Narrowband noise mitigation in location-determining signal processing
AssigneeSiRF Technology, Inc.
InventorsNainesh Agarwal, Anant Sahai, John Tsitsiklis
Life of this patent
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Abstract
System and method for mitigating the effects of narrowband noise in a location-determining signal are provided, wherein the location-determining signal is associated with a periodic reference signal, the embodiments include identifying a set of noisy frequencies in the signal, determining a set of frequencies to be removed, and removing the set of frequencies from either the location-determining signal or the reference signal, thereby removing the effects of narrowband noise from the location-determining signal.
Claims61
A method for removing the effects of narrowband noise from a location-determining signal associated with a reference signal, the method comprising:
- identifying a set of noisy frequencies in said location-determining signal;
- determining a set of frequencies to be removed associated with said set of noisy frequencies;
- removing said set of frequencies to be removed from said reference signal, thereby removing the effects of narrowband noise from said location-determining signal.
The method of the previous claim, wherein said removing comprises calculating a fast fourier transform (FFT) of a length M block of said reference signal, to yield a plurality of FFT coefficients each associated with a frequency which is a multiple of 1/M.
The method of the previous claim, wherein said removing comprises zeroing out said FFT coefficients corresponding to said set of frequencies to be removed.
The method of the previous claim, comprising performing an inverse FFT calculation to generated a modified reference signal.
A method for removing the effects of narrowband noise from a location-determining signal associated with a reference signal, the method comprising:
- selecting a length L block of said location-determining signal;
- calculating a fast fourier transform (FFT) of said length L block, to yield a plurality of identification FFT coefficients;
- comparing the magnitudes of said identification FFT coefficients to a threshold to identify a set of noisy frequencies at which said location-determining signal has narrowband noise;
- determining a set of frequencies to be removed associated with said set of noisy frequencies;
- calculating a fast fourier transform of a length M block of said reference signal, to yield a plurality of reference signal FFT coefficients each associated with a frequency which is a multiple of 1/M;
- decreasing the reference signal FFT coefficients that correspond to said set of frequencies to be removed, thereby removing the effects of narrowband noise from said location-determining signal.
A method for removing the effects of narrowband noise from a location-determining signal associated with a reference signal, the method comprising:
- selecting a plurality of blocks of said location-determining signal;
- calculating a fast fourier transform (FFT) of each of said blocks, to yield a plurality of identification FFT coefficients;
- combining the magnitudes of the identification FFT coefficients of said blocks to generated a plurality of combined magnitudes;
- comparing said combined magnitudes to a threshold to identify a set of noisy frequencies at which said location-determining signal has narrowband noise;
- determining a set of frequencies to be removed associated with said set of noisy frequencies;
- calculating a fast fourier transform of a length M block of said reference signal, to yield a plurality of reference signal FFT coefficients each associated with a frequency which is a multiple of 1/M;
- decreasing the reference signal FFT coefficients that correspond to said set of frequencies to be removed, thereby removing the effects of narrowband noise from said location-determining signal.
A receiver, comprising:
- a processor;
- a communication device, receiving a location-determining signal;
- and
- a storage device in communication with said processor and storing instructions adapted to be executed by said processor to identify a set of noisy frequencies in said location-determining signal, determine a set of frequencies to be removed associated with said set of noisy frequencies;
- and to remove said set of frequencies to be removed from a plurality of reference signals associated with said location-determining signal, thereby removing the effects of narrowband noise from said location-determining signal.
A medium storing instructions adapted to be executed by a processor in a method to mitigate the effects of narrowband noise in a location-determining signal associated with a plurality of reference signals, the method comprising:
- identifying a set of noisy frequencies in said location-determining signal;
- determining a set of frequencies to be removed associated with said set of noisy frequencies;
- removing said set of frequencies to be removed from said reference signal, thereby removing the effects of narrowband noise from said location-determining signal.
A method for removing noise from a sampled signal, comprising:
- identifying an undesirable frequency in said sampled signal, wherein said undesirable frequency is associated with narrowband noise;
- partitioning said sampled signal into a plurality of M length blocks, each of said M length blocks having a length M;
- identifying a frequency to be removed from said sampled signal;
- calculating a fast fourier transform (FFT) for each of said M length blocks, to yield a plurality of FFT coefficients;
- and
- zeroing out, for each of said M length blocks, said FFT coefficients corresponding to said frequency to be removed.
A method for removing narrowband noise from a location-determining signal, comprising:
- identifying a first set of frequencies in said signal, wherein each frequency of said first set is associated with narrowband noise;
- partitioning said signal into a plurality of M length blocks, each of said M length blocks having a length M;
- identifying a second set of frequencies to be removed from said signal, said second set based on said first set of frequencies;
- calculating a fast fourier transform (FFT) for each of said M length blocks, to yield a plurality of FFT coefficients;
- and
- removing, for each of said M length blocks, said FFT coefficients corresponding to a frequency in said second set of frequencies.
A receiver, comprising:
- a processor;
- and
- a storage device in communication with said processor and storing instructions adapted to be executed by said processor to:
- identify an undesirable frequency in a signal, wherein said undesirable frequency is associated with narrowband noise;
- partition said signal into a plurality of blocks, each of said blocks having a length M;
- identify a frequency to be removed from said signal;
- calculate a fast fourier transform (FFT) for each of said blocks, said FFT of each of said blocks having a plurality of coefficients;
- and
- zero out, for each of said blocks, said coefficients corresponding to said frequency to be removed.
A medium storing instructions adapted to be executed by a processor to mitigate the effects of narrowband noise in a location-determining signal, comprising:
- identifying an undesirable frequency in said signal, wherein said undesirable frequency is associated with narrowband noise;
- partitioning said signal into a plurality of blocks, each of said blocks having a length M;
- identifying a frequency to be removed from said signal;
- calculating a fast fourier transform (FFT) for each of said blocks, said FFT of each of said blocks having a plurality of coefficients;
- and
- zeroing out, for each of said blocks, said coefficients corresponding to said frequency to be removed.
A method of identifying narrowband noise in a location-determining signal, comprising:
- receiving a location-determining signal;
- pre-processing said location-determining signal to generate a signal;
- selecting a plurality of blocks of said signal;
- calculating a fast fourier transform (FFT) of each of said blocks, to yield a plurality of coefficients each having a magnitude;
- creating a plurality of combined magnitudes from said magnitudes;
- and
- comparing said combined magnitudes to a threshold to identify narrowband noise in said signal.
A method for identifying narrowband noise in a signal, comprising:
- receiving a signal;
- selecting a plurality of blocks of said signal, each having a length that is small in comparison to an overall duration of said signal;
- calculating a fast Fourier transform (FFT) of each of said blocks, said FFT of each of said blocks having a plurality of coefficients each having a magnitude;
- generating a plurality of combined magnitudes using said magnitudes;
- and
- comparing said combined magnitudes to a threshold to identify narrowband noise in said signal.
A method for identifying narrowband noise in a location-determining signal, comprising:
- receiving said location-determining signal;
- preprocessing said location-determining signal to generate a preprocessed signal;
- selecting a plurality of blocks of said preprocessed signal;
- calculating, for each of said plurality of blocks, a plurality of fast Fourier transform (FFT) coefficients, wherein each of said coefficients is at a different frequency, and each of said coefficients having a magnitude;
- combining the magnitudes of said coefficients to generate a plurality of combined magnitudes;
- and
- identifying those frequencies for which said combined magnitudes exceed a threshold, said identified frequencies representing frequencies having narrowband noise.
A receiver, comprising:
- a processor;
- a communication device coupled to said processor and receiving a location-determining signal;
- and
- a storage device in communication with said processor and storing instructions adapted to be executed by said processor to:
- preprocess said location-determining signal to generate a preprocessed signal;
- select a plurality of blocks of said preprocessed signal;
- calculate a fast fourier transform (FFT) of each of said blocks, said FFT of each of said blocks having a plurality of coefficients;
- calculate combined magnitudes from the magnitudes of said coefficients, and
- compare said combined magnitudes to a threshold to identify narrowband noise of said signal.
A medium storing instructions adapted to be executed by a processor to identify narrowband noise in a location-determining signal, comprising:
- selecting a plurality of blocks of said signal;
- calculating a fast fourier transform (FFT) of each of said blocks, said FFT of each of said blocks having a plurality of coefficients;
- calculating combined magnitudes from the magnitudes of said coefficients;
- and
- comparing said combined magnitudes to a threshold to identify narrowband noise of said signal.
Dependencies are inferred from the claim text.