Method and apparatus for digital phased array imaging
First Claim
1. A method for digitally forming a beam of energy substantially focussed at a range R and at an angle θ
- with respect to a transducer array having a plurality N of transducers, each in a separate channel and receiving a portion of the energy of the beam, comprising the steps of;
(a) separately generating for each j-th channel, where 1≦
j≦
N, a stream of sampling strobe signals at a fixed common sample rate F;
(b) converting the amplitude of an analog signal from the transducer in each channel into a baseband data signal comprised of consecutive data words each responsive to one of said strobe signals;
(c) digitally processing only those baseband data signals converted, in the j-th channel, after a coarse time delay, determined by range R and angle θ and
unique to that channel, has elapsed after a start time to common to all N channels;
(d) phase rotating the baseband data signals in each channel by a fine time delay to obtain a total delay time in each channel predetermined by range R and angle θ
, and(e) coherently summing all N of the separately-delayed baseband data signal streams to obtain a single set of digital baseband data words representing at least amplitude information from the formed energy beam.
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Abstract
A method for generating a stream of digital data words, each representing an analog signal amplitude from a beam of vibratory energy received by a plurality N of transducers each associated with one of a like number of separate channels of a phased array, uses the steps of: sampling, after a delay of a multiple number of cycles at a fixed frequency F, an analog input signal in each channel at a fixed frequency F for conversion to a digital data word at each sample; then demodulating the digital data word stream in each channel to baseband and reducing the data word rate by a factor D; and phase-rotating the baseband data stream of each channel by a phase difference Δφ determined by the focal range R and steering angle θ to obtain, along both the sampling delay, a different channel time delay td,j, for each j-th channel, where 1≦j≦N, necessary to steer and focus the beam to a desired angle/range combination. Apparatus for generating the stream of digital data words is disclosed, and uses a special output-switching section in each channel to allow a pipelined coherent summation to be obtained across the entire phased transducer array.
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Citations
21 Claims
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1. A method for digitally forming a beam of energy substantially focussed at a range R and at an angle θ
- with respect to a transducer array having a plurality N of transducers, each in a separate channel and receiving a portion of the energy of the beam, comprising the steps of;
(a) separately generating for each j-th channel, where 1≦
j≦
N, a stream of sampling strobe signals at a fixed common sample rate F;(b) converting the amplitude of an analog signal from the transducer in each channel into a baseband data signal comprised of consecutive data words each responsive to one of said strobe signals; (c) digitally processing only those baseband data signals converted, in the j-th channel, after a coarse time delay, determined by range R and angle θ and
unique to that channel, has elapsed after a start time to common to all N channels;(d) phase rotating the baseband data signals in each channel by a fine time delay to obtain a total delay time in each channel predetermined by range R and angle θ
, and(e) coherently summing all N of the separately-delayed baseband data signal streams to obtain a single set of digital baseband data words representing at least amplitude information from the formed energy beam. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- with respect to a transducer array having a plurality N of transducers, each in a separate channel and receiving a portion of the energy of the beam, comprising the steps of;
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12. Apparatus for digitally forming a beam of energy substantially focussed at a range R and at an angle θ
- with respect to a transducer array having a plurality N of transducers, each in a separate channel and receiving a portion of the energy of the beam, comprising;
means for separately generating for each j-th channel, where 1≦
j≦
N, a stream of sampling strobe signals at a fixed common sample rate F,means for converting the amplitude of an analog signal from the transducer in each channel into a baseband data signal comprised of consecutive data words each responsive to one of said strobe signals; means for digitally processing only those baseband data signals converted, in the j-th channel, after a coarse time delay, determined by range R and angle θ and
unique to that channel, has elapsed after a start time to common to all N channels;means for phase rotating the baseband data signals in each channel by a fine time delay to obtain a total delay time in each channel predetermined by range R and angle θ
, andmeans for coherently summing all N of the separately-delayed baseband data signal streams to obtain a single set of digital baseband data words representing at least amplitude information from the formed energy beam. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
- with respect to a transducer array having a plurality N of transducers, each in a separate channel and receiving a portion of the energy of the beam, comprising;
Specification