correlation processing unit 231 → carrier frequency difference calculation unit 255 → carrier frequency tracking loop filter unit 256 → carrier removal signal generation unit 213 → frequency locked loop (FLL (Frequency Locked Loop)) ) Is formed as a loop circuit for tracking the carrier frequency.

  The processing unit 27 is a control device that comprehensively controls each functional unit of the baseband processing circuit unit 20, and includes a processor such as a CPU, for example. The processing unit 27 includes a correlation integration time determination unit 271, a loop bandwidth setting unit 273, a Doppler calculation unit 275, and a position / velocity calculation unit 277 as functional units.

  The correlation integration time determination unit 271 is a determination unit that determines an integration time (correlation integration time) when the correlation processing unit 231 performs correlation value integration processing, and outputs the determined correlation integration time to the correlation processing unit 231. .

  The loop bandwidth setting unit 273 is a setting unit that individually sets the loop bandwidth of each loop filter unit included in the satellite signal tracking unit 25, and outputs the set loop bandwidth to the corresponding loop filter unit.

  The Doppler calculation unit 275 is a calculation unit that calculates the Doppler frequency generated by the movement of the GPS satellite and the mobile phone 1 using the speed of the mobile phone 1 and the speed of the GPS satellite, and removes the calculated Doppler frequency as a carrier. To the signal generator 213.

  The position / velocity calculation unit 277 performs a known position / velocity calculation calculation using a GPS satellite signal captured by the satellite signal acquisition unit 23 or tracked by the satellite signal tracking unit 25, and is portable. It is a calculation part which calculates the position and speed of the telephone 1. The position / speed calculation unit 277 outputs the calculated position and speed to the host CPU 30.

  The storage unit 29 is configured by a storage device such as a ROM, a flash ROM, or a RAM, and various programs for realizing a system program of the baseband processing circuit unit 20, a loop bandwidth setting function, a position / speed calculation function, etc. Data etc. are memorized. In addition, it has a work area for temporarily storing data being processed and results of various processes.

  Returning to the functional blocks in FIG. 1, the host CPU 30 is a processor that comprehensively controls each unit of the mobile phone 1 according to various programs such as a system program stored in the storage unit 90. Based on the position coordinates output from the baseband processing circuit unit 20, the host CPU 30 displays a map indicating the current position on the display unit 50, or uses the position coordinates for various application processes.

  The operation unit 40 is an input device configured by, for example, a touch panel, a button switch, or the like, and outputs a pressed key or button signal to the host CPU 30. By operating the operation unit 40, various instructions such as a call request, a mail transmission / reception request, and a position calculation request are input.

  The display unit 50 is configured by an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on display signals input from the host CPU 30. The display unit 50 displays a position display screen, time information, and the like.

  The IMU 60 includes, for example, an acceleration sensor 61 and a gyro sensor 63, and can detect the acceleration in the axial direction of each of the three orthogonal axes of the sensor coordinate system determined in advance in association with the sensor and the angular velocity around each axis. Composed. The acceleration sensor 61 and the gyro sensor 63 may be independent sensors or may be integrated sensors.

  The cellular phone antenna 70 is an antenna that transmits and receives cellular phone radio signals to and from a radio base station installed by a communication service provider of the cellular phone 1.

  The cellular phone wireless communication circuit unit 80 is a cellular phone communication circuit unit configured by an RF conversion circuit, a baseband processing circuit, and the like, and by performing modulation / demodulation of the cellular phone radio signal, the communication and mail Realize transmission / reception and so on.

  The storage unit 90 is a storage device that stores a system program for the host CPU 30 to control the mobile phone 1, various programs and data for realizing the calibration function of the IMU 60, and the like.

2. Next, the principle of loop bandwidth setting executed by the loop bandwidth setting unit 273 of the processing unit 27 in the baseband processing circuit unit 20 will be described.

(1) Setting of Loop Bandwidth of Carrier Phase Tracking Loop Filter Unit First, the principle of setting the loop bandwidth of the carrier phase tracking loop filter unit 254 will be described. The problem in tracking the carrier phase in the carrier phase tracking loop circuit is the presence of errors that can be included in the carrier phase to be tracked. The main factors of this carrier phase error are noise components called thermal noise and dynamic stress.

  Thermal noise is a noise component known as thermal noise, and is distributed over the entire frequency band mixed in the signal in the carrier phase tracking loop circuit. Dynamic stress is dynamic signal fluctuation known as dynamic stress, and is caused by a change in the pseudorange between the GPS receiver and the GPS satellite due to the movement of the GPS satellite and the GPS receiver. It is phase fluctuation.

In order to explain specifically, carrier phase fluctuation in the carrier phase tracking loop circuit is formulated. Here, the carrier phase fluctuation is formulated by angle conversion (deg). The total jitter “σ _PLL ”, which is the total amount of carrier phase fluctuation in the carrier phase tracking loop, is given by the following equation (1).

In Equation (1), “σ _tPLL ” indicates thermal noise, and “θ _en ” indicates dynamic stress. Further, “σ _v ” and “θ _A ” indicate carrier phase fluctuation due to vibration and carrier phase fluctuation due to Allan dispersion, respectively, but these values are negligibly small and are not considered in this embodiment. I will do it.

The thermal noise “σ _tPLL ” is given by the following equation (2).

In Expression (2), “B _PLL ” is the loop bandwidth of the carrier phase tracking loop filter unit 254. “S” is the signal strength of the received signal expressed as a C / N ratio, and “T” is the correlation integration time. From Equation (2), the thermal noise “σ _tPLL ” depends on the loop bandwidth “B _PLL ” of the carrier phase tracking loop filter unit 254, the signal strength “S” of the received signal, and the correlation integration time “T”. It turns out that it is a value to do.

Further, the dynamic stress “θ _en ” in the carrier phase tracking loop circuit is formulated by a different formula depending on the order of the carrier phase tracking loop filter unit 254 (the order of the loop filter). Specifically, the dynamic stresses “θ _e1 ” to “θ _e3 ” are given by the following equations (3) to (5) for the respective orders of the first to third order loop filters.

In Expressions (3) to (5), “R” is a pseudo distance between the GPS receiver and the GPS satellite. “DR / dt” is the speed (true speed) of the GPS receiver with respect to the line-of-sight direction from the GPS receiver toward the GPS satellite, and “dR ² / dt ² ” is the acceleration (true) of the GPS receiver with respect to the line-of-sight direction. “DR ³ / dt ³ ” is the jerk (= jerk) (true jerk) of the GPS receiver with respect to the line-of-sight direction. “Α”, “β”, and “γ” are constants that differ depending on the order of the filter.

Looking at the equations (3) to (5), the dynamic stress “θ _en ” indicates the GPS receiver speed “dR / dt”, acceleration “dR ² / dt ² ” and jerk according to the order of the loop filter. It can be seen that the line-of-sight direction component of “dR ³ / dt ³ ” depends on each. Further, it can be seen that, regardless of the order of the filter, it also depends on the loop bandwidth “B _PLL ” of the carrier phase tracking loop filter unit 254.

  The loop bandwidth setting unit 273 of the processing unit 27 sets the loop bandwidth of the carrier phase tracking loop filter unit 254 at a predetermined setting timing. The loop bandwidth is set by, for example, a periodic timing (for example, once a day), a timing at which the GPS satellite signal reception environment has changed, a temperature change of a certain level (for example, a temperature change of 5 ° C. or more) It is preferable to execute it at the timing of occurrence. In the case of a timing at which a temperature change above a certain level occurs, a temperature sensor is further provided.

The loop bandwidth setting unit 273 measures and acquires the signal intensity “S” of the GPS satellite signal captured by the satellite signal capturing unit 23 at the loop bandwidth setting timing of the carrier phase tracking loop filter unit 254. The correlation integration time “T” is acquired from the correlation integration time determination unit 271. Then, using the acquired signal intensity “S” and correlation integration time “T”, the loop bandwidth characteristic “σ _tPLL (B _PLL )” of the thermal noise is obtained according to the equation (2). The loop bandwidth characteristic is a characteristic indicating how the fluctuation of the carrier phase changes due to the change of the loop bandwidth.

On the other hand, the loop bandwidth setting unit 273 detects a sensor detected value of a physical quantity (hereinafter referred to as “dynamic quantity for dynamic stress calculation”) used for calculating dynamic stress at the setting timing, and calculates the dynamic stress. The maximum detection error (hereinafter referred to as “assumed maximum detection error”) that can be included in the sensor detection value of the physical quantity for use is acquired from the host CPU 30. Then, using these values, the dynamic stress loop bandwidth characteristic “θ _en (B _PLL )” is obtained.

FIG. 3 is a diagram illustrating a correspondence relationship between the order of the loop filter unit and the physical quantity for dynamic stress calculation. If the order of the loop filter section is “first order”, the loop bandwidth characteristic “θ _e1 ” of the dynamic stress is calculated according to Equation (3) using the speed (speed calculated from the sensor output) and the assumed maximum speed error with respect to the line-of-sight direction. (B _PLL ) ”. If the order of the loop filter part is “second order”, the loop bandwidth characteristic “θ _e2 ” of the dynamic stress according to the equation (4) using the acceleration with respect to the line of sight (acceleration calculated from the sensor output) and the assumed maximum acceleration error. (B _PLL ) ”. If the order of the loop filter section is “third order”, the dynamic stress loop band according to equation (5) using the jerk with respect to the line-of-sight direction (the jerk calculated from the sensor output) and the assumed maximum jerk error. The width characteristic “θ _e3 (B _PLL )” is obtained.

More specifically, in each of the formulas (3) to (5), “the gaze direction component of the speed sensor detection value + the gaze direction component of the assumed maximum speed error” is “dR / dt”, and “acceleration sensor The line-of-sight direction component of the detected value + the line-of-sight direction component of the assumed maximum acceleration error is “dR ² / dt ² ”, and the line-of-sight direction component of the jerk sensor detection value + the line-of-sight direction component of the assumed maximum jerk error is “ As the dR ³ / dt ³ ”, the loop bandwidth characteristic“ θ _en (B _PLL ) ”of the dynamic stress is obtained.

One of the major features of the present embodiment is that, in the equations (3) to (5), the loop bandwidth characteristic “θ of dynamic stress is simply calculated using the sensor detection values of the speed, acceleration, and jerk of the GPS receiver. _en (B _PLL ) ", instead of taking into account the assumed maximum detection errors of sensor detection values of speed, acceleration and jerk, the loop bandwidth characteristics of dynamic stress" θ _en (B _PLL ) " It is in the point which decided to ask.

  According to the equations (3) to (5), the true bandwidth of the dynamic stress should be obtained using the true value of the physical quantity for dynamic stress calculation, but the true value is unknown. Therefore, conventionally, a loop bandwidth characteristic of dynamic stress is obtained using a sensor detection value of a physical quantity for dynamic stress calculation. The present embodiment is characterized in that the loop bandwidth characteristic of dynamic stress is obtained in consideration of the maximum detection error that can be included in the sensor detection value.

Once the thermal noise loop bandwidth characteristic “σ _tPLL (B _PLL )” and the dynamic stress loop bandwidth characteristic “θ _en (B _PLL )” are obtained, the total jitter loop bandwidth according to Equation (1) The characteristic “σ _PLL (B _PLL )” can be obtained. Then, the loop bandwidth “B _PLL ” is optimized based on the loop bandwidth characteristic “σ _PLL (B _PLL )” thus obtained.

The inventor of the present application conducted an experiment to examine the loop bandwidth characteristics of thermal noise, dynamic stress, and total jitter. Specifically, the thermal noise “σ _tPLL ”, the dynamic stress “θ _en ”, and the total jitter “σ _PLL ” are changed to the loop bandwidth “B” while changing the reception environment of the GPS satellite signal and the movement state of the GPS receiver. It was examined how it changes according to the size of the _PLL .

FIG. 4 is a diagram illustrating an example of the experimental result. The order of the carrier phase tracking loop filter unit 254 is “second order”, the signal strength of the received signal is 23 [dB-Hz], the assumed maximum acceleration error is ± 0.1 [m / s ² ], and the correlation integration time is 20 The experiment was conducted as [ms]. In FIG. 4, the horizontal axis represents the carrier phase tracking loop bandwidth “B _PLL ”, and the vertical axis represents the thermal noise “σ _tPLL ”, the dynamic stress “θ _e2 ”, and the total jitter “σ _PLL ”. Thermal noise “σ _tPLL ” is indicated by a dotted line, dynamic stress “θ _e2 ” is indicated by a one-dot chain line, and total jitter “σ _PLL ” is indicated by a solid line.

Looking at this figure, the thermal noise “σ _tPLL ” tends to increase as the carrier phase tracking loop bandwidth “B _PLL ” increases. On the other hand, the dynamic stress “θ _e2 ” tends to decrease as the carrier phase tracking loop bandwidth “B _PLL ” increases. The total jitter “σ _PLL ” obtained by adding these values becomes the minimum in a certain loop bandwidth “B _PLL ”, and tends to increase as the distance from the loop bandwidth “B _PLL ” increases.

Since the total jitter “σ _PLL ” represents the magnitude of the carrier phase fluctuation in the code phase tracking loop circuit, the total jitter “σ _PLL ” should be smaller. Therefore, in this embodiment, the loop bandwidth “B _PLL ” is optimized so as to minimize the total jitter “σ _PLL ”.

From equation (1), the total jitter “σ _PLL ” is mainly expressed as the sum of the thermal noise “σ _tPLL ” and the dynamic stress “θ _en ”, but the carrier phase tracking is appropriate in the carrier phase tracking loop circuit. Therefore, the total jitter “σ _PLL ” needs to be set to a predetermined threshold value (for example, 15 [deg]) or less.

As described above, the loop bandwidth characteristic of the dynamic stress “θ _en ” is obtained in consideration of the assumed maximum detection errors of speed, acceleration, and jerk according to the order of the loop filter. The assumed maximum detection error is the maximum detection error of the physical quantity for dynamic stress calculation assumed in a certain period. It is expected that the detection error of the physical quantity for dynamic stress calculation actually detected during the period is smaller than the assumed maximum detection error. Even so, instead of using the actual detection error, we decided to obtain the loop bandwidth characteristics of the dynamic stress using the assumed maximum detection error. This is to provide a margin so that the noise “σ _tPLL ” may increase to some extent.

More specifically, when the carrier phase tracking loop bandwidth “B _PLL ” is fixed, the dynamic stress “θ _en ” obtained using the assumed maximum detection error is the dynamic stress obtained using the actual detection error. It becomes larger than the stress “θ _en ”. In FIG. 4, the dynamic stress obtained using the assumed maximum detection error is indicated by a one-dot chain line. However, since the actual detection error is expected to be smaller than the assumed maximum detection error, the one-dot chain line indicating the dynamic stress. Is expected to shift to the left.

  As described above, there is no problem if the total jitter is equal to or less than a predetermined threshold. Therefore, the smaller dynamic stress means that larger thermal noise is allowed for the same loop bandwidth. That is, in FIG. 4, when the alternate long and short dash line indicating dynamic stress shifts to the left, the dotted line indicating thermal noise is allowed to shift upward.

  According to the equation (2), the smaller the signal strength of the received signal (the weaker the signal), the greater the thermal noise. Therefore, in FIG. 4, the fact that the dotted line of thermal noise is allowed to shift upward means that the signal strength of the received signal is allowed to be small for the same loop bandwidth. To do.

  In this way, by optimizing the loop bandwidth using the assumed maximum detection error and providing a certain margin for the increase in thermal noise, the reception environment is a weak electric field environment such as an indoor environment while tracking GPS satellite signals. Even in such a case, the occurrence of unlocking is less likely to occur, and the continuity of tracking can be improved.

As described above, it is known that tracking of the carrier phase is appropriately performed if the total jitter “σ _PLL ” is equal to or less than a predetermined threshold (for example, 15 [deg]). Therefore, the loop bandwidth is not limited to setting the "B _PLL" total jitter "sigma _PLL" threshold below a predetermined value so as to minimize the total jitter "sigma _PLL" as in this embodiment (e.g., The loop bandwidth “B _PLL ” may be set to be a value slightly larger than the minimum value.

(2) Setting of the loop bandwidth of the carrier frequency tracking loop filter unit When tracking the carrier frequency in the carrier frequency tracking loop, there is an error that can be included in the carrier frequency to be tracked. The main factors of this carrier frequency error are still thermal noise and dynamic stress.

In order to explain specifically, the carrier frequency fluctuation in the carrier frequency tracking loop circuit is formulated. Here, the carrier frequency fluctuation is formulated in terms of frequency (Hz). The thermal noise “σ _tFLL ” in the carrier frequency tracking loop is given by the following equation (6).

In Expression (6), “B _FLL ” is the loop bandwidth of the carrier frequency tracking loop filter unit 256, and “F” is a constant. From the equation (6), the thermal noise “σ _tFLL ” in the carrier frequency tracking loop is also the loop bandwidth “B _FLL ” of the carrier frequency tracking loop filter unit 256, the signal strength “S” of the received signal, and the correlation integration time “ It turns out that it depends on "T".

但し、「λ」は定数であり、「Ｒ」は擬似距離である。 Further, the dynamic stress “f _e ” in the carrier frequency tracking loop is formulated by a different formula depending on the order of the carrier frequency tracking loop filter unit 256. Specifically, the dynamic stress “f _en ” for the nth-order carrier frequency tracking loop filter unit 256 is given by the following equation (7).

However, “λ” is a constant, and “R” is a pseudorange.

The total jitter “σ _FLL ” in the carrier frequency tracking loop is given by the following equation (8).

The setting of the loop bandwidth of the carrier frequency tracking loop filter unit 256 can also be considered in the same manner as in the case of the carrier phase tracking loop filter unit 254. That is, the loop bandwidth characteristic “σ _tFLL (B _FLL )” of the thermal noise obtained from Expression (6) and the loop bandwidth characteristic “f _en (B _FLL )” of the dynamic stress obtained from Expression (7) Using this, the loop bandwidth characteristic “σ _FLL (B _FLL )” of the total jitter is obtained according to the equation (8). Then, the loop bandwidth “B _FLL ” of the carrier frequency tracking loop filter unit 256 is optimized so that the total jitter “σ _FLL ” is minimized.

(3) Setting the loop bandwidth of the code tracking loop filter unit When tracking the code phase in the code tracking loop circuit, there is an error that can be included in the code phase to be tracked. The main causes of this code phase error are still thermal noise and dynamic stress.

For concrete explanation, the code phase fluctuation in the code tracking loop circuit is formulated. Here, the code phase fluctuation is formulated by converting the CA code into chips (chips). The thermal noise “σ _tDLL ” in the code tracking loop circuit is given by the following equation (9).

In Expression (9), “B _DLL ” is a code tracking loop bandwidth, and “F ₁ ” and “F ₂ ” are correlation coefficients. “D” is the phase difference (spacing) of the Early code, Prompt code, and Late code. From equation (9), the thermal noise “σ _tDLL ” in the code tracking loop also _{depends on} the code tracking loop bandwidth “B _DLL ”, the received signal strength “S”, and the correlation integration time “T”. I understand.

但し、「η」は定数であり、「Ｒ」は擬似距離である。 The dynamic stress “D _e ” in the code tracking loop circuit is formulated by a different formula depending on the order of the code tracking loop filter unit 252. Specifically, the dynamic stress “D _en ” for the n-th code tracking loop filter unit 252 is given by the following equation (10).

However, “η” is a constant and “R” is a pseudorange.

The total jitter “σ _DLL ” in the code tracking loop is given by the following equation (11).

The setting of the loop bandwidth of the code tracking loop filter unit 252 can be considered in the same manner as in the case of the carrier phase tracking loop filter unit 254. That is, the loop bandwidth characteristic “σ _tDLL (B _DLL )” of thermal noise obtained from Expression (9) and the loop bandwidth characteristic “D _en (B _DLL ) of dynamic stress obtained from Expression (10) are obtained. Then, the loop bandwidth characteristic “σ _DLL (B _DLL )” of the total jitter is obtained according to the equation (11). Then, the loop bandwidth “B _DLL ” of the code tracking loop filter unit 252 is optimized so that the total jitter “σ _DLL ” is minimized.

3. Data Configuration (1) Data Configuration of Storage Unit 90 As shown in FIG. 1, the main program 911 read out by the host CPU 30 and executed as main processing (see FIG. 5) is stored in the storage unit 90 of the mobile phone 1. Sensor data 921, calibration time 922, calibration detection error 923, dynamic stress calculation physical quantity 925, and assumed maximum detection error 927 are stored. Further, the main program 911 includes a calibration program 912 executed as a calibration process as a subroutine.

  In the main process, the host CPU 30 performs a process for realizing a call function, a mail transmission / reception function, an Internet function, and the like, which are essential functions of the mobile phone 1. Further, the calibration processing of the IMU 60 is performed, the assumed maximum detection error 927 is calculated based on the elapsed time since the calibration processing is performed, and is output to the baseband processing circuit unit 20 together with the physical quantity 925 for dynamic stress calculation. . The main process will be described later in detail using a flowchart.

  In the calibration process, the host CPU 30 calculates error parameter values such as bias and scale factor of the acceleration sensor 61 and the gyro sensor 63 constituting the IMU 60, and outputs sensor outputs from the acceleration sensor 61 and the gyro sensor 63. In this process, the IMU 60 is calibrated by performing a correction process using the calculated error parameter value.

  The sensor data 921 is data in which acceleration and angular velocity respectively detected by the acceleration sensor 61 and the gyro sensor 63 constituting the IMU 60 are stored in time series, and is updated whenever a detection result is output from the IMU 60.

  The calibration time 922 is the time when the calibration processing of the IMU 60 was last executed by the host CPU 30. A calibration detection error 923 is a detection error of a physical quantity for dynamic stress calculation at the calibration time 922.

  The physical quantity 925 for dynamic stress calculation is a physical quantity used for calculating dynamic stress. As described with reference to FIG. 3, when the order of the loop filter unit included in the satellite signal tracking unit 25 is “first order”, “speed” is “order”, and when “second order”, “acceleration” is “3”. In the case of “next”, “jump” is a physical quantity for dynamic stress calculation.

  The assumed maximum detection error 927 is a detection error of a physical quantity for dynamic stress calculation calculated based on the elapsed time from the calibration time 922, and is the assumed maximum detection error.

(2) Data Configuration of Storage Unit 29 As shown in FIG. 2, the storage unit 29 of the baseband processing circuit unit 20 is read by the processing unit 27 and executed as baseband processing (see FIG. 6). A band processing program 291, satellite orbit data 293, a physical quantity for dynamic stress calculation 295, and an assumed maximum detection error 297 are stored.

  The baseband processing program 291 includes a code tracking loop bandwidth setting program 2911 executed as a loop bandwidth setting process of the code tracking loop filter, and a loop bandwidth setting process of the carrier phase tracking loop filter (see FIG. 7). The carrier phase tracking loop bandwidth setting program 2913 and the carrier frequency tracking loop bandwidth setting program 2915 executed as the loop bandwidth setting processing of the carrier frequency tracking loop filter are included as subroutines.

  The satellite orbit data 293 is data such as an almanac storing approximate satellite orbit information of all GPS satellites, and an ephemeris storing detailed satellite orbit information for each GPS satellite. The satellite orbit data 293 is obtained by decoding a GPS satellite signal received from a GPS satellite, or obtained from a base station or an assist server of the mobile phone 1.

  The dynamic stress calculation physical quantity 295 and the assumed maximum detection error 297 are the same data as the dynamic stress calculation physical quantity 925 and the assumed maximum detection error 927 stored in the storage unit 90.

4). Flow of Processing (1) Processing of Host CPU 30 FIG. 5 shows main processing executed in the mobile phone 1 by reading and executing the main program 911 stored in the storage unit 90 by the host CPU 30. It is a flowchart which shows a flow.

  First, the host CPU 30 determines an instruction operation performed by the user via the operation unit 40 (step A1), and determines that the instruction operation is a call instruction operation (step A1; call instruction operation), Processing is performed (step A3). Specifically, the mobile phone wireless communication circuit unit 80 performs base station communication with the base station, thereby realizing a call between the mobile phone 1 and another device.

  If it is determined in step A1 that the instruction operation is a mail transmission / reception instruction operation (step A1; mail transmission / reception instruction operation), the host CPU 30 performs a mail transmission / reception process (step A5). Specifically, base station communication is performed by the mobile phone wireless communication circuit unit 80, and mail transmission / reception between the mobile phone 1 and another device is realized.

  When it is determined in step A1 that the instruction operation is a position / speed calculation instruction operation (step A1; position / speed calculation instruction operation), the host CPU 30 stores the physical quantity for dynamic stress calculation stored in the storage unit 90. 925 and the assumed maximum detection error 927 are output to the processing unit 27 of the baseband processing circuit unit 20 (step A7).

  Then, the host CPU 30 performs a position / speed calculation control process that causes the processing unit 27 to execute position / speed calculation calculation (step A9). Then, the host CPU 30 acquires the calculated position and speed from the processing unit 27, and outputs and displays the acquired position and speed on the display unit 50 (step A11).

  After the processes of steps A3 to A11, the host CPU 30 determines whether or not it is the execution timing of the calibration process (step A13). Arbitrary timing can be set as the calibration execution timing.

  For example, the elapsed time from the power-on of the mobile phone 1 or the elapsed time since the last execution of the calibration process may be a timing at which a predetermined time (for example, 1 hour) has been reached. It is good also as timing when the temperature change more than predetermined temperature (for example, 5 degreeC) was detected from the temperature at the time of power-on, or the temperature when calibration processing was performed last time. In the latter case, a temperature sensor is further provided. Further, it may be the timing when the user performs an instruction to execute the calibration process.

  If it is determined that it is not yet the execution timing (step A13; No), the host CPU 30 shifts the processing to step A17. When it is determined that it is the execution timing (step A13; Yes), the calibration process is performed by reading and executing the calibration program 912 in the storage unit 90 (step A15).

  The calibration process is performed by obtaining values of error parameters such as bias and scale factor of each sensor of the IMU 60 according to a known method, for example. The bias means an error value that is constantly added, and the scale factor means the sensitivity of the sensor, that is, the ratio of the change in the output value to the change in the input value to be measured.

  Next, the host CPU 30 calculates a dynamic stress calculating physical quantity 925 based on the sensor data 921 stored in the storage unit 90, and updates the storage unit 90 (step A17). Then, the assumed maximum detection error 927 is calculated based on the calibration time 922 and the calibration detection error 923 stored in the storage unit 90, and the storage unit 90 is updated (step A19).

Specifically, when the detection error 923 at the time of calibration is “E _C ”, “E _MAX ” that is the assumed maximum detection error 927 is calculated according to the following equation (12), for example.

In Equation (12), “k” is a coefficient having a positive correlation with the elapsed time “Δt” from the calibration time. That is, as the elapsed time “Δt” increases, the coefficient “k” increases, and the calculated assumed maximum detection error “E _MAX ” also increases. Expression (12) is an example of an arithmetic expression for an assumed maximum detection error, and the assumed maximum detection error may be calculated using another arithmetic expression. It is only necessary to determine an arithmetic expression such that the assumed maximum detection error “E _MAX ” increases as the elapsed time “Δt” from the calibration time increases.

  Next, the host CPU 30 determines whether or not a power-off instruction operation has been performed by the user via the operation unit 40 (step A21). On the other hand, if it is determined that it has been made (step A21; Yes), the main process is terminated.

(2) Processing of Processing Unit 27 FIG. 6 is executed by the baseband processing circuit unit 20 by the baseband processing program 291 stored in the storage unit 29 being read and executed by the processing unit 27. It is a flowchart which shows the flow of a baseband process.

  First, the processing unit 27 performs a capture target satellite determination process (step B1). Specifically, a GPS satellite located in the sky at a given reference position at the current time measured by a clock unit (not shown) is determined using the satellite orbit data 293 in the storage unit 29, and is captured. Satellite. For example, in the case of the first position calculation after power-on, the reference position is a position acquired from the assist server by so-called server assist, and in the second and subsequent position calculation, the reference position is the latest calculated position. Can be set.

  Next, the processing unit 27 performs the process of loop A for each capture target satellite determined in step B1 (steps B3 to B27). In the process of loop A, the processing unit 27 measures the signal strength of the GPS satellite signal received from the capture target satellite (step B5). Then, the correlation integration time determination unit 271 determines the correlation integration time when the correlation processing unit 231 performs the correlation integration process on the GPS satellite signal received from the capture target satellite (step B7).

  The determination of the correlation integration time can be realized by various methods. For example, it may be determined based on the signal strength of the GPS satellite signal measured in step B5. The weaker the signal strength, the more difficult it is to detect the correlation value peak unless the correlation values are integrated over a long period of time. For this reason, it is preferable to increase the correlation integration time as the signal intensity decreases. For example, when the signal strength satisfies a predetermined low signal strength condition (for example, signal strength ≦ low signal strength threshold), the correlation integration time is set to “20 milliseconds”, and when the low signal strength condition is not satisfied, the correlation For example, the accumulated time may be “10 milliseconds”.

  Further, the reception environment of the GPS satellite signal may be determined, and the correlation integration time may be determined based on the determined reception environment. For example, when the reception environment is “indoor environment (indoor environment)”, the correlation integration time is “20 milliseconds”. When the reception environment is “outdoor environment (outdoor environment)”, the correlation integration time is “10 milliseconds”. And so on.

  Thereafter, the processing unit 27 determines whether or not the satellite signal tracking unit 25 is tracking the GPS satellite signal from the capture target satellite (step B9), and when determining that the tracking is being performed (step B9) ; Yes), the process proceeds to step B13. If it is determined that tracking is not in progress (step B9; No), the processing unit 27 performs satellite signal acquisition processing, and causes the satellite signal acquisition unit 23 to acquire a GPS satellite signal from the acquisition target satellite (step S9). B11).

  Next, the processing unit 27 determines whether or not the loop bandwidth setting execution condition is satisfied (step B13). Migrate processing. If it is determined that the loop bandwidth setting execution condition is satisfied (step B13; Yes), the processing unit 27 reads and executes the carrier phase tracking loop bandwidth setting program 2913 stored in the storage unit 29. Thus, carrier phase tracking loop bandwidth setting processing is performed (step B15).

FIG. 7 is a flowchart showing the flow of the carrier phase tracking loop bandwidth setting process.
First, the loop bandwidth setting unit 273 calculates the line-of-sight direction component of the dynamic stress calculation physical quantity 295 stored in the storage unit 29 (step C1). Further, the line-of-sight direction component of the assumed maximum detection error 297 stored in the storage unit 29 is calculated (step C3).

  The line-of-sight direction is a direction from the mobile phone 1 toward the capture target satellite. Therefore, for example, the line-of-sight direction can be obtained by using the latest calculated position of the mobile phone 1 and the latest satellite position of the capture target satellite calculated using the satellite orbit data 293. Then, the dynamic stress calculating physical quantity 295 and the assumed maximum detection error 297 may be projected in the obtained line-of-sight direction.

Next, the loop bandwidth setting unit 273 uses the signal intensity “S” of the capture target satellite measured in step B5 and the correlation integration time “T” of the capture target satellite determined in step B7 to obtain an equation ( According to 2), the loop bandwidth characteristic “σ _tPLL (B _PLL )” of the thermal noise is obtained (step C5).

In addition, the loop bandwidth setting unit 273 uses the gaze direction component of the dynamic stress calculation physical quantity 295 calculated in step C1 and the gaze direction component of the assumed maximum detection error 297 calculated in step C3 to obtain equation (3). The loop bandwidth characteristic “θ _en (B _PLL )” of the dynamic stress is obtained according to (5) (step C7).

The loop bandwidth setting unit 273 then sets the thermal noise loop bandwidth characteristic “σ _tPLL (B _PLL )” obtained in step C5 and the dynamic stress loop bandwidth characteristic “θ _en (B _PLL ) obtained in step C7. ) ”Is used to determine the loop bandwidth characteristic“ σ _PLL (B _PLL ) ”of the total jitter according to the equation (1) (step C9).

Next, the loop bandwidth setting unit 273 determines the carrier phase tracking loop bandwidth “B _PLL ” based on the loop bandwidth characteristic “σ _PLL (B _PLL )” of the total jitter obtained in Step C9 (Step C11). ). That is, the carrier phase tracking loop bandwidth “B _PLL ” is optimized so that the total jitter “σ _PLL ” is minimized.

Then, the loop bandwidth setting unit 273 outputs the determined carrier phase tracking loop bandwidth “B _PLL ” to the carrier phase tracking loop filter unit 254 (step C13), and ends the carrier phase tracking loop bandwidth setting process. .

  Returning to the baseband processing of FIG. 6, after performing the carrier phase tracking loop bandwidth setting processing, the processing unit 27 reads and executes the carrier frequency tracking loop bandwidth setting program 2915 stored in the storage unit 29. Thus, the carrier frequency tracking loop bandwidth setting process is performed (step B17). The processing unit 27 reads out and executes the code tracking loop bandwidth setting program 2911 stored in the storage unit 29, thereby performing code tracking loop bandwidth setting processing (step B19).

  The setting of the carrier frequency tracking loop bandwidth and the setting of the code tracking loop bandwidth can be performed in the same manner as the setting of the carrier phase tracking loop bandwidth as described in the principle. Therefore, the flow chart of the carrier frequency tracking loop bandwidth setting process and the code tracking loop bandwidth setting process is not shown and described.

  After setting the loop bandwidth of the various loop filter units, the Doppler calculation unit 275 calculates the Doppler frequency of the GPS satellite signal received from the capture target satellite (step B23). The Doppler frequency is calculated using the speed of the mobile phone 1 calculated by integrating the acceleration detected by the acceleration sensor 61 and the satellite speed of the capture target satellite calculated using the satellite orbit data 293. can do.

  Then, the Doppler calculation unit 275 outputs the calculated Doppler frequency to the carrier removal signal generation unit 213 (step B25), and shifts the processing to the next acquisition target satellite. After performing the processing of Steps B5 to B25 for all the acquisition target satellites, the processing unit 27 ends the processing of Loop A (Step B27).

  Thereafter, the position / velocity calculation unit 277 executes position / velocity calculation calculation using the GPS satellite signals captured for each capture target satellite (step B29). The position calculation calculation can be realized by performing a known convergence calculation using, for example, a least square method or a Kalman filter using a pseudo distance between the mobile phone 1 and each capture target satellite. Further, the speed calculation calculation can be realized based on a known method using, for example, a time change of the reception frequency of the GPS satellite signal received from each capture target satellite.

  Next, the processing unit 27 outputs the calculated position and speed to the host CPU 30 (step B31). Then, the processing unit 27 determines whether or not to end the processing (step B33). If it is determined that the processing has not ended yet (step B33; No), the processing unit 27 returns to step B1. If it is determined that the process is to be terminated (step B33; Yes), the baseband process is terminated.

5. Operational Effect In the mobile phone 1, the movement status is detected by the IMU 60. Further, the host CPU 30 calculates an assumed maximum detection error that is the assumed maximum detection error of the IMU 60. The loop of the loop filter unit of the tracking loop circuit for tracking the GPS satellite signal received from the GPS satellite using the detection result of the IMU 60 and the assumed maximum detection error by the processing unit 27 of the baseband processing circuit unit 20 Bandwidth is set.

  The jitter of the code phase, the carrier phase, and the carrier frequency in the loop circuit for tracking the GPS satellite signal can vary greatly depending on the movement state of the mobile phone 1. Therefore, it is appropriate to set the loop bandwidth of each tracking loop filter unit using the detection result of the IMU 60. However, the detection result of the IMU 60 can naturally include an error. Therefore, the loop bandwidth can be set to an appropriate value by setting the loop bandwidth in consideration of the detection error of the IMU 60 in addition to the detection result of the IMU 60.

  In particular, in the present embodiment, the maximum expected detection error that can be included in the physical quantity for dynamic stress calculation is calculated according to the order of the loop filter unit, and the loop band of the dynamic stress is calculated in consideration of the assumed maximum detection error. The width characteristic was determined. Thereby, it becomes possible to give a certain margin to the increase in thermal noise. This makes it difficult to cause a lock release even in a weak electric field environment such as an indoor environment, and enables continuous tracking of GPS satellite signals.

6). Modification 6-1. Electronic Device In the above-described embodiments, the case where the present invention is applied to a mobile phone which is a kind of electronic device has been described as an example. However, an electronic device to which the present invention can be applied is not limited thereto. For example, the present invention can be similarly applied to other electronic devices such as a car navigation device, a portable navigation device, a personal computer, a PDA (Personal Digital Assistant), and a wristwatch.

6-2. In the above-described embodiment, the GPS has been described as an example of the position calculation system. However, WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), GALILEO It may be a position calculation system using other satellite positioning systems.

6-3. In the embodiment described above, the movement state of the mobile phone 1 is detected using the acceleration detected by the acceleration sensor 61 of the IMU 60, but the angular velocity detected by the gyro sensor 63 of the IMU 60 is used. It may be used to detect the movement situation. Further, in place of or in addition to the IMU 60, a speed sensor for detecting the speed of the mobile phone 1 is provided, and the moving state is detected using the moving speed detected by the speed sensor. Also good.

6-4. Setting of loop bandwidth using GPS satellite signal reception environment In the embodiment described above, the signal strength of the GPS satellite signal is measured, and the loop bandwidth characteristic of the thermal noise is obtained by using the measured signal strength. It has been described that the bandwidth is set to a value suitable for the measured signal strength. However, since the signal strength of the GPS satellite signal is closely related to the reception environment, the loop bandwidth characteristics of the thermal noise may be obtained using the reception environment such as the indoor environment or the outdoor environment.

  For example, as shown in FIG. 8, a table in which the GPS satellite signal reception environment is associated with the signal strength of the GPS satellite signal reception signal is stored in the storage unit 29. In the table of FIG. 8, reception environments represented by A, B, C, D,... Represent GPS satellite signal reception environments such as an indoor environment, an outdoor environment, an urban canyon environment, and a multipath environment. Further, the signal strengths Sa, Sb, Sc, Sd,... Of GPS satellite signals are stored in association with the reception environments A, B, C, D,.

  The processing unit 27 determines the reception environment of the GPS satellite signal from the capture target satellite, and reads the signal intensity associated with the determined reception environment. Then, using the read signal strength, the loop bandwidth characteristic of the thermal noise is obtained according to Equation (2). Then, using the obtained loop bandwidth characteristic of thermal noise and the loop bandwidth characteristic of dynamic stress, the loop bandwidth is set to a value suitable for the determined reception environment.

  In addition, PDOP (Position Dilution of Precision) values, which are index values representing the geometrical sky arrangement of GPS satellites, and information such as the elevation angle of GPS satellites are closely related to the reception environment. It is also possible to set the loop bandwidth. Since the reception environment is better as the PDOP value is smaller and the reception environment is better as the elevation angle is higher, the loop bandwidth characteristics of thermal noise may be obtained using this relationship in the same manner as described above.

6-5. Setting of Loop Bandwidth In the embodiment described above, the loop bandwidth of each loop filter unit has been described as being set so as to minimize the total jitter in each loop circuit. However, as described in the principle, the total jitter may be set to be equal to or less than a predetermined threshold value instead of setting the total jitter to be minimum.

DESCRIPTION OF SYMBOLS 1 Portable telephone, 10 GPS receiving part, 11 RF receiving circuit part, 20 Baseband processing circuit part, 30 Host CPU, 40 Operation part, 50 Display part, 60 IMU, 61 Acceleration sensor, 63 Gyro sensor, 70 For mobile phones Antenna, 80 wireless communication circuit unit for mobile phone, 90 storage unit

Claims (7)

Detecting movement status,
Calculating an error of the detection;
Using the detection result and the error, setting the loop bandwidth of the tracking filter that is used for tracking the satellite signal received from the positioning satellite and in which the loop bandwidth can be changed;
Including satellite signal tracking method. Detecting the movement state includes performing a calibration process on an output of any one of the sensors at a given timing using at least one of an acceleration sensor, a speed sensor, and a gyro sensor,
Calculating the error includes calculating the error using an elapsed time since the execution of the calibration process;
The satellite signal tracking method according to claim 1. Setting the loop bandwidth includes setting the loop bandwidth using a reception environment of the satellite signal.
The satellite signal tracking method according to claim 1 or 2. Setting the loop bandwidth includes setting the loop bandwidth using a filter order of the tracking filter.
The satellite signal tracking method according to any one of claims 1 to 3. Performing the satellite signal tracking method according to any one of claims 1 to 4 to track the satellite signal;
Calculating a position using the tracked satellite signal;
Position calculation method including A detection unit for detecting the movement status;
Using the detection result of the detection unit and the detection error of the detection unit, the loop bandwidth of the tracking filter that can be used to track the satellite signal received from the positioning satellite and that can change the loop bandwidth is set. A setting section to
Satellite signal tracking device with At least one of an acceleration sensor, a speed sensor, and a gyro sensor;
A movement situation detector that detects a movement situation using an output of the at least one sensor;
A tracking filter that is used for tracking satellite signals from positioning satellites and that can change the loop bandwidth;
A setting unit that sets the loop bandwidth of the tracking filter using the detection result of the movement state detection unit and the detection error of the movement state detection unit;
A position calculation unit that calculates a position using a satellite signal tracked by the tracking filter;
A position calculation device comprising:

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