Sparse Billboard And T-Shaped Arrays for 2D DOA With Low Mutual Coupling
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Solution Overview
Problem
Existing antenna array configurations for two-dimensional direction of arrival (DOA) estimation suffer from significant mutual coupling, leading to ambiguity and reduced accuracy, especially in applications where physical space and cost are limited.
Innovation Solution
The development of coprime, nested, and supernested sparse billboard and T-shaped antenna arrays, which employ a small number of closely separated sensors to reduce mutual coupling and achieve large degrees of freedom (DOF) through the use of fourth-order difference coarrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional 2D antenna arrays (URA, UCA, cross-shaped, L-shaped, hexagonal) are used for DOA estimation, then joint azimuth and elevation estimation is achieved, but significant mutual coupling occurs resulting in reduced accuracy
Solution Approach 1:
The patent divides the 2D array into multiple 1D sparse subarrays (e.g., three linear subarrays in billboard array, four subarrays in T-shaped array) arranged in specific geometric configurations. Each subarray is sparsely populated, and their collective arrangement creates a virtual 2D aperture that enables joint azimuth-elevation estimation while maintaining low mutual coupling within each subarray.
Solution Approach 2:
The patent transitions from 1D sparse arrays to 2D array configurations by arranging multiple 1D subarrays in geometric patterns (billboard, T-shaped, L-shaped). This dimensional expansion allows the system to estimate both azimuth and elevation angles simultaneously while preserving the sparse characteristics that minimize mutual coupling effects.
2Measurement precision
If many antennas are used to achieve greater accuracy in DOA estimation, then estimation precision is improved, but physical space requirements and cost increase
Solution Approach 1:
The patent employs nested array configurations where subarrays are positioned within a larger geometric structure. For example, the billboard array nests three linear subarrays in an L-shaped configuration with a common vertex, while the T-shaped array nests four subarrays in a T-configuration. This nesting allows efficient use of spatial aperture with fewer physical elements.
Solution Approach 2:
The patent changes the spatial distribution parameters of antenna elements from uniform dense packing to sparse non-uniform arrangements. By optimizing subarray spacings and configurations, the system achieves equivalent or superior DOA estimation accuracy with significantly reduced physical aperture compared to conventional uniform arrays.
3Area of stationary object
If array virtualization technique is used to create virtual arrays with larger number of antennas, then physical space and cost are reduced, but ambiguity in estimated DOA may occur
Solution Approach 1:
The patent employs asymmetric array configurations where subarrays have different lengths, spacings, or orientations. The billboard array uses three subarrays of potentially different configurations, and the T-shaped array uses four subarrays with asymmetric arrangement. This asymmetry breaks the symmetry-induced ambiguities that can occur in conventional uniform arrays while still achieving comprehensive 2D DOA coverage.
4Object-affected harmful factors
If linear sparse arrays are used to reduce mutual coupling, then robustness to mutual coupling is improved, but degrees of freedom and estimation capability are limited compared to 2D arrays
Solution Approach 1:
The patent merges multiple 1D sparse subarrays into a unified 2D array structure. Each subarray maintains its sparse characteristics for mutual coupling robustness, while their combined geometric arrangement provides the degrees of freedom necessary for 2D DOA estimation. The merging creates a system that achieves both 1D sparse array robustness and 2D array capability.
Data Source
AI summary
An antenna array for reception of radio waves includes a first leg aligned in a first direction, a second leg aligned in a second direction, a third leg, and a communication module. The elements of the first linear subarray are spaced by a first distance. The elements of the second linear subarray are spaced by a second distance. The first distance is not equal to the second distance. The second direction is orthogonal to the first direction. The third linear subarray is aligned in a third direction that is collinear to the first direction or at an angle of 45 degrees between the first direction and the second direction. The communication module receives the radio waves from the first leg, the second leg and the third leg and determines a two dimensional direction of the source of the radio waves.