Capacitive Shielded Coupled Lines for Bend Transition Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transmission-line designs face challenges in maintaining equal even and odd mode velocities during coupling transitions, especially in compact designs with bends, where magnetic coupling is strongly affected, leading to impedance mismatches and reduced directivity.
Innovation Solution
A planar transmission-line assembly with a shield conductor is used to transition between coupled and uncoupled sections, where the shield conductor intercepts capacitive fields and reduces cross-conductor capacitance, maintaining even mode impedance without affecting magnetic coupling, and the conductors' widths are adjusted to compensate for added capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If bends are introduced in coupled planar transmission lines for compact design, then the size of the coupler is reduced, but magnetic coupling is strongly affected and even mode impedance changes more than odd mode impedance
Solution Approach 1:
A shield conductor is introduced as an intermediary element between the coupled transmission lines. This shield conductor intercepts capacitive fields and reduces cross-conductor capacitance, thereby compensating for the impedance changes caused by bends. The shield conductor acts as a mediator that restores the balance between even and odd mode velocities without requiring the transmission lines to be straight.
2Manufacturing precision
If the shield conductor is added to maintain even mode impedance, then impedance matching is improved, but device complexity increases
Solution Approach 1:
The widths of the transmission conductors are adjusted as a compensatory parameter. By modifying the conductor widths, the added capacitance from the shield conductor is compensated, maintaining the desired even mode impedance. This parameter adjustment allows the system to achieve impedance matching while managing the complexity introduced by the shield conductor.
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
This solution allows for a seamless transition between coupled and uncoupled sections with minimal impact on magnetic coupling, maintaining high directivity and impedance matching, thereby enhancing the performance of transmission-line couplers.
Implementation Method 1
the shield conductor intercepts capacitive fields and reduces cross-conductor capacitance
Implementation Method 2
The shield conductor is coplanar with, spaced from, adjacent to, and extends along the first transmission conductor in the intermediate section, whereby the shield conductor is edge-coupled to the first transmission conductor
Implementation Method 3
magnetic coupling is strongly affected by the bends
Implementation Method 4
Two conductive lines are coupled when they are spaced apart, but spaced closely enough together for energy flowing in one to be induced in the other
Data Source
AI summary
A transmission-line assembly provides a transition between more coupled and less coupled transmission lines. The more coupled transmission lines may be configured as a dual stripline, and the less coupled transmission lines may be configured as separate striplines or a dual stripline with reduced coupling. In an intermediate section, the transmission conductors transition between the more coupled and less coupled sections and at least one transmission conductor bends. A grounded shield conductor is coplanar with and edge-coupled to the one transmission conductor and extends along the bend in the one transmission conductor. The shield conductor is not connected to either of the transmission conductors, and overlaps the other transmission conductor when viewed normal to the planes of the transmission conductors, whereby the shield conductor is broadside coupled to the other transmission conductor. Capacitive coupling between the transmission conductors and the shield conductor reduce capacitive coupling between the transmission conductors.