JP2010197189A - Time determination method and time determination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method determining time even in a weal electric field environment or the like. <P>SOLUTION: A cellular phone receives a GPS satellite signal which is a conveyance wave signal from a GPS satellite, and demodulate and acquires a data bit pattern from the received signal. The acquired reception data bit pattern is collated successively in each bit unit with a collation bit pattern generated by using a stored ephemeris, and suitability between the reception data bit pattern and the collation bit pattern is determined based on an accumulated continuous bit length acquired by adding a bit length determined to be continuously consistent by collation to a bit length determined to be continuously inconsistent. When determined to be suitable by suitability determination, a time is determined by using, for example, a reception timing of a telemetry word (TLM) specified as a communication format for navigation data. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a time determination method and a time determination 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 is performed to obtain a three-dimensional coordinate value indicating the position of the own device and a clock error based on information such as the positions of a plurality of GPS satellites and pseudo distances from each GPS satellite to the own device.

  In GPS, since time is essential information for performing position calculation, a technique for acquiring time information is required. Patent Document 1 discloses a technique for determining a time by performing pattern matching between a bit pattern of navigation data acquired and stored in advance and a bit pattern of received data.

JP 2000-332739 A

  In the technique of Patent Document 1, a received positioning signal is demodulated to obtain a data bit pattern, and collation is performed with a collation bit pattern obtained and stored in advance. However, in an environment where the received positioning signal is a weak electric field signal (so-called weak electric field environment), such as when the device is indoors, an error occurs when demodulating the positioning signal, and the data bit pattern May be inverted. That is, since the positioning signal is modulated by the phase inversion method, if a demodulation error occurs once, all the signs of the subsequent data bits are interpreted in reverse.

  In the technique disclosed in Patent Document 1, the suitability between the received data bit pattern and the verification bit pattern is determined based on the bit length in which the bit values are continuously matched. Therefore, when the technique of Patent Document 1 is applied as it is, if an error occurs once when demodulating a positioning signal received in a weak electric field environment, all subsequent codes are interpreted in reverse and demodulated. Therefore, there is a problem that the time cannot be determined using bit pattern matching.

  The present invention has been made in view of the above-described problems, and an object thereof is to propose a new method capable of determining the time even in a weak electric field environment or the like.

  In a first mode for solving the above-described problems, the carrier signal is transmitted from a positioning satellite that periodically transmits a carrier signal that carries predetermined navigation data in a predetermined communication format by modulating the phase inversion method. Receiving, demodulating and obtaining a data bit pattern from the received signal, sequentially collating the data bit pattern and a predetermined collation bit pattern bit by bit, Determining the suitability of the data bit pattern and the verification bit pattern based on the identification cumulative length obtained by adding together the bit length determined to be continuously matched and the bit length determined to be continuously mismatched; When it is determined to be suitable by the suitability determination, the time is determined using a predetermined reception timing defined in the communication format. Doo Doo, a time determination method, including.

  Further, as another form, a receiving unit that receives the carrier signal from a positioning satellite that periodically transmits a carrier signal that carries predetermined navigation data in a predetermined communication format by modulating the phase inversion method, A demodulator that demodulates and acquires a data bit pattern from a received signal, a collator that sequentially collates the data bit pattern with a predetermined bit pattern for collation in units of bits, and continuously matches by the collation An appropriateness determination unit for determining the appropriateness of the data bit pattern and the verification bit pattern based on the identification accumulated length obtained by adding the bit length determined to be consecutively determined and the bit length determined to be inconsistent; Time determination that determines the time using the predetermined reception timing defined in the communication format when it is determined to be appropriate by the suitability determination. And parts, may constitute a time determination device equipped with.

  According to the first embodiment, a carrier wave signal is received from a positioning satellite, and a data bit pattern is demodulated and acquired from the received signal. Then, the obtained data bit pattern and a predetermined bit pattern for verification are sequentially verified in bit units, and the bit length determined to be continuously matched by the verification and the bit length determined to be continuously mismatched Whether or not the acquired data bit pattern and the verification bit pattern are appropriate is determined based on the accumulated cumulative length obtained by adding together. Then, when it is determined to be suitable by the suitability determination, the time is determined using a predetermined reception timing of the communication format of the navigation data.

  Appropriateness of the data bit pattern obtained by demodulating the carrier wave signal and the verification bit pattern includes not only the bit length determined to be consistently matched but also the bit length determined to be continuously mismatched. I decided to judge. As a result, even when an error occurs when demodulating a carrier wave signal in a weak electric field environment or the like, it is possible to correctly determine the suitability of the bit pattern even when the subsequent bit code is interpreted in reverse. The time can be determined according to the data communication format.

  Further, as a second mode, in the time determination method according to the first mode, an effective period is determined for the navigation data, and the positioning satellite transmits a carrier signal carrying the navigation data of the latest effective period. Out of the bit patterns representing the acquired past navigation data, extracting a reusable bit portion having the same bit value as the bit pattern representing the latest navigation data, and reusing the reusable bit portion. And generating the collation bit pattern using the collation, wherein the collation sequentially collates the data bit pattern and the collation bit pattern bit by bit with respect to the divertable bit portion. A time determination method may be configured.

  According to the second mode, a divertable bit portion having the same bit value as the bit pattern representing the latest navigation data is extracted from the bit patterns representing the acquired past navigation data. Then, a verification bit pattern is generated using the extracted reusable bit part, and the data bit pattern obtained by demodulating the reusable bit part and the verification bit pattern are sequentially verified in bit units. .

  By using the divertable bit portion having the same bit value as the bit pattern representing the latest navigation data, a matching bit pattern suitable for matching can be generated.

  Further, as a third mode, the time determination method according to the second mode, wherein the navigation data includes a parameter whose value gradually changes with time, and the extraction includes You may comprise the time determination method including extracting the bit part of a predetermined | prescribed upper digit among the bit parts showing the value of a parameter as the said diversion possible bit part.

  According to the third embodiment, a bit portion of a predetermined upper digit is extracted as a divertable bit portion from bit portions representing parameter values whose values gradually change with time. A parameter whose value gradually changes over time is not used for collation because the value of the lower-order bit part is likely to change, and the upper-order bit whose value is unlikely to change Use part for matching.

  Further, as a fourth mode, the time determination method according to any one of the first to third modes, the latest navigation data using past navigation data and a period during which the past navigation data was valid. A time determination method that further includes generating a part of or all of the bit pattern for verification and generating the verification bit pattern may be configured.

  According to the fourth embodiment, a part or all of the latest navigation data is estimated using the past navigation data and the period during which the past navigation data was valid, and a verification bit pattern is generated. The navigation data includes a parameter whose time is a variable and whose value changes depending on the time. Therefore, values for these parameters are estimated and a verification bit pattern is generated.

  Further, as a fifth mode, in the time determination method according to any one of the first to fourth modes, it is determined that the determination of the suitability is continuously matched by a predetermined continuous number or more by the collation. A time determination method may be configured which includes adding the bit length and the bit length determined to be inconsistent continuously over the continuous number to obtain the identified cumulative length.

  According to the fifth aspect, the identification cumulative length is obtained by adding together the bit length determined to be continuously matched by a predetermined continuous number or more by the collation and the bit length determined to be continuously mismatched by the continuous number or more. . Even when it is determined that they are continuously matched or when it is determined that they do not match continuously, if the bit length is less than a predetermined number of consecutive numbers, they are not added to the identified cumulative length. Therefore, in the case where errors frequently occur when demodulating a carrier wave signal and bit value inversion repeatedly occurs, it is determined as nonconforming.

Explanatory drawing of the principle of the bit pattern generation for collation. Explanatory drawing of the principle of collation. The block diagram which shows the function structure of a portable telephone. The figure which shows an example of the data stored in ROM of a baseband process circuit part. The figure which shows an example of the data stored in RAM of a baseband process circuit part. The figure which shows an example of the data structure of the data for collation mask formation. The flowchart which shows the flow of a time determination process. The flowchart which shows the flow of the bit pattern generation process for collation. The flowchart which shows the flow of collation processing.

  Hereinafter, with reference to the drawings, an embodiment in which the present invention is applied to a mobile phone 1 which is a kind of electronic apparatus including a time determination device and a position calculation device will be described. However, embodiments to which the present invention can be applied are not limited to the embodiments described below.

1. Principle In this embodiment, the mobile phone 1 acquires a received data bit pattern that is a bit pattern of navigation message data by demodulating a GPS satellite signal received from a GPS satellite. On the other hand, the navigation message data is estimated, and a verification bit pattern representing the estimated navigation message data is generated inside the mobile phone 1. The received data bit pattern is compared with the verification bit pattern. As a result of the collation, when it is determined to be compatible, the time is determined using a predetermined reception timing defined as the communication format of the navigation message data.

1-1. Principle of Collation Bit Pattern Generation FIG. 1 is a diagram illustrating a concept for explaining the principle of collation bit pattern generation in the present embodiment. The GPS satellite repeatedly transmits a carrier wave signal (GPS satellite signal) that carries navigation data (navigation message) by modulating the phase inversion method.

  Since the bit rate of the GPS satellite signal is 50 bits per second, each bit is 20 milliseconds long. One navigation data is composed of one master frame, and one master frame is composed of 25 1500-bit main frames. Therefore, it takes 30 seconds to receive one main frame, and 12.5 minutes to receive all navigation data (one master frame). The head of each main frame is always transmitted in synchronization with every minute or every 30 seconds after every minute.

  Each main frame is composed of five subframes (the first to fifth subframes in FIG. 1). The same information is repeated for each main frame in the first to third subframes, and different information is stored in each mainframe in the fourth and fifth subframes. Information stored in different pages of navigation data is stored in the fourth subframe and the fifth subframe.

  Each subframe is composed of 10 words. The first word is called a telemetry word (TLM) and is composed of an 8-bit synchronization pattern and a 14-bit message. The second word is called a handover word (HOW) and includes time information (number of seconds elapsed since the beginning of the week). The third word to the tenth word contain different information for each subframe.

  In this embodiment, paying attention to the ephemeris included in the third to tenth words of the second and third subframes, various parameters such as satellite orbit parameters and clock correction parameters in the ephemeris (hereinafter referred to as “ephemeris parameters”). To generate a verification bit pattern.

  The mobile phone 1 needs to acquire the ephemeris from the server of the base station by server assist in advance or acquire and store the ephemeris by demodulating the GPS satellite signal transmitted from the GPS satellite. It becomes. The effective period of the ephemeris is 4 hours, and the ephemeris can be used as it is within the effective period. However, if the effective period has expired, the ephemeris cannot be used as it is. Therefore, the verification bit pattern is generated by a different method depending on whether or not the stored ephemeris is within the valid period.

(1) When the effective period of the ephemeris has expired When the effective period of the ephemeris has expired, a collation mask that defines a bit portion for performing pattern matching with the received data bit pattern is determined. The ephemeris parameter is classified into two types, a time-dependent parameter which is a parameter whose value gradually changes with the passage of time and a time-independent parameter which is a parameter whose time is not a variable. The collation mask is composed of estimated values of time-dependent parameters and original values of time-independent parameters.

This will be described in detail. Among the ephemeris parameters, the three parameters of the ephemeris reference time “t _oe ”, the rising intersection red longitude “Ω ₀ ”, and the average near point separation angle “M ₀ ” are time-dependent parameters in the present embodiment. . When the effective period of the ephemeris has expired, the value of the time-dependent parameter is estimated based on the elapsed time since the ephemeris was acquired.

但し、「ｔ_oe」の単位は秒である。 The effective period of the ephemeris is ± 2 hours from the reference time “t _oe ”. Therefore, when the elapsed time since the acquisition of the ephemeris is “m hours”, the reference time “2 × m time = 7200 × m seconds” is added to the reference time “t _oe ” of the ephemeris. Is estimated. That is, the estimated reference time “t ′ _oe ” is calculated according to the following equation (1).

However, the unit of “t _oe ” is second.

但し、「Ωドット」は昇交点赤経の変化率、「Δｎ」は平均運動差である。 In this case, the estimated value of the ascending intersection red longitude “Ω ₀ ” and the average near point separation angle “M ₀ ” is the time difference “t ′ _oe −” between the reference time “t _oe ” and the estimated reference time “t ′ _oe ”. t _oe ”can be calculated according to the following equations (2) and (3).

However, “Ω dot” is the rate of change of ascending intersection, and “Δn” is the average motion difference.

For the time-dependent parameter, a collation mask is generated using the estimated values calculated by Expressions (1) to (3). On the other hand, since the time-independent parameter does not depend on time, the value cannot be estimated using the ephemeris reference time “t _oe ”. Therefore, for time-independent parameters, a matching mask is generated by using the original values included in the stored ephemeris.

  However, the time-dependent parameter is only an estimated value and may not be a correct value at present, so it cannot be used as it is for collation. Also, for time-independent parameters, the values change if the validity period of the ephemeris is different, so the original values cannot be used for matching as they are.

  Therefore, in the present embodiment, for each ephemeris parameter, a collation mask composed of a predetermined number of high-order bit values that are associated in advance with the ephemeris parameter is formed. That is, only a predetermined number of higher-order bits in the bit portion representing the estimated value or the original value are used for the collation. This is because the lower-order bit value is likely to contain an error and cannot be relied on, but the upper-order bit value is almost constant regardless of changes over time and may contain an error. This is because the bit value of the upper digit is used for collation as trustworthy.

  By the procedure so far, for example, a verification mask as shown in FIG. 1 is formed. In FIG. 1, the hatched portion shows the bit portion used for collation. In this embodiment, in order to generate a collation bit pattern for the ephemeris, a part of each word in the second subframe and the third subframe is hatched. After the collation mask is formed, based on the collation mask, the ephemeris parameter values are arranged in accordance with the communication format of the navigation data to generate a collation bit pattern.

(2) Within the effective period of the ephemeris If it is within the effective period of the ephemeris, the values of each ephemeris parameter included in the ephemeris are reliable, so the original value of the ephemeris parameter is used for verification. A bit pattern is generated. That is, the original value of each ephemeris parameter is arranged according to the communication format of navigation data to generate a verification bit pattern.

1-2. 2. Principle of Matching FIG. 2 is a diagram for explaining the principle of matching between a received data bit pattern and a matching bit pattern in this embodiment, and shows a part of the bit pattern. In this embodiment, each bit value of the received data bit pattern and each bit value of the verification bit pattern are collated in order, and the bit length that is continuously matched (hereinafter referred to as “continuous match bit length”). )) And consecutively mismatched bit lengths (hereinafter referred to as “sequential mismatch bit lengths”) are combined to determine suitability based on the “accumulated continuous bit length” as the identified cumulative length. .

  Specifically, it is determined whether or not the accumulated continuous bit length exceeds a first threshold set as a threshold for verification. When the first threshold value is exceeded, it is determined that the received data bit pattern and the verification bit pattern are matched, and when it is equal to or less than the first threshold value, it is determined that the received data bit pattern is not matched.

  What is characteristic in this embodiment is that not only the continuous match bit length but also the continuous mismatch bit length is taken into account for the match determination. In an environment where the received GPS satellite signal is a weak electric field signal (so-called weak electric field environment), such as when the mobile phone 1 is located indoors, demodulation of the GPS satellite signal may fail. In such a case, if the demodulation of one bit fails, since it is modulated by the phase inversion method, the subsequent bit value is reversely interpreted and demodulated. That is, once a demodulation error occurs, all bit values are inverted until a demodulation error occurs again. Even in such a case, in order to correctly determine suitability, the consecutive mismatch bit length is also added to the accumulated consecutive bit length.

  However, in this embodiment, when the continuous match bit length or the continuous mismatch bit length exceeds a second threshold value that is predetermined as a threshold value for determining the bit length, it is added to the cumulative continuous bit length. If it is less than or equal to the second threshold, it is not added to the cumulative continuous bit length. This is for the purpose of eliminating the case where errors frequently occur when demodulating GPS satellite signals and bit values are repeatedly inverted.

  A specific example will be described. Consider a case where a verification bit pattern and a received data bit pattern as shown in FIG. 2 are given. The description will be made assuming that the first threshold is “15 bits” and the second threshold is “3 bits”. In the verification bit pattern, bits surrounded by a thick frame are bits used for verification, and other bits are not used for verification.

  When the six bit values surrounded by the first thick frame F1 are collated, all the bit values are matched, so that the continuous match bit length is “6 bits” at this point. Next, the five bit values surrounded by the second thick frame F2 are collated, but the first bit value matches, but the second bit value does not match. The length is “6 + 1 = 7 bits”. Since “7 bits” that is the continuous match bit length exceeds “3 bits” that is the second threshold value, “7 bits” is added to the cumulative continuous bit length. Then, the continuous match bit length is reset.

  Thereafter, since the second to fifth bit values in the thick frame F2 all do not match, the continuous mismatch bit length at this time is “4 bits”. Next, the 12 bit values surrounded by the third thick frame F3 are collated, respectively, but the first and second bit values do not match, but the third bit value matches, The consecutive mismatch bit length is “4 + 2 = 6 bits”. Since “6 bits” that is the consecutive mismatch bit length exceeds the “3 bits” that is the second threshold value, “6 bits” is added to the accumulated continuous bit length. Then, the consecutive mismatch bit length is reset.

  After that, since the third to fifth bit values all match in the thick frame F3, the continuous match bit length is “3 bits”. This continuous coincidence bit length “3 bits” is equal to the second threshold value “3 bits” and does not exceed the second threshold value, and thus is reset without adding to the accumulated continuous bit length. After that, since the sixth and seventh bit values in the thick frame F3 do not match, the continuous mismatch bit length becomes “2 bits”, but this also does not exceed the second threshold value “3 bits”. Reset without adding to the cumulative continuous bit length.

  Thereafter, since all of the eighth to twelfth bit values match in the thick frame F3, the continuous match bit length becomes “5 bits”. Since the continuous matching bit length “5 bits” exceeds the second threshold value “3 bits”, “5 bits” is added to the accumulated continuous bit length. Then, the continuous match bit length is reset.

  By the processing so far, the cumulative continuous bit length becomes “7 + 6 + 5 = 18 bits”. This accumulated continuous bit length is compared with the first threshold value “15 bits”. As a result, since the accumulated continuous bit length exceeds the first threshold value, it is determined that the verification bit pattern and the received data bit pattern are matched.

  When it is determined that the verification bit pattern and the received data bit pattern are matched, for example, the time is set by adjusting the time to the head portion of the subframe that appears immediately after the portion determined to be matched, that is, the telemetry word (TLM). To decide. Since the main frame is always transmitted every minute or in synchronization with the timing 30 seconds after the minute, the reception timing data transmitted every 6 seconds is the head portion (TLM) of each subframe. But there is. For this reason, the time is set to the head part.

  The time may be set at the reception start timing of a word (0.6 second interval) that appears immediately after the portion determined to be compatible. In any case, time calibration is possible by using a communication format of standardized navigation data (navigation message).

  On the other hand, if it is determined that the verification bit pattern does not match the received data bit pattern, the bits of the verification bit pattern are shifted, and verification with the received data bit pattern is performed again. This bit shift and collation are repeatedly executed until collation for the entire length of the bit pattern is completed or until it is determined to be suitable in the middle.

2. Functional Configuration FIG. 3 is a block diagram showing a functional configuration of the mobile phone 1. The mobile phone 1 includes a GPS antenna 10, a GPS receiving unit 20, a host CPU (Central Processing Unit) 40, an operation unit 50, a display unit 60, a mobile phone antenna 65, and a mobile phone wireless communication circuit. A unit 70, a ROM (Read Only Memory) 80, and a RAM (Random Access Memory) 90 are provided.

  The GPS antenna 10 is an antenna that receives an RF (Radio Frequency) signal including a GPS satellite signal transmitted from a GPS satellite, and outputs the received signal to the GPS receiver 20. The GPS satellite signal is a 1.57542 [GHz] communication signal modulated by a direct spread spectrum system with a PRN (Pseudo Random Noise) code which is a kind of spreading code different for each satellite. The PRN code is a pseudo-random noise code having a repetition period of 1 ms with a code length of 1023 chips as one PN frame.

  The GPS receiver 20 is a position calculation circuit that measures the position of the mobile phone 1 based on a signal output from the GPS antenna 10 and a time determination circuit that determines time, and is a functional block corresponding to a so-called GPS receiver. is there. The GPS receiving unit 20 includes an RF (Radio Frequency) receiving circuit unit 21 and a baseband processing circuit unit 30. The RF receiving circuit unit 21 and the baseband processing circuit unit 30 can be manufactured as separate LSIs (Large Scale Integration) or can be manufactured as one chip.

  The RF receiving circuit unit 21 is an RF signal processing circuit block, and generates an oscillation signal for RF signal multiplication by dividing or multiplying a predetermined oscillation signal. Then, by multiplying the generated oscillation signal by the RF signal output from the GPS antenna 10, 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 or the like, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 30.

  The baseband processing circuit unit 30 performs correlation processing or the like on the IF signal output from the RF receiving circuit unit 21 to capture and extract GPS satellite signals, and navigation messages and time information carried in the GPS satellite signals. Etc. is a circuit unit that demodulates and extracts the signal. The baseband processing circuit unit 30 includes a satellite capturing unit 31, a CPU 33, a ROM 35, and a RAM 37.

  The satellite capture unit 31 is a circuit unit that captures a GPS satellite signal from the reception signal (IF signal) output from the RF reception circuit unit 21. The satellite acquisition unit 31 acquires a GPS satellite signal by performing a correlation calculation process that calculates and integrates the correlation between the PRN code and the replica code included in the received signal using, for example, FFT (Fast Fourier Transform) calculation. The replica code is a signal that simulates a PRN code included in a GPS satellite signal to be captured that is generated in a pseudo manner.

  If the GPS satellite signal to be captured is correct, the PRN code and replica code included in the GPS satellite signal match (capture success), and if they are incorrect, they do not match (capture failure). Therefore, by determining the peak of the calculated correlation value, it can be determined whether the acquisition of the GPS satellite signal was successful, by changing the replica code one after another, and performing the correlation operation with the same received signal, GPS satellite signals can be captured.

  The CPU 33 is a processor that comprehensively controls the baseband processing circuit unit 30 to the RF receiving circuit unit 21 according to various programs such as a baseband processing program stored in the ROM 35.

  The CPU 33 demodulates the GPS satellite signal captured by the satellite capturing unit 31 and stores the demodulated data in the RAM 37 as a received data bit pattern. Further, the CPU 33 uses the ephemeris acquired in advance and stored in the RAM 37 to generate a verification bit pattern. Then, the received data bit pattern and the verification bit pattern are verified, and the time is determined based on the verification result.

  The host CPU 40 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 ROM 80. Further, the host CPU 40 performs a position calculation process, determines the output position to be displayed on the display unit 60 by measuring the position of the mobile phone 1, generates a navigation screen in which the output position is plotted, and displays it on the display unit 60. Display.

  The operation unit 50 is an input device configured by, for example, a touch panel or a button switch, and outputs a pressed key or button signal to the host CPU 40. By operating the operation unit 50, various instruction operation inputs such as a call request, a mail transmission / reception request, a position calculation request, and a navigation screen display request are made.

  The display unit 60 is a display device that is configured by an LCD (Liquid Crystal Display) or the like and performs various displays based on display signals input from the host CPU 40. The display unit 60 displays a navigation screen on which output positions are plotted, time information, and the like.

  The cellular phone antenna 65 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 70 is a cellular phone communication circuit unit configured by an RF conversion circuit, a baseband processing circuit, and the like, and performs modulation and demodulation of the cellular phone radio signal, thereby enabling communication and mailing. Realize transmission / reception and so on.

  The ROM 80 is a read-only nonvolatile storage device, and stores a system program for the host CPU 40 to control the mobile phone 1 and various programs and data for realizing a position calculation function.

  The RAM 90 is a readable / writable volatile storage device, and forms a work area for temporarily storing a system program executed by the host CPU 40, various processing programs, data being processed in various processing, processing results, and the like. .

3. Data Configuration FIG. 4 is a diagram illustrating an example of data stored in the ROM 35 of the baseband processing circuit unit 30. The ROM 35 stores a time determination program 351 that is read by the CPU 33 and executed as a time determination process (see FIG. 7), and collation mask formation data 353. Further, the time determination program 351 has a subroutine for a verification bit pattern generation program 3511 executed as a verification bit pattern generation process (see FIG. 8) and a verification program 3513 executed as a verification process (see FIG. 9). Included as

  In the time determination process, the CPU 33 calculates the received data bit pattern obtained by demodulating the GPS satellite signal captured by the satellite capturing unit 31 and the verification bit pattern generated by the verification bit pattern generation process. This is a process of collating and determining the time using a predetermined reception timing defined as the communication format of the navigation data when the collation result is appropriate.

  In the verification bit pattern generation process, when the valid period of the ephemeris stored in the RAM 37 has expired, the CPU 33 sets the verification mask using the estimated value of the time-dependent parameter and the original value of the time-independent parameter. This is a process for generating a verification bit pattern. When the ephemeris is within the valid period, a verification bit pattern is generated using the original value of each ephemeris parameter.

  In addition, the collation processing means that the CPU 33 collates the received data bit pattern with the collation bit pattern for each bit, and uses the accumulated continuous bit length obtained by adding the continuous match bit length and the continuous mismatch bit length. This is processing for determining whether or not the bit pattern and the matching bit pattern are appropriate. These processes will be described later in detail using a flowchart.

  FIG. 6 is a diagram illustrating an example of the data configuration of the verification mask formation data 353. The collation mask formation data 353 is data used to form a collation mask. For each ephemeris parameter 3531, the position 3533 including the ephemeris parameter and the collation of the bits representing the ephemeris parameter are used. And a collation use bit 3535 indicating the higher-order bit to be stored.

  For example, the eccentricity “e”, which is a time-independent parameter, is included in the sixth and seventh words of the second subframe. The bits used for collation are the first to fifteenth bits of the upper digits.

  FIG. 5 is a diagram illustrating an example of data stored in the RAM 37 of the baseband processing circuit unit 30. The RAM 37 stores an ephemeris 371, an almanac 373, a received data bit pattern 375, and a verification bit pattern 377.

  The ephemeris 371 is detailed satellite orbit data for each GPS satellite, and includes values of ephemeris parameters such as satellite orbit parameters and clock correction parameters. The almanac 373 is data of approximate satellite orbits of all GPS satellites, and includes the values of almanac parameters such as satellite orbit parameters and clock correction parameters, like the ephemeris 371.

  These satellite orbit data can be obtained by decoding GPS satellite signals received from GPS satellites, or accessed to the base station server when the mobile phone 1 is turned on or periodically (eg once a day). However, it can be obtained by so-called server assist and stored in the RAM 37.

  The received data bit pattern 375 is a demodulated data bit pattern acquired by the CPU 33 demodulating the GPS satellite signal captured by the satellite capturing unit 31. The collation bit pattern 377 is a bit pattern used by the CPU 33 to collate with the received data bit pattern 375, and is generated by performing a collation bit pattern generation process.

4). Processing Flow FIG. 7 is a flowchart showing a flow of time determination processing executed in the baseband processing circuit unit 30 when the time determination program 351 stored in the ROM 35 is read and executed by the CPU 33. .

  Although not specifically described, during execution of the following time determination processing, reception of the RF signal by the GPS antenna 10 and down conversion of the RF signal to the IF signal by the RF reception circuit unit 21 are performed, and the IF signal is subjected to baseband processing. It is assumed that the circuit unit 30 is in a state of being output as needed. In addition, it is assumed that GPS satellite signals are captured by the satellite capturing unit 31 as needed.

  First, the CPU 33 stores the demodulated data obtained by demodulating the GPS satellite signal captured by the satellite capturing unit 31 in the RAM 37 as a received data bit pattern 375 (step A1). Then, it is determined whether or not a signal has been received for a specified number of seconds (for example, 10 seconds) or more (step A3). If it is determined that the specified number of seconds has not yet elapsed (step A3; No), the process goes to step A1. Return.

  If it is determined in step A1 that a signal has been received for the specified number of seconds or more (step A3; Yes), the CPU 33 determines whether the ephemeris 371 has been stored in the RAM 37 (step A5). And when it determines with not storing (step A5; No), a time determination process is complete | finished.

  If it is determined in step A5 that the ephemeris 371 has already been stored (step A5; Yes), the CPU 33 reads the verification bit pattern generation program 3511 stored in the ROM 35 and executes it for verification. Bit pattern generation processing is performed (step A7).

FIG. 8 is a flowchart showing the flow of the verification bit pattern generation process.
First, the CPU 33 determines whether or not the valid period of the ephemeris 371 stored in the RAM 37 has expired (step B1). If it is determined that the valid period has expired (step B1; Yes), “40 bits” is set as the first threshold value and “10 bits” is set as the second threshold value (step B3). .

Thereafter, the CPU 33 estimates values of the reference time “t _oe ”, the ascending intersection red longitude “Ω ₀ ”, and the average near point separation angle “M ₀ ”, which are time-dependent parameters, according to the equations (1) to (3). (Step B5). Then, the CPU 33 refers to the collation mask formation data 353 stored in the ROM 35 and forms a collation mask using the estimated value of the time-dependent parameter estimated in step B5 and the original value of the time-independent parameter. (Step B7).

  Then, the CPU 33 generates a verification bit pattern 377 in accordance with the communication format of the navigation data using the verification mask formed in step B7, and stores it in the RAM 37 (step B9). Then, the CPU 33 ends the verification bit pattern generation process.

  On the other hand, when it is determined in step B1 that the ephemeris 371 is within the valid period (step B1; No), the CPU 33 sets “60 bits” as the first threshold and “15 as the second threshold. Bit "is set (step B11).

  When the effective period of the ephemeris has expired, the first threshold value and the second threshold value are set to be smaller than when the effective period of the ephemeris is within the effective period (steps B3 and B11). This means that if the validity period of the ephemeris has expired, not all bits of all ephemeris parameters are used for matching, but only the higher-order bit value for each ephemeris parameter is used for matching. This is due to the fact that the number of bits available for verification is small.

  Thereafter, the CPU 33 uses the original value of each ephemeris parameter included in the ephemeris 371 stored in the RAM 37 to generate a verification bit pattern 377 in accordance with the communication format of the navigation data, and stores it in the RAM 37 (step B13). . Then, the CPU 33 ends the verification bit pattern generation process.

  Returning to the time determination process of FIG. 7, after performing the verification bit pattern generation process, the CPU 33 reads the received data bit pattern 375 and the verification data bit pattern 377 stored in the RAM 37 (step A9). And the collation process is performed by reading and executing the collation program 3513 memorize | stored in ROM35 (step A11).

FIG. 9 is a flowchart showing the flow of collation processing.
First, the CPU 33 sets the counter value to “0” and sets the cumulative continuous bit length to “0” (step C1). Then, the CPU 33 determines whether or not the bit is a collation use bit (step C3), and when it is determined that the bit is not a collation use bit (step C3; No), the process proceeds to step C25. If it is determined that the bit is a collation use bit (step C3; Yes), it is determined whether or not the bit value matches (step C5).

  If it is determined that the bit values match (step C5; Yes), the CPU 33 determines whether or not the previous difference flag is set to “same” (step C7). The previous difference flag is a flag for detecting whether the bit values are continuously matched or the bit values are continuously mismatched, and indicates whether the bit values matched in the previous determination. Yes. If it is determined that the previous difference flag has been set to “same” (step C7; Yes), the CPU 33 increments the counter value (step C9).

  On the other hand, when it is determined in step C5 that the bit values do not match (step C5; No), the CPU 33 determines whether or not the previous difference flag is set to “different” (step C11). If it is determined that the previous difference flag has been set to “different” (step C11; Yes), the CPU 33 increments the counter value (step C13).

  If it is determined in step C7 that the previous difference flag is not set to “same”, that is, set to “different” (step C7; No), the CPU 33 sets the previous difference flag to “same”. Set (step C15). If it is determined in step C11 that the previous difference flag is not set to “different”, that is, set to “same” (step C11; No), the CPU 33 sets the previous difference flag to “different”. Set (step C17).

  After step C15 or C17, the CPU 33 determines whether or not the counter value exceeds the second threshold value (step C19). If it is determined that the value has exceeded (step C19; Yes), the counter value is added to the accumulated continuous bit length (step C21). Then, the CPU 33 resets the counter value to “0” (step C23). When it is determined that the counter value is equal to or smaller than the second threshold (step C19; No), the process proceeds to step C23.

  Thereafter, the CPU 33 determines whether or not collation has been completed for all bits (step C25). If it is determined that the verification has not been completed (step C25; No), the process proceeds to the next bit. (Step C27), the process returns to Step C5. If it is determined that the collation has been completed for all bits (step C25; Yes), the CPU 33 terminates the collation process.

  After returning to the time determination process of FIG. 7 and performing the collation process, the CPU 33 determines whether or not the accumulated continuous bit length exceeds the first threshold (step A13). And when it determines with it being below a 1st threshold value (step A13; No), the bit of the bit pattern 377 for a collation is shifted (step A15), and a collation process is performed again (step A11).

  On the other hand, when it is determined that the accumulated continuous bit length exceeds the first threshold (step A13; Yes), it is determined that the received data bit pattern 375 and the verification bit pattern 377 are matched (step A17). Then, the time is determined by adjusting the time to the head portion (TLM) of the subframe that appears first after the matching portion (step A19). Then, the CPU 33 ends the time determination process.

5). Effects The mobile phone 1 receives a GPS satellite signal, which is a carrier wave signal, from a GPS satellite, and demodulates and acquires a data bit pattern from the received signal. Then, the acquired received data bit pattern and the verification bit pattern generated using the stored ephemeris are sequentially verified in bit units, and the bit length and the continuous value determined to be consistently matched by the verification. Whether or not the received data bit pattern and the verification bit pattern are appropriate is determined based on the accumulated continuous bit length obtained by adding the bit lengths determined to be inconsistent. Then, when it is determined as appropriate by the suitability determination, for example, the time is determined using the reception timing of the telemetry word (TLM) defined as the communication format of the navigation data.

  Appropriateness of the received data bit pattern obtained by demodulating the GPS satellite signal and the verification bit pattern is not only the bit length determined to be consistently matched, but also the bit length determined to be mismatched continuously. By making a decision in consideration, even in a weak electric field environment, etc., even when an error occurs when demodulating a GPS satellite signal and inversion occurs in the received data bit pattern, the suitability determination is performed correctly And the time can be determined.

  In the present embodiment, among the parameters included in the ephemeris, for the time-dependent parameter whose value changes depending on the time, an estimated value is calculated based on the acquired ephemeris and the validity period of the ephemeris. Ask. Then, a collation bit pattern is generated using the estimated value of the time-dependent parameter and the original value of the time-independent parameter which is a parameter whose value changes but does not depend on the time.

  Furthermore, in the present embodiment, when collation is performed, collation is performed using a predetermined higher-order bit value that is predetermined in association with each parameter. This is because the bit part of the lower digit of each parameter is likely to contain an error, so it is not used for collation, and the bit part of the upper digit that is less likely to contain an error is used for collation. It was decided.

6). Modification 6-1. Electronic Device The present invention can be applied to any electronic device as long as it is an electronic device provided with a position calculating device in addition to a mobile phone. For example, the present invention can be similarly applied to a notebook personal computer, a PDA (Personal Digital Assistant), a car navigation device, a portable navigation device, and the like.

6-2. In the above-described embodiment, the GPS is described as an example of the satellite position calculation system, but WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), GALILEO Other satellite position calculation systems may be used.

6-3. Differentiation of Processing The host CPU 40 may perform part or all of the processing executed by the CPU 33 of the baseband processing circuit unit 30. For example, the CPU 33 demodulates the GPS satellite signal captured by the satellite capturing unit 31 and outputs the demodulated data to the host CPU 40 as a received data bit pattern. Then, the host CPU 40 collates the received data bit pattern input from the CPU 33 with the collation bit pattern generated by performing the collation bit pattern generation process, and determines the time.

6-4. Generation of Verification Bit Pattern In the above-described embodiment, the ephemeris 371 acquired in advance and stored in the RAM 37 has been described as generating the verification bit pattern. However, the verification bit pattern is acquired in advance and stored in the RAM 37. A collation bit pattern may be generated in the same manner using the placed almanac 373. Since the almanac is included in the words of the 4th subframe and the 5th subframe, the collation mask is formed for the 4th subframe and the 5th subframe in the same manner as the above-described embodiment, and A bit pattern may be generated.

6-5. In the above-described embodiment, when the effective period of the ephemeris has expired, the two threshold values of the first threshold value and the second threshold value are both set smaller than those within the effective period of the ephemeris. Although described as a thing, it is good also as setting only any one threshold value small. Further, the first threshold value and the second threshold value may be set to fixed values regardless of the effective period of the ephemeris.

1 mobile phone, 10 GPS antenna, 20 GPS receiver,
21 RF receiving circuit section, 30 baseband processing circuit section, 31 satellite capturing section,
33 CPU, 35 ROM, 37 RAM, 40 host CPU,
50 operation section, 60 display section, 65 mobile phone antenna,
70 wireless communication circuit for mobile phone, 80 ROM, 90 RAM

Claims (6)

Receiving the carrier signal from a positioning satellite that periodically transmits a carrier signal that carries predetermined navigation data in a predetermined communication format by modulating the phase inversion method;
Demodulating and obtaining a data bit pattern from the received signal;
Collating the data bit pattern with a predetermined collation bit pattern in order in bit units;
Whether the data bit pattern and the matching bit pattern are appropriate is determined based on the identification accumulated length obtained by adding together the bit length determined to be consistently matched by the verification and the bit length determined to be mismatched continuously. To do
Determining a time using a predetermined reception timing defined in the communication format when the suitability is determined by the suitability determination;
Time determination method including The navigation data has a valid period,
The positioning satellite transmits a carrier wave signal carrying navigation data of the latest valid period,
Extracting a reusable bit portion having the same bit value as the bit pattern representing the latest navigation data from the acquired bit pattern representing the past navigation data;
Generating the verification bit pattern using the divertable bit portion;
Further including
The collation is to sequentially collate the data bit pattern and the collation bit pattern in bit units for the divertable bit portion.
The time determination method according to claim 1. The navigation data includes a parameter whose value gradually changes over time,
The extracting includes extracting a bit part of a predetermined upper digit from the bit parts representing the value of the parameter as the divertable bit part.
The time determination method according to claim 2.   4. The method according to claim 1, further comprising: estimating a part or all of the latest navigation data by using past navigation data and a period during which the past navigation data is valid to generate the verification bit pattern. The time determination method according to any one of the above.   The determination of suitability is performed by adding the bit length determined to be continuously matched by a predetermined continuous number or more by the collation and the bit length determined to be continuously mismatched by the continuous number or more. The time determination method according to any one of claims 1 to 4, further comprising: A receiving unit that receives the carrier signal from a positioning satellite that periodically transmits a carrier signal that carries predetermined navigation data in a predetermined communication format by modulating the phase inversion method;
A demodulator that demodulates and acquires a data bit pattern from the received signal;
A collation unit that collates the data bit pattern and a predetermined collation bit pattern in order in units of bits;
Whether the data bit pattern and the matching bit pattern are appropriate is determined based on the identification accumulated length obtained by adding together the bit length determined to be consistently matched by the verification and the bit length determined to be mismatched continuously. A suitability determination unit to perform,
A time determination unit that determines a time using a predetermined reception timing defined in the communication format when it is determined to be suitable by the suitability determination;
A time determination device comprising:

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