Vertical Cross-Coupled Monolithic Transformers for High Coupling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional differential power amplifiers and low noise amplifiers face challenges in designing baluns and transformers with high coupling factors in standard CMOS processes, leading to increased insertion loss, noise figure, and decreased gain, which affects the efficiency and sensitivity of RF transceivers in mobile communication devices.
Innovation Solution
The development of ultra-high coupling factor monolithic transformers with innovative geometries and winding structures, including vertically and horizontally cross-coupled primary and secondary windings on multiple conductive layers, to achieve high mutual inductance and low insertion loss, enabling efficient signal conversion and impedance transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional edge coupled transformers are used in standard CMOS processes, then device integration is achieved, but coupling factor is limited to approximately 0.7 or lower
Solution Approach 1:
The patent transitions from planar edge-coupled transformer geometry to a vertically stacked three-dimensional configuration. The primary and secondary windings are positioned on different conductive layers separated by an insulating layer, creating vertical coupling through the insulating barrier. This dimensional transition enables significantly higher coupling factors (exceeding 0.95) while remaining compatible with standard CMOS fabrication processes, as the vertical stacking utilizes the layered structure inherent to CMOS technology.
2Manufacturing precision
If the number of inductive coils is increased to achieve high coupling factors, then coupling factor improves, but insertion loss increases
Solution Approach 1:
By moving from planar to vertical coupling, the patent achieves high coupling factors with fewer effective turns. The vertical proximity of windings on adjacent layers creates strong magnetic coupling without requiring additional coil windings, thereby avoiding the increased resistance and associated insertion losses that would result from adding more coils in a planar configuration.
Solution Approach 2:
The patent combines multiple functions into the transformer structure: impedance transformation, signal coupling, and differential mode generation are achieved simultaneously through the vertical coupled winding configuration. This integration eliminates the need for separate components and reduces overall signal path losses.
3Device complexity
If conventional transformers with coupling factor around 0.7 are used, then device complexity is reduced, but noise figure increases and gain decreases
Solution Approach 1:
The vertical stacked configuration provides superior magnetic coupling and reduced parasitic effects compared to planar designs. The close vertical proximity of windings minimizes loop area and associated parasitic inductance, while the insulating layer between layers reduces capacitive coupling to substrate, thereby lowering noise figure and improving gain without significantly increasing structural complexity.
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 proposed transformers achieve coupling factors greater than 0.9, minimizing noise figures and power amplifier errors, while maintaining high efficiency and reducing current consumption, thus enhancing the performance of RF front-end circuits in mobile devices.
Implementation Method 1
a first winding inductor (12) and a second winding inductor (14) that are cross-coupled horizontally and vertically and that define a mutual coupling inductance from surrounding directions
Data Source
AI summary
An ultra-high coupling factor transformer has a plurality of conductive layers, a primary winding inductor, and a secondary winding inductor. The primary winding inductor is defined by a plurality of turns and disposed on a first one of the plurality of conductive layers and extends to a second one of the plurality of conductive layers. The secondary winding inductor is defined by a plurality of turns and disposed on the first one of the plurality of conductive layers and extends to the second one of the plurality of conductive layers. The primary winding is vertically and horizontally cross coupled with the secondary winding inductor, and defines a mutual coupling inductance from surrounding directions.