Spiral Coupler External Port Accessibility
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Solution Overview
Problem
Existing spiral couplers, such as the Lange coupler, face challenges in reducing size, improving performance, and ensuring all ports are externally accessible while maintaining high isolation and directivity, especially in semiconductor and planar fabrication processes.
Innovation Solution
A spiral coupler design featuring parallel coextensive conductive strips in a planar spiral path with cross-over connections that bridge the strips from the inside to the outside, allowing all four ports to be external, and incorporating symmetrical configurations and interdigitated elements to achieve reduced size and enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional interdigitated strip line couplers are used, then coupling performance is achieved, but device size is large and ports are not all externally accessible
Solution Approach 1:
The patent transforms the traditional linear strip line configuration into a planar spiral geometry, utilizing two-dimensional spatial arrangement to achieve compact size while maintaining all four ports externally accessible. The spiral path allows ports to be positioned at the outer perimeter while the coupling action occurs along the spiral trajectory, effectively using dimensional transformation to resolve the contradiction between compact size and port accessibility.
Solution Approach 2:
The patent employs curved spiral paths instead of straight linear strips, creating a compact coiled structure that fits within a smaller area. The spiral curvature allows the transmission lines to be folded back on themselves multiple times, achieving the required electrical length and coupling performance within a reduced physical footprint while keeping all ports accessible at the outer perimeter.
2Area of stationary object
If strip spacing is reduced to achieve compact size, then device area is reduced, but isolation and directivity performance deteriorates
Solution Approach 1:
By transitioning from linear to spiral configuration, the patent maintains adequate spacing between adjacent spiral turns while achieving compact overall size. The spiral geometry distributes the coupling interaction along the curved path, allowing sufficient transverse separation between strips to maintain isolation and directivity performance without requiring excessively small spacing that would compromise performance.
Solution Approach 2:
The patent incorporates preliminary design of the spiral path geometry and cross-over connection locations to pre-establish optimal spacing relationships. By carefully planning the spiral trajectory and cross-over positions before fabrication, the design ensures that adequate spacing is maintained throughout the coupling region, preventing performance degradation while achieving compact dimensions.
3Ease of operation
If cross-over connections are added to make all ports external, then port accessibility is improved, but device complexity increases
Solution Approach 1:
The patent combines the cross-over connection function with the spiral path structure itself, rather than adding separate cross-over elements. The spiral configuration naturally creates the necessary crossings as part of its continuous path, integrating the port switching function into the main transmission line geometry and reducing overall structural complexity.
Solution Approach 2:
The spiral path serves multiple functions simultaneously: it provides the transmission line path, creates the necessary cross-overs for port accessibility, and establishes the coupling geometry. This multi-functionality reduces the need for separate dedicated cross-over structures, simplifying the overall device while achieving all four ports externally accessible.
Data Source
AI summary
An improved spiral coupler including a plurality of parallel, coextensive conductive strips disposed in a planar spiral path, including a first strip having an input port and a direct or through port, a second strip having a coupler port and an isolated port and a first cross-over connection for bridging the strips from the inside to the outside of the spiral path to provide all four the ports external access to the spiral path.