Multi-Layer Spiral Inductor for Low DC Resistance RF Choke
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional RF choke inductors fail to achieve both low direct current (DC) resistance and high radio frequency (RF) resistance, leading to instability and voltage degradation in radio frequency front end (RFFE) power amplifiers due to high quality factor, which causes oscillation and increased power consumption.
Innovation Solution
A multi-layer spiral inductive array is designed with a series connection of multiple-layer spiral inductors, each with a spiral pattern matching that of adjacent layers, reducing run length between turns to achieve low DC resistance and high RF resistance, thereby stabilizing the power amplifier and reducing RF swing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional printed inductors are used, then manufacturing is simple, but the quality factor is too high (greater than twenty) causing instability
Solution Approach 1:
The inductor is divided into multiple segments (first inductor and second inductor) connected in series, each with multiple layers. This segmentation allows independent optimization of each segment's characteristics to achieve the desired low Q factor while maintaining reliability
Solution Approach 2:
The patent transitions from planar 2D spiral patterns to 3D multi-layer structures with vertical stacking. Each layer is connected through vias, creating a three-dimensional configuration that reduces the quality factor by increasing the effective surface area and reducing parasitic effects
2Loss of energy
If conventional choke inductors are used, then DC resistance is reduced, but RF resistance is also reduced leading to high Q factor and oscillation
Solution Approach 1:
Different layers and segments of the inductor are designed with different geometric characteristics (varying trace widths, spacing, and spiral patterns) to optimize local properties. This allows the inductor to simultaneously achieve low DC resistance in some regions and high RF resistance in others, reducing the overall Q factor
Solution Approach 2:
The inductor uses composite construction with multiple conductive layers separated by dielectric materials, connected through via structures. This composite architecture creates different current paths for DC and RF signals, enabling low DC resistance while maintaining high RF resistance through skin effect and proximity effect
3Loss of energy
If multi-layer spiral inductive array is implemented, then DC resistance is reduced below 100 mOhm and Q factor below 15, but manufacturing complexity increases
Solution Approach 1:
The multi-layer spiral inductive array structure serves multiple functions simultaneously: it provides inductance, reduces DC resistance through parallel current paths, and reduces Q factor through increased surface area and distributed capacitance. This multi-functionality is achieved through a single integrated fabrication process, making the complex structure manufacturable
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 multi-layer spiral inductive array effectively reduces DC resistance below 100 mOhm and Q factor below 15, increasing the RF/DC resistance ratio, thereby stabilizing the power amplifier and reducing voltage degradation and oscillation.
Implementation Method 1
a first multi-layer spiral inductor with a second layer matching a spiral pattern of a first layer
Data Source
AI summary
A multi-layer spiral inductive array includes a first multi-layer spiral inductor with a second layer matching a spiral pattern of a first layer. The multi-layer spiral inductive array also includes a second multi-layer spiral inductor with a third layer matching a spiral pattern of a fourth layer. The second multi-layer spiral inductor is coupled in series with the first multi-layer spiral inductor.