US4983970A
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Method and apparatus for digital phased array imaging
Assignee: General Electric Co
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Filing: 1990-03-28
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Granted: 1991-01-08
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Expires: 2010-03-28
Abstract
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 t d ,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.
Inventors
- 👤 Matthew O'Donnell
- 👤 William E. Engeler
- 👤 John J. Bloomer
- 👤 John T. Pedicone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 09:51
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/52; G01S7/52017; G01S7/52046; G10; G10K; G10K11/00; G10K11/18; G10K11/26; G10K11/34; G10K11/341; G10K11/346
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
211 words
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.
Claim 2
Independent Claim
211 words
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.
Claim 3
Dependent Claim
53 words
The method of claim 1, wherein step (b) includes the step of continuously converting the analog signal amplitude responsive to a continuous stream of strobe signals; and step (c) includes the step of ignoring all baseband data signals in the j-th channel until the coarse time delay for that j-th channel has elapsed.
Claim 4
Dependent Claim
35 words
The method of claim 1, wherein step (d) comprises the step of performing a CORDIC multiplication of each baseband data signal word by a digital word Δφ selected to provide the predetermined fine time delay.
Claim 5
Dependent Claim
86 words
The method of claim 1, wherein step (a) includes the step of providing a continuous clock signal at the fixed common rate F; and step (c) includes the steps of: calculating for each j-th channel a total channel delay time t d ,j ; calculating a greatest integer number of clock signal half-cycles which is not more than one half-cycle removed from the total delay time; and setting the j-th channel coarse time delay t' d ,j to contain that integer number of clock signal half-cycles.
Claim 6
Dependent Claim
47 words
The method of claim 4, wherein the total channel delay time includes a steering component (X j /V)sinθ, wherein X j is the position of the j-th transducer with respect to the center of the array and V is a velocity of energy in a propagation medium.
Claim 7
Dependent Claim
22 words
The method of claim 5, wherein the total channel delay time also includes a focusing component X j 2 /2RV)cos 2 θ.
Claim 8
Dependent Claim
35 words
The method of claim 6, wherein step (d) comprises the step of performing a CORDIC rotation of each baseband data signal word by a digital word Δφ selected to provide the predetermined fine time delay.
Claim 9
Dependent Claim
35 words
The method of claim 5, wherein step (d) comprises the step of performing a CORDIC rotation of each baseband data signal word by a digital word Δφ selected to provide the predetermined fine time delay.
Claim 10
Dependent Claim
35 words
The method of claim 4, wherein step (d) comprises the step of performing a CORDIC rotation of each baseband data signal word by a digital word Δφ selected to provide the predetermined fine time delay.
Claim 11
Dependent Claim
37 words
The method of claim 1, wherein step (e) includes the step of delaying the phase-rotated data words of each channel by a time interval sufficient to cause all like-numbered data signals to substantially simultaneously appear for summation.
Claim 12
Dependent Claim
68 words
The method of claim 10, wherein the delaying step includes the steps of: delaying the phase-rotated data words in each channel by one clock time interval; adding the delayed rotating data word to data received from another channel to obtain sum data; and providing the sum data to a channel in an opposite direction in the array, from the another channel, until all channel data is pipelined summed.
Claim 13
Dependent Claim
213 words
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 t o 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, and means 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.
Claim 14
Dependent Claim
213 words
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 t o 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, and means 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.
Claim 15
Dependent Claim
40 words
The apparatus of claim 12, wherein the generating means provides a continuous stream of strobe signals; and the processing means ignores all baseband data signals in the j-th channel until the coarse time delay for that j-th channel has elapsed.
Claim 16
Dependent Claim
33 words
The apparatus of claim 12, wherein said rotating means comprises means for CORDIC multiplication of each baseband data signal word by a digital word Δφ selected to provide the predetermined fine time delay.
Claim 17
Dependent Claim
82 words
The apparatus of claim 12, wherein said generating means receives a clock signal at the fixed common rate F, and comprises: means for calculating for each j-th channel (a) a total channel delay time t d ,j, and (b) a greatest integer number of clock signal half-cycles which is not more than one half-cycle removed from the total delay time;, and means for setting the j-th channel coarse time delay t' d ,j to contain that integer number of clock signal half-cycles.
Claim 18
Dependent Claim
51 words
The apparatus of claim 15, wherein said converting means includes: ADC means for converting the amplitude of said channel analog signal to a data word at each strobe signal at said fixed rate F once said strobe signals commence; and means for demodulating a stream of said data words to baseband.
Claim 19
Dependent Claim
24 words
The apparatus of claim 16, wherein said converting means also includes means or decimating the data word stream by a preselected decimation factor D.
Claim 20
Dependent Claim
27 words
The apparatus of claim 16, wherein said converting means also includes FIFO means for temporarily storing the stream of baseband data words for a commanded time interval.
Claim 21
Dependent Claim
37 words
The apparatus of claim 12, wherein the summing means includes means for delaying the phase-rotated data words of each channel by a time interval sufficient to cause all like-numbered data signals to substantially simultaneously appear for summation.
Claim 22
Dependent Claim
69 words
The apparatus of claim 19, wherein the delaying means includes: means for delaying the phase-rotated data words in each channel by one clock time interval; means for adding the delayed rotating data word to data received from another channel to obtain sum data; and providing the sum data to a channel in an opposite direction in the array, from the another channel, until all channel data is pipelined summed.
Claim 23
Dependent Claim
48 words
The apparatus of claim 20, wherein said providing means includes gating means for steering incoming data from a selected one of an immediately-previous channel or an immediately-next channel to a summing means input and for steering sum data to a remaining one of the immediately-previous and immediately-next channels.
References Cited (Backward Citations)
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