Frequency division beamforming for sonar arrays

An underwater sonar system comprising:

• an array of acoustic transducers;
• and
• a beamforming system that simultaneously associates signals with a range of frequencies to the transducers wherein a signal to a given transducer is phase shifted by a selected fixed amount relative to a signal assigned to the adjacent transducer, wherein the phase shifted signals with the range of frequencies form an acoustic signal with a range of directions, wherein a given direction within the range of directions corresponds to a specific frequency of the signals within the range of frequencies.

A method of using an underwater sonar system having an array of acoustic transducers, the method comprising:

• associating signals having a frequency component to the transducers wherein a signal associated with a given transducer is phase shifted by a selected fixed amount relative to a signal assigned to the adjacent transducer such that the phase shifted signals form an acoustic beam having a direction;
• and
• controlling the directionality of the acoustic beam by manipulating the frequency component of the signals.

A method of scanning an angular sector underwater using an array of acoustic transducers, the method comprising:

• forming a plurality of acoustic beams wherein each acoustic beam is formed by associating signals to the array of acoustic transducers such that a signal associated with a given transducer is phase shifted by a selected fixed amount relative to a signal assigned to the adjacent transducer and wherein the direction of each acoustic beam depends on the frequency of the signals;
• and
• varying the frequency of signals corresponding to each acoustic beam so as to vary the direction of the acoustic beam, thereby allowing the acoustic beam to sweep a range of direction angles and wherein the frequency is selected for each acoustic beam such that resulting ranges of direction angles cover the angular sector.

A sonar system for forming a steerable underwater acoustic beams, the system comprising:

• an array of acoustic transducers;
• and
• a beamforming system that associates a signal to each of the transducers to form an acoustic beam with a direction wherein the signal is phase-shifted by a selected phase relative to a signal assigned to the adjacent transducer and wherein the direction of the acoustic beam is determined by a combination of the phase and the frequency of the signals, wherein the beamforming system is adapted to vary the frequency of the signals for a given phase so as to permit steering of the acoustic beam.

A method of using an underwater sonar system having an array of acoustic transducers, the method comprising:

• associating signals having a frequency component and a phase component to the transducers wherein a signal associated with a given transducer is phase-shifted by a selected phase relative to a signal assigned to the adjacent transducer;
• and
• controlling the directionality of the acoustic signal by selecting a first direction of the acoustic signal as determined by the selected phase and varying the direction of the acoustic beam about the first direction by manipulating the frequency component of the signals.