Method for setting search band widths of a GPS receiver
First Claim
1. A method of setting a search band in a GPS receiver, the method comprising the steps of:
- a) reading from a memory a stored oscillator offset value, and determining if said stored oscillator offset value is within a predetermined reference range;
b) if said stored offset value is within said predetermined reference range, setting said search band around a center frequency determined by a doppler effect of said GPS satellite and said stored oscillator offset value and searching over a first range of frequencies; and
c) if said stored offset value is outside said predetermined reference range, setting said search band around a center frequency determined by said doppler effect of said GPS receiver and said stored oscillator offset value and searching over a second frequency range, said second frequency range being wider than said first range of frequencies.
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Accused Products
Abstract
In a GPS receiver which searches for a satellite radio wave over a predetermined search bandwidth while setting a search center frequency fs to a start point, an offset value of Δfosc of an oscillator calculated last when a power source of the receiver is turned off upon completion of the position measurement is stored as a backup value into a memory. When the power source of the receiver is turned on at the next position measurement, the backup offset value Δfosc is read out and an initial search bandwidth W0 at the start of the position measurement is set in accordance with the magnitude of the offset value. According to another feature, when the offset value of the oscillator calculated during the position measurement exceeds a predetermined reference value, a time point of the calculation is backed up into a memory. If a predetermined reference time has not elasped from the backup time point, at the time point when the power source is turned on for the next position measurement, an initial search bandwidth at the start of the position measurement is set to a wide band.
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Citations
21 Claims
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1. A method of setting a search band in a GPS receiver, the method comprising the steps of:
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a) reading from a memory a stored oscillator offset value, and determining if said stored oscillator offset value is within a predetermined reference range; b) if said stored offset value is within said predetermined reference range, setting said search band around a center frequency determined by a doppler effect of said GPS satellite and said stored oscillator offset value and searching over a first range of frequencies; and c) if said stored offset value is outside said predetermined reference range, setting said search band around a center frequency determined by said doppler effect of said GPS receiver and said stored oscillator offset value and searching over a second frequency range, said second frequency range being wider than said first range of frequencies. - View Dependent Claims (2, 3, 4)
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5. A method of setting a search band in a GPS receiver, the method comprising the steps of:
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reading from a memory in said receiver a stored oscillator offset value and determining if said stored oscillator offset value is to be used as a backup value; if said stored oscillator offset value is not to be used as a backup value, setting said search band around a center frequency determined by a doppler effect of a GPS satellite and a desired offset and searching over a first predetermined range of frequencies; if said stored oscillator offset value is to be used as a backup value, further determining if said stored offset value is within a predetermined reference range; if said stored offset value is within said predetermined reference range, setting said search band around a center frequency determined by said doppler effect of said GPS satellite and said backup value and searching over a second range of frequencies; and if said stored offset value is outside said predetermined reference range, setting said search band around a center frequency determined by said doppler effect of said GPS receiver and said backup value and searching over a third frequency range, said third frequency range being wider than said second frequency range. - View Dependent Claims (6, 7)
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8. A method of setting a search band in a GPS receiver, the method comprising the steps of:
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a) if an offset value of an oscillator in said receiver measured at a first time exceeds a reference value, determining if a time period between a present time and said first time exceeds a reference time; b) if said time period exceeds said reference time, setting a search bandwidth of said receiver to a first bandwidth; and c) if said time period does not exceed said reference time, setting said search bandwidth to a second bandwidth, said second bandwidth being narrower than said first bandwidth. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of setting a search bandwidth in a GPS receiver, the method comprising the steps of:
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reading from a memory in said receiver a stored oscillator offset value as a backup value; if said backup value exceeds a reference offset value by a predetermined amount in a first direction, setting said search bandwidth around a center frequency to have a first search range of frequencies in said first direction and a second range of search frequencies in a direction opposite said first direction, said first range being broader than said second range. - View Dependent Claims (18, 19, 20, 21)
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Specification