Towed Sonar Array Defocusing via Virtual Source Beamformer
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Solution Overview
Problem
Towed sonar arrays face limitations in achieving 360-degree azimuthal coverage due to the naturally focused beamwidth of linear projector arrays, which restricts ping repetition rate and requires beam sweeping, making it challenging to insonify a full sector efficiently.
Innovation Solution
A control system modifies drive signals for each projector in a towed sonar array by applying amplitude and phase adjustments based on the distance to a virtual source, using beamformer coefficients to defocus the beampattern, allowing for broader sector coverage and dynamic beam steering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If beam sweeping is used to achieve 360-degree azimuthal coverage, then coverage area is improved, but ping repetition rate deteriorates
Solution Approach 1:
The patent applies dynamics by making the beamwidth adjustable rather than fixed. The system dynamically changes the effective aperture of the array to vary beamwidth, allowing the beam to be widened for faster sweeping across azimuth angles, thus improving ping repetition rate while maintaining coverage capability
Solution Approach 2:
The patent changes the physical parameter of beamwidth by modifying the phase and amplitude distribution across the array elements. By adjusting these parameters, the system can switch between narrow and wide beam patterns, resolving the contradiction between coverage area and ping repetition rate
2Measurement precision
If narrow focused beam is used, then measurement precision is improved, but sector coverage deteriorates
Solution Approach 1:
The system dynamically adjusts beamwidth based on operational requirements. When precise measurement is needed, the beam is focused narrow; when sector coverage is prioritized, the beam is widened, allowing the system to adapt between these two states
3Area of stationary object
If beam sweeping is implemented, then azimuthal coverage is improved, but time consumption deteriorates
Solution Approach 1:
The patent employs periodic pulsed operation where the array transmits acoustic pulses at high repetition rates. By using wide beam patterns during these pulses, the system covers large azimuthal sectors without requiring time-consuming continuous sweeping, thus reducing time loss
Data Source
AI summary
A method and towed sonic array system for defocusing the beampattern of the towed sonic array. The method includes determining an amplitude adjustment and a phase adjustment for each of the sonic projectors; and driving each of the sonic projectors with a drive signal modified by the amplitude adjustment and the phase adjustment for that sonic projector. The amplitude adjustment and phase adjustment for each of the sonic projectors are, at least in part, based upon the distance from that sonic projector to a virtual source. The location of the virtual source may be selected so as to achieve different beampatterns, including wide-sector beams and, in at least one case, a near-omni-directional beampattern. The drive signal may include multiple frequency components, in which case the method may be used to find a set of beamformer coefficients for each of the frequency components and an inverse transform may be used to realize a defocused driving signal.