JP5408025B2 - Time information acquisition device and radio clock - Google Patents

Description

  The present invention relates to a time information acquisition device that receives a standard time radio wave and acquires the time information, and a radio clock equipped with the time information acquisition device.

  Currently, in Japan, Germany, the United Kingdom, Switzerland, etc., long standard time radio waves are transmitted from transmitting stations. For example, in Japan, standard time radio waves with amplitude modulation of 40 kHz and 60 kHz are transmitted from transmitting stations in Fukushima Prefecture and Saga Prefecture, respectively. The standard time radio wave includes a sequence of codes constituting a time code indicating the year, month, day, hour and minute, and is transmitted in one cycle of 60 seconds. That is, the period of the time code is 60 seconds.

  A timepiece (radio timepiece) capable of receiving a standard time radio wave including such a time code, taking out the time code from the received standard time radio wave, and correcting the time has been put into practical use. The reception circuit of the radio clock accepts the standard time radio wave received by the antenna and demodulates the standard time radio signal amplitude-modulated by a band pass filter (BPF) for extracting only the standard time radio signal, envelope detection, etc. A demodulation circuit and a processing circuit that reads a time code included in the signal demodulated by the demodulation circuit are provided.

  The conventional processing circuit synchronizes at the rising edge of the demodulated signal, and then binarizes at a predetermined sampling period to obtain TCO data of a unit time length (1 second) which is a binary bit string. Further, the processing circuit measures the pulse width of the TCO data (that is, the time of bit “1” or the time of bit “0”), and codes “P”, “0” corresponding to the width. "Or" 1 "is determined, and time information is acquired based on the determined code sequence.

  In a conventional processing circuit, a process of second synchronization processing, minute synchronization processing, code acquisition, and matching determination is performed from the start of reception of standard time radio waves to acquisition of time information. When processing cannot be completed properly in each process, the processing circuit needs to start processing from the beginning. For this reason, processing may have to be performed again and again due to the influence of noise included in the signal, and the time until the time information can be acquired may be significantly increased.

  Second synchronization is to detect the rise of a code that arrives every second among the codes indicated by the TCO data. The minute synchronization is to specify the start position of the minute. Data according to the JJY standard can be realized by detecting a portion where the position marker “P0” arranged at the end of the frame and the marker “M” arranged at the beginning of the frame are continuous. Since the beginning of the frame is recognized by the above-mentioned minute synchronization, code acquisition is started thereafter, and after acquiring the data for one frame, the parity bit is checked, and an impossible value (year, month, day, and time cannot actually occur) Value) is determined (consistency determination). For example, minute synchronization finds the beginning of a frame and may take 60 seconds. Of course, it takes several times as long to detect the beginning of a frame over several frames.

  In Patent Document 1, TCO data obtained by binarizing a demodulated signal at a predetermined sampling interval (50 ms) is acquired, and a data group consisting of binary bit strings every second (20 samples) is listed. It becomes. The apparatus disclosed in Patent Document 1 includes this bit string, a binary bit string template representing the code “P: position marker”, a binary bit string template representing the code “1”, and a binary bit string representing the code “0”. Each of the templates is compared with each other to obtain the correlation, and it is determined by the correlation whether the bit string corresponds to the code “P”, “1”, or “0”.

JP 2005-249632 A JP 2009-216544 A

  In the technique disclosed in Patent Document 1, TCO data, which is a binary bit string, is acquired and matched with a template. In a state where the electric field strength is weak or a state where a lot of noise is mixed in the demodulated signal, many errors are included in the acquired TCO data. Therefore, it is necessary to finely adjust the filter for removing noise from the demodulated signal and the threshold of the AD converter to improve the quality of TCO data.

  Further, Patent Document 2 generates input waveform data for one frame (60 seconds), has a similar data length, and predicts corresponding to the current time according to the time based on the internal clock (base time). There is disclosed a technique for generating waveform data, comparing sample values of input waveform data with corresponding sample values of predicted waveform data, and detecting the number of errors. In the technique of Patent Document 2, the predicted waveform data is shifted by 1 bit (the sample value at the end of the data becomes the first sample value), and the sample value of the input waveform data and the shifted predicted waveform data newly correspond to each other. Repeat the comparison with the sample value. Repeat the process only 60 times, find the predicted waveform data with the smallest number of errors from the number of errors for each of the predicted waveform data, and obtain the base time error based on the number of shifts of the found predicted waveform data To do.

  In the technique of Patent Document 2, input waveform data for 60 seconds is required. Further, it is necessary to generate 60 types of predicted waveform data by shifting and to compare the sample values of the input waveform data and the sample values of the predicted waveform data. Therefore, there is a problem that it takes a processing time to acquire input waveform data and compare sample values. In addition, since the reception status of radio waves is not always constant, it is desirable to shorten the reception time of standard time radio waves in order to acquire input waveform data.

  An object of this invention is to provide the time information acquisition apparatus and radio timepiece which can acquire the present time based on a standard time radio wave reliably and in a shorter time.

An object of the present invention is to sample the standard time radio signal from a second start position detected in a standard time radio signal including a time code representing received time information at a predetermined sampling period, and Input waveform data pattern generation means for generating an input waveform data pattern in which the sample value is either a first value indicating a low level or a second value indicating a high level and has one or more unit time lengths When,
The sample value of each sample point takes either the first value or the second value, and has the same time length and the same number of samples as the input waveform data pattern, A plurality of internal waveform data starting from the base time and a pattern start time shifted by a predetermined number of seconds before and after the base time. Internal waveform data pattern generating means for generating a pattern;
First error detection that determines whether or not the sample value of the input waveform data pattern matches the corresponding sample value of the internal waveform data pattern, and calculates a first error index value based on the number of errors indicating the mismatch Means,
A feature section including a predetermined time based on the pattern start times of the plurality of internal waveform data patterns for the internal waveform data pattern extracted based on the first error index value detected by the first error detection means A feature section data pattern generating means for generating a feature section data pattern including the code of
From the input waveform data obtained by sampling the standard time radio signal, a data pattern of a section corresponding to the feature section including the predetermined time with reference to the pattern start time of each of the plurality of internal waveform data patterns Comparison target data pattern generation means for generating a comparison target data pattern,
The feature section data pattern and each of the comparison target data patterns are compared to determine whether the corresponding sample values match or not, and a second error index value based on a second error number indicating the mismatch is obtained. Second error detection means for calculating;
Current time correction means for specifying an optimal internal waveform data pattern based on the second error index value and correcting the base time based on a pattern start time of the specified internal waveform data pattern. This is achieved by a time information acquisition device characterized by the above.

  In a preferred embodiment, when the first error detecting means determines that there are a plurality of internal waveform data patterns such that the bit error rate as the first index value is smaller than a predetermined allowable value, The second index value is calculated by the second error detecting means.

  In a more preferred embodiment, the predetermined time is a minute start time, and the feature section data pattern generation unit generates a feature section data pattern having a predetermined time length including before and after the minute start time.

  In another preferred embodiment, the input waveform data pattern generating means and the internal waveform data pattern generating means are based on a time difference between the time when the previous base time was corrected and the current time, and a predetermined timing accuracy. The time lengths of the input waveform data pattern and the internal waveform data pattern and the predetermined number of seconds for the internal waveform data pattern are determined.

Another object of the present invention is to provide the time information acquisition device,
The internal time measuring means for measuring the current time by an internal clock;
This is achieved by a radio timepiece comprising time display means for displaying the current time measured by the internal time measuring means or corrected by the current time adjusting means.

  According to the present invention, it is possible to provide a time information acquisition device and a radio timepiece that can acquire the current time based on the standard time radio wave reliably and in a shorter time.

FIG. 1 is a block diagram showing a configuration of a radio timepiece 10 according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration example of the receiving circuit 16 according to the present embodiment. FIG. 3 is a block diagram showing the configuration of the signal comparison circuit 18 according to the present embodiment. FIG. 4 is a diagram showing in more detail each of the codes constituting the standard time radio signal according to the JJY standard. FIG. 5 is a diagram showing an example of a standard time radio signal according to the JJY standard. FIG. 6 is a flowchart showing an outline of processing executed in the radio timepiece 10 according to the present embodiment. FIG. 7 is a diagram for explaining the outline of comparison between the input waveform data pattern and the internal waveform data pattern. FIG. 8 is a flowchart showing step 606 in more detail. FIG. 9 is a diagram illustrating an example of an input waveform data pattern and a plurality of internal waveform data patterns according to the present embodiment. FIG. 10 is a flowchart illustrating an example of the optimum pattern determination process according to the present embodiment. FIG. 11 is a diagram for explaining the data pattern of the feature section according to the present embodiment. FIG. 12 is a diagram for more specifically explaining the optimum pattern determination processing according to the present embodiment. FIG. 13 is a diagram for more specifically explaining the optimum pattern determination processing according to the present embodiment. FIG. 14 is a diagram for more specifically explaining the optimum pattern determination processing according to the present embodiment. FIG. 15 is a diagram illustrating an example of the time length a and the time length b before and after the input waveform data pattern.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the embodiment of the present invention, a standard time radio wave in a long wave band is received, the signal is detected, a sequence of codes indicating a time code included in the signal is extracted, and based on the sequence of the codes The radio timepiece for correcting the time is provided with the time information acquisition device according to the present invention.

  Currently, standard time radio waves are transmitted from a predetermined transmitting station in Japan, Germany, the United Kingdom, Switzerland, and the like. For example, in Japan, standard time radio waves with amplitude modulation of 40 kHz and 60 kHz are transmitted from transmitting stations in Fukushima Prefecture and Saga Prefecture, respectively. The standard time radio wave includes a string of codes constituting a time code indicating the year, month, day, hour and minute, and is transmitted in one cycle of 60 seconds. Since one code has a unit time length (1 second), one cycle can include 60 codes.

  FIG. 1 is a block diagram showing a configuration of a radio timepiece according to an embodiment of the present invention. As shown in FIG. 1, the radio timepiece 10 according to the present embodiment includes a CPU 11, an input unit 12, a display unit 13, a ROM 14, a RAM 15, a receiving circuit 16, an internal clock circuit 17, and a signal comparison circuit 18.

  The CPU 11 reads out a program stored in the ROM 14 at a predetermined timing or in response to an operation signal input from the input unit 12, expands the program in the RAM 15, and configures the radio clock 10 based on the program. Execute instructions and data transfer. Specifically, for example, digital signals based on signals obtained from the receiving circuit 16 by controlling the receiving circuit 16 to receive standard time radio waves at predetermined time intervals or in accordance with instructions input to the input unit 12. A sequence of codes included in the standard time radio signal is specified from the data, and a process for correcting the base time BT, which is the internal time obtained by the internal timing circuit 17 based on the sequence of codes, is obtained by the internal timing circuit 17. Processing for transferring the received base time BT to the display unit 13 is executed.

  In the present embodiment, as will be described later, the processing start time CT of the input waveform data pattern having one or more unit time lengths is specified using the base time BT that is the time obtained by the internal clock circuit 17, A plurality of internal waveform data patterns of one or more unit time lengths are generated with a predetermined time before and after the processing start time CT as the start time, and from the plurality of internal waveform data patterns and the signal obtained by the receiving circuit 16 Each of the generated input waveform data patterns is compared. As a result of the comparison and the comparison of the waveform data pattern for the characteristic section described later, the code included in the received signal is specified, and the error between the base time BT and the time based on the received signal is calculated. The base time BT in the time measuring circuit 17 can be corrected.

  The input unit 12 includes a switch for instructing execution of various functions of the radio timepiece 10, and outputs a corresponding operation signal to the CPU 11 when the switch is operated. The display unit 13 includes a dial, an analog pointer mechanism controlled by the CPU 11, and a liquid crystal panel, and displays a time based on the base time BT timed by the internal clock circuit 17. The ROM 14 stores a system program, an application program, and the like for operating the radio timepiece 10 and realizing a predetermined function. The program for realizing the predetermined function includes a signal comparison circuit 18 for second pulse position detection processing (second synchronization processing), comparison processing with the internal waveform data pattern and the input waveform data pattern in the present embodiment, and the like. A program to control The RAM 15 is used as a work area for the CPU 11 and temporarily stores programs and data read from the ROM 14, data processed by the CPU 11, and the like.

  The reception circuit 16 includes an antenna circuit, a detection circuit, and the like, obtains a signal demodulated from the standard time radio wave received by the antenna circuit, and outputs the signal to the signal comparison circuit 18. The internal clock circuit 17 includes an oscillation circuit (not shown), counts clock signals output from the oscillation circuit, counts time based on the base time BT, and outputs time data to the CPU 11.

  FIG. 2 is a block diagram showing a configuration example of the receiving circuit 16 according to the present embodiment. As shown in FIG. 2, the receiving circuit 16 is an output of the antenna circuit 50 that receives the standard time radio signal, the filter circuit 51 that removes noise of the standard time radio signal received by the antenna circuit 50, and the filter circuit 51. An RF amplification circuit 52 that amplifies a high frequency signal, and a detection circuit 53 that detects a signal output from the RF amplification circuit 52 and demodulates a standard time radio wave signal. The signal demodulated by the detection circuit 53 is a signal comparison circuit. 18 is output.

  FIG. 3 is a block diagram showing the configuration of the signal comparison circuit 18 according to the present embodiment. As shown in FIG. 3, the signal comparison circuit 18 according to this exemplary embodiment includes an input waveform data generation unit 21, a reception waveform data buffer 22, an internal waveform data pattern generation unit 23, a waveform cutout unit 24, an error detection unit 25, It has a match determination unit 26, a second synchronization execution unit 27, a feature section data pattern generation unit 28, and a comparison target waveform cutout unit 29.

  The input waveform data generation unit 21 converts the signal output from the receiving circuit 16 into digital data whose value takes one of a plurality of values (“1” or “0”) at a predetermined sampling interval. Convert to In the first embodiment, for example, the sampling interval is 50 ms, and data of 20 samples per second can be acquired. The reception waveform data buffer 22 sequentially stores the data generated in the input waveform data generation unit 21. The reception waveform data buffer 22 can store a plurality of unit time lengths (1 unit time: 1 second) of data (for example, 20 seconds of data). Will be erased.

  Further, the input waveform data generation unit 21 determines the sample position D (n) of the input waveform data every second, that is, every code from the second start position after the second position is determined by the second synchronization by the second synchronization execution unit 27. Is generated. In this case, for example, data corresponding to a predetermined time zone (500 ms to 800 ms) is obtained from the values acquired at the predetermined sampling interval, and there are many data values “1” and “0”. By determining whether or not, the sample value D (n) of the code data per second can be obtained.

  In the present embodiment, data corresponding to one code generated by the input waveform data generation unit 21 is referred to as code data, and its value is referred to as a sample value. A plurality of code data having a predetermined unit time length (a predetermined number of seconds) is referred to as an input waveform data pattern. Also in the internal waveform data pattern generation unit 23 described below, data corresponding to one code is referred to as code data of internal waveform data, and code data having a predetermined unit time length (predetermined number of seconds) is referred to as an internal waveform data pattern. .

  The internal waveform data pattern generation unit 23 generates a plurality of internal waveform data patterns to be compared with the input waveform data pattern. The plurality of internal waveform data patterns will be described in detail later. The waveform cutout unit 24 extracts an input waveform data pattern having the same unit time length as the unit time length of the internal waveform data pattern from the received waveform data buffer 22.

  Hereinafter, the standard time radio signal and its sign according to JJY will be described. FIG. 4 is a diagram showing in more detail each of the codes constituting the standard time radio signal according to JJY. As shown in FIG. 4, JJY includes codes indicating “P”, “1”, and “0” having a unit time length of 1 second. In the code “0”, the high level (value “1”) is set in the first 800 ms section, and the low level (value “0”) is set in the remaining 200 ms section. In the code “1”, the high level (value “1”) is set in the first 500 ms section, and the low level (value “0”) is set in the remaining 500 ms section. In addition, in the code “P”, the high level (value “1”) is set in the first 200 ms section, and the low level (value “0”) is set in the remaining 800 ms section.

  FIG. 5 is a diagram showing an example of a standard time radio signal according to the JJY standard. As shown in FIG. 5, the standard time radio signal according to the JJY standard is transmitted in the order in which one of the codes “0”, “1” and “P” shown in FIG. 4 is determined. The standard time radio signal has 60 seconds as one frame, and one frame includes 60 codes. In the standard time radio signal, a position marker “P1”, “P2”,... Or a marker “M” arrives every 10 seconds, and a position marker “P0” arranged at the end of the frame and A portion where the marker “M” arranged at the head of the frame continues is detected. In JJY, the head of the code rises from a low level to a high level. Finding the head position of this code is called second synchronization. Finding the head position of a frame that arrives every 60 seconds is called minute synchronization.

  The second synchronization execution unit 27 detects the second start position in the input waveform data generated by the input waveform data generation unit 21 by, for example, a known conventional method. For example, in the standard time radio signal according to JJY, as described above, it rises at the leading position of the second in all codes. Therefore, it is possible to detect the leading position of the second by detecting the rising edge of this signal.

  The error detection unit 25 calculates the number of errors indicating a mismatch between the values of each of the plurality of internal waveform data patterns and the input waveform data pattern. As described above, the input waveform data pattern has the sample value D (n) of the sign data of the input waveform data per second. Similarly, the internal waveform data pattern has a sample value P (n) of the sign data of the internal waveform data per second. Therefore, if the sample value of the code data of the input waveform data is compared with the sample value of the code data of the corresponding internal waveform data, and if there is a mismatch, the number of errors is incremented by “1”. The number of errors can be calculated.

  Further, the coincidence determination unit 26 calculates a bit error rate (BER) based on the number of errors for each of the plurality of internal waveform data patterns, and based on the calculated BER, the internal waveform data having a BER smaller than a predetermined allowable maximum value. Identify the pattern. As a result, an internal waveform data pattern that matches the input waveform data pattern can be identified.

  In the calculation of the coincidence determination unit 26, there may be a case where there are a plurality of internal waveform data patterns whose bit error rate BER is smaller than a predetermined allowable maximum value. In such a case, it is necessary to determine which of the plurality of internal waveform data patterns really matches the input waveform data pattern. In the present embodiment, as will be described in detail later, based on each pattern start time of the internal waveform data pattern, the minute start position in the internal waveform data is found, and the corresponding in the input waveform data corresponding to that position. The comparison target data pattern is specified. Then, the feature section data pattern indicating the front and back of the minute position based on the internal waveform data pattern is compared with the identified comparison target data pattern.

  The feature section data pattern generation unit 28 generates a specific section data pattern indicating the front and back of the above-mentioned start position. Further, the comparison target waveform cutout unit 29 acquires a data pattern (comparison target data pattern) in the input waveform data corresponding to the start position of each of the plurality of internal waveform data. The feature section data pattern and the comparison target data pattern will be described in detail later.

  FIG. 6 is a flowchart showing an outline of processing executed in the radio timepiece 10 according to the present embodiment. As shown in FIG. 6, the CPU 11 determines the time length a of the input waveform data pattern (step 601). In the present embodiment, the input waveform data has one sample per second. Therefore, if the time length is a (second), an input waveform data pattern composed of a sample points is generated. The determination of the time length a will be described later. Further, the CPU 11 determines a time length b that defines the pattern start time of the internal waveform data pattern (step 602). For example, the time length b that defines the pattern start time is the standard time from the period when the time adjustment is not performed in the radio timepiece 10, that is, from the time when the time adjustment was performed by receiving the standard time radio signal last time. It can be determined based on the period until the time radio signal is received and the timekeeping accuracy of the radio timepiece 10.

  For example, if the period in which the time is not corrected is one month (30 days) and the timekeeping accuracy of the radio clock is ± 15 seconds (monthly difference ± 15 seconds) in one month, the time length b is 15 or more. Therefore, when the time length b = 15, 2b + 1 = 31 internal waveform data patterns are generated. The pattern start time is CT-15, CT-14,..., CT, CT + 1,..., CT + 15, where CT is the current time based on the base time BT.

  Thereafter, the CPU 11 instructs the reception circuit 16 to start receiving the standard time radio signal, and the reception circuit 16 receives the standard time radio signal and outputs the received signal to the signal comparison circuit 18 (step 603). The second synchronization execution unit 27 of the signal comparison circuit 18 detects the second head position (second synchronization) in accordance with an instruction from the CPU 11 (step 604). Second synchronization is realized by, for example, a known conventional method. By the second synchronization, the second start position in the input waveform data is specified, and the time difference between the start of the input waveform data and the specified second start position is obtained. The detection of the second head position by the second synchronization execution unit 27 is continued until the detection is completed (see step 605).

  When the second synchronization is completed (Yes in step 605), the signal comparison circuit 18 compares the input waveform data pattern with a plurality of internal waveform data patterns in accordance with an instruction from the CPU 11 (step 606). FIG. 7 is a diagram for explaining the outline of comparison between the input waveform data pattern and the internal waveform data pattern, and FIG. 8 is a flowchart showing step 606 in more detail. As shown in FIG. 7, the input waveform data pattern 700 has a time length a (a = 12 seconds in the example of FIG. 7), and corresponds to 12 codes each indicating a value of “0” or “1”. Code data D (0) to D (11) to be included.

  The internal waveform data (symbol 710) is a sequence of codes of standard time radio signal in accordance with the base time BT. For example, in the base time BT, from the position of “00 seconds”, that is, from the minute start position, as shown in FIG. 5, it starts with a marker (symbol “P”), and a code “P” appears every 10 seconds. In addition, the 60th is a string of codes that is a marker (symbol “P”).

  The internal waveform data pattern is obtained by cutting out data having the same time length as the input waveform data pattern from the internal waveform data corresponding to the code sequence of the standard time radio signal according to the base time BT (for example, reference numeral 711). 712, 713). In the present embodiment, the input waveform data pattern has a data length of a, and internal waveform data patterns having different pattern start times in the range of b seconds (± b rows) around the processing start time CT. Generated. Therefore, in order to generate 2b + 1 internal waveform data patterns, internal waveform data having a time length of 2b + a is required.

  As shown in FIG. 8, the CPU 11 acquires a process start time CT based on the base time BT (step 801). The processing start time CT is transmitted to the waveform cutout unit 24. The waveform cutout unit 24 cuts out the input waveform data pattern having the time length a starting from the processing start time CT from the input waveform data (step 802). FIG. 9 is a diagram illustrating an example of an input waveform data pattern and a plurality of internal waveform data patterns according to the present embodiment. As shown in FIG. 9, the input waveform data pattern includes a sample values corresponding to the time length a (sample values D (0) to time CT + (a-1) based on code data of input waveform data at time CT). Sample value D (a-1)) based on the code data of

  Next, the parameter n for specifying the internal waveform data pattern used in the internal waveform data pattern generation unit 23 and the like of the signal comparison circuit 18 is initialized to “1” (step 803). The internal waveform data pattern generation unit 23 generates an internal waveform data pattern having a time length a starting from the time CT-b + (n−1) (step 804).

  For example, initially (parameter n = 1), the internal waveform data pattern PP (-b) starts with a sample value P (-b) corresponding to the sign of the standard time radio signal at time CT-b. Sample values P (-b + (a-1)) of sample values P (-b) to CT-b + (a-1) of time CT-b (see reference numeral 901). Similarly, if the parameter n = 2, the internal waveform data pattern PP (−b + 1) has a number starting from the sample value P (−b + 1) corresponding to the sign of the standard time radio signal at time CT−b + 1. Sample values P (-b + 1) of the time CT-b + 1 sign to sample values P (-b + a) of the time CT-b + a (see reference numeral 902).

  In the present embodiment, the internal waveform data PP (−b) to PP (b) having the pattern start times respectively from time CT−b to time CT + b by incrementing the parameters as described later (see step 808). (See reference numerals 901, 902, 910, 911, and 912).

  After the internal waveform data pattern PP (n) is generated in step 804, the error detection unit 25 compares the input waveform data pattern DP with the corresponding sample value of the internal waveform data pattern PP (n), A bit error rate BER (n) is calculated based on the match / mismatch (step 805). The bit error rate BER (n) can be obtained as (number of mismatched samples / total number of samples (= a)). The coincidence determination unit 26 determines whether the obtained bit error rate BER (n) is smaller than a predetermined allowable maximum value (step 806). When it is determined Yes in step 806, the coincidence determination unit 26 temporarily stores the bit error rate BER (n) and the parameter n in the RAM 15 (step 807).

  Next, the CPU 11 increments the parameter n (step 808), and determines whether n is larger than 2b + 1 (step 809). If it is determined No in step 809, the process returns to step 804, and the next new internal waveform data pattern PP (n) is generated and compared with the input waveform data pattern DP.

  By repeating the process shown in FIG. 8, information (parameter n and BER (n)) about the internal waveform data pattern PP (n) related to the BER smaller than the allowable maximum value can be obtained. When step 606 is completed, the CPU 11 refers to the information about the internal waveform data pattern PP (n) stored in the RAM 15 to determine whether there are a plurality of internal waveform data patterns whose bit error rate BER is smaller than the allowable maximum value. Is determined (step 607). When it is determined Yes in step 607, the CPU 11 causes the signal comparison circuit 18 to execute an optimum pattern determination process (step 608). FIG. 10 is a flowchart showing an example of the optimum pattern determination process according to the present embodiment, and FIG. 11 is a diagram for explaining the data pattern of the feature section according to the present embodiment.

  As shown in FIG. 10, the feature section data pattern generation unit 28 generates a feature section data pattern based on any internal waveform data pattern PP (n) related to the BER smaller than the allowable maximum value (step 1001). The feature section based on the present embodiment refers to a predetermined section before and after the next minute start using the start time based on the internal waveform data pattern PP (n). In FIG. 11, the start time T1 of the internal waveform data pattern PP (n1) is (h1, m1, s1) (representing h: hour, m: minute, s: second). In data including the internal waveform data pattern PP (n1) at the start time T1 (hereinafter referred to as “internal waveform data 1”), the next minute start position (time: (h1, (m1 + 1)) ) And s1) As the data pattern of the feature section, for example, a data pattern of 5 seconds after 2 seconds from the second minute before (58 seconds) from the start position of the next minute can be used.

  As shown in FIG. 5, in the code of the standard time radio signal according to JJY, the code “P” is continuous only at 59 seconds and 0 seconds. Therefore, the code string of the section including the part before and after the minute start position has a remarkable feature compared with the code string of the other sections. Therefore, in the present embodiment, the data pattern of the feature section according to the time based on the internal waveform data pattern is generated as the feature section data pattern, and as described below, according to the time based on the internal data pattern. The data of the section corresponding to the feature section in the input waveform data is generated as the comparison target data pattern.

  The comparison target waveform cutout unit 29 specifies a position corresponding to the feature section in the input waveform data based on the start time of the internal waveform data pattern (step 1002). As shown in FIG. 11, assuming that the start time T1 of the internal waveform data pattern PP (n1) = (h1, m1, s1), the next minute start position based on the start time of the internal waveform data pattern PP (n1) (H1, (m1 + 1), 00) is a position after (60-s1) seconds from T1 (see reference numerals 1100 and 1110). Similarly, if the start time T2 of the internal waveform data pattern PP (n2) = (h1, m1, s2), the next minute start position (h1, ( m1 + 1), 00) is a position after (60-s2) seconds from T2 (see reference numerals 1101 and 1111).

  The comparison target waveform cutout unit 29 cuts out the data pattern in the corresponding feature section identified in step 1002 from the input waveform data (step 1003). A data pattern at a position corresponding to a feature section cut out from the input waveform data is referred to as a comparison target data pattern. Next, the error detection unit 25 compares the feature section data pattern based on the internal waveform data with the comparison target data pattern based on the input waveform data, and calculates the bit error rate BER (step 1004).

  The coincidence determination unit 26 determines whether the BER calculated in step 1004 is smaller than the minimum BER value BERmin stored in the RAM 15 (step 1005). When it is determined Yes in step 1005, the coincidence determination unit 26 stores the BER calculated in step 1004 in the RAM 15 as BERmin (step 1006), and the internal waveform data pattern from which the new BERmin is obtained. Is stored in the RAM 15 (step 1007).

  The CPU 11 determines whether the processing has been completed for all the internal waveform data patterns in which the bit error rate BER is smaller than the allowable maximum value (step 1008). If it is determined No in step 1008, the CPU 11 specifies the next internal waveform data pattern (step 1009) and returns to step 1001. If it is determined YES in step 1008, the CPU 11 refers to the RAM 15 and sets the internal waveform data pattern indicating the minimum value BERmin of the bit error rate as an optimal pattern, based on the optimal pattern, Time information based on the signal is acquired (step 1010).

  In FIG. 6, when it is determined No in step 607, there is one internal waveform data pattern in which the bit error rate BER is smaller than the allowable maximum value, and the internal waveform data pattern is the optimum pattern. When it is determined No in step 607 or after the optimum pattern determination process in step 608 is executed, the CPU 11 performs the base time BT timed by the internal timer circuit 17 and the standard time radio signal based on the optimum pattern. The base time BT is corrected based on the difference from the time information based on (step 609). In step 609, in addition to correcting the time of the internal clock circuit 17, the corrected current time is displayed on the display unit 13.

  12 to 14 are diagrams for more specifically explaining the optimum pattern determination processing according to the present embodiment. As shown in FIG. 12, the input waveform data pattern DP and the plurality of internal waveform data patterns are respectively compared, and the bit error rate BER between the internal waveform data pattern PP (n1) and the internal waveform data pattern PP (n2) is determined. These are considered to be smaller than the maximum allowable value (see FIG. 13). Actually, the internal waveform data pattern PP (n2) is a data pattern that should be determined to be consistent. In the optimum pattern determination process, as shown in FIG. 14, the comparison target data pattern (reference numeral 1401) obtained based on the time (start time) of the internal waveform data pattern PP (n1) and the internal waveform data pattern PP (n2 ) And a comparison target data pattern (symbol 1402) obtained based on the time (start time) of) are generated, and each is compared with the feature section data pattern (symbol 1410). As can be understood from FIG. 14, in this example, the comparison target data pattern (reference numeral 1402) obtained based on the time (start time) of the internal waveform data pattern PP (n2) matches the feature section data pattern (reference numeral 1410). Therefore, the internal waveform data pattern PP (n2) is determined as the optimum pattern, and the base time BT is corrected based on the time of the internal waveform data pattern PP (n2).

  In the present embodiment, the CPU 11 determines the time length a of the input waveform data pattern (step 601 in FIG. 6) and the time for defining the start time of the internal waveform data pattern in the processing in the radio timepiece 10. The length b is determined (step 602 in FIG. 6). The time lengths a and b will be described below.

Consider a bit error rate BER depending on the number of samples a in received data (input waveform data). If the number of samples is n, the occurrence probability of “1” is assumed to be p, the occurrence probability of “0” is assumed to be 1-p, and of the n pieces, the e code is “1”. The probability R that the base time BT timed by the internal time measuring circuit 17 matches the 1/0 code is expressed by the following equation (1).
R = (p ^ e) * ((1-p) ^ (n-e)) (1)

Here, if both the probability that the code “1” appears and the probability that “0” appears are P = ½, the bit error BER of the input waveform data is required to be “10 ^ −8”. In order to satisfy BER ≦ 10 ^ −8, the following equation (2) is established.
(1/2) ^ n ≦ 10 ^ -8 (2)
When this is solved, n ≧ 27.

  The time is expressed in, for example, hours, minutes, and seconds. One day is 60 * 60 * 24 = 86400 seconds, and takes a discrete value in seconds. However, in the timepiece 10, a period in which the time is not adjusted, that is, a period from the time when the standard time radio signal was received and the time correction was performed last time until the time when the standard time radio signal is to be received this time. Thus, the degree of deviation can be estimated. Therefore, it is sufficient to perform time verification within an appropriate range in which the degree of deviation is estimated.

That is, if verification for 86400 seconds is not required, the period is one month, and the accuracy of the radio clock is a monthly difference of ± 15 seconds, a comparison considering 30 seconds before and after may be executed. That is, 31 patterns may be generated as the internal waveform data pattern and compared with the input waveform data pattern. Since the comparison of 31 patterns (31 verifications) is a pattern that has 31 adjacent times as the start time,
The BER is further reduced by 31/86400. Conversely, if a similar BER is assumed, the BER required by the input waveform data is
(10 ^ -8) * 86400/31.

Further, the bit acquisition rate BER (a) when the number of samples of the input waveform data pattern is reduced to a is expressed by the following equation (3).
BER (a) = {(1/2) ^ a} (3)

At this time, the time length of the input waveform data pattern is a (second). Therefore,
{(1/2) ^ a} ≦ {10 ^ −8} * 86400
A must be able to be set, and at this time, a ≧ 15 (seconds). Further, in consideration of b indicating the length of time before and after generating the internal waveform data pattern, the following equation (4) is obtained.
{(1/2) ^ a} * (1 + 2 * b) ≦ {10 ^ −8} * 86400 (4)

  In this case, ± b seconds is the correctable time, and the total time length of the internal waveform data for matching with the base time BT by the internal clock circuit 17 is a + 2 * b (see FIG. 7).

  When the equation (4) is obtained, a is 15 seconds or longer. For example, the correctable time is as shown in FIG. In the present embodiment, a table including the values shown in FIG. 15 is stored in the RAM 15, and the CPU 11 does not perform time correction (a time difference between the time when the previous base time was corrected and the current time). Based on the accuracy of the radio timepiece 10, the time lengths a and b can be obtained by referring to the table.

  In this embodiment, when there are a plurality of internal waveform data patterns having a number of errors smaller than a predetermined number in comparison between the input waveform data pattern and a plurality of internal waveform data patterns having different pattern start times, the feature interval data pattern The generation unit 28 generates a feature section data pattern including a feature section code including a predetermined time based on the pattern start times of the plurality of internal waveform data patterns. The comparison target waveform cutout unit 29 generates a comparison target data pattern that is a data pattern of a section corresponding to the feature section including a predetermined time with reference to each pattern start time. The error detection unit 25 compares the feature section data pattern and the comparison target data pattern to detect the number of errors, and the coincidence determination unit 26 specifies an optimal internal waveform data pattern based on the detected number of errors.

  Therefore, when there are a plurality of internal waveform data patterns in which the number of errors (or bit error rate) is smaller than a predetermined allowable value in the comparison between the first input waveform data pattern and a plurality of internal waveform data patterns, it is further characterized By comparing the waveform data pattern with the data pattern to be compared, it is possible to specify the internal waveform data pattern that really matches the waveform. Thereby, it is possible to obtain an accurate time based on the standard time radio signal.

  This is particularly effective when the number of samples of the input waveform data pattern (and the internal waveform data pattern) is small, or when the signal strength of the standard time radio signal is small and the input waveform data pattern contains noise.

  Further, when there are a plurality of internal waveform data patterns having a bit error rate smaller than a predetermined allowable value, the feature waveform data pattern and the comparison target waveform data pattern are compared. That is, when it is confusing which internal waveform data pattern matches the input waveform data pattern, the comparison between the characteristic waveform data pattern and the comparison target waveform data pattern is further performed. Therefore, only when further verification is required, the characteristic waveform data pattern and the comparison target waveform data pattern are compared to prevent the processing time from being unnecessarily increased.

  In the present embodiment, the predetermined time is the minute start time, and the feature section data pattern generation unit 28 generates a feature section data pattern having a predetermined time length including before and after the minute start time. For example, in the standard time radio signal according to JJY, the code “P” continues only before and after the minute start position, and has a remarkable feature compared to the code strings of other sections. Therefore, it is possible to determine an exact match by comparing the feature section data pattern including the part before and after the minute start position and the comparison target data pattern.

  Further, in the present embodiment, based on the time difference between the time when the previous base time was corrected and the current time, and the predetermined timing accuracy, the time length of the input waveform data pattern and the internal waveform data pattern, Then, a predetermined number of seconds indicating a shift in pattern start time for the internal waveform data pattern is determined. This makes it possible to optimize the time length of the appropriate data pattern according to the period in which the base time is not corrected, and the number of seconds for shifting the pattern start time in the internal waveform data pattern.

  The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

10 radio time clock 11 CPU
12 Input unit 13 Display unit 14 ROM
15 RAM
16 Receiving Circuit 17 Internal Clock Circuit 18 Signal Comparison Circuit

Claims (5)

The standard time radio signal is sampled at a predetermined sampling period from the second position detected in the standard time radio signal including a time code representing the received time information, and the sample value of each sample point is low level. An input waveform data pattern generating means for generating an input waveform data pattern having a unit time length of one or more and a first value indicating a high level and a second value indicating a high level;
The sample value of each sample point takes either the first value or the second value, and has the same time length and the same number of samples as the input waveform data pattern, A plurality of internal waveform data starting from the base time and a pattern start time shifted by a predetermined number of seconds before and after the base time. Internal waveform data pattern generating means for generating a pattern;
First error detection that determines whether or not the sample value of the input waveform data pattern matches the corresponding sample value of the internal waveform data pattern, and calculates a first error index value based on the number of errors indicating the mismatch Means,
A feature section including a predetermined time based on the pattern start times of the plurality of internal waveform data patterns for the internal waveform data pattern extracted based on the first error index value detected by the first error detection means A feature section data pattern generating means for generating a feature section data pattern including the code of
From the input waveform data obtained by sampling the standard time radio signal, a data pattern of a section corresponding to the feature section including the predetermined time with reference to the pattern start time of each of the plurality of internal waveform data patterns Comparison target data pattern generation means for generating a comparison target data pattern,
The feature section data pattern and each of the comparison target data patterns are compared to determine whether the corresponding sample values match or not, and a second error index value based on a second error number indicating the mismatch is obtained. Second error detection means for calculating;
Current time correction means for specifying an optimal internal waveform data pattern based on the second error index value and correcting the base time based on a pattern start time of the specified internal waveform data pattern. A time information acquisition device characterized by that.   When the first error detection means determines that there are a plurality of internal waveform data patterns such that the bit error rate as the first index value is smaller than a predetermined allowable value, the second error detection means 2. The time information acquisition apparatus according to claim 1, wherein the second index value is calculated by the following.   The predetermined time is a minute start time, and the characteristic interval data pattern generation unit generates a characteristic interval data pattern having a predetermined time length including before and after the minute start time. The time information acquisition device described in 1.   The input waveform data pattern generation unit and the internal waveform data pattern generation unit are configured to generate the input waveform data pattern and the internal waveform based on a time difference between a time at which the previous base time was corrected and a current time, and a predetermined timing accuracy. The time information acquisition apparatus according to any one of claims 1 to 3, wherein a time length of a waveform data pattern and the predetermined number of seconds for the internal waveform data pattern are determined. The time information acquisition device according to any one of claims 1 to 4,
The internal time measuring means for measuring the current time by an internal clock;
A radio-controlled timepiece comprising time display means for displaying the current time measured by the internal time measuring means or corrected by the current time adjusting means.

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