Directional Coupler Symmetric Sub-line Switching for Directivity
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Solution Overview
Problem
Existing directional couplers face challenges in achieving stable detection accuracy due to differences in directivity between forward and reverse signal detection, resulting from uneven coupling between main and sub-lines.
Innovation Solution
A directional coupler design featuring a substrate with a main line and sub-lines, where the sub-lines are formed symmetrically with respect to the main line, and a switch that adjusts connections among sub-line end portions, ensuring that the sub-line connected to detection output terminals is overlapped or surrounded by other sub-lines, thereby reducing directivity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sub-lines are connected asymmetrically to the main line, then the coupling degree can be adjusted, but the directivity in forward and reverse signal detection becomes different
Solution Approach 1:
The patent applies asymmetry in a controlled manner by making the sub-line configuration asymmetric with respect to the main line, while maintaining overall symmetry in the coupling structure. This allows adjustment of coupling degrees while preserving uniform directivity through the symmetric arrangement of equivalent coupling sections.
Solution Approach 2:
The sub-lines are divided into multiple sections with different coupling characteristics. By segmenting the sub-lines into first and second sub-lines with different lengths and coupling degrees, the patent achieves adjustable overall coupling while maintaining symmetric interaction with the main line, thus resolving the contradiction between adaptability and measurement precision.
2Device complexity
If the sub-line configuration is simplified, then the device complexity is reduced, but the uniformity of directivity in signal detection deteriorates
Solution Approach 1:
The patent segments the sub-line structure into multiple manageable sections (first sub-line and second sub-line) with specific functional roles. This segmentation allows for a systematic configuration that achieves directivity uniformity through symmetric coupling while keeping the overall structure relatively simple and manageable.
3Adaptability or versatility
If the sub-lines are made of different lengths, then the coupling degree can be adjusted for different frequency bands, but the symmetry with respect to the main line is broken
Solution Approach 1:
The patent strategically applies asymmetry by making the sub-lines of different lengths (first sub-line longer than second sub-line) while positioning them symmetrically with respect to the main line. This creates a balanced asymmetric configuration that achieves frequency band adaptability while maintaining overall structural symmetry for uniform directivity.
Solution Approach 2:
The patent resolves the symmetry conflict by transitioning from one-dimensional length comparison to two-dimensional spatial arrangement. The sub-lines are positioned at different locations symmetrically with respect to the main line, allowing different lengths while maintaining overall symmetry in the coupling structure.
Data Source
AI summary
A directional coupler (1) includes a substrate (10), a main line (20) formed directly or indirectly on the substrate (10), sub-lines (21, 22 and 23) at least part of each of which is formed directly or indirectly on the substrate (10) along the main line (20), a switch (30) switching connections among end portions of the plurality of sub-lines (21, 22 and 23), and detection output terminals (FWD and REV) connected to the sub-line (21), wherein, when looking at the substrate (10) in plan, the end portions of the sub-lines (21, 22 and 23) are disposed on the opposite side to the detection output terminals (FWD and REV) relative to the main line (20), and the sub-line (21) to which the detection output terminals (FWD and REV) are connected is overlapped with or surrounded by the sub-lines (22 and 23).