Stacked Multiplexer Filter Layout for Compact Isolation Control
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Solution Overview
Problem
Existing multiplexers face challenges in achieving optimal isolation characteristics while minimizing size, as overlapping filters interfere with each other, leading to deteriorated isolation, and non-overlapping configurations result in increased size.
Innovation Solution
A multiplexer design where parts of the transmit filter and receive filter overlap in plan view, specifically configuring series and parallel resonators and pathways to minimize interference and reduce size while maintaining improved isolation, by overlapping parallel pathways with series pathways and parallel resonators, and ensuring small inductance between resonators and grounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If filters are arranged to overlap in plan view, then the size of the multiplexer is reduced, but the isolation characteristics deteriorate due to interference between filters
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional stacked configuration. Filters are arranged on different substrates (first substrate and second substrate) separated by an air gap, allowing them to overlap in plan view while being physically separated in the vertical dimension. This dimensional transition enables size reduction through overlapping projection areas while maintaining isolation through spatial separation in the third dimension.
Solution Approach 2:
The patent implements a nested structure where the projection area of filters on the first substrate overlaps with the projection area of filters on the second substrate. The filters are arranged in a nested configuration where one filter set is positioned within the projected boundary of the other, allowing compact integration while maintaining functional separation through the air gap and substrate structure.
2Reliability
If filters are arranged not to overlap in plan view, then the isolation characteristics are improved, but the size of the multiplexer increases
Solution Approach 1:
The patent resolves this contradiction by utilizing the vertical dimension (air gap between substrates) to accommodate overlapping filters. Instead of expanding the planar area to prevent overlap, the design allows overlap in the horizontal plane while maintaining isolation through vertical separation, thus minimizing the overall footprint while preserving isolation characteristics.
3Area of stationary object
If parallel pathways overlap with series pathways and parallel resonators, then the size is minimized, but interference between pathways increases
Solution Approach 1:
The patent applies dimensional separation by routing parallel pathways on one substrate and series pathways on another substrate, separated by an air gap. This allows the pathways to overlap in plan view for compactness while the vertical separation prevents electromagnetic interference, effectively using the third dimension to resolve the conflict between size minimization and interference reduction.
Data Source
AI summary
A multiplexer includes: a substrate having a surface; another substrate having another surface facing the surface across an air gap; a filter that is located on the surface, and includes first series resonators in a first series pathway from a common terminal to a terminal, and first parallel resonators in first parallel pathways; another filter that is located on the another surface, and includes second series resonators in a second series pathway from the common terminal to another terminal, and second parallel resonators in second parallel pathways, a second parallel resonator closest to the another terminal and a second series resonator closest to the another terminal not overlapping with the first series pathway, at least a part of the second parallel pathways overlapping with at least a part of first pathways between the first series pathway and the first parallel resonators, the first parallel resonators, and the first series pathway.