IDT and Multilayer Acoustic Wave Structure for Spurious Suppression
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Solution Overview
Problem
Existing acoustic wave devices face challenges in minimizing spurious components in specific frequency bands, which affect the filter characteristics and resonance frequencies, due to the limitations in the design of interdigital transducer (IDT) electrodes and multilayer films.
Innovation Solution
The acoustic wave device incorporates a piezoelectric layer with an IDT electrode and a multilayer film comprising alternating low and high acoustic impedance layers, with specific thickness and duty ratio relationships to optimize the propagation of acoustic waves, thereby reducing spurious components by controlling the normalized thickness and duty of the electrode fingers and impedance layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the IDT electrode and multilayer film are designed with conventional parameters, then the device structure is simple, but spurious components appear in specific frequency bands affecting filter characteristics
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between the normalized thickness of the piezoelectric layer (D1/p), the normalized thickness of the low acoustic impedance layer (D2/p), the normalized thickness of the high acoustic impedance layer (D3/p), and the duty ratio (d) of the IDT electrode. These parameter relationships are optimized to suppress spurious components in specific frequency bands while maintaining device functionality.
Solution Approach 2:
The patent uses composite materials by implementing a multilayer film structure consisting of alternating low acoustic impedance layers and high acoustic impedance layers. This composite structure is designed with specific thickness ratios to create acoustic impedance variations that suppress spurious components without requiring complex IDT electrode designs.
2Reliability
If the thickness and duty ratio of the piezoelectric layer and IDT electrode are optimized to reduce spurious components, then filter characteristics improve, but the design and manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges and relationships: D1/p × d should be in a predetermined range, D2/p × d should be in a predetermined range, and D3/p × d should be in a predetermined range. These parameter specifications provide clear manufacturing targets that balance performance optimization with manufacturability, reducing the need for excessive precision while achieving reliable filter characteristics.
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 spurious components in targeted frequency bands, enhancing the filter characteristics and resonance frequencies of the acoustic wave device, leading to improved performance in communication apparatuses like duplexers.
Implementation Method 1
A known acoustic wave device applies a voltage to an interdigital transducer (IDT) electrode on a piezoelectric body to generate an acoustic wave that propagates through the piezoelectric body
Implementation Method 2
The multilayer film is located on a lower surface side of the piezoelectric layer and includes at least one low acoustic impedance layer and at least one high acoustic impedance layer alternated with each other
Data Source
AI summary
An acoustic wave device includes a piezoelectric layer made of a piezoelectric crystal and an interdigital transducer (IDT) electrode on an upper surface of the piezoelectric layer. The IDT electrode includes multiple electrode fingers. A normalized thickness D1/p of the piezoelectric layer and a duty d of the IDT electrode have a relationship expressed by 0.166≤d×D1/p≤0.241 . . . (1), where p is a repetition interval between centers of the multiple electrode fingers, and D1 is a thickness of the piezoelectric layer.