Multilayer Signal Coupler Layout for Low-Loss High Directivity
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Solution Overview
Problem
Existing signal couplers, particularly those used in high frequency applications like microwave frequencies, face challenges in achieving a compact size with low insertion loss and high directivity, especially when using ¼ lambda transmission lines, which can result in large area occupation and high signal loss.
Innovation Solution
A signal coupler design utilizing a substrate with multiple layers, including a ground plane, where transmission lines are galvanically connected across layers and electromagnetically coupled through overlapping and spaced portions, employing both edge-coupled and broadside-coupled structures to achieve electromagnetic coupling, reducing size and loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ¼ lambda transmission lines are used in signal couplers, then coupling function is achieved, but area occupation increases and insertion loss increases
Solution Approach 1:
The patent transitions from planar transmission lines to three-dimensional multilayer stacked structures. The main transmission line and coupled transmission line are positioned in different layers vertically stacked, enabling coupling through electromagnetic field interaction across layers rather than requiring long lateral spacing. This dimensional change reduces the footprint area while maintaining coupling functionality.
Solution Approach 2:
The patent combines multiple transmission line segments from different layers into a unified coupled structure. The first transmission line in the first layer and the second transmission line in the second layer are galvanically connected through vias, merging their functions into a single compact coupler unit that achieves the desired coupling ratio without requiring large area.
2Area of stationary object
If compact size is reduced, then area occupation decreases, but achieving high directivity and low insertion loss becomes difficult
Solution Approach 1:
By utilizing vertical stacking of transmission lines in multiple layers, the patent achieves compact horizontal footprint while maintaining sufficient electromagnetic coupling length for high directivity. The vertical separation allows for optimized coupling distance without increasing lateral dimensions, preserving performance in a compact form factor.
Solution Approach 2:
The patent applies different coupling mechanisms at different locations: edge-coupled structures in some regions and broadside-coupled structures in others. This local differentiation allows optimization of specific coupling regions to achieve high directivity and low insertion loss while keeping the overall structure compact.
3Loss of energy
If edge-coupled and broadside-coupled structures are combined, then electromagnetic coupling is optimized, but device complexity increases
Solution Approach 1:
The patent implements both edge-coupled and broadside-coupled structures by utilizing the third dimension (vertical layering). The main transmission line spans multiple layers with galvanic connections via vias, creating edge-coupled regions where lines are laterally adjacent and broadside-coupled regions where lines face each other across layers. This vertical integration achieves multiple coupling modes without significantly increasing lateral complexity.
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 high coupler directivity and low insertion loss with a reduced size, suitable for high frequency signals, particularly microwave frequencies, by optimizing electromagnetic coupling through multilayered transmission line configurations.
Implementation Method 1
the main-transmission-line and the coupled-transmission-line are electromagnetically coupled to each other; at least part of the first-portion of the main-transmission-line is spaced apart from the coupled-transmission-line in the depth direction in order to provide electromagnetic coupling between the main-transmission-line and the coupled-transmission-line
Implementation Method 2
the main-transmission-line comprises a first-portion in the first layer, a second-portion in the second layer, and a third-portion in the third layer, wherein the first-portion, the second-portion and the third-portion are galvanically connected together
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A signal coupler (100) comprising: a main-transmission-line (114) that extends in a longitudinal direction within a substrate (102) between an input port and an output port; and a coupled-transmission-line (116) that extends in the longitudinal direction within the substrate (102) between a coupled port and a termination port. The coupled-transmission-line (116) is in a second layer (110). The main-transmission-line (114) comprises a first-portion (120) in a first layer (108), a second-portion (122) in a second layer (110), and a third-portion (124) in a third layer (112). At least part of the first-portion (120) is spaced apart from the coupled-transmission-line (116) in a depth direction. At least part of the second-portion (122) is spaced apart from the coupled-transmission-line (116) in the depth direction. At least part of the third-portion (124) is spaced apart from the coupled-transmission-line (116) in the depth direction.