Diffractive Dielectric Lens Antenna for Microwave Wavefront Shaping
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Solution Overview
Problem
Conventional lens antennas in the microwave range face challenges with bulkiness and weight due to thick refractive lenses, and existing diffractive lenses suffer from low diffraction efficiency and shadowing effects, especially at high numerical apertures, leading to unsatisfactory performance.
Innovation Solution
A lens antenna with a diffractive dielectric component featuring sub-wavelength microstructures arranged in zones to vary the effective refractive index quasi-monotonically, improving diffraction efficiency and reducing shading effects, while maintaining a compact form.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick refractive lenses are used to achieve high numerical aperture (low F/D ratio), then the focusing performance is improved, but the lens becomes bulky and heavy
Solution Approach 1:
The lens is divided into multiple discrete Fresnel zones with abrupt transitions between them, allowing the lens to achieve high numerical aperture with reduced thickness. The segmentation enables the lens to maintain focusing performance while reducing bulk and weight by eliminating the continuous thick structure of conventional refractive lenses.
Solution Approach 2:
The invention transitions from a three-dimensional thick refractive lens to a two-dimensional planar Fresnel lens structure. By moving the lens function to a planar geometry with concentric annular zones, the design achieves high numerical aperture without the bulk and weight of thick lenses.
2Volume of moving object
If Fresnel lenses with abrupt zone transitions are used to reduce thickness, then the lens becomes compact, but shadowing effects and diffraction losses increase
Solution Approach 1:
The invention modifies the geometric parameters of the Fresnel zones by introducing a curvature radius that is finite rather than infinite. This parameter change allows the zone edges to be rounded smoothly, reducing shadowing effects and diffraction losses while maintaining the compact thin-lens structure. The curvature radius is optimized to balance between reducing shadowing and maintaining the Fresnel lens functionality.
3Area of stationary object
If the F/D ratio is reduced to make the antenna more compact, then the numerical aperture increases, but the curvature on lens edges becomes very large making manufacturing complex
Solution Approach 1:
The lens is segmented into discrete Fresnel zones with defined inner and outer radii, transforming the continuous curved surface of a conventional lens into a stepped structure. This segmentation simplifies manufacturing by allowing the lens to be fabricated using layer-by-layer deposition or molding techniques, avoiding the need to machine complex continuous curvatures.
Solution Approach 2:
The invention introduces a finite curvature radius parameter for the Fresnel zones, which can be optimized during design. This parameter change allows the lens to accommodate low F/D ratios while maintaining manufacturable edge geometries, balancing compactness with ease of fabrication.
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 enhances diffraction efficiency and reduces losses by reflection, resulting in a more efficient and compact lens antenna design for the microwave range.
Implementation Method 1
a diffractive dielectric component capable of shaping a microwave wavefront
Implementation Method 2
sub-wavelength microstructures arranged in zones to vary the effective refractive index
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The antenna has a diffractive dielectric component (60) comprising main microstructures i.e. pillars (62), formed in a substrate material with a substrate refractive index to form an artificial material with an effective refractive index. The microstructures are arranged per zone to vary a surface filling level, where the effective refractive index is a function of the level. The microstructures are arranged such that the effective refractive index varies inside a zone of the component quasi monotonously between minimum and maximum values less than/equal to the substrate refractive index. The main microstructures have size smaller than target wavelength taken from a range of wavelengths.