Method and apparatus for rapidly estimating the doppler-error and other receiver frequency errors of global positioning system satellite signals weakened by obstructions in the signal path
First Claim
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1. A method for extracting Dö
- ppler-error components from digitized signal samples transmitted by a satellite, said method comprising the steps of;
receiving and digitizing said signals to produce digitized samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain.
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Abstract
Frequency-offset components are extracted from a set of digitized samples of signals transmitted by a satellite. The samples are squared to produce squared samples and decimated. The squared samples are auto-correlated to produce an auto-correlate, and the auto-correlate is truncated. The truncated auto-correlate is transformed into the frequency domain to obtain double-frequency offset components. The scaled offset frequencies are used to compensate for Doppler-shift and receiver frequency errors and for Doppler induced time errors in digitized samples used to estimate pseudorange information.
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Citations
39 Claims
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1. A method for extracting Dö
- ppler-error components from digitized signal samples transmitted by a satellite, said method comprising the steps of;
receiving and digitizing said signals to produce digitized samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain. - View Dependent Claims (2, 3)
obtaining the significant frequency components of said auto-correlate; and
scaling said frequency components for actual offset frequencies.
- ppler-error components from digitized signal samples transmitted by a satellite, said method comprising the steps of;
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3. The method of claim 1 wherein said step of decimating the squared samples includes:
applying said squared samples to a low-pass filter, creating narrow-band samples, said narrow-band samples having a plurality of sinusoidal components, wherein said low-pass filter reduces the signal and noise bandwidth of said squared samples and reduces the number of narrow-band samples to be Fourier transformed.
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4. A computer useable medium having stored therein instructions for causing a processing unit to execute the following method:
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receiving and digitizing said satellite signals to produce digitized signal samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain.
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5. A machine having a memory which contains data representing auto-correlates, said auto-correlates generated by the following method:
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receiving and digitizing said satellite signals to produce digitized signal samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain.
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6. A method of noise-filtering the digitized signal samples of said signals received from said satellites, said signals from satellites containing noise-energy, said method comprising the steps of:
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receiving and digitizing said noisy signals to produce digitized signal samples, said digitized signal samples having been squared;
auto-correlating said squared samples to emphasize the sinusoidal components in said squared samples, wherein said auto-correlation produces an auto-correlate that concentrates said noise-energy of said squared samples in a zero-time-shift component; and
removing said zero-time-shift component from the auto-correlate. - View Dependent Claims (7, 8, 9)
transforming said auto-correlate to the frequency domain; and
examining the resulting spectrum of said auto-correlate to obtain the frequency-offset components of said auto-correlate; and
scaling said frequency-offset components to yield actual offset frequencies.
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8. The method of claim 7 comprising the further steps of:
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using an actual offset frequency to compensate said digitized signal samples for a frequency-offset; and
determining the satellite identification code from said compensated digitized signal samples.
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9. The method of claim 7 comprising the further steps of:
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using the actual offset frequencies to compensate the digitize signal samples for the frequency-offsets; and
determining the pseudorange timing to said satellite from said compensated digitized signal samples.
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10. A computer useable medium having stored therein instructions for causing a processing unit to execute the following method:
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receiving and digitizing signals from satellites, said digitized signals having been squared, said signals from satellites containing noise-energy;
auto-correlating said squared samples of digitized signals received from said satellite signals to emphasize the sinusoidal components in said squared samples, wherein said auto-correlation produces an auto-correlate that concentrates said noise-energy of said squared samples in a zero-time-shift component; and
removing said component from the auto-correlate.
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11. A machine having a memory which contains data representing digitized samples of satellite signals, said samples of satellite signals produced by the following method:
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receiving and digitizing signals from satellites, said digitized signals having been squared, said signals from satellites containing noise;
auto-correlating said squared samples of digitized signals received from said satellite signals to emphasize the sinusoidal components in said squared samples, wherein said auto-correlation produces an auto-correlate that concentrates said noise-energy of said squared samples in a zero-time-shift component; and
removing said component from the auto-correlate.
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12. A method for extracting frequency-offset components for compensating for the frequency-offsets contained in the digitized signal samples of signals transmitted by a satellite, said method comprising the steps of:
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receiving and digitizing said digitized signal signals to produce digitized signal samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate;
transforming said auto-correlate to the frequency domain;
examining the resulting spectrum of said auto-correlate to obtain the frequency-offset components of said auto-correlate;
scaling said frequency-offset components to yield actual offset frequencies; and
using said actual offset frequencies to compensate for said frequency-offsets of said digitized signal samples. - View Dependent Claims (13, 14)
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15. A computer useable medium having stored therein instructions for causing a processing unit to execute the following method:
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receiving and digitizing signals from satellites to produce digitized samples;
squaring said digitized signal samples to produce squared samples;
auto-correlating said squared samples to produce an auto-correlate;
transforming said auto-correlate to the frequency domain;
examining the resulting spectrum of said squared samples to obtain the frequency-offset components of said auto-correlate;
scaling said frequency-offset components to yield actual offset frequencies; and
using said actual offset frequencies to compensate for said frequency-offsets components of said digitized signal samples.
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16. A device for extracting carrier components from digitized signal samples of signals transmitted by a satellite, comprising:
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means for receiving and digitizing said signals to produce digitized samples;
means for squaring said digitized samples to produce squared samples; and
means for auto-correlating said squared samples to produce an auto-correlate. - View Dependent Claims (17, 18, 19, 20)
means for obtaining frequency-offset components of said auto-correlate; and
means for scaling said frequency-offset components to yield the actual offset frequencies.
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18. The device of claim 16 further including means for decimating the squared samples includes means for low-pass filtering said squared samples to create narrow-band samples, said narrow-band samples having a plurality of sinusoidal components, wherein said low-pass filter reduces the signal and noise bandwidth of said squared samples.
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19. The device of claims 16, 17 or 18 wherein said device is an integral portion of a two-way wireless device.
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20. The device of claims 16, 17 or 18 wherein said device is included in an attachment, said attachment being coupled to a two-way wireless device.
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21. A device for filtering digitized samples of signals received from a satellite, said device comprising:
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means for receiving a digitized signal from said satellite, said signal containing noise-energy;
means for digitizing the signal, to provide digitized samples;
means for squaring said digitized signal samples, to provide a squared sample of signals from said satellite;
means for auto-correlating said squared samples of signals received from said satellite, to produce a signal sample that emphasizes the sinusoidal components in said squared sample, whereby said auto-correlation produces an auto-correlate that concentrates said noise-energy of said squared samples in a zero-time-shift component; and
means for removing said zero-time-shift component from the auto-correlate. - View Dependent Claims (22, 23, 24, 25)
means for transforming said auto-correlate to the frequency domain;
means for examining the resulting spectrum of said auto-correlate to obtain the frequency-offset components of said auto-correlate; and
means for scaling said frequency-offset components to yield actual offset frequencies.
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23. The device of claim 21 further comprising:
means for compensating for the Dö
ppler-errors to enable determining the unique satellite identification code.
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24. The device of claims 21, 22 or 23 wherein said device is an integral portion of a two-way wireless device.
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25. The device of claims 21, 22 or 23 wherein said device is included in an attachment, said attachment being coupled to a two-way wireless device.
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26. A wireless device comprising:
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an antenna that receives and transmits full-duplex wireless signals to and from a user;
processing means, coupled to said antenna, for processing said wireless signals to produce audio signals and communicating said audio signals to said user;
a GPS antenna to receive GPS signals, said GPS signal containing noise-energy;
means for digitizing said GPS signals into digitized signal samples;
means for squaring said digitized signal samples to produce squared samples;
means for decimating said squared samples;
auto-correlation means for auto-correlating said squared samples to produce an auto-correlate; and
means for transforming said auto-correlate to the frequency domain. - View Dependent Claims (27)
means for emphasizing the sinusoidal components of said squared signal samples;
means for concentrating said noise-energy of said squared sample in a zero-time-shift component; and
means for removing said zero-time-shift component from said auto-correlate.
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28. A wireless device attachment comprising:
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means for receiving GPS signals, said GPS signals containing noise-energy;
means for digitizing said GPS signals into digitized signal samples;
means for squaring said digitized signal samples to produce squared samples;
means for decimating said squared samples;
means for auto-correlating squared sample to produce an auto-correlate; and
means for transforming said auto-correlate to the frequency domain. - View Dependent Claims (29)
means for emphasizing the sinusoidal components in said squared samples, means for concentrating said noise-energy in said squared samples in a zero-time-shift component; and
means for removing said zero-time-shift component from said auto-correlate.
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30. A method for extracting Dö
- ppler-errors from a set of digitized samples of signals transmitted by a satellite, said method comprising the steps of;
receiving and capturing a set of digitized signal samples of said signals;
squaring said digitized signal samples to produce a set of squared samples;
auto-correlating said set of squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain. - View Dependent Claims (31)
obtaining frequency-offset components of said auto-correlate; and
scaling said frequency-offset components to yield actual offset frequencies.
- ppler-errors from a set of digitized samples of signals transmitted by a satellite, said method comprising the steps of;
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32. A computer useable medium having stored therein instructions for causing a processing unit to execute the following method:
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receiving and capturing a set of digitized samples of signals from satellites;
squaring said digitized signal samples to produce a set of squared samples;
auto-correlating said set of squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain.
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33. A method for extracting carrier components from a set of digitized samples of signals transmitted by a satellite, said method comprising the steps of:
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receiving and capturing a set of digitized samples of said signals from satellites;
squaring said digitized samples to produce a set of squared samples;
auto-correlating said set of squared samples to produce an auto-correlate; and
transforming said auto-correlate to the frequency domain. - View Dependent Claims (34, 35)
obtaining the frequency-offset components of said squared auto-correlate; and
scaling said frequency-offset components to yield actual offset frequencies.
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35. The method of claim 33 wherein said step of decimating the squared samples includes:
applying said squared samples to a low-pass filter and creating a plurality of narrow-band samples, said narrow-band signals having a plurality of sinusoidal components, wherein said low-pass filter reduces the signal and noise bandwidth of said samples.
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36. A computer useable medium having stored therein instructions for causing a processing unit to execute the following method:
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receiving and capturing a set of digitized signal samples of signals from satellites;
squaring said digitized samples to produce a set of squared samples;
decimating said squared samples; and
transforming said squared samples to the frequency domain.
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37. A method for extracting frequency-offset components to compensate for the time-shifts caused by the frequency-offsets contained in the digitized samples of signals transmitted by a satellite, said method comprising the steps of:
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receiving and digitizing said signals to produce digitized signal samples;
squaring said digitized signal samples to produce squared samples;
decimating said squared samples;
auto-correlating said squared samples to produce an auto-correlate;
transforming said auto-correlate to the frequency domain;
examining the resulting spectrum of said auto-correlate to obtain the frequency-offset components of said auto-correlate;
scaling said frequency-offset components to yield actual offset frequencies; and
using said actual offset frequencies to compensate for the Doppler-time-shift related to the said frequency-offsets components of said auto-correlate. - View Dependent Claims (38, 39)
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Specification