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US 6,847,588 B1Granted
Method for changing the frequency for sampling sonar wavefronts
AssigneeL-3 Communications Corporation
InventorsGeorge Wallace, Paul Greene
Life of this patent
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Abstract
A system and method for processing sonar information from an underwater hydrophone array, at frequencies having wavelengths less than two times a spacing between adjacent hydrophones. The method and system all for processing received underwater waveforms at high frequency limits beyond the mechanical limits of the array.
Claims14
A method for processing sonar information from an underwater hydrophone array, which array has a known spacing between adjacent hydrophones, at frequencies having wavelengths less than two times a spacing between adjacent hydrophones, the method comprising:
- a) providing an underwater hydrophone array comprising a plurality of receiver hydrophones, which array has a known length and known spacing between adjacent hydrophones, wherein λDU is the upper design wavelength for the design upper frequency limit fDU for the array;
- b) providing forward motion for the hydrophone array underwater with a vessel at a velocity of the hydrophone array in water VS;
- c) selecting a synthetic upper frequency fSU, wherein the synthetic upper frequency is equal to or greater than the frequency of a signal to be measured;
- d) defining a synthetic hydrophone spacing ΔdSU, wherein the synthetic hydrophone spacing is equal to λSU/2 wherein λSU is the wavelength for the synthetic upper frequency fSU for the array;
- e) determining the time interval for the hydrophones to travel the distance of the synthetic hydrophone spacing;
- f) calculating the number of sonar signal wavefronts predicted to be encountered by each hydrophone in the time interval for the hydrophones to travel the distance of the synthetic hydrophone spacing;
- g) selecting a telemetry sampling rate for the predicted number of sonar wavefronts, wherein the telemetry sampling rate is selected such that each wavefront is sampled more than once;
- h) detecting samples of a first sonar wavefront with each of the hydrophones at a time t0 and summing and recording the samples at time t0 with a beamformer to provide a plurality of beam sets at a time t0;
- i) detecting samples of N subsequent sonar wavefronts with each of the hydrophones at ≧2N equally spaced times in a time interval Δt;
- summing and recording the samples from each of the hydrophones with a beamformer to provide beam sets for the number of samples taken in the time interval Δt;
- and
- j) combining the beam sets into an assembly of beams at a time t1=t0+Δt.
9 more elements
A system for processing sonar information from an underwater hydrophone array, which array has a known spacing between adjacent hydrophones, at frequencies having wavelengths less than two times a spacing between adjacent hydrophones, comprising:
- a) an underwater hydrophone array comprising a plurality of receiver hydrophones, which array has a known length and known spacing between adjacent hydrophones, wherein λDU is the upper design wavelength for the design upper frequency limit fDU for the array;
- b) a driver for providing forward motion for the hydrophone array underwater at a velocity of the hydrophone array in water VS;
- c) an arrangement for selecting a synthetic upper frequency fSU, wherein the synthetic upper frequency is equal to or greater than the frequency of a signal to be measured;
- d) an instrumentality for defining a synthetic hydrophone spacing ΔdSU, wherein the synthetic hydrophone spacing is equal to λSU/2 wherein λSU is the wavelength for the synthetic upper frequency fSU for the array;
- e) an implement for determining the time interval for the hydrophones to travel the distance of the synthetic hydrophone spacing;
- f) a calculator for calculating the number of sonar signal wavefronts predicted to be encountered by each hydrophone in the time interval for the hydrophones to travel the distance of the synthetic hydrophone spacing;
- g) a sampler for selecting a telemetry sampling rate for the predicted number of sonar wavefronts, wherein the telemetry sampling rate is selected such that each wavefront is sampled more than once;
- h) a detector for detecting samples of a first sonar wavefront with each of the hydrophones at a time t0 and summing and recording the samples at time t0 with a beamformer to provide a plurality of beam sets at a time t0;
- and for detecting samples of N subsequent sonar wavefronts with each of the hydrophones at ≧2N equally spaced times in a time interval Δt;
- and for summing and recording the samples from each of the hydrophones with a beamformer to provide beam sets for the number of samples taken in the time interval Δt;
- and
- i) a combiner for combining the beam sets into an assembly of beams at a time t1=t0+Δt.
9 more elements
Dependencies are inferred from the claim text.