Stacked RF Transformer Layout for Low Capacitance Coupling
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Solution Overview
Problem
Transformers in RF integrated circuits face challenges with non-scalable physical sizes, high capacitance, and performance degradation at high frequencies, leading to space consumption, increased circuit board space, and unwanted reflections, which are not optimized for impedance, coupling coefficient, and Q factor.
Innovation Solution
The design incorporates a primary winding and a secondary winding with fractional sections connected in parallel, located on the same layer, and uses a substrate with shield sections to minimize capacitance and maximize coupling, reducing impedance and resistance while maintaining high Q factor and resonance frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional integrated transformer designs are used, then the transformer can be integrated into the circuit, but the physical size remains large and consumes valuable circuit board space
Solution Approach 1:
The patent transitions from planar surface-mount transformer designs to a three-dimensional stacked configuration where windings are arranged in multiple layers vertically. This dimensional change allows the transformer to achieve higher coupling coefficients and better performance while reducing the footprint area on the circuit board, as the magnetic coupling occurs through vertical stacking rather than horizontal placement.
Solution Approach 2:
The patent implements a nested winding structure where secondary windings are positioned within the space occupied by primary windings, and shield sections are integrated between winding layers. This nesting approach maximizes the use of available space, increases the coupling coefficient by bringing windings closer together, and reduces the overall transformer volume without compromising performance.
2Reliability
If integrated transformer designs are used, then integration is achieved, but unwanted reflections occur from secondary winding to primary winding at high frequencies
Solution Approach 1:
The patent introduces shield sections as intermediary elements positioned between the primary and secondary windings. These shield sections, connected to ground, act as electromagnetic barriers that block unwanted signal reflections and interference between windings while allowing the transformer to maintain high coupling efficiency for the desired signal path.
Solution Approach 2:
The patent extracts and separates the shielding function from the winding structure by implementing dedicated shield sections that are distinct from the signal-carrying windings. This separation allows the shield to specifically target and eliminate harmful reflections without interfering with the primary transformation function, improving signal quality at high frequencies.
3Reliability
If traditional transformer designs are used, then impedance transformation is achieved, but capacitance is high and Q factor is poor at high frequencies
Solution Approach 1:
The patent divides the windings into multiple discrete sections or turns arranged in a stacked configuration, with shield sections positioned between them. This segmentation reduces the parasitic capacitance between adjacent winding sections by increasing their vertical separation distance, while the shield sections prevent capacitive coupling that would otherwise create unwanted reflections and degrade Q factor at high frequencies.
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
This configuration achieves a compact transformer size with improved performance by maintaining a high coupling coefficient, low resistance, and reduced reflections, suitable for high-frequency operations without degrading system performance.
Implementation Method 1
a primary winding and a secondary winding with fractional sections connected in parallel, located on the same layer
Implementation Method 2
uses a substrate with shield sections to minimize capacitance and maximize coupling
Data Source
AI summary
A transformer comprising a primary winding and a secondary winding. The primary winding has N2 number turns and having a first terminal and a second terminal. The secondary winding has having N1 fractional portions, which together form a full turn, are in close proximity to the primary winding to establish coupling between the primary winding and the N1 fractional coil portions, the transformer turn ratio from the primary winding to the secondary winding is N2:(N3/N1) where N2 is an integer equal to or greater than 1, N1 is an integer greater than or equal to 2, and N3 is an integer greater than or equal to 1. Also disclosed is a stacked integrated transformer having a primary winding and secondary winding of which one or both have a waterfall structure and a portion of which functions as a ground connected shield between the secondary winding and the primary winding.