Reciprocal Circular Polarization Selective Surface with Double Crankwire Elements
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Solution Overview
Problem
Existing circular polarization selective surfaces (CPSS) suffer from performance degradation under oblique incidence and are limited in volume, weight, and space due to their design, particularly in the Pierrot and Tilston types, and the CP-LP-CP cascade design has limited performance under oblique incidence and is thicker.
Innovation Solution
A CPSS comprising a 2D array of 2-fold rotationally symmetrical double crankwire elements with electromagnetic coupling between transverse segments of adjacent elements, forming a 2D array with a dielectric substrate and corrugated structure to enhance performance and reduce thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional CPSS design (Pierrot or Tilston type) is used, then the structure is simple to manufacture, but the performance degrades under oblique incidence and the volume/weight/space is excessive
Solution Approach 1:
The CPSS is divided into multiple unit cells, each containing two perpendicular crankwires oriented at 45 degrees to the principal axes. These segmented units are arranged in a periodic pattern to form the complete CPSS surface, allowing independent optimization of each unit while achieving overall performance improvement
Solution Approach 2:
The patent introduces a new dimensional configuration by orienting crankwires at 45 degrees to the x and y axes, creating a rotated coordinate system arrangement. This dimensional transformation allows the CPSS to maintain polarization selectivity while reducing sensitivity to oblique incidence angles and decreasing the required surface area
2Reliability
If the CP-LP-CP cascade design is used, then the theoretical polarization control is achieved, but the structure becomes thicker and performance is still limited under oblique incidence
Solution Approach 1:
The patent extracts and eliminates the intermediate linear polarization conversion layer from the traditional CP-LP-CP cascade structure. By using only circularly polarized crankwires directly, the design removes the unnecessary thickness contribution from the LP layer while maintaining the polarization selective function through the perpendicular crankwire arrangement
Solution Approach 2:
The CPSS employs asymmetric positioning of the two perpendicular crankwires within each unit cell, with specific orientations at 45 degrees to the axes. This asymmetric configuration creates different electromagnetic interactions for different polarization senses, achieving high polarization selectivity in a thin profile without requiring symmetric multi-layer structures
3Productivity
If traditional crankwire arrangements are used, then the manufacturing is straightforward, but the density and efficiency of the CPSS array is limited
Solution Approach 1:
Each unit cell in the CPSS serves multiple functions simultaneously: the two perpendicular crankwires work together to provide circular polarization selectivity, the 45-degree orientation provides oblique incidence robustness, and the periodic arrangement enables spatial filtering. This multi-functionality increases array efficiency without requiring additional separate components
Solution Approach 2:
The patent employs curved crankwire geometries with specific radius of curvature ratios to optimize the electromagnetic response. The curved shapes create more favorable current distributions and radiation patterns compared to straight-segment approximations, improving the polarization selectivity and reducing grating lobes while maintaining manufacturability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved performance under oblique incidence and reduces the physical size of the CPSS while maintaining effective circular polarization selectivity, enhancing the efficiency and density of the CPSS array.
Implementation Method 1
electromagnetic coupling between transverse segments of adjacent elements
Implementation Method 2
corrugated structure to enhance performance and reduce thickness
Data Source
AI summary
A reciprocal circular polarization selective surface (CPSS) is formed of two mutually orthogonal arrays of dipoles disposed at opposite transverse CPSS faces, with opposing orthogonal dipoles individually connected by transmission lines, wherein adjacent dipoles are EM coupled for enhancing CPSS performance. In one implementation, the CPSS comprises a two-dimensional array of double-crankwire elements each having a 2-fold rotational symmetry and composed of two separate crankwires of the same handedness, with the array elements positioned to impart EM coupling between adjacent array elements for enhanced performance at normal and oblique angles of incidence. Square-array and triangular-array CPSSs are disclosed.