Radio-controlled timepiece, method of obtaining date/time information, and recording medium

Patent metadata

Field	Value
Publication number	US-9563179-B2
Application number	US-201514963449-A
Country	US
Kind code	B2
Filing date	Dec 9, 2015
Priority date	Dec 24, 2014
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

Abstract

A radio-controlled timepiece, including: a radio wave reception unit that receives satellite waves and extracts an incoming code sequence formatted in a prescribed format from the received satellite waves; and a processor that generates in advance an expected code sequence that is expected to be part of the incoming code sequence and detects the expected code sequence within the incoming code sequence by sequentially comparing the expected code sequence with the incoming code sequence, the processor determining a present date/time, as indicated by the satellite waves, in accordance with a timing at which the detected code sequence occurs within the incoming code sequence as measured by time kept by the timepiece, wherein the expected code sequence includes codes that change with a transmission period during which time-related information that includes satellite date/time contained in the satellite waves, which is formatted in the prescribed format, is transmitted.

First claim

What is claimed is:

1. A radio-controlled timepiece, comprising:
a radio wave reception unit that receives satellite waves and extracts an incoming code sequence formatted in a prescribed format from said received satellite waves; and
a processor that generates in advance an expected code sequence that is expected to be part of said incoming code sequence and detects said expected code sequence within said incoming code sequence by sequentially comparing said expected code sequence with said incoming code sequence, the processor determining a present date/time, as indicated by the satellite waves, in accordance with a timing at which said detected code sequence occurs within said incoming code sequence as measured by time kept by the timepiece,
wherein said expected code sequence includes codes that change with a transmission period during which time-related information that includes satellite date/time contained in the satellite waves, which is formatted in said prescribed format, is transmitted.

2. The radio-controlled timepiece according to claim 1 , further comprising:
a counter unit that counts a date/time of said radio-controlled timepiece,
wherein said processor determines an error in said date/time counted by said counter unit in accordance with said timing at which said detected code sequence occurs within said incoming code sequence, which is measured in said date/time counted by the counter unit.

3. The radio-controlled timepiece according to claim 1 , further comprising:
a counter unit that counts a date/time of said radio-controlled timepiece,
wherein said processor, in accordance with said date/time counted by said counter unit, generates said expected code sequence that includes a prescribed number of low-order bits that are part of a code sequence representing said time-related information and determines said present date/time in accordance with said timing at which said detected code sequence occurs within said incoming code sequence as measured in said date/time counted by said counter unit.

4. The radio-controlled timepiece according to claim 3 , wherein, if a time that is longer than or equal to said transmission period elapses without said expected code sequence being detected from said incoming code sequence, then said processor renews said expected code sequence in accordance with time-related information that is transmitted after said transmission period.

5. The radio-controlled timepiece according to claim 3 , wherein said processor determines whether an estimated error in said counter unit, which is estimated based on an elapsed time from a most recent time when said date/time of said counter unit was corrected, is greater than or equal to a reference time that is set based on said transmission period, and if said processor determines said error to be not greater than or equal to said reference time, said processor determines said present date/time based on said expected code sequence that includes said prescribed number of low-order bits.

6. The radio-controlled timepiece according to claim 3 , wherein said time-related information that is included in said expected code sequence includes a value that corresponds to a period number indicating a number of said transmission period.

7. The radio-controlled timepiece according to claim 3 , wherein said processor starts comparing said incoming code sequence with said expected code sequence at a moment in time that is before an estimated start time at which said expected code sequence is predicted to start in said incoming code sequence in said date/time counted by said counter unit and that is within one said transmission period measured from said estimated start time.

8. The radio-controlled timepiece according to claim 7 , wherein said processor estimates a range of error in said counter unit based on a time interval elapsed since a most recent time when said date/time counted by said counter unit was corrected and derives said estimated start time at which said expected code sequence is predicted to start in said incoming code sequence in accordance with said estimated range of error in said counter unit.

9. The radio-controlled timepiece according to claim 8 , wherein said radio wave reception unit determines a timing of when to start receiving said satellite waves based on said moment in time at which said processor starts comparing said incoming code sequence with said expected code sequence.

10. The radio-controlled timepiece according to claim 8 , wherein said radio wave reception unit starts receiving said satellite waves at a preset time interval prior said moment in time at which said processor starts comparing said incoming code sequence with said expected code sequence.

11. The radio-controlled timepiece according to claim 1 , wherein a length of said expected code sequence is set such that a probability that said expected code sequence occurs in a location that is not expected within said incoming code sequence is lower than a prescribed reference value.

12. The radio-controlled timepiece according to claim 11 , wherein said probability is computed by assuming that, in each of binary code bits that constitute said incoming code sequence, a probability that 0 occurs and a probability that 1 occurs are ½, respectively.

13. The radio-controlled timepiece according to claim 11 , wherein said prescribed reference value is set according to a number of times said radio wave reception unit is expected to receive said satellite waves during an expected lifespan of the radio controlled timepiece.

14. The radio-controlled timepiece according to claim 1 , wherein a length of said expected code sequence is set to be shorter than a length of a data block that includes: invariant code sequences that do not change with said transmission period; satellite time information; and an error correction code for said satellite time information.

15. The radio-controlled timepiece according to claim 14 , wherein said satellite waves are sent from a Global Positioning Satellite, and said length of said data block has a length of 2 words.

16. The radio-controlled timepiece according to claim 1 , wherein a transmitted code sequence that corresponds to content in transmitted information from a positioning satellite that transmits said satellite waves in said prescribed format includes inversion codes, said transmitted code sequence having unit blocks that are preset, and for each of the unit blocks, the corresponding inversion code determining whether to invert code bits in the unit block before said transmitted code sequence is transmitted, and
wherein said processor generates one expected code sequence that includes a code sequence in which each of the code bits in each of said unit blocks within said expected code sequence are inverted one said unit block at a time and another expected code sequence that includes another code sequence in which said each of the code bits are not inverted and compares both said one expected code sequence and said another expected code sequence with said incoming code sequence.

17. The radio-controlled timepiece according to claim 1 , further comprising:
a storage unit that stores a reception history of most recently received satellite waves and a code sequence that is obtained from said most recently received satellite waves,
wherein said processor determines, based on types of information represented by said code sequence that is stored in said storage unit, a part of said code sequence that does not change within a time interval between when said most recently received satellite waves were r

Assignees

• Casio Computer Co Ltd

Inventors

• Matsue Takeshi
• Abe Hideo
• Abe Kazuaki

Classifications

• G01S19/256

  relating to timing, e.g. time of week, code phase, timing offset · CPC title

• G04R20/06 Primary

  Decoding time data; Circuits therefor · CPC title