Hybrid Coupler with Unwound-Rewound Spiral Geometry
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Solution Overview
Problem
Existing directional couplers face challenges in reducing overall size while maintaining performance symmetry and power handling capabilities, with conventional approaches like meandered line structures and inter-digital designs suffering from phase velocity imbalance and asymmetry.
Innovation Solution
A symmetrical hybrid coupler design featuring interdigitally coupled transmission lines with an unwound/rewound spiral configuration, where multiple transmission lines are vertically aligned and interconnected in a planar arrangement, achieving high coupling and improved power handling with reduced thermal resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional meandered line structures or inter-digital designs are used to reduce coupler size, then the device volume is reduced, but phase velocity imbalance and asymmetry occur leading to performance degradation
Solution Approach 1:
The patent applies asymmetry principle by using an unwound/rewound spiral configuration where the transmission lines are deliberately designed with non-uniform spacing - closer spacing in the unwound portion and wider spacing in the rewound portion. This controlled asymmetry compensates for phase velocity imbalances and maintains performance symmetry across the operating bandwidth while achieving compact size reduction.
Solution Approach 2:
The patent transitions from planar two-dimensional transmission line layouts to a three-dimensional spiral configuration. By winding the transmission lines in a spiral pattern with vertical alignment and interdigital coupling, the design achieves compact footprint reduction while maintaining proper phase relationships and coupling characteristics through the added dimensional complexity.
2Power
If transmission lines are placed in close proximity to achieve high coupling, then coupling factor is improved, but thermal resistivity increases and power handling capability decreases
Solution Approach 1:
The patent segments the coupling interaction into two distinct regions: an unwound portion with close spacing for strong coupling, and a rewound portion with wider spacing for thermal management. This segmentation allows the device to achieve high coupling factor in the unwound region while the rewound region provides thermal relief and power handling capability.
Solution Approach 2:
The patent applies local quality by varying the spacing between transmission lines at different locations along the spiral. The unwound portion has tight spacing optimized for coupling, while the rewound portion has wider spacing optimized for heat dissipation. This localized optimization of geometric parameters allows simultaneous achievement of high coupling and low thermal resistivity.
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 design achieves a 50% size reduction with similar insertion loss and enhanced power handling, maintaining symmetry and performance across a broad bandwidth, while improving thermal conductivity and reducing thermal resistivity.
Implementation Method 1
A directional coupler is a four port passive device that is used to combine, split and/or direct an RF signal within an RF circuit in a desired, predictable manner. A coupler can be implemented by placing two transmission lines in relatively close proximity to each other. Directional couplers operate in accordance with the principles of superposition and constructive/destructive interference of RF waves.
Implementation Method 2
The first transmission line and the N third transmission lines are interconnected between a first port and a second port. The first transmission line and the N third transmission lines are characterized by a predetermined planar arrangement that includes a plurality of geometric patterns. A second transmission line structure includes a second transmission line disposed in parallel with N fourth transmission lines. The second transmission line and the N fourth transmission lines are interconnected between a third port and a fourth port.
Data Source
AI summary
The present invention is directed to a hybrid coupler device that includes a first transmission line structure and a second transmission line structure. The first transmission line structure is interdigitally coupled with the second transmission line structure such that each transmission line in the second transmission line structure is disposed adjacent to a transmission line in the first transmission line structure. The coupling or the mutual capacitance Cd between the transmission lines of the present invention need not be equal; in fact, they all can be different.