Method for obtaining precise intermediate frequency of global positioning system (GPS)
First Claim
1. A method for obtaining a precise intermediate frequency of a global positioning system (GPS), applied in a GPS receiver having a radio frequency (RF) module, the method comprising:
- searching a satellite by using a designated frequency of the RF module;
receiving at least one satellite signal from the satellite with a signal frequency;
obtaining an ephemeris data of the satellite by using the received satellite signal;
calculating a present coordinate of the GPS receiver by using the received satellite signal;
calculating a first coordinate of the satellite at a first time point by using the ephemeris data;
obtaining a second coordinate of the satellite at a second time point by using the ephemeris data;
calculating a traveling speed of the satellite by using the first time point, the first coordinate, the second time point, and the second coordinate;
calculating a projection value of the traveling speed on a position vector from the first coordinate to the present coordinate;
multiplying a carrier frequency of the satellite by a ratio between the projection value and a velocity of light to obtain an influence value of the Doppler Effect; and
subtracting the influence value of the Doppler Effect from the signal frequency to obtain an intermediate frequency.
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Abstract
A method for obtaining a precise intermediate frequency for a global positioning system (GPS) is applied in a GPS receiver having a radio frequency (RF) module. Using a satellite signal received by the RF module, ephemeris data of a satellite is completely obtained, and present coordinate of the GPS receiver is calculated. First coordinate of the satellite at first time point and second coordinate of the satellite at second time point are calculated using the ephemeris data. Then, traveling speed of the satellite and projection value of the traveling speed on position vector from the first coordinate to the present coordinate are calculated using the first time point, the first coordinate, the second time point, and the second coordinate. Finally, the precise intermediate frequency is calculated using the signal frequency, a carrier frequency of the satellite, the projection value, and velocity of light.
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Citations
10 Claims
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1. A method for obtaining a precise intermediate frequency of a global positioning system (GPS), applied in a GPS receiver having a radio frequency (RF) module, the method comprising:
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searching a satellite by using a designated frequency of the RF module; receiving at least one satellite signal from the satellite with a signal frequency; obtaining an ephemeris data of the satellite by using the received satellite signal; calculating a present coordinate of the GPS receiver by using the received satellite signal; calculating a first coordinate of the satellite at a first time point by using the ephemeris data; obtaining a second coordinate of the satellite at a second time point by using the ephemeris data; calculating a traveling speed of the satellite by using the first time point, the first coordinate, the second time point, and the second coordinate; calculating a projection value of the traveling speed on a position vector from the first coordinate to the present coordinate; multiplying a carrier frequency of the satellite by a ratio between the projection value and a velocity of light to obtain an influence value of the Doppler Effect; and subtracting the influence value of the Doppler Effect from the signal frequency to obtain an intermediate frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification