Satellite radio wave receiving device, electronic timepiece, positioning control method, and storage medium

Patent metadata

Field	Value
Publication number	US-2018231663-A1
Application number	US-201815893419-A
Country	US
Kind code	A1
Filing date	Feb 9, 2018
Priority date	Feb 13, 2017
Publication date	Aug 16, 2018
Grant date	—

Abstract

A processor of a satellite radio wave receiving device processes radio waves received by a receiver to identify a bit value in each of divided unit time segments that are obtained by dividing a time period of one bit into a plurality of unit time segments of equal duration; creates a bit array having the identified bit values in respective divided unit time segments by sequentially arranging the identified bit values in an order of receipt, the one or more processors creating said bit array in a plurality by successively shifting a time at which the bit array starts by one unit time segment; and performs a bit edge detection operation by detecting a head timing of the bit data at which a bit value changes in the received radio waves based on said plurality of bit value arrays.

First claim

What is claimed is:

1 . A satellite radio wave receiving device comprising:
a receiver that receives radio waves transmitted from a satellite, the radio waves including a message signal having a sequence of bit data with each bit being assigned with a prescribed duration; and one or more processors, wherein the one or more processors perform the following:
processing the radio waves received by the receiver to identify a bit value in each of divided unit time segments that are obtained by dividing a time period that has a same duration as said prescribed duration into a plurality of unit time segments of equal duration;
creating a bit array having the identified bit values in the respective divided unit time segments by sequentially arranging the identified bit values in an order of receipt, the one or more processors creating said bit array in a plurality by successively shifting a time at which the bit array starts by one unit time segment;
performing a bit edge detection operation by detecting a head timing of the bit data at which a bit value changes in the received radio waves based on said plurality of bit value arrays;
correcting a deviation within said prescribed duration in a current date and time that is counted internally in the satellite radio wave receiving device in accordance with the detected head timing; and
performing positioning by calculating a position of the satellite radio wave receiving device using the corrected current date and time.

2 . The satellite radio wave receiving device according to claim 1 ,
wherein the one or more processors carry out the bit edge detection operation for at least one of the transmitted radio waves from a plurality of positioning satellites used for the positioning, and carry out the positioning using the current date and time that has been corrected according to the detected head timing.

3 . The satellite radio wave receiving device according to claim 2 ,
wherein the one or more processors externally acquire position information of the plurality of positioning satellites, and carry out the positioning using the position information and the corrected current date and time.

4 . The satellite radio wave receiving device according to claim 1 ,
wherein the divided unit time segments each have a length of one period of a pseudo noise code with which the message signal is spectrum-spread, and are set respectively in synchronization with respective periods of the pseudo noise code.

5 . The satellite radio wave receiving device according to claim 2 ,
wherein the divided unit time segments have a length of one period of a pseudo-noise code with which the message signal is spectrum-spread, and are set respectively in synchronization with respective periods of the pseudo noise code.

6 . The satellite radio wave receiving device according to claim 1 ,
wherein the one or more processors, in the bit edge detection operation, perform the following:
comparing each of said plurality of bit arrays with a prescribed comparison bit array for every unit time segment to determine, among the plurality of bit arrays, a first bit array that has a largest degree of matching or a largest degree of mismatching with the prescribed comparison bit array, said prescribed comparison bit array being a predetermined sequence of bits having a duration of a plural number of the unit time segments, and having a bit boundary in a middle of the sequence at which a bit value changes from 0 to 1 or from 1 to 0; and
determining a position of the bit boundary of said determined first bit array as corresponding to the head timing at which the bit value changes in the received radio waves.

7 . The satellite radio wave receiving device according to claim 6 ,
wherein the duration of said prescribed comparison bit array is set to be equal to said prescribed duration in which each bit lasts in the sequence of the bit data in the message signal.

8 . The satellite radio wave receiving device according to claim 6 ,
wherein the one or more processors, in the bit edge detection operation, further perform the following: when comparing each of said plurality of bit arrays with the prescribed comparison bit array, also determining, among the plurality of bit arrays, a second bit array that has a second largest degree of matching or a second largest degree of mismatching with the prescribed comparison bit array; evaluating a probability of erroneously determining the first bit array relative to a probability of erroneously determining the second bit array so as to determine whether to trust the determination of the first bit array; and when the first bit array is determined to be trusted, determining the position of the bit boundary of said determined first bit array as corresponding to the head timing at which the bit value changes in the received radio waves.

9 . The satellite radio wave receiving device according to claim 8 ,
wherein in comparing each of said plurality of bit arrays with the prescribed comparison bit array to determine the first and second bit arrays, the one or more processors regard a smaller out of a degree of matching and a degree of mismatching as a redefined degree of mismatching, determine a bit array that has a smallest value in the redefined degree of mismatching as the first bit array, and determine a bit array that has a second smallest value in the redefined degree of mismatching as the second bit array in executing bit edge detection operation.

10 . The satellite radio wave receiving device according to claim 9 ,
wherein in evaluating the probability of erroneously determining the first bit array relative to the probability of erroneously determining the second bit array, the one or more processors calculate a ratio of the probability of erroneously determining the first bit array to the probability of erroneously determining the second bit array, and when said ratio is less than or equal to a prescribed value, the one or more processors determine that the first bit array is trusted.

11 . The satellite radio wave receiving device according to claim 10 ,
wherein when comparing each of said plurality of bit arrays with the prescribed comparison bit array, the one or more processors further evaluate whether a difference between the degree of matching and the degree of mismatching is equal to or less than a prescribed reference difference, and when the difference between the degree of matching and the degree of mismatching is equal to or less than the prescribed reference value, disregard results of the comparing each of said plurality of bit arrays with the prescribed comparison bit array, and do not perform the bit edge detection operation, and wherein when the bit edge detection operation is being performed and when said ratio of the probability of erroneously determining the first bit array to the probability of erroneously determining the second bit array is greater than the prescribed value, the one or more processors determine that the first bit array is not trusted and cause said plurality of bit value arrays to be renewed.

12 . The satellite radio wave receiving device according to claim 8 ,
wherein in evaluating the probability of erroneously determining the first bit array relative to the probability of erroneously determining the second bit array, the one or more processors evaluate a degree of mismatching in bit arrays that are shifted from the first bit array by a prescribed number of the unit time segments with respect to the prescribed comparison bit array, and a degree of mismatching in bit arrays that are shifted from the second bit array by a prescribed number of the unit time segme

Assignees

• Casio Computer Co Ltd

Inventors

• Matsue Takeshi

Classifications

• G01S19/42 Primary

  Determining position · CPC title

• G04R20/06

  Decoding time data; Circuits therefor · CPC title

• G01S19/05 Primary

  providing aiding data · CPC title

• G01S19/243

  Demodulation of navigation message · CPC title

• G01S19/24

  Acquisition or tracking {or demodulation} of signals transmitted by the system {(synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073)} · CPC title