Multilayer PCB Directional Coupler for Compact RF Isolation
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Solution Overview
Problem
Conventional directional couplers occupy significant internal space in electronic devices, hinder miniaturization and integration, and can compromise communication performance due to insufficient isolation.
Innovation Solution
A directional coupler is embedded within a multilayer printed circuit board, comprising conductive layers with capacitive and inductive elements, forming part of the board structure to reduce spatial occupancy and enhance isolation and insertion loss characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the directional coupler is mounted on the surface of the board, then the coupler is easy to install and maintain, but it occupies significant internal space of the electronic device
Solution Approach 1:
The patent merges the directional coupler with the printed circuit board by embedding it within the board's multilayer structure. The coupler's conductive plates, capacitive elements, and inductive elements are integrated into different layers of the PCB, making the coupler an inherent part of the board rather than a separate mounted component. This eliminates the need for additional mounting space while maintaining functionality.
Solution Approach 2:
The patent transitions the coupler from a two-dimensional surface mounting approach to a three-dimensional embedded structure within the multilayer board. By utilizing the vertical dimension (Z-axis) through multiple board layers, the coupler occupies internal volume rather than surface area, effectively moving the solution from 2D to 3D space utilization.
2Measurement precision
If a shield can is added to protect the directional coupler from electromagnetic influence, then sampling accuracy is improved, but internal space is further reduced
Solution Approach 1:
The patent combines the shielding function with the existing PCB ground layers and conductive structures. The multilayer board's ground planes and conductive traces serve dual purposes: electrical connectivity and electromagnetic shielding. This integration eliminates the need for separate shield cans while maintaining electromagnetic compatibility and sampling accuracy.
Solution Approach 2:
The patent makes the PCB's conductive structures serve multiple functions: signal transmission, power distribution, and electromagnetic shielding. The ground layers and conductive planes that are already part of the board structure are utilized for shielding purposes, eliminating the need for dedicated shielding components and reducing overall device volume.
3Ease of manufacture
If passive elements such as capacitor or inductor are installed on the board, then the directional coupler can be assembled, but it occupies considerable internal space
Solution Approach 1:
The patent merges the passive elements (capacitors and inductors) directly into the PCB structure. Capacitive elements are formed by overlapping conductive plates on adjacent layers, while inductive elements are created using wound conductive lines on the board. This integration eliminates the need for separate discrete passive components and their associated mounting space.
Solution Approach 2:
The patent replaces mechanical/passive components with electromagnetic field-based structures formed by conductive patterns on the PCB. Instead of using physical capacitors and inductors that occupy space, the patent uses conductive geometries that create the necessary electrical properties through electromagnetic field distribution across the board layers.
4Device complexity
If isolation is not sufficiently secured in the directional coupler, then the structure is simpler, but communication performance is compromised
Solution Approach 1:
The patent combines multiple isolation mechanisms within the integrated structure: electromagnetic coupling through controlled impedance traces, shielding via ground planes, and directional signal routing through the coupled-line geometry. These combined effects achieve high isolation without requiring additional separate isolation components or complex structures.
Solution Approach 2:
The patent uses the PCB's dielectric material and ground planes as intermediary elements to provide isolation between different signal paths. The controlled impedance traces and ground structures act as mediators that enable signal transmission while maintaining electrical isolation, achieving both performance and integration.
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 embedded directional coupler reduces space usage, enhances durability, and provides excellent isolation and wideband support, ensuring efficient communication performance.
Implementation Method 1
The at least one conductive portion of the first layer and the at least one conductive plate of the second layer are configured to operate as a capacitor
Implementation Method 2
a fourth layer disposed adjacent to the third layer in the first direction and configured to include a conductive line that is wound with at least one turn and that is configured to operate as an inductor
Implementation Method 3
The at least one RF signal transmission line of the third layer at least partly overlaps the at least one conductive plate of the second layer, provides an RF in/out line including an RF input port and an RF output port, and is configured to be electro-magnetically coupled to the capacitor and the inductor
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A directional coupler according to various embodiment and an electronic device having the same are provided. The directional coupler includes a first layer having at least one conductive portion, a second layer disposed adjacent to the first layer in a first direction and having at least one conductive plate corresponding to the conductive portion of the first layer, a third layer disposed adjacent to the second layer in the first direction and including an RF signal transmission line, a fourth layer disposed adjacent to the third layer in the first direction and having a conductive line wound with at least one turn, and at least one conductive via electrically connecting the at least one conductive plate of the second layer and the conductive line of the fourth layer which is wound with at least one turn.