Acoustic Wave Filter Layout With Gap Mass Loading for Ripple Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Acoustic wave devices using rotated Y-cut lithium niobate piezoelectric layers face challenges in suppressing unnecessary waves while maintaining low insertion loss, as these waves generate ripples between resonant and anti-resonant frequencies, leading to increased insertion loss.
Innovation Solution
Incorporating a mass addition film in the gap regions of the acoustic wave device, with specific thickness and width relationships, to reduce or prevent unnecessary waves and minimize insertion loss, by optimizing the design parameters such as the thickness of the mass addition film and the width of the gap region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bulk wave of thickness shear mode is excited in rotated Y-cut lithium niobate piezoelectric layer, then acoustic wave device functionality is achieved, but unnecessary waves are generated between resonant frequency and anti-resonant frequency
Solution Approach 1:
The patent extracts and removes the harmful unnecessary waves by introducing an acoustic reflection portion that selectively reflects unwanted acoustic energy while allowing the desired thickness shear mode bulk waves to propagate. This separation of useful and harmful acoustic modes resolves the contradiction.
Solution Approach 2:
The patent introduces an acoustic reflection portion as an intermediary element between the piezoelectric layer and the substrate. This intermediary structure mediates the acoustic wave propagation by reflecting unnecessary waves while maintaining the functionality of the desired mode.
2Object-generated harmful factors
If unnecessary waves are suppressed in rotated Y-cut lithium niobate acoustic wave device, then wave interference is reduced, but insertion loss increases
Solution Approach 1:
The patent applies local quality by positioning the acoustic reflection portion at specific locations (in gap regions between electrode fingers) where it can selectively affect only the unnecessary waves without interfering with the main signal path. This localized approach suppresses harmful waves while minimizing impact on insertion loss.
Solution Approach 2:
The patent addresses the contradiction by operating in another dimension - using vertical acoustic reflection through the substrate thickness rather than horizontal signal path modification. The acoustic reflection portion works in the depth dimension to reflect unnecessary waves back, while the signal propagation continues horizontally with minimal loss.
3Object-generated harmful factors
If mass addition film is added to gap regions, then unnecessary waves are reduced, but device structure becomes more complex
Solution Approach 1:
The patent merges the mass addition film with existing substrate structures or integrates it into the fabrication process flow, combining multiple functions into a single structural element. This reduces the perceived complexity by unifying the mass addition function with the substrate or existing layers.
Solution Approach 2:
The patent optimizes parameters such as the thickness and material composition of the mass addition film to achieve effective suppression of unnecessary waves with minimal structural modification. By carefully controlling film thickness and material properties, the solution achieves effectiveness while maintaining relatively simple device structure.
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 effectively reduces or prevents unnecessary waves and associated insertion loss, maintaining low admittance and insertion loss across the frequency band, as demonstrated by the admittance frequency characteristics and impedance frequency characteristics.
Implementation Method 1
A bulk wave of the thickness shear mode is excited by applying an AC voltage between the electrodes
Implementation Method 2
The support includes an acoustic reflection portion overlapping at least a portion of the IDT electrode in plan view
Implementation Method 3
A mass addition film is provided in at least a portion of at least one of the pair of gap regions
Data Source
AI summary
An acoustic wave device includes a support, a piezoelectric layer on the support, and an IDT electrode on the piezoelectric layer and includes a pair of busbars and electrode fingers. The support includes an acoustic reflection portion overlapping at least a portion of the IDT electrode. d/p is about 0.5 or less. Some of the electrode fingers are connected to one of the busbars, others of the electrode fingers are connected to another of the busbars. When viewed from a direction in which adjacent electrode fingers face each other, a region where the adjacent electrode fingers overlap each other is an intersection region. A region between the intersection region and the pair of busbars includes a pair of gap regions. A mass addition film is provided in at least a portion of at least one of the gap regions.