Acoustic Wave Filter Layout With Shared Bus Bar for Smaller Size
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Solution Overview
Problem
Acoustic wave devices used in wireless communication devices face challenges in power durability and size reduction, as serial division increases device size and dummy electrode fingers can further enlarge the device while compromising surface acoustic wave confinement.
Innovation Solution
The acoustic wave device incorporates a piezoelectric substrate with a first and second IDT connected in series, sharing a common bus bar that is no more than two times the wavelength of the acoustic wave, and lacks dummy electrode fingers facing the bus bars, allowing for improved power durability and reduced size without significant surface acoustic wave loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single acoustic wave device is serially divided to improve power durability, then power durability is improved, but the device increases in size
Solution Approach 1:
The patent merges the bus bar functions of the first and second IDTs by making them share a common bus bar. This consolidation reduces the overall number of bus bars from four to three, thereby reducing device size while maintaining the serial connection configuration that improves power durability.
Solution Approach 2:
The common bus bar serves dual functions: it acts as the second bus bar of the first IDT and simultaneously as the first bus bar of the second IDT. This multi-functionality reduces the total component count and device area while preserving the power durability benefits of serial division.
2Stability of the object's composition
If dummy electrode fingers are provided between electrode fingers to improve surface acoustic wave confinement, then wave confinement is improved, but the device increases in size
Solution Approach 1:
The patent extracts (removes) dummy electrode fingers from the regions facing the bus bars. By eliminating these unnecessary dummy fingers that would increase device size, the invention achieves wave confinement through alternative means while reducing the overall device area.
Solution Approach 2:
The patent applies different electrode finger configurations to different regions: dummy electrode fingers are provided in regions where they are needed for wave confinement, but deliberately omitted in regions facing the bus bars where they would be redundant and increase device size. This localized differentiation optimizes both wave confinement and size reduction.
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 configuration enhances power durability and reduces device size while maintaining the confinement of surface acoustic waves, with minimal loss when waves propagate between the first and second IDTs, and improves the frequency and pass characteristics of filters and duplexers.
Implementation Method 1
an acoustic wave device including: a piezoelectric substrate; a first IDT located on the piezoelectric substrate and including electrode fingers and two bus bars
Implementation Method 2
the common bus bar has a width that is not more than two times a wavelength of an acoustic wave propagating through the first IDT and the second IDT
Data Source
AI summary
Acoustic wave device includes: a piezoelectric substrate; a first IDT located on the piezoelectric substrate; and a second IDT located on the piezoelectric substrate and connected in series to the first IDT, wherein the first IDT and the second IDT share a single common bus bar as a first bus bar of two bus bars of the first IDT and a first bus bar of two bus bars of the second IDT, and the common bus bar has a width not more than two times a wavelength of an acoustic wave propagating through the first and second IDTs, the common bus bar connects to no dummy electrode finger facing a tip of an electrode finger connected to a second bus bar of the two bus bars of the first IDT and the second IDT across a gap.