Truncated Conical Acoustic Array for Constant Beam Width
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Solution Overview
Problem
Existing directional acoustic transducers and arrays have frequency-dependent beam patterns, leading to varying spectral content and fidelity issues, and prior solutions sacrifice side lobe and null management for constant beam width, limiting their application in sonar and acoustic systems.
Innovation Solution
A method for designing a broadband constant beam width acoustic array using a shading function with user-specified parameters, calculated using Legendre polynomial orders, allowing for truncation at null bearing locations to maintain beam width across a broad frequency range, utilizing a conical spherical array with amplification and attenuation adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a spherical or hemispherical array is used with shading function to achieve constant beam width over broad frequency range, then beam width consistency is improved, but array size and weight increase
Solution Approach 1:
The spherical array is segmented into a conical subset of elements, retaining only those elements that contribute to the desired beam pattern within the conical angle. This segmentation reduces the total number of elements while maintaining the constant beam width property, thereby reducing array weight without sacrificing beam width consistency.
Solution Approach 2:
The invention extracts the essential functional elements from the full spherical array by selecting only the conical subset of transducers that are necessary to generate the desired beam pattern. This extraction approach maintains the constant beam width characteristic while eliminating unnecessary elements that would increase array weight.
2Stability of the object's composition
If Legendre polynomial shading function is used to create constant beam pattern, then beam width is maintained constant, but side lobe and null control is sacrificed
Solution Approach 1:
The invention applies local quality by designing the conical array to have different functional characteristics in different spatial regions. The conical geometry naturally creates a main lobe in the desired direction while the truncated edges produce controlled side lobes and nulls at specific angular positions, allowing simultaneous optimization of beam width constancy and side lobe management.
Solution Approach 2:
The invention transitions from a two-dimensional spherical surface to a three-dimensional conical geometry. This dimensional change allows the array to exploit the conical shape's inherent properties to control beam pattern characteristics, achieving both constant beam width and improved side lobe/null control through the conical truncation geometry.
3Length of moving object
If high degree Legendre polynomial is used to achieve narrower beam width, then beam width is reduced, but array complexity and computational requirements increase
Solution Approach 1:
The invention applies partial action by using a finite number of conical elements rather than a complete spherical array. This partial sampling of the spherical geometry provides sufficient beam width control without requiring the full complexity of high-degree Legendre polynomial expansions, achieving narrow beam width with reduced array complexity.
Data Source
AI summary
A method is given for a broadband constant beam width acoustic array using shading function parameters for a three dimensional axially symmetric beam. Coefficients are calculated for an estimated shading function fitting the parameters that is a summation of Legendre polynomial orders. The number of orders is user specified. Null bearing locations can be determined from the parameters or from the shading function. A constant beam width shading function can be created from these parameters and used as amplifications and attenuations for a conical spherical array of transducers. The array can be truncated at the null bearing locations. The estimated shading function can be further refined by provided additional Legendre polynomial orders.