Ultrawideband Feed Array Coupling Mitigation for GRIN Lens Antennas
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Solution Overview
Problem
Switch-beam GRIN lens antennas require a wideband feed array that effectively mitigates element-to-element coupling to maintain efficiency and coverage across a wide bandwidth, as conventional methods fail to account for the strong coupling that occurs due to close element spacing.
Innovation Solution
Implementing a staggered frequency operation of array elements and embedding feed antennas in a high-refractive-index medium to reduce coupling, with impedance matching structures to maintain efficiency and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If feed array elements are spaced closely together to achieve compact antenna design, then the antenna size is reduced, but element-to-element coupling increases causing impedance bandwidth degradation
Solution Approach 1:
A dielectric substrate with refractive index n > 1 is introduced as an intermediary medium between feed array elements. This substrate reduces the wavelength of electromagnetic waves within the array region, thereby reducing the electrical spacing between elements and mitigating coupling effects while maintaining compact physical dimensions. The dielectric substrate acts as a mediator that transforms the interaction between closely-spaced elements.
Solution Approach 2:
The operating wavelength parameter is effectively changed by introducing the dielectric substrate. Since wavelength in a medium is λ = λ₀/n where n is the refractive index, the electrical spacing between elements is reduced by factor of n, thereby reducing coupling effects while maintaining the same physical spacing.
2Area of stationary object
If feed array elements are spaced closely together to achieve compact design, then the antenna footprint is reduced, but coupling between elements increases causing efficiency loss
Solution Approach 1:
The dielectric substrate serves as an intermediary that reduces electrical spacing between elements, thereby reducing coupling losses and improving radiation efficiency while maintaining compact footprint. The substrate material guides and confines electromagnetic energy, reducing power loss due to mutual coupling.
3Reliability
If conventional wideband antenna designs are used in array configuration, then individual element bandwidth is achieved, but element-to-element coupling degrades overall array performance
Solution Approach 1:
The dielectric substrate is positioned specifically in the region where array elements are located, creating an electromagnetic environment that reduces coupling between elements. This intermediary structure allows each element to maintain its wideband characteristics while the substrate mitigates the harmful coupling effects that would otherwise degrade overall array performance.
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 solutions effectively reduce element-to-element coupling, ensuring high efficiency and wide bandwidth operation by maintaining aperture efficiency and beamforming capabilities across the frequency range.
Implementation Method 1
embedding feed antennas in a high-refractive-index medium to reduce coupling
Implementation Method 2
The GRIN lens (100) collimates power radiated (102) quasi-spherically by the feed antenna (101) such that the output phase contours (103) have reduced curvature
Implementation Method 3
the material variation permits the inclusion of impedance matching structures (tapers) within the lens, allowing a wideband impedance match to free space
Data Source
AI summary
Wideband antenna elements exhibit strong coupling when formed into an array, which normally degrades the impedance bandwidth, radiation pattern, and efficiency of the feed antennas. Various methods are provided herein to mitigate or reduce this coupling. For example, designing an array such that not all antennas support the lower frequency operation mitigates coupling at low frequencies where coupling is most significant. Alternatively, embedding the feeds into a high-refractive-index medium increases the electrical distance between feeds while the physical separation is kept constant.