Super directional beamforming design and implementation
First Claim
1. A sensor array for receiving a signal that includes a desired signal and noise, comprising:
- a plurality of sensors;
a plurality of filters for filtering the output of each sensor, each filter being defined by one or more filter coefficients; and
a means for combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter.
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Accused Products
Abstract
A sensor array receiving system which incorporates one or more filters that are capable of adaptive and/or fixed operation. The filters are defined by a multiple of coefficients and the coefficients are set so as to maximize the signal to noise ratio of the receiving array'"'"'s output. In one preferred embodiment, the filter coefficients are adaptively determined and are faded into a predetermined group of fixed values upon the occurrence of a specified event. Thereby, allowing the sensor array to operate in both the adaptive and fixed modes, and providing the array with the ability to employ the mode most favorable for a given operating environment. In another preferred embodiment, the filter coefficients are set to a fixed group of values which are determined to be optimal for a predefined noise environment.
416 Citations
44 Claims
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1. A sensor array for receiving a signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a plurality of filters for filtering the output of each sensor, each filter being defined by one or more filter coefficients; and
a means for combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
a plurality of delay lines, said delay lines corresponding to respective outputs of said sensors and receiving respective outputs from said sensors; and
a plurality of convolvers, corresponding to respective outputs of said delay lines, said convolvers being operative to receive respective outputs from said delay lines and convolve the received outputs with respective filter coefficients to generate a plurality of filtered delay line outputs;
wherein said plurality of filtered delay line outputs are combined by said means for combining to form said array output.
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6. The sensor array as set forth in claim 5, further comprising a plurality of signal conditioners for receiving respective outputs from said sensors, sampling the received outputs and passing the sampled received outputs to respective delay lines.
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7. The sensor array as set forth in claim 1, wherein said fixed filter coefficients are determined by placing the array in a simulated noise environment, letting the adaptation of the filter weights converge to a solution and then setting the fixed filter coefficients equal to the coefficients of the converged adaptive solution.
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8. The sensor array as set forth in claim 1, wherein said fixed filter coefficients are determined by simulating a noise environment and the array'"'"'s response to said noise environment, letting the simulated adaptation of the filter weights converge to a solution and then storing the coefficients of the converged adaptive solution for use as the fixed weights of an actual array.
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9. A sensor array for receiving a signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a plurality of filters for filtering the output of each sensor, each filter being defined by one or more filter coefficients; and
a means for combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter; and
wherein said fixed filter coefficients are determined by simulating a noise environment, recording the simulated noise generated in said environment, playing back said simulated noise for reception by the array, letting the adaptation of the filter weights converge to a solution and then setting the fixed filter coefficients of the array equal to the coefficients of the converged adaptive solution.
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10. An sensor array for receiving signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a delay and sum beamformer for combining the outputs of said sensors to generate a beamformer output;
a reference channel processor for combining the outputs of said sensors to generate one or more reference channel signals;
at least one filter for each said reference channel, each said filter being defined by one or more coefficients; and
means for combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said reference channel processor and said filters operate to maximize the signal to noise ratio of the array output signal, wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. An sensor array for receiving signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a delay and sum beamformer for combining the outputs of said sensors to generate a beamformer output;
a reference channel processor for combining the outputs of said sensors to generate one or more reference channel signals;
at least one filter for each said reference channel, each said filter being defined by one or more coefficients; and
means for combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said reference channel processor and said filters operate to maximize the signal to noise ratio of the array output signal, wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
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19. A method of processing a received signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
filtering the output of each sensor through a filter, each filter being defined by one or more filter coefficients; and
combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter.- View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
receiving the outputs of said sensors at a plurality of respective delay lines;
receiving the outputs of said delay lines at respective convolvers;
convolving the received delay line outputs with respective filter coefficients to generate a plurality of filtered delay line outputs; and
combining said plurality of filtered delay line outputs to generate said array output.
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24. The sensor array as set forth in claim 23, further comprising the steps of:
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receiving the outputs of said sensors at respective signal conditioners; and
sampling the received outputs and passing the sampled received outputs to respective delay lines.
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25. The sensor array as set forth in claim 19, wherein said fixed filter coefficients are determined by placing the array in a simulated noise environment, letting the adaptation of the filter weights converge to a solution and then setting the fixed filter coefficients equal to the coefficients of the converged adaptive solution.
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26. The sensor array as set forth in claim 19, wherein said fixed filter coefficients are determined by simulating a noise environment and the array'"'"'s response to said noise environment, letting the simulated adaptation of the filter weights converge to a solution and then storing the coefficients of the converged adaptive solution for use as the fixed weights of an actual array.
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27. A method of processing a received signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
filtering the output of each sensor through a filter, each filter being defined by one or more filter coefficients; and
combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter; and
wherein said fixed filter coefficients are determined by simulating a noise environment, recording the simulated noise generated in said environment, playing back said simulated noise for reception by the array, letting the adaptation of the filter weights converge to a solution and then setting the fixed filter coefficients of the array equal to the coefficients of the converged adaptive solution.
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28. A method for receiving a signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
generating a beamformer output by passing the outputs of said sensors through a delay and sum beamformer;
generating one or more reference channel signals by passing the outputs of said sensors through a reference channel processor;
filtering each reference channel using at least one filter, each said filter being defined by one or more coefficients; and
combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said reference channel processor and said filters operate to maximize the signal to noise ration of the array output signal, wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
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36. A method for receiving a signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
generating a beamformer output by passing the outputs of said sensors through a delay and sum beamformer;
generating one or more reference channel signals by passing the outputs of said sensors through a reference channel processor;
filtering each reference channel using at least one filter, each said filter being defined by one or more coefficients; and
combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said reference channel processor and said filters operate to maximize the signal to noise ration of the array output signal, wherein said filter coefficients are adaptively determined so as to maximize the signal to noise ratio of the array output signal, and wherein upon the occurrence of a predetermined event the adaptive determination of said filter coefficients is stopped and said filter coefficients are faded into a predetermined set of fixed coefficients;
the fixed filter coefficients being determined by solving directly and non-adaptively an equation
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37. A sensor array for receiving a signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a plurality of filters for filtering the output of each sensor, each filter being defined by one or more filter coefficients; and
a means for combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are determined by solving an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter; and
wherein said noise covariance matrix is determined by defining a spatial distribution of noise sources;
defining a delay vector for each noise source using said spatial distribution, said delay vector expressing the relative times of arrival of the wavefront from said noise source at each sensor;
defining a steering vector for each said noise source based on said delay vector;
using said steering vector to determine the contribution of each noise source to said noise covariance matrix; and
generating said noise covariance matrix by adding the contributions of each noise source and a matrix indicative of spatially distributed white noise.- View Dependent Claims (38)
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39. An sensor array for receiving signal that includes a desired signal and noise, comprising:
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a plurality of sensors;
a delay and sum beamformer for combining the outputs of said sensors to generate a beamformer output;
a reference channel processor for combining the outputs of said sensors to generate one or more reference channel signals;
at least one filter for each said reference channel, each said filter being defined by one or more coefficients; and
means for combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said filter coefficients are determined by solving an equation - View Dependent Claims (40)
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41. A method of processing a received signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
filtering the output of each sensor through a filter, each filter being defined by one or more filter coefficients; and
combining the outputs of said filters to form a sensor array output signal;
wherein said filter coefficients are determined by solving an equation
where C is the noise covariance matrix, v is the steering vector toward the array look direction, and wopt is a vector having a number of components equal to the number of sensors, and where solving said equation for “
n”
frequencies provides “
n”
coefficients for each filter; and
wherein said noise covariance matrix is determined by defining a spatial distribution of noise sources;
defining a delay vector for each noise source using said spatial distribution, said delay vector expressing the relative times of arrival of the wavefront from said noise source at each sensor;
defining a steering vector for each said noise source based on said delay vector;
using said steering vector to determine the contribution of each noise source to said noise covariance matrix; and
generating said noise covariance matrix by adding the contributions of each noise source and a matrix indicative of spatially distributed white noise.- View Dependent Claims (42)
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43. A method of processing a received signal that includes a desired signal and noise, comprising the steps of:
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providing an array of sensors;
generating a beamformer output by passing the outputs of said sensors through a delay and sum beamformer;
generating one or more reference channel signals by passing the outputs of said sensors through a reference channel processor;
filtering each reference channel using at least one filter, each said filter being defined by one or more coefficients; and
combining the outputs of said filters with said beamformer output to generate a sensor array output signal;
wherein said filter coefficients are determined by solving an equation - View Dependent Claims (44)
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Specification