SAW Resonator Dielectric Layer for Coupling Control in Filters
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Solution Overview
Problem
As communication technology advances from 2G to 5G and beyond, the increasing number of frequency bands requires more filters in communication devices, necessitating improved filter performance, miniaturization, and complexity, particularly in controlling the frequency-temperature coefficient and quality factor of surface acoustic wave filters.
Innovation Solution
A surface acoustic wave resonator with a dielectric layer between the interdigital transducer and the piezoelectric material layer, allowing for adjustable electromechanical coupling coefficients, and a manufacturing method involving etching to remove the dielectric layer in some resonators, enhancing passband and roll-off characteristics and transition band steepness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dielectric layer is added between the interdigital transducer and the piezoelectric material layer, then the electromechanical coupling coefficient can be adjusted and passband characteristics are improved, but the device structure becomes more complex and manufacturing steps increase
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the interdigital transducer and the piezoelectric material layer. This dielectric layer acts as a mediator that adjusts the electromechanical coupling coefficient by controlling the interaction strength between the transducer electrodes and the piezoelectric material, thereby improving passband characteristics while providing a systematic approach to managing the added structural complexity
Solution Approach 2:
The electromechanical coupling coefficient is adjusted by changing physical parameters of the dielectric layer, specifically its thickness and material properties. By varying these parameters, the coupling coefficient can be precisely controlled to optimize filter performance, including passband characteristics and transition band steepness, without requiring fundamental changes to the overall device architecture
2Reliability
If the dielectric layer is removed by etching in some resonators, then the transition band steepness is improved, but the manufacturing process becomes more difficult and requires additional etching steps
Solution Approach 1:
The dielectric layer is selectively removed only in specific resonators where enhanced transition band steepness is required, while retaining it in other resonators for different performance characteristics. This local differentiation allows optimization of specific filter poles for steep roll-off characteristics without affecting the entire filter structure, enabling targeted improvement of transition band performance
Solution Approach 2:
The filter is divided into multiple resonators with different configurations - some with the dielectric layer removed and others with it retained. This segmentation allows different resonators to serve different functions: those without the dielectric layer provide steep roll-off characteristics, while those with the layer provide other performance benefits, and all can be manufactured using the same base process followed by selective removal
3Adaptability or versatility
If more filters are required to support increasing frequency bands, then communication compatibility is improved, but the device size and complexity increase
Solution Approach 1:
The filter design uses a unified structure with standardized interdigital transducers and piezoelectric material layers that can be configured for different frequency bands by adjusting parameters such as dielectric layer thickness, resonator geometry, and electrode patterns. This universal base structure allows the same manufacturing process and component types to serve multiple frequency bands, reducing overall device complexity and size compared to having separate dedicated filters for each band
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 solution achieves higher performance filters with adjustable electromechanical coupling coefficients, improving passband and roll-off characteristics, and increasing the steepness of the transition band, while maintaining a simple and cost-effective manufacturing process.
Implementation Method 1
a piezoelectric material layer; an interdigital transducer located at a side of the piezoelectric material layer
Implementation Method 2
a dielectric layer, wherein the dielectric layer is located between the interdigital transducer and the piezoelectric material layer
Implementation Method 3
surface acoustic wave resonator
Data Source
AI summary
A surface acoustic wave resonator, a filter, a manufacturing method thereof and a communication device. The surface acoustic wave resonator includes a piezoelectric material layer, an interdigital transducer and a dielectric layer; the interdigital transducer is located at a side of the piezoelectric material layer, and the dielectric layer is located between the interdigital transducer and the piezoelectric material layer. Therefore, the surface acoustic wave resonator can reduce the electromechanical coupling coefficient of the surface acoustic wave resonator by arranging the dielectric layer between the interdigital transducer and the piezoelectric material layer. In addition, the surface acoustic wave resonator can adjust the electromechanical coupling coefficient of the surface acoustic wave resonator by controlling the thickness of the dielectric layer.