Patent Application
20080049558
Preferred embodiments of the present invention are described below with reference to the accompanying figures.
A radio-controlled timepiece according to a first embodiment of the invention is described below.
As shown in
The microprocessor 2 has a reception processor 21, an oscillation circuit 22 for outputting a reference clock, a frequency divider 23, and a external waveform discrimination standard setting unit 24. The reception processor 21 outputs a control signal to the reception circuit 4 and receives the time code signal demodulated by the demodulation circuit 5. The frequency divider 23 frequency divides the reference clock output from the oscillation circuit 22 and supplies the clock signal to the reception processor 21. The external waveform discrimination standard setting unit 24 enables externally setting the waveform discrimination standard.
The reception processor 21 has a sampling unit 211, a signal width detector 212, a waveform discrimination standard storage unit 213, a selector 214, a waveform discriminator 215, a time information convertor 216, a timekeeping unit 217, and a display 218.
The sampling unit 211 samples the time code signal demodulated by the demodulation circuit 5. This embodiment of the invention uses a 64-Hz sampling circuit for sampling.
The signal width detector 212 measures the signal width between the falling edge and the rising edge of the time code signal sampled by the sampling unit 211, and thus measures the LOW signal width. This embodiment of the invention measures the LOW signal width in order to discriminate the codes in the German standard time signal DCF77. Note that the M code has a LOW signal width of 0 ms.
The waveform discrimination standard storage unit 213 stores the waveform discrimination standards for discriminating the waveform of the time code signal.
In this aspect of the invention the waveform discrimination standard storage unit 213 therefore stores waveform discrimination standards I to III each defining plural discrimination periods. The width or the starting position, or both the width and the starting position, is different in each of the discrimination periods. Each discrimination period includes the timing at which the signal level of the waveform of the pulse denoting a particular code value changes in the German standard time signal.
In the German standard time signal a 0 pulse has a LOW signal width of 100 ms, a 1 pulse has a LOW signal width of 200 ms, and two discrimination periods A and B are provided. Period A is the period containing the rising edge of the 0 pulse, and period B is the period containing the rising edge of the 1 pulse.
The relationship between the discrimination periods in waveform discrimination standards I to III and the codes of the German standard time signal is described next with reference to
As described above the German standard time signal transmits one code per second, and transmits one frame per minute. Each code pulse starts from the falling edge, that is, from the point where the time code signal goes from HIGH to LOW.
Therefore, when the sampling unit 211 samples the time code signal referenced to the starting position of the pulse wave of the code transmitted each second (sample 0), samples 0 to 7 are LOW in the pulse waveform of the 0 code because the pulse remains LOW for 100 ms, and samples 0 to 14 are LOW in the pulse waveform of the 1 code because the pulse remains LOW for 200 ms.
The sampling unit 211 operates at a 64-Hz sampling frequency, and the sampling interval of the time code signal is therefore approximately 15.6 ms.
Note that samples 0 to 63 are all HIGH for the M code.
The discrimination periods are set to periods including the position where the time code signal goes from LOW to HIGH. Period A in waveform discrimination standard I is therefore set to samples 1 to 8 because the timing at which the 0 pulse signal level changes is sample 7, and period B in waveform discrimination standard I is set to samples 9 to 16 because the timing at which the signal level of the 1 pulse changes is sample 14.
Period A in waveform discrimination standard II is samples 1 to 9, and thus changes the width of period A in waveform discrimination standard I. Period B in waveform discrimination standard II is samples 10 to 17, and thus changes the width of period A in waveform discrimination standard I.
The discrimination period for detecting the M code is samples 1 to 62 in waveform discrimination standards I to III.
The error code is output by the waveform discriminator 215 when a 0, 1, or M is not detected, and a discrimination period is therefore not set for error code detection.
The selector 214 selects one of the waveform discrimination standards from among the waveform discrimination standards I to III stored in the waveform discrimination standard storage unit 213.
The waveform discriminator 215 discriminates the waveform of the time code signal sampled by the sampling unit 211 based on the waveform discrimination standard selected by the selector 214, and outputs the corresponding codes.
The time information convertor 216 converts the code output from the waveform discriminator 215 to time information.
The timekeeping unit 217 keeps time based on the reference clock generated by the oscillation circuit 22, and adjusts the time based on the information output by the time information convertor 216.
The display 218 then displays the time kept by the timekeeping unit 217.
The method of changing the waveform discrimination standard of the radio-controlled timepiece 1 is described next.
As shown in
When the waveform discrimination standard changing process is started, the reference signal output step S1 outputs a reference signal from an external device (not shown in the figure).
This aspect of the invention outputs a reference signal that repeats the 0 pulse of the German standard time signal.
In the reference signal reception step S2 the reception circuit 4 then receives the reference signal through the antenna 3 based on the control signal output from the microprocessor 2.
In the reference signal demodulation step S3 the demodulation circuit 5 demodulates the reference signal received by the reception circuit 4 to the time code signal. This signal resulting from demodulating the reference signal to the time code signal is referred to herein as the “demodulated reference signal.”
In the signal width detection step S4 the signal width detector 212 measures the LOW signal width in the demodulated reference signal, and outputs the detected signal width to an external device (not shown in the figure).
Instead of using the signal width detector 212, this signal width detection step S4 could detect the LOW signal width in the demodulated reference signal output by the demodulation circuit 5 directly using an external pulse width measuring device.
In the waveform discrimination standard changing step S5 a worker or manufacturing device changes the waveform discrimination standard according to the LOW signal width in the demodulated reference signal measured by the signal width detector 212.
This embodiment of the invention describes using a method of changing the waveform discrimination standard by changing the jumper switch 6 connection by way of example.
As shown in
The external waveform discrimination standard setting unit 24 first determines if the jumper switch 6 is connected to pin K1 (S51) If the jumper switch 6 is connected to pin K1, the external waveform discrimination standard setting unit 24 selects waveform discrimination standard I (S52).
If the jumper switch 6 is not connected to K1, the external waveform discrimination standard setting unit 24 determines if the jumper switch 6 is connected to pin K2 (S53). If the jumper switch 6 is connected to pin K2, the external waveform discrimination standard setting unit 24 selects waveform discrimination standard II (S54).
If the jumper switch 6 is not connected to pin K2, the external waveform discrimination standard setting unit 24 sets waveform discrimination standard III (SS5).
The external waveform discrimination standard changing means in this embodiment of the invention includes the signal width detector 212, the waveform discrimination standard storage unit 213, the selector 214, and the external waveform discrimination standard setting unit 24.
When the waveform discrimination standard is externally set by the external waveform discrimination standard setting unit 24, the selector 214 selects the waveform discrimination standard set by the external waveform discrimination standard setting unit 24.
The method whereby the waveform discriminator 215 discriminates the waveform of the demodulated signal based on the waveform discrimination standard and outputs the corresponding codes when the radio-controlled timepiece 1 in this embodiment of the invention is used is described next.
The waveform discriminator 215 identifies the period in which the time code signal rises, or more specifically detects the sample number of the sample that goes from LOW to HIGH.
As shown in
If the sample is not in period A, the waveform discriminator 215 determines if the sample number of the time code signal rise is in period B (S13). If the sample is in period B, the waveform discriminator 215 outputs a 1 (S14).
If the sample is not in period B, the waveform discriminator 215 determines if the time code signal rise is code M (S15).
More specifically, the discrimination period for the M code is samples 1 to 62, and the waveform discriminator 215 therefore determines if the sampled values are all HIGH throughout this period. If all sampled values are HIGH, the waveform discriminator 215 outputs the M code (S16).
If the samples are not all HIGH, and the code is therefore not a 1, 0, or M, the waveform discriminator 215 outputs the error code (S17).
If the signal width of the demodulated reference signal detected by the signal width detector 212 is 125 ms, for example, the signal rise is detected at sample 8. When the selector 214 then selects the waveform discrimination standard I, period A is samples 1 to 8 and the effects of the field strength and S/N ratio of the standard time signal cause the rise in the time code signal to change to sample 9, for example, the waveform discrimination process will not operate correctly.
In this case the jumper switch 6 is connected to pin K2 so that the selector 214 selects waveform discrimination standard II. This changes period A to samples 1 to 9 and the waveform discrimination process operates correctly even if affected by the field strength and S/N ratio of the standard time signal.
The benefits of a radio-controlled timepiece 1 according to this aspect of the invention are described below.
(1) The radio-controlled timepiece 1 has a waveform discrimination standard changing means. The selector 214 can therefore select the appropriate waveform discrimination standard from among plural waveform discrimination standards stored in the waveform discrimination standard storage unit 213. The waveform discriminator 215 can therefore discriminate the waveforms of the demodulated signal based on the waveform discrimination standard selected by the selector 214, and the waveform discrimination process can operate correctly even when affected by the field strength and S/N ratio of the standard time signal.
(2) Because the waveform discrimination process operates accurately, fewer error codes are output, the reception time is shortened, and power consumption is reduced.
(3) A reference signal repeating the 0 pulse wave is output in the reference signal output step, the reference signal is received in the reference signal reception step, and the reference signal demodulation step demodulates the reference signal and outputs a demodulated reference signal. As a result, the waveform discrimination standard can be changed in the factory using a precise reference signal with sufficient signal strength and no noise. Change in the signal width caused by variations during the manufacture of the radio-controlled timepiece 1 can therefore be accurately detected, and the waveform discrimination standard can be reliably set to account for detected deviations introduced in the manufacturing process.
A radio-controlled timepiece according to a second embodiment of the invention is described below.
Note that like parts in this and first embodiment are identified by like reference numerals, and further description thereof is omitted.
The radio-controlled timepiece 1 according to the first embodiment changes the waveform discrimination standard by causing the reception circuit 4 to receive a reference signal that repeats a specific code in the standard time signal and changes the connection of the jumper switch 6 according to the signal width of the demodulated reference signal measured by the signal width detector 212.
The radio-controlled timepiece 1 according to this embodiment of the invention differs from the first embodiment in that the reception circuit 4 receives a long-wave standard time signal and the selector 214 automatically changes the waveform discrimination standard according to the signal width of the demodulated signal measured by the signal width detector 212 as shown in
The waveform discrimination standard changing means in this embodiment of the invention includes the signal width detector 212, the waveform discrimination standard storage unit 213, and the selector 214.
The radio-controlled timepiece 1 according to this aspect of the invention starts an automatic waveform discrimination standard changing process at the preset time for receiving the standard time signal or when the user operates the radio-controlled timepiece 1 to unconditionally receive the standard time signal.
When this automatic waveform discrimination standard changing process starts the reception circuit 4 receives the standard time signal through the antenna 3 based on a control signal output from the microprocessor 2 in the standard time signal reception step S21.
The demodulation circuit 5 then demodulates the standard time signal received by the reception circuit 4 to the time code signal in the standard time signal demodulation step S22.
In the signal width detection step S23 the signal width detector 212 measures the LOW signal width of a 0 pulse at least once. In this embodiment of the invention the signal width detector 212 measures the LOW signal width five times.
The signal width detector 212 calculates the LOW signal width by counting the number of consecutive samples that are LOW in the demodulated signal.
The signal width detector 212 first measures the signal width of the demodulated signal (S231), and then determines if the result is less than or equal to 140 ms (S232). The German standard time signal includes 1, 0, and M codes, and one code is transmitted every second. If the measured LOW signal width is greater than 140 ms, the code is not a 0, and the signal width of the demodulated signal is measured in the next code (S231).
If the result is less than or equal to 140 ms, a 0 pulse is detected and the microprocessor 2 stores the result in memory (not shown in the figure) (S233).
The signal width detector 212 then determines if a 0 pulse is detected five times consecutively (S234). If not, the signal width of the demodulated signal for the next code is measured (S231).
If five 0s are detected, the selector 214 determines the most frequent result in the measured signal widths output by the signal width detector 212 in the waveform discrimination standard changing step S24. If the results are 109 ms, 125 ms, 109 ms, 93 ms, and 109 ms, for example, the 109 ms result is most frequent with a count of 3, and the selector 214 detects a signal width of 109 ms.
The selector 214 then detects if the detected result is less than or equal to 93 ms (S242). If the detected result is less than or equal to 93 ms, the selector 214 selects waveform discrimination standard I (S243).
If the result is greater than 93 ms, the selector 214 determines if the detected result is less than or equal to 125 ms (S244). If the detected result is less than or equal to 125 ms, the selector 214 selects waveform discrimination standard II (S245).
If the detected result is greater than 125 ms, the selector 214 selects waveform discrimination standard III (S246).
When the waveform discrimination standard is selected by the selector 214, the radio-controlled timepiece 1 ends the automatic waveform discrimination standard changing process, executes the reception using the selected waveform discrimination standard, and adjusts the time based on the received time information.
This embodiment of the invention affords the same benefits as benefits (1) and (2) of the first embodiment described above.
In addition, the waveform discrimination standard is changed automatically by causing the reception circuit 4 to receive the standard time signal when the radio-controlled timepiece is used. As a result, the waveform discrimination process returns accurate results even if the signal width of the code pulses varies due to the effects of the field strength and S/N ratio of the standard time signal, temperature fluctuations, or aging.
Furthermore, the signal width detector 212 measures the signal width of the demodulated signal five times, and the selector 214 changes the waveform discrimination standard based on the most frequently detected signal width. The effects of measurement error can thus be suppressed and the waveform discrimination standard can be changed based on precise measurements.
The production efficiency of the radio-controlled timepiece 1 is also improved because the waveform discrimination standard does not need to be adjusting when manufacturing the radio—controlled timepiece 1.
The invention is not limited to the foregoing embodiments and can modified and improved in many ways within the scope of the accompanying claims by one with ordinary skill in the related art.
For example, the invention is described herein using the German standard time signal DCF77 by way of example, but the invention can also be used with the standard time signals transmitted in other countries. More specifically, the invention can be used with any long-wave standard time signal containing time information, and can set the waveform discrimination standard according to the codes in the appropriate standard time signal.
The waveform of the 0 pulse is used as the reference signal in the foregoing embodiments, but the waveform of the 1 pulse can be used instead. More specifically, any signal that can be used as a reference for changing the waveform discrimination standard can be used.
The signal width detector 212 measures the LOW signal width of the demodulated reference signal in the foregoing embodiments, but the HIGH signal width can be measured instead. More specifically, it is only necessary to be able to change the waveform discrimination standard based on the measurement.
The falling edge in the time code signal, that is, the point where the time code signal goes from HIGH to LOW, is used as the reference position in the foregoing embodiments, but the invention is not so limited. More specifically, any place where the time code signal switches between HIGH and LOW due to the arrangement of the demodulation circuit, or the rising edge, that is, the point where the time code signal goes from LOW to HIGH, depending upon the type of standard time signal, can be used. More specifically, the reference position can be the starting point of any pulse waveform for a code that is transmitted once per second.
A plurality of discrimination periods in which the signal level of the waveform changes according to the code are defined in the waveform discrimination standard, but the invention is not so limited. The plural discrimination periods can be set to any part where the signal level changes according to the code, and other waveform discrimination standards can be used. More specifically, any standard that enables identifying the waveforms of the demodulated signal and outputting the correct corresponding code can be used.
The waveform discrimination standard storage unit 213 stores waveform discrimination standards I to III above, but a different number of waveform discrimination standards can be stored. More particularly, any number of waveform discrimination standards that enables changing the waveform discrimination standard can be stored.
Furthermore, discrimination periods are provided for the waveform discrimination standard as shown in
The waveform discrimination standard is changed by the selector 214 selecting one waveform discrimination standard from among the plural waveform discrimination standards stored in the waveform discrimination standard storage unit 213, but the waveform discrimination standard can be changed by calculating an equation based on the demodulated reference signal. More particularly, any method that enables changing the waveform discrimination standard according to a variable signal width can be used.
The radio-controlled timepiece 1 according to the first embodiment of the invention changes the waveform discrimination standard as a result of the reception circuit 4 receiving a reference signal that repeats a particular code in the standard time signal, and then changing the connection of the jumper switch 6 according to the signal width of the demodulated reference signal measured by the signal width detector 212, but the selector 214 can automatically change the waveform discrimination standard according the signal width of the demodulated reference signal measured by the signal width detector 212.
The radio-controlled timepiece 1 according to the second embodiment of the invention executes an automatic waveform discrimination standard changing process during the standard time signal reception process at preset time for receiving the standard time signal or the user forces the radio-controlled timepiece 1 to receive the standard time signal. The automatic waveform discrimination standard changing process can be executed every time the standard time signal is received, or every n-times the standard time signal is received.
The automatic waveform discrimination standard changing process can also be executed during the manufacturing process.
The signal width detector 212 measures the LOW signal width five times in the foregoing embodiments, but can measure the signal width only once or any number of times that enables changing the waveform discrimination standard automatically based on the measured signal width. The effect of measurement errors decreases as the measurement count increases, and precise measurements can therefore be achieved, but the number of measurements is preferably set according to the performance of the sampling circuit, for example, because more measurements take more time.
The signal width detector 212 measures the signal width of the time code signal at least once to get the desired measurements and the waveform discrimination standard is changed based on the most frequent result in the foregoing embodiment, but the waveform discrimination standard can be changed based on the average of the measurements, for example. More particularly, the waveform discrimination standard can be changed based on the measurements.
Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.
The entire disclosure of Japanese Patent Application No. 2006-229538, filed Aug. 25, 2006 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP 2006-229538 | Aug 2006 | JP | national |
