LiNbO3 Acoustic Wave Filter Layout for Spurious Wave Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing acoustic wave devices face challenges in miniaturization and bandwidth expansion, particularly in forming multiple band pass filters with different pass bands on the same piezoelectric substrate, leading to unwanted wave interference due to varying electrode finger pitches.
Innovation Solution
The acoustic wave device employs a piezoelectric substrate made of LiNbO3 with multiple IDT electrodes having different electrode finger pitches, where the film thickness and material density ratio of the main electrode layers are optimized, along with a dielectric film, to minimize unwanted waves by controlling the Euler angles and film thickness ratios, ensuring effective suppression of spurious noise across varying electrode lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple IDT electrodes with different electrode finger pitches are provided on the same piezoelectric substrate to expand bandwidth and enable multi-band communication, then the device can simultaneously perform communication in a large number of bands and widen bandwidth, but unwanted waves and spurious noise are generated due to the different pitches
Solution Approach 1:
A dielectric film is selectively provided only on specific IDT electrodes (those generating unwanted waves) rather than uniformly across all electrodes. The dielectric film covers the IDT electrode with a different electrode finger pitch from the reference IDT electrode, creating local differentiation to suppress unwanted waves while maintaining the different pitch configurations needed for multi-band operation.
Solution Approach 2:
A dielectric film is introduced as an intermediary element between the piezoelectric substrate and the problematic IDT electrode. This dielectric film acts as a mediator to suppress the generation of unwanted waves by the IDT electrode with different pitch, without requiring changes to the electrode pitch itself or the fundamental multi-band architecture.
2Volume of moving object
If multiple IDT electrodes with different electrode finger pitches are provided on the same piezoelectric substrate to meet miniaturization requirements, then the device size can be reduced, but unwanted waves interfere with signal quality
Solution Approach 1:
The dielectric film is selectively applied only to specific IDT electrodes that generate unwanted waves, creating local differentiation. This allows the compact multi-electrode layout to be maintained for miniaturization while locally suppressing unwanted wave generation at problem areas.
Solution Approach 2:
The dielectric film converts the harmful unwanted waves generated by IDT electrodes with different pitches into a controllable parameter. By strategically placing the dielectric film, the unwanted wave energy is suppressed and converted into useful signal transmission, turning the interference problem into a solved characteristic.
3Speed
If IDT electrodes with different electrode finger pitches are used to increase communication speed and data transmission rate, then carrier aggregation and multi-band communication can be achieved, but spurious noise is generated that affects signal integrity
Solution Approach 1:
The dielectric film serves as an intermediary that suppresses spurious noise generated by IDT electrodes operating at different pitches. This allows the high-speed multi-band communication functionality to be maintained while the dielectric film mediates the noise generation process.
Solution Approach 2:
The dielectric film changes the physical parameters (film thickness, material properties) of specific IDT electrode regions to suppress spurious noise. By adjusting these parameters, the noise generation is controlled while maintaining the different pitch configurations necessary for high-speed data communication.
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 effectively reduces or prevents unwanted waves, even when multiple IDT electrodes with different finger pitches are used on the same substrate, enhancing the device's frequency-temperature characteristics and bandwidth capabilities.
Implementation Method 1
an acoustic wave device using a Rayleigh wave... a piezoelectric substrate made of LiNbO3... IDT electrodes provided on the piezoelectric substrate
Implementation Method 2
a dielectric film provided on the piezoelectric substrate to cover the plurality of IDT electrodes... effectively reduce or prevent unwanted waves
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate made of LiNbO3, and a dielectric film provided on the piezoelectric substrate to cover first and second IDT electrodes on the piezoelectric substrate. The first and second IDT electrodes include main electrode layers. When wave lengths determined by electrode finger pitches of the first and second IDT electrodes are λ1 and λ2, respectively, the average value thereof is λ0, λ1/λ0=1+X, and λ2/λ0=1−X, a relationship of 0.05≤X≤0.65 is satisfied. The wavelength λ1 is the longest, and the wavelength λ2 is the shortest. In Euler angles (φ, θ, ψ) of the piezoelectric substrate, φ is 0°±5°, ψ is 0°±10°, and θ satisfies Expression 1, wherein a relationship of B1<T×r≤0.10λ0 and B2<T×r≤0.10λ0 are satisfied.