Method and apparatus for increasing the sensitivity of a global positioning satellite receiver
First Claim
1. A method for improving the sensitivity of a Global Positioning System (GPS) receiver, the method including the steps of:
- a) receiving a GPS signal from a GPS satellite;
b) determining whether the receiver has a source for synchronization to GPS time other than the GPS satellite itself; and
c) if there is a source for synchronization to GPS time other than the GPS satellite itself, then;
1) determining, from the synchronization source, the boundaries of a plurality of code periods in the received GPS signl;
2) determining the amount of power in the received GPS signal by applying a particular code associated with a particular satellite to the received GPS signal during each of the plurality of code periods;
3) summing the power received during each code period to determine a total integrated power over the sum of the plurality of code periods; and
4) processing the received GPS signal using information about the particular satellite if the total integrated power is greater than a threshold value.
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Accused Products
Abstract
Method and apparatus providing enhanced sensitivity for GPS receivers by allowing coherent integration of a correlation over several code periods of a GPS signal in one embodiment, and by performing a time to frequency domain conversion to the output from a correlation processor in a second embodiment. In the case in which coherent integration is performed over several code periods, advantage is taken of the fact that CDMA cellular telephone base stations transmit information that allows the receiver to determine GPS time before beginning a GPS signal acquisition process. The integration can be expanded to include code periods from more than one bit period, if the GPS receiver takes advantage of the fact that known bit patterns are transmitted at particular times within the transmission from a GPS satellite. If no base station is within range, then the output from a correlator that integrates a correlation over one code period is used to generate values that are input to in a discrete time domain to frequency domain transform. The output from the transform will indicate the presence of a signal from a particular satellite and the offset between locally generated signal and the received GPS signal.
236 Citations
18 Claims
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1. A method for improving the sensitivity of a Global Positioning System (GPS) receiver, the method including the steps of:
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a) receiving a GPS signal from a GPS satellite;
b) determining whether the receiver has a source for synchronization to GPS time other than the GPS satellite itself; and
c) if there is a source for synchronization to GPS time other than the GPS satellite itself, then;
1) determining, from the synchronization source, the boundaries of a plurality of code periods in the received GPS signl;
2) determining the amount of power in the received GPS signal by applying a particular code associated with a particular satellite to the received GPS signal during each of the plurality of code periods;
3) summing the power received during each code period to determine a total integrated power over the sum of the plurality of code periods; and
4) processing the received GPS signal using information about the particular satellite if the total integrated power is greater than a threshold value. - View Dependent Claims (2, 3, 4, 5, 6)
d) if there is no source for synchronization to GPS time other than the GPS satellite itself, then;
1) performing a time to frequency domain transform on the power in the received GPS signal encoded with the particular code associated with the particular satellite during each of the plurality of code periods; and
2) processing the received GPS signal using information about the particular satellite if the amount of power in any one of the frequencies in the frequency domain is greater than a predetermined threshold.
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5. The method of claim 4, wherein the s ource for synchronization to GPS time comprises a signal from a Code Division Multiple Access (CDMA) base station.
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6. The method of claim 5, wher ein the signal fr om the CDMA base station includes information based on the round trip delay from the GPS receiver to the base station and back to adjust the offset between CDMA system time and GPS time.
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7. Apparatus for improving the sensitivity of a Global Positioning System (GPS) receiver, the apparatus including:
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a) means for receiving a GPS signal from a GPS satellite;
b) means for determining whether the receiver has a source for synchronization to GPS time other than the GPS satellite itself;
c) means, responsive to a determination that there is a source for synchronization to GPS time other than the GPS satellite itself, for;
1) determining, from the synchronization source, the boundaries of a plurality of code periods in the received GPS signal;
2) determining the amount of power in the received GPS signal by applying a particular code associated with a particular satellite to the received GPS signal during each of the plurality of code periods;
3) summing the power received during each code period to determine a total integrated power over the sum of the plurality of code periods; and
4) processing the received GPS signal using information about the particular satellite if the total integrated power is greater than a threshold value. - View Dependent Claims (8, 9, 10, 11, 12)
a) to respond to information, included in the signal from the CDMA base station, based on the round trip delay from the GPS receiver to the bases station and back; and
b) to thereby adjust the offset between CDMA system time and GPS time.
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10. The apparatus of claim 7, further including means, responsive to a determination that there is no source for synchronization to GPS time other than the GPS satellite itself, for:
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a) performing a time to frequency domain transform on the power in the received GPS signal encoded with the particular code associated with the particular satellite during each of the plurality of code periods; and
b) processing the received GPS signal using information about the particular satellite if the amount of power in any one of the frequencies in the frequency domain is greater than a predetermined threshold.
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11. The apparatus of claim 10, wherein the means for determining whether the receiver has a source for synchronization to GPS time, other than the GPS satellite itself, is constructed to respond to a signal from a Code Division Multiple Access (CDMA) base station.
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12. The apparatus of claim 11, wherein the means for determining whether the receiver has a source for synchronization to GPS time, other than the GPS satellite itself, is constructed:
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a) to respond to information, included in the signal from the CDMA base station, based on the round trip delay from the GPS receiver to the base station and back; and
b) to thereby adjust the offset between CDMA system time and GPS time.
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13. A method for improving the sensitivity of a Global Positioning System (GPS) receiver, the method including the steps of:
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a) receiving a GPS signal from a GPS satellite;
b) providing the receiver with a source for synchronization to GPS time, other than the GPS satellite itself;
c) determining, from the synchronization source, the boundaries of a plurality of code periods in the received GPS signal;
d) determining the amount of power in the received GPS signal by applying a particular code associated with a particular satellite to the received GPS signal during each of the plurality of code periods;
e) summing the power received during each code period to determine a total integrated power over the sum of the plurality of code periods; and
f) processing the received GPS signal using information about the particular satellite if the total integrated power is greater than a threshold value. - View Dependent Claims (14, 15)
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16. Apparatus for improving the sensitivity of a Global Positioning System (GPS) receiver, the apparatus including:
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a) means for receiving a GPS signal from a GPS satellite;
b) means for providing the receiver with a source for synchronization to GPS time, other than the GPS satellite itself;
c) means for determining, from the synchronization source, the boundaries of a plurality of code periods in the received GPS signal;
d) means for determining the amount of power in the received GPS signal by applying a particular code associated with a particular satellite to the received GPS signal during each of the plurality of code periods;
e) means for summing the power received during each code period to determine a total integrated power over the sum of the plurality of code periods; and
f) means for processing the received GPS signal using information about the particular satellite if the total integrated power is greater than a threshold value. - View Dependent Claims (17, 18)
a) to respond to information, included in the signal from the CDMA base station, based on the round trip delay from the GPS receiver to the base station and back; and
b) to thereby adjust the offset between CDMA system time and GPS time.
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Specification