Multi-Lobe On-Chip Inductor Layout for Mutual Coupling Isolation
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Solution Overview
Problem
The mutual coupling between neighboring on-chip inductors due to magnetic flux interlinkage leads to undesirable effects such as strong S21 (S-parameters) and the generation of unwanted spurs, which can result in elevated clock jitter or VCO pulling, and functionality failures.
Innovation Solution
A multi-lobe inductor structure is proposed, where the inductor is surrounded by a ground ring and a broken ring. The broken ring is electrically coupled with the ground ring and positioned around the perimeter of the substrate, creating a magnetic barrier that effectively terminates all flux propagation and cancels electromagnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wide spacing between inductors is used to mitigate coupling effects, then mutual coupling is reduced, but silicon area efficiency deteriorates
Solution Approach 1:
A ground ring is introduced as an intermediary structure between neighboring inductors. The ground ring acts as a magnetic flux termination path, providing a low-impedance return path for magnetic flux and preventing it from coupling to adjacent inductors. This allows inductors to be placed closer together while maintaining isolation through the ground ring mediator.
Solution Approach 2:
The ground ring is segmented into multiple sections rather than being continuous. These segments are positioned strategically around the inductor to provide effective flux termination while minimizing the area occupied by the isolation structure. The segmentation allows the ground ring to function effectively with reduced area overhead.
2Adaptability or versatility
If multiple VCOs are used to cover diverse frequency bands, then frequency versatility is improved, but mutual coupling between inductors increases
Solution Approach 1:
The ground ring serves as a mediator between multiple VCO inductors, providing a common reference potential and flux termination path. This allows multiple VCOs operating at different frequency bands to coexist on the same chip without excessive mutual coupling, as the ground ring captures and terminates magnetic flux before it can couple to neighboring inductors.
3Object-affected harmful factors
If inductors are positioned orthogonally to minimize mutual coupling, then coupling effects are reduced, but device complexity increases
Solution Approach 1:
The ground ring creates an equipotential reference around the inductor, establishing a uniform magnetic flux termination boundary. This simplifies the layout design as inductors can be placed in standard orientations without requiring complex orthogonal positioning, since the ground ring provides isotropic flux termination in all directions around the inductor.
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 solution significantly mitigates flux leakage and mutual coupling between adjacent inductors, enhancing the quality factor (Q) and isolation, while maintaining silicon area efficiency and avoiding increased PCB manufacturing costs.
Implementation Method 1
The broken ring is electrically coupled with the ground ring and positioned around a perimeter of the substrate such that the inductor is surrounded by the ground ring and the broken ring... creating a magnetic barrier that effectively terminates all flux propagation
Implementation Method 2
the side lobes configured to generate an electromagnetic flux in opposite direction of an electromagnetic flux generated by the main coil
Data Source
AI summary
The present invention discloses an electronic device having a multi-lobe differential inductor with two terminals fabricated on a P-substrate, The electronic device comprises a broken ring electrically coupled with the ground ring (M5), positioned around a perimeter of the substrate such that the inductor is surrounded by the ground ring and the broken ring. The broken ring defines a plurality of parallelly arranged structures; each structure comprises a plurality of metal segments (M1-M4, M6-M10) parallel to each other and electrically connected to and perpendicular to the ground ring.