Planar Inverted-L Tightly Coupled Arrays for Wide-Angle mmWave Scanning
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Solution Overview
Problem
Current ultra-wideband (UWB) millimeter wave communication systems face challenges with electromagnetic propagation due to free-space pathloss, atmospheric absorption, and scattering, limiting their performance in achieving high traffic capacities and link reliability at frequencies above 10 GHz.
Innovation Solution
The development of fully-planar inverted-L element (FILE) arrays, which are tightly coupled arrays (TCAs) that utilize an inverted-L shaped antenna element with a capacitively coupled via-fence, eliminating broadside nulls and resonances, and allowing operation up to 100 GHz with a 3:1 bandwidth and low profile, enabling efficient scanning and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional monopole antenna elements are used in tightly coupled arrays, then the array structure is simple and easy to manufacture, but broadside nulls and resonances occur that degrade radiation performance
Solution Approach 1:
The patent applies asymmetry by using an inverted-L shaped antenna element instead of a traditional symmetric monopole. The inverted-L configuration consists of a vertical segment and a horizontal segment that are unequal in length, creating an asymmetric structure that eliminates broadside nulls and resonances while maintaining manufacturing simplicity. This asymmetric geometry transforms the current distribution to eliminate the nulls in the broadside direction.
2Speed
If conventional antenna elements are used at millimeter wave frequencies above 70 GHz, then the operating frequency is limited, but the array profile becomes large and complex
Solution Approach 1:
The patent employs dimensionality change by transitioning from conventional three-dimensional antenna structures to a fully planar two-dimensional configuration. The inverted-L element lies entirely in the plane of the ground sheet, and the feed network is implemented as planar microstrip lines. This planarization enables scaling to millimeter wave frequencies above 70 GHz while maintaining a low-profile array structure without vertical complexity.
3Area of stationary object
If tightly coupled array elements are placed close together to reduce aperture size, then the array footprint is reduced, but electromagnetic coupling between elements increases causing performance degradation
Solution Approach 1:
The patent uses an intermediary approach by introducing a specific geometric configuration of the inverted-L element that acts as a mediator between closely spaced elements. The horizontal segment of the inverted-L element extends perpendicular to the array axis, creating an intermediate structure that reduces mutual coupling between adjacent elements. This configuration allows elements to be placed closer together while maintaining electromagnetic isolation through the carefully designed intermediate geometry.
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 FILE arrays achieve a voltage standing wave ratio (VSWR) of less than 3 for maximum scan angles of ±45° in all principal planes, significantly improving scanning ability and impedance bandwidth, making them suitable for high mmWave frequencies beyond 70 GHz.
Implementation Method 1
a capacitively coupled via-fence
Data Source
AI summary
Ultra-wideband (UWB) arrays that are fully planar are provided. Fully-planar inverted-L element (FILE) arrays that are tightly coupled arrays (TCAs) can realize UWB tightly coupled apertures in the W and higher millimeter wave (mmWave) bands. The unit cell architecture of the FILE array, (which can have any desired size, can be comprised of an inverted-L shaped antenna and a capacitively coupled via-fence.