RF Inductive Coupler With Vertically Offset Spiral Inductors
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Solution Overview
Problem
Current RF couplers face challenges in reducing costs while simplifying fabrication processes while maintaining effective RF signal coupling and directionality, especially in advanced wireless applications.
Innovation Solution
A high directivity RF coupler design featuring two spiral inductors with weak electromagnetic coupling and series capacitors resonating with the self-inductance at a desired frequency, configured to provide a high directivity RF signal coupling with distinct output ports for direct, coupled, and isolated signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional RF coupler designs are used, then effective RF signal coupling and directionality are achieved, but costs increase and fabrication processes become complex
Solution Approach 1:
The RF coupler is segmented into distinct functional regions: a first spiral inductor for receiving signals, a second spiral inductor for coupled signals, and isolated regions. This segmentation allows each component to be optimized independently while simplifying the overall fabrication process through modular design approaches.
Solution Approach 2:
The patent transitions from planar spiral inductors to three-dimensional vertically-coupled inductor structures. The first and second spiral inductors are positioned at different vertical levels with vertical coupling elements connecting them, enabling effective RF signal coupling while maintaining a compact footprint and simplifying planar fabrication processes.
2Reliability
If traditional RF coupler designs are used, then effective RF signal coupling and directionality are achieved, but costs increase
Solution Approach 1:
The vertically-coupled inductor structure serves multiple functions simultaneously: it provides RF signal coupling, achieves signal isolation through vertical positioning, and enables compact integration. This multi-functionality reduces the need for additional components and assembly steps, thereby lowering manufacturing costs.
Solution Approach 2:
The patent merges the coupling and isolation functions into a single integrated vertically-coupled inductor structure. The first and second spiral inductors with vertical coupling elements combine signal coupling and spatial isolation in one component, reducing part count and assembly complexity, which directly lowers manufacturing costs.
3Manufacturing precision
If spiral inductors with weak electromagnetic coupling are used, then high directivity is achieved, but device area increases
Solution Approach 1:
The patent achieves weak electromagnetic coupling with high directivity by positioning spiral inductors in three-dimensional space at different vertical levels rather than placing them side-by-side in the planar domain. The vertical separation reduces magnetic field overlap while maintaining compact planar footprint, effectively trading vertical for horizontal space.
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 effective RF signal coupling and directionality with reduced costs and simplified fabrication, as demonstrated by simulated S-parameter results showing approximately 26 dB directivity at 3.5 GHz, suitable for various wireless applications.
Implementation Method 1
two spiral inductors which are weakly electromagnetically coupled (K«1)
Implementation Method 2
Values of the series capacitors are selected to resonate with the self-inductance of each inductor at a desired operating frequency
Data Source
AI summary
A reference circuit includes an integrated circuit (IC) formed on a semiconductor substrate including a first spiral inductor and a second spiral inductor. The first spiral inductor is formed from a first metal layer over the substrate. The second spiral inductor is formed from a second metal layer. The second spiral inductor is offset from the first spiral inductor and includes a first portion overlapping the first spiral inductor. A first capacitor includes a first terminal coupled to receive a radio frequency (RF) signal and a second terminal coupled to a first terminal of the first spiral inductor, and second capacitor includes a first terminal coupled to a second terminal of the first spiral inductor.