Convex Phased Array for Grating Lobe Elimination
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Solution Overview
Problem
Sparse phased arrays, which reduce the number of antenna elements to lower costs, suffer from grating sidelobes that cause ghosting phenomena, and existing post-processing remedies are either computationally expensive or scene-dependent, making them impractical for real-time use in dynamic environments.
Innovation Solution
Restricting the maximum scan angle to less than π/2 radians and forming the array into a convex shape such as a paraboloid or ellipsoid, allowing for less dense element spacing without grating lobes, enabling efficient scanning in limited solid angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of antenna elements is reduced to lower costs, then device complexity and cost are reduced, but grating sidelobes appear causing ghosting phenomena
Solution Approach 1:
The patent applies curvature by forming the phased array into a convex shape (cylindrical, spherical, ellipsoidal, or paraboloid form) rather than using a flat array. This curved geometry fundamentally changes the wave interference patterns, eliminating grating sidelobes while allowing reduced element spacing greater than λ/2. The curvature causes reflected waves to converge properly without creating the pathological interference patterns that produce ghosting in flat sparse arrays.
Solution Approach 2:
The patent changes the geometric parameter of the array from a flat planar configuration to a convex three-dimensional shape. This parameter change in the array geometry transforms the radiation pattern characteristics, allowing the system to achieve sidelobe-free operation with fewer elements. The convex form factor and restricted scan angles work together to modify the wave propagation characteristics and eliminate grating lobes.
2Device complexity
If element spacing is increased to reduce array density, then device complexity is reduced, but grating lobes are created at different angles
Solution Approach 1:
The convex curved geometry of the array allows elements to be spaced at distances greater than λ/2 without creating grating lobes. The curvature ensures that waves from sparsely spaced elements arrive at scan angles within the restricted range (-π/2 < θ < π/2) in phase, preventing the formation of unwanted lobes. This geometric transformation fundamentally alters the interference conditions compared to flat arrays.
Solution Approach 2:
The patent transitions from a two-dimensional planar array to a three-dimensional convex structure. By adding the dimensional aspect of curvature, the system can accommodate larger element spacing while maintaining proper wave interference patterns. The third dimension (curvature radius) provides an additional degree of freedom to control phase relationships and eliminate grating lobes.
3Measurement precision
If post-processing deconvolution algorithms are applied to remove ghosting, then image reconstruction quality is improved, but computational time increases significantly
Solution Approach 1:
The patent eliminates the source of ghosting (grating sidelobes) through the convex array geometry before scanning begins, rather than attempting to remove ghosting through post-processing after data collection. This preliminary geometric configuration prevents the formation of problematic interference patterns, allowing real-time imaging without computationally intensive deconvolution algorithms.
Solution Approach 2:
The patent converts the potential harm of sparse array grating lobes into a benefit by using the same sparsity advantage while eliminating the harmful interference through convex geometry. The restricted scan angle regime combined with convex shaping transforms what would be problematic grating lobe directions into useful main lobe directions, turning the sparse array's weakness into a strength.
Data Source
AI summary
Grating lobe free scanning in a phased array with sparse element spacing is obtained by restricting the maximum scan angle for elements in the array, and arranging the elements in a convex form. One convex form is a paraboloid, which may be continuous, or piecewise in nature, tiled with flat segments.