Duplexer Ground Pad Layout for Compact Signal Isolation
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Solution Overview
Problem
Modern portable phones with multiple bands and interfaces require a duplexer that is both downsized and maintains reliable isolation between signal pads, which existing technologies struggle to achieve due to signal leakage caused by reduced distances between pads.
Innovation Solution
A duplexer design featuring a substrate with insulation layers and interconnection layers, where the minimum distance between signal pads and inner ground pads is greater than the distance between signal pads and upper ground pads, and the thickness of the insulation layer between these layers is optimized to enhance signal coupling and reduce leakage, ensuring effective isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between signal pads is reduced to downsize the duplexer, then the device size is reduced, but signal leakage between pads increases and isolation characteristics deteriorate
Solution Approach 1:
The invention introduces a third vertical dimension by stacking interconnection layers above and below the substrate. Multiple ground pads are arranged in different vertical layers (upper interconnection layer, lower interconnection layer, and inner interconnection layer embedded in substrate), creating three-dimensional spatial separation between signal pads and ground pads. This vertical stacking allows reduced horizontal pad distances while maintaining isolation through layered grounding structures.
Solution Approach 2:
The invention embeds the inner interconnection layer containing ground pads within the substrate itself, nesting this layer inside the existing substrate structure. The inner ground pads are positioned within the substrate thickness, while upper and lower ground pads are positioned on opposite sides, creating a nested, multi-layer grounding configuration that provides comprehensive signal shielding in a compact volume.
2Reliability
If shield electrodes are added between patterns to improve isolation, then isolation characteristics improve, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The substrate serves multiple functions simultaneously: it provides mechanical support, electrical insulation, and houses embedded ground pads within its structure. The upper and lower interconnection layers also serve dual purposes as both signal transmission paths and grounding structures. This multi-functionality reduces the need for separate shield electrode structures, simplifying the overall device design while maintaining isolation performance.
3Reliability
If input and output terminals are arranged diagonally to prevent interference, then signal isolation improves, but device layout complexity and area increase
Solution Approach 1:
Instead of relying solely on diagonal arrangement in the horizontal plane, the invention uses vertical layering to achieve signal isolation. Ground pads are positioned in multiple vertical layers (upper, lower, and inner), allowing signal pads to be placed closer horizontally while maintaining isolation through the vertical stacking of grounding elements. This reduces the required device footprint compared to planar diagonal arrangements.
Data Source
AI summary
A duplexer includes a substrate including an insulation layer, an upper interconnection layer provided on an upper surface of the insulation layer, a lower interconnection layer provided on a lower surface of the insulation layer, and an inner interconnection layer provided in the insulation layer, the inner interconnection layer including an inner ground pad, at least one acoustic wave filter chip mounted on an upper surface of the substrate, signal pads provided on the upper interconnection layer and connected to signal electrodes of the at least one acoustic wave filter chip, and an upper ground pad that is provided in the upper interconnection layer so as to be located between the signal pads and is connected to a ground electrode of the at least one acoustic wave filter, wherein D1>D2 and D1>T1 where D1 is a minimum distance between the signal pads and the upper ground pad, D2 is a minimum distance between the signal pads and the inner ground pad, and T1 is a thickness of the insulation layer between the upper interconnection layer and the inner interconnection layer.