JP5037397B2 - Standard radio wave receiver - Google Patents

Description

  The present invention relates to a standard radio wave receiver that receives a standard radio wave including time information, and more particularly to a radio timepiece.

[Explanation of standard radio wave and time code]
Standard radio waves are transmitted in a long wave band of several tens of kHz or a short wave band of 1 to 15 MHz in order to provide a frequency standard and a standard of time information in various countries around the world. This time information generally includes information such as time, date, year, day of the week, leap second, and daylight saving time. In Japan, the information is transmitted from two transmitting stations at 40 kHz and 60 kHz by the Independent Administrative Institution Information and Communication Organization.

The standard radio wave is generally transmitted by a carrier wave by AM modulation, and when the amplitude at the time of non-modulation is 100%, the amplitude at the time of modulation is changed from about 25% to about 10% to represent the binary values of HIGH and LOW. Yes. The demodulated signal becomes a pulse signal with these two values. The standard radio wave transmits one bit every certain time, and one code is assigned to each bit.
However, the “bit” referred to here is a minimum unit of information sent by the standard radio wave, and is different from a bit when “digital value“ 0101 ”is 4 bits”, for example.

  The code in the standard radio wave is defined by the pulse width of the pulse signal, and there are a plurality of codes. In the case of Japanese standard radio waves, as shown in FIGS. 12 and 13, the three codes “0”, “1”, and “P” have pulse widths of 800 ms, 500 ms, and 200 ms, respectively. However, the definition of the pulse width and each code varies greatly depending on the transmitting station.

  As shown in Fig. 14, time information is assigned to each block in one cycle, and each block has a bit width of several bits. Have. Each bit of each block is assigned one of the codes “0”, “1”, and “P”. Information such as hours, minutes, and dates is expressed by a combination of these codes. Therefore, the time information of the standard radio wave is also called a time code. In the code, “P” is called a position marker, which does not indicate information such as time, but indicates a specific place in the period of the time code such as the beginning of one period of the time code or the beginning of each block. Is.

  Although the definition of the time code varies depending on the transmitting station, the time codes of many transmitting stations in the world are “0” and “1” assigned to each bit of time information other than the marker, and these two codes are used. The information of each block is expressed by binary system.

For example, in the case of Japanese standard radio waves, time information is represented by a method similar to a binary-coded decimal number (BCD). One bit is assigned to one second, and 0 to 59 bits are one time code period, that is, one minute is one time code period. Bits 1 to 8 are minute blocks, and the current minute is represented by adding the time information numerical values of the bits that have become “1”. For example, the codes from bit 1 to bit 8 are {“0”, “1”, “0”, “0”, “0”, “1”, “0”, “1”}
In this case, 20 + 4 + 1 = 25 [minutes].

[Description of code judgment]
Since the time code is defined as described above, codes such as “0”, “1”, and “P” can be determined by measuring the pulse width of the signal demodulated by the receiving means.
For example, the pulse width can be estimated by sampling the binarized signal at a constant period and dividing the number of HIGHs per second by the number of samplings.

In addition, since all different codes rise at the beginning of every second and fall after maintaining HIGH for a defined time, there is a section in which a specific code drink becomes HIGH for a certain section in one second. For example, in the case of Japanese standard radio time code, “0”, “1”, and “P” all start at 0 ms, “P” is 200 ms, “1” is 500 ms, and “0” is 800 ms. Because it falls
From 0ms to 200ms, "P", "1" and "0"
From 200ms to 500ms, “1” and “0”
“0” from 500 ms to 800 ms
Should be HIGH. It is possible to determine “0”, “1”, and “P” every second by determining HIGH and LOW for each section and combining the determination for each section. Further, an impossible combination can be determined as an error code.

[Evaluation of sensitivity]
A bit error rate (BER) is a typical reference for evaluating the sensitivity of the standard radio wave receiver using the code determination result. This is the number of bits in error during a certain time divided by the total number of bits. If 1 bit becomes an error in 100 bits,
1/100 = 0.01
BER is expressed as 0.01 or 1%. Since the time code has almost no superimposition property, it cannot be received when the BER becomes several percent.

  As described above, the reception sensitivity of the standard radio wave receiver largely depends on the accuracy of the pulse width. In other words, increasing the accuracy of the binarization of the demodulated signal is one of the important factors for improving the reception sensitivity of the standard radio wave receiver.

[Overview of conventional technology]
A technique for eliminating the influence of noise and the like included in the demodulated signal is also known. For example, a technique for avoiding noise generated on the upper side or the lower side of the demodulated signal by adjusting the threshold level when the demodulated signal is binarized to the lower side or the upper side is known (see Patent Document 1). .)

  In the prior art disclosed in Patent Document 1, the threshold level for binarizing the demodulated signal is switched from a standard level to a higher or lower threshold level by the transmitting station. The standard threshold is an intermediate level between the peak and the bottom of the demodulated signal.

JP 2007-139705 A (Page 15, FIGS. 20 to 22)

[Characteristics and problems of time code]
There is no redundancy in the time information sent by standard radio waves, except for the parity check for limited information of some transmitting stations, and there is a method for detecting erroneous codes and means for correcting them. Because there is a fundamental problem that there is no information source, there is no information source other than the signal received at that time, and the accuracy of code determination depends only on the characteristics of the demodulated signal or pulse signal. Yes. Further, in order to increase the reliability of the acquired information, it is necessary to receive a plurality of time codes and compare and correct the data of the same bits of the time code. As the reception environment gets worse, there is a problem that more data must be taken and the reception time becomes longer.

  The characteristics of the demodulated signal mainly depend on the electric field strength and the ratio of signal component to noise component (SNR). If the pulse rise position or pulse width on the time axis differs greatly from the transmitted original code due to a decrease in electric field strength or an increase in noise components, code determination and time information acquisition are performed accurately. However, it becomes the reception limit at that time.

[Specific problems of the prior art 1: Problems with threshold switching]
FIG. 8 is a diagram in which the threshold level and the part related to the description for avoiding noise in the waveform of the demodulated signal of the prior art shown in Patent Document 1 are rewritten without departing from the gist thereof. With respect to the waveform of the demodulated signal in FIG. 8, reference numerals 801 and 802 are lines that smoothly connect the upper and lower peaks of the demodulated signal, respectively, and the intermediate level 803 binarizes the demodulated signal. Is the threshold value. Reference numerals 804 and 805 denote noises appearing on the upper side and the lower side, respectively.

  As shown in FIG. 8, when the entire demodulated signal waveform is stable and the noise level is low, noise such as noise 804 and 805 can be easily avoided by setting the intermediate level of the demodulated signal waveform as a threshold value. Can do.

  In the case where one of the noises 804 and 805 grows to a noise that is applied to the intermediate level 803, the conventional technique 1 disclosed in Patent Document 1 avoids the noise by adjusting the threshold level to the upper side or the lower side. ing.

  This technology is based on the assumption that either the upper or lower noise is serious for a specific transmitting station, and the threshold level is set upward or downward in a certain direction depending on the transmitting station. It is to avoid noise by moving to.

  However, for a specific transmitting station, for example, in order to avoid noise appearing on the lower side, when the threshold level is raised above the intermediate level in advance, the threshold level is adjusted if the upper noise increases in the actual reception environment. As a result, the BER is rather deteriorated and the reception sensitivity is lowered. On the other hand, when it is assumed that noise at a certain transmitting station appears on the upper side, if the lower noise increases in an actual environment, the sensitivity may be deteriorated by adjusting the threshold level.

[Specific Problem of Conventional Technology 2: Problem of Threshold Level]
Hereinafter, the problem of the threshold level estimated from the prior art and the actual reception environment will be described. In an actual reception environment, particularly when the electric field strength is very low, the reception environment is easily affected, and the amplitude of the waveform of the demodulated signal continuously changes or the entire waveform fluctuates up and down. In such a situation, the threshold level is affected by these and deviates from an appropriate level, the pulse width of the digital signal after binarization becomes inaccurate, and error bits are likely to be generated in code determination.

  FIG. 9 shows the waveform of the demodulated signal when the amplitude of the demodulated signal waveform fluctuates. In this figure, if the upper peak level 801 follows fluctuations in amplitude, the signal 806 can be captured, but the noise 805 cannot be avoided. On the other hand, if the fluctuation of the amplitude is ignored and only a large signal is followed, the noise of 805 can be avoided, but the signal portion of 806 cannot be captured by the threshold value.

  FIG. 10 shows the waveform of the demodulated signal when periodic low-frequency spike noise is mixed. In this case, the lower peak level of 802 is pulled by spike-like noise, and the threshold level is further reduced to be lower than the appropriate level. As shown in FIG. 10, although the demodulated signal sufficiently reflects the time code, the pulse width of the time code may not be accurately reproduced due to the influence of noise.

  If the upper peak level is adjusted so as to avoid narrow-width noise as shown in Fig. 10, it becomes insensitive to narrow pulse peaks such as "P" in Japanese standard radio waves, and the pulse is accurately The width cannot be reproduced. There is a possibility that the “P” code of the Japanese standard radio wave may be mistakenly avoided, and in the worst case, there is a possibility that minute synchronization cannot be obtained. This becomes more prominent as the pulse width of the time code becomes narrower, and this problem is more pronounced in the case of a German DCF time code with “0” and “1” codes of 100 ms and 200 ms respectively. Become serious.

  In addition, when the waveform of the demodulated signal fluctuates as shown in FIG. 11, it is difficult to adjust the followability of the peak level, and it is difficult to set an appropriate threshold level.

  Such undesirable characteristics of the noise and the waveform of the demodulated signal are not specified by the time code or the transmission frequency of the transmitting station, but are generated in various ways depending on the combination of the reception environment and the characteristics of the receiving means. The effect is more pronounced if the field strength decreases or there is proximity noise with a frequency very close to the transmission frequency.Assuming only certain noise in advance is likely to generate error bits and errors. It becomes a factor of reception.

  As described above, in the prior art, the threshold value is determined by determining the amplitude, upper peak level, and lower peak level of the demodulated signal on the assumption that the demodulated signal is stable.

  The present invention solves the above-described problem. Even when the demodulated waveform becomes unstable due to the influence of a change in reception environment or noise, an appropriate threshold level is found, code determination is performed accurately, and an accurate time is determined. A standard radio wave receiver capable of performing information conversion and time correction is provided.

  In order to achieve the above object, the standard radio wave receiver of the present invention employs the following configuration.

A plurality of codes are represented by a plurality of rectangular pulse widths included in a predetermined cycle, and time information allocated to a predetermined bit is received and demodulated by receiving a standard radio wave including a time code defined by the plurality of codes. Receiving means for outputting a signal, a threshold value for converting the demodulated signal output from the receiving means into a digital signal, and a comparing means for outputting the digital signal;
Standard radio wave receiving apparatus having decoding means for decoding time code from digital signal, control means for extracting time information from output of decoding means and correcting time, and selection means for switching or adjusting threshold of comparison means In
The decoding means has first storage means, the control means has second storage means, and the decoding means stores the output of the comparison means in the first storage means, and the stored data The control means outputs the threshold value switching signal of the comparison means to the selection means, and the control means stores the output of the decoding means in the second storage means, and switches the threshold value of the comparison means based on the stored data. The signal is output to the selection means, the selection means switches the threshold value of the comparison means using either or both of the switching signal from the decoding means and the switching signal from the control means ,
The output data of the comparison means stored in the first storage means counts the number of counts that become HIGH by sampling, and determines based on an average value or an assumed range of the theoretical values in a predetermined period. The output data of the decoding means stored in the storage means is determined based on the same code consecutive appearance bit number of the time code or the appearance interval of the same code .

The comparison means has a plurality of comparators, each of the comparators has a plurality of independent threshold values, and outputs a separate digital signal to the decoding means by comparing the plurality of threshold values with each output from the reception means. It is characterized by doing.

  The comparison means having a plurality of threshold values switches the threshold values at a constant period.

  The demodulating signal output from the receiving means is input and receiving state determining means is provided for determining the state of the received standard radio wave. The selecting means outputs the reception state determining means and the first storage of the decoding means. The threshold value is switched based on the output data of the comparison means stored in the means and the output data of the decoding means stored in the second storage means of the control means.

  The demodulating signal output from the receiving means is input, and the transmitting station detecting means for detecting the station of the received standard radio wave is included. The selecting means outputs the output of the transmitting station detecting means and the first memory of the decoding means. The threshold value is switched based on the output data of the comparison means stored in the means and the output data of the decoding means stored in the second storage means of the control means.

  According to the present invention, even when the reliability of the received signal is reduced in an environment where the electric field strength is low and the SNR is low, it is possible to accurately determine the time code and correct the time correctly. There exists an effect that an apparatus is obtained.

  Exemplary embodiments of a standard radio wave receiver according to the present invention will be described below in detail with reference to the accompanying drawings.

[Configuration of standard radio wave receiver: FIGS. 1, 2, 3, and 4]
First, the configuration of a standard radio wave receiver according to an embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating a standard radio wave receiver according to the present invention, and FIGS. 2 to 4 are block diagrams illustrating modifications thereof. First, a basic configuration will be described with reference to FIG.
In FIG. 1, 100 is a receiving means, 200 is a comparing means, 300 is a decoding means, 301 is a first storage means, 400 is a control means, 401 is a second storage means, and 500 is a selection means.

The receiving means 100 receives the standard radio wave transmitted as an AM modulated wave from the transmitting station, captures the envelope of the AM modulated wave, demodulates it, and outputs it.
The comparing unit 200 compares the demodulated signal output from the receiving unit 100 with a plurality of threshold levels, and determines HIGH or LOW for each threshold. The comparison result is output as a digital signal. The decoding unit 300 performs code determination using the digital signal from the comparison unit 200.
The control unit 400 extracts time information based on the code determination result output from the decoding unit 300. The decoding unit 300 and the control unit 400 include a first storage unit 301 and a second storage unit 401 that are independent of each other.

[Variation 1 of standard radio wave receiver 1: Fig. 2]
Next, a configuration in which the comparison unit 200 has a plurality of comparators will be described with reference to FIG. In the same configuration, the same number is assigned. In FIG. 2, reference numeral 201 denotes comparison means having a plurality of comparators.
Each comparator in the comparison unit 201 has an independent threshold value, and outputs the determination made to the decode unit 300 independently.
Similar to the configuration of FIG. 1, the decoding unit 300 and the control unit 400 send an adjustment signal to the selection unit 500 from the results of the plurality of comparators, and the selection unit 500 adjusts the threshold value of each comparator.

[Modification 2 of standard radio wave receiver: Fig. 3]
Next, a configuration in which reception state determination means is added will be described with reference to FIG. In the same configuration, the same number is assigned. In FIG. 3, reference numeral 501 denotes reception determination means.
In the configuration of FIG. 3, the reception state determination unit 501 determines the intensity of received radio waves and the amount of noise in the reception unit 100, and outputs the result to the control unit 400. The control unit 400 combines the output of the reception state determination unit 501 and the output of the decoding unit 300 and sends a threshold switching signal to the selection unit 500.

[Modification 3 of standard radio wave receiver: Fig. 4]
Next, a configuration in which transmitting station detecting means is added will be described with reference to FIG. In the same configuration, the same number is assigned. In FIG. 4, reference numeral 502 denotes transmission station detection means.
In the configuration shown in FIG. 4, as in the configuration of FIG. 3, the transmission station detection unit 502 determines the transmission station from the signal received by the reception unit 100 and sends the result to the control unit 400. The control unit 400 combines the output of the transmission station detection unit 502 and the output of the decoding unit 300, and sends threshold switching to the selection unit 500.

[Description of receiving means: FIG. 5]
Next, the circuit configuration of the receiving means 100 will be described with reference to FIG. In FIG. 5, 101 is an antenna, 102 is a tuning circuit, 103 is an amplifier circuit, 104 is a filter circuit, 105 is a demodulation circuit, and 106 is an AGC control circuit. The frequency of the standard radio wave received by the antenna 101 is selected by the tuning circuit 102, the selected signal is amplified by the amplifier circuit 103, and noise is removed by the filter circuit 104. The demodulating circuit 105 demodulates the AM modulated wave and outputs it as a demodulated waveform reflecting a time code pulse. An AGC control circuit 106 adjusts the amplification factor of the amplifier circuit 103 according to the amplitude of the demodulated signal.

[Circuit Configuration for Adjusting Specific Threshold: FIGS. 6 and 7]
Next, a circuit for switching the threshold value will be described with reference to FIGS. These circuits are mounted on the comparison means 200 shown in FIG.
For the sake of explanation, FIG. 6 shows a circuit for switching between two threshold values as the simplest example.
In FIG. 6, reference numeral 601 denotes a comparator, and reference numerals 602 to 604 denote resistors R0 to R2. Reference numerals 605 and 606 are inferences. Reference numeral 607 denotes a ground potential line, and 608 denotes a power supply line. Reference numeral 609 denotes an input signal line, and reference numeral 610 denotes a comparator output.

  A resistor R0, a resistor R1, and a switch 605 are connected in series between the ground potential line 607 and the power supply line 608. A connection point between the resistor R0 and the resistor R1 is connected to the positive input terminal of the comparator 601. A resistor R2 and a switch 606 are connected in series between the positive input terminal and the power supply line 608. The input signal line 609 is connected to the negative input terminal of the comparator 601, and the output terminal of the comparator 601 is a comparator output 610.

  The switches 605 and 606 are operated by signals from the selection means 500 shown in FIGS. 1 to 4 to change the resistance voltage dividing ratio by switching between the resistors R1 and R2, and the comparison level input to the comparator 601 is switched. Yes.

The example shown in FIG. 7 is a modification of the example shown in FIG. 6 and has a configuration in which the threshold level is adjusted steplessly by a variable resistor. In FIG. 7, VR is a variable resistor. In the same configuration, the same number is assigned.
The variable resistor VR changes the resistance voltage division ratio with the resistor R0 and switches the comparison level input to the comparator 601.

[Explanation of threshold value switching by decoding means: FIGS. 1 to 5]
Next, switching of threshold values by the decoding unit 300 in the standard radio wave receiver of the present invention will be described. The description will be made with reference to FIGS. 1 to 5 as appropriate. Except for specific setting values, the switching method is common to all transmitting stations, so here, an example of Japanese standard radio waves will be described.

First, a numerical value that serves as a reference when adjusting the threshold value using the output of the comparison unit 200 stored in the first storage unit 301 of the decoding unit 300 will be described.
When the binarized digital signal is sampled and the ratio of the number of times HIGH is counted in a certain period of time to the total number of sampling times is RH,
RH = NH / N
It becomes. Here, NH is the HIGH count number per unit time, and N is the total sampling number per unit time.

  As the simplest example, RH in 1 second can be easily obtained from the pulse width of each code. For example, since “P” has a pulse width of 200 ms, for example, when the sampling frequency is 100 Hz, HIGH is counted 20 times from 0 ms in an extremely good reception environment. Since the total number of samplings per second is 100, the RH per second when the “P” code appears is 20/100 = 0.2. Similarly, “1” is 0.5, and “0” is 0.8.

  As an example, FIG. 15 shows the change in the theoretical value of RH calculated by simulation of the time code at 2:22:02 on June 6, 2007 (Wednesday). Since the RH when the unit time is 1 second changes directly according to the code of every second, it greatly changes between 0.2 and 0.8 as shown in FIG.

The fluctuation of RH is moderated by taking a long unit time. For example, when “P” and “0” appear within 2 seconds, HI = 100/200 = 0.5 because 20 + 80 = 100 times are counted in an ideal environment. Based on this, when generalizing the equation for obtaining RH in a certain number of seconds of 2 seconds or more, RH = (N0 * 0.8 + N1 * 0.5 + NP * 0.2) / N
It becomes. Here, N0, N1, and NP are the numbers of appearances of “0”, “1”, and “P” in the unit time, respectively.

  FIG. 16 shows the change in the theoretical value of RH of the time code from 2:00 on June 6, 2007 (Wednesday), calculated similarly by simulation. Here, the unit time is 1 minute, and the range of fluctuation of RH is approximately 0.03. In this way, the longer the unit time, the more the bias of the appearance code is eliminated, and the fluctuation of RH becomes more gradual.

Next, how RH changes between 2000 and 2099, which is assumed for standard radio waves, will be described. Since the time axis is long, the unit time is 1 minute for convenience. FIG. 17 shows the change in RH over one year in the year 2000.
RH varies approximately in the range of 0.64 to 0.71. On the other hand, FIG. 18 shows the change of RH in one year in the year 2077. RH varies in the range of approximately 0.61 to 0.68.

Except for special conditions such as when there is a leap second, the change in the time code other than the year code year block is common in the year 2000 and the year 2077 throughout the year.
With regard to the year code year block, the year 2000 is all "0", and the year 2007 is a year in which "1" appears in 6 bits and the number of bits in the year block is "1".
Since “1” has a narrower pulse width than “0”, the year with the highest “1” is the year with the lowest RH.
That is, between the year 2000 and the year 2099, the theoretical value of RH always exists between the upper limit of the graph of the year 2000 in FIG. 17 and the lower limit of the graph of the year 2077 in FIG. The range is approximately 0.61 to 0.71 as described above, and the width is approximately 0.1.

As shown in FIG. 12, since the demodulated signal is not a perfect rectangular wave, the closer to the top of the waveform, the closer to the peak of the peak and the narrower the pulse width of the output digital signal.
However, if the threshold is set to an ideal level in a receivable environment, the above RH enters a theoretically possible range.
If the actually measured RH is out of this range, the RH can be adjusted to an appropriate value and the accuracy of code determination can be improved by adjusting the threshold value to correct it.

  An example of a method for controlling the threshold level based on this will be described below. RH = 0.65 is set as a reference value as an average level within the range of theoretical values of RH. When the actual measurement value obtained from the data of the comparison means output is less than 0.65, the threshold value is lowered to make HIGH more likely to be output. Conversely, if it exceeds 0.65, the threshold value is increased to make it easier to output LOW.

  FIGS. 19 and 20 respectively show changes in RH and BER when RH is calculated every 20 seconds using actually measured data, and determination of the RH and adjustment of the threshold are performed. Starting from a state where the initial threshold level is higher than the appropriate value. Therefore, RH is low and BER is high. However, after that, the threshold level is gradually adjusted to an appropriate level, and the BER is lowered.

  Since the possible range of RH in the ideal condition is known for each transmitting station or each time code, if the measured RH deviates greatly from this, it is determined that the environment is not receivable, and a signal such as a reception error is displayed. It can be sent to the control means, and the reception operation can be immediately terminated to prevent the reception state from being unnecessarily kept for a long time, thereby reducing power consumption and the like.

  In addition to the threshold adjustment as described above, as an advantage of processing the data stored in the first storage unit 301 of the decoding unit 300, it is possible to provide a simple filter function. . If LOW occurs for a very short time when HIGH is continuously counted, it can be judged that this is likely to be noise, so it is possible to correct this LOW to HIGH. is there.

[Explanation of threshold switching by control means]
Next, a method of storing the result of the code determination performed by the decoding unit 300 in the second storage unit 401 of the control unit 400 and switching the threshold based on the stored data will be described. Again, except for specific setting values, the switching method is common to all transmitting stations, so an example of Japanese standard radio waves will be described.

Several conditions can be set from the definition of the time code for the result of the code determination that is output continuously every second. A simple condition is the number of bits in which the same code appears continuously. The number of bits that each code can appear in succession is (Condition 1): “P” is 2 bits at most,
(Condition 2): “1” is a maximum of 3 bits.
(Condition 3): “0” is a maximum of 9 bits.
It is. For “P”, the following conditions are also added.
(Condition 4a): The interval between “P” and “P” is smaller than 9 bits or 10 bits (Condition 4b): The interval between “P” and “P” is larger than 9 bits or 10 bits
(However, the last "P" code at the end and the beginning of the time code are excluded)
It is also possible to set more complicated conditions from the prescribed pattern of time code.

As shown in FIG. 12, since the demodulated signal is not a perfect rectangular wave, the closer to the top of the waveform, the closer to the peak of the peak and the narrower the pulse width of the output digital signal.
Therefore, if the threshold level is too high, “P” and “1” are likely to appear, and the above limit on the number of consecutive bits may be exceeded. In this case, the threshold level is lowered. On the other hand, when “0” appears continuously, it is estimated that the threshold level is below the appropriate threshold level, so the threshold level is raised.

[When the comparison means has multiple comparators]
Even when the comparison means 200 has a plurality of comparators, each comparator has a plurality of threshold values or an adjustable threshold value as in the case described above. The threshold value of each comparator is output independently to the decoding unit 300, and the decoding unit 300 performs code determination based on these data. The decoding unit 300 sends a signal for switching the threshold value for each comparator to the selection unit, and the selection unit 500 switches the threshold value by combining these and the switching signal sent from the control unit 400.

[Reception status judgment means]
When the reception state determination unit 501 can read the intensity of standard radio waves received from the reception unit 100, the amount of noise, etc., as in the configuration of FIG. 3, this information is sent to the control unit 400, The control unit 400 determines the threshold value switching together with this and sends a switching signal to the selection unit 500.

[Transmission station detection means]
When the transmitting station detecting unit 502 can determine the transmitting station of the standard radio wave received by the receiving unit 100 as in the configuration of FIG. 4, this information is sent to the control unit 400, and the control unit 400 sends the information to the transmitting station. At the same time, a switching signal is sent to the selection means.

[flowchart]
Actually, the threshold value can be switched using both the RH obtained from the HIGH and LOW data in the decoding means and the result of the code determination stored in the second storage means 401 of the control means 400. Hereinafter, the threshold value switching process in the selection unit 500 will be described with reference to the flowchart of FIG.

After starting reception, set the transmitting station. If the transmitting station is known, the transmitting station is set. Otherwise, an initial setting station is set (S1).
Next, an RH reference value and a threshold level are set according to the transmitting station (S2). If reception state information is obtained, a correction value is added to these (S3).
Thereafter, the threshold value is set to an intermediate level (S4), and the decoding unit 300 and the control unit 400 acquire and store data for a unit time.
From the obtained data, the consistency of RH, decoding result, setting transmission station, etc. is confirmed (S5). Here, since it is unclear whether the threshold level is appropriate, the consistency check is given a certain range. If it is determined that the transmission station setting is appropriate, the acquired data is compared with a reference value (S6 to S10).

When (Condition 1), (Condition 2), and (Condition 4a) are not satisfied (S11), there is a high possibility that the threshold is too high. In this case, the value of RH is further compared with the reference value, and RH is the reference. If it is lower than the value, the threshold is lowered (S12).

  If (Condition 3) and (Condition 4b) are not satisfied (S13), there is a high possibility that the threshold is too low. In this case, the value of RH is further compared with the reference value, and if RH is higher than the reference value, the threshold is set. (S12).

  Even when (Condition 1) to (Condition 4b) are satisfied (S14), if the RH is out of the reference range, the threshold is increased or decreased to further increase the accuracy of code determination (S15, S16).

  Thereafter, when the threshold is fixed (S17), the switching process is terminated, and when the adjustment is dynamically performed, the process returns to the unit time data acquisition and the above process is repeated.

[Decoding means when switching at a constant frequency]
It is also possible to perform more advanced threshold adjustment by using a plurality of thresholds simultaneously. When data obtained by sampling a digital signal at 100 Hz is necessary for code determination in the decoding means 300, the threshold is switched at a frequency faster than this sampling frequency. The switching frequency can also be determined as follows using the sampling frequency and the number of threshold values to be switched.
(Threshold switching frequency) = (Required sampling frequency) × (Number of thresholds)

FIG. 21 is a diagram schematically showing threshold switching. The starting point of the arrow in FIG. 21 indicates the threshold level used at that time, and the HIGH and LOW determination results are indicated in the direction of the arrow.
First, at 0 ms, the threshold 0 is compared with the demodulated waveform to determine HIGH and LOW. Next, the determination is made based on the threshold 1 at 2.5 ms, the threshold 2 at 5.0 ms, and the threshold 3 at 7.5 ms. Then, the determination is performed using the threshold 0 again in 10 ms. Thus, each threshold value is determined every 10 ms, that is, at 100 Hz.

The comparison unit 200 outputs the determination of each threshold value directly and continuously, and the decoding unit 300 performs sampling at the same frequency as the switching frequency and stores data for each threshold value. In the example of FIG. 21, the comparison means is HLLLHHHLHH.
Is output continuously. The decoding means 300 performs sampling at 400 Hz so as to synchronize with the switching frequency, and data group 0: HHH. . .
Data County 1: LHH. . .
Data County 2: LH. . .
Data County 3: LL. . .
As described above, data is stored for each threshold.

FIG. 23 shows a table in which the determination results are changed according to threshold values using an example of the actual measurement results. In FIG. 23, the threshold switching frequency is 400 Hz, and RH below the table is the result for 20 seconds, but the table is omitted. As the threshold level is lower, it is easier to determine HIGH, and therefore RH tends to be higher. Normally, as the threshold level increases, RH decreases continuously, and this tendency can also be seen in the table shown in FIG.
In the table shown in FIG. 23, the threshold value 1 has a value of RH = 0.65, and it is estimated from the results of FIGS. 17 and 18 that the threshold value 1 is the most appropriate threshold level. By performing code determination using the data of the threshold value 1, more accurate code determination can be performed.

  By storing data for each threshold, it is possible to search for the most appropriate threshold every fixed time such as 20 seconds as in the above example, and use the data of the threshold at any time. This is effective when the demodulated signal fluctuates because the threshold value is switched at any time.

Also, a certain time from the start of reception is set as a stable time, and the threshold is switched at a constant frequency during this period. The most appropriate threshold level is determined using the result of this stable time, and is fixed to this threshold level during the subsequent reception operation. It is also possible to use it. Even in this case, since the data during the stable time can be used without being discarded, the reception time can be shortened.
In a normal method in which the threshold value is not switched at a fixed period, the threshold value is switched after the value of RH is obtained, and therefore the output result based on the appropriate threshold value is effective after the switching. In other words, the reliability of data while adjusting the threshold value is lowered.

[When switching at a constant frequency]
As described above, HIGH and LOW data stored for each threshold can be subjected to code determination for each data group. The table shown in FIG. 24 is an example of an actual measurement result obtained by performing code determination in the decoding unit 300 for each data group obtained from each threshold value.

  In the table shown in FIG. 24, in the data group with the threshold 0, “0” is continuous for 10 bits or more, and the interval between “P” and “P” is 12 bbit or more, so the threshold is too low. I guess that. In addition, it is easily estimated that the threshold value is too high in the data group of the threshold value 3 because “P” appears too much. In the data group of the threshold value 2, the interval between “P” and “P” is 3 bits or 7 bits, and it can be estimated that the threshold value is too high. Only the data group of threshold value 1 satisfies all of the above (condition 1) to (condition 4b), and it can be estimated that threshold value 1 is the most appropriate threshold level.

  Similar to the threshold value switching by the decoding means 300, it is possible to find an appropriate threshold value at regular intervals and use the data as needed, or use only the data group of the threshold value after finding an appropriate threshold level. is there.

As described above, according to the embodiment of the present invention, when the reception environment is deteriorated and the demodulated signal output from the standard radio wave receiving means 100 becomes unstable, accurate code determination is performed by appropriately switching the threshold value. And accurate time information can be provided.
In addition, even when receiving multiple time codes in order to improve the reliability of acquired information, it is possible to compare and correct with a small amount of data based on accurate code determination results, reducing reception time and reducing power consumption. be able to.

  In the embodiment described above, the standard radio wave receiving apparatus of the present invention is an example of a radio wave correction watch. Of course, the standard radio wave receiver of the present invention is not limited to this, and portable information such as a mobile phone, a PDA (Personal Digital Assistant), a personal computer, a portable music player, etc., which incorporates a standard radio wave receiver. It may be a terminal device.

  Since the standard radio wave receiver of the present invention can accurately provide time information even if the reception state deteriorates, it is away from a small radio wave correction watch such as a wrist watch with many physical restrictions on the antenna and the receiving circuit, or from an indoor window. This is suitable for a radio-controlled watch at a certain place.

It is a block diagram explaining the structure of the standard radio wave receiver of this invention. It is a block diagram explaining the example in which the comparison means has a some comparator in the structure of the standard radio wave receiver of this invention. It is a block diagram explaining the example which has a reception status judgment means in the structure of the standard radio wave receiver of this invention. It is a block diagram explaining the example which has a transmission station detection means in the structure of the standard radio wave receiver of this invention. It is a block diagram explaining the circuit structure of the receiving means of the standard wave receiver of this invention. It is a circuit diagram of the circuit which switches a threshold value. It is a circuit diagram of the circuit which switches a threshold value steplessly. It is a figure explaining a demodulated signal and a threshold value. It is a figure explaining a demodulated signal and a threshold value. It is a figure explaining a demodulated signal and a threshold value. It is a figure explaining a demodulated signal and a threshold value. It is a figure explaining a demodulated signal and a binarized digital signal. It is a figure explaining "0", "1", and "P" code of Japanese standard radio waves. It is a figure explaining the time code of Japanese standard radio waves. It is a figure which shows the change of RH of unit time 1 second. It is a figure which shows the change of RH per unit time. It is a figure which shows the change of RH of 2000 AD. It is a figure which shows the change of RH of the year 2077. It is a figure which shows the change of RH when a threshold value is adjusted. It is a figure which shows the change of BER when a threshold value is adjusted. It is a figure explaining the threshold value and determination result at the time of switching a threshold value with a fixed period. It is a flowchart explaining a threshold value switching process. It is a table | surface explaining a mode that the determination result was changed according to threshold value. It is a chart explaining the actual measurement result which carried out code judgment according to the data group obtained from each threshold value.

Explanation of symbols

100 receiving means 200, 201 comparing means 300 decoding means 301 first storage means 400 control means 401 second storage means 500 selection means 501 reception state determination means 502 transmitting station detection means

Claims (5)

A plurality of codes are represented by a plurality of rectangular pulse widths included in a predetermined cycle, and time information assigned to predetermined bits is received and demodulated including a standard radio wave including a time code defined by the plurality of codes. Receiving means for outputting a demodulated signal;
A comparator having a threshold for converting the demodulated signal output from the receiving unit into a digital signal, and outputting a digital signal;
Decoding means for decoding the time code from the digital signal;
Control means for extracting time information from the decoding means output and correcting the time;
Selection means for switching or adjusting the threshold value of the comparison means;
In a standard radio wave receiver having
The decoding means has first storage means,
The control means has second storage means,
The decoding means stores the output of the comparison means in the first storage means, and outputs a threshold switching signal of the comparison means to the selection means based on the stored data.
The control means stores the output of the decoding means in the second storage means, and outputs a threshold switching signal of the comparison means to the selection means based on the stored data,
The selection means includes
A standard radio wave receiver characterized by switching the threshold value of the comparison means using either or both of the switching signal from the decoding means and the switching signal from the control means ,
The output data of the comparison means stored in the first storage means counts the count number that becomes HIGH by sampling, and determines the average value or the assumed range of the theoretical value in a predetermined period as a reference,
The output data of the decoding means stored in the second storage means is determined based on the same code consecutive appearance bit number of the time code, or the appearance interval of the same code,
A standard radio wave receiver characterized in that The comparison means has a plurality of comparators, and each comparator has a plurality of independent thresholds,
2. The standard radio wave receiving apparatus according to claim 1, wherein the standard radio wave receiving apparatus outputs the independent digital signal to the decoding means by comparing the plurality of threshold values with the output from the receiving means.   The standard radio wave receiving apparatus according to claim 2, wherein the comparison unit having the plurality of thresholds switches the thresholds at a constant period. Receiving the demodulated signal output from the receiving means, and having a receiving state judging means for judging the state of the received standard radio wave,
The selection means includes
The output of the reception state judging means, the output data of the comparing means stored in the first storage means of the decoding means, and the decoding means stored in the second storage means of the control means. 4. The standard radio wave receiving apparatus according to claim 1, wherein the threshold value is switched based on output data. Inputting the demodulated signal output from the receiving means, and having a transmitting station detecting means for detecting the station of the received standard radio wave,
The selection means includes
The output of the transmitting station detection means, the output data of the comparison means stored in the first storage means of the decoding means, and the output of the decoding means stored in the second storage means of the control means The standard radio wave receiver according to any one of claims 1 to 3, wherein the threshold value is switched based on the data.

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