Reducing satellite signal interference in a global positioning system receiver
First Claim
1. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
- receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
estimating characteristics of said first signal to form estimated data;
constructing an interference waveform using said estimated data and a hypothesized carrier frequency of said second signal and pseudorandom codes corresponding to said first signal and said second signal;
performing tests for times of arrival of said second signal to produce a first output waveform;
selecting a portion of said interference waveform; and
subtracting said portion of said interference waveform from said first output waveform to produce a second output waveform.
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Abstract
A method and apparatus is disclosed for reducing cross-interference between received satellite signals in a satellite positioning system receiver. A satellite positioning receiver receives satellite signals from a plurality of satellites. Spurious signals when processing a weak received satellite signal due to interference by a stronger received signal are reduced by estimating certain characteristics of the stronger signal, creating an interference waveform based on these estimated characteristics, and subtracting this interference waveform from a set of correlation outputs for the weaker signal to remove the interference effects of the stronger signal. Alternatively, a subset of these correlation outputs are ignored where the interference waveform produces strong spurious signals.
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Citations
54 Claims
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1. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
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receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
estimating characteristics of said first signal to form estimated data;
constructing an interference waveform using said estimated data and a hypothesized carrier frequency of said second signal and pseudorandom codes corresponding to said first signal and said second signal;
performing tests for times of arrival of said second signal to produce a first output waveform;
selecting a portion of said interference waveform; and
subtracting said portion of said interference waveform from said first output waveform to produce a second output waveform. - View Dependent Claims (2, 3, 4, 5, 6, 43)
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7. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
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receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
estimating characteristics of said first signal to form estimated data;
constructing an interference waveform using said estimated data; and
subtracting said interference waveform from said first input waveform to produce an output waveform. - View Dependent Claims (8, 9, 10, 11, 12, 44)
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13. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
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receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
estimating characteristics of said first signal to form estimated data;
constructing an interference waveform using said estimated data and a hypothesized carrier frequency of said second signal and a first pseudorandom code corresponding to said first signal and a second pseudorandom code corresponding to said second signal;
performing tests for times of arrival of said second signal to produce an output waveform; and
discarding portions of said output waveform for which said interference waveform is above a predetermined threshold. - View Dependent Claims (14, 15, 16, 17, 45)
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18. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
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receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
estimating characteristics of said first signal to form estimated data;
detecting the presence of an interference component in said input signal by processing said estimated data and a hypothesized carrier frequency of said second signal;
determining the width of a peak of a signal produced by cross-correlations of said first signal and the PN code of said second signal if said interference component is detected;
comparing said width of said peak with a predetermined threshold;
performing tests for times of arrival of said second signal to produce an output waveform; and
deleting said peak from said output waveform if said width of said peak exceeds said predetermined threshold. - View Dependent Claims (19, 20, 21, 22, 46, 47)
estimating a signal to noise ratio for said peak at said satellite positioning system receiver; and
transmitting the estimated signal to noise ratio to said remote location remote from said satellite positioning system receiver.
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23. A method for reducing satellite signal cross-interference in a satellite positioning system receiver, said method comprising the steps of:
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receiving as an input waveform a first signal and a second signal from respective satellites of a plurality of satellite positioning system satellites, wherein said first signal is stronger than said second signal;
performing tests for times of arrival of said second signal to produce an output waveform;
subtracting a mean noise level from said output waveform to produce a modified output waveform;
establishing a detection threshold by multiplying a first constant by a root mean squared level of said modified output waveform; and
modifying said detection threshold by multiplying said detection threshold by a first value to produce a modified detection threshold. - View Dependent Claims (24, 25, 26, 27, 48)
comparing said modified output waveform with said modified detection threshold; and
signaling a detection of a pseudorandom noise signal for said second signal if a component of said modified output exceeds said modified detection threshold.
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26. The method of claim 25 wherein said tests for times of arrival of said second signal is a correlation operation.
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27. The method of claim 26 wherein said tests for times of arrival of said second signal is a matched filtering operation.
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48. The method of claim 23 wherein said steps of performing said tests, subtracting said mean noise level, establishing said detection threshold, and modifying said detection threshold are performed in a remote location separate from said satellite positioning system receiver, and wherein data is transmitted from said satellite positioning system receiver to said remote location to permit said steps to be performed.
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28. An apparatus comprising:
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an input circuit operable to receive satellite positioning system signals from a plurality of satellite positioning system satellites, and wherein a first received signal is stronger than a second received signal;
a processor coupled to said input circuit, said processor operable to estimate characteristics of said first signal;
construct an interference waveform based on the estimated characteristics;
perform tests for times of arrival of said second signal to produce an output waveform; and
subtract said interference waveform from said output waveform to remove interference effects of said first signal from said output waveform. - View Dependent Claims (29, 30)
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31. An apparatus comprising:
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an input circuit operable to receive satellite positioning system signals from a plurality of satellite positioning system satellites, and wherein a first received signal is stronger than a second received signal;
a processor coupled to said input circuit, said processor operable to estimate characteristics of said first signal;
construct an interference waveform based on the estimated characteristics; and
subtract said interference waveform from the received satellite positioning system signals to remove interference effects of said first signal from said received signals. - View Dependent Claims (32, 33)
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34. An apparatus comprising:
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an input circuit operable to receive satellite positioning system signals from a plurality of satellite positioning system satellites, and wherein a first received signal is stronger than a second received signal;
a processor coupled to said input circuit, said processor operable to estimate characteristics of said first signal;
construct an interference waveform based on the estimated characteristics and a first locally generated code corresponding to said first signal and a second locally generated code corresponding to said second signal;
perform tests for times of arrival of said second signal to produce an output waveform; and
discard portions of said output waveform for which said interference waveform is above a predetermined threshold. - View Dependent Claims (35, 36)
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37. An apparatus comprising:
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an input circuit operable to receive satellite positioning system signals from a plurality of satellite positioning system satellites, and wherein a first received signal is stronger than a second received signal;
a processor coupled to said input circuit, said processor operable to estimate characteristics of said first signal;
determine the possibility of interference from said first signal with said second signal using the estimated characteristics and a characteristic of said second signal;
perform tests for a time-of-arrival of said second signal to produce an output waveform;
compare the width of a peak in said output waveform with a predetermined threshold; and
discard said peak from further processing if said width exceeds said predetermined threshold, and the possibility of interference from said first signal with said second signal is affirmative. - View Dependent Claims (38, 39)
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40. An apparatus comprising:
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an input circuit operable to receive satellite positioning system signals from a plurality of satellite positioning system satellites, and wherein a first received signal is stronger than a second received signal;
a processor coupled to said input circuit, said processor operable to perform tests for times of arrival of said second signal to produce an output waveform;
subtract a mean noise level from said output waveform to form a modified output waveform;
establish a detection threshold based on a root mean squared value of data in said output waveform;
compare said modified output waveform with said detection threshold; and
signal a detection if a portion of said modified output waveform exceeds said detection threshold. - View Dependent Claims (41, 42)
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49. A method for processing satellite positioning system (SPS) signals transmitted from a first satellite, said method comprising the steps of:
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receiving said SPS signals at a mobile SPS receiver;
determining at least one signal-to-noise ratio for at least one of said SPS signals; and
transmitting said at least one signal-to-noise ratio to a remote processing system. - View Dependent Claims (50, 51)
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52. A method for processing satellite positioning system (SPS) signals transmitted from a first satellite, said method comprising the steps of:
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receiving said SPS signals at a mobile SPS receiver;
determining at least one peak width for at least one of said SPS signals; and
transmitting said at least one peak width to a remote processing system. - View Dependent Claims (53, 54)
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Specification