Overlapping Piezoelectric Multiplexer Layout for Better Filter Isolation
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Solution Overview
Problem
When two filters in a multiplexer overlap, they interfere with each other, leading to deteriorated isolation characteristics, especially for high-frequency signals, and this issue is not effectively addressed by existing technologies.
Innovation Solution
A multiplexer design where a first substrate with a first filter and a second substrate with a second filter are arranged such that they overlap partially in a plan view, with series and parallel resonators including a piezoelectric film and electrodes, where the electrodes form a resonance region with the air gap, allowing for improved isolation characteristics by suppressing signal leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If two filters are arranged to overlap in plan view to reduce multiplexer size, then device area is reduced, but isolation characteristics deteriorate due to signal interference between filters
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the first and second filters. This ground electrode acts as a mediator to suppress electromagnetic coupling and signal leakage between the overlapping filters, thereby improving isolation characteristics while allowing the filters to maintain their overlapping compact arrangement
Solution Approach 2:
The multiplexer structure is segmented into multiple layers (first substrate with first filter, second substrate with second filter) with an air gap between them. This spatial segmentation allows the filters to overlap in plan view for compactness while separating them in the vertical direction to reduce interference, with the ground electrode providing additional isolation
2Area of stationary object
If wiring lines transmitting high-frequency signals are made to overlap to reduce area, then device area is reduced, but signal leakage increases and isolation characteristics worsen
Solution Approach 1:
The ground electrode serves as an intermediary shield between the wiring lines of the first and second filters. By positioning the ground electrode between the overlapping high-frequency signal paths, it intercepts and grounds stray electromagnetic fields, preventing signal leakage between the filters while allowing the wiring lines to overlap for compact design
Solution Approach 2:
The air gap between the first and second substrates, which could potentially allow signal leakage, is converted into a beneficial element. The air gap provides electrical isolation between the overlapping wiring lines, reducing parasitic capacitance and signal coupling, thereby improving isolation characteristics while maintaining the compact overlapping layout
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 design reduces the deterioration in isolation characteristics while maintaining a compact multiplexer size by strategically overlapping parts of the filters, enhancing signal suppression and frequency performance.
Implementation Method 1
each of the one or more second series resonators and the one or more second parallel resonators including a piezoelectric film
Implementation Method 2
forms a resonance region where the second electrode overlaps with the first electrode with at least a part of the piezoelectric film interposed between the first electrode and the second electrode in a plan view
Data Source
AI summary
A multiplexer includes: first and second substrates overlapping with each other with an air gap interposed therebetween; a first filter disposed on the first substrate and including first series resonators connected in series with a first path, and first parallel resonators; and a second filter disposed on the second substrate and including second series resonators connected in series with a second path, and second parallel resonators connected between the second path and a ground, each of the second series resonators and the second parallel resonators including a piezoelectric film, a first electrode interposed between the piezoelectric film and the second substrate, a second electrode interposed between the piezoelectric film and the air gap, and a resonance region, in at least one second parallel resonator, the first electrode being coupled to the second path, the second electrode being coupled to the ground, the resonance region overlapping with the first path.