Rolled-Up Transformer Structure for RFIC Footprint Reduction
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Solution Overview
Problem
On-chip transformers for radiofrequency integrated circuits (RFICs) face challenges in reducing footprint while maintaining desirable coupling coefficients, which is essential for impedance matching, signal coupling, and phase splitting.
Innovation Solution
A rolled-up on-chip transformer structure is developed, comprising a multilayer sheet with conductive pattern layers that self-roll into a tubular configuration, where primary and secondary conductive strips wrap around a longitudinal axis, reducing the footprint and enhancing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional planar transformer structures are used, then the device is easy to manufacture, but the footprint area is large
Solution Approach 1:
The patent transitions from a two-dimensional planar transformer structure to a three-dimensional rolled-up cylindrical structure. The primary and secondary windings are formed by rolling a multilayer sheet containing conductive patterns, creating a vertical stacking configuration that achieves high coupling coefficients while minimizing footprint area on the chip surface.
Solution Approach 2:
The rolled-up structure nests the primary windings and secondary windings in a concentric cylindrical arrangement around a central axis. This nested configuration allows the windings to be closely coupled in three-dimensional space, achieving high magnetic coupling coefficients while occupying minimal planar area.
2Reliability
If the number of turns is increased to improve coupling coefficient, then the coupling performance is improved, but the footprint area increases
Solution Approach 1:
By rolling the multilayer sheet into a cylindrical structure, the patent enables multiple turns to be stacked vertically along the longitudinal axis rather than expanding horizontally. This three-dimensional arrangement allows high coupling coefficients to be achieved with compact footprint by utilizing the vertical dimension for winding turns.
Solution Approach 2:
The patent employs a composite multilayer sheet structure comprising alternating layers of conductive materials and dielectric materials. This composite construction enables the formation of multiple primary and secondary windings with precise geometric control, achieving high coupling coefficients while maintaining compact dimensions through optimized material stacking.
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 rolled-up transformer structure achieves a significant reduction in on-chip footprint and improves performance by maintaining a high coupling coefficient, achieving a dramatic reduction in footprint and substrate loss, with a wide working frequency band and low leakage inductance.
Implementation Method 1
A varying current in the primary winding creates a varying magnetic flux in the transformer's air core, and thus a varying magnetic flux through the secondary winding. This varying magnetic flux induces a varying electromotive force (EMF), or voltage in the secondary winding. This effect is called inductive coupling.
Implementation Method 2
The strained layer is held on the substrate by the sacrificial layer. Removal of the sacrificial layer from the substrate is initiated, thereby releasing an end of the strained layer, and removal of the sacrificial layer is continued, thereby allowing the strained layer to move away from the substrate and roll up to relieve strain in the strained layer.
Data Source
AI summary
A rolled-up transformer structure comprises a multilayer sheet having a rolled configuration comprising multiple turns about a longitudinal axis. The multilayer sheet comprises more than one conductive pattern layer on a strain-relieved layer, including a first conductive film and a second conductive film separated from the first conductive film in a thickness direction. The first conductive film comprises an even number of primary conductive strips, where each primary conductive strip has a length extending in the rolling direction, and the second conductive film comprises an even number of secondary conductive strips, where each secondary conductive strip has a length extending in the rolling direction. In the rolled configuration, turns of the primary conductive strips and turns of the secondary conductive strips wrap around the longitudinal axis. The primary conductive strips serve as a primary winding and the secondary conductive strips serve as a secondary winding of the rolled-up transformer structure.